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Sample records for east antarctica evidence

  1. Morphological evidence and direct estimates of rapid melting beneath Totten Glacier Ice Shelf, East Antarctica

    Science.gov (United States)

    Greenbaum, Jamin; Schroeder, Dustin; Grima, Cyril; Habbal, Feras; Dow, Christine; Roberts, Jason; Gwyther, David; van Ommen, Tas; Siegert, Martin; Blankenship, Donald

    2017-04-01

    Totten Glacier drains at least 3.5 meters of eustatic sea level potential from marine-based ice in the Aurora Subglacial Basin (ASB) in East Antarctica, more than the combined total of all glaciers in West Antarctica. Totten Glacier has been the most rapidly thinning glacier in East Antarctica since satellite altimetry time series began and the nature of the thinning suggests that it is driven by enhanced basal melting due to ocean processes. While grounded ice thinning rates have been steady, recent work has shown that Totten's floating ice shelf may not have the same thinning behavior; as a result, it is critical to observe ice shelf and cavity boundary conditions and basal processes to understand this apparent discrepancy. Warm Modified Circumpolar Deep Water (MCDW), which has been linked to glacier retreat in West Antarctica, has been observed in summer and winter on the nearby Sabrina Coast continental shelf and deep depressions in the seafloor provide access for MCDW to reach the ice shelf cavity. Given its northern latitude, numerical ice sheet modeling indicates that Totten Glacier may be prone to retreat caused by hydrofracture in a warming climate, so it is important to understand how intruding MCDW is affecting thinning of Totten Glacier's ice shelf. Here we use post-processed, focused airborne radar observations of the Totten Glacier Ice Shelf to delineate multi-km wide basal channels and flat basal terraces associated with high basal reflectivity and specularity (flatness) anomalies and correspondingly large ice surface depressions that indicate active basal melting. Using a simple temperature-attenuation model, and basal roughness corrections, we present basal melt rates associated with the radar reflection and specularity anomalies and compare them to those derived from numerical ocean circulation modeling and an ice flow divergence calculation. Sub-ice shelf ocean circulation modeling and under-ice robotic observations of Pine Island Glacier Ice

  2. Tectonic Models for the Lake Vostok Region: Evidence for a major Suture Zone within East Antarctica

    Science.gov (United States)

    Studinger, M.; Karner, G. D.; Bell, R. E.; Levin, V.; Raymond, C. A.; Tikku, A. A.; Lerner-Lam, A.

    2001-12-01

    East Antarctica, roughly the size of the conterminous United States, remains the largest unexplored part of the Earth's crust. Existing tectonic models are mostly derived from the geological record preserved in the sparse rock outcrops along the perimeter of the continent. New aerogeophysical data, acquired during the 2000/01 field season over Lake Vostok represents the first comprehensive geophysical data in this region. A range of tectonic models has been tested in order to match the observed and predicted aerogeophysical data. A simple boundary between two different crustal blocks with different thickness and density, isostatically balanced, fails to match the long wavelength signature and amplitude of the observed gravity. Similarly, a simple extensional model does not fit the observed long wavelength trends in the gravity. In order to match the characteristic anomalies along the profiles we constructed a thrust model involving a former continental margin on one side. This model explains the typical asymmetric, dipolar gravity signature of suture zones. A small extensional basin beneath Lake Vostok,is needed to match the short wavelength gravity low, modulating the main trend. This small basin was likely created during a later phase of weak extensional reactivation. Modeling of composite receiver functions supports the idea of two different types of crust on top of each other beneath the recording site. Our newly discovered boundary in East Antarctica, its possible extension towards the Queen Mary Coast and its relation to major structures in Australia like the Albany-Fraser belt will be discussed in our presentation.

  3. Monitoring geodynamic activity in the Victoria Land, East Antarctica: Evidence from GNSS measurements

    Science.gov (United States)

    Zanutta, A.; Negusini, M.; Vittuari, L.; Cianfarra, P.; Salvini, F.; Mancini, F.; Sterzai, P.; Dubbini, M.; Galeandro, A.; Capra, A.

    2017-10-01

    GNSS networks in Antarctica are a fundamental tool to define actual crustal displacements due to geological and geophysical processes and to constrain the glacial isostatic models (GIA). A large network devoted to the detection and monitoring of crustal deformations in the Northern Victoria Land (Victoria Land Network for DEFormation control - VLNDEF), was monumented during the 1999-2000 and 2000-2001 field campaigns, as part of Italian National Program for Antarctic Research and surveyed periodically during the Southern summer seasons. In this paper, GPS observations of VLNDEF collected over a more than 15-year span, together with various selected POLENET sites and more than 70 IGS stations, were processed with Bernese Software, using a classical double difference approach. A solution was obtained combining NEQs by means of ADDNEQ2/FODITS tools embedded in Bernese Software. All the Antarctic sites were kept free and a subset of 50 IGS stations were used to frame VLNDEF into ITRF2008. New evidence provided by analysis of GPS time series for the VLNDEF network is presented; also displacements along the vertical component are compared with the recently published GIA models. The absolute velocities indicate an overall displacement of the northern Victoria Land region along the south-east direction (Ve = 10.6 mm/yr, Vn = -11.5 mm/yr) and an average uplift rate of Vu = 0.5 mm/yr. Two GIA models have been analyzed: ICE-6G_C-VM5a proposed by Argus et al. (2014), Peltier et al. (2015) and W12A_v1 by Whitehouse et al. (2012a,b). Up rates, predicted over the VLNDEF sites by the mentioned GIA models, have been extracted and compared with those observed. A preliminary comparison with GPS-derived vertical rates shows that the Victoria Land ICE-6G_C-VM5 and W12A_v1 GIA models predict overestimated uplift rates of 0.7 and 0.9 mm/yr weighted mean residuals respectively. The mean horizontal relative motions within the Victoria Land (VL) area are in most cases negligible, while only

  4. High-velocity lid of East Antarctica: Evidence of a depleted continental lithosphere

    Science.gov (United States)

    Kuge, Keiko; Fukao, Yoshio

    2005-06-01

    In broadband seismograms from shallow earthquakes occurring south of New Zealand recorded at the South Pole, we found significant arrivals 40-70 s after the first SH arrivals at distances of 29°-35° and 20-50 s after the first P arrivals at distances of 28°-35°. These waves traversing beneath East Antarctica can be modeled by slightly modifying one-dimensional P and S wave velocity structures of the Canadian shield. In the obtained velocity models, a velocity reduction below the lithosphere forms a deep low-velocity zone. S waves turning below the low-velocity zone explain the SH waveforms observed at 29°-55°. The observed P waveforms, however, suggest that a corresponding reduction in P velocity is smaller. These P and S wave velocity variations are likely to be a manifestation of a depleted continental lithosphere (high concentrations of olivine and magnesium number (Mg # = 100Mg/(Mg + Fe)). For a lithospheric composition more depleted than that of the underlying mantle, the temperature profile estimated from our velocity models is smooth from the lithosphere to the underlying mantle. Lithospheric depletion can also explain that the velocity anomaly in the lithosphere is larger for S than for P waves. Were the composition to be assumed uniform throughout the upper mantle, a large temperature gradient would be required at the bottom of the lithosphere, implying a heat sink which is unlikely to be sustainable. Thus a difference in composition between the lithosphere and underlying mantle leads to a reasonable estimate of temperature profile that is consistent with the observed seismic waveforms.

  5. The seafloor geomorphology of the Windmill Islands, Wilkes Land, East Antarctica: Evidence of Law Dome ice margin dynamics

    Science.gov (United States)

    Carson, C. J.; Post, A. L.; Smith, J.; Walker, G.; Waring, P.; Bartley, R.; Raymond, B.

    2017-09-01

    A high-resolution multibeam sonar dataset covering an area of ca. 33 km2 was collected in the vicinity of the Windmill Islands (67°S, 110°E), Wilkes Land, East Antarctica. The new data permit visualisation of the nearshore seafloor morphology in unprecedented detail, providing invaluable insight into the ice-sheet history of the region. A range of geomorphic features are evident, including prominent parallel northwest-trending linear fault sets affecting Mesoproterozoic metamorphic basement, which appear to control the regional coastal physiography. The fault systems probably formed during fragmentation of eastern Gondwana during the Mesozoic. Networks of sub-glacial meltwater channels, preserved on bedrock platforms and ridges, indicate grounding of a thick ice sheet over the continental shelf during previous glaciations. West-trending subtle glacial lineations and streamlined landforms record evidence of the westward expansion of the grounded Law Dome ice sheet margin, probably during the late Pleistocene. The direction of these features coincides with glacial striae on onshore crystalline bedrock outcrops. Perhaps the most striking glacial geomorphological features are sets of arcuate ridges confined mostly within glacially excavated U-shaped troughs formed by erosion of the northwest-trending bedrock fault sets. These ridge sets are interpreted as push moraines or grounding zone features, formed during episodic retreat of highly channelised, topographically-controlled ice-streams following ice surging of the Law Dome margin. This event was possibly triggered in response to local environmental forcing during the mid-late Holocene. Minor post-glacial marine sedimentation is preserved in several small (≤ 1 km2) isolated basins with shallow seaward sills.

  6. Evidence of Meso-Archaean subduction from the Torckler-Tango Layered Complex, Rauer Group, Prydz bay, East Antarctica

    Science.gov (United States)

    McCallum, C. A.; Harley, S. L.

    2010-12-01

    The Archaean Torckler Tango Layered complex (TTLC) of the Rauer Group, East Antarctica, consists of a series of elongate mega-boudins that can be traced over a strike length of 7 km, enclosed within and intruded by c. 2.8 Ga homogeneous tonalitic orthogneisses. Despite later granulite facies metamorphism (860-900°C, 0.7 GPa) original igneous structures and layering features of the TTLC are very well preserved. Graded and cross stratified layering is evident, as are load-cast structures and geopetal structures. Isotopic and LILE signatures indicate that crustal contamination has been negligible and that metamorphic disturbances have been minor. As a result, the whole rock chemistry of the TTLC is considered to reflect its igneous protoliths. This whole rock geochemistry is distinctive, with high MgO (av. 15.8 wt%), high Mg# (av. 79.1) low TiO2 (av.< 0.33 wt%), and high SiO2 (av. 52.5 wt%). The TTLC can be subdivided into two geochemical groupings based upon Al2O3 and Cr abundances, which provide clear evidence for the crystal fractionation and accumulation processes active within the complex. Trace-element and REE element ratios show coherent trends. Based on its systematic major element (Al2O3/TiO2 ~40), trace element ratios Ti/Zr vs. Zr (Ti/Zr ~34-59 at Zr ~15-40 ppm), and negative HSFE anomalies, the TTLC is similar in geochemistry to both modern, neo-Proterozoic and Archaean boninitic rocks. Magmatic zircons define an intrusive age for the TTLC of ca. 3280 ± 22 Ma. HSFE ratios, and whole rock Nd isotope ratios recalculated back to this age, are consistent with a juvenile depleted source for the primary magma. The TTLC is therefore interpreted as the intrusive equivalent of a boninite, produced through the shallow melting of refractory mantle and supportive of the operation of subduction-like processes in the early-mid Archaean.

  7. Age and isotopic marks of K-rich Manning Massif trachybasalts: an evidence for Lambert-Amery rift-system initiation (East Antarctica)

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    Leitchenkov, German; Belyatsky, Boris; Lepekhina, Elena; Antonov, Anton; Krymsky, Robert; Andronikov, Alex; Sergeev, Sergey

    2017-04-01

    Volcanic rocks from the Manning Massif, which is situated in the western flank of the Paleozoic-Late Mesozoic Lambert Rift (East Antarctica), belong to a rare type of alkaline magmatism within the Precambrian East Antarctic Craton. K-rich olivine trachybasalts compose some flows resting upon a surface of Precambrian granulite terrain, each flow of 2.5-7 m in thickness and total section not less than 30 m. Each flow sequence comprises of glassy chilled base with vitroporphyritic texture, fine-plated vesicular basalt with interstitial texture, massive fine-grained basalt with porphyritic microlitic texture, amigdaloidal aphanitic basalt with poikilophytic texture, and vesicular mandelstone of slag crust with vitroporphyritic texture [Andronikov et al., 1998]. Rb-Sr and K-Ar isotopic age of this eruption was estimated as 40-50 Ma and the main reason for this Cenozoic continental volcanism was supposed the post-rift tectonic activity [Andronikov et al., 1998]. But the isotopic characteristics of these trachybasalts are very similar to those obtained for the part of spinel lherzolite and spinel-garnet lherzolite xenoliths from the Mesozoic alkaline picrite of the adjacent Jetty Peninsula region. That could be evidence of the trachybasalt mantle source in long-lived enriched upper mantle beneath the region, either under the lowermost levels of spinel lherzolite facies or on the highest levels of garnet lherzolite facies conditions. To reveal tectonic position of these enigmatic volcanics, we have studied 16 samples from different parts of basaltic flows for U-Pb geochronology and Pb-Sr-Nd-Os isotopic characteristics. U-Pb SIMS SHRIMP-II analysis was performed for 68 apatite grains from 5 samples. All obtained data-points are approximated by discordia line (MSWD=1.6) on Tera-Wasserburg diagram, corresponding to the age of 346±46 Ma. Common Pb isotope composition of these apatites differs from the model by increased 206Pb/204Pb (19.8) and 207Pb/204Pb (18.3) that means the

  8. Bed Topography and Evidence of Possible new Subglacial Lakes Over the Region Vostok-Dome Concordia (East Antarctica) Inferred by Airborne Radar Survey

    Science.gov (United States)

    Tabacco, I. E.; Forieri, A.; Bianchi, C.; Zirizzotti, A.; Passerini, A.; Rémy, F.

    2002-05-01

    During the 1999 and 2001 Italian Antarctic Expeditions, extensive airborne radar surveys were carried out over the region Vostok-Dome C (about 6000 km of radar tracks were acquired). The radar data allowed to determine the ice thickness and the bedrock topography over the entire area; in addition, the analysis of the shape and the amplitude of the bottom reflections, permitted to identify 30 radar tracks as sub glacial "lake" mirrors. On account of the bed topography some important features were detected: (i) a deep trench into the Aurora Subglacial Basin, oriented approximately N-S at about 119o E, (that could be considered as the extension of the Peacock Subglacial Trenc) that divides the region into two sub-areas with different morphological aspect. The first one, located between the eastern ridge of Lake Vostok and the trench, is characterized by a bedrock that dips gently with a near constant gradient of about 4.2 m/km, without relevant local irregularities. The second one, located North-East of the trench towards Dome C, is characterized by a bedrock with a steep rise up and a complex morphology typical of mountain massif; (ii) a second trench, East of Dome C summit, N-S oriented at about 124.5o E. This trench seems to divide the Dome C massif by the Belgica Subglacial Highlands. Considering that the Dome C massif is surrounded North and North-East by the depressions of the Vincennes Subglacial Basin and of the Adventure Trench we could suggest that the Dome C mountains are morphologically like an isolated massif. The comparison of the surface topography, inferred by ERS-1 data, with the bed morphology, allowed to link and to correlate the surface slope anomalies with the main bed features. The "lake" radar tracks were analysed and compared with the surface slope anomalies and with the bed morphology. All the tracks are located over narrow and local anomalies of the bedrock like trough or catchment basin; 26 of the radar tracks lie over close and evident

  9. Petrology and phase equilibrium modeling of sapphirine + quartz assemblage from the Napier Complex, East Antarctica: Diagnostic evidence for Neoarchean ultrahigh-temperature metamorphism

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    Hisako Shimizu

    2013-11-01

    Full Text Available A synthesis of the petrological characters of granulite facies rocks that contain equilibrium sapphirine + quartz assemblage from two localities (Tonagh Island (TI and Priestley Peak (PP in the Napier Complex, East Antarctica, provides unequivocal evidence for extreme crustal metamorphism possibly associated with the collisional orogeny during Neoarchean. The reaction microstructures associated with sapphirine + quartz vary among the samples, probably suggesting different tectonic conditions during the metamorphic evolution. Sapphirine and quartz in TI sample were probably in equilibrium at the peak stage, but now separated by corona of Grt + Sil + Opx suggesting near isobaric cooling after the peak metamorphism, whereas the Spr + Qtz + Sil + Crd + Spl assemblage replaces garnet in PP sample suggesting post-peak decompression. The application of mineral equilibrium modeling in NCKFMASHTO system demonstrated that Spr + Qtz stability is lowered down to 930 °C due to small Fe3+ contents in the rocks (mole Fe2O3/(FeO + Fe2O3 = 0.02. The TI sample yields a peak p-T range of 950–1100 °C and 7.5–11 kbar, followed by cooling toward a retrograde stage of 800–950 °C and 8–10 kbar, possibly along a counterclockwise p-T path. In contrast, the peak condition of the PP sample shows 1000–1050 °C and >12 kbar, which was followed by the formation of Spr + Qtz corona around garnet at 930–970 °C and 6.7–7.7 kbar, suggesting decompression possibly along a clockwise p-T trajectory. Such contrasting p-T paths are consistent with a recent model on the structural framework of the Napier Complex that correlates the two areas to different crustal blocks. The different p-T paths obtained from the two localities might reflect the difference in the tectonic framework of these rocks within a complex Neoarchean subduction/collision belt.

  10. Planktonic cephalopods collected off East Antarctica during the `BROKE' survey

    Science.gov (United States)

    Jackson, George D.; Finn, Julian; Nicol, Stephen

    2002-06-01

    The composition and distribution of squid captured between January and March during the 1996 baseline research on oceanography, krill and the environment survey off East Antarctica (80-150°E) was investigated. A total of 195 individuals were captured. The species collected were Galiteuthis glacialis, Mesonychoteuthis hamiltoni, Histioteuthis atlantica, H. eltaninae, Alluroteuthis antarcticus, Batoteuthis skolops and Pholidoteuthis boschmai. Concentrations of squid were low, ranging from 4.4 to 174.7 individuals 100,000 -3. The majority of squid captured were G. glacialis (174 individuals, 89.2% of all squid captured), and most of these ( n=171) were small paralarvae oceanic waters of the ACC to the east, where salps dominated.

  11. New Views of East Antarctica- from Columbia to Gondwana

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    Ferraccioli, F.; Forsberg, R.; Aitken, A.; Young, D. A.; Blankenship, D. D.; Bell, R. E.; Finn, C.; Martos, Y. M.; Armadillo, E.; Jacobs, J.; Ebbing, J.; Eagles, G.; Jokat, W.; Jordan, T. A.; Ruppel, A.; Läufer, A.; Dalziel, I. W. D.

    2015-12-01

    East Antarctica is a keystone in the Gondwana, Rodinia and the Columbia supercontinents. Recent aerogeophysical research, augmented by satellite magnetic, gravity and seismological data is unveiling the crustal architecture of the continent. This is helping comprehend the impact of supercontinental processes such as subduction, accretion, rifting and intraplate tectonics on its evolution. A mosaic of Precambrian basement provinces is apparent in interior East Antarctica (Ferraccioli et al., 2011, Nature). A major suture separates the Archean-Neoproterozoic Ruker Province from an inferred Grenvillian-age orogenic Gamburtsev Province with remarkably thick crust (up to 60 km thick) and thick lithosphere (over 200 km thick). The age of the suturing and its linkages with supercontinental assembly is debated with both Rodinia and Gondwana candidates being proposed. Further east, magnetic highs delineate a Paleo to Mesoproterozoic Nimrod-South Pole igneous province (Goodge and Finn, 2010 JGR) that flanks a composite Mawson Continent- including the Gawler Craton of South Australia (Aitken et al., 2014 GRL). An over 1,900 km long magnetic and gravity lineament is imaged along the western flank of the Wilkes Subglacial Basin and is interpreted here as a major Paleoproterozoic suture zone linked to the collision of Laurentia and East Antarctica within Columbia. The proposed suture played a pivotal role helping localise Neoproterozoic Rodinia rifted margin evolution and forming a backstop for the Ross-Delamerian cycle of Gondwana amalgamation. Aeromagnetic and gravity imaging help determine the extent of a Keweenawan-age (ca 1.1 Ga) large igneous province in the Coats Land Block -isotopically tied with the Mid-Continent Rift System of Laurentia (Loewy et al., 2011 Geology). Imprints of Grenvillian magmatic arc accretion link together the Namaqua-Natal and Maud belts in South Africa and Dronning Maud Land within Rodinia. The aeromagnetically distinct Southeast Dronning Maud

  12. Structure of the Katabatic winds at Mizuho station, East Antarctica

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    Ohata, Tetsuo; Kobayashi, Shun'ichi; Ishikawa, Nobuyoshi; Kawaguchi, Sadao

    1985-10-01

    The structure of katabatic wind at Mizuho Station (70°42'S 44°20'E, 2230 m above sea level) in East Antarctica is described using data from radiosondes and a 30-m tower. This station is characterized by a so-called "cold katabatic" region. The frequency of occurrence of a single wind direction (in this case, east) is higher at Mizuho than at any other station in Antarctica. Because of this and the strong wind, well-developed sastrugi can be seen in the vicinity. The characteristics of the temperature inversion during clear sky conditions in winter were a quasi-isothermal layer from the surface up to 50 m capped by a thermocline of stronger temperature gradient. The maximum wind speed occurred near this height. The height of the top of the boundary layer, where turbulence becomes quite small, can be considered as the height above this thermocline. The d value of the stable boundary layer obtained by using the above height was 0.048-0.19 in the present case. This value is lower than the values obtained on the flat horizontal surface and on a slope of 0.002 m km-1 in the mid-latitudes. Taking the above height as the top of the katabatic wind, the two-layer model including the surface friction can explain the observational results well, better than the inversion wind model. This seems to indicate that the surface stress is important in the development of the katabatic wind at Mizuho but that the interfacial stress at the top of the inversion layer is not important in its development.

  13. Glimpses of East Antarctica: Aeromagnetic and satellite magnetic view from the central Transantarctic Mountains of East Antarctica

    Science.gov (United States)

    Finn, Carol A.; Goodge, John W.

    2010-01-01

    Aeromagnetic and satellite magnetic data provide glimpses of the crustal architecture within the Ross Sea sector of the enigmatic, ice-covered East Antarctic shield critical for understanding both global tectonic and climate history. In the central Transantarctic Mountains (CTAM), exposures of Precambrian basement, coupled with new high-resolution magnetic data, other recent aeromagnetic transects, and satellite magnetic and seismic tomography data, show that the shield in this region comprises an Archean craton modified both by Proterozoic magmatism and early Paleozoic orogenic basement reactivation. CTAM basement structures linked to the Ross Orogeny are imaged 50–100 km farther west than previously mapped, bounded by inboard upper crustal Proterozoic granites of the Nimrod igneous province. Magnetic contrasts between craton and rift margin sediments define the Neoproterozoic rift margin, likely reactivated during Ross orogenesis and Jurassic extension. Interpretation of satellite magnetic and aeromagnetic patterns suggests that the Neoproterozoic rift margin of East Antarctica is offset by transfer zones to form a stepwise series of salients tracing from the CTAM northward through the western margin of the Wilkes Subglacial Basin to the coast at Terre Adélie. Thinned Precambrian crust inferred to lie east of the rift margin cannot be imaged magnetically because of modification by Neoproterozoic and younger tectonic events.

  14. Height changes over subglacial Lake Vostok, East Antarctica: Insights from GNSS observations

    National Research Council Canada - National Science Library

    Richter, Andreas; Popov, Sergey V; Fritsche, Mathias; Lukin, Valery V; Matveev, Alexey Yu; Ekaykin, Alexey A; Lipenkov, Vladimir Ya; Fedorov, Denis V; Eberlein, Lutz; Schröder, Ludwig; Ewert, Heiko; Horwath, Martin; Dietrich, Reinhard

    2014-01-01

    Height changes of the ice surface above subglacial Lake Vostok, East Antarctica, reflect the integral effect of different processes within the subglacial environment and the ice sheet. Repeated GNSS...

  15. Ecobiological assessment of a freshwater lake at Schirmacher Oasis, East Antarctica, with reference to human activities

    Digital Repository Service at National Institute of Oceanography (India)

    Ingole, B.S.; Dhargalkar, V.K.

    The scale and magnitude of probable impact of human activities over a decade (1983-1994) on the freshwater lake Priyadarshini, at Schirmacher Oasis, East Antarctica, was assessed through an ecological study conducted over an annual cycle during...

  16. A note on the morphology and tectonics of Kainan Maru Seamount, East Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Kodagali, V.N.; Hagen, R.; Schenke, H.W.

    Kainan Maru Seamount lies off the northern end of the Gunnerus Ridge along the margin of East Antarctica. The seamount is separated from the Gunnerus Ridge by only about 15 km. Detailed Hydrosweep multibeam surveys of the seamount have shown...

  17. Recent snowfall anomalies in Dronning Maud Land, East Antarctica, in a historical and future climate perspective

    NARCIS (Netherlands)

    Lenaerts, J.T.M.|info:eu-repo/dai/nl/314850163; van Meijgaard, E.; van den Broeke, M.R.|info:eu-repo/dai/nl/073765643; Ligtenberg, S.R.M.|info:eu-repo/dai/nl/32821177X; Horwath, M.; Isaksson, E.

    2013-01-01

    Enhanced snowfall on the East Antarctic ice sheet is projected to significantly mitigate 21st century global sea level rise. In recent years (2009 and 2011), regionally extreme snowfall anomalies in Dronning Maud Land, in the Atlantic sector of East Antarctica, have been observed. It has been

  18. SMOS brightness data indicate ice thickness hence bedrock topography in east antarctica

    DEFF Research Database (Denmark)

    Skou, Niels; Kristensen, Steen Savstrup

    2017-01-01

    In order to evaluate a potential calibration target for spaceborne L-band radiometer systems, a 350 × 350 km area near the Concordia station on the East Antarctica plateau was mapped by an airborne L-band radiometer. Unexpectedly, the area showed significant brightness temperature spatial...... variations, well correlated with bedrock topography, hence ice thickness. Using SMOS data over a poorly known part of Antarctica, ice thickness in this area has been assessed, and an existing bedrock map has been improved....

  19. PROSPECTS FOR LIFE IN THE SUBGLACIAL LAKE VOSTOK, EAST ANTARCTICA

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    S. A. Bulat

    2012-01-01

    Full Text Available The objective was to estimate the genuine microbial content of ice samples from refrozen water (accretion ice from the subglacialLakeVostok(Antarctica buried beneath the 4-km thick East Antarctic ice sheet as well as surface snow nearby Vostok station. The lake ice samples were extracted by heavy deep ice drilling from3764 mbelow the surface reaching the depth3769.3 mby February 2011 (lake entering. High pressure, an ultra low carbon and chemical content, isolation, complete darkness and the probable excess of oxygen in water for millions of years characterize this extreme environment. A decontamination protocol was first applied to samples selected for the absence of cracks to remove the outer part contaminated by handling and drilling fluid. Preliminary indications showed the accretion ice samples to be almost gas free with the very low impurity content. Flow cytometry showed the very low unevenly distributed biomass in both accretion (0–19 cells per ml and glacier (0–24 cells per ml ice and surface snow (0–0.02 cells per ml as well while repeated microscopic observations were unsuccessful meaning that the whole Central East Antarctic ice sheet seems to be microbial cell-free.We used strategies of Ancient DNA research that include establishing contaminant databases and criteria to validate the amplification results. To date, positive results that passed the artifacts and contaminant databases have been obtained for a few bacterial phylotypes only in accretion ice samples featured by some bedrock sediments. Amongst them are the chemolithoautotrophic thermophile Hydrogenophilus thermoluteolus of beta-Proteobacteria, the actinobacterium rather related (95% to Ilumatobacter luminis and one unclassified phylotype distantly related (92% to soil-inhabiting uncultured bacteria. Combined with geochemical and geophysical considerations, our results suggest the presence of a deep biosphere, possibly thriving within some active faults of the bedrock

  20. Brief communication: Organochlorine pesticides in an archived firn core from Law Dome, East Antarctica

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    M. Bigot

    2016-10-01

    Full Text Available Organochlorine pesticides (OCPs were, for the first time, quantified in archived firn cores from East Antarctica representative of 1945–1957 and 1958–1967 (current era, C.E.. The core sections were melted under high-purity nitrogen atmosphere, and the meltwater was analysed. Methods allowed quantification of hexachlorocyclohexanes, heptachlor, trans-chlordane, dieldrin and endrin. While the core presented evidence of nominal contamination by modern-use chemicals, indicating handling and/or storage contamination, legacy OCP concentrations and deposition rates reported are orders of magnitude lower than those from Arctic regions, lending support for their validity. The study further provides a description of equipment used and suggests methods to overcome logistical challenges associated with trace organic contaminant detection in polar regions.

  1. Biodiversity and community structure of freeliving marine nematodes from the Larsemann Ice Shelf, East Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Ingole, B.S.; Singh, R.

    Subtidal (500-700 m) meiofaunal assemblage of the Larsemann Ice Shelf, East Antarctica, is described with special emphasis on the free-living marine nematodes. The sampling was conducted with a 25 x 25 x 40 cm VSNL Spade Box corer and sub...

  2. Glacier and deep water Holocene dynamics, Adélie Land region, East Antarctica

    NARCIS (Netherlands)

    Denis, D.; Crosta, X.; Schmidt, S.; Carson, D.; Ganeshram, R.; Renssen, H.; Bout-Roumazeilles, V.; Zaragosi, S.; Martin, B.; Giraudeau, J.

    2009-01-01

    This study presents a high-resolution multi-proxy investigation of sediment core MD03-2601 and documents major glacier oscillations and deep water activity during the Holocene in the Adélie Land region, East Antarctica. A comparison with surface ocean conditions reveals synchronous changes of

  3. Heterotrophic bacteria in soils of Larsemann Oasis of East Antarctica

    Science.gov (United States)

    Churilin, Nikita; Soina, Vera

    2015-04-01

    The study of diversity and functional state of microorganisms in subsurface rocks layers, their participation in the biochemical weathering and formation of organic horizons of soils is important for understanding ecology and microorganisms in Antarctic soils. The study of cultured forms of microorganisms and their potential viability is still relevant to characterize the physiological state, biological activity and resilience of microorganisms involved in the initial soil formation. Improvement of isolation techniques of viable bacteria from the extreme habitats has a particular importance for rising the efficiency of environmental monitoring. The aim of the study was to investigate the viable heterotrophic bacteria involved in the formation of soils from wet valleys Larsemann Oasis, which is one of the warmest ice-free space of East Antarctica. Soil samples were taken from the intermountain humid valleys, where silt-gravelly substrates formed moss, algae, lichen cover. We used nutrient solutions (trypticase soy, R2A and glucose-peptone) to isolate cultured bacteria and study their morphological types in the light microscope. The total number of microorganisms was determined by fluorescent microscopy with acridine orange. SEM was used for morphological studies of bacterial communities in situ. To activate the growth processes we added into nutrient solutions various regulatory metabolites that have dose-dependence and operate at the community level. Physiological and functional conditions were determined by the duration of the lag phase and specific growth rate of bacterial communities in nutrient solutions containing various organic substrates. Soils form under protection of «stone pavement» and organisms leave the surface, so the forming organo-mineral horizon occurs inside of rock, thus the microprofile can form on both sides of the organic horizons. UV radiation, lack of moisture and strong wind are main limiting factors for microorganisms' growth in

  4. Ice crystal precipitation at Dome C site (East Antarctica)

    Science.gov (United States)

    Santachiara, G.; Belosi, F.; Prodi, F.

    2016-01-01

    For the first time, falling ice crystals were collected on glass slides covered with a thin layer of 2% formvar in chloroform at the Dome Concordia site (Dome C), Antarctica. Samplings were performed in the framework of the 27th Italian Antarctica expedition of the Italian National Program for Research in Antarctica in the period 21 February-6 August 2012. Events of clear-sky precipitations and precipitations from clouds were considered and the replicas obtained were examined under Scanning Electron Microscope (SEM). Several shapes of ice crystals were identified, including ;diamond dust; (plates, pyramids, hollow and solid columns), and crystal aggregates varying in complexity. Single events often contained both small (10 μm to 50 μm) and large (hundreds of microns) crystals, suggesting that crystals can form simultaneously near the ground (height of a few hundred metres) and at higher layers (height of thousands of metres). Images of sampled crystal replicas showed that single bullets are not produced separately, but by the disintegration of combinations of bullets. Rimed ice crystals were absent in the Dome C samples, i.e. the only mode of crystal growth was water vapour diffusion. On considering the aerosol in the sampled crystals, we reached the conclusion that inertial impaction, interception and Brownian motion were insufficient to explain the scavenged aerosol. We therefore presume that phoretic forces play a role in scavenging during the crystal growth process.

  5. Optimal site selection for a high-resolution ice core record in East Antarctica

    Science.gov (United States)

    Vance, Tessa R.; Roberts, Jason L.; Moy, Andrew D.; Curran, Mark A. J.; Tozer, Carly R.; Gallant, Ailie J. E.; Abram, Nerilie J.; van Ommen, Tas D.; Young, Duncan A.; Grima, Cyril; Blankenship, Don D.; Siegert, Martin J.

    2016-03-01

    Ice cores provide some of the best-dated and most comprehensive proxy records, as they yield a vast and growing array of proxy indicators. Selecting a site for ice core drilling is nonetheless challenging, as the assessment of potential new sites needs to consider a variety of factors. Here, we demonstrate a systematic approach to site selection for a new East Antarctic high-resolution ice core record. Specifically, seven criteria are considered: (1) 2000-year-old ice at 300 m depth; (2) above 1000 m elevation; (3) a minimum accumulation rate of 250 mm years-1 IE (ice equivalent); (4) minimal surface reworking to preserve the deposited climate signal; (5) a site with minimal displacement or elevation change in ice at 300 m depth; (6) a strong teleconnection to midlatitude climate; and (7) an appropriately complementary relationship to the existing Law Dome record (a high-resolution record in East Antarctica). Once assessment of these physical characteristics identified promising regions, logistical considerations (for site access and ice core retrieval) were briefly considered. We use Antarctic surface mass balance syntheses, along with ground-truthing of satellite data by airborne radar surveys to produce all-of-Antarctica maps of surface roughness, age at specified depth, elevation and displacement change, and surface air temperature correlations to pinpoint promising locations. We also use the European Centre for Medium-Range Weather Forecast ERA 20th Century reanalysis (ERA-20C) to ensure that a site complementary to the Law Dome record is selected. We find three promising sites in the Indian Ocean sector of East Antarctica in the coastal zone from Enderby Land to the Ingrid Christensen Coast (50-100° E). Although we focus on East Antarctica for a new ice core site, the methodology is more generally applicable, and we include key parameters for all of Antarctica which may be useful for ice core site selection elsewhere and/or for other purposes.

  6. Optimal site selection for a high resolution ice core record in East Antarctica

    Science.gov (United States)

    Vance, T.; Roberts, J.; Moy, A.; Curran, M.; Tozer, C.; Gallant, A.; Abram, N.; van Ommen, T.; Young, D.; Grima, C.; Blankenship, D.; Siegert, M.

    2015-11-01

    Ice cores provide some of the best dated and most comprehensive proxy records, as they yield a vast and growing array of proxy indicators. Selecting a site for ice core drilling is nonetheless challenging, as the assessment of potential new sites needs to consider a variety of factors. Here, we demonstrate a systematic approach to site selection for a new East Antarctic high resolution ice core record. Specifically, seven criteria are considered: (1) 2000 year old ice at 300 m depth, (2) above 1000 m elevation, (3) a minimum accumulation rate of 250 mm yr-1 IE, (4) minimal surface re-working to preserve the deposited climate signal, (5) a site with minimal displacement or elevation change of ice at 300 m depth, (6) a strong teleconnection to mid-latitude climate and (7) an appropriately complementary relationship to the existing Law Dome record (a high resolution record in East Antarctica). Once assessment of these physical characteristics identified promising regions, logistical considerations (for site access and ice core retrieval) were briefly considered. We use Antarctic surface mass balance syntheses, along with ground-truthing of satellite data by airborne radar surveys to produce all-of-Antarctica maps of surface roughness, age at specified depth, elevation and displacement change and surface air temperature correlations to pinpoint promising locations. We also use the European Centre for Medium-Range Weather Forecast ERA 20th Century reanalysis (ERA-20C) to ensure a site complementary to the Law Dome record is selected. We find three promising sites in the Indian Ocean sector of East Antarctica in the coastal zone from Enderby Land to the Ingrid Christensen Coast (50-100° E). Although we focus on East Antarctica for a new ice core site, the methodology is more generally applicable and we include key parameters for all of Antarctica which may be useful for ice core site selection elsewhere and/or for other purposes.

  7. Early diagenetic siderite in the Panorama Point Beds (Radok Conglomerate, Early to Middle Permian), Prince Charles Mountains, East Antarctica

    National Research Council Canada - National Science Library

    Krajewski, Krzysztof P; Gonzhurov, Nikolai A; Laiba, Anatoly A; Tatur, Andrzej

    2010-01-01

    The Panorama Point Beds represent a subfacies of the Early to Middle Permian Radok Conglomerate, which is the oldest known sedimentary unit in the Prince Charles Mountains, MacRobertson Land, East Antarctica...

  8. Climatic variability in Princess Elizabeth Land (East Antarctica) over the last 350 years

    OpenAIRE

    A. A. Ekaykin; D. O. Vladimirova; Lipenkov, V. Y.; Masson-Delmotte, V.

    2017-01-01

    We use isotopic composition (δD) data from six sites in Princess Elizabeth Land (PEL) in order to reconstruct air temperature variability in this sector of East Antarctica over the last 350 years. First, we use the present-day instrumental mean annual surface air temperature data to demonstrate that the studied region (between Russia's Progress, Vostok and Mirny research stations) is characterized by uniform temperature variability. We thus construct a stacked record of the ...

  9. Ice sheet retreat and glacio-isostatic adjustment in Lützow-Holm Bay, East Antarctica

    Science.gov (United States)

    Verleyen, Elie; Tavernier, Ines; Hodgson, Dominic A.; Whitehouse, Pippa L.; Kudoh, Sakae; Imura, Satoshi; Heirman, Katrien; Bentley, Michael J.; Roberts, Steve J.; De Batist, Marc; Sabbe, Koen; Vyverman, Wim

    2017-08-01

    The East Antarctic Ice Sheet has relatively few field data to constrain its past volume and contribution to global sea-level change since the Last Glacial Maximum. We provide new data on deglaciation history and develop new relative sea-level (RSL) curves along an 80 km transect (from Skallen to Skarsvnes, Langhovde and the Ongul Islands) in Lützow Holm Bay, East Antarctica. The geological constraints were compared with output from two Glacial Isostatic Adjustment (GIA) models. The minimum radiocarbon age for regional deglaciation is c. 11,240 cal. yr BP on West Ongul Island with progressively younger deglaciation ages approaching the main regional ice outflow at Shirase Glacier. Marked regional differences in the magnitude and timing of RSL change were observed. More in particular, in Skarvsnes a minimum marine limit of 32.7 m was inferred, which is c. 12.7 m higher than previously published evidence, and at least 15 m higher than that reported in the other three ice-free areas. Current GIA model predictions slightly underestimate the rate of Late Holocene RSL fall at Skallen, Langhovde, and West Ongul, but provide a reasonable fit to the reconstructed minimum marine limit at these sites. GIA model predictions are unable to provide an explanation for the shape of the reconstructed RSL curve at Skarvsnes. We consider a range of possible explanations for the Skarvsnes RSL data and favour an interpretation where the anomalously high marine limit and rate of RSL fall is due to reactivation of a local fault.

  10. Analysis of strong wind events around Adelie Land, East Antarctica

    Directory of Open Access Journals (Sweden)

    G. Mastrantonio

    2003-06-01

    Full Text Available Strong wind events at Dumont d'Urville (DdU, an East Antarctic coastal station, and Dome C, an interior station, were studied to determine if the wind along the Adelie Land coast increases with the approach of the depression from the west of the site or after its passage to the east of it. The events for the year 1993 were studied using synoptic observations, mean sea level pressure charts and composite infrared satellite images. It was found that the winds are enhanced with the approach of a depression from the west towards the DdU coast. The wind increases in response to the decreasing pressure at the coastal site and increasing downslope pressure difference (dp. The wind starts decreasing once the system moves to the east of DdU and the pressure at DdU starts building up, as reported in some earlier studies. The response of wind to the approaching depression is not the same for all the events but depends on the downslope pressure difference and the movement of the depression that is often conditioned by the presence of a blocking high to the northeast. The wind comes down if the system starts penetrating inland due to the presence of the high pressure ridge to the northeast and decreasing dp. It is observed that the winds at Dome C increase to as high as 17 m s-1 with the inland penetration of the depression.

  11. Great earthquake East Japan observation by superconducting gravimeter in Antarctica

    Science.gov (United States)

    Ikeda, H.; Aoyama, Y.; Hayakawa, H.; Doi, K.; Shibuya, K.

    2012-12-01

    The seismic wave caused by the Great East Japan Earthquake that occurred on March 11, 2011 at 14:46 JST (magnitude: M 9.0, location: 38° 6.2 min N, 142° 51.6 min E, depth: 32 km) was clearly observed approximately 20 min later by the superconducting gravimeter at Syowa Station, about 14,000 km away from Japan. The observation of the free oscillations of the Earth will be reported compared to the observed records of the Sumatra earthquake on December 26, 2004 (magnitude: M 9.1) and Chile earthquake on February 27, 2010 (magnitude: M 8.8).

  12. Tectonic and erosion-driven uplift in the Gamburtsev Subglacial Mountains of East Antarctica

    Science.gov (United States)

    Ferraccioli, Fausto; Jordan, Tom; Watts, Tony; Bell, Robin; Jamieson, Stewart; Finn, Carol; Damaske, Detlef

    2014-05-01

    Understanding the mechanisms leading to intraplate mountain building remains a significant challenge in Earth Sciences compared to ranges formed along plate margins. The most enigmatic intraplate mountain range on Earth is the Gamburtsev Subglacial Mountains (GSM) located in the middle of the Precambrian East Antarctic Craton. During the International Polar Year, the AGAP project acquired 120,000 line km of new airborne geophysical data (Bell et al., 2011, Science) and seismological observations (Hansen et al., 2010, EPSL) across central East Antarctica. Models derived from these datasets provide new geophysical perspectives on crustal architecture and possible uplift mechanisms for the enigmatic GSM (Ferraccioli et al., 2011, Nature). The geophysical data define a 2,500-km-long Paleozoic to Mesozoic rift system in East Antarctica surrounding the GSM. A thick high-density lower crustal root is partially preserved beneath the range and has been interpreted as formed during the Proterozoic assembly of East Antarctica. Rifting could have triggered phase/density changes at deep crustal levels, perhaps restoring some of the latent root buoyancy, as well as causing rift-flank uplift. Permian rifting is well-established in the adjacent Lambert Rift, and was followed by Cretaceous strike-slip faulting and transtension associated with Gondwana break-up; this phase may have provided a more recent tectonic trigger for the initial uplift of the modern GSM. The Cretaceous rift-flank uplift model for the Gamburtsevs is appealing because it relates the initiation of intraplate mountain-building to large-scale geodynamic processes that led to the separation of Greater India from East Antarctica. It is also consistent with several geological and geophysical interpretations within the Lambert Rift. However, recent detrital thermochrology results from Oligocene-Quaternary sediments in Prydz Bay (Tochlin et al., 2012, G3) argue against the requirement for major Cretaceous rift

  13. Geophysical models for the tectonic framework of the Lake Vostok region, East Antarctica

    Science.gov (United States)

    Studinger, Michael; Karner, Garry D.; Bell, Robin E.; Levin, Vadim; Raymond, Carol A.; Tikku, Anahita A.

    2003-12-01

    Aerogeophysical and seismological data from a geophysical survey in the interior of East Antarctica were used to develop a conceptual tectonic model for the Lake Vostok region. The model is constrained using three independent data sets: magnetic, seismic, and gravimetric. A distinct change in the aeromagnetic anomaly character across Lake Vostok defines a crustal boundary. Depth to magnetic basement estimates image a 400-km-wide and more than 10-km-deep sedimentary basin west of the lake. Analysis of teleseismic earthquakes suggests a relatively thin crust beneath Lake Vostok consistent with predictions from kinematic and flexural gravity modelling. Magnetic, gravity, and subglacial topography data reveal a tectonic boundary within East Antarctica. Based on our kinematic and flexural gravity modelling, this tectonic boundary appears to be the result of thrust sheet emplacement onto an earlier passive continental margin. No data presently exist to date directly either the timing of passive margin formation or the subsequent shortening phase. The preserved thrust sheet thickness is related to the thickness of the passive margin crust. Because a significant amount of time is required to erode the thrust sheet topography, we suggest that these tectonic events are Proterozoic in age. Minor normal reactivation of the thrust sheet offers a simple mechanism to explain the formation of the Lake Vostok Basin. A low level of seismicity exists in the vicinity of this tectonic boundary. The existence of a crustal boundary in the Antarctic interior provides new constraints on the Proterozoic architecture of the East Antarctic craton.

  14. The Measurement of the Surface Temperature at Mizuho Station, East Antarctica

    OpenAIRE

    Mae,Shinji; Yamanouchi, Takashi; Wada, Makoto

    1981-01-01

    In 1979,the measurement of the surface temperature was made at Mizuho Station (70°42′S, 44°20′E, and 2230m above sea level), East Antarctica, by employing three different methods, a platinum resistance thermometer, a pyrgeometer and a radiation thermometer. These instruments were installed at different sites, on the drift snow, on the sastrugi and on the glazed surface. In winter the surface temperature measured by these different methods is roughly similar, but in spring and summer the surfa...

  15. The reduction of chloride ion concentration in basal ice near Hamna Icefall, East Antarctica

    OpenAIRE

    イイズカ, ヨシノリ; サタケ, ヒロシ; ワタナベ, オキツグ; Yoshinori , Iizuka; Hiroshi, Satake; Okitsugu, WATANABE

    2001-01-01

    The present paper mainly discusses chloride ions (Cl^-) in debris-laden basal ice near Hamna Icefall, Queen Maud Land, East Antarctica. The basal ice consists of alternating layers of bubble-free and bubbly ice of the order of mm to cm in thickness. Detailed analyses of Cl^- and stable isotopes (δ^O and δD) on the alternating layers were performed. The Cl^- concentrations in the bubble-free ice layers and in the bubbly ice layers whose isotopic fluctuations decrease from neighboring bubble-fr...

  16. Surface Roughness and Snow Accumulation in East Antarctica

    Science.gov (United States)

    Scambos, T. A.; Vornberger, P. L.; Bohlander, J. A.; Das, I.; Klinger, M.; Pope, A.; Lenaerts, J.; Fahnestock, M. A.

    2015-12-01

    A complex relationship exists between snow accumulation (e.g., net surface mass balance) and meter-scale surface roughness as represented by sastrugi and erosional structures over the East Antarctic Ice Sheet (EAIS). The morphology of the ice sheet at this scale is a result of a complex interaction between katabatic winds, synoptic storms, and the slope of the surface, all driving local patterns of snow accretion and sublimation. In megadune regions, the accumulation, surface slope, and surface roughness are highly correlated with slope. Smooth glazed surfaces are present on the steeper leeward wind-faces, and much rougher snow-accreting megadunes are present on the windward (depositional) slope. However, the highest elevation areas near the ridge crest of the EAIS (above ~3200 m) have a converse relationship between roughness and accumulation. Here, very low wind ridge crest areas are smooth and have higher accumulation than adjacent, slightly steeper regions that exhibit a slight increase in roughness. Below the main regions of megadunes (Landsat 8 acquisitions with available wind and accumulation data from climate model results and field measurements. Roughness is determined by sunlight scattering relative to viewing geometry (MISR) or from the amplitude of textural characteristics tied to surface sastrugi (Landsat 8). Both are validated by comparison with meter-scale images (WorldView-1) and field observations. MISR roughness mapping shows persistent qualitative patterns of surface roughness across the EAIS, but an absolute roughness scale mapping is difficult to generate because of complex viewing, illumination, and bi-directional reflectance variations of the snow surface. Landsat 8 band 8 provides a more constrained viewing geometry (nadir, sun-synchronous observations) and has a high radiometric sensitivity and adequate resolution (15 m) to reveal textural details in a consistent and quantitative way.

  17. New constraints on the Neogene plate kinematics of West and East Antarctica

    Science.gov (United States)

    Granot, R.; Dyment, J.; Szitkar, F.

    2016-12-01

    The motion between East and West Antarctic Plates during the last 26 million years (post-Adare seafloor spreading) is loosely constrained, and although it is often considered negligible, accumulating observations from along the rift system suggest that significant faulting and transtensional motion have occurred in that period. Part of the reason for this uncertainty is the complicated kinematic evolution of the oceanic crust found north of the Ross Sea and the lack of proper magnetic anomaly data at key tectonic locations. We have conducted a series of two cruises (TACT project) aboard M/V L'Astrolabe, the supply ship of Dumont d'Urville French Antarctic station, in February-March of 2012 and 2016 during which we have acquired total field magnetic profiles oriented along flowline direction and straddling the Tasman spreading corridor, located between Tasmania and the Balleny Islands and the Tasman and Balleny FZs. The new data allow us to refine the overall motion of the Macquarie Plate relative to Australia. After correction of this motion, the Tasman corridor, lying west of the Balleny FZ uncovers the Australia-East Antarctic plate motion, and the Balleny corridor, lying east of the FZ uncovers the Australia-West Antarctic plate motion, reveal a mismatched anomaly pattern that result from the Neogene relative plate motion between East and West Antarctica. We combine these new observations together with geological constraints from within the west Antarctic rift system to compute new rotation parameters that describe the relative plate motion between West and East Antarctica for the last 26 million years.

  18. Plankton diversity and aquatic ecology of a freshwater lake (L3 at Bharti Island, Larsemann Hills, east Antarctica

    Directory of Open Access Journals (Sweden)

    Pawan K. Bharti

    2015-04-01

    Full Text Available The Larsemann Hills range is an ice-free oasis on the Ingrid Christensen Coast of Princess Elizabeth Land, East Antarctica, which includes Bharti Island, Fisher Island, McLeod Island, Broknes Peninsula, Stornes Peninsula, and several other islands, promontories, and nunataks. The Larsemann Hills is an ice-free area of approximately 50 km2, located halfway between the Vestfold Hills and the Amery Ice Shelf on the south-eastern coast of Prydz Bay, Princess Elizabeth Land, East Antarctica. The ice-free area consists of two major peninsulas (Stornes and Broknes, four minor peninsulas, and approximately 130 near shore islands. The Larsemann Hills area contains more than 150 lakes at different Islands and peninsulas. Bharti Island of Larsemann Hills in east Antarctica was selected as a sampling site for the present study. Water sample was collected from a freshwater lake during XXXth Indian Scientific Expedition to Antarctica (ISEA and analyzed for the physico-chemical parameters, major elements, trace metals and major plankton diversity in surface lake water by following standard methodology. The concentrations of metals Cu, Pb, Cd, Zn and Cr were measured using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES. Phytoplankton and zooplankton were also assessed in the aquatic ecosystem of Lake L3 at Bharti Island, Larsemann Hills over east Antarctica. Psychrophillic bacteria were found 71 cfu in lake water, while total bacterial count was found to be 5.4 × 102cfu.

  19. Widespread wind-scour sites reduce total surface mass balance of East Antarctica

    Science.gov (United States)

    Das, I.; Bell, R. E.; Scambos, T.; Wolovick, M.; Nicolas, J. P.; Creyts, T. T.; Studinger, M.; Frearson, N.

    2012-12-01

    Accurate quantification of surface accumulation over Antarctica is important for mass balance estimates and climate studies based on chemical and isotopic analysis of ice cores. Significant uncertainties exist in the current compilations of surface mass balance (SMB) over East Antarctica, especially in the interior. Katabatic winds accelerating over steeper ice surface slopes erode and sublimate the surface snow and firn, producing extensive and localized (~ 10 km or less) regions of near-zero or negative surface mass balance. Surface mass balance estimates over Antarctica rely on widely scattered point measurements or atmospheric models that interpolate over large grids and do not capture these local processes, thereby overestimating the net surface accumulation. Here we use unconformities in airborne radar data combined with lidar derived surface roughness to identify extensive and persistent wind-scour zones at high elevations (>3800 m) near Dome A, Antarctica. These wind-scour zones form in areas of relatively steep surface slopes controlled by bedrock topography. Airborne data used in this study was collected during the AGAP survey in 2009. Approximately 125,500 sq. km area over Dome A was surveyed in a dense grid of 5km spacing in the along-track and 35 km in the across-track direction. The radar profile unconformities are observed in ~45 flight lines. Over a broad region (~ 200 km) surrounding the unconformities, lidar derived surface roughness is higher than the regional mean roughness. The elevated surface roughness indicates formation of microscale surface features like sastrugi and dunes due to increased wind activity. Truncation of internal layers by the unconformity in the radar images indicates ablation of near-surface firn layers. We interpret the surface projection of unconformities as wind-scour zones where the SMB is zero or negative. Using a calculated mean slope in the wind direction based on a 1 km DEM, near-surface winds and annual SMB from

  20. New geophysical views of Mt.Melbourne Volcano (East Antarctica)

    Science.gov (United States)

    Armadillo, E.; Gambetta, M.; Ferraccioli, F.; Corr, H.; Bozzo, E.

    2009-05-01

    Mt. Melbourne volcano is located along the transition between the Transantarctic Mountains and the West Antarctic Rift System. Recent volcanic activity is suggested by the occurrence of blankets of pyroclastic pumice and scoria fall around the eastern and southern flanks of Mt Melbourne and by pyroclastic layers interbedded with the summit snows. Geothermal activity in the crater area of Mount Melbourne may be linked to the intrusion of dykes within the last 200 years. Geophysical networks suggest that Mount Melbourne is a quiescent volcano, possibly characterised by slow internal dynamics. During the 2002-2003 Italian Antarctic campaign a high-resolution aeromagnetic survey was performed within the TIMM (Tectonics and Interior of Mt. Melbourne area) project. This helicopter-borne survey was flown at low-altitude and in drape-mode configuration (305 m above terrain) with a line separation less than 500 m. Our new high-resolution magnetic maps reveal the largely ice-covered magmatic and tectonic patters in the Mt. Melbourne volcano area. Additionally, in the frame of the UK-Italian ISODYN-WISE project (2005-06), an airborne ice-sounding radar survey was flown. We combine the sub-ice topography with images and models of the interior of Mt. Melbourne volcano, as derived from the high resolution aeromagnetic data and land gravity data. Our new geophysical maps and models also provide a new tool to study the regional setting of the volcano. In particular we re-assess whether there is geophysical evidence for coupling between strike-slip faulting, the Terror Rift, and Mount Melbourne volcano.

  1. Magnetotelluric investigation of the Vestfold Hills and Rauer Group, East Antarctica

    Science.gov (United States)

    Peacock, Jared R.; Selway, Katherine

    2016-01-01

    The Vestfold Hills and Rauer Group in East Antarctica have contrasting Archean to Neoproterozoic geological histories and are believed to be juxtaposed along a suture zone that now lies beneath the Sørsdal Glacier. Exact location and age of this suture zone are unknown, as is its relationship to regional deformation associated with the amalgamation of East Gondwana. To image the suture zone, magnetotelluric (MT) data were collected in Prydz Bay, East Antarctica, mainly along a profile crossing the Sørsdal Glacier and regions inland of the Vestfold Hills and Rauer Group islands. Time-frequency analysis of the MT time series yielded three important observations: (1) Wind speeds in excess of ∼8 m/s reduce coherence between electric and magnetic fields due to charged wind-blown particles of ice and snow. (2) Estimation of the MT transfer function is best between 1000 and 1400 UT when ionospheric Hall currents enhance the magnetic source field. (3) Nonplanar source field effects were minimal but detectable and removed from estimation of the MT transfer function. Inversions of MT data in 2-D and 3-D produce similar resistivity models, where structures in the preferred 3-D resistivity model correlate strongly with regional magnetic data. The electrically conductive Rauer Group is separated from the less conductive Vestfold Hills by a resistive zone under the Sørsdal Glacier, which is interpreted to be caused by oxidation during suturing. Though a suture zone has been imaged, no time constrains on suturing can be made from the MT data.

  2. Surface Clutter Suppression Techniques Applied to P-band Multi-Channel SAR Ice Sounder Data from East Antarctica

    DEFF Research Database (Denmark)

    Lin, Chung-Chi; Bekaert, David; Gebert, Nicolas

    ., Lausanne, developed and built the radiator-elements of the enhanced POLARIS. Several datasets were acquired in the multi-channel configuration during the Feb. 2011 campaign over East Antarctica. The POLARIS instrument will be briefly introduced, followed by an overview of the sounding campaign. Finally...

  3. Upward continuation of Dome-C airborne gravity and comparison with GOCE gradients at orbit altitude in east Antarctica

    DEFF Research Database (Denmark)

    Yildiz, Hasan; Forsberg, René; Tscherning, Carl Christian

    2017-01-01

    An airborne gravity campaign was carried out at the Dome-C survey area in East Antarctica between the 17th and 22nd of January 2013, in order to provide data for an experiment to validate GOCE satellite gravity gradients. After typical filtering for airborne gravity data, the cross-over error...

  4. Inferences from stable water isotopes on the Holocene evolution of Scharffenbergbotnen blue-ice area, East Antarctica

    NARCIS (Netherlands)

    Sinisalo, Anna; Grinsted, Aslak; Moore, John C.; Meijer, Harro A. J.; Martma, Tonu; Van De Wal, Roderik S. W.

    2007-01-01

    We show that it is possible to extract a high-resolution (annual) paleoclimate record from the surface of a blue-ice area (BIA). The variability of the surface stable-isotope values suggests that almost all the surface ice in Scharffenbergbotnen BIA, East Antarctica, is of Holocene age. The isotopic

  5. Borehole temperatures reveal a changed energy budget at Mill Island, East Antarctica, over recent decades

    Directory of Open Access Journals (Sweden)

    J. L. Roberts

    2013-02-01

    Full Text Available A borehole temperature record from the Mill Island (East Antarctica icecap reveals a large surface warming signal manifested as a 0.75 K temperature difference over the approximate 100 m depth in the zone of zero annual amplitude below the seasonally varying zone. The temperature profile shows a break in gradient around 49 m depth, which we model with inverse numerical simulations, indicating that surface warming started around the austral summer of 1980/81 AD ±5 yr. This warming of approximately 0.37 K per decade is consistent with trends seen in both instrumental and other reconstructions for Antarctica and, therefore, suggests that regional- rather than local-scale processes are largely responsible. Alteration of the surface energy budget arising from changes in radiation balances due to local cloud, the amount of liquid deposition and local air temperatures associated with altered air/sea exchanges also potentially plays a role at this location due to the proximity of the Shackleton Ice Shelf and sea-ice zone.

  6. Bacterial community initial development in proglacial soils of Larsemann hill, East Antarctica

    Science.gov (United States)

    Ma, H.; Yan, W.; Shi, G.; Sun, B.; Zhang, Y.; Xiao, X.

    2016-12-01

    Glacial forefields are considered ideal places to explore how microbial communities will response to climate-driven environmental changes. Our knowledge of how the bacterial community activities and structure was influenced by changing environment due to glacier retreat is still very limited, especially at the initial stage of glacier retreat. The short gradient soil samples including the ice free and ice covered sites were sampled in the forehead of East Antarctica ice sheet, in Larsemann Hills. By employing the Miseq sequencing methods, 1.8 x104 high-quality sequences were gotten for each sample and the bacterial diversity including abundant bacteria and rare bacteria were studied and compared between the gradient samples. Even though in such an extreme stress condition, the bacterial diversity was high. The coefficient of variance between the five sites of abundant group was 0.886 which was higher than that of the top 20 rare group (0.159) significantly (unpaired t test, p-valuebank to keep the community functionality in the forehead of sheet. And the ice thickness was the major factor to affect the abundant bacterial community. Given the fact that Antarctica environment was more sensitive to the global warming, the study about abundant and rare bacteria response to condition change will be helpful to precisely predict community response to climate change in polar region. This finding will improve the understanding about the relationship between community structure and environment condition in extreme stress condition.

  7. Spatial distributions of soluble salts in surface snow of East Antarctica

    Directory of Open Access Journals (Sweden)

    Yoshinori Iizuka

    2016-07-01

    Full Text Available To better understand how sea salt reacts in surface snow of Antarctica, we collected and identified non-volatile particles in surface snow along a traverse in East Antarctica. Samples were obtained during summer 2012/2013 from coastal to inland regions within 69°S to 80°S and 39°E to 45°E, a total distance exceeding 800 km. The spatial resolution of samples is about one sample per latitude between 1500 and 3800 m altitude. Here, we obtain the atomic ratios of Na, S and Cl, and calculate the masses of sodium sulphate and sodium chloride. The results show that, even in the coast snow sample (69°S, sea salt is highly modified by acid (HNO3 or H2SO4. The fraction of sea salt that reacts with acid increases in the region from 70°S to 74°S below 3000 m a.s.l., where some NaCl remains. At the higher altitudes (above 3300 m a.s.l. in the inland region (74°S to 80°S, the reaction uses almost all of the available NaCl.

  8. Sediment profile characterisation at contaminated and reference locations in the Windmill Islands, East Antarctica.

    Science.gov (United States)

    Palmer, A S; Snape, I; Townsend, A T; Stark, J S; Samson, C; Riddle, M J

    2010-09-01

    Sediment profiles for pH, Eh, 28 elements, water and organic content are presented here for human impacted and reference locations in the Windmill Islands, East Antarctica. Variations in element concentrations are observed with increasing depth, especially at Brown Bay where the impact of past human activities is most pronounced in the top 10 cm. Spatial differences were observed between sediment profiles at reference and impacted locations and were largely explained by Pb variability in the top 5 cm. Median element concentrations from surface, middle and bottom regions of the sediment profile were compared to composite sample medians (no depth stratigraphy) for 11 elements at O'Brien Bay (reference) and Brown Bay (impacted). Pronounced differences were observed for Brown Bay, particularly surface and middle sections, implying that composite samples dilute the near surface anthropogenic signal by mixing with deeper uncontaminated sediment. Copyright 2010 Elsevier Ltd. All rights reserved.

  9. Understanding the Role of Wind in Reducing the Surface Mass Balance Estimates over East Antarctica

    Science.gov (United States)

    Das, I.; Scambos, T. A.; Koenig, L.; Creyts, T. T.; Bell, R. E.; van den Broeke, M. R.; Lenaerts, J.; Paden, J. D.

    2014-12-01

    Accurate quantification of surface snow-accumulation over Antarctica is important for mass balance estimates and climate studies based on ice core records. An improved estimate of surface mass balance must include the significant role near-surface wind plays in the sublimation and redistribution of snow across Antarctica. We have developed an empirical model based on airborne radar and lidar observations, and modeled surface mass balance and wind fields to produce a continent-wide prediction of wind-scour zones over Antarctica. These zones have zero to negative surface mass balance, are located over locally steep ice sheet areas (>0.002) and controlled by bedrock topography. The near-surface winds accelerate over these zones, eroding and sublimating the surface snow. This scouring results in numerous localized regions (≤ 200 km2) with reduced surface accumulation. Each year, tens of gigatons of snow on the Antarctic ice sheet are ablated by persistent near-surface katabatic winds over these wind-scour zones. Large uncertainties remain in the surface mass balance estimates over East Antarctica as climate models do not adequately represent the small-scale physical processes that lead to mass loss through sublimation or redistribution over the wind-scour zones. In this study, we integrate Operation IceBridge's snow radar over the Recovery Ice Stream with a series of ice core dielectric and depth-density profiles for improved surface mass balance estimates that reflect the mass loss over the wind-scour zones. Accurate surface mass balance estimates from snow radars require spatially variable depth-density profiles. Using an ensemble of firn cores, MODIS-derived surface snow grain size, modeled accumulation rates and surface temperatures from RACMO2, we assemble spatially variable depth-density profiles and use our mapping of snow density variations to estimate layer mass and net accumulation rates from snow radar layer data. Our study improves the quantification of

  10. Triassic tetrapods from antarctica: evidence for continental drift.

    Science.gov (United States)

    Elliot, D H; Colbert, E H; Breed, W J; Jensen, J A; Powell, J S

    1970-09-18

    During the austral summer of 1969-1970 bones of Lower Triassic vertebrates were excavated from coarse quartzose sandstones forming stream channel deposits of the Fremouw Formation at Coalsack Bluff, in the Transantarctic Mountains of Antarctica. This is the first assemblage of fossil tetrapods of significant geologic age to be found on the Antarctic Continent. The fossils include labyrinthodont amphibians, presumed thecodont reptiles, and therapsid reptiles, including the definitive genus, Lystrosaurus. This genus is typical of the Lower Triassic of southern Africa, and is also found in India and China. Lystrosaurus and associated vertebrates found in Antarctica were land-living animals: therefore their presence on the South Polar Continent would seem to indicate the contiguity of Antarctica, Africa, and India in Early Triassic times.

  11. Dust composition changes from Taylor Glacier (East Antarctica) during the last glacial-interglacial transition: A multi-proxy approach

    Science.gov (United States)

    Aarons, Sarah M.; Aciego, Sarah M.; Arendt, Carli A.; Blakowski, Molly A.; Steigmeyer, August; Gabrielli, Paolo; Sierra-Hernández, M. Roxana; Beaudon, Emilie; Delmonte, Barbara; Baccolo, Giovanni; May, Nathaniel W.; Pratt, Kerri A.

    2017-04-01

    Mineral dust is transported in the atmosphere and deposited in oceans, ice sheets and the terrestrial biosphere. Temporal changes in locations of dust source areas and transport pathways have implications for global climate and biogeochemical cycles. The chemical and physical characterization of the dust record preserved in ice cores is useful for identifying of dust source regions, dust transport, dominant wind direction and storm trajectories. Here, we present a 50,000-year geochemical characterization of mineral dust entrapped in a horizontal ice core from the Taylor Glacier in East Antarctica. Strontium (Sr) and neodymium (Nd) isotopes, grain size distribution, trace and rare earth element (REE) concentrations, and inorganic ion (Cl- and Na+) concentrations were measured in 38 samples, corresponding to a time interval from 46 kyr before present (BP) to present. The Sr and Nd isotope compositions of insoluble dust in the Taylor Glacier ice shows distinct changes between the Last Glacial Period (LGP in this study ranging from ∼46.7-15.3 kyr BP) the early Holocene (in this study ranging from ∼14.5-8.7 kyr BP), and zero-age samples. The 87Sr/86Sr isotopic composition of dust in the Taylor Glacier ice ranged from 0.708 to 0.711 during the LGP, while the variability during the early Holocene is higher ranging from 0.707 to 0.714. The εNd composition ranges from 0.1 to -3.9 during the LGP, and is more variable from 1.9 to -8.2 during the early Holocene. The increased isotopic variability during the early Holocene suggests a shift in dust provenance coinciding with the major climate transition from the LGP to the Holocene. The isotopic composition and multiple physical and chemical constraints support previous work attributing Southern South America (SSA) as the main dust source to East Antarctica during the LGP, and a combination of both local Ross Sea Sector dust sources and SSA after the transition into the Holocene. This study provides the first high time

  12. Unveiling subglacial geology and crustal architecture in the Recovery frontier of East Antarctica with recent aeromagnetic and airborne gravity imaging

    Science.gov (United States)

    Ferraccioli, F.; Forsberg, R.; Jordan, T. A.; Matsuoka, K.; Olsen, A.; King, O.; Ghidella, M.

    2014-12-01

    East Antarctica is the least known continent, despite being a keystone in the Gondwana, Rodinia and Columbia supercontinents. Significant progress has been made in recent years in exploring East Antarctica using aeromagnetic and airborne gravity together with radar. Major aerogeophysical campaigns over the Wilkes Subglacial Basin (Ferraccioli et al., 2009 Tectonophysics), the Aurora Subglacial Basin (Aitken et al., 2014 GRL) and the Gamburtsev Subglacial Mountains (Ferraccioli et al., 2011, Nature) provide new glimpses into the crustal architecture of East Antarctica. However, a major sector of the continent that includes key piercing points for reconstructing linkages between East Antarctica and Laurentia within Rodinia, and also the inferred remnants of a major suture zone active during Gondwana amalgamation in Pan-African times (ca 500 Ma), has remained largely terra incognita. Here we present the results of a major aerogeophysical survey flown over this sector of East Antarctica, named the Recovery Frontier, from the major ice stream flowing in the region. The survey was flown during the IceGRAV 2012-13 field season, as part of a Danish-Norwegian-UK and Argentine collaboration and led to the collection of 29,000 line km of radar, laser altimetry, gravity and magnetic data. We present the new aeromagnetic anomaly, Bouguer and residual and enhanced anomaly maps for the region. Using these images we trace the extent of major subglacial faults and interpret these to delineate the tectonic boundaries separating the Coast block, the Shackleton Range and the Dronning Maud Land crustal provinces. Forward magnetic and gravity modelling enables us to examine the inferred Pan-African age suture zone in the Shackleton Range and address its tectonic relationships with older terranes of the Mawson Craton and Grenvillian-age terranes of Dronning Maud Land and interior East Antarctica. Finally, we present new models to test our hypothesis that Paleozoic to Mesozoic rift basins

  13. Arc Boudinage, Basin Inversion and Obduction in an Evolving Subduction System of East Antarctica

    Science.gov (United States)

    Ferraccioli, F.; Balbi, P.; Armadillo, E.; Crispini, L.; Capponi, G.

    2014-12-01

    The paleo-Pacific margin of Gondwana experienced protracted subduction and accretionary tectonics starting in late Neoproterozic-early Cambrian times. Northern Victoria Land (NVL), in East Antarctica, preserves a cryptic record of these active margin processes. Most models indicate that NVL contains three main terranes, namely the Robertson Bay, Bowers and Wilson terranes. Significant debate centres, however, on whether these are far travelled terranes with respect to the East Antarctic Craton, and on the tectonic and magmatic processes that affected its active margin and were ultimately responsible for the formation of the Ross Orogen. Here we interpret new aeromagnetic, aerogravity and land-gravity compilations that enable us to trace the extent of major subglacial faults in the basement of NVL, examine crustal architecture, and propose a new evolutionary model for the active margin of the craton. Prominent aeromagnetic anomalies at the edge of the Wilkes Subglacial Basin delineate the extent of an early-stage magmatic arc (ca 530 Ma?). This arc may have accreted as an exotic element onto the former Neoproterozoic rifted margin of East Antarctica or (perhaps more likely) developed in situ upon a pre-existing suture. Remnants of magnetic arc basement are also identified ca 150 km further to the east within the Wilson Terrane (WT). We propose that these were originally adjacent arc segments and that transtension triggered significant arc boudinage separating these segments. Transtension may have created accommodation space for the development of thick Cambrian sedimentary basins, which are marked by regional magnetic lows with an en-echelon geometry. Basin inversion likely occurred in a later traspressional stage of the Ross-Delamerian Orogen (ca. 490-460 Ma) that triggered the development of a major pop-up structure within the WT. Several buried thrusts of the pop-up can be traced in the aeromagnetic images and a prominent residual gravity high delineates its high

  14. Accurate delineation of the grounding line from kinematic GPS measurements. Application to an outlet glacier in East Antarctica

    Science.gov (United States)

    Le Meur, E.; Sacchettini, M.; Durand, G.; Drouet, A.; Rignot, E. J.; Mouginot, J.; Young, D. A.; Blankenship, D.; Greenbaum, J.

    2011-12-01

    Polar ice sheets have a huge potential in terms of sea level rise. Recent measurements show clear evidence of a generalized speeding up of outlet glaciers in Greenland and West Antarctica and the question whether similar behaviors are to be expected in East Antarctica is all the more crucial as this latter represents the largest ice reservoir. Moreover, many glaciers in the Wilkes-Terre Adélie sector are in a supposedly unstable configuration due to a landward downsloping bedrock. As a consequence, the Astrolabe Glacier (Terre Adélie land) was selected as a test zone for extensive field surveys like surface and bedrock heights, surface velocities, mass balance measurements. Among those, the exact position of the grounding line is fundamental as it represents a strong transition in the flow regime when the basal drag of the grounded ice reduces to virtually zero when this latter starts to float over the ocean. We here propose a method based on GPS measurements along various profiles in order to identify the presence or not of tidal movements of the ice surface indicating floating ice. The amplitude of the tides of the order of a meter requires accurate data only possible with the differential GPS method. Processing of these GPS data along selected profiles allows us to propose a position for the grounding line (hydrostatic one) which we then compare to that obtained from remote techniques (Landsat-7, ICESat, differential satellite synthetic-aperture radar interferometry). The exact position of the grounding line as well as the exact surface height along a radar transect across the glacier (giving the underlying bedrock topography) is also used to infer a mean density for the whole ice column by applying the hydrostatic criterion and a firn depth correction.

  15. Potential groundwater and heterogeneous heat source contributions to ice sheet dynamics in critical submarine basins of East Antarctica

    Science.gov (United States)

    Gooch, Brad T.; Young, Duncan A.; Blankenship, Donald D.

    2016-02-01

    We present the results of two numerical models describing contributions of groundwater and heterogeneous heat sources to ice dynamics directly relevant to basal processes in East Antarctica. A two-phase, one-dimensional hydrothermal model demonstrates the importance of groundwater flow in vertical heat flux advection near the ice-bed interface. Typical, conservative vertical components of groundwater volume fluxes (from either topographical gradients or vertically channeled flow) on the order of ±1-10 mm/yr can alter vertical heat flux by ±50-500 mW/m2 given parameters typical for the interior of East Antarctica. This heat flux has the potential to produce considerable volumes of meltwater depending on basin geometry and geothermal heat production. A one-dimensional hydromechanical model demonstrates that groundwater is mainly recharged into saturated, partially poroelastic (i.e., vertical stress only; not coupled to a deformation equation) sedimentary aquifers during ice advance. During ice retreat, groundwater discharges into the ice-bed interface, which may contribute to water budgets on the order of 0.1-1 mm/yr. We also present an estimated map of potentially heterogeneous heat flow provinces using radiogenic heat production data from East Antarctica and southern Australia, calculated sedimentary basin depths, and radar-derived bed roughness. These are overlaid together to delineate the areas of greatest potential effect from these modeled processes on the ice sheet dynamics of the East Antarctic Ice Sheet.

  16. High-resolution 900 year volcanic and climatic record from the Vostok area, East Antarctica

    Science.gov (United States)

    Osipov, E. Y.; Khodzher, T. V.; Golobokova, L. P.; Onischuk, N. A.; Lipenkov, V. Y.; Ekaykin, A. A.; Shibaev, Y. A.; Osipova, O. P.

    2014-05-01

    Ion chromatography measurements of 1730 snow and firn samples obtained from three short cores and one pit in the Vostok station area, East Antarctica, allowed for the production of the combined volcanic record of the last 900 years (AD 1093-2010). The resolution of the record is 2-3 samples per accumulation year. In total, 24 volcanic events have been identified, including seven well-known low-latitude eruptions (Pinatubo 1991, Agung 1963, Krakatoa 1883, Tambora 1815, Huanaputina 1600, Kuwae 1452, El Chichon 1259) found in most of the polar ice cores. In comparison with three other East Antarctic volcanic records (South Pole, Plateau Remote and Dome C), the Vostok record contains more events within the last 900 years. The differences between the records may be explained by local glaciological conditions, volcanic detection methodology, and, probably, differences in atmospheric circulation patterns. The strongest volcanic signal (both in sulfate concentration and flux) was attributed to the AD 1452 Kuwae eruption, similar to the Plateau Remote and Talos Dome records. The average snow accumulation rate calculated between volcanic stratigraphic horizons for the period AD 1260-2010 is 20.9 mm H2O. Positive (+13%) anomalies of snow accumulation were found for AD 1661-1815 and AD 1992-2010, and negative (-12%) for AD 1260-1601. We hypothesized that the changes in snow accumulation are associated with regional peculiarities in atmospheric transport.

  17. Infrasound Observations at the Lützow-Holm Bay region, East Antarctica

    Science.gov (United States)

    Kanao, M.; Murayama, T.; Yamamoto, M.; Ishihara, Y.; Kakinami, Y.

    2013-12-01

    Characteristic infrasound waves observed at Antarctic stations demonstrate physical interaction involving surface environmental changes in the continent and surrounding oceans. A Chaparral type infrasound sensor was installed at Syowa Station (SYO; 39E, 69S), East Antarctica, as one of the projects of the International Polar Year (IPY2007-2008). Continuous recording data during the three seasons in 2008-2010 clearly indicate a contamination of the background oceanic signals (microbaroms) with peaks between 4 and 10 s observed during a whole season. The peak amplitudes of the microbaroms has relatively lower amplitudes during austral winters, caused by a larger amount of sea-ice extending around the Lützow-Holm Bay near SYO, with decreasing ocean wave loading effects. Microbaroms measurements are a useful tool for characterizing ocean wave climate, complementing other oceanographic and geophysical data. In the austral summer in 2013, a few number of infrasound stations was established along the coast of LHB. Two different size of infrasound arrays were installed at SYO (100m spacing triangle) and S16 area on the continental ice sheet (1000m spacing triangle). In addition, isolated single stations were developed at two outcrops along the LHB. The new two infrasound arrays clearly detected the microbaroms with their propagating directions from the Southern Ocean. Moreover, characteristic signals associated with calving of the edge of glaciers, as well as the shock waves generated from meteorite injection at the Russian Republic on 15 February 2013. In this presentation, several kind of remarkable data are demonstrated. Detail measurements of the infrasound waves in Antarctica could be a new proxy for monitoring a regional environmental change together with temporal climate variations in polar region.

  18. Snow precipitation at four ice core sites in East Antarctica: provenance, seasonality and blocking factors

    Science.gov (United States)

    Scarchilli, Claudio; Frezzotti, Massimo; Ruti, Paolo Michele

    2011-11-01

    Snow precipitation is the primary mass input to the Antarctic ice sheet and is one of the most direct climatic indicators, with important implications for paleoclimatic reconstruction from ice cores. Provenance of precipitation and the dynamic conditions that force these precipitation events at four deep ice core sites (Dome C, Law Dome, Talos Dome, and Taylor Dome) in East Antarctica were analysed with air mass back trajectories calculated using the Lagrangian model and the mean composite data for precipitation, geopotential height and wind speed field data from the European Centre for Medium Range Weather Forecast from 1980 to 2001. On an annual basis, back trajectories showed that the Atlantic-Indian and Ross-Pacific Oceans were the main provenances of precipitation in Wilkes Land (80%) and Victoria Land (40%), respectively, whereas the greatest influence of the ice sheet was on the interior near the Vostok site (80%) and in the Southwest Ross Sea (50%), an effect that decreased towards the coast and along the Antarctic slope. Victoria Land received snowfall atypically with respect to other Antarctica areas in terms of pathway (eastern instead of western), seasonality (summer instead of winter) and velocity (old air age). Geopotential height patterns at 500 hPa at low (>10 days) and high (2-6 days) frequencies during snowfall cycles at two core sites showed large positive anomalies at low frequencies developing in the Tasman Sea-Eastern Indian Ocean at higher latitudes (60-70°S) than normal. This could be considered part of an atmospheric blocking event, with transient eddies acting to decelerate westerlies in a split region area and accelerate the flow on the flanks of the low-frequency positive anomalies.

  19. Climatic variability in Princess Elizabeth Land (East Antarctica) over the last 350 years

    Science.gov (United States)

    Ekaykin, Alexey A.; Vladimirova, Diana O.; Lipenkov, Vladimir Y.; Masson-Delmotte, Valérie

    2017-01-01

    We use isotopic composition (δD) data from six sites in Princess Elizabeth Land (PEL) in order to reconstruct air temperature variability in this sector of East Antarctica over the last 350 years. First, we use the present-day instrumental mean annual surface air temperature data to demonstrate that the studied region (between Russia's Progress, Vostok and Mirny research stations) is characterized by uniform temperature variability. We thus construct a stacked record of the temperature anomaly for the whole sector for the period of 1958-2015. A comparison of this series with the Southern Hemisphere climatic indices shows that the short-term inter-annual temperature variability is primarily governed by the Antarctic Oscillation (AAO) and Interdecadal Pacific Oscillation (IPO) modes of atmospheric variability. However, the low-frequency temperature variability (with period > 27 years) is mainly related to the anomalies of the Indian Ocean Dipole (IOD) mode. We then construct a stacked record of δD for the PEL for the period of 1654-2009 from individual normalized and filtered isotopic records obtained at six different sites (PEL2016 stacked record). We use a linear regression of this record and the stacked PEL temperature record (with an apparent slope of 9 ± 5.4 ‰ °C-1) to convert PEL2016 into a temperature scale. Analysis of PEL2016 shows a 1 ± 0.6 °C warming in this region over the last 3 centuries, with a particularly cold period from the mid-18th to the mid-19th century. A peak of cooling occurred in the 1840s - a feature previously observed in other Antarctic records. We reveal that PEL2016 correlates with a low-frequency component of IOD and suggest that the IOD mode influences the Antarctic climate by modulating the activity of cyclones that bring heat and moisture to Antarctica. We also compare PEL2016 with other Antarctic stacked isotopic records. This work is a contribution to the PAGES (Past Global Changes) and IPICS (International Partnerships in

  20. A glaciochemical study of the 120 m ice core from Mill Island, East Antarctica

    Science.gov (United States)

    Inoue, Mana; Curran, Mark A. J.; Moy, Andrew D.; van Ommen, Tas D.; Fraser, Alexander D.; Phillips, Helen E.; Goodwin, Ian D.

    2017-05-01

    A 120 m ice core was drilled on Mill Island, East Antarctica (65°30' S, 100°40' E) during the 2009/2010 Australian Antarctic field season. Contiguous discrete 5 cm samples were measured for hydrogen peroxide, water stable isotopes, and trace ion chemistry. The ice core was annually dated using a combination of chemical species and water stable isotopes. The Mill Island ice core preserves a climate record covering 97 years from 1913 to 2009 CE, with a mean snow accumulation of 1.35 m (ice-equivalent) per year (mIE yr-1). This northernmost East Antarctic coastal ice core site displays trace ion concentrations that are generally higher than other Antarctic ice core sites (e.g. mean sodium levels were 254 µEq L-1). The trace ion record at Mill Island is characterised by a unique and complex chemistry record with three distinct regimes identified. The trace ion record in regime A displays clear seasonality from 2000 to 2009 CE; regime B displays elevated concentrations with no seasonality from 1934 to 2000 CE; and regime C displays relatively low concentrations with seasonality from 1913 to 1934 CE. Sea salts were compared with instrumental data, including atmospheric models and satellite-derived sea-ice concentration, to investigate influences on the Mill Island ice core record. The mean annual sea salt record does not correlate with wind speed. Instead, sea-ice concentration to the east of Mill Island likely influences the annual mean sea salt record. A mechanism involving formation of frost flowers on sea ice is proposed to explain the extremely high sea salt concentration. The Mill Island ice core records are unexpectedly complex, with strong modulation of the trace chemistry on long timescales.

  1. Teleseismic SKS splitting beneath East Antarctica using broad-band stations around Soya Coast

    Science.gov (United States)

    Usui, Y.; Kanao, M.

    2006-12-01

    We observed shear wave splitting of SKS waves from digital seismographs that are recorded at 5 stations around Soya Coast in the Lutzow-Holm Bay, East Antarctica. Their recording systems are composed of a three-component broadband seismometer (CMG-40T), a digital recording unit and a solar power battery supply. The events used were selected from 1999 to 2004 and phase arrival times were calculated using the IASPEI91 earth model (Kennet, 1995). In general, we chose the data from earthquakes with m>6.0 and a distance range 85° < Δ < 130° for the most prominent SKS waves We used the methods of Silver and Chan (1991) for the inversion of anisotropy parameters and estimated the splitting parameters φ (fast polarization direction) and δt (delay time between split waves) assuming a single layer of hexagonal symmetry with a horizontal symmetry axis. The weighted averages of all splitting parameters (φ, δt) for each station are AKR (30±4, 1.30±0.2), LNG (58±6, 1.27±0.2), SKL (67±10, 0.94±0.2), SKV (40±6, 1.28±0.3) and TOT (52±8, 1.26±0.3), where the weights are inversely proportional to the standard deviations for each solution. As compared to typical delay times of SKS waves which show 1.2s (Silver and Chan 1991; Vinnik et al., 1992), the result shows generally the same value. In previous study, Kubo and Hiramatsu (1998) estimate the splitting parameter for Syowa station (SYO), where is located near our using stations in East Antarctica, and the results are (49±3, 0.70±0.1). Although it is consistent with our results for fast polarization direction, δt for our results are large relatively to those of SYO. The difference may be due to either different incident angle or more complex anisotropic structure. We found that fast polarization direction is systematically parallel to coast line in the Lutzow-Holm Bay, East Antarctica, which is consistent with NE-SW paleo compressional stress. The absolute plate motion based on the HS2-NUVEL1 (Gripp and Gordon

  2. Chemical composition of aerosol in the atmospheric surface layer of the East Antarctica coastal zone

    Directory of Open Access Journals (Sweden)

    L. P. Golobokova

    2016-01-01

    Full Text Available Chemical composition of aerosol in the ground layer of the coastal zone in East Antarctica is analyzed in the article. The aerosol samples were taken in 2006–2015 during seasonal works of the Russian Antarctic Expeditions (RAE, namely, these were 52nd–53rd, 55th, and 58th–60th expeditions. Samples were taken in the 200‑km band of the sea-shore zone along routes of the research vessels (REV «Akademik Fedorov» and «Akademik Treshnikov» as well as on territories of the Russian stations Molodezhnaya and Mirny. Although the results obtained did show the wide range of the aerosol concentrations and a certain variability of their chemical composition, some common features of the variability were revealed. Thus, during the period from 2006 to 2014 a decrease of average values of the sums were noted. Spatially, a tendency of decreasing of the ion concentrations was found in the direction from the station Novolazarevskaya to the Molodezhnaya one, but the concentrations increased from the Molodezhnaya to the station Mirny. The sum of ions of the aerosol in the above mentioned coastal zone was, on the average, equal to 2.44 μg/m3, and it was larger than that on the territory of the Antarctic stations Molodezhnaya (0,29 μg/m3 and Mirny (0,50 ág / m3. The main part to the sum of the aerosol ions on the Antarctic stations was contributed by Na+, Ca2+, Cl−, SO4 2−. The main ions in aerosol composition in the coastal zone are ions Na+ and Cl−. The dominant contribution of the sea salt and SO4 2− can be traced in not only the composition of atmospheric aerosols, but also in the chemical composition of the fresh snow in the coastal areas of East Antarctica: at the Indian station Maitri, on the Larsemann Hills, and in a boring located in 55.3 km from the station Progress (K = 1.4÷6.1. It was noted that values of the coefficient of enrichment K of these ions decreases as someone moves from a shore to inland. Estimation of

  3. Uplift and tilting of the Shackleton Range in East Antarctica driven by glacial erosion and normal faulting.

    OpenAIRE

    Paxman, Guy J.G.; Jamieson, Stewart S.Rr; Ferraccioli, Fausto; Bentley, Michael J.; Forsberg, Rene; Ross, Neil; Watts, Anthony B.; Corr, Hugh F. J.; Jordan, Tom A.

    2017-01-01

    Unravelling the long-term evolution of the subglacial landscape of Antarctica is vital for understanding past ice sheet dynamics and stability, particularly in marine-based sectors of the ice sheet. Here we model the evolution of the bedrock topography beneath the Recovery catchment, a sector of the East Antarctic Ice Sheet characterized by fast-flowing ice streams that occupy overdeepened subglacial troughs. We use 3-D flexural models to quantify the effect of erosional unloading and mechani...

  4. Deglaciation records of 17O-excess in East Antarctica: reliable reconstruction of oceanic normalized relative humidity from coastal sites

    Directory of Open Access Journals (Sweden)

    B. Stenni

    2012-01-01

    Full Text Available We measured δ17O and δ18O in two Antarctic ice cores at EPICA Dome C (EDC and TALDICE (TD, respectively, and computed 17O-excess with respect to VSMOW. The comparison of our 17O-excess data with the previous record obtained at Vostok (Landais et al., 2008a revealed differences up to 35 ppm in 17O-excess mean level and evolution for the three sites. Our data show that the large increase depicted at Vostok (20 ppm during the last deglaciation is a regional and not a general pattern in the temporal distribution of 17O-excess in East Antarctica. The EDC data display an increase of 12 ppm, whereas the TD data show no significant variation from the Last Glacial Maximum (LGM to the Early Holocene (EH. A Lagrangian moisture source diagnostic revealed very different source regions for Vostok and EDC compared to TD. These findings combined with the results of a sensitivity analysis, using a Rayleigh-type isotopic model, suggest that normalized relative humidity (RHn at the oceanic source region (OSR is a determining factor for the spatial differences of 17O-excess in East Antarctica. However, 17O-excess in remote sites of continental Antarctica (e.g. Vostok may be highly sensitive to local effects. Hence, we consider 17O-excess in coastal East Antarctic ice cores (TD to be more reliable as a proxy for RHn at the OSR.

  5. Seismic Stratigraphy Of The Sabrina Coast Shelf, East Antarctica: History Of Late Paleogene To Early Neogene Glacial Evolution

    Science.gov (United States)

    Montelli, A.; Gulick, S. P. S.; Frederick, B. C.; Blankenship, D. D.; Leventer, A.; Shevenell, A.; Domack, E. W.

    2015-12-01

    Sedimentary architecture of the Sabrina Coast (SC) shelf, East Antarctica is studied for the first time using 754 km of high (up to 3 m) vertical resolution multichannel seismic data and four piston cores acquired on board of RVIB Palmer in 2014. We interpret the sedimentary record of early glacial SC shelf stratigraphy based on analysis of seismic facies and morphological features. We identify at least nine erosional surfaces that indicate advances of the Totten Glacier - Moscow University Ice Shelf system, part of the East Antarctic Ice Sheet (EAIS), to the SC shelf. The most prominent features include two series of undulating, channelized erosional surfaces truncating strata below and showing highly irregular morphology with elevation amplitudes of up to ~120 m and widths of individual undulations of up to ~10 km. These surfaces are located stratigraphically above a core bearing IRD and assigned biostratigraphically to the Late Eocene and below a regional erosional surface of Late Miocene age. Our major results show that: (1) Oligocene-early Miocene evolution of EAIS consists of low-frequency, high-amplitude glacial expansions followed by long periods of ice-distal to open marine conditions; (2) the presence of grounded EAIS expansions on shelf is expressed in a series of deep, hummocky undulations and first Antarctic sedimentary tunnel valley system, suggestive of presence of subglacial meltwater and hence, a polythermal glacial regime; (3) at least nine erosional unconformities representing major ice advances have been found on the inner shelf; (4) the most intensive polythermal glaciations have occurred in late Eocene-early Oligocene; (5) no evidence of focused paleo- ice stream(s) draining Aurora Basin Complex prior to the middle Miocene was found in the study area.

  6. Age-related environmental gradients influence invertebrate distribution in the Prince Charles Mountains, East Antarctica

    Science.gov (United States)

    White, Duanne; Clarke, Laurence; McKay, Alan; Cooper, Alan; Stevens, Mark I.

    2016-01-01

    The potential impact of environmental change on terrestrial Antarctic ecosystems can be explored by inspecting biodiversity patterns across large-scale gradients. Unfortunately, morphology-based surveys of Antarctic invertebrates are time-consuming and limited by the cryptic nature of many taxa. We used biodiversity information derived from high-throughput sequencing (HTS) to elucidate the relationship between soil properties and invertebrate biodiversity in the Prince Charles Mountains, East Antarctica. Across 136 analysed soil samples collected from Mount Menzies, Mawson Escarpment and Lake Terrasovoje, we found invertebrate distribution in the Prince Charles Mountains significantly influenced by soil salinity and/or sulfur content. Phyla Tardigrada and Arachnida occurred predominantly in low-salinity substrates with abundant nutrients, whereas Bdelloidea (Rotifera) and Chromadorea (Nematoda) were more common in highly saline substrates. A significant correlation between invertebrate occurrence, soil salinity and time since deglaciation indicates that terrain age indirectly influences Antarctic terrestrial biodiversity, with more recently deglaciated areas supporting greater diversity. Our study demonstrates the value of HTS metabarcoding to investigate environmental constraints on inconspicuous soil biodiversity across large spatial scales. PMID:28083092

  7. 1-D-ice flow modelling at EPICA Dome C and Dome Fuji, East Antarctica

    Directory of Open Access Journals (Sweden)

    F. Parrenin

    2007-06-01

    Full Text Available One-dimensional (1-D ice flow models are used to construct the age scales at the Dome C and Dome Fuji drilling sites (East Antarctica. The poorly constrained glaciological parameters at each site are recovered by fitting independent age markers identified within each core. We reconstruct past accumulation rates, that are larger than those modelled using the classical vapour saturation pressure relationship during glacial periods by up to a factor 1.5. During the Early Holocene, changes in reconstructed accumulation are not linearly related to changes in ice isotopic composition. A simple model of past elevation changes is developed and shows an amplitude variation of 110–120 m at both sites. We suggest that there is basal melting at Dome C (0.56±0.19 mm/yr. The reconstructed velocity profile is highly non-linear at both sites, which suggests complex ice flow effects. This induces a non-linear thinning function in both drilling sites, which is also characterized by bumps corresponding to variations in ice thickness with time.

  8. Bacterial succession in Antarctic soils of two glacier forefields on Larsemann Hills, East Antarctica.

    Science.gov (United States)

    Bajerski, Felizitas; Wagner, Dirk

    2013-07-01

    Antarctic glacier forefields are extreme environments and pioneer sites for ecological succession. Increasing temperatures due to global warming lead to enhanced deglaciation processes in cold-affected habitats, and new terrain is becoming exposed to soil formation and microbial colonization. However, only little is known about the impact of environmental changes on microbial communities and how they develop in connection to shifting habitat characteristics. In this study, using a combination of molecular and geochemical analysis, we determine the structure and development of bacterial communities depending on soil parameters in two different glacier forefields on Larsemann Hills, East Antarctica. Our results demonstrate that deglaciation-dependent habitat formation, resulting in a gradient in soil moisture, pH and conductivity, leads to an orderly bacterial succession for some groups, for example Cyanobacteria, Bacteroidetes and Deltaproteobacteria in a transect representing 'classical' glacier forefields. A variable bacterial distribution and different composed communities were revealed according to soil heterogeneity in a slightly 'matured' glacier forefield transect, where Gemmatimonadetes, Flavobacteria, Gamma- and Deltaproteobacteria occur depending on water availability and soil depth. Actinobacteria are dominant in both sites with dominance connected to certain trace elements in the glacier forefields. © 2013 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

  9. Airborne gravity over Lake Vostok and adjacent highlands of East Antarctica

    Science.gov (United States)

    Holt, John W.; Richter, Thomas G.; Kempf, Scott D.; Morse, David L.; Blankenship, Donald D.

    2006-11-01

    Lake Vostok and a 1200 km transect were the targets of aerogeophysical surveys in East Antarctica during the austral summer of 2000/2001. The measurement of gravity anomalies for geologic studies was the primary goal. A total of 24,459 line-km of data were acquired. Favorable weather, aircraft navigation, and instrument performance contributed to excellent data quality. Multiple carrier-phase GPS solutions to determine aircraft-induced accelerations were available for each flight. Raw gravity and GPS position solutions were initially filtered to compensate for hardware filtering within the gravity meter. Filtering of remaining high-frequency noise was accomplished with a spatial, moving average smoother. Due to upward continuation effects imposed by the ice cover, the theoretically estimated minimum resolvable gravity feature size for the Lake Vostok survey is 8 km, consistent with an analysis of power spectra comparing the gravity signal to noise calculated from geographically repeated lines. Comparison of gravity results with subice topography indicates that the gravity data are sensitive to real features including the existence of major crustal structures. Repeated lines and crossovers were analyzed to estimate uncertainties for the Lake Vostok data set, with both of these repeatability measures indicating relative accuracy in the 2 mGal range for the unleveled data and 1 mGal after leveling.

  10. Polyphase Neoproterozoic orogenesis within the east Africa- Antarctica orogenic belt in central and northern Madagascar

    Science.gov (United States)

    Key, R.M.; Pitfield, P.E.J.; Thomas, Ronald J.; Goodenough, K.M.; Waele, D.; Schofield, D.I.; Bauer, W.; Horstwood, M.S.A.; Styles, M.T.; Conrad, J.; Encarnacion, J.; Lidke, D.J.; O'connor, E. A.; Potter, C.; Smith, R.A.; Walsh, G.J.; Ralison, A.V.; Randriamananjara, T.; Rafahatelo, J.-M.; Rabarimanana, M.

    2011-01-01

    Our recent geological survey of the basement of central and northern Madagascar allowed us to re-evaluate the evolution of this part of the East Africa-Antarctica Orogen (EAAO). Five crustal domains are recognized, characterized by distinctive lithologies and histories of sedimentation, magmatism, deformation and metamorphism, and separated by tectonic and/or unconformable contacts. Four consist largely of Archaean metamorphic rocks (Antongil, Masora and Antananarivo Cratons, Tsaratanana Complex). The fifth (Bemarivo Belt) comprises Proterozoic meta-igneous rocks. The older rocks were intruded by plutonic suites at c. 1000 Ma, 820-760 Ma, 630-595 Ma and 560-520 Ma. The evolution of the four Archaean domains and their boundaries remains contentious, with two end-member interpretations evaluated: (1) all five crustal domains are separate tectonic elements, juxtaposed along Neoproterozoic sutures and (2) the four Archaean domains are segments of an older Archaean craton, which was sutured against the Bemarivo Belt in the Neoproterozoic. Rodinia fragmented during the early Neoproterozoic with intracratonic rifts that sometimes developed into oceanic basins. Subsequent Mid- Neoproterozoic collision of smaller cratonic blocks was followed by renewed extension and magmatism. The global 'Terminal Pan-African' event (560-490 Ma) finally stitched together the Mid-Neoproterozoic cratons to form Gondwana. ?? The Geological Society of London 2011.

  11. Ground-based measurements of spatial and temporal variability of snow accumulation in East Antarctica

    Science.gov (United States)

    Eisen, Olaf; Frezzotti, Massimo; Genthon, Christophe; Isaksson, Elisabeth; Magand, Olivier; van den Broeke, Michiel R.; Dixon, Daniel A.; Ekaykin, Alexey; Holmlund, Per; Kameda, Takao; KarlöF, Lars; Kaspari, Susan; Lipenkov, Vladimir Y.; Oerter, Hans; Takahashi, Shuhei; Vaughan, David G.

    2008-06-01

    The East Antarctic Ice Sheet is the largest, highest, coldest, driest, and windiest ice sheet on Earth. Understanding of the surface mass balance (SMB) of Antarctica is necessary to determine the present state of the ice sheet, to make predictions of its potential contribution to sea level rise, and to determine its past history for paleoclimatic reconstructions. However, SMB values are poorly known because of logistic constraints in extreme polar environments, and they represent one of the biggest challenges of Antarctic science. Snow accumulation is the most important parameter for the SMB of ice sheets. SMB varies on a number of scales, from small-scale features (sastrugi) to ice-sheet-scale SMB patterns determined mainly by temperature, elevation, distance from the coast, and wind-driven processes. In situ measurements of SMB are performed at single points by stakes, ultrasonic sounders, snow pits, and firn and ice cores and laterally by continuous measurements using ground-penetrating radar. SMB for large regions can only be achieved practically by using remote sensing and/or numerical climate modeling. However, these techniques rely on ground truthing to improve the resolution and accuracy. The separation of spatial and temporal variations of SMB in transient regimes is necessary for accurate interpretation of ice core records. In this review we provide an overview of the various measurement techniques, related difficulties, and limitations of data interpretation; describe spatial characteristics of East Antarctic SMB and issues related to the spatial and temporal representativity of measurements; and provide recommendations on how to perform in situ measurements.

  12. Location of a new ice core site at Talos Dome (East Antarctica

    Directory of Open Access Journals (Sweden)

    I. Tabacco

    2006-06-01

    Full Text Available In the frame of glaciology and palaeoclimate research, Talos Dome (72°48lS; 159°06lE, an ice dome on the East Antarctic plateau, represents the new selected site for a new deep ice core drilling. The increasing interest in this region is due to the fact that the ice accumulation is higher here than in other domes in East Antarctica. A new deep drilling in this site could give important information about the climate changes near the coast. Previous papers showed that the dome summit is situated above a sloped bedrock. A new position on a relatively flat bedrock 5-6 km far from here in the SE direction was defined as a possible new ice core site for an European (Italy, France, Swiss and United Kingdom drilling project named as TALDICE (TALos Dome Ice Core Project. This point, named as ID1 (159°11l00mE; 72°49l40mS, became the centre of the Radio Echo Sounding (RES flight plan during the 2003 Italian Antarctic expedition, with the aim of confirming the new drilling site choice. In this paper 2001 and 2003 RES data sets have been used to draw a better resolution of ice thickness, bottom morphology and internal layering of a restricted area around the dome. Based on the final results, point ID1 has been confirmed as the new coring site. Finally, the preliminary operations about the installation of the summer ice core camp (TALDICE at ID1 site carried out during the XX Italian Antarctic expedition (November 2004-December 2005 are briefly described.

  13. Hypolithic Biocrust in the Larsemann Hills of East Antarctica: Spatial Patterns, Organic Matter Stabilization, Comparison with Endolithic Systems

    Science.gov (United States)

    Mergelov, Nikita; Dolgikh, Andrey; Shorkunov, Ilya; Zazovskaya, Elya; Shishkov, Vasily; Pochikalov, Alexander

    2017-04-01

    The survey conducted in the Larsemann Hills oasis of East Antarctica (69°24'S, 76°14'E) revealed that hypolithic and endolithic bio-abiotic systems occupy from 20 to 60% of the wet valleys floors and slopes area. As in many other parts of Antarctica a significant portion of organic matter in Larsemann Hills is produced in cryptic niches inside the fissure network of hard rocks or under the stone pavements on loose sediments. The dominant autotrophic components of such ecosystems are cyanobacteria and green algae, mainly in the form of biofilms. However moss dominated communities could form distinct patterns within hypolithic biocrust. The spatial distribution of various types of hypolithic biocrusts, its thickness, moisture content, carbon and nitrogen content/stocks, as well as C/N ratios were studied at a detailed scale at several key sites along the grid of 10x10 m with a step of 1 m (121 sampling points each). The data received are evident that microbial and cryptogamic photoautotrophs activity in hidden habitats under the stone pavements could lead to the substantial organic matter accumulation in extreme environment of East Antarctica - up to 5% of C and 0.4% of N. However the radiocarbon data indicate that in many cases the values of fraction modern (F14C) exceed "1" which means that organic matter in hypolithic biocrust is not preserved in a long-term period. This contrasts with 14C "ages" of endolithic systems on surrounding slopes of the valley exceeding 500 and sometimes 1000 yr BP. We found that once hypolithic organogenous material is buried under sand and gravel 2-5 cm deeper than common hypolithic biocrust it could preserve for a dramatically longer periods and have the 14C "age" up to 1100 yr BP. As evidenced by optical and scanning electron microscopy with EDX this old organogenous material of hypolithic origin still retains clear filamentous structure of cyanobacteria biofilm as well as remnants of EPS stabilized mainly by amorphous Si and Al

  14. Archean, Paleoproterozoic and Mesoproterozoic Crust of Central East Antarctica: New Insights on Subglacial Geology from Proxy Geologic Materials

    Science.gov (United States)

    Goodge, J. W.; Fanning, C. M.; Vervoort, J. D.; Fisher, C. M.; Nissen, C. I.

    2013-12-01

    Uncovering the ice-covered geology of East Antarctica is critical for understanding its ancient crustal history, its role in supercontinent formation, and its relationship to development of the Cenozoic ice cap. Multiple approaches--including detrital-mineral provenance study, analysis of glacial clasts, airborne and passive geophysics, and future sub-ice drilling--are rapidly improving our view of the remote continental interior. Proxy geologic materials such as detrital zircons and glacial clasts provide indirect means to sample the ice-covered crust, although spatial-geographic resolution is poor; geophysical data are spatially accurate yet limited by uncertainty in geologic significance. In addition to U-Pb zircon ages of ~3.1, 2.5 and 1.7 Ga from Nimrod Group outcrop, detrital-zircon provenance and glacial clast studies from the central Transantarctic Mountains show that central East Antarctica was formed by a series of episodic magmatic events at 2.01, 1.88-1.79, 1.57, 1.48-1.43, and 1.22-1.06 Ga. Zircon Hf and O isotopic compositions from a suite of granitoid clasts collected from glacial catchments draining central East Antarctica have variable compositions that indicate both juvenile, mantle-derived melts and those involving older crustal sources. None of these igneous clast ages are known from limited Antarctic outcrop in the region. Detrital zircon ages in Neoproterozoic rift-margin strata confirm important populations of 1.88-1.72, 1.64-1.36, and 1.28-1.04 Ga, strengthening a case for episodic magmatic growth of East Antarctic crust. After a juvenile Archean magmatic origin, central East Antarctica was consolidated by further crustal assembly at ~1.9 (Nuna time), ~1.7 (Mawson), and ~1.2 Ga (Rodinia), as indicated by monazite U-Pb ages from metamorphic leucogneiss clasts. Monazite ages record suspected but previously undocumented Proterozoic tectonometamorphic events in central East Antarctica, overprinted by younger Neoproterozoic metamorphism. Together

  15. Ice Velocity Measurement in East Antarctica from 1960s to 1980s Based on Argon and Landsat Imagery

    Science.gov (United States)

    Li, R.; Ma, X.; Cheng, Y.; Ye, W.; Guo, S.; Tang, G.; Wang, Z.; Gao, T.; Huang, Y.; Li, X.; Qiao, G.; Tian, Y.; Feng, T.; Tong, X.

    2017-09-01

    Ice flow velocity is a vital parameter for estimating the ice mass balance of glaciers in Antarctica. Especially long time serial observation of the surface velocity is of great significance to assessing the relationship between Antarctic ice materials and global climate change. However, the existing research on Antarctic ice velocity based on remote sensing data since 1970s due to the harsh climate in Antarctica. This paper presents an ice flow velocity estimating method includes image pre-processing, geometric model reconstruction, image ortho-rectification and feature matching by using ARGON images token in 1963 and Landsat images collected form 1973 to 1989.Considering the temporal-spatial distributions of ARGON images and Landsat images in Antarctica, two different methods respectively based on ortho-photos pair and Non-Ortho photos are adopted in this paper. More specifically, when there exist two stereo pairs taken in different time in the glacier region, after being ortho-rectified, the stereo pairs can be used to calculate ice flow velocity based on feature matching method. Otherwise, a parallax decomposition method that separates the effect of the terrain relief from the ice flow motion is applied when there only exists one stereo pair with a certain time interval. With this method, glacier surface velocity is available in the glacier region lacked enough stereo pairs. The methods mentioned above for estimating ice flow velocity are applied in Totten, Amery and Fimbul, etc. in eastern Antarctica. Furthermore, a 1960-80s ice flow speed map in the main glaciers of East Antarctica is produced for the first time.

  16. Crustal heat production and estimate of terrestrial heat flow in central East Antarctica, with implications for thermal input to the East Antarctic ice sheet

    Directory of Open Access Journals (Sweden)

    J. W. Goodge

    2018-02-01

    Full Text Available Terrestrial heat flow is a critical first-order factor governing the thermal condition and, therefore, mechanical stability of Antarctic ice sheets, yet heat flow across Antarctica is poorly known. Previous estimates of terrestrial heat flow in East Antarctica come from inversion of seismic and magnetic geophysical data, by modeling temperature profiles in ice boreholes, and by calculation from heat production values reported for exposed bedrock. Although accurate estimates of surface heat flow are important as an input parameter for ice-sheet growth and stability models, there are no direct measurements of terrestrial heat flow in East Antarctica coupled to either subglacial sediment or bedrock. As has been done with bedrock exposed along coastal margins and in rare inland outcrops, valuable estimates of heat flow in central East Antarctica can be extrapolated from heat production determined by the geochemical composition of glacial rock clasts eroded from the continental interior. In this study, U, Th, and K concentrations in a suite of Proterozoic (1.2–2.0 Ga granitoids sourced within the Byrd and Nimrod glacial drainages of central East Antarctica indicate average upper crustal heat production (Ho of about 2.6  ±  1.9 µW m−3. Assuming typical mantle and lower crustal heat flux for stable continental shields, and a length scale for the distribution of heat production in the upper crust, the heat production values determined for individual samples yield estimates of surface heat flow (qo ranging from 33 to 84 mW m−2 and an average of 48.0  ±  13.6 mW m−2. Estimates of heat production obtained for this suite of glacially sourced granitoids therefore indicate that the interior of the East Antarctic ice sheet is underlain in part by Proterozoic continental lithosphere with an average surface heat flow, providing constraints on both geodynamic history and ice-sheet stability. The ages and geothermal

  17. A new approach to estimate ice dynamic rates using satellite observations in East Antarctica

    Science.gov (United States)

    Kallenberg, Bianca; Tregoning, Paul; Fabian Hoffmann, Janosch; Hawkins, Rhys; Purcell, Anthony; Allgeyer, Sébastien

    2017-05-01

    Mass balance changes of the Antarctic ice sheet are of significant interest due to its sensitivity to climatic changes and its contribution to changes in global sea level. While regional climate models successfully estimate mass input due to snowfall, it remains difficult to estimate the amount of mass loss due to ice dynamic processes. It has often been assumed that changes in ice dynamic rates only need to be considered when assessing long-term ice sheet mass balance; however, 2 decades of satellite altimetry observations reveal that the Antarctic ice sheet changes unexpectedly and much more dynamically than previously expected. Despite available estimates on ice dynamic rates obtained from radar altimetry, information about ice sheet changes due to changes in the ice dynamics are still limited, especially in East Antarctica. Without understanding ice dynamic rates, it is not possible to properly assess changes in ice sheet mass balance and surface elevation or to develop ice sheet models. In this study we investigate the possibility of estimating ice sheet changes due to ice dynamic rates by removing modelled rates of surface mass balance, firn compaction, and bedrock uplift from satellite altimetry and gravity observations. With similar rates of ice discharge acquired from two different satellite missions we show that it is possible to obtain an approximation of the rate of change due to ice dynamics by combining altimetry and gravity observations. Thus, surface elevation changes due to surface mass balance, firn compaction, and ice dynamic rates can be modelled and correlated with observed elevation changes from satellite altimetry.

  18. Atmospheric trace elements in aerosols observed over the Southern Ocean and coastal East Antarctica

    Directory of Open Access Journals (Sweden)

    Guojie Xu

    2014-11-01

    Full Text Available Atmospheric aerosol samples were collected over the Southern Ocean (SO and coastal East Antarctica (CEA during the austral summer of 2010/11. Samples were analysed for trace elements, including Na, Mg, K, Al, Fe, Mn, Ni, Cd and Se, by inductively coupled plasma mass spectrometry (ICP-MS. The mean atmospheric concentrations over the SO were 1100 ng m−3 for Na, 190 ng m−3 for Mg, 150 ng m−3 for Al, 14 ng m−3 for Fe, 0.46 ng m−3 for Mn and 0.25 ng m−3 for Se. Over CEA, the mean concentrations were 990 ng m−3 for Na, 180 ng m−3 for Mg, 190 ng m−3 for Al, 26 ng m−3 for Fe, 0.70 ng m−3 for Mn and 0.29 ng m−3 for Se. Particle size distributions, enrichment factors (EFs and correlation analysis indicate that Na, Mg and K mainly came from the marine source, while Al, Fe and Mn were mainly from the crustal source, which also contributed to Mg and K over CEA. High EFs were associated with Ni, Cd and Se, suggesting likely contributions from mixed sources from the Antarctic continent, long-range transport, marine biogenic emissions and anthropogenic emissions. Sea-salt elements (Na, Mg, K were mainly accumulated in the coarse mode, and crustal elements (Al, Fe, Mn presented a bimodal size distribution pattern. Bioactive elements (Fe, Ni, Cd were enriched in the fine mode, especially with samples collected over the SO, possibly affecting biogeochemical cycles in this oceanic region.

  19. Oceanic circulation changes during early Pliocene marine ice-sheet instability in Wilkes Land, East Antarctica

    Science.gov (United States)

    Hansen, Melissa A.; Passchier, Sandra

    2017-06-01

    In the Southern Ocean, unconstrained Westerlies allow for intense mixing between deep waters and the atmosphere. How this system interacts with Antarctic ice sheets and the global ocean circulation is poorly understood due to a paucity of data. The poor abundance and preservation of foraminiferal carbonate in ice-proximal sediments is a major challenge in high-latitude paleoceanography. A new approach is to examine a sediment geochemical record of changing paleoproductivity and sediment redox environment that can be tied to changes in water mass properties. This study focuses on the paleoceanography of the George V Land margin between 4.7 and 4.3 Ma. This interval at the onset of the early Pliocene Climatic Optimum was characterized by the highest global sea surface temperatures and the lowest sea ice concentrations in East Antarctica in the past 5 million years. At IODP Site U1359, an abrupt increase in Mn/Al ratios 4.6 Ma indicates an episode of oxic bottom conditions resulting from enhanced wind-driven downwelling of Antarctic surface water. Above, extremely high concentrations of sedimentary barite (Ba excess >40,000 ppm) point to biogenic barite deposition, preservation, and concentration through enhanced upwelling of nutrient-rich Circumpolar Deep Water (CDW). Incursion of CDW onto the continental shelf affected ice discharge and resulted in a stable but reduced ice-sheet configuration over several glacial cycles. The geochemical results along with previous work on Site U1359 for the first time link paleoceanography and cryospheric change based on data from the same high-latitude site.

  20. A new approach to estimate ice dynamic rates using satellite observations in East Antarctica

    Directory of Open Access Journals (Sweden)

    B. Kallenberg

    2017-05-01

    Full Text Available Mass balance changes of the Antarctic ice sheet are of significant interest due to its sensitivity to climatic changes and its contribution to changes in global sea level. While regional climate models successfully estimate mass input due to snowfall, it remains difficult to estimate the amount of mass loss due to ice dynamic processes. It has often been assumed that changes in ice dynamic rates only need to be considered when assessing long-term ice sheet mass balance; however, 2 decades of satellite altimetry observations reveal that the Antarctic ice sheet changes unexpectedly and much more dynamically than previously expected. Despite available estimates on ice dynamic rates obtained from radar altimetry, information about ice sheet changes due to changes in the ice dynamics are still limited, especially in East Antarctica. Without understanding ice dynamic rates, it is not possible to properly assess changes in ice sheet mass balance and surface elevation or to develop ice sheet models. In this study we investigate the possibility of estimating ice sheet changes due to ice dynamic rates by removing modelled rates of surface mass balance, firn compaction, and bedrock uplift from satellite altimetry and gravity observations. With similar rates of ice discharge acquired from two different satellite missions we show that it is possible to obtain an approximation of the rate of change due to ice dynamics by combining altimetry and gravity observations. Thus, surface elevation changes due to surface mass balance, firn compaction, and ice dynamic rates can be modelled and correlated with observed elevation changes from satellite altimetry.

  1. Holocene secular variations in dust transport to east Antarctica (Vostok and Dome-C): a response to solar forcing?

    Science.gov (United States)

    Delmonte, B.; Petit, J.-R.; Krinner, G.; Maggi, V.; Raisbeck, G.; Yiou, F.; Jouzel, J.; Lipenkov, V.

    2003-04-01

    Two Holocene sections from EPICA-Dome C and Vostok ice cores have been analysed at high temporal resolution (1 sample per 40 and 50 yrs respectively) for continental dust concentration and size distribution. A new Holocene record of the cosmogenic isotope 10Be has also been obtained from the Vostok ice core, and the chronologies of all three records are tightly linked by stratigraphic markers. Both dust records of size distribution, good proxy for the efficiency of atmospheric dust transport to the Antarctic plateau, clearly show secular oscillations in the 200-year band that are opposite in phase between the two sites. This suggests a secular variability in the efficiency of dust advection to East Antarctica and a regional character of dust transport. The combined dust record and the 10Be record appear highly coherent in the 200-year band, but the atmospheric response to solar forcing seems lagged by about 50 years. We speculate an amplification by the Southern Ocean: sea ice can interact with atmospheric circulation both responding to atmospheric conditions and modifying the cyclonic behaviour and sea ice itself. We performed a sensitivity test with the LMDz atmosphere-only general circulation model with present-day and modified sea-surface conditions, and the model response evidence that Antarctic ocean surface temperature anomalies propagate vertically to high levels in the troposphere, likely affecting dust advection. Such an amplification of solar frequencies by the Southern Ocean can allow a combination of them and originate the millennial-scale oscillations also present in EPICA dust record.

  2. Aerial surveys for pack-ice seals along the Ingrid Christensen and Princess Astrid Coasts, East Antarctica

    OpenAIRE

    R.S. Kumar; J.A. Johnson

    2014-01-01

    We conducted aerial surveys in the austral summer of 2009-2010 to count and record the spatial distribution patterns of pack-ice seals hauled-out along the Ingrid Christensen and Princess Astrid coast of East Antarctica. A total of 3,601 hauled-out seals were counted from six aerial surveys totalling a length of approx. 1,200km, with each survey lasting about two hours. Weddell Seal Leptonychotes weddellii was the most commonly sighted species in both the areas surveyed (98.2%), and had an en...

  3. Nitrate records of a shallow ice core from East Antarctica: Atmospheric processes, preservation and climatic implications

    Digital Repository Service at National Institute of Oceanography (India)

    Laluraj, C.M.; Thamban, M.; Naik, S.S.; Redkar, B.L.; Chaturvedi, A.; Ravindra, R.

    and its comparison with 10Be record from a core collected from South Pole suggest that a reduction in solar activity influenced the NO sub(3) sup(-) accumulation in Antarctica through enhanced production of odd nitrogen species...

  4. Trace elements and Pb isotope records in Dome C (East Antarctica ice over the past 800,000 years

    Directory of Open Access Journals (Sweden)

    Hong S.

    2013-04-01

    Full Text Available Trace elements (V, Cr, Mn, Fe, Co, Cu, Zn, As, Rb, Sr, Mo, Cd, Sb, Ba, Tl, Pb, Bi, Th and U and Pb isotopic compositions from the EPICA (European Project for Ice Coring in Antarctica Dome C ice core have been determined using inductively coupled plasma sector field mass spectrometry (ICP-SFMS and thermal ionization mass spectrometry (TIMS, covering the period from ~533 kyr BP to ~800 kyr BP, respectively. Our data have enabled us to extend the previous EDC records of trace elements and Pb isotopes from the Holocene back to the Marine Isotopic Stage 20.2, ~800 kyr BP. We here discuss the EDC records of Ba, Rb, Mo, Sb, Cd, Tl, Bi and Pb isotopes. Crustal elements such as Ba and Rb show well defined variations in concentrations in relation to climatic conditions with lower values during the interglacial periods and much higher values during the coldest periods of the last eight climatic cycles. Volcanogenic Cd, Tl and Bi show a less pronounced relationship between concentrations and climatic conditions. The isotopic signatures of Pb suggest that changes in the provenance of dust reaching the East Antarctic Plateau from Potential Source Areas occurred during the interglacial periods before the MBE. Our data suggest that the main factors affecting deposition fluxes and sources of natural trace elements over Antarctica are most likely linked to a progressive coupling of the climates of Antarctica and lower latitudes over the past 800 kyr.

  5. Pan-ice-sheet glacier terminus change in East Antarctica reveals sensitivity of Wilkes Land to sea-ice changes.

    Science.gov (United States)

    Miles, Bertie W J; Stokes, Chris R; Jamieson, Stewart S R

    2016-05-01

    The dynamics of ocean-terminating outlet glaciers are an important component of ice-sheet mass balance. Using satellite imagery for the past 40 years, we compile an approximately decadal record of outlet-glacier terminus position change around the entire East Antarctic Ice Sheet (EAIS) marine margin. We find that most outlet glaciers retreated during the period 1974-1990, before switching to advance in every drainage basin during the two most recent periods, 1990-2000 and 2000-2012. The only exception to this trend was in Wilkes Land, where the majority of glaciers (74%) retreated between 2000 and 2012. We hypothesize that this anomalous retreat is linked to a reduction in sea ice and associated impacts on ocean stratification, which increases the incursion of warm deep water toward glacier termini. Because Wilkes Land overlies a large marine basin, it raises the possibility of a future sea level contribution from this sector of East Antarctica.

  6. Pan–ice-sheet glacier terminus change in East Antarctica reveals sensitivity of Wilkes Land to sea-ice changes

    Science.gov (United States)

    Miles, Bertie W. J.; Stokes, Chris R.; Jamieson, Stewart S. R.

    2016-01-01

    The dynamics of ocean-terminating outlet glaciers are an important component of ice-sheet mass balance. Using satellite imagery for the past 40 years, we compile an approximately decadal record of outlet-glacier terminus position change around the entire East Antarctic Ice Sheet (EAIS) marine margin. We find that most outlet glaciers retreated during the period 1974–1990, before switching to advance in every drainage basin during the two most recent periods, 1990–2000 and 2000–2012. The only exception to this trend was in Wilkes Land, where the majority of glaciers (74%) retreated between 2000 and 2012. We hypothesize that this anomalous retreat is linked to a reduction in sea ice and associated impacts on ocean stratification, which increases the incursion of warm deep water toward glacier termini. Because Wilkes Land overlies a large marine basin, it raises the possibility of a future sea level contribution from this sector of East Antarctica. PMID:27386519

  7. A 300 000 year isotopic record from the TALDICE ice core (East Antarctica)

    Science.gov (United States)

    Stenni, B.

    2009-04-01

    The TALos Dome Ice CorE (TALDICE) project retrieved an ice core from a peripheral dome of East Antarctica. This international project aimed at drilling an ice core reaching back in time the past two climatic cycles (about 250,000 years). Talos Dome (72˚ 49' S, 159˚ 11' E; 2315 m; 80 kg m-2 yr-1; -41˚ C) is located at about 290 km from the Southern Ocean, 250 km from the Ross Sea, 275 km from the Zucchelli Station (Terra Nova Bay). Backtrajectory analyses suggest that Talos Dome is mainly influenced by air masses arriving both from the Pacific (Ross Sea) and Indian Ocean sectors. In December 2007 the drilling team reached the depth of 1619.2 m. A preliminary dating based on an ice flow model and an inverse method suggests for the upper 1560 m an age of about 300 000 years BP. This near coastal site allows a higher climate resolution study for the Holocene compared to the ones obtained from the more inland drilling sites. The paleotemperature reconstructions from Antarctic ice cores relies mainly on ^D and ^18O records. The main factors controlling the observed distribution of their surface values in Antarctic snow are mainly related to the condensation temperature and the origin of moisture. Measuring both isotopes in the ice allow the determination of the deuterium excess (d=^D-8*^18O) which is mainly controlled by the climatic conditions in the moisture source regions. The ice cores have been cut in the cold laboratory of the Alfred Wegener Institut at Bremerhaven. ^18O and ^D measurements have been performed on a continuous basis of 100 cm ("bag samples") and 10 cm (detailed samples) in Italy and France. The full ^18O record obtained from the bag samples is presented here along with a preliminary deuterium excess data set. The long term climate variability is in good agreement with the EPICA Dome C ice core with the exception of trends during interglacial periods (present and past interglacial). While most of the Holocene record shows a good agreement

  8. Imprints of a Pan-African transpressional orogen superimposed on an inferred Grenvillian accretionary belt in central East Antarctica

    Science.gov (United States)

    Ferraccioli, Fausto; Seddon, Samuel; Finn, Carol; Bell, Robin; Wu, Guochao; Jordan, Tom

    2017-04-01

    The Gamburtsev Subglacial Mountains in interior East Antarctica are underlain by 50-60 km thick crust imaged by gravity and seismic models (Ferraccioli et al., 2011; An et al., 2015). In contrast, the composite Archean to Mesoproterozoic Mawson craton that occupies the Wilkes and Terre Adelie sector of East Antarctica typically features only 40-45 km thick crust (Aitken et al., 2014). Over 200 km thick and seismically fast lithosphere underlies the Gamburtsev Province, as typically observed over Precambrian lithosphere that has not been substantially reworked during Phanerozoic subduction or collision. Satellite and airborne magnetic data indicate that the Gamburtev Province is sandwiched in between distinct Precambrian lithospheric blocks including the Ruker, Princess Elizabeth Land, Vostok, Nimrod (Goodge and Finn, 2010), South Pole and Recovery provinces. Ferraccioli et al., (2011) proposed that a segment of a stalled orogen (i.e. an orogen where widespread orogenic collapse and root delamination has not occurred) is preserved in the Gamburtsev Province and further hypothesised that its origin relates to widespread accretionary and subsequent collisional events at ca 1 Ga, linked to the assembly of the Rodinia supercontinent. However, recent passive seismic interpretations (An et al., 2015) indicate that crustal thickening may relate instead to Pan-African age assembly of Greater India, East Antarctica and Australia within Gondwana (at ca 550 Ma). Here we interpret a set of enhanced magnetic and gravity images, depth to magnetic and gravity sources and preliminary 2D and 3D forward and inverse models to characterise in detail the crustal architecture of the Gamburtsev Province. Enhanced aeromagnetic images reveal a system of subglacial faults that segment the Gamburtsev Province into three distinct geophysical domains, the northern, central and southern domains. Apparent offsets in high-frequency magnetic anomalies within the central domain are interpreted here

  9. Growth, Transport, And/or Breakdown of Accessory Minerals in Migmatites from the Larsemann Hills, East Antarctica

    Science.gov (United States)

    Matthews, J. A.; Kelly, N. M.

    2010-12-01

    The extraction of melts from the lower crust and their subsequent emplacement at higher structural levels is an important differentiation mechanism that leads to the transfer of major and trace elements, volatiles and heat through the crust. Residual migmatites and granulites exposed at the Earth’s surface represent former melt-bearing crust and preserve evidence for melt transport on the micro- and meso-scale. The study of accessory phases, in particular their stabilities in melt-bearing systems and interactions with major minerals, is key to understanding the fluxes of trace and heat-producing elements during crustal anatexis. The Larsemann Hills of Prydz Bay, east Antarctica provide excellent 2-D exposure of granulite facies (c. 7 kbar and 800 °C) metasedimentary rocks and leucognesisses that preserve evidence for in situ partial melting, melt mobilization and connectivity. Leucosome found here contains K-feldspar, quartz, plagioclase, and minor garnet and biotite. Domains of residuum include: a) garnet (with aligned acicular sillimanite inclusions)-cordierite-spinel-ilmenite melanosome, the inferred assemblage remaining after melting and the extraction of some or all of the melt fraction; and b) coarse-grained garnet-sillimanite-cordierite ± biotite selvage zones that formed during melt-wall rock interaction. Petrographic analysis of melanosome, selvage, and leucosome domains has characterized mineral assemblages, structural fabrics and/or reaction textures that reflect the process of melt generation and in some cases reaction between residuum and crystallizing melts. In particular, focus on the textural context of accessory phases (zircon, monazite, apatite) has found that these phases occur as inclusions in and along grain boundaries of major minerals (e.g. garnet). This suggests that these accessory phases grew along with major minerals during partial melting. Detailed trace element characterization of major and accessory phases is being integrated with

  10. Climatology of clouds and precipitation over East Antarctica using ground-based remote sensing at the Princess Elizabeth station

    Science.gov (United States)

    Souverijns, Niels; Gossart, Alexandra; Gorodetskaya, Irina; Lhermitte, Stef; Van Tricht, Kristof; Mangold, Alexander; Laffineur, Quentin; Van Lipzig, Nicole

    2016-04-01

    The surface mass balance of the Antarctic ice sheet is highly dependent on the interaction between clouds and precipitation. Our understanding of these processes is challenged by the limited availability of observations over the area and problems in Antarctic climate simulations by state-of-the-art climate models. Improvements are needed in this field, as the Antarctic ice sheet is expected to become a dominant contributor to sea level rise in the 21st century. In 2010, an observational site was established at the Princess Elisabeth (PE) Antarctic station. PE is located in the escarpment area of Dronning Maud Land, East Antarctica (72°S, 23°E). The instruments consist of several ground-based remote sensing instruments: a ceilometer (measuring cloud-base height and vertical structure), a 24-GHz Micro Rain Radar (MRR; providing vertical profiles of radar effective reflectivity and Doppler velocity), and a pyrometer (measuring effective cloud base temperature). An automatic weather station provides info on boundary-layer meteorology (temperature, wind speed and direction, humidity, pressure), as well as broadband radiative fluxes and snow height changes. This set of instruments can be used to infer the role of clouds in the Antarctic climate system, their interaction with radiation and their impact on precipitation. Cloud and precipitation characteristics are derived from 5-year-long measurement series, which is unprecedented for the Antarctic region. Here, we present an overview of the cloud and precipitation climatology. Statistics on cloud occurrence are calculated on annual / seasonal basis and a distinction between liquid / mixed phase and ice clouds is made. One can discriminate between liquid-bearing and ice-only clouds by investigating the ceilometer attenuated backscatter, since liquid phase clouds have a much higher signal. Furthermore, by using pyrometer measurements, we are able to identify the range of temperatures at which liquid / ice clouds are

  11. Accumulation variability over a small area in east Dronning Maud Land, Antarctica, as determined from shallow firn cores and snow pits : some implications for ice-core records

    NARCIS (Netherlands)

    Karlof, Lars; Isaksson, Elisabeth; Winther, Jan-Gunnar; Gundestrup, Niels; Meijer, Harro A. J.; Mulvaney, Robert; Pourchet, Michel; Hofstede, Coen; Lappegard, Gaute; Pettersson, Rickard; Van den Broeke, Michiel; Van De Wal, Roderik S. W.

    2005-01-01

    We investigate and quantify the variability of snow accumulation rate around a medium-depth firn core (1160 m) drilled in east Dronning Maud Land, Antarctica (75 degrees 00'S, 15 degrees 00'E; 3470 m h.a.e. (ellipsoidal height)). We present accumulation data from five snow pits and five shallow (20

  12. Constraining the recent history of the perennially ice-covered Lake Bonney, East Antarctica using He, Kr and Xe concentrations

    Science.gov (United States)

    Hall, Chris M.; Castro, Maria Clara; Kenig, Fabien; Doran, Peter T.

    2017-07-01

    Lake Bonney is a perennially ice-covered lake in the McMurdo Dry Valleys (MDVs) that has long been studied in order to provide constraints on the paleoclimate of West Antarctica. The lake is divided into two lobes, West Lake Bonney (WLB) and East Lake Bonney (ELB) that are separated by a narrow ridge. The two lobes currently receive surface melt water during austral summers from glacier-fed ephemeral streams and this meltwater enters the lake via a narrow ring, or moat, of liquid water that forms around the lake during summer. The West Lobe also receives water from direct input of melt water from Taylor glacier and saline water from irregular subglacial discharge. Here, we combine previously published He data from Lake Bonney with new Kr and Xe concentration data to examine the signatures of water recharge via the seasonal moat and these data are used to constrain a model for He, Kr and Xe transport within both WLB and ELB over about the last 5000-6000 yrs. A detailed numerical simulation is presented that combines diffusive transport of noble gases within the stratified water column of Lake Bonney, along with ice ablation at the top of the ice cover, partitioning of noble gases between water and ice, plus exchange of noble gases between WLB and ELB. Results strongly suggest that open moats have only operated for about 2-3 centuries within the last millennium. These results are corroborated by the high concentration of He, especially within WLB, which points to a history of ice cover with no open moats operating for both lobes for at least about 5 millennia. In addition, the distribution of He, Kr and Xe suggest that a significant rise of the water level of Lake Bonney associated with a warmer period may have been interrupted by a roughly 4-5 century long cold period during which the moats were not large enough to allow air saturated water into the lake, with this cold period ending about one century ago. In addition, during this cold period, there is evidence for

  13. A low-angle brittle shear zone in the western Sør Rondane Mountains, Dronning Maud Land, East Antarctica - Implication for assembly of Gondwanaland

    Science.gov (United States)

    Tsukada, Kazuhiro; Yuhara, Masaki; Owada, Masaaki; Shimura, Toshiaki; Kamei, Atsushi; Kouchi, Yoshikazu; Yamamoto, Koshi

    2017-11-01

    The Sør Rondane Mountains (SRM), East Antarctica, lie within the late Neoproterozoic-early Paleozoic collision zone related to the formation of the Gondwana supercontinent. Many studies have been carried out in the eastern SRM, whereas fundamental questions on the western SRM remain unanswered, e.g. detail metamorphic history, age, kinematics of sheared rocks and others. This paper describes lithology and structure of the western SRM, and the tectonic implications of a low-angle brittle shear zone within this area, the Kanino-tume Shear Zone (KSZ), is discussed. Rocks of the study area are divided into units 1-3 based on their lithology and structural position. Units 1 and 2 are composed mainly of Neoproterozoic gneiss, and unit 3 consists mainly of ca. 1000-800 Ma metatonalite. Units 2 and 3, both separated by a mylonite/ultramylonite zone formed by dextral shearing (Main Shear Zone: MSZ), tectonically overlie unit 1 with the KSZ. The KSZ, showing top-to-the south sense of shear, cuts MSZ (∼ ca. 530 Ma) and is intruded by mafic dikes (ca. 560-440 Ma). Therefore, units 2 and 3, which had been juxtaposed by the dextral movement along the MSZ, rode together onto unit 1 along the KSZ by top-to-the southward movement at late Neoproterozoic-early Paleozoic time. The KSZ gives critical evidence for late Neoproterozoic-early Paleozoic movement in the SRM within the East African-Antarctic orogen.

  14. Infrasound observations at Syowa Station, East Antarctica: Implications for detecting the surface environmental variations in the polar regions

    Directory of Open Access Journals (Sweden)

    Yoshiaki Ishihara

    2015-03-01

    Full Text Available Characteristic infrasound waves observed at Antarctic stations demonstrate physical interaction involving environmental changes in the Antarctic continent and the surrounding oceans. A Chaparral-type infrasound sensor was installed at Syowa Station (SYO; 39°E, 69°S, East Antarctica, as one of the projects of the International Polar Year (IPY2007‒2008. Data continuously recorded during the three seasons in 2008–2010 clearly indicate a contamination of the background oceanic signals (microbaroms with peaks between 4 and 10 s observed during a whole season. The peak amplitudes of the microbaroms have relatively lower values during austral winters, caused by a larger amount of sea-ice extending around the Lützow-Holm Bay near SYO, with decreasing ocean wave loading effects. Microbaroms measurements are useful tool for characterizing ocean wave climate, complementing other oceanographic and geophysical data. A continuous monitoring by infrasound sensors in the Antarctic firmly contributes to the Comprehensive Nuclear-Test-Ban Treaty (CTBT in the southern high latitude, together with the Pan-Antarctic Observations System (PAntOS under the Scientific Committee on Antarctic Research (SCAR. Detailed measurements of the infrasound waves in Antarctica, consequently, could be a new proxy for monitoring regional environmental change as well as the temporal climate variations in the polar regions.

  15. Detrital zircons - the unique source of information on tectonics, paleogeography and denudation processes of East Antarctica (subglacial challenge)

    Science.gov (United States)

    Belyatsky, Boris; Leitchenkov, German; Rodionov, Nickolay; Antonov, Anton; Sergeev, Sergey; Savva, Helen

    2010-05-01

    Vast (about 7 billions km2) almost wholly (98%) covered with ice continental mass of East Antarctica is the central fragment of ancient supercontinents of Rodinia and Gondwana. Any information on its geologic structure is of the greatest importance for solving the problems of formation and amalgamation of lithosphere of ancient continents, processes of intraplate activity, denudation and peneplanation of the earth crust and for geodynamic reconstruction. Geologic structure of central part of the East Antarctica is still absolutely unknown due to the thick (up to 4000 m) ice cover, which is the obstacle even for modern drilling technology to sample directly the underlying rocks. The main goal of the study has been to make an attempt in fill up the hiatus in geologic knowledge on the origin of subglacial continental crust of the Antarctica. We studied detrital zircons from sedimentary and metasedimentary rocks outcropped in Prince-Charles Mts (PCM, East Antarctica). Rock specimens were sampled from the Permian-Triassic sedimentary succession outcropped along the Beaver Lake coast (sandstones and siltstones) and from moraine of the Fisher Massive (metasandstone) and Meridith Massive (sandstone). A lump of zircons which are characterized by different grain morphology from well-rounded to poorly-rounded has been extracted from rock specimens for isotopic studies and dating. The age determinations of 302 zircons from 6 specimens were conducted using secondary ion-microprobe SHRIMP-II and laser-ablation ICP-MS. The age of zircons ranges from 500 to 3200 Ma. Isotopic analysis and probability distribution diagrams for zircon populations show heterogeneity of provenance. Zircons of 500 Ma old are proposed to come from the eastern flank of Lambert Glacier and/or from central Antarctica; 900-1100 Ma old - from Proterozoic Mobile Belt (central-northern PCM); while 2400-3200 Ma old - from granite-greenstone terrain (southern PCM). Additionally, 21 trace elements and isotopic

  16. Morphotypes of virus-like particles in two hydrothermal vent fields on the East Scotia Ridge, Antarctica.

    Science.gov (United States)

    Millard, Andrew D; Hands-Portman, Ian; Zwirglmaier, Katrin

    2014-01-01

    Viruses from extreme environments are still largely unexplored and may harbor unseen genetic potential. Here, we present a first glance at the morphological diversity of virus like particles (VLPs) from an environment that is extreme in more than one respect: two recently discovered hydrothermal vent fields on the East Scotia Ridge in the Southern Ocean near Antarctica. They are the southernmost hydrothermal sites found to date and have been shown to present a new biogeographic province, containing several new macrofaunal species and associated microbial organisms. Transmission electron microscopy revealed a range of tailed and untailed VLPs of various morphologies as well as an unusual long rod-shaped VLP with three long filaments. Based on its distant similarity with several known archaeal viruses, we hypothesize that this presents a new viral morphology that most likely infects an archaeon. Notably absent in the samples we analyzed were lemon- or spindle-shaped VLPs that have previously been described in other hydrothermal vent settings.

  17. Exploring the Recovery Lakes region and interior Dronning Maud Land, East Antarctica, with airborne gravity, magnetic and radar measurements

    DEFF Research Database (Denmark)

    Forsberg, René; Olesen, Arne Vestergaard; Ferraccioli, Fausto

    2017-01-01

    for major Dronning Maud Land ice stream systems, from the grounding lines up to the Recovery Lakes drainage basin, and filled in major data voids in Antarctic data compilations, such as AntGP for gravity data, ADMAP for magnetic data and BEDMAP2 for ice thickness data and the sub-ice topography. We present......Long-range airborne geophysical measurements were carried out in the ICEGRAV campaigns, covering hitherto unexplored parts of interior East Antarctica and part of the Antarctic Peninsula. The airborne surveys provided a regional coverage of gravity, magnetic and ice-penetrating radar measurements...... the first maps of gravity, magnetic and ice thickness data and bedrock topography for the region and show examples of bedrock topography and basal reflectivity patterns. The 2013 Recovery Lakes campaign was carried out with a British Antarctic Survey Twin Otter aircraft operating from the Halley...

  18. Origin and characterisation of microparticles in an ice core from the Central Dronning Maud Land, East Antarctica.

    Science.gov (United States)

    Laluraj, C M; Krishnan, K P; Thamban, M; Mohan, R; Naik, S S; D'Souza, W; Ravindra, R; Chaturvedi, A

    2009-02-01

    The scanning electron microscopy-energy dispersive spectroscopic (SEM-EDS) study of selected samples from an ice core collected from Central Dronning Maud Land (CDML), East Antarctica, revealed several microparticles. They are mainly siliceous and carbonaceous particles and have distinct variations in their shape and composition. The morphology and major element chemistry of the particles suggest their origin from either volcanic eruptions or continental dust. The EDS analysis revealed that the volcanic particles are enriched in silica (average SiO2 62%), compared to the continental dust particle (average SiO2 56%). We found that the tephra relating to Agung (1963) and Karkatau (1883) volcanic eruptions, as recorded, in the ice core harbored microbial cells (both coocoid and rods). The occurrence of organic and inorganic particles which bear relation to volcanic eruption and continental dust implies significant environmental changes in the recent past.

  19. Distribution and diversity of soil microfauna from East Antarctica: assessing the link between biotic and abiotic factors.

    Directory of Open Access Journals (Sweden)

    Alejandro Velasco-Castrillón

    Full Text Available Terrestrial life in Antarctica has been described as some of the simplest on the planet, and mainly confined to soil microfaunal communities. Studies have suggested that the lack of diversity is due to extreme environmental conditions and thought to be driven by abiotic factors. In this study we investigated soil microfauna composition, abundance, and distribution in East Antarctica, and assessed correlations with soil geochemistry and environmental variables. We examined 109 soil samples from a wide range of ice-free habitats, spanning 2000 km from Framnes Mountains to Bailey Peninsula. Microfauna across all samples were patchily distributed, from complete absence of invertebrates to over 1600 specimens/gram of dry weight of soil (gdw, with highest microfauna abundance observed in samples with visible vegetation. Bdelloid rotifers were on average the most widespread found in 87% of sampled sites and the most abundant (44 specimens/gdw. Tardigrades occurred in 57% of the sampled sites with an abundance of 12 specimens/gdw. Nematodes occurred in 71% of samples with a total abundance of 3 specimens/gdw. Ciliates and mites were rarely found in soil samples, with an average abundance of 1.3 and 0.04 specimens/gdw, respectively. We found that microfaunal composition and abundance were mostly correlated with the soil geochemical parameters; phosphorus, NO3 (- and salinity, and likely to be the result of soil properties and historic landscape formation and alteration, rather than the geographic region they were sampled from. Studies focusing on Antarctic biodiversity must take into account soil geochemical and environmental factors that influence population and species heterogeneity.

  20. Distribution and diversity of soil microfauna from East Antarctica: assessing the link between biotic and abiotic factors.

    Science.gov (United States)

    Velasco-Castrillón, Alejandro; Schultz, Mark B; Colombo, Federica; Gibson, John A E; Davies, Kerrie A; Austin, Andrew D; Stevens, Mark I

    2014-01-01

    Terrestrial life in Antarctica has been described as some of the simplest on the planet, and mainly confined to soil microfaunal communities. Studies have suggested that the lack of diversity is due to extreme environmental conditions and thought to be driven by abiotic factors. In this study we investigated soil microfauna composition, abundance, and distribution in East Antarctica, and assessed correlations with soil geochemistry and environmental variables. We examined 109 soil samples from a wide range of ice-free habitats, spanning 2000 km from Framnes Mountains to Bailey Peninsula. Microfauna across all samples were patchily distributed, from complete absence of invertebrates to over 1600 specimens/gram of dry weight of soil (gdw), with highest microfauna abundance observed in samples with visible vegetation. Bdelloid rotifers were on average the most widespread found in 87% of sampled sites and the most abundant (44 specimens/gdw). Tardigrades occurred in 57% of the sampled sites with an abundance of 12 specimens/gdw. Nematodes occurred in 71% of samples with a total abundance of 3 specimens/gdw. Ciliates and mites were rarely found in soil samples, with an average abundance of 1.3 and 0.04 specimens/gdw, respectively. We found that microfaunal composition and abundance were mostly correlated with the soil geochemical parameters; phosphorus, NO3 (-) and salinity, and likely to be the result of soil properties and historic landscape formation and alteration, rather than the geographic region they were sampled from. Studies focusing on Antarctic biodiversity must take into account soil geochemical and environmental factors that influence population and species heterogeneity.

  1. Evaluating precipitation in a regional climate model using ground-based radar measurements in Dronning Maud Land, East Antarctica

    Science.gov (United States)

    Gorodetskaya, Irina; Maahn, Maximilan; Gallée, Hubert; Souverijns, Niels; Gossart, Alexandra; Kneifel, Stefan; Crewell, Susanne; Van Lipzig, Nicole

    2017-04-01

    Occasional very intense snowfall events over Dronning Maud Land (DML) region in East Antarctica, contributed significantly to the entire Antarctic ice sheet surface mass balance (SMB) during the last years. The meteorological-cloud-precipitation observatory running at the Princess Elisabeth station (PE) in the DML escarpment zone since 2009 (HYDRANT/AEROCLOUD projects), provides unique opportunity to estimate contribution of precipitation to the local snow accumulation and new data for evaluating precipitation in climate models. Our previous work using PE measurements showed that occasional intense precipitation events determine the total local yearly SMB and account for its large interannual variability. Here we use radar measurements to evaluate precipitation in a regional climate model with a special focus on intense precipitation events together with the large-scale atmospheric dynamics responsible for these events. The coupled snow-atmosphere regional climate model MAR (Modèle Atmosphérique Régional) is used to simulate climate and SMB in DML at 5-km horizontal resolution during 2012 using initial and boundary conditions from the European Centre for Medium-range Weather Forecasts (ECMWF) Interim re-analysis atmospheric and oceanic fields. Two evaluation approaches are used: observations-to-model and model-to-observations. In the first approach, snowfall rate (S) is derived from the MRR (vertically profiling 24-GHz precipitation radar) effective reflectivity factor (Ze) at 400 m agl using various Ze-S relationships for dry snow. The uncertainty in Ze-S relationships is constrained using snow particle size distribution from Snow Video Imager - Precipitation Imaging Package (SVI/PIP) and information about particle shapes. For the second approach we apply the Passive and Active Microwave radiative TRAnsfer model (PAMTRA), which allows direct comparison of the radar-measured and climate model-based vertical profiles of the radar Ze and Doppler velocity. In MAR

  2. Measurements of precipitation in Dumont d'Urville, Adélie Land, East Antarctica

    Science.gov (United States)

    Grazioli, Jacopo; Genthon, Christophe; Boudevillain, Brice; Duran-Alarcon, Claudio; Del Guasta, Massimo; Madeleine, Jean-Baptiste; Berne, Alexis

    2017-08-01

    The first results of a campaign of intensive observation of precipitation in Dumont d'Urville, Antarctica, are presented. Several instruments collected data from November 2015 to February 2016 or longer, including a polarimetric radar (MXPol), a Micro Rain Radar (MRR), a weighing gauge (Pluvio2), and a Multi-Angle Snowflake Camera (MASC). These instruments collected the first ground-based measurements of precipitation in the region of Adélie Land (Terre Adélie), including precipitation microphysics. Microphysical observations during the austral summer 2015/2016 showed that, close to the ground level, aggregates are the dominant hydrometeor type, together with small ice particles (mostly originating from blowing snow), and that riming is a recurring process. Eleven percent of the measured particles were fully developed graupel, and aggregates had a mean riming degree of about 30 %. Spurious precipitation in the Pluvio2 measurements in windy conditions, leading to phantom accumulations, is observed and partly removed through synergistic use of MRR data. The yearly accumulated precipitation of snow (300 m above ground), obtained by means of a local conversion relation of MRR data, trained on the Pluvio2 measurement of the summer period, is estimated to be 815 mm of water equivalent, with a confidence interval ranging between 739.5 and 989 mm. Data obtained in previous research from satellite-borne radars, and the ERA-Interim reanalysis of the European Centre for Medium-Range Weather Forecasts (ECMWF) provide lower yearly totals: 655 mm for ERA-Interim and 679 mm for the climatological data over DDU. ERA-Interim overestimates the occurrence of low-intensity precipitation events especially in summer, but it compensates for them by underestimating the snowfall amounts carried by the most intense events. Overall, this paper provides insightful examples of the added values of precipitation monitoring in Antarctica with a synergistic use of in situ and remote sensing

  3. Distributions of larval and juvenile/adult stages of the Antarctic myctophid fish, Electrona antarctica, off Wilkes Land in East Antarctica

    Science.gov (United States)

    Moteki, Masato; Fujii, Kentaro; Amakasu, Kazuo; Shimada, Keishi; Tanimura, Atsushi; Odate, Tsuneo

    2017-06-01

    Myctophid fish are an important component of the Southern Ocean food web because of their very high biomass. This study investigated the spatial distributions of larval and juvenile/adult stages of the Antarctic myctophid Electrona antarctica. Fish were sampled in January 2011 and 2012 on a transect along 140°E and in January 2013 along 110°E using two different opening/closing net systems. In total, 1075 specimens of E. antarctica were collected: 948 larvae, 127 juveniles/adults, and 2 in the transformation stage. Most larvae were collected at 5-200 m depth, with diel vertical migration (DVM) not apparent. Larvae were mainly distributed in the Modified Circumpolar Deep Water (-1.5 °C-2.0 °C). By contrast, an analysis of the echogram at 38 kHz and discrete depth samples implied that juveniles/adults undertook DVM except in the continental slope area (65.5°S). As the distribution of krill is limited to the cold water mass (<-1.5 °C) along the continental slope, E. antarctica and krill populations are spatially separated off Wilkes Land during summer. According to the previously estimated larval period of 30-47 days, E. antarctica may spawn in late November to December in the marginal ice zone or near the sea ice edge. This study suggests that the environment related to sea ice provides a nursery ground for early stage larvae of E. antarctica.

  4. Environmental and ice volume changes based on seismic stratigraphy in Sabrina Coast, East Antarctica: Preliminary results from NBP1402

    Science.gov (United States)

    Gulick, S. P. S.; Fernandez-Vasquez, R. A.; Frederick, B.; Saustrup, S., Sr.; Domack, E. W.; Lavoie, C.; Shevenell, A.; Blankenship, D. D.; Leventer, A.

    2014-12-01

    In 2014, the R/V Nathaniel B. Palmer (NBP1402) sailed to a virtually unexplored continental shelf along the Sabrina Coast, East Antarctica. The shelf contains the sedimentary record of environmental and ice volume changes within the Aurora Subglacial Basin (ASB), which is presently occupied by ~7 m sea level-rise equivalent of ice. We acquired 750 km of high-resolution seismic data proximal to the Reynolds Trough and Moscow University Ice Shelf glacial systems west of the Dalton Ice Tongue using dual 45/45 cu. in. G.I. guns and a 24 ch. streamer with 3.125 m groups providing a vertical resolution of ~3 m simultaneously with CHIRP data. These are the first images of this margin acquired and show a remarkable set of sequence stratigraphic transitions. Crystalline basement is at the seafloor landward and buried seaward with a transition to smoother reflection interface. Reflective sedimentary strata overlie the basement, dip seaward, and are capped by a landward-dipping regional angular unconformity. Above this are a series of transparent seismic facies that, along with the middle to outer shelf seafloor, dip landward towards a shelf-oblique glacial trough. The older, seaward-dipping strata include a deeper series of units that display at least three stratal architectures interpreted to be shelf deltas implying a pre-glacial, fluvial environment within the drainage basin. Above these sequences, the seismic facies transition to surfaces exhibiting significant erosion, small u-shaped valleys, and channel fill sequences, all of which are reminiscent of temperate glacial features. We interpret these sequences as including sub-ice tunnel valleys and grounding zone wedges with interspersed non-glacial to pro-glacial deposits. Increasing glaciogenic facies upsection suggests a gradual fluvial to glacial transition and increasing glacial extent with time. The subsequent transition to ice sheets is marked by erosion to basement landward and the angular unconformity seaward

  5. Characteristics and sources of tephra layers in the EPICA-Dome C ice record (East Antarctica): Implications for past atmospheric circulation and ice core stratigraphic correlations [rapid communication

    Science.gov (United States)

    Narcisi, B.; Petit, J. R.; Delmonte, B.; Basile-Doelsch, I.; Maggi, V.

    2005-11-01

    Thirteen discrete air-fall tephra layers were identified in the last 200,000-yr section of the EPICA-Dome C ice record drilled in the East Antarctic plateau (75°06'S, 123°21'E). Quantitative grain size, glass particle morphology, and the grain-discrete major element composition of the glass fraction of these layers were investigated. Through comparison with literature data on the rock composition of Quaternary volcanic centres located within and around Antarctica, five tephra layers were attributed to South Sandwich volcanoes in the South Atlantic Ocean, two to South Shetland volcanoes (northern Antarctic Peninsula), two to Andean volcanoes, and four to Antarctic (Marie Byrd Land and Melbourne) provinces. The abundance of layers originating in the southern part of the Atlantic confirms that westerly atmospheric circulation spiralling towards East Antarctica prevailed over the last 200 ka. Moreover, the record of events from Antarctic centres suggests that atmospheric trajectories from West to East Antarctica can also be significant. A few ash layers are geochemically distinct and appear equivalent to levels from Vostok and Dome Fuji deep ice records, located ca. 600 km and ca. 2000 km, respectively, from Dome C on the Antarctic plateau. These layers provide unambiguous markers for future correlation with other Antarctic ice cores and circumpolar marine climatic records. They also provide reliable constraints to get a common timescale by glaciological modelling, and represent a first step towards absolute ice core dating.

  6. Cosmogenic evidence for limited local LGM glacial expansion, Denton Hills, Antarctica

    Science.gov (United States)

    Joy, Kurt; Fink, David; Storey, Bryan; De Pascale, Gregory P.; Quigley, Mark; Fujioka, Toshiyuki

    2017-12-01

    The geomorphology of the Denton Hills provides insight into the timing and magnitude of glacial retreats in a region of Antarctica isolated from the influence of the East Antarctic ice sheet. We present 26 Beryllium-10 surface exposure ages from a variety of glacial and lacustrine features in the Garwood and Miers valleys to document the glacial history of the area from 10 to 286 ka. Our data show that the cold-based Miers, Joyce and Garwood glaciers retreated little since their maximum positions at 37.2 ± 6.9 (1σ n = 4), 35.1 ± 1.5 (1σ, n = 3) and 35.6 ± 10.1 (1σ, n = 6) ka respectively. The similar timing of advance of all three glaciers and the lack of a significant glacial expansion during the global LGM suggests a local LGM for the Denton Hills between ca. 26 and 51 ka, with a mean age of 36.0 ± 7.5 (1σ, n = 13) ka. A second cohort of exposure ages provides constraints to the behaviour of Glacial Lake Trowbridge that formerly occupied Miers Valley in the late Pleistocene. These data show active modification of the landscape from ∼20 ka until the withdrawal of ice from the valley mouths, and deposition of Ross Sea Drift, at 10-14 ka.

  7. Characteristic Cryoseismic and Oceanic Waves Associated with Surface Environments at the Lützow-Holm Bay, East Antarctica

    Science.gov (United States)

    Kanao, M.

    2014-12-01

    In a international geoscience prospect at the IPY, the 'Polar Earth Observing Network (POLENET)' was the largest contributions in establishing a seismic and GPS network in Antarctica. Several kinds of environmental signals associated with the atmosphere - ocean - cryosphere - solid earth systems were detected in the continental margins and surrounding oceans. Ice-related seismic motions for small magnitude events are generally named 'ice-quakes' ( 'ice-shocks') and can be generated by glacially related dynamics (Kanao et al., 2012). Such kinds of cryoseismic sources are consisted from the movements of ice sheets, sea-ice, oceanic tide-cracks, oceanic gravity waves, icebergs and the calving fronts of ice caps. Nettles and Ekstrom (2010), moreover, determined the hopocenter and magnitude of several large ice-quakes (glacial earthquakes) around Antarctica by using the long period surface wave data. These hypocenters locate mainly at the outlet of the large glaciers, otherwise the edge of ice shelves. Cryoseismic and oceanic waves (microseismis) are likely to be influenced by the variations in environmental conditions, including lower atmosphere, and the continuous study of their time-space variation provides indirect evidence of climate change. In this presentation, several characteristic features of cryoseismic waves observed the stations around the Lützow-Holm Bay (LHB) region are demonstrated, involving the surface environmental variations in vicinity of the area from continental coastal to the southern ocean. Hypocenters of local events in LHB, waveforms invlolving discharge of sea-ice, tide relating signals, as well as the tremor signals with characteristic frequency contents are demonstrated. As the glacial earthquakes are the most prominent evidence found recently in the polar region, these new innovative studies of polar seismology has been achieved on the basis of observational experiments and long-term monitoring under the extreme conditions in polar

  8. Aerial surveys for pack-ice seals along the Ingrid Christensen and Princess Astrid Coasts, East Antarctica

    Directory of Open Access Journals (Sweden)

    R.S. Kumar

    2014-08-01

    Full Text Available We conducted aerial surveys in the austral summer of 2009-2010 to count and record the spatial distribution patterns of pack-ice seals hauled-out along the Ingrid Christensen and Princess Astrid coast of East Antarctica. A total of 3,601 hauled-out seals were counted from six aerial surveys totalling a length of approx. 1,200km, with each survey lasting about two hours. Weddell Seal Leptonychotes weddellii was the most commonly sighted species in both the areas surveyed (98.2%, and had an encounter rate of 2.9 seals/km. The other species encountered during the survey were Crabeater Seal Lobodon carcinophaga (1.7% and Leopard Seal Hydrurga leptonyx (0.03%. Group size of hauled-out Weddell Seals varied considerably and ranged from solitary to maximum of 42 individuals. The median group size of Weddell seals hauled-out along the Ingrid Christenson Coast was found to be significantly different between the December 2009 and January 2010 survey. Further, along this coast Weddell Seals were found hauled-out mainly close to the ice shelf and their spatial distribution appeared to be influenced by the extent of sea ice in the area.

  9. The role of planktonic Flavobacteria in processing algal organic matter in coastal East Antarctica revealed using metagenomics and metaproteomics.

    Science.gov (United States)

    Williams, Timothy J; Wilkins, David; Long, Emilie; Evans, Flavia; DeMaere, Mathew Z; Raftery, Mark J; Cavicchioli, Ricardo

    2013-05-01

    Heterotrophic marine bacteria play key roles in remineralizing organic matter generated from primary production. However, far more is known about which groups are dominant than about the cellular processes they perform in order to become dominant. In the Southern Ocean, eukaryotic phytoplankton are the dominant primary producers. In this study we used metagenomics and metaproteomics to determine how the dominant bacterial and archaeal plankton processed bloom material. We examined the microbial community composition in 14 metagenomes and found that the relative abundance of Flavobacteria (dominated by Polaribacter) was positively correlated with chlorophyll a fluorescence, and the relative abundance of SAR11 was inversely correlated with both fluorescence and Flavobacteria abundance. By performing metaproteomics on the sample with the highest relative abundance of Flavobacteria (Newcomb Bay, East Antarctica) we defined how Flavobacteria attach to and degrade diverse complex organic material, how they make labile compounds available to Alphaproteobacteria (especially SAR11) and Gammaproteobacteria, and how these heterotrophic Proteobacteria target and utilize these nutrients. The presence of methylotrophic proteins for archaea and bacteria also indicated the importance of metabolic specialists. Overall, the study provides functional data for the microbial mechanisms of nutrient cycling at the surface of the coastal Southern Ocean. © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd.

  10. Generation of a high-accuracy regional DEM based on ALOS/PRISM imagery of East Antarctica

    Science.gov (United States)

    Shiramizu, Kaoru; Doi, Koichiro; Aoyama, Yuichi

    2017-12-01

    A digital elevation model (DEM) is used to estimate ice-flow velocities for an ice sheet and glaciers via Differential Interferometric Synthetic Aperture Radar (DInSAR) processing. The accuracy of DInSAR-derived displacement estimates depends upon the accuracy of the DEM. Therefore, we used stereo optical images, obtained with a panchromatic remote-sensing instrument for stereo mapping (PRISM) sensor mounted onboard the Advanced Land Observing Satellite (ALOS), to produce a new DEM ("PRISM-DEM") of part of the coastal region of Lützow-Holm Bay in Dronning Maud Land, East Antarctica. We verified the accuracy of the PRISM-DEM by comparing ellipsoidal heights with those of existing DEMs and values obtained by satellite laser altimetry (ICESat/GLAS) and Global Navigation Satellite System surveying. The accuracy of the PRISM-DEM is estimated to be 2.80 m over ice sheet, 4.86 m over individual glaciers, and 6.63 m over rock outcrops. By comparison, the estimated accuracy of the ASTER-GDEM, widely used in polar regions, is 33.45 m over ice sheet, 14.61 m over glaciers, and 19.95 m over rock outcrops. For displacement measurements made along the radar line-of-sight by DInSAR, in conjunction with ALOS/PALSAR data, the accuracy of the PRISM-DEM and ASTER-GDEM correspond to estimation errors of <6.3 mm and <31.8 mm, respectively.

  11. Uplift and tilting of the Shackleton Range in East Antarctica driven by glacial erosion and normal faulting

    Science.gov (United States)

    Paxman, Guy J. G.; Jamieson, Stewart S. R.; Ferraccioli, Fausto; Bentley, Michael J.; Forsberg, Rene; Ross, Neil; Watts, Anthony B.; Corr, Hugh F. J.; Jordan, Tom A.

    2017-03-01

    Unravelling the long-term evolution of the subglacial landscape of Antarctica is vital for understanding past ice sheet dynamics and stability, particularly in marine-based sectors of the ice sheet. Here we model the evolution of the bedrock topography beneath the Recovery catchment, a sector of the East Antarctic Ice Sheet characterized by fast-flowing ice streams that occupy overdeepened subglacial troughs. We use 3-D flexural models to quantify the effect of erosional unloading and mechanical unloading associated with motion on border faults in driving isostatic bedrock uplift of the Shackleton Range and Theron Mountains, which are flanked by the Recovery, Slessor, and Bailey ice streams. Inverse spectral (free-air admittance) and forward modeling of topography and gravity anomaly data allow us to constrain the effective elastic thickness of the lithosphere (Te) in the Shackleton Range region to 20 km. Our models indicate that glacial erosion, and the associated isostatic rebound, has driven 40-50% of total peak uplift in the Shackleton Range and Theron Mountains. A further 40-50% can be attributed to motion on normal fault systems of inferred Jurassic and Cretaceous age. Our results indicate that the flexural effects of glacial erosion play a key role in mountain uplift along the East Antarctic margin, augmenting previous findings in the Transantarctic Mountains. The results suggest that at 34 Ma, the mountains were lower and the bounding valley floors were close to sea level, which implies that the early ice sheet in this region may have been relatively stable.

  12. Seasonal Variations in Drag Coefficient over a Sastrugi-Covered Snowfield in Coastal East Antarctica

    Science.gov (United States)

    Amory, Charles; Gallée, Hubert; Naaim-Bouvet, Florence; Favier, Vincent; Vignon, Etienne; Picard, Ghislain; Trouvilliez, Alexandre; Piard, Luc; Genthon, Christophe; Bellot, Hervé

    2017-02-01

    The surface of windy Antarctic snowfields is subject to drifting snow, which leads to the formation of sastrugi. In turn, sastrugi contribute to the drag exerted by the snow surface on the atmosphere and hence influence drifting snow. Although the surface drag over rough sastrugi fields has been estimated for individual locations in Antarctica, its variation over time and with respect to drifting snow has received little attention. Using year-round data from a meteorological mast, seasonal variations in the neutral drag coefficient at a height of 10 m (C_{{ DN}10}) in coastal Adelie Land are presented and discussed in light of the formation and behaviour of sastrugi based on observed aeolian erosion patterns. The measurements revealed high C_{{ DN}10} values (≥ 2 × 10^{-3}) and limited drifting snow (35% of the time) in summer (December-February) versus lower C_{{ DN}10} values (≈ 1.5 × 10^{-3}) associated with more frequent drifting snow (70% of the time) in winter (March-November). Without the seasonal distinction, there was no clear dependence of C_{{ DN}10} on friction velocity or wind direction, but observations revealed a general increase in C_{{ DN}10} with rising air temperature. The main hypothesis defended here is that higher temperatures increase snow cohesion and the development of sastrugi just after snow deposition while inhibiting the sastrugi streamlining process by raising the erosion threshold. This increases the contribution of the sastrugi form drag to the total surface drag in summer when winds are lighter and more variable. The analysis also showed that, in the absence of erosion, single snowfall events can reduce C_{{ DN}10} to 1 × 10^{-3} due to the burying of pre-existing microrelief under newly deposited snow. The results suggest that polar atmospheric models should account for spatial and temporal variations in snow surface roughness through a dynamic representation of the sastrugi form drag.

  13. Revised model of the East Gondwana Break-up and formation of the Gateway between India and Antarctica

    Science.gov (United States)

    Leitchenkov, German; Guseva, Julia; Ivanov, Sergey; Golynsky, Alexander

    2017-04-01

    The history of break-up and sea-floor spreading between India and Antarctica long remained vague mainly because of the data scarcity off both continents. Geophysical studies carried out recently in the Enderby Basin (Southern Indian Ocean) provided new information and advanced our knowledge on this problem. Magnetic surveys discovered there a prominent linear high-amplitude bipolar magnetic anomaly (HBMA), which stretched more than 1000 km westward from the southern Kerguelen Plateau. This anomaly was interpreted by many as the contact between stretched continental crust and oceanic crust. Gaina et al. (1987) suggested the existence of an abandoned spreading centre in the eastern Enderby Basin and inferred that the Elan Bank (established as a microcontinent) was isolated from the India margin by a ridge jump at about M0 chron (c. 120 Ma). South of an abandoned spreading centre, they identified a series of magnetic anomalies from M2 to M9. New magnetic data collected in the western Enderby Basin and revision of all available geophysical data gives a new notion on the geodynamics of the East Gondwana break-up and separation of India from Antarctica. According to a new model, the HBMA corresponds to M34o chrone and its increased intensity can be explained by the emplacement of the Kerguelen Hotspot and thickening of the oceanic (magmatic) crust at that time. A relationship between hot-spots and appearance of high-amplitude magnetic anomalies is observed elsewhere in the World Ocean. In our model, the continent-ocean boundary is located about 150 km landward of the HBMA, and anomalies from M4 to M0 are identified between these features. The ridge jump (which isolated the Elan Bank) occurred about 110 Ma ago when the Kerguelen Hotspot moved toward the India margin. This model is consistent with the interpretation of sea-floor spreading history off Western Australia. An earlier (around 120 Ma) ridge jump probably occurred in the area of the southern Kerguelen Plateau

  14. Aerosol and CCN properties at Princess Elisabeth station, East Antarctica: seasonality, new particle formation events and properties around precipitation events

    Science.gov (United States)

    Mangold, Alexander; Laffineur, Quentin; De Backer, Hugo; Herenz, Paul; Wex, Heike; Gossart, Alexandra; Souverijns, Niels; Gorodetskaya, Irina; Van Lipzig, Nicole

    2016-04-01

    Since 2010, several complementary ground-based instruments for measuring the aerosol composition of the Antarctic atmosphere have been operated at the Belgian Antarctic research station Princess Elisabeth, in Dronning Maud Land, East Antarctica (71.95° S, 23.35° E, 1390 m asl.). In addition, three ground-based remote sensing instruments for cloud and precipitation observations have been installed for continuous operation, including a ceilometer (cloud base height, type, vertical extent), a 24 Ghz micro-rain radar (vertical profiles of radar effective reflectivity and Doppler velocity), and a pyrometer (cloud base temperature). The station is inhabited from November to end of February and operates under remote control during the other months. In this contribution, the general aerosol and cloud condensation nuclei (CCN) properties will be described with a special focus on new particle formation events and around precipitation events. New particle formation events are important for the atmospheric aerosol budget and they also show that aerosols are not only transported to Antarctica but are also produced there, also inland. Aerosols are essential for cloud formation and therefore also for precipitation, which is the only source for mass gain of the Antarctic ice sheet. Measured aerosol properties comprise size distribution, total number, total mass concentration, mass concentration of light-absorbing aerosol and absorption coefficient and total scattering coefficient. In addition, a CCN counter has been operated during austral summers 2013/14, 2014/15 and 2015/16. The baseline total number concentration N-total was around some hundreds of particles/cm3. During new particle formation events N-total increased to some thousands of particles/cm3. Simultaneous measurements of N-total, size distribution and CCN number revealed that mostly the number of particles smaller than 100 nm increased and that the concentration of cloud condensation nuclei increased only very

  15. Interpreting last glacial to Holocene dust changes at Talos Dome (East Antarctica: implications for atmospheric variations from regional to hemispheric scales

    Directory of Open Access Journals (Sweden)

    S. Albani

    2012-04-01

    Full Text Available Central East Antarctic ice cores preserve stratigraphic records of mineral dust originating from remote sources in the Southern Hemisphere, and represent useful indicators of climatic variations on glacial-interglacial time scales. The peripheries of the East Antarctic Ice Sheet, where ice-free areas with the potential to emit dust exist, have been less explored from this point of view. Here, we present a new profile of dust deposition flux and grain size distributions from an ice core drilled at Talos Dome (TALDICE, Northern Victoria Land, East Antarctica, where there is a significant input of dust from proximal Antarctic ice-free areas. We analyze dust and stable water isotopes variations from the Last Glacial Maximum to the Late Holocene, and compare them to the EPICA Dome C profiles from central East Antarctica. The smaller glacial-interglacial variations at Talos Dome compared to Dome C and a distinctive decreasing trend during the Holocene characterize the TALDICE dust profile. By deciphering the composite dust signal from both remote and local sources, we show the potential of this combined proxy of source activity and atmospheric transport to give information on both regional and larger spatial scales. In particular, we show how a regional signal, which we relate to the deglaciation history of the Ross Sea embayment, can be superimposed to the broader scale glacial-interglacial variability that characterizes other Antarctic sites.

  16. Seismic sources near Jang Bogo Station, Terra Nova Bay, East Antarctica

    Science.gov (United States)

    Kong, C.; Kang, T. S.

    2016-12-01

    The Jang Bogo Research Station is the second Korean Antarctic base which was build in Terra Nova Bay, Victoria Land, in the southeastern part of Antarctica in 2014. For the purpose of monitoring various natural seismic signals as well as local earthquakes in and around the station, two broadband seismographs were installed within the station compound and were operated during the second overwintering period from December 2014 to November 2015. Seismic data were continuously recorded during the period, and thus they might deliver much of information on the natural and artificial phenomena in the vicinity of the station. From both the temporal and spectral analyses, it was revealed that the continuous data are consisted of various types of event waveforms which are strongly correlated with variety of seismic sources. Event waveforms are classified into major four categories in accordance with their origin: tectonic earthquakes, volcanic earthquakes, cryogenic events such as icequakes, and atmospheric perturbation. Besides typical waveforms from local and teleseismic earthquakes, local volcano-related signals are expected. A prime source of those signals is Mt. Melbourne which is the only active volcano on the Antarctic mainland and is located in about 30 km northeast of the Jang Bogo station. While no magma eruption occurred during the overwinter period, phreatic eruptions of gases at the summit of Mt. Melbourne were observed sporadically. Seismic sources of the ice-related signal are associated with the Campbell glacier which is originated from the end of Mesa Range in Victoria Land. The Campbell glacier flows into Terra Nova Bay in Ross Sea and forms Campbell ice tongue that is a seaward extension of the glacier. The fast-flowing movement of the glacier appears to generate seismic signals observed at the station. Sometimes katabatic winds, which are downslope winds transiently blowing from Mt. Browning during the Antarctic winter period, massaged the ground and thus

  17. Radionuclides in ornithogenic sediments as evidence for recent warming in the Ross Sea region, Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Nie, Yaguang [Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026 (China); Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Key Laboratory of Environmental Toxicology and Pollution Control Technology of Anhui Province, Hefei, Anhui 230031 (China); Xu, Liqiang [School of Resources and Environmental Engineering, Hefei University of Technology, Hefei, Anhui 230009 (China); Liu, Xiaodong, E-mail: ycx@ustc.edu.cn [Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026 (China); Emslie, Steven D. [Department of Biology and Marine Biology, University of North Carolina Wilmington, 601 S. College Road, Wilmington, NC 28403 (United States)

    2016-07-01

    Radionuclides including {sup 210}Pb, {sup 226}Ra and {sup 137}Cs were analyzed in eight ornithogenic sediment profiles from McMurdo Sound, Ross Sea region, East Antarctica. Equilibration between {sup 210}Pb and {sup 226}Ra were reached in all eight profiles, enabling the determination of chronology within the past two centuries through the Constant Rate of Supply (CRS) model. Calculated fluxes of both {sup 210}Pb and {sup 137}Cs varied drastically among four of the profiles (MB4, MB6, CC and CL2), probably due to differences in their sedimentary environments. In addition, we found the flux data exhibiting a clear decreasing gradient in accordance with their average deposition rate, which was in turn related to the specific location of the profiles. We believe this phenomenon may correspond to global warming of the last century, since warming-induced surface runoff would bring more inflow water and detritus to the coring sites, thus enhancing the difference among the profiles. To verify this hypothesis, the deposition rate against age of the sediments was calculated based on their determined chronology, which showed ascending trends in all four profiles. The significant increase in deposition rates over the last century is probably attributable to recent warming, implying a potential utilization of radionuclides as environmental indicators in this region. - Highlights: • {sup 210}Pb, {sup 226}Ra and {sup 137}Cs were measured in ornithogenic sediment profiles. • Chronology within 200 years was determined through Constant Rate of Supply model. • Calculated nuclide fluxes decreased with average deposition rate and locations. • Deposition rate over time indicated warming which caused the flux gradient.

  18. Crustal architecture and tectonic evolution in the South Pole frontier, East Antarctica, in light of recent aerogeophysical observations

    Science.gov (United States)

    Ferraccioli, Fausto; Jordan, Tom; Forsberg, Rene; Olesen, Arne; Eagles, Graeme; Matsuoka, Kenichi; Casal, Tania

    2017-04-01

    Our knowledge of interior East Antarctica has increased significantly in recent years, aided by major aerogeophysical exploration efforts conducted by the geosciences community since the International Polar Year. Aerogeophysical and satellite imaging is helping unveil cryptic crustal provinces and this is enabling new studies of the major tectonic process that shaped East Antarctica through the supercontinent cycle (e.g. Ferraccioli et al., 2011, Nature; Aitken et al., 2014, GRL). However, the South Pole itself has remained one of the largest "poles of ignorance", as very little data have been acquired here since pioneering aerogeophysical surveys performed in the 1970's and a single more detailed US survey flown in the late 1990's from the Transantarctic Mountains to South Pole (Studinger et al., 2006, EPSL). During the 2015-2016 Antarctic campaign we flew a major aerogeophysical survey over the South Pole frontier, collecting ca 30,000 line km of new radio echo sounding, laser altimetry, airborne gravity and aeromagnetic data. The main aim of the PolarGAP project, supported by the European Space Agency was to fill in the data void in GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) satellite gravity south of 83.3°S. Here we present the new ice thickness, bedrock topography, and gravity and magnetic anomaly images derived from the survey and interpret them to investigate the crustal architecture and tectonic evolution of the South Pole region. The Free-air gravity and radar data reveal the form and extent of the Pensacola-Pole Subglacial Basin that stretches from the Weddell Sea to South Pole. Linear free-air gravity lows within the basin are interpreted here as a system of glacially overdeepened grabens flanked by uplifted horst blocks, including the Pensacola Mountains, Patuxent Range and the Argentine Range. The grabens are inferred to be linked to the Jurassic Transantarctic rift system, which at regional to continental-scale, is associated

  19. The subglacial Lake Vostok (East Antarctica) surface snow is Earth-bound DNA (and dust)-free

    Science.gov (United States)

    Bulat, S.; Marie, D.; Bulat, E.; Alekhina, I.; Petit, J.-R.

    2012-09-01

    The objective was to assess the microbial cell abundance in the surface snow in Central East Antarctica and the fate of microbial genomic DNA during summer short-time exposure to surface climatic (and radiation) conditions at Vostok using flow cytometry and DNA-based methods. The surface snow (until 4m deep) was collected as clean as possible in the vicinity of the Vostok station (3 sites - courtesy of A Ekaykin and ASC Lebedev Physical Iinstitute RAS) and towards the Progress station (4 more sites with one just 29km from the coast - courtesy of A Ekaykin and S Popov) in specially decontaminated plastic crates or containers of various volumes (up to 75 kg of snow). All subsequent snow treatment manipulations (melting, concentrating, genomic DNA extraction, primary PCR set up) were performed in clean room laboratory facilities (LGGE, UJF-CNRS, Grenoble, France). Cell concentrations were determined on meltwater aliquots prepared under clean room conditions using flow cytofluorometry (Biostation, Roscoff, France). The highly concentrated meltwater (until 10000 times down) was used to extract gDNA which were subjected to bacterial 16S rRNA genes amplification in PCR and sequencing. The gDNA of a complex mesophile microbial community for exposure trials were also prepared and put onto a filter under strict clean room conditions. The filters were got exposed open to solar radiation and surface temperature at Vostok during January for various time duration periods (from 25 to 1 day). As a result no microbial cells were confidently detected in surface snow samples differed by sampling sites and people asked to collect as well. Complementary the mineral dust particle abundance did not exceed 16 mkg per liter with the particle size mode about 2.5 mkm as shown using Coulter counter. Preliminary amongst the microparticles no unusual findings (e.g. spherules of cosmic origin) were observed by shape and element composition using electron scanning microscopy. The gDNA studies

  20. Outline of surface mass balance at Dome Fuji, East Antarctica, by the stake method from 1995 to 2006

    Directory of Open Access Journals (Sweden)

    Takao Kameda

    2008-06-01

    Full Text Available This paper describes observational results of surface mass balance (SMB at Dome Fuji (77°19'01″S, 39°42'11″E; 3810m a.s.l., East Antarctica from 1995 to 2006. The SMB was estimated using 36 bamboo stakes (grid of 6×6, placed at 20m intervals. The heights of the stake tops from the snow surface were measured at 0.5cm resolution twice monthly in 1995, 1996, 1997, and 2003, and once a year for the rest of the study period. The annual SMB from 1995 to 2006 at Dome Fuji was 27.3±1.5kgm^a^. This result agrees well with the annual SMB from AD 1260 to 1993 (26.4kgm^a^, estimated from volcanic signals in the Dome Fuji ice core. From 1995 to 2006, there were 37 incidences of negative or zero annual SMB, which was 8.6%. Compared with similar studies at Vostok, South Pole and Dome C, we found that a site with SMB over 190kgm^a^ is expected to have annual snow accumulation at the 95% confidence level. Sites from 1500 to 2500m above sea level fit the criteria on the Antarctic ice sheet. According to stake and snow pit observations at Vostok, we estimated that the probability of an annual layer missing (hiatus at Dome Fuji under present-day and glacial conditions are 9.4% and 11.4%, respectively. Variations of SMB measured by 36-stakes for 12 years were also analyzed.

  1. Totten Glacier, East Antarctica: How has ocean access to the ice shelf cavity shaped local elevation change patterns?

    Science.gov (United States)

    Greenbaum, J. S.; Young, D. A.; Roberts, J. L.; Richter, T.; Warner, R. C.; van Ommen, T. D.; Siegert, M. J.; Blankenship, D. D.

    2013-12-01

    Totten Glacier has the largest outflow of any glacier in East Antarctica and is in mass deficit despite 40 years of anomalously high snowfall. As a result, the glacier and its floating terminus have been the focus of several geophysical studies over the last decade. In particular, the international collaborative ICECAP Project has acquired over 10,000 line-kilometers of aerogeophysical data from the grounding zone over the floating terminus and onto the inner continental shelf. Several flights in 2010 and 2012 were focused on continuing the time series of surface elevation change conducted by the ICESAT mission that ended in 2009 while other flights were flown to map the subglacial context for the observed elevation change and to determine the broad scale bathymetry beneath the ice shelf and nearby sea ice using airborne gravimetry. The gravimetry experiment was expanded in 2012 with an advanced, three-axis stabilized GT-1A gravimeter which significantly improved both data coverage and quality over previous ICECAP seasons. With the new gravimeter installed, five-km spaced coast parallel survey lines were flown from the lower reaches of the cavity to about 100km seaward of the terminus to infer the presence of sills and potential warm water pathways from the continental shelf to the deep glacier cavity. Here we present updated elevation change measurements in the context of the new bathymetry information and show that ocean access to the cavity is complicated by high bedrock near the terminus of the glacier. Verification of warm water intrusion potential will require new oceanographic observations such as those planned for the collaborative US-Australian marine survey scheduled to sail on the NB Palmer in February 2014.

  2. Glaciological and geophysical investigations aimed at organization of a new airfield at the Station Mirny (East Antarctica

    Directory of Open Access Journals (Sweden)

    S. V. Popov

    2016-01-01

    Full Text Available Main results of glaciological and geophysical engineering surveys, conducted during three summer field seasons of 2013– 2016 (59–61st Russian Antarctic Expeditions  – RAE near the Russian Station Mirny (East Antarctica, are discussed in the paper. Objective of these works was to site and then to organize a new airfield for landing of medium-range aircrafts with ski landing gears. Investigations included aerial photography, GPR surveys (georadar profiling, ice core drilling, and installation of landmarks to measure velocity of the glacier motion. The GSSI ground-penetrating radars with the main frequencies of 270 MHz and 900 MHz were used. In addition, special explorations were conducted for detecting the englacial crevasses by means of remote-sensing methods. The GPR data allowed a revealing the boundary between snow-andfirn thickness and atmospheric ice. In the course of processing of 252 travel-time curves of the diffracted waves a kinematic model of the sub-surface part of the glacier has been constructed. It was found that the dielectric permittivity of the snowfirn thickness averages 2.43; similar value for the atmospheric ice amounts to 3.0. The GPR data made it possible to determine intraglacial (englacial crevasses and to choose the most favorable field for the landing. On February 10, 2016, the first middle-range aircraft DC-3T (BT-67 had landed onto the new run-way near the station Mirny.

  3. Properties of snow overlying the sea ice off East Antarctica in late winter, 2007

    Science.gov (United States)

    Toyota, Takenobu; Massom, Robert; Tateyama, Kazutaka; Tamura, Takeshi; Fraser, Alexander

    2011-05-01

    The properties of snow on East Antarctic sea ice off Wilkes Land were examined during the Sea Ice Physics and Ecosystem Experiment (SIPEX) in late winter of 2007, focusing on the interaction with sea ice. This observation includes 11 transect lines for the measurement of ice thickness, freeboard, and snow depth, 50 snow pits on 13 ice floes, and diurnal variation of surface heat flux on three ice floes. The detailed profiling of topography along the transects and the d 18O, salinity, and density datasets of snow made it possible to examine the snow-sea-ice interaction quantitatively for the first time in this area. In general, the snow displayed significant heterogeneity in types, thickness (mean: 0.14±0.13 m), and density (325±38 kg m -3), as reported in other East Antarctic regions. High salinity was confined to the lowest 0.1 m. Salinity and d 18O data within this layer revealed that saline water originated from the surface brine of sea ice in 20% of the total sites and from seawater in 80%. From the vertical profiles of snow density, bulk thermal conductivity of snow was estimated as 0.15 W K -1 m -1 on average, only half of the value used for numerical sea-ice models. Although the upward heat flux within snow estimated with this value was significantly lower than that within ice, it turned out that a higher value of thermal conductivity (0.3 to 0.4 W K -1 m -1) is preferable for estimating ice growth amount in current numerical models. Diurnal measurements showed that upward conductive heat flux within the snow and net long-wave radiation at the surface seem to play important roles in the formation of snow ice from slush. The detailed surface topography allowed us to compare the air-ice drag coefficients of ice and snow surfaces under neutral conditions, and to examine the possibility of the retrieval of ice thickness distribution from satellite remote sensing. It was found that overall snow cover works to enhance the surface roughness of sea ice rather than

  4. Ocean circulation off east Antarctica affects ecosystem structure and sea-ice extent

    Science.gov (United States)

    Nicol, Stephen; Pauly, Tim; Bindoff, Nathan L.; Wright, Simon; Thiele, Deborah; Hosie, Graham W.; Strutton, Peter G.; Woehler, Eric

    2000-08-01

    Sea ice and oceanic boundaries have a dominant effect in structuring Antarctic marine ecosystems. Satellite imagery and historical data have identified the southern boundary of the Antarctic Circumpolar Current as a site of enhanced biological productivity. Meso-scale surveys off the Antarctic peninsula have related the abundances of Antarctic krill (Euphausia superba) and salps (Salpa thompsoni) to inter-annual variations in sea-ice extent. Here we have examined the ecosystem structure and oceanography spanning 3,500km of the east Antarctic coastline, linking the scales of local surveys and global observations. Between 80° and 150°E there is a threefold variation in the extent of annual sea-ice cover, enabling us to examine the regional effects of sea ice and ocean circulation on biological productivity. Phytoplankton, primary productivity, Antarctic krill, whales and seabirds were concentrated where winter sea-ice extent is maximal, whereas salps were located where the sea-ice extent is minimal. We found enhanced biological activity south of the southern boundary of the Antarctic Circumpolar Current rather than in association with it. We propose that along this coastline ocean circulation determines both the sea-ice conditions and the level of biological productivity at all trophic levels.

  5. Sea-ice algal primary production and nitrogen uptake rates off East Antarctica

    Science.gov (United States)

    Roukaerts, Arnout; Cavagna, Anne-Julie; Fripiat, François; Lannuzel, Delphine; Meiners, Klaus M.; Dehairs, Frank

    2016-09-01

    Antarctic pack ice comprises about 90% of the sea ice in the southern hemisphere and plays an important structuring role in Antarctic marine ecosystems, yet measurements of ice algal primary production and nitrogen uptake rates remain scarce. During the early austral spring of 2012, measurements for primary production rates and uptake of two nitrogen substrates (nitrate and ammonium) were conducted at 5 stations in the East Antarctic pack ice (63-66°S, 115-125°E). Carbon uptake was low (3.52 mg C m-2 d-1) but a trend of increased production was observed towards the end of the voyage suggesting pre-bloom conditions. Significant snow covers reaching, up to 0.8 m, induced strong light limitation. Two different regimes were observed in the ice with primarily nitrate based 'new' production (f-ratio: 0.80-0.95) at the bottom of the ice cover, due to nutrient-replete conditions at the ice-water interface, and common for pre-bloom conditions. In the sea-ice interior, POC:PN ratios (20-70) and higher POC:Chl a ratios suggested the presence of large amounts of detrital material trapped in the ice and here ammonium was the prevailing nitrogen substrate. This suggests that most primary production in the sea-ice interior was regenerated and supported by a microbial food web, recycling detritus.

  6. Regional modeling of the Shirase drainage basin, East Antarctica: full Stokes vs. shallow ice dynamics

    Science.gov (United States)

    Seddik, Hakime; Greve, Ralf; Zwinger, Thomas; Sugiyama, Shin

    2017-09-01

    A hierarchy of approximations of the force balance for the flow of grounded ice exists, ranging from the most sophisticated full Stokes (FS) formulation to the most simplified shallow ice approximation (SIA). Both are implemented in the ice flow model Elmer/Ice, and we compare them by applying the model to the East Antarctic Shirase drainage basin. First, we apply the control inverse method to infer the distribution of basal friction with FS. We then compare FS and SIA by simulating the flow of the drainage basin under present-day conditions and for three scenarios 100 years into the future defined by the SeaRISE (Sea-level Response to Ice Sheet Evolution) project. FS reproduces the observed flow pattern of the drainage basin well, in particular the zone of fast flow near the grounding line, while SIA generally overpredicts the surface velocities. As for the transient scenarios, the ice volume change (relative to the constant-climate control run) of the surface climate experiment is nearly the same for FS and SIA, while for the basal sliding experiment (halved basal friction), the ice volume change is ˜ 30 % larger for SIA than for FS. This confirms findings of earlier studies that, in order to model ice sheet areas containing ice streams and outlet glaciers with high resolution and precision, careful consideration must be given to the choice of a suitable force balance.

  7. Metamorphic evolution of the Maud Belt: P- T- t path for high-grade gneisses in Gjelsvikfjella, Dronning Maud Land, East Antarctica

    Science.gov (United States)

    Bisnath, Avinash; Frimmel, Hartwig E.

    2005-12-01

    A metamorphic petrological study, in conjunction with recent precise geochronometric data, revealed a complex P- T- t path for high-grade gneisses in a hitherto poorly understood sector of the Mesoproterozoic Maud Belt in East Antarctica. The Maud Belt is an extensive high-grade, polydeformed, metamorphic belt, which records two significant tectono-thermal episodes, once towards the end of the Mesoproterozoic and again towards the late Neoproterozoic/Cambrian. In contrast to previous models, most of the metamorphic mineral assemblages are related to a Pan-African tectono-thermal overprint, with only very few relics of late Mesoproterozoic granulite-facies mineral assemblages (M 1) left in strain-protected domains. Petrological and mineral chemical evidence indicates a clockwise P- T- t path for the Pan-African orogeny. Peak metamorphic (M 2b) conditions recorded by most rocks in the area ( T = 709-785 °C and P = 7.0-9.5 kbar) during the Pan-African orogeny were attained subsequent to decompression from probably eclogite-facies metamorphic conditions (M 2a). The new data acquired in this study, together with recent geochronological and geochemical data, permit the development of a geodynamic model for the Maud Belt that involves volcanic arc formation during the late Mesoproterozoic followed by extension at 1100 Ma and subsequent high-grade tectono-thermal reworking once during continent-continent collision at the end of the Mesoproterozoic (M 1; 1090-1030 Ma) and again during the Pan-African orogeny (M 2a, M 2b) between 565 and 530 Ma. Post-peak metamorphic K-metasomatism under amphibolite-facies conditions (M 2c) followed and is ascribed to post-orogenic bimodal magmatism between 500 and 480 Ma.

  8. Microbial trace fossils in Antarctica and the search for evidence of early life on Mars

    Science.gov (United States)

    Friedmann, E. Imre; Friedmann, Roseli O.

    1989-01-01

    It is possible to hypothesize that, if microbial life evolved on early Mars, fossil remnants of these organisms may be preserved on the surface. However, the cooling and drying of Mars probably resembled a cold desert and such an environment is not suitable for the process of fossilization. The frigid Ross Desert of Antarctica is probably the closest terrestrial analog to conditions that may have prevailed on the surface of the cooling and drying Mars. In this desert, cryptoendolithic microbial communities live in the airspaces of porous rocks, the last habitable niche in a hostile outside environment. The organisms produce characteristic chemical and physical changes in the rock substrate. Environmental changes (deterioration of conditions) may result in the death of the community. Although no cellular structures are fossilized, the conspicuous changes in the rock substrate are preserved as trace fossils. Likewise, microbial trace fossils (without cellular structures) may also be preserved on Mars: Discontinuities in structure or chemistry of the rock that are independent of physical or chemical gradients may be of biological origin. Ross Desert trace fossils can be used as a model for planning search strategies and for instrument design to find evidence of past Martian life.

  9. Spring phytoplankton onset after the ice break-up and sea-ice signature (Adélie Land, East Antarctica)

    OpenAIRE

    Riaux-Gobin, C.; Poulin, M.; Dieckmann, Gerhard; Labrune, C.; Vétion, G.

    2011-01-01

    The phytoplankton onset following the spring ice break-up in Adélie Land, East Antarctica, was studied along a short transect, from 400 m off the continent to 5 km offshore, during the austral summer of 2002. Eight days after the ice break-up, some large colonial and solitary diatom cells, known to be associated with land-fast ice and present in downward fluxes, were unable to adapt in ice-free waters, while some other solitary and short-colony forming taxa (e.g., Fragilariopsis curta, F. cyl...

  10. Trigonium curvatus sp nov and Trigonium arcticum (Bacillariophyceae) from the surface sediments of Prydz Bay, east Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Abhilash, N.; Mohan, R.; Shetye, S.; Gazi, S.; Jafar, S.A

    Here we propose a new species of genus Trigonium namely Trigonium curvatus from the surface sediments of coastal Antarctica A comparative study was done between Trigonium curvatus and Trigonium arcticum to find out the differential morphological...

  11. Inter-annual variability of surface ozone at coastal (Dumont d'Urville, 2004–2014 and inland (Concordia, 2007–2014 sites in East Antarctica

    Directory of Open Access Journals (Sweden)

    M. Legrand

    2016-07-01

    Full Text Available Surface ozone has been measured since 2004 at the coastal East Antarctic site of Dumont d'Urville (DDU, and since 2007 at the Concordia station located on the high East Antarctic plateau. This paper discusses long-term changes, seasonal and diurnal cycles, as well as inter-annual summer variability observed at these two East Antarctic sites. At Concordia, near-surface ozone data were complemented by balloon soundings and compared to similar measurements done at the South Pole. The DDU record is compared to those obtained at the coastal site of Syowa, also located in East Antarctica, as well as the coastal sites of Neumayer and Halley, both located on the coast of the Weddell Sea in West Antarctica. Surface ozone mixing ratios exhibit very similar seasonal cycles at Concordia and the South Pole. However, in summer the diurnal cycle of ozone is different at the two sites with a drop of ozone in the afternoon at Concordia but not at the South Pole. The vertical distribution of ozone above the snow surface also differs. When present, the ozone-rich layer located near the ground is better mixed and deeper at Concordia (up to 400 m than at the South Pole during sunlight hours. These differences are related to different solar radiation and wind regimes encountered at these two inland sites. DDU appears to be the coastal site where the impact of the late winter/spring bromine chemistry is the weakest, but where the impact of elevated ozone levels caused by NOx snow emissions from the high Antarctic plateau is the highest. The highest impact of the bromine chemistry is seen at Halley and Neumayer, and to a lesser extent at Syowa. These three sites are only weakly impacted by the NOx chemistry and the net ozone production occurring on the high Antarctic plateau. The differences in late winter/spring are attributed to the abundance of sea ice offshore from the sites, whereas those in summer are related to the topography of East Antarctica that promotes

  12. Layer-cake vs. fruit-cake stratigraphy of megadune-related snows of East Antarctica

    Science.gov (United States)

    Wise, D. U.; Cianfarra, P.; Salvini, F.

    2009-12-01

    Published models of snow deposits of the East Antarctic Plateau visualize km-scale snow stripes in scattered megadune fields as actively-forming stratigraphic zones growing through later Holocene time in parallel with other patches and zones of more normal snow and ice, in effect a stratigraphy of lumps scattered like fruit-cake “goodies.” An alternate four-unit layer-cake model seems more appropriate based on superposition relationships in satellite images. In this model the oldest unit (#1) contains upslope-climbing, relic megadune sets and cosets of pseudo-beds beneath the striped surfaces. This unit is transitional upward into unit #2, divisible into several facies: a) abandoned megadune plains or wind-swept snow regs to use a sand desert term, b) sudden appearance of high topographic relief “Duke of York” dunes from the children’s song of the Grand Old Duke’s soldiers abandoned “neither up nor down,” c) extensions of megadune snow stripes growing into downslope-migrating, lobate dunes, and d) downslope-migrating sheets of coalesced, mostly lobate dune forms, commonly lineated on regional scales. Unit #3 is a pile of snow blankets, transverse and longitudinal dunes that commonly form snow ergs, another sand desert term. This unit is semi-transparent to radar as indicted by near-surface trends and patterns on Modis images disappearing on radar images to show clearly defined unit #2 facies patterns for the same area. These three stratigraphic units appear analogous to an abbreviated form of the aqueous Bouma sequence of fining upward turbiditic beds that pass from upper flow regime (UFR), upstream-climbing antidunes through transitional units into lower flow regime (LFR), downstream-migrating dunes. If megadunes are UFR, very rapid deposition necessitated massive supplies of moisture-rich air available only from open water in the Ross and Weddell Seas or across narrow winter ice shelves of the Southern Ocean, a climate much warmer than present

  13. Is The East Antarctic Ice Sheet Stable? New Aerogeophysical Evidence from Terra Adelie

    Science.gov (United States)

    Durand, G.; Young, D. A.; Le Meur, E.; Blankenship, D. D.; Garcia-Aznar, P.

    2011-12-01

    Recently collected ice thickness data, collected as part of NASA's Operation Ice Bridge, provide insight into the sea level rise potential of the Terra Adelie/George V Land sector of East Antarctica. We compare the bedrock geometry unveiled over Ninnis Glacier and the ice streams feeding Cook Ice Shelf in this region to that of the major glaciers of West Antarctica. We find that many aspects of the bedrock geometry are comparable between the two regions. Rapid acceleration of West Antarctic's outlet glaciers and consequent ice loss (known as dynamic thinning) has been observed since the mid nineties. As a consequence, the West Antarctic Ice Sheet is out of balance and contributes increasingly to the current sea level rise. Due to West Antarctica's inward sloping bed geometry, continued and accelerating ice loss is predicted due to the effects of the Marine Ice Sheet Instability (MISI). Weertman [1974] suggested that marine terminated outlet glaciers may present an intrinsic instability when they rest over a seaward up-sloping bedrock. This principle was recently demonstrated in for the 2D flow line models and further confirmed through numerical investigations. The Amundsen sea sector of West Antarctica (more particularly Pine Island and Thwaites Glaciers) undergoes a significant increase of its grounded ice discharge along with grounding line retreats of up to tens of kilometers. Amongst the difficulties in forecasting the future ice sheet contribution to sea level is the determining whether the current shrinkage of West Antarctic glaciers can persist due to MISI. On the other hand, even if dynamical thinning has been recently observed over some outlets (particularly between 90° and 165° E), mass balance of East Antarctica seems currently to be in equilibrium. Due to that fact and to the vast scale of East Antarctica, surveys to determine bedrock elevation have received much less attention than West Antarctica, particularly in the Terra Adelie region. It is

  14. ICT Pathways to Poverty Reduction: Empirical Evidence from East ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    2014-01-14

    Jan 14, 2014 ... Information and communication technologies (ICTs) have been proven to promote economic growth, but do we know that ICTs reduce poverty? This book provides new empirical evidence on access to and use of ICTs and their effect on poor households in four East African countries: Kenya, Rwanda, ...

  15. ICT Pathways to Poverty Reduction : Empirical Evidence from East ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    14 janv. 2014 ... ICT Pathways to Poverty Reduction : Empirical Evidence from East and Southern Africa. Couverture du livre ICT Pathways to Poverty Reduction. Directeur(s) : Edith Ofwona Adera, Timothy M. Waema, Julian May, Ophelia Mascarenhas et Kathleen Diga. Maison(s) d'édition : Practical Action Publishing ...

  16. Spring phytoplankton onset after the ice break-up and sea-ice signature (Adélie Land, East Antarctica

    Directory of Open Access Journals (Sweden)

    Catherine Riaux-Gobin

    2011-01-01

    Full Text Available The phytoplankton onset following the spring ice break-up in Adélie Land, East Antarctica, was studied along a short transect, from 400 m off the continent to 5 km offshore, during the austral summer of 2002. Eight days after the ice break-up, some large colonial and solitary diatom cells, known to be associated with land-fast ice and present in downward fluxes, were unable to adapt in ice-free waters, while some other solitary and short-colony forming taxa (e.g., Fragilariopsis curta, F. cylindrus did develop. Pelagic species were becoming more abundant offshore, replacing the typical sympagic (ice-associated taxa. Archaeomonad cysts, usually associated with sea ice, were recorded in the surface waters nearshore. Rough weather restricted the data set, but we were able to confirm that some microalgae may be reliable sea-ice indicators and that seeding by sea ice only concerns a few taxa in this coastal area of East Antarctica.

  17. Sediment features at the grounding zone and beneath Ekström Ice Shelf, East Antarctica, imaged using on-ice vibroseis.

    Science.gov (United States)

    Smith, Emma C.; Eisen, Olaf; Hofstede, Coen; Lambrecht, Astrid; Mayer, Christoph

    2017-04-01

    The grounding zone, where an ice sheet becomes a floating ice shelf, is known to be a key threshold region for ice flow and stability. A better understanding of ice dynamics and sediment transport across such zones will improve knowledge about contemporary and palaeo ice flow, as well as past ice extent. Here we present a set of seismic reflection profiles crossing the grounding zone and continuing to the shelf edge of Ekström Ice Shelf, East Antarctica. Using an on-ice vibroseis source combined with a snowstreamer we have imaged a range of sub-glacial and sub-shelf sedimentary and geomorphological features; from layered sediment deposits to elongated flow features. The acoustic properties of the features as well as their morphology allow us to draw conclusions as to their material properties and origin. These results will eventually be integrated with numerical models of ice dynamics to quantify past and present interactions between ice and the solid Earth in East Antarctica; leading to a better understanding of future contributions of this region to sea-level rise.

  18. Geological controls on bedrock topography and ice sheet dynamics in the Wilkes Subglacial Basin sector of East Antarctica

    Science.gov (United States)

    Ferraccioli, Fausto; Armadillo, Egidio; Young, Duncan; Blankenship, Donald; Jordan, Tom; Siegert, Martin

    2017-04-01

    The Wilkes Subglacial Basin extends for 1,400 km into the interior of East Antarctica and hosts several major glaciers that drain a large sector of the East Antarctic Ice Sheet. The deep northern Wilkes Subglacial Basin underlies the catchments of the Matusevich, Cook, Ninnis and Mertz Glaciers, which are largely marine-based and hence potentially particularly sensitive to past and also predicted future ocean and climate warming. Sediment provenance studies suggest that the glaciers flowing in this region may have retreated significantly compared to their modern configuration, as recently as the warm mid-Pliocene interval, potentially contributing several m to global sea level rise (Cook et al.,Nature Geosci., 2013). Here we combine airborne radar, aeromagnetic and airborne gravity observations collected during the international WISE-ISODYN and ICECAP aerogeophysical campaigns with vintage datasets to help unveil subglacial geology and deeper crustal architecture and to assess its influence on bedrock topography and ice sheet dynamics in the northern Wilkes Subglacial Basin. Aeromagnetic images reveal that the Matusevich Glacier is underlain by a ca 480 Ma thrust fault system (the Exiles Thrust), which has also been inferred to have been reactivated in response to intraplate Cenozoic strike-slip faulting. Further to the west, the linear Eastern Basins are controlled by the Prince Albert Fault System. The fault system continues to the south, where it provides structural controls for both the Priestley and Reeves Glaciers. The inland Central Basins continue in the coastal area underlying the fast flowing Cook ice streams, implying that potential ocean-induced changes could propagate further into the interior of the ice sheet. We propose based on an analogy with the Rennick Graben that these deep subglacial basins are controlled by the underlying horst and graben crustal architecture. Given the interpreted subglacial distribution of Beacon sediments and Ferrar

  19. Bacterial and eukaryotic biodiversity patterns in terrestrial and aquatic habitats in the Sor Rondane Mountains, Dronning Maud Land, East Antarctica\

    Czech Academy of Sciences Publication Activity Database

    Obbels, D.; Verleyen, P.; Mano, M. J.; Namsaraev, Z.; Sweetlove, M.; Tytgat, B.; Fernandez-Carazo, R.; De Wever, A.; D'hondt, S.; Ertz, D.; Elster, Josef; Sabbe, K.; Willems, A.; Wilmotte, A.; Vyverman, W.

    2016-01-01

    Roč. 92, č. 6 (2016), s. 1-13, č. článku fiw041. ISSN 0168-6496 Institutional support: RVO:67985939 Keywords : Antarctica * terrestiral biodiversity * eukaryotes Subject RIV: EE - Microbiology, Virology Impact factor: 3.720, year: 2016

  20. Multichannel surface clutter suppression: East Antarctica P-band SAR ice sounding in the presence of grating lobes

    DEFF Research Database (Denmark)

    Bekaert, David; Gebert, Nicolas; Lin, Chung-Chi

    2014-01-01

    with the European Space Agency's P-band POLarimetric Airborne Radar Ice Sounder (POLARIS). The 4 m long antenna of POLARIS enables simultaneous reception of up to four across-track channels. It was operated in 2011 over Antarctica at a high flight altitude of 3200 m. Different coherent weighting techniques...

  1. Uplift and tilting of the Shackleton Range in East Antarctica driven by glacial erosion and normal faulting

    DEFF Research Database (Denmark)

    Paxman, Guy J. G.; Jamieson, Stewart S. R.; Ferraccioli, Fausto

    2017-01-01

    Unravelling the long-term evolution of the subglacial landscape of Antarctica is vital for understanding past ice sheet dynamics and stability, particularly in marine-based sectors of the ice sheet. Here we model the evolution of the bedrock topography beneath the Recovery catchment, a sector...

  2. Atmospheric circulation in the Indian Ocean sector of East Antarctica over the last 200 years according to chemical studies of snow‑firn cover

    Directory of Open Access Journals (Sweden)

    E. Yu. Osipov

    2017-01-01

    Full Text Available Spatial and temporal variability of a sea‑salt aerosol (Na+ concentration was investigated in snow‑firn cores and snow pits taken at four sites of the Indian Ocean sector of the East Antarctica (along a profile between stations Progress and Vostok: PV‑10, NVFL‑1, SW‑42, and the Vostok point. In long annually resolved Na+ records, we had revealed the following periodicities: 17 to 95‑year (Vostok and 29 to 52‑year (NVFL‑1, while the shorter records are characterized by 8‑year periodicity. The Na+ concentrations decrease as the snow accu‑ mulation increases (especially, at the Vostok station, and this is evidence for a presence of «dilution effect» in the sites with the great part of «dry precipitation». The closest relationship was revealed between changes in flows of Na+ at points SW‑42, and PV‑10. Variability of the Na+ fluxes had been linked to the circulation indices (AAO, PDO, SOI, MEI, SPO and the sea level pressure in the Southern Hemisphere, as well as to occurrence of Elementary Circulation Mechanisms (ECM. The revealed irregularity of the Na+ precipitation over the area under investigation is caused by different atmospheric circulation patterns as well as by influ‑ ence of basic Action Centers of the Atmosphere (ACA in the Southern Hemisphere. The closest relationship is found to take place with South Pacific ACA (Vostok, 1976–2009 and with the South Indian ACA (SW‑42 and PV‑10. A presence of distant atmospheric relations (including one with El Nino had been revealed for the inland areas. Changes in features of the atmospheric circulation in the South Indian Ocean over the last 200‑year period have been reconstructed on the basis of summarized Na+ records from the Vostok station area. Distinctive feature of the atmospheric circulation is the 40‑year periodicity with its increasing intensity during the following periods: 1805–1820, 1830–1860, 1890–1900, 1940–1950, and 1980–2000. In

  3. Characteristic Surface Processes Between Atmosphere, Cryosphere and Oceanic Environment Inferred from Infrasound Array Observations in Lützow-Holm Bay, East Antarctica

    Science.gov (United States)

    Ishihara, Y.; Kanao, M.; Yamamoto, M. Y.; Kakinami, Y.; Murayama, T.; Okada, K.; Toda, S.; Matsushima, T.

    2014-12-01

    Infrasound is sub-audible sound whose frequency range is about 3 mHz to 20 Hz. Because this frequency is common between atmospheric, oceanic and solid earth vibrations, those waves are interacting with each other and interaction itself generates infrasound. At polar region, cryosphere also play an important role for generation and propagation of infrasound. The Japanese Antarctic infrasound observation started at April 2008. A sensor was installed at Syowa Station (SYO) in Lützow-Holm Bay (LHB) of East Antarctica, as a part of the International Polar Year. Characteristic infrasound waves observed at SYO demonstrate physical interaction involving environmental changes in the Antarctic region. Continuous recordings of infrasound clearly indicate existence of the hums generated by ocean-atmosphere interaction (microbaroms) with peaks of 0.1 to 0.25 Hz. Because larger amount of sea-ice extending around the LHB near SYO suppress ocean wave, the microbaroms become weak during austral winter. Following success of pilot observation, in austral summer in 2013, we extended one-sensor observation at SYO to 3-sensor arrayed observations, and installed a few field stations along the coast of the LHB. Newly established SYO array clearly detected the propagating directions and frequency contents of the microbaroms from Southern Ocean. In addition, we found harmonic signals around lowermost human audible band, however, currently unclear how and what generating hamonic signals. Those signals are recorded under windy condition. Since our system has no mechanical resonance at those frequency ranges, we speculate that the characteristic harmonic signals are probably related to local surficial phenomena such as ice sheet vibration generated by katabatic winds. Infrasound measurement at Antarctica could be a new proxy for monitoring a regional environmental change in high southern latitude. In such point of view, we will continue and improve the observations at and around SYO

  4. Accumulation variability over a small area in east Dronning Maud Land, Antarctica, as determined from shallow firn cores and snow pits: some implications for ice-core records

    Science.gov (United States)

    Karlöf, Lars; Isaksson, Elisabeth; Winther, Jan-Gunnar; Gundestrup, Niels; Meijer, Harro A. J.; Mulvaney, Robert; Pourchet, Michel; Hofstede, Coen; Lappegard, Gaute; Pettersson, Rickard; van den Broeke, Michiel; van de Wal, Roderik S. W.

    We investigate and quantify the variability of snow accumulation rate around a medium-depth firn core (160 m) drilled in east Dronning Maud Land, Antarctica (75°00‧S, 15°00‧E; 3470 m h.a.e. (ellipsoidal height)). We present accumulation data from five snow pits and five shallow (20 m) firn cores distributed within a 3.5 7 km distance, retrieved during the 2000/01 Nordic EPICA (European Project for Ice Coring in Antarctica) traverse. Snow accumulation rates estimated for shorter periods show higher spatial variance than for longer periods. Accumulation variability as recorded from the firn cores and snow pits cannot explain all the variation in the ion and isotope time series; other depositional and post-depositional processes need to be accounted for. Through simple statistical analysis we show that there are differences in sensitivity to these processes between the analyzed species. Oxygen isotopes and sulphate are more conservative in their post-depositional behaviour than the more volatile acids, such as nitrate and to some degree chloride and methanesulphonic acid. We discuss the possible causes for the accumulation variability and the implications for the interpretation of ice-core records.

  5. Diversity of Phototrophic Genes Suggests Multiple Bacteria May Be Able to Exploit Sunlight in Exposed Soils from the Sør Rondane Mountains, East Antarctica

    Directory of Open Access Journals (Sweden)

    Guillaume Tahon

    2016-12-01

    Full Text Available Microbial life in exposed terrestrial surface layers in continental Antarctica is faced with extreme environmental conditions, including scarcity of organic matter. Bacteria in these exposed settings can therefore be expected to use alternative energy sources such as solar energy, abundant during the austral summer. Using Illumina MiSeq sequencing, we assessed the diversity and abundance of four conserved protein encoding genes involved in different key steps of light-harvesting pathways dependent on (bacteriochlorophyll (pufM, bchL/chlL and bchX genes and rhodopsins (actinorhodopsin genes, in exposed soils from the Sør Rondane Mountains, East Antarctica. Analysis of pufM genes, encoding a subunit of the type 2 photochemical reaction center found in anoxygenic phototrophic bacteria, revealed a very broad diversity, dominated by Roseobacter- and Loktanella-like sequences. The bchL and chlL, involved in (bacteriochlorophyll synthesis, on the other hand, showed a high abundance of either cyanobacterial or green algal trebouxiophyceael chlL reads, depending on the sample, while most bchX sequences belonged mostly to previously unidentified phylotypes. Rhodopsin-containing phototrophic bacteria could not be detected in the samples. Our results, while suggesting that Cyanobacteria and green algae are the main phototrophic groups, show that light-harvesting bacteria are nevertheless very diverse in microbial communities in Antarctic soils.

  6. Comparison of the Microbial Diversity and Abundance Between the Freshwater Land-Locked Lakes of Schirmacher Oasis and the Perennially Ice-Covered Lake Untersee in East Antarctica

    Science.gov (United States)

    Huang, Jonathan; Hoover, Richard B.; Swain, Ashit; Murdock, Chris; Bej, Asim K.

    2010-01-01

    Extreme conditions such as low temperature, dryness, and constant UV-radiation in terrestrial Antarctica are limiting factors of the survival of microbial populations. The objective of this study was to investigate the microbial diversity and enumeration between the open water lakes of Schirmacher Oasis and the permanently ice-covered Lake Untersee. The lakes in Schirmacher Oasis possessed abundant and diverse group of microorganisms compared to the Lake Untersee. Furthermore, the microbial diversity between two lakes in Schirmacher Oasis (Lake L27C and L47) was compared by culture-based molecular approach. It was determined that L27Chad a richer microbial diversity representing 5 different phyla and 7 different genera. In contrast L47 consisted of 4 different phyla and 6 different genera. The difference in microbial community could be due to the wide range of pH between L27C (pH 9.1) and L47 (pH 5.7). Most of the microbes isolated from these lakes consisted of adaptive biological pigmentation. Characterization of the microbial community found in the freshwater lakes of East Antarctica is important because it gives a further glimpse into the adaptation and survival strategies found in extreme conditions.

  7. Refined broad-scale sub-glacial morphology of Aurora Subglacial Basin, East Antarctica derived by an ice-dynamics-based interpolation scheme

    Directory of Open Access Journals (Sweden)

    J. L. Roberts

    2011-07-01

    Full Text Available Ice thickness data over much of East Antarctica are sparse and irregularly distributed. This poses difficulties for reconstructing the homogeneous coverage needed to properly assess underlying sub-glacial morphology and fundamental geometric constraints on sea level rise. Here we introduce a new physically-based ice thickness interpolation scheme and apply this to existing ice thickness data in the Aurora Subglacial Basin region. The skill and robustness of the new reconstruction is demonstrated by comparison with new data from the ICECAP project. The interpolated morphology shows an extensive marine-based ice sheet, with considerably more area below sea-level than shown by prior studies. It also shows deep features connecting the coastal grounding zone with the deepest regions in the interior. This has implications for ice sheet response to a warming ocean and underscores the importance of obtaining additional high resolution data in these marginal zones for modelling ice sheet evolution.

  8. Changes in water properties and flow regime on the continental shelf off the Adélie/George V Land coast, East Antarctica, after glacier tongue calving

    Science.gov (United States)

    Aoki, S.; Kobayashi, R.; Rintoul, S. R.; Tamura, T.; Kusahara, K.

    2017-08-01

    Oceanic changes before and after the relocation of iceberg B9B and calving of the Mertz Glacier Tongue (MGT) in February 2010 are examined on the continental shelf off the Adélie Land/George V Land coast, East Antarctica. Summer hydrographic observations, including stable oxygen isotope ratio (δ18O), in 2001/2008 and 2011/2015 and results of a numerical model are used. Along the western flank of the MGT, temperature decreased between 2001 and 2015 for most of the water column in the Adélie Depression. δ18O generally decreased, especially at the MGT draft depths on the northern side. West of the MGT, temperature, salinity, and δ18O decreased in the intermediate layer. East of the MGT, in contrast, temperature increased between 2001 and 2011 at intermediate depths, salinity increased in the intermediate and deep layers, and δ18O slightly decreased in the deep layer but did not change much around 300 dbar. The numerical experiment exhibits a change in ocean circulation, revealing an increase in modified Circumpolar Deep Water (mCDW) inflow in the east and a decrease in the west. The contrasting changes in mCDW intrusion are consistent between the observations and numerical model, and are indicative of the effect of removal of the ice barriers. The contrast is overlain by overall decreases in salinity and δ18O, which suggests an increase in the continental meltwater fraction of 5-20% and might reveal a wide-ranging influence from West Antarctica. The oxygen isotope ratio is, hence, effective in monitoring the increase in continental melt over the Antarctic shelf.Plain Language SummaryAntarctic glaciers, icebergs, and ice sheet have significant impact on the surrounding ocean, and, in turn, are affected by the ocean. The Mertz Glacier, East Antarctica, had been melted from below by the oceanic heat. The seaward extension of the glacier of about 500 m tall obstructed sea ice drift from the east and enabled a large amount of sea ice production there. Dense water

  9. Evidence of Pliocene Nothofagus in Antarctica from Pliocene marine sedimentary deposits (DSDP Site 274)

    Science.gov (United States)

    Fleming, R.F.; Barron, J.A.

    1996-01-01

    Microfossil assemblages in Pliocene sediments from DSDP Site 274 (68??59.81???S, 173??25.64???E) provide data on the age of the sediments and suggest the presence of Nothofagus (southern beech) in Antarctica during the Pliocene. A suite of 17 samples was collected in an interval from Samples 28-274-6R-1, 83-87 cm to 28-274-11R-4, 73-77 cm (48.33-100.29 mbsf). Biostratigraphic study of the abundant diatom assemblages combined with published radiolarian data indicates that the sample interval ranges in age from 5.0 to 2.2 Ma, with an apparent unconformity between about 3.8 and 3.2 Ma. Nothofagidites (the genus for fossil pollen referable to Nothofagus) occurs throughout the interval, as well as pollen and spores with known stratigraphic ranges that unequivocally indicate reworking from older rocks. Species of Nothofagidites recovered include N. asperus, N. brachyspinulosus, N. flemingii, N. senectus, and N. sp. cf. N. lachlaniae; the latter form is previously known from the Sirius Group in the Transantarctic Mountains. Abundant palynomorphs were recovered in only three of the samples from Site 274 (Samples 28-274-9R-2, 15-19 cm; 28-274-9R-2, 48-52 cm; and 28-274-9R-2, 65-69 cm). Based on the diatom and radiolarian biostratigraphic data, the ages of these samples range from 3.00 to 3.01 Ma. The relative abundance of N. sp. cf. N. lachlaniae in the three samples is an order of magnitude higher than relative abundances for the other species of Nothofagidites in the same samples. The significantly higher relative abundance of N. sp. cf. N. lachlaniae suggests that this pollen was derived from trees of Nothofagus that were living in Antarctica during the mid Pliocene. Diatom assemblages from these three samples indicate that sediments in this interval were rapidly deposited as biogenic oozes in an open-ocean setting relatively free of sea ice, thus decreasing the possibility of reworking from a single source bed rich in N. sp. cf. N. lachlaniae. Clearly, more detailed

  10. Evidence of the 2011 Puyehue-Córdon Caulle Eruption in West Antarctica

    Science.gov (United States)

    Dowd, E.; Koffman, B. G.; Ferris, D. G.; Osterberg, E. C.; Wong, G. J.; Kreutz, K. J.

    2016-12-01

    Gases and aerosols emitted during volcanic eruptions can have widespread impacts, including global climate cooling, disruption to air travel, and a reduction in air quality. Ice core records offer highly temporally resolved archives of past volcanic eruptions, allowing for precise tephrostratigraphy as well as estimates of past volcanic impacts on Earth's radiative balance. Previous work in West Antarctica has shown that the latitude and/or magnitude of past eruptions can be inferred on the basis of changes in particle size distributions (PSDs) relative to background dust, as well as phasing between ash particle and sulfate aerosol deposition. Specifically, explosive tropical eruptions show finer-than-background PSDs and clear phasing between (earlier) ash and (later) sulfate deposition, while high-latitude eruptions exhibit coarser-than-background PSDs. In order to assess the depositional characteristics of a mid-latitude eruption for comparison with these earlier observations, we evaluated the June 4-6, 2011 VEI 5 eruption of Puyehue-Córdon Caulle, Chile (40.59°S). Satellite imagery shows the ash cloud from the eruption passing directly over central West Antarctica, suggesting that ash particle deposition may have occurred. We collected surface snow samples from the West Antarctic Ice Sheet (WAIS) Divide field camp in January 2012 and analyzed them for major ion concentrations and particle concentration and size distribution using ion chromatographs and a Coulter-Counter, respectively. The annually resolved snowpit record, which extends to June 2009, does not have elevated sulfate concentrations linked with the Puyehue eruption. However, particle analyses indicate that ash deposition did occur, with ash particles coarser than background dust (>12 μm diameter vs. modal diameter of 5 μm). The coarseness of ash particles, similar to those from high-latitude eruptions, is consistent with tropospheric transport. On the basis of these results, we suggest that mid

  11. Evidence for a dynamic East Antarctic ice sheet during the mid-Miocene climate transition

    Science.gov (United States)

    Pierce, Elizabeth L.; van de Flierdt, Tina; Williams, Trevor; Hemming, Sidney R.; Cook, Carys P.; Passchier, Sandra

    2017-11-01

    The East Antarctic ice sheet underwent a major expansion during the Mid-Miocene Climate Transition, around 14 Ma, lowering sea level by ∼60 m. However, direct or indirect evidence of where changes in the ice sheet occurred is limited. Here we present new insights on timing and locations of ice sheet change from two drill sites offshore East Antarctica. IODP Site U1356, Wilkes Land, and ODP Site 1165, Prydz Bay are located adjacent to two major ice drainage areas, the Wilkes Subglacial Basin and the Lambert Graben. Ice-rafted detritus (IRD), including dropstones, was deposited in concentrations far exceeding those known in the rest of the Miocene succession at both sites between 14.1 and 13.8 Ma, indicating that large amounts of IRD-bearing icebergs were calved from independent drainage basins during this relatively short interval. At Site U1356, the IRD was delivered in distinct pulses, suggesting that the overall ice advance was punctuated by short periods of ice retreat in the Wilkes Subglacial Basin. Provenance analysis of the mid-Miocene IRD and fine-grained sediments provides additional insights on the movement of the ice margin and subglacial geology. At Site U1356, the dominant 40Ar/39Ar thermochronological age of the ice-rafted hornblende grains is 1400-1550 Ma, differing from the majority of recent IRD in the area, from which we infer an inland source area of this thermochronological age extending along the eastern part of the Adélie Craton, which forms the western side of the Wilkes Subglacial Basin. Neodymium isotopic compositions from the terrigenous fine fraction at Site U1356 imply that the ice margin periodically expanded from high ground well into the Wilkes Subglacial Basin during periods of MMCT ice growth. At Site 1165, MMCT pebble-sized IRD are sourced from both the local Lambert Graben and the distant Aurora Subglacial Basin drainage area. Together, the occurrence and provenance of the IRD and glacially-eroded sediment at these two marine

  12. A Combined Observational and Modeling Approach to Study Modern Dust Transport from the Patagonia Desert to East Antarctica

    Science.gov (United States)

    Gasso, S.; Stein, A.; Marino, F.; Castellano, E.; Udisti, R.; Ceratto, J.

    2010-01-01

    The understanding of present atmospheric transport processes from Southern Hemisphere (SH) landmasses to Antarctica can improve the interpretation of stratigraphic data in Antarctic ice cores. In addition, long range transport can deliver key nutrients normally not available to marine ecosystems in the Southern Ocean and may trigger or enhance primary productivity. However, there is a dearth of observational based studies of dust transport in the SH. This work aims to improve current understanding of dust transport in the SH by showing a characterization of two dust events originating in the Patagonia desert (south end of South America). The approach is based on a combined and complementary use of satellite retrievals (detectors MISR, MODIS, GLAS ,POLDER, OMI,), transport model simulation (HYSPLIT) and surface observations near the sources and aerosol measurements in Antarctica (Neumayer and Concordia sites). Satellite imagery and visibility observations confirm dust emission in a stretch of dry lakes along the coast of the Tierra del Fuego (TdF) island (approx.54deg S) and from the shores of the Colihue Huapi lake in Central Patagonia (approx.46deg S) in February 2005. Model simulations initialized by these observations reproduce the timing of an observed increase in dust concentration at the Concordia Station and some of the observed increases in atmospheric aerosol absorption (here used as a dust proxy) in the Neumayer station. The TdF sources were the largest contributors of dust at both sites. The transit times from TdF to the Neumayer and Concordia sites are 6-7 and 9-10 days respectively. Lidar observations and model outputs coincide in placing most of the dust cloud in the boundary layer and suggest significant de- position over the ocean immediately downwind. Boundary layer dust was detected as far as 1800 km from the source and approx.800 km north of the South Georgia Island over the central sub-Antarctic Atlantic Ocean. Although the analysis suggests the

  13. A combined observational and modeling approach to study modern dust transport from the Patagonia desert to East Antarctica

    Directory of Open Access Journals (Sweden)

    S. Gassó

    2010-09-01

    Full Text Available The understanding of present atmospheric transport processes from Southern Hemisphere (SH landmasses to Antarctica can improve the interpretation of stratigraphic data in Antarctic ice cores. In addition, long range transport can deliver key nutrients normally not available to marine ecosystems in the Southern Ocean and may trigger or enhance primary productivity. However, there is a dearth of observational based studies of dust transport in the SH.

    This work aims to improve current understanding of dust transport in the SH by showing a characterization of two dust events originating in the Patagonia desert (south end of South America. The approach is based on a combined and complementary use of satellite retrievals (detectors MISR, MODIS, GLAS, POLDER, OMI, transport model simulation (HYSPLIT and surface observations near the sources and aerosol measurements in Antarctica (Neumayer and Concordia sites.

    Satellite imagery and visibility observations confirm dust emission in a stretch of dry lakes along the coast of the Tierra del Fuego (TdF island (~54° S and from the shores of the Colihue Huapi lake in Central Patagonia (~46° S in February 2005. Model simulations initialized by these observations reproduce the timing of an observed increase in dust concentration at the Concordia Station and some of the observed increases in atmospheric aerosol absorption (here used as a dust proxy in the Neumayer station. The TdF sources were the largest contributors of dust at both sites. The transit times from TdF to the Neumayer and Concordia sites are 6–7 and 9–10 days respectively. Lidar observations and model outputs coincide in placing most of the dust cloud in the boundary layer and suggest significant deposition over the ocean immediately downwind. Boundary layer dust was detected as far as 1800 km from the source and ~800 km north of the South Georgia Island over the central sub-Antarctic Atlantic Ocean. Although the analysis

  14. A combined observational and modeling approach to study modern dust transport from the Patagonia desert to East Antarctica

    Science.gov (United States)

    Gassó, S.; Stein, A.; Marino, F.; Castellano, E.; Udisti, R.; Ceratto, J.

    2010-09-01

    The understanding of present atmospheric transport processes from Southern Hemisphere (SH) landmasses to Antarctica can improve the interpretation of stratigraphic data in Antarctic ice cores. In addition, long range transport can deliver key nutrients normally not available to marine ecosystems in the Southern Ocean and may trigger or enhance primary productivity. However, there is a dearth of observational based studies of dust transport in the SH. This work aims to improve current understanding of dust transport in the SH by showing a characterization of two dust events originating in the Patagonia desert (south end of South America). The approach is based on a combined and complementary use of satellite retrievals (detectors MISR, MODIS, GLAS, POLDER, OMI), transport model simulation (HYSPLIT) and surface observations near the sources and aerosol measurements in Antarctica (Neumayer and Concordia sites). Satellite imagery and visibility observations confirm dust emission in a stretch of dry lakes along the coast of the Tierra del Fuego (TdF) island (~54° S) and from the shores of the Colihue Huapi lake in Central Patagonia (~46° S) in February 2005. Model simulations initialized by these observations reproduce the timing of an observed increase in dust concentration at the Concordia Station and some of the observed increases in atmospheric aerosol absorption (here used as a dust proxy) in the Neumayer station. The TdF sources were the largest contributors of dust at both sites. The transit times from TdF to the Neumayer and Concordia sites are 6-7 and 9-10 days respectively. Lidar observations and model outputs coincide in placing most of the dust cloud in the boundary layer and suggest significant deposition over the ocean immediately downwind. Boundary layer dust was detected as far as 1800 km from the source and ~800 km north of the South Georgia Island over the central sub-Antarctic Atlantic Ocean. Although the analysis suggests the presence of dust at

  15. Evidence for the former existence of a thicker ice sheet on the Vestfjella nunataks in western Dronning Maud Land, Antarctica

    Directory of Open Access Journals (Sweden)

    Lintinen, P.

    1996-06-01

    Full Text Available Vestfjella (73-74°S, 13-16°W is a 130 km long nunatak range in western Dronning Maud Land in East Antarctica, and its northern and southern ends are situated close to the present ice sheet grounding-line. Striations and lodgement till on nunatak Basen indicate that the northernmost Vestfjella nunataks were formerly covered by a thicker Antarctic ice sheet. Striations on the summit ridge of nunatak Plogen indicate that the minimum change in ice thickness has been 700 m at the present ice sheet grounding-line. The relatively uniform oldest striation direction on different nunatak summits and the altitude of Plogen, which is less than 200 m lower than the highest Vestfjella summits, indicates that the whole of Vestfjella may have been covered by an ice sheet. Oxidation of till surface stones and an increased clay fraction in the upper part of the till layer were the only indications of soil formation on Basen. The unweathered nature of the Basen lodgement till indicate a relatively young age for deglaciation. This conclusion is also supported by age determinations and sedimentological data obtained from Weddell Sea sediments by Norwegian researchers, suggesting that a grounded ice sheet extended to the shelf edge at around 21 ka B.P. However the age of the glaciation which covered Basen and Plogen and the subsequent deglaciation is not based on precise dates and therefore the late Wisconsinan/Weichselian age is only a working hypothesis.

  16. Measurements of precipitation in Dumont d'Urville, Adélie Land, East Antarctica

    Directory of Open Access Journals (Sweden)

    J. Grazioli

    2017-08-01

    Full Text Available The first results of a campaign of intensive observation of precipitation in Dumont d'Urville, Antarctica, are presented. Several instruments collected data from November 2015 to February 2016 or longer, including a polarimetric radar (MXPol, a Micro Rain Radar (MRR, a weighing gauge (Pluvio2, and a Multi-Angle Snowflake Camera (MASC. These instruments collected the first ground-based measurements of precipitation in the region of Adélie Land (Terre Adélie, including precipitation microphysics. Microphysical observations during the austral summer 2015/2016 showed that, close to the ground level, aggregates are the dominant hydrometeor type, together with small ice particles (mostly originating from blowing snow, and that riming is a recurring process. Eleven percent of the measured particles were fully developed graupel, and aggregates had a mean riming degree of about 30 %. Spurious precipitation in the Pluvio2 measurements in windy conditions, leading to phantom accumulations, is observed and partly removed through synergistic use of MRR data. The yearly accumulated precipitation of snow (300 m above ground, obtained by means of a local conversion relation of MRR data, trained on the Pluvio2 measurement of the summer period, is estimated to be 815 mm of water equivalent, with a confidence interval ranging between 739.5 and 989 mm. Data obtained in previous research from satellite-borne radars, and the ERA-Interim reanalysis of the European Centre for Medium-Range Weather Forecasts (ECMWF provide lower yearly totals: 655 mm for ERA-Interim and 679 mm for the climatological data over DDU. ERA-Interim overestimates the occurrence of low-intensity precipitation events especially in summer, but it compensates for them by underestimating the snowfall amounts carried by the most intense events. Overall, this paper provides insightful examples of the added values of precipitation monitoring in Antarctica with a synergistic use of in situ

  17. Upward continuation of Dome-C airborne gravity and comparison with GOCE gradients at orbit altitude in east Antarctica

    DEFF Research Database (Denmark)

    Yildiz, Hasan; Forsberg, René; Tscherning, Carl Christian

    2017-01-01

    spherical harmonic models confirmed the quality of the airborne data and that they contain more high-frequency signal than the global models. First, the airborne gravity data were upward continued to GOCE altitude to predict gravity gradients in the local North-East-Up reference frame. In this step...

  18. Multiple gene evidence for expansion of extant penguins out of Antarctica due to global cooling.

    Science.gov (United States)

    Baker, Allan J; Pereira, Sergio Luiz; Haddrath, Oliver P; Edge, Kerri-Anne

    2006-01-07

    Classic problems in historical biogeography are where did penguins originate, and why are such mobile birds restricted to the Southern Hemisphere? Competing hypotheses posit they arose in tropical-warm temperate waters, species-diverse cool temperate regions, or in Gondwanaland approximately 100 mya when it was further north. To test these hypotheses we constructed a strongly supported phylogeny of extant penguins from 5851 bp of mitochondrial and nuclear DNA. Using Bayesian inference of ancestral areas we show that an Antarctic origin of extant taxa is highly likely, and that more derived taxa occur in lower latitudes. Molecular dating estimated penguins originated about 71 million years ago in Gondwanaland when it was further south and cooler. Moreover, extant taxa are inferred to have originated in the Eocene, coincident with the extinction of the larger-bodied fossil taxa as global climate cooled. We hypothesize that, as Antarctica became ice-encrusted, modern penguins expanded via the circumpolar current to oceanic islands within the Antarctic Convergence, and later to the southern continents. Thus, global cooling has had a major impact on penguin evolution, as it has on vertebrates generally. Penguins only reached cooler tropical waters in the Galapagos about 4 mya, and have not crossed the equatorial thermal barrier.

  19. Stratigraphic calibration of Oligocene-Miocene organic-walled dinoflagellate cysts from offshore Wilkes Land, East Antarctica, and a zonation proposal

    Science.gov (United States)

    Bijl, Peter K.; Houben, Alexander J. P.; Bruls, Anja; Pross, Jörg; Sangiorgi, Francesca

    2018-01-01

    There is growing interest in the scientific community in reconstructing the paleoceanography of the Southern Ocean during the Oligocene-Miocene because these time intervals experienced atmospheric CO2 concentrations with relevance to our future. However, it has remained notoriously difficult to put the sedimentary archives used in these efforts into a temporal framework. This is at least partially due to the fact that the bio-events recorded in organic-walled dinoflagellate cysts (dinocysts), which often represent the only microfossil group preserved, have not yet been calibrated to the international timescale. Here we present dinocyst ranges from Oligocene-Miocene sediments drilled offshore the Wilkes Land continental margin, East Antarctica (Integrated Ocean Drilling Program (IODP) Hole U1356A). In addition, we apply statistical means to test a priori assumptions about whether the recorded taxa were deposited in situ or were reworked from older strata. Moreover, we describe two new dinocyst species, Selenopemphix brinkhuisii sp. nov. and Lejeunecysta adeliensis sp. nov., which are identified as important markers for regional stratigraphic analysis. Finally, we calibrate all identified dinocyst events to the international timescale using independent age control from calcareous nanoplankton and magnetostratigraphy from IODP Hole U1356A, and we propose a provisional dinoflagellate cyst zonation scheme for the Oligocene-Miocene of the Southern Ocean.

  20. Effect of UV-B radiation on UV absorbing compounds and pigments of moss and lichen of Schirmacher oasis region, East Antarctica.

    Science.gov (United States)

    Singh, J; Gautam, S; Bhushan Pant, A

    2012-12-22

    The survival of Antarctic flora under ozone depletion depends on their ability to acclimate against increasing UV—B radiation by employing photo protective mechanisms either by avoiding or repairing UV—B damage. A fifteen days experiment was designed to study moss (Bryum argenteum) and lichen (Umbilicaria aprina) under natural UV—B exposure and under UV filter frames at the Maitri region of Schirmacher oasis, East Antarctica. Changes in UV absorbing compounds, phenolics, carotenoids and chlorophyll content were studied for continuous fifteen days and significant changes were observed in the UV exposed plants of B. argenteum and U. aprina. The change in the UV absorbing compounds was more significant in B. argenteum (P<0.0001) than U. aprina (P<0.0002). The change in phenolic contents and total carotenoid content was significant (P<0.0001) in both B. argenteum and lichen U. aprina indicating that the increase in UV absorbing compounds, phenolic contents and total carotenoid content act as a protective mechanism against the deleterious effect of UV—B radiations.

  1. Community structure of copepods in the oceanic and neritic waters off Adélie and George V Land, East Antarctica, during the austral summer of 2008

    Science.gov (United States)

    Tachibana, Aiko; Watanabe, Yuko; Moteki, Masato; Hosie, Graham W.; Ishimaru, Takashi

    2017-06-01

    Copepods are one of the most important components of the Southern Ocean food web, and are widely distributed from surface to deeper waters. We conducted discrete depth sampling to clarify the community structure of copepods from the epi- to bathypelagic layers of the oceanic and neritic waters off Adélie and George V Land, East Antarctica, in the austral summer of 2008. Notably high diversity and species numbers were observed in the meso- and bathypelagic layers. Cluster analysis based on the similarity of copepod communities identified seven cluster groups, which corresponded well with water masses. In the epi- and upper- mesopelagic layers of the oceanic zone, the SB (Southern Boundary of the Antarctic Circumpolar Current) divided copepod communities. Conversely, in the lower meso- and bathypelagic layers (500-2000 m depth), communities were consistent across the SB. In these layers, the distributions of copepod species were separated by habitat depth ranges and feeding behaviour. The different food webs occur in the epipelagic layer with habitat segregation by zooplankton in their horizontal distribution ranges.

  2. Fractionation distribution and preliminary ecological risk assessment of As, Hg and Cd in ornithogenic sediments from the Ross Sea region, East Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Lou, Chuangneng [Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026 (China); Liu, Xiaodong, E-mail: ycx@ustc.edu.cn [Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026 (China); Nie, Yaguang [Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026 (China); Emslie, Steven D. [Department of Biology and Marine Biology, University of North Carolina Wilmington, 601S. College Road, Wilmington, NC 28403 (United States)

    2015-12-15

    To evaluate mobility of toxic elements and their potential ecological risk caused by seabird biovectors, the fractionation distributions of arsenic (As), mercury (Hg) and cadmium (Cd) were investigated in three ornithogenic sediment profiles from the Ross Sea region, East Antarctica. The results show residual As holds a dominant position, and Hg mainly derives from residual, organic matter-bound and humic acid-bound fractions, indicating weak mobility of As and Hg. However, exchangeable Cd occupies a considerable proportion in studied samples, suggesting Cd has strong mobility. The preliminary evaluation of Sediment Quality Guidelines (SGQs) shows adverse biological effects may occur occasionally for As and Cd, and rarely for Hg. Using Risk Assessment Code (RAC), the ecological risk is assessed at moderate, low and very high for As, Hg and Cd pollution, respectively. Organic matter derived from guano is the main factor controlling the mobility of Hg and Cd through adsorption and complexation. - Highlights: • Residual As holds a dominant position in ornithogenic sediments. • Hg mainly derives from residual, organic matter-bound and humic acid-bound fractions. • Exchangeable Cd occupies a considerable proportion in ornithogenic sediments. • TOC is the main factor controlling the mobility of Hg and Cd in studied sediments.

  3. Formation processes of sea ice floe size distribution in the interior pack and its relationship to the marginal ice zone off East Antarctica

    Science.gov (United States)

    Toyota, Takenobu; Kohout, Alison; Fraser, Alexander D.

    2016-09-01

    To understand the behavior of the Seasonal Ice Zone (SIZ), which is composed of sea-ice floes of various sizes, knowledge of the floe size distribution (FSD) is important. In particular, FSD in the Marginal Ice Zone (MIZ), controlled by wave-ice interaction, plays an important role in determining the retreating rates of sea-ice extent on a global scale because the cumulative perimeter of floes enhances melting. To improve the understanding of wave-ice interaction and subsequent effects on FSD in the MIZ, FSD measurements were conducted off East Antarctica during the second Sea Ice Physics and Ecosystems eXperiment (SIPEX-2) in late winter 2012. Since logistical reasons limited helicopter operations to two interior ice regions, FSD in the interior ice region was determined using a combination of heli-photos and MODIS satellite visible images. The possible effect of wave-ice interaction in the MIZ was examined by comparison with past results obtained in the same MIZ, with our analysis showing: (1) FSD in the interior ice region is basically scale invariant for both small- (1 km) scale regimes; (2) although fractal dimensions are quite different between these two regimes, they are both rather close to that in the MIZ; and (3) for floes pack.

  4. Colonization, succession, and extinction of marine floras during a glacial cycle: A case study from the Windmill Islands (east Antarctica) using biomarkers

    Science.gov (United States)

    Hodgson, Dominic A.; McMinn, Andrew; Kirkup, Helen; Cremer, Holger; Gore, Damian; Melles, Martin; Roberts, Donna; Montiel, Pedro

    2003-09-01

    With the exception of the diatoms, little is known of the extinction, colonization, and succession of marine floras during glacial cycles. Here we study both morphological and biochemical fossils in two sediment cores from the Antarctic to unravel the sequence of events over a single glacial cycle. The cores, from the nearshore continental shelf off the Windmill Islands (66°S, 110°E), east Antarctica, span the period from Marine Isotope Stage 3 or earlier to the present. New high-performance liquid chromatography and mass spectrometry methods were used to study fossil pigments with additional data from siliceous microfossils, lithological analyses, and radiocarbon dates. Results show two response processes. First, there is the large-scale impact of the expanding ice sheet in removing the flora from the inner shelf, primarily through the denial of light, destabilization of the substratum, and elimination of habitats. Second, there are a number of glacial climate interactions that have a surprisingly strong influence on recolonization and succession. These include sea ice extent and the proximity of the ice edge, the annual duration of open water, the stabilization of the substratum first by benthic diatoms and later by macrophyte algae, and relative sea level. A period of warmer climate in the mid-Holocene had a considerable influence on the composition and species diversity of the marine flora. These are the first data on the timing of colonization and succession of marine floras over a glacial cycle based on both morphological and biochemical fossils.

  5. Classroom Antarctica

    Science.gov (United States)

    Gozzard, David

    Australian company Antarctica Flights runs summer sightseeing trips out of Australian capital cities to tour the Antarctic coast. The Laby Foundation of the University of Melbourne, through its "Classroom Antarctica" program, sponsored Kent Street High School science teacher, Ms Suzy Urbaniak and 18 of her students to take the trip, to…

  6. Diatom evidence for the onset of Pliocene cooling from AND-1B, McMurdo Sound, Antarctica

    Science.gov (United States)

    Riesselman, Christina; Dunbar, R. B.

    2013-01-01

    The late Pliocene, ~ 3.3–3.0 Ma, is the most recent interval of sustained global warmth in the geologic past. This window is the focus of climate reconstruction efforts by the U.S. Geological Survey's Pliocene Research, Interpretation, and Synoptic Mapping (PRISM) Data/Model Cooperative, and may provide a useful climate analog for the coming century. Reconstructions of past surface ocean conditions proximal to the Antarctic continent are essential to understanding the sensitivity of the cryosphere to this key interval in Earth's climate evolution. An exceptional marine sediment core collected from the southwestern Ross Sea (78° S), Antarctica, during ANDRILL's McMurdo Ice Shelf Project preserves evidence of dramatic fluctuations between grounded ice and productive, open ocean conditions during the late Pliocene, reflecting orbitally-paced glacial/interglacial cycling. In this near-shore record, diatom-rich sediments are recovered from interglacial intervals; two of these diatomites, from ~ 3.2 Ma and 3.03 Ma, are within the PRISM chronologic window. The diatom assemblages identified in PRISM-age late Pliocene diatom-rich sediments are distinct from those in mid-Pliocene and later Pliocene/Pleistocene intervals recovered from AND-1B, and comprise both extant taxa with well-constrained ecological preferences and a diverse extinct flora, some members of which are previously undescribed from Antarctic sediments. Both units are dominated by Chaetoceros resting spores, an indicator of high productivity and stratification that is present at much lower abundance in materials both older and younger than the PRISM-age sediments. Newly described species of the genus Fragilariopsis, which first appear in the AND-1B record at 3.2 Ma, are the most abundant extinct members of the PRISM-age assemblages. Other extant species with established environmental affinities, such as Fragilariopsis sublinearis, F. curta, Stellarima microtrias, and Thalassiothrix antarctica, are

  7. 187Re - 232Th - 238U nuclear geochronometry: constraining magmatism in East-Antarctica and the break-up of Gondwana

    Science.gov (United States)

    Roller, Goetz

    2017-04-01

    187Re - 232Th - 238U nuclear geochronometry is a new dating method for astronomy, earth and planetary sciences [1-4]. Nucleogeochronometric Rhenium-Osmium two-point-isochron (TPI) ages are calculated using a nuclear geochronometer as one data point in a two-point-isochron diagram [5-7]. The IVREA chronometer, for example, is one of five terrestrial nuclear geochronometers identified so far [8]. Here, it is used to constrain the magmatism of the Ferrar flood basalt province, which has been related to continental rifting and the break-up of Gondwana in the Jurassic.TPI ages for seven (basaltic) andesite whole rock samples from the Prince Albert Mountains (Victoria Land, Antarctica) are calculated. An isochron age of 172 ± 5 Ma (187Os/188Osi = 0.194 ± 0.023) has previously been published for these rocks [9]. Initial TPI 187Os/188Osi ratios show only minor scatter between 187Os/188Osi = 0.2149 ± 0.0064 and 187Os/188Osi = 0.22231 ± 0.00080, in agreement with the enigmatic, suprachondritic 187Os/188Osi = 0.194 ± 0.023 from the isochron [9]. TPI ages for the Mount Joyce samples range from 125.4 ± 9.9 Ma to 139 ± 17 Ma and thus constrain the youngest magmatic event(s) in the Transantarctic Mountains. For the Thumb Point basalt, a TPI age of 219 ± 81 Ma is calculated. Despite of its large uncertainty, the age itself is in agreement with the Triassic 224 Ma and 240 Ma events reported from North Patagonia [10]. The TPI age of 186.1 ± 8.1 Ma from the Ricker Hill basalt can be clearly distinguished from the Mount Murray TPI age of 158 ± 14 Ma, while at Brimstone Peak two TPI age groups of 155 ± 14 Ma and 175.3 ± 3.1 Ma are observed. From this it may be concluded that the seven TPI ages indicate episodic magmatic activity in East-Antarctica between 125 Ma and 219 Ma, leading to the break-up of Gondwana. This picture is consistent with the geochronology of the Antarctic Peninsula, Patagonia, the Karoo and the Ferrar mafic rocks [10]. Thus, besides constraining

  8. Early evidence of the genus Homo in East Asia.

    Science.gov (United States)

    Zhu, R X; Potts, R; Pan, Y X; Yao, H T; Lü, L Q; Zhao, X; Gao, X; Chen, L W; Gao, F; Deng, C L

    2008-12-01

    The timing and route of the earliest dispersal from Africa to Eastern Asia are contentious topics in the study of early human evolution because Asian hominin fossil sites with precise age constraints are very limited. Here we report new high-resolution magnetostratigraphic results that place stringent age controls on excavated hominin incisors and stone tools from the Yuanmou Basin, southwest China. The hominin-bearing layer resides in a reverse polarity magnetozone just above the upper boundary of the Olduvai subchron, yielding an estimated age of 1.7Ma. The finding represents the age of the earliest documented presence of Homo, with affinities to Homo erectus, in mainland East Asia. This age estimate is roughly the same as for H. erectus in island Southeast Asia and immediately prior to the oldest archaeological evidence in northeast Asia. Mammalian fauna and pollen obtained directly from the hominin site indicate that the Yuanmou hominins lived in a varied habitat of open vegetation with patches of bushland and forest on an alluvial fan close to a lake or swamp. The age and location are consistent with a rapid southern migration route of initial hominin populations into Eastern Asia.

  9. Palaeoflood evidence on the River Nore, South East Ireland

    Science.gov (United States)

    Fleming, Ciara; Turner, Jonathan; Bourke, Mary

    2017-04-01

    Past geomorphic changes can be detected in sediment sinks, through the investigation of natural sediment archives. Since the advent of palaeoflood hydrology in the 1980s, numerous authors have demonstrated that such sediment deposits record valuable evidence of past flooding events. Many of these studies have focussed on fluvial systems in arid environments, with bedrock channels proving to be particularly successful field sites. In some districts, the collected datasets are now routinely employed to augment analyses of flood frequency and magnitude, which have traditionally relied on extrapolation of short hydrometric datasets. This study targets river reaches in a temperate humid environment, with a predominantly alluvial channel. The River Nore is one of the largest catchments draining South East Ireland. It is situated in a valley with an inherited glacial legacy and is principally a lowland river catchment. Specific morphological zones have been targeted which are optimal for flood deposit preservation, including palaeochannels, tributary junctions and floodplain overbank settings.There are a variety of anthropogenic pressures evident in this landscape. Among them are channelisation of select tributaries, a legacy of coal mining in the upland Carboniferous limestones, and the installation of man-made obstacles or modifications along the length of the river channel such as sluices and weirs. Regarding land-use, the majority of the catchment is dominated by agriculture, mainly pasture with some tillage. This study investigates palaeoflood evidence in the River Nore catchment and examines the development of the river floodplain using a variety of complementary field and desk-based methods. The sub-surface and micro-topography of river reaches are investigated using Ground Penetrating Radar (GPR) and Unmanned Aerial Vehicle (UAV) technology. Flood deposits have been characterised by examination of bank exposures and sediment cores. Installation of sediment traps

  10. Five years' gravity observation with the superconducting gravimeter OSG#058 at Syowa Station, East Antarctica: gravitational effects of accumulated snow mass

    Science.gov (United States)

    Aoyama, Yuichi; Doi, Koichiro; Ikeda, Hiroshi; Hayakawa, Hideaki; Shibuya, Kazuo

    2016-05-01

    Continuous gravimetric observations have been made with three successive generations of superconducting gravimeter over 20 yr at Syowa Station (39.6°E, 69.0°S), East Antarctica. The third-generation instrument, OSG#058, was installed in January 2010 and was calibrated by an absolute gravimeter during January and February, 2010. The estimated scale factor was -73.823 ± 0.053 μGal V-1 (1 μGal = 10-8 m s-2). The first 5 yr of OSG#058 data from 2010 January 7 to 2015 January 10 were decomposed into tidal waves (M3 to Ssa) and other non-tidal components by applying the Bayesian tidal analysis program BAYTAP. Long-term non-tidal gravity residuals, which were obtained by subtracting annual and 18.6 year tidal waves and the predicted gravity response to the Earth's variable rotation, showed significant correlation with the accumulated snow depth measured at Syowa Station. The greatest correlation occurred when the gravity variations lagged the accumulated snow depth by 21 d. To estimate the gravitational effect of the accumulated snow mass, we inferred a conversion factor of 3.13 ± 0.08 μGal m-1 from this relation. The accumulated snow depth at Syowa Station was found to represent an extensive terrestrial water storage (the snow accumulation) around Syowa Station, which was estimated from the Gravity Recovery and Climate Experiment satellite gravity data. The snow accumulation around Syowa Station was detectable by the superconducting gravimeter.

  11. Basal melt, seasonal water mass transformation, ocean current variability, and deep convection processes along the Amery Ice Shelf calving front, East Antarctica}

    Science.gov (United States)

    Herraiz Borreguero, Laura; Church, John A.; Alison, Ian; Peña Molino, Beatriz; Coleman, Richard; Tomczak, Mathias; Craven, Mike

    2017-04-01

    Despite the Amery Ice Shelf (AIS) being the third largest ice shelf in Antarctica, the seasonal variability of the physical processes involved in the AIS-ocean interaction remains undocumented and a robust observational, oceanographic-based basal melt rate estimate has been lacking. Here we use year-long time series of water column temperature, salinity, and horizontal velocities measured along the ice shelf front from 2001 to 2002. Our results show strong zonal variations in the distribution of water masses along the ice shelf front: modified Circumpolar Deep Water (mCDW) arrives in the east, while in the west, Ice Shelf Water (ISW) and Dense Shelf Water (DSW) formed in the Mackenzie polynya dominate the water column. Baroclinic eddies, formed during winter deep convection (down to 1100 m), drive the inflow of DSW into the ice shelf cavity. Our net basal melt rate estimate is 57.4±25.3 Gt yr?1 (1±0.4 m yr?1), larger than previous modeling-based and glaciological-based estimates, and results from the inflow of DSW (0.52±0.38 Sv; 1 Sv=106 m3 s?1) and mCDW (0.22±0.06 Sv) into the cavity. Our results highlight the role of the Mackenzie polynya in the seasonal exchange of water masses across the ice shelf front, and the role of the ISW in controlling the formation rate and thermohaline properties of DSW. These two processes directly impact on the ice shelf mass balance, and on the contribution of DSW/ISW to the formation of Antarctic Bottom Water.

  12. High-resolution records of the beryllium-10 solar activity proxy in ice from Law Dome, East Antarctica: measurement, reproducibility and principal trends

    Directory of Open Access Journals (Sweden)

    J. B. Pedro

    2011-07-01

    Full Text Available Three near-monthly resolution 10Be records are presented from the Dome Summit South (DSS ice core site, Law Dome, East Antarctica. The chemical preparation and Accelerator Mass Spectrometer (AMS measurement of these records is described. The reproducibility of 10Be records at DSS is assessed through intercomparison of the ice core data with data from two previously published and contemporaneous snow pits. We find generally good agreement between the five records, comparable to that observed between other trace chemical records from the site. This result allays concerns raised by a previous Antarctic study (Moraal et al., 2005 about poor reproducibility of ice core 10Be records. A single composite series is constructed from the three ice cores providing a monthly-resolved record of 10Be concentrations at DSS over the past decade (1999 to 2009. To our knowledge, this is the first published ice core data spanning the recent exceptional solar minimum of solar cycle 23. 10Be concentrations are significantly correlated to the cosmic ray flux recorded by the McMurdo neutron monitor (rxy = 0.64, with 95 % CI of 0.53 to 0.71, suggesting that solar modulation of the atmospheric production rate may explain up to ~40 % of the variance in 10Be concentrations at DSS. Sharp concentration peaks occur in most years during the summer-to-autumn, possibly caused by stratospheric incursions. Our results underscore the presence of both production and meteorological signals in ice core 10Be data.

  13. Microbial Communities and Their Predicted Metabolic Functions in Growth Laminae of a Unique Large Conical Mat from Lake Untersee, East Antarctica

    Directory of Open Access Journals (Sweden)

    Hyunmin Koo

    2017-08-01

    Full Text Available In this study, we report the distribution of microbial taxa and their predicted metabolic functions observed in the top (U1, middle (U2, and inner (U3 decadal growth laminae of a unique large conical microbial mat from perennially ice-covered Lake Untersee of East Antarctica, using NextGen sequencing of the 16S rRNA gene and bioinformatics tools. The results showed that the U1 lamina was dominated by cyanobacteria, specifically Phormidium sp., Leptolyngbya sp., and Pseudanabaena sp. The U2 and U3 laminae had high abundances of Actinobacteria, Verrucomicrobia, Proteobacteria, and Bacteroidetes. Closely related taxa within each abundant bacterial taxon found in each lamina were further differentiated at the highest taxonomic resolution using the oligotyping method. PICRUSt analysis, which determines predicted KEGG functional categories from the gene contents and abundances among microbial communities, revealed a high number of sequences belonging to carbon fixation, energy metabolism, cyanophycin, chlorophyll, and photosynthesis proteins in the U1 lamina. The functional predictions of the microbial communities in U2 and U3 represented signal transduction, membrane transport, zinc transport and amino acid-, carbohydrate-, and arsenic- metabolisms. The Nearest Sequenced Taxon Index (NSTI values processed through PICRUSt were 0.10, 0.13, and 0.11 for U1, U2, and U3 laminae, respectively. These values indicated a close correspondence with the reference microbial genome database, implying high confidence in the predicted metabolic functions of the microbial communities in each lamina. The distribution of microbial taxa observed in each lamina and their predicted metabolic functions provides additional insight into the complex microbial ecosystem at Lake Untersee, and lays the foundation for studies that will enhance our understanding of the mechanisms responsible for the formation of these unique mat structures and their evolutionary significance.

  14. Adaptations to Hydrothermal Vent Life in Kiwa tyleri, a New Species of Yeti Crab from the East Scotia Ridge, Antarctica.

    Directory of Open Access Journals (Sweden)

    Sven Thatje

    Full Text Available Hydrothermal vents in the Southern Ocean are the physiologically most isolated chemosynthetic environments known. Here, we describe Kiwa tyleri sp. nov., the first species of yeti crab known from the Southern Ocean. Kiwa tyleri belongs to the family Kiwaidae and is the visually dominant macrofauna of two known vent sites situated on the northern and southern segments of the East Scotia Ridge (ESR. The species is known to depend on primary productivity by chemosynthetic bacteria and resides at the warm-eurythermal vent environment for most of its life; its short-range distribution away from vents (few metres is physiologically constrained by the stable, cold waters of the surrounding Southern Ocean. Kiwa tylerihas been shown to present differential life history adaptations in response to this contrasting thermal environment. Morphological adaptations specific to life in warm-eurythermal waters, as found on - or in close proximity of - vent chimneys, are discussed in comparison with adaptations seen in the other two known members of the family (K. hirsuta, K. puravida, which show a preference for low temperature chemosynthetic environments.

  15. Comparative account of benthic community at two different locations in the continental Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Ingole, B.S.; Dhargalkar, V.K.

    Data on faunal communities, abundance and biomass were collected from seven stations in the Queen Maud Land shelf, Lazarev Sea, East Antarctica and three stations in Atca Ice Port, Weddell Sea, West Antarctica. The sampling depth ranged from 70...

  16. Using Evidence to Reduce Health Inequalities in East and Southern ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    EQUINET has focused the region's attention on equity issues. Its work has influenced the East, Central and Southern Africa Health ... -improve capacity among researchers and decision-makers with workshops, mentorship, and support for master's students -conduct outreach to engage local, regional, and national decision- ...

  17. Seismic Stratigraphy of Ice Sheet Advance-Retreat Cycles on the Sabrina Coast Continental Shelf, East Antarctica

    Science.gov (United States)

    Frederick, B. C.; Gulick, S. P. S.; Saustrup, S.; Fernandez-Vasquez, R. A.; Domack, E. W.; Lavoie, C.; Blankenship, D. D.; Leventer, A.; Shevenell, A.

    2014-12-01

    2D multichannel seismic (MCS), multibeam and CHIRP data were collected as part of the recent R/V Nathaniel B. Palmer (NBP1402) cruise to investigate the marine record of cryosphere-ocean dynamics on the continental shelf between the Dalton Ice Tongue and Totten Glacier systems. Outlet glaciers and ice shelves along this coastline drain a catchment area extending across the Aurora Subglacial Basin (ASB) whose topography lies below sea level and contains an ice volume of approximately 6.9m of sea level rise equivalent. Analysis of over 750km of high-resolution MCS data has revealed the preservation of extensive tilted fluvial-deltaic shelf sedimentation and the first evidence of polythermal glacial advance in this region with well-preserved subglacial meltwater channels and tunnel valley systems. This expansive fluvial to glacial sedimentary section is separated by a regional unconformity from a series of irregular, localized unconformities preserved in an otherwise seismically transparent facies. We interpret these transparent facies as subglacial diamictites deposited over several glacial cycles. Detailed seismic stratigraphic analysis of the glacial sequences above the regional unconformity identified at least 4 glacial cycles illustrated by grounding zone wedge moraine deposits recorded in both MCS and multibeam bathymetric data. Distinct differences were evident in the stratigraphic architecture of polar versus polythermal glaciations including greater preservation of till deposits above the regional unconformity proximal to the exposed bedrock boundary and the present-day ice front. Sedimentary sequence preservation here appears dictated by the geometry of local ice advance and allied basement structure controls. Integration of marine geology, high resolution CHIRP and multibeam bathymetry data with MCS sequence geometry and acoustic facies mapping has led to improved constraints on rates, styles and patterns of glacial retreat. Such improvements to deformable

  18. Valdivian ecosystems in the late Cretaceous and early Tertiary of Antarctica: further evidence from myrtaceous and eucryphiaceous fossil wood

    NARCIS (Netherlands)

    Poole, I.J.; Mennega, A.M.W.; Cantrill, David J.

    2003-01-01

    Cool temperate rainforests growing on the flanks of the Andes and along the Coastal Range in Valdivia (Chile) today provide the closest analogue for the fossil floras of Antarctica during the Eocene. This paper records key Valdivian elements in a Maastrichtian to Eocene wood flora that extends the

  19. Sedimentary response to sea ice and atmospheric variability over the instrumental period off Adélie Land, East Antarctica

    Science.gov (United States)

    Campagne, Philippine; Crosta, Xavier; Schmidt, Sabine; Noëlle Houssais, Marie; Ther, Olivier; Massé, Guillaume

    2016-07-01

    Diatoms account for a large proportion of primary productivity in Antarctic coastal and continental shelf zones. Diatoms, which have been used for a long time to infer past sea surface conditions in the Southern Ocean, have recently been associated with diatom-specific biomarkers (highly branched isoprenoids, HBI). Our study is one of the few sedimentary research projects on diatom ecology and associated biomarkers in the Antarctic seasonal sea ice zone. To date, the Adélie Land region has received little attention, despite evidence for the presence of high accumulation of laminated sediment, allowing for finer climate reconstructions and sedimentary process studies. Here we provide a sequence of seasonally to annually laminated diatomaceous sediment from a 72.5 cm interface core retrieved on the continental shelf off Adélie Land, covering the 1970-2010 CE period. Investigations through statistical analyses of diatom communities, diatom-specific biomarkers and major element abundances document the relationships between these proxies at an unprecedented resolution. Additionally, comparison of sedimentary records to meteorological data monitored by automatic weather station and satellite derived sea ice concentrations help to refine the relationships between our proxies and environmental conditions over the last decades. Our results suggest a coupled interaction of the atmospheric and sea surface variability on sea ice seasonality, which acts as the proximal forcing of siliceous productivity at that scale.

  20. Towards a comprehensive geophysical coverage of a test Glacier; example from various surveys during field campaigns over the Astrolabe outlet Glacier, East Antarctica

    Science.gov (United States)

    Le Meur, E.; Berthier, E.; Blankenship, D.; Drouet, A.; Durand, G.; de Fleurian, B.; Gagliardini, O.; Garambois, S.; Gim, Y.; Holt, J. W.; Kirchner, D. L.; Legresy, B.; Mouginot, J.; Safaeinili, A.; Siegert, M. J.; Rignot, E.; Young, D.

    2009-12-01

    We discuss various field observations that have been (and will still be) carried out during the last two field seasons over a test glacier in East Antarctica under the framework of the DACOTA program (supported by both the French Agence Nationale de la Recherche, and the French Polar Institute). We will use various techniques so as to provide a better characterization of the dynamics of an outlet glacier as well as the required data sets for running and constraining an ice flow model. These outlet glaciers play a crucial role by draining ice situated inland, thereby controlling the overall mass balance of large parts of the ice sheet. As a small, simple, and accessible glacier, Astrolabe Glacier is an ideal test case. Data of the kinds being collected provide a reference against which later measurements will be compared to infer significant trends (velocity and thickness changes). As an example, surface elevation has been measured at various places on the glacier. The order of magnitude of thickness changes expected compared to the measurement techniques accuracy should allow for significant trends after a couple of years. A permanent deformation rate network consisting of autonomous GPS stations has been started last year and should be completed next winter. By being located close to the grounding line, the deformation rate network will yield constraining data for the model by providing the surface velocity changes induced by the mobility of the grounding line. With regard to modelling input data, bedrock topography represents the most important data set but also the most difficult to access. Radar techniques have been used with first a ground-based penetrating radar later completed by two larger scale airborne surveys allowing for full coverage of the entire drainage basin (8000 km2). This airborne campaign has been possible under the frame of a collaboration between the University of Texas (60 MHz airborne radar), the Jet Propulsion Laboratory (2.5 MHz airborne

  1. Semi-Automatic Mapping of Tidal Cracks in the Fast Ice Region near Zhongshan Station in East Antarctica Using Landsat-8 OLI Imagery

    Directory of Open Access Journals (Sweden)

    Fengming Hui

    2016-03-01

    Full Text Available Tidal cracks are linear features that appear parallel to coastlines in fast ice regions due to the actions of periodic and non-periodic sea level oscillations. They can influence energy and heat exchange between the ocean, ice, and atmosphere, as well as human activities. In this paper, the LINE module of Geomatics 2015 software was used to automatically extract tidal cracks in fast ice regions near the Chinese Zhongshan Station in East Antarctica from Landsat-8 Operational Land Imager (OLI data with resolutions of 15 m (panchromatic band 8 and 30 m (multispectral bands 1–7. The detected tidal cracks were determined based on matching between the output from the LINE module and manually-interpreted tidal cracks in OLI images. The ratio of the length of detected tidal cracks to the total length of interpreted cracks was used to evaluate the automated detection method. Results show that the vertical direction gradient is a better input to the LINE module than the top-of-atmosphere (TOA reflectance input for estimating the presence of cracks, regardless of the examined resolution. Data with a resolution of 15 m also gives better results in crack detection than data with a resolution of 30 m. The statistics also show that, in the results from the 15-m-resolution data, the ratios in Band 8 performed best with values of the above-mentioned ratio of 50.92 and 31.38 percent using the vertical gradient and the TOA reflectance methods, respectively. On the other hand, in the results from the 30-m-resolution data, the ratios in Band 5 performed best with ratios of 47.43 and 17.8 percent using the same methods, respectively. This implies that Band 8 was better for tidal crack detection than the multispectral fusion data (Bands 1–7, and Band 5 with a resolution of 30 m was best among the multispectral data. The semi-automatic mapping of tidal cracks will improve the safety of vehicles travel in fast ice regimes.

  2. Acoustic survey for marine mammal occurrence and distribution off East Antarctica (30-80°E) in January-February 2006

    Science.gov (United States)

    Gedamke, Jason; Robinson, Sarah M.

    2010-05-01

    A large scale, systematic, acoustic survey for whales and seals in eastern Antarctic waters was conducted in January-February 2006. During the BROKE-West survey of Southern Ocean waters between 30 and 80° E longitude, an acoustic survey was conducted to complement a traditional visual survey for marine mammal occurrence and distribution. As part of the survey, 145 DIFAR sonobuoys were deployed every 30' of latitude on north-south transects, and prior to CTD stations on the initial east-west transect. Underwater sound was analyzed for 70 minute samples from each sonobuoy. Blue whales were the most commonly recorded species, identified at 55 of the sonobuoy deployment sites. Other species recorded include: sperm (46 sites), fin (14), humpback (2), and sei (3) whales, and leopard (11) and Ross (17) seals. Large numbers of blue and sperm whales, and all Ross seals were detected on the westernmost two transects, which were the only transects of the survey with relatively extensive sea ice remaining off the continental shelf. Large numbers of blue whales were also detected in the more eastern waters of the survey off the Prydz Bay region, while two detections of pygmy blue whales represent the farthest south these whales have been recorded. Of the relatively few fin whale detections, most occurred in more northerly waters. Fin whale vocalizations from this region were distinctly different than those recorded elsewhere around Antarctica suggesting acoustic recordings may be useful to delineate regional or stock boundaries of this species. Previously undescribed sounds were attributed to Ross seals. Acoustic detections of these and leopard seal sounds indicate these animals venture further from their traditionally described distributions, with vocalizing leopard seals occurring much further north than might be expected. Overall, the results of the sonobuoy survey provide a measure of each species' relative spatial distribution over the survey area based on acoustic

  3. Megadunes and Geologic Maps of Snow/Firn of East Antarctica: Implications for Major Climatic Change, Accumulation Rates, Ice Flowage, and Bedrock Structures

    Science.gov (United States)

    Wise, D. U.; Cianfarra, P.; Salvini, F.

    2007-12-01

    Recent satellite mosaics of East Antarctica (EA) contradict current megadune origin models based on modern wind patterns, sastrugi, and slow, snow/firn accumulation rates. The images invariably show older megadune fields buried by younger snow/firn or cut by younger structures with sastrugi as surface decorations. An alternative model proposes these enigmatic, 2-4 km spaced, zebra-striped, snow ripple marks are relics of a past climate wherein summer glaze preserved winter antidunes that grew at rates 10 to 50 times present values. This requires an earlier Holocene, warm climatic excursion with extremely rapid snow accumulation from moisture- rich air off more open winter seas. Following this, present-day snow/firn has slowly accumulated over about 2/3 of EA. This, plus limited apparent erosion / ablation of megadune areas, implies relatively minor, net accumulation over the post-megadune surface, now collapsing from deeper, bedrock-controlled outflow. A new type of snow/firn geologic map supports these interpretations using the Megadune Formation (MF) as a basal unit. A new class of transitional high relief dunes helps define the MF. These "Duke of York" (DOY) dunes (after that nursery rhyme of uphill-downhill marches) marks the top of the MF, transitional from uphill-migrating, upper flow regime antidunes into overlying, downhill-migrating, modern- style, lower flow regime dune fields and smooth snow/firn deposits. The MF crops out flowing over bedrock highs and disappears into snow basins above bedrock lows. One map suggests flowage over a 900 km-long, bedrock, fault-line scarp passing nearly under the South Pole. An opposite facing partner forms a bedrock horst, blocking drainage of a stagnant basin now filled as the large, flat area E of the pole. A map of Argus Dome, highest divide of the plateau, suggests high relief DOY dunes formed a walled, shallow basin around a former divide. That basin, now completely filled with firn, forms the present crest, with

  4. High-resolution Deglacial to Holocene paleoceanographic records from the Sabrina Coast, East Antarctica: Preliminary foraminifer-based results from NBP14-02

    Science.gov (United States)

    Shevenell, A.; Snow, T.; Domack, E. W.; Leventer, A.; Gulick, S. P. S.; Huber, B. A.; Orsi, A. H.; Goddard, E.; Fernandez-Vasquez, R. A.

    2014-12-01

    Cruise 14-02 of the RV/IB N.B. Palmer conducted the first multidisciplinary oceanographic investigation of the continental shelf within the Dalton Iceberg Tongue polynya off the Sabrina Coast, East Antarctica. At >350 m in the northeastern polynya, hydrographic measurements confirmed that relatively warm (>0°C) oceanic thermocline water from near the shelf break has been imported to the shelf but likely within an interior recirculation associated with local mid-shelf bathymetry. CHIRP sub-bottom data revealed ~15 m of acoustically transparent sediment in a 550-m deep basin proximal to this feature. A suite of coring devices was used to recover a complete 13-m sequence of Late Pleistocene glacial diamict and Holocene laminated diatom oozes and muds (NBP14-02 MC 45, KC 27B, JPC 27, and JKC 53) with chronology constrained by 210Pb and foraminifer-based AMS 14C dates. Unlike many Antarctic margin sedimentary sequences, biogenic carbonate (CaCO3) is exceptionally well preserved throughout the sedimentary sequence, likely due to non-corrosive bottom waters and/or low sedimentary organic carbon content. Planktic foraminifer Neogloboquadrina pachyderma(s) is present throughout and abundant in the diatomaceous muds. Bulimina aculeata, which prefers calm, hemipelagic environments and bottom water temperatures >0°C, dominates the living benthic foraminifer assemblage. Fossil assemblages oscillate between B. aculeata and Trifarina angulosa-dominated assemblages. As T. angulosa is associated with oxygenated bottom waters and strong bottom currents, this assemblage may record past changes in the location of the Polar and Slope Fronts. This interpretation is supported by T. angulosa presence in Thalassiothrix diatom oozes, which are associated with oceanic frontal zones and rapid biosiliceous sedimentation. Preliminary foraminifer oxygen and carbon isotopes, N. pachyderma(s) presence, and the observed T. angulosa Mg/Ca-temperature (-1.8 to 0°C) relationship highlight the

  5. Preliminary CFA measurements of Al and Fe "available" fraction in EPICA-Dome C ice core (East Antarctica)

    Science.gov (United States)

    Udisti, R.; Barbante, C.; Cozzi, G.; Fattori, I.; Largiuni, O.; Magaldi, L.; Traversi, R.

    2003-04-01

    Aerosol load of Al and Fe allows estimating the crustal contribution to the primary aerosol sources. While continental dust is the only significant source for Al, Fe takes part also to metabolic processes of living species as an essential oligo-element. For this reason, it has been assumed that atmospheric deposition of desert dust on the oceanic surface can constitute a phytoplanktonic growth factor. Besides, Fe content in aerosol during glacial/interglacial transitions is believed to play a relevant role in controlling oceanic phytoplanktonic uptake of atmospheric CO2. A detailed stratigraphy of Al and Fe in ice cores is basic in understanding the correlation between environmental and climatic changes. Here we report preliminary results of CFA methods able to determine, in field, the "available" (free form and labile complexes) fraction of Al and Fe in ice cores with high sensitivity (D.L. of 10 ppt for Al and 300 ppt for Fe) and reproducibility (around 2 % at ppb level). The two methods were applied to 32 selected sections coming from the EPICA-Dome C ice core (EDC96): 10 sections belonging to Holocene, 10 to the transition and 12 to the LGM. Though Al and Fe determined by CFA is representative of the only soluble fraction (or "available" in the measurement conditions after filtration on 5.0 um), a comparison with the Al and Fe "total" content, as measured by ICP-MS, was made. "Available" fractions represent a minor contribution to the ICP-MS Fe and Al content in the LGM, but this contribution increases during the transition. In the Holocene, the two different analytical methods give similar values. Anyway, also CFA Fe and Al profiles show a sharp concentration decrease in the glacial/interglacial transition, reflecting the lowering dust aerosol load. Fe, especially, shows a very high sensitivity for the ACR climatic change. Whereas CFA-Fe in the LGM is more than 10 times lower than ICP-MS-Fe, ACR values are similar. This evidence could be explained considering

  6. Genetic evidence for an East Asian origin of domestic dogs.

    Science.gov (United States)

    Savolainen, Peter; Zhang, Ya-ping; Luo, Jing; Lundeberg, Joakim; Leitner, Thomas

    2002-11-22

    The origin of the domestic dog from wolves has been established, but the number of founding events, as well as where and when these occurred, is not known. To address these questions, we examined the mitochondrial DNA (mtDNA) sequence variation among 654 domestic dogs representing all major dog populations worldwide. Although our data indicate several maternal origins from wolf, >95% of all sequences belonged to three phylogenetic groups universally represented at similar frequencies, suggesting a common origin from a single gene pool for all dog populations. A larger genetic variation in East Asia than in other regions and the pattern of phylogeographic variation suggest an East Asian origin for the domestic dog, approximately 15,000 years ago.

  7. Finance and Inequality – Evidence from East Asia

    Directory of Open Access Journals (Sweden)

    Mohamed Salah Mansour

    2015-08-01

    Full Text Available The economic debate about inequality has occupied a huge place in the scientific discourse of the last decades. Several factors have been identified as causes for the rising wealth and income inequality in various regions such as economic growth, capital return and intergenerational wealth. In this paper, East Asia is chosen as a regional focus for the analysis due to the region’s specific characteristics and history regarding inequality. Until the end of the 1980s, the region experienced a period of so-called “growth with equity” where high economic growth rates were associated with decreasing poverty and inequality. In recent years, however, growth in East Asia has gone hand in hand with inequality. This shift from “growth with equity” to “growth with inequality” makes the region worth investigating. The paper focuses particularly on the size of the financial sector, analyzing its role and impact on the development of inequality. Therefore, the theoretical connection and the natural relationship between poverty, inequality, economic growth as well as the size of the financial sector are discussed. Indicators, proxies and measurements for these variables are identified, based on existing literature. The main analysis delivers an answer to the research question of whether and how financial development affects the inequality in a society. For the analysis, cross-country and panel data for the ASEAN+3 countries from 1960-2012 are used.

  8. Under the sea ice: Exploring the relationship between sea ice and the foraging behaviour of southern elephant seals in East Antarctica

    Science.gov (United States)

    Labrousse, Sara; Sallée, Jean-Baptiste; Fraser, Alexander D.; Massom, Robert A.; Reid, Phillip; Sumner, Michael; Guinet, Christophe; Harcourt, Robert; McMahon, Clive; Bailleul, Frédéric; Hindell, Mark A.; Charrassin, Jean-Benoit

    2017-08-01

    Investigating ecological relationships between predators and their environment is essential to understand the response of marine ecosystems to climate variability and change. This is particularly true in polar regions, where sea ice (a sensitive climate variable) plays a crucial yet highly dynamic and variable role in how it influences the whole marine ecosystem, from phytoplankton to top predators. For mesopredators such as seals, sea ice both supports a rich (under-ice) food resource, access to which depends on local to regional coverage and conditions. Here, we investigate sex-specific relationships between the foraging strategies of southern elephant seals (Mirounga leonina) in winter and spatio-temporal variability in sea ice concentration (SIC) and coverage in East Antarctica. We satellite-tracked 46 individuals undertaking post-moult trips in winter from Kerguelen Islands to the peri-Antarctic shelf between 2004 and 2014. These data indicate distinct general patterns of sea ice usage: while females tended to follow the sea ice edge as it extended northward, the males remained on the continental shelf despite increasing sea ice. Seal hunting time, a proxy of foraging activity inferred from the diving behaviour, was longer for females in late autumn in the outer part of the pack ice, ∼150-370 km south of the ice edge. Within persistent regions of compact sea ice, females had a longer foraging activity (i) in the highest sea ice concentration at their position, but (ii) their foraging activity was longer when there were more patches of low concentration sea ice around their position (either in time or in space; 30 days & 50 km). The high spatio-temporal variability of sea ice around female positions is probably a key factor allowing them to exploit these concentrated patches. Despite lack of information on prey availability, females may exploit mesopelagic finfishes and squids that concentrate near the ice-water interface or within the water column (from

  9. A geochemical study of lithospheric mantle beneath Northern Victoria Land (Antarctica): main evidences from volatile content in ultramafic xenoliths

    Science.gov (United States)

    Correale, Alessandra; Pelorosso, Beatrice; Rizzo, Andrea Luca; Coltorti, Massimo; Italiano, Francesco; Bonadiman, Costanza

    2017-04-01

    A geochemical study of ultramafic xenoliths from Northern Victoria Land (Green Point, GP and Handler Ridge, HR), is carried out in order to investigate the features of the lithosphere mantle beneath the Western Antarctic Ridge System (WARS). The majority of samples is spinel anhydrous lherzolite with rare presence of secondary phases (secondary cpx and glass). Geothermobarometric calculations, based on the Fe/Mg distribution among the peridotite minerals reveal that Sub Continental Lithospheric Mantle (SCLM) beneath Handler Ridge records temperatures and redox conditions higher then Greene Point (P fixed at 15 Kbar). Moreover, geochemical models evidence that, GP mantle domain represents a residuum after ˜7 to 21 % of partial melting in the spinel stability field, which was variably affected by interaction with infiltrating melts, acting in different times, from at least Jurassic to Cenozoic (Pelorosso et al., 2016). Fluid inclusions (FI) entrapped in olivine and pyroxene crystals were investigated for elemental and isotopic contents of both, noble gases (He, Ne, Ar) and CO2. He, Ar and Ne concentrations range from 1.52×10-14 to 1.07×10-12, from 4.09×10-13 to 3.47×10-11and from 2.84×10-16 to 7.57×10-14 mol/g, respectively, while the CO2amounts are between 7.08×10-10 and 8.12×10-7 mol/g. The 3He/4He varies between 5.95 and 20.18 Ra (where Ra is the 3He/4He ratio of air), being the lowest and the highest values measured in the He-poorer samples. Post-eruptive input of cosmogenic 3He and radiogenic 4He seems to influence mainly the samples associated to a lower He concentrations, increasing and decreasing respectively their primordial 3He/4He values, that for all the other samples range between 6.76 and 7.45 Ra. This range reasonably reflects the isotope signature of mantle beneath the investigated areas. The 4He/40Ar* ratio corrected for atmospheric-derived contamination ranges between 0.004 and 0.39. The lowest 4He/40Ar* values (4He/40Ar*<0.1) are

  10. UAV Antarctica

    OpenAIRE

    Dahl, David; Stetler, Fredrik

    2014-01-01

    One of the biggest problems of our time is the global warming. A direct result of this phenomena is the melting of ice of the glaciers on the north and the south pole. As this continues, the melted ice will contribute to an increase of the sea level, and may cause enormous natural disasters. To be able to prevent this, it’s important to study its affects. This reports contains a concept study of a Unmanned Aerial Vehicle, a UAV, set on the coast of Antarctica by the Australian owned base Davi...

  11. Absence of evidence is no proof : slave resistance under German colonial rule in East Africa

    NARCIS (Netherlands)

    Deutsch, J-G.; Abbink, J.; Bruijn, de M.E.; Walraven, van K.

    2003-01-01

    This chapter examines the lack of evidence regarding slave resistance in German East Africa and the related question of whether the colonial stereotype of the 'docile slave' is true. It starts with a brief surmise of the history of slavery and an analysis of slave actions in the period concerned

  12. Photolysis imprint in the nitrate stable isotope signal in snow and atmosphere of East Antarctica and implications for reactive nitrogen cycling

    Directory of Open Access Journals (Sweden)

    J. M. F. Martins

    2009-11-01

    Full Text Available The nitrogen (δ15N and triple oxygen (δ17O and δ18O isotopic composition of nitrate (NO3 was measured year-round in the atmosphere and snow pits at Dome C, Antarctica (DC, 75.1° S, 123.3° E, and in surface snow on a transect between DC and the coast. Comparison to the isotopic signal in atmospheric NO3 shows that snow NO3 is significantly enriched in δ15N by >200‰ and depleted in δ18O by <40‰. Post-depositional fractionation in Δ17O(NO3 is small, potentially allowing reconstruction of past shifts in tropospheric oxidation pathways from ice cores. Assuming a Rayleigh-type process we find fractionation constants ε of −60±15‰, 8±2‰ and 1±1‰, for δ15N, δ18O and Δ17O, respectively. A photolysis model yields an upper limit for the photolytic fractionation constant 15ε of δ15N, consistent with lab and field measurements, and demonstrates a high sensitivity of 15ε to the incident actinic flux spectrum. The photolytic 15ε is process-specific and therefore applies to any snow covered location. Previously published 15ε values are not representative for conditions at the Earth surface, but apply only to the UV lamp used in the reported experiment (Blunier et al., 2005; Jacobi et al., 2006. Depletion of oxygen stable isotopes is attributed to photolysis followed by isotopic exchange with water and hydroxyl radicals. Conversely, 15N enrichment of the NO3 fraction in the snow implies 15N depletion of emissions. Indeed, δ15N in atmospheric NO3 shows a strong decrease from background levels (4±7‰ to −35‰ in spring followed by recovery during summer, consistent with significant snowpack

  13. Correlating the Late Mesoproterozoic Unkar Group, Grand Canyon, Arizona with the upper Rocky Cape Group, western Tasmania: A sedimentary record of a southwest Laurentia-East Antarctica connection in Rodinia

    Science.gov (United States)

    Mulder, Jacob; Karlstrom, Karl; Halpin, Jacqueline; Meffre, Sebastien; Gehrels, George; Pecha, Mark

    2017-04-01

    A major challenge facing paleogeographic reconstructions of the Late Mesoproterozoic supercontinent Rodinia is identifying the extension of the Grenville orogen in continents formerly adjacent to western Laurentia (Proterozoic North America). Many paleogeographic reconstructions of Rodinia link exposures of the Grenville orogen in southern Laurentia to Late Mesoproterozoic orogens in central Australia or in the Transantarctic Mountains of East Antarctica. The Grenville Orogeny in southern Laurentia was accompanied by regionally extensive sedimentation in the interior of the continent, represented by a series of Late Mesoproterozoic basins throughout southwest Laurentia. The Late Mesoproterozoic basin system of southwest Laurentia is truncated by the Neoproterozoic rifted margin of western Laurentia produced during the breakup of Rodinia. Remnants of this basin system could be exposed on continents formerly adjacent to western Laurentia and may therefore be an important 'piercing point' for refining paleogeographic reconstructions of Rodinia. In this contribution, we identify a possible fragment of the Late Mesoproterozoic basin system of southwest Laurentia represented by the upper Rocky Cape Group of western Tasmania, Australia. We test the correlation between Late Mesoproterozoic strata in southwest Laurentia and western Tasmania through new field observations and detrital zircon U-Pb-Hf isotopic data from exposures of the Unkar Group (Grand Canyon, Arizona) and the upper Rocky Cape Group. The stratigraphy of the Unkar Group and upper Rocky Cape Group are remarkably similar with both successions comprising a lower subdivision of stromatolitic dolomite and siltstone overlain by quartz arenite with soft-sediment deformation features. Detrital zircons age distributions from the Unkar and upper Rocky Cape Groups are both characterized by large age peaks at 1600—1800 Ma, prominent 1450 Ma peaks, abundant 1400—1300 Ma ages, and youngest peaks at ca. 1220 Ma. The

  14. De ontdekking van Antarctica

    NARCIS (Netherlands)

    Beintema, A.J.

    2004-01-01

    Aristoteles bedacht de naam Antarctica, maar wie ontdekte het zevende continent? Dit eerste artikel binnen het thema Antarctica beantwoordt die vraag. Ontdekkingsreizigers als Cook, Biscoe, Amundsen en Scott komen ter sprake, naast het kartografisch werk van Finnaeus

  15. The geochemistry of Don Juan Pond: Evidence for a deep groundwater flow system in Wright Valley, Antarctica

    Science.gov (United States)

    Toner, J. D.; Catling, D. C.; Sletten, R. S.

    2017-09-01

    Don Juan Pond (DJP), Antarctica, is one of the most unusual surface waters on Earth because of its CaCl2-rich composition. To investigate the evolution of pond waters during closed-basin evaporation and to understand the source of brines responsible for the chemistry of DJP, we apply a newly developed low-temperature aqueous model in the Na-K-Ca-Mg-Cl system to DJP. By modeling the closed-basin evaporation of DJP and comparing ionic ratios between DJP surface water, deep groundwater, shallow groundwater, and other surface chemistries in Wright Valley, we find that DJP is best explained by upwelling deep groundwater, as opposed to recent hypotheses proposing shallow groundwater sources. The early closed-basin evolution of brines in our model accurately predicts observed chemistries in DJP; however, late-stage closed-basin evaporation produces Mg-K-rich brines and salts that do not match the CaCl2-rich brine in DJP. Based on groundwater inflow rates to DJP, we estimate that even the most concentrated brines in DJP have undergone closed-basin evaporation for less than a year. To explain the observed lack of Mg2+ and K+ accumulation in DJP over time, and the surprisingly young age for the brines, we deduce that DJP is a localized upwelling from a regional groundwater flow-through system in which evaporated DJP brines are recycled back into the subsurface over yearly timescales. The existence of a regional groundwater flow system beneath DJP has implications for water and solute budgets in cold desert ecosystems, and may provide clues for the formation of groundwater and aqueous flows on Mars.

  16. Physical, psychological, sexual, and systemic abuse of children with disabilities in East Africa: Mapping the evidence.

    Directory of Open Access Journals (Sweden)

    Niall Winters

    Full Text Available Children with disabilities (CWDs are at a higher risk of being maltreated than are typical children. The evidence base on the abuse of children with disabilities living in low- and middle-income countries is extremely limited but the problem is particularly acute in East Africa. We don't know the types of evidence that exist on this topic. This problem is compounded by the fact that key indicators of disability, such as reliable prevalence rates, are not available currently. This paper addresses this serious problem by mapping the existing evidence-base to document the coverage, patterns, and gaps in existing research on the abuse of children with disabilities in East Africa. An evidence map, following systematic review guidelines, was conducted and included a systematic search, transparent and structured data extraction, and critical appraisal. Health and social science databases (Medline, EMBASE, PsychInfo, Taylor&Francis, Web of Science, and SAGE were systematically searched for relevant studies. A substantive grey literature search was also conducted. All empirical research on the abuse of CWDs in East Africa was eligible for inclusion: Data on abuse was systematically extracted and the research evidence, following critical appraisal, mapped according to the type of abuse and disability condition, highlighting gaps and patterns in the evidence-base. 6005 studies were identified and screened, of which 177 received a full-text assessment. Of these, 41 studies matched the inclusion criteria. By mapping the available data and reports and systematically assessing their trustworthiness and relevance, we highlight significant gaps in the available evidence base. Clear patterns emerge that show a major data gap and lack of research on sexual abuse of children with disabilities and an identifiable lack of methodological quality in many relevant studies. These make the development of a concerted and targeted research effort to tackle the abuse of

  17. Physical, psychological, sexual, and systemic abuse of children with disabilities in East Africa: Mapping the evidence.

    Science.gov (United States)

    Winters, Niall; Langer, Laurenz; Geniets, Anne

    2017-01-01

    Children with disabilities (CWDs) are at a higher risk of being maltreated than are typical children. The evidence base on the abuse of children with disabilities living in low- and middle-income countries is extremely limited but the problem is particularly acute in East Africa. We don't know the types of evidence that exist on this topic. This problem is compounded by the fact that key indicators of disability, such as reliable prevalence rates, are not available currently. This paper addresses this serious problem by mapping the existing evidence-base to document the coverage, patterns, and gaps in existing research on the abuse of children with disabilities in East Africa. An evidence map, following systematic review guidelines, was conducted and included a systematic search, transparent and structured data extraction, and critical appraisal. Health and social science databases (Medline, EMBASE, PsychInfo, Taylor&Francis, Web of Science, and SAGE) were systematically searched for relevant studies. A substantive grey literature search was also conducted. All empirical research on the abuse of CWDs in East Africa was eligible for inclusion: Data on abuse was systematically extracted and the research evidence, following critical appraisal, mapped according to the type of abuse and disability condition, highlighting gaps and patterns in the evidence-base. 6005 studies were identified and screened, of which 177 received a full-text assessment. Of these, 41 studies matched the inclusion criteria. By mapping the available data and reports and systematically assessing their trustworthiness and relevance, we highlight significant gaps in the available evidence base. Clear patterns emerge that show a major data gap and lack of research on sexual abuse of children with disabilities and an identifiable lack of methodological quality in many relevant studies. These make the development of a concerted and targeted research effort to tackle the abuse of children with

  18. In situ-measurement of ice deformation from repeated borehole logging of the EPICA Dronning Maud Land (EDML) ice core, East Antarctica.

    Science.gov (United States)

    Jansen, Daniela; Weikusat, Ilka; Kleiner, Thomas; Wilhelms, Frank; Dahl-Jensen, Dorthe; Frenzel, Andreas; Binder, Tobias; Eichler, Jan; Faria, Sergio H.; Sheldon, Simon; Panton, Christian; Kipfstuhl, Sepp; Miller, Heinrich

    2017-04-01

    The European Project for Ice Coring in Antarctica (EPICA) ice core was drilled between 2001 and 2006 at the Kohnen Station, Antarctica. During the drilling process the borehole was logged repeatedly. Repeated logging of the borehole shape is a means of directly measuring the deformation of the ice sheet not only on the surface but also with depth, and to derive shear strain rates for the lower part, which control the volume of ice transported from the inner continent towards the ocean. The logging system continuously recorded the tilt of the borehole with respect to the vertical (inclination) as well as the heading of the borehole with respect to magnetic north (azimuth) by means of a compass. This dataset provides the basis for a 3-D reconstruction of the borehole shape, which is changing over time according to the predominant deformation modes with depth. The information gained from this analysis can then be evaluated in combination with lattice preferred orientation, grain size and grain shape derived by microstructural analysis of samples from the deep ice core. Additionally, the diameter of the borehole, which was originally circular with a diameter of 10 cm, was measured. As the ice flow velocity at the position of the EDML core is relatively slow (about 0.75 m/a), the changes of borehole shape between the logs during the drilling period were very small and thus difficult to interpret. Thus, the site has been revisited in the Antarctic summer season 2016 and logged again using the same measurement system. The change of the borehole inclination during the time period of 10 years clearly reveals the transition from a pure shear dominated deformation in the upper part of the ice sheet to shear deformation at the base. We will present a detailed analysis of the borehole parameters and the deduced shear strain rates in the lower part of the ice sheet. The results are discussed with respect to ice microstructural data derived from the EDML ice core. Microstructural

  19. Glaciers of Antarctica

    Science.gov (United States)

    Williams, Richard S.; Ferrigno, Jane G.

    1988-01-01

    have been included. Again, these represent only a small fraction of the large number of aerial photographs now available in various national collections. The chapter is divided into five geographic sections. The first is the Transantarctic Mountains in the Ross Sea area. Some very large outlet glaciers flow from the East Antarctic ice sheet through the Transantarctic Mountains to the Ross Ice Shelf. Byrd Glacier, one of the largest in the world, drains an area of more than 1,000,000 km2. Next, images from the Indian Ocean sector are discussed. These include the Lambert Glacier- Amery Ice Shelf system, so large that about 25 images must be mosaicked to cover its complex system of tributary glaciers. Shirase Glacier, a tidal outlet glacier in the sector, flows at a speed of 2.5 km a-l. About 200 km inland and 200 km west of Shirase Glacier lie the Queen Fabiola (?Yamato?) Mountains, whose extensive exposures of `blue ice? lay claim to being the world?s most important meteorite-collecting locality, with more than 4,700 meteorite fragments discovered since 1969. The Atlantic Ocean sector is fringed by ice shelves into which flow large ice streams like Jutulstraumen, Stancomb-Wills, Slessor, and Recovery Glaciers. Filchner and Ronne Ice Shelves together cover an area two-thirds the size of Texas. From the western margin of the Ronne Ice Shelf, the north-trending arc of the Antarctic Peninsula, with its fjord and alpine landscape and fringing ice shelves, stretches towards South America. The Pacific Ocean sector begins with the Ellsworth Mountains, which include the highest peaks (Vinson Massif at 4,897 m) in Antarctica. The area between the Ellsworth Mountains and the eastern margin of the Ross Ice Shelf is fringed with small ice shelves and some major outlet glaciers. One of these, Pine Island Glacier, was found from comparing 1973 and 1975 images to have an average ice-front velocity of 2.4 km a-l. This part of Antarctica

  20. Raman spectroscopy, an innovative tool to explore the mineralogy and provenance of dust (1-5 µm): Dome B ice core, East Antarctica

    Science.gov (United States)

    Ileana Paleari, Chiara; Andò, Sergio; Delmonte, Barbara; Maggi, Valter; Garzanti, Eduardo

    2017-04-01

    The polar ice sheets are invaluable archives preserving information about past climate changes and atmosphere composition. Deep ice cores from Greenland and Antarctica provide records of several climate-dependent proxies allowing climate reconstructions at different time scales, among which greenhouse gases, atmospheric aerosol and aeolian dust. In this project, the mineralogy of dust preserved in the Dome B (77°05'S, 94°55'E, 3650 m a.s.l.) ice core was investigated using Raman spectroscopy. The thermal drilled ice core, made during the 1987-1988 Austral season by the 33rd Soviet Antarctic Expedition, covers the last 30 kyr. The record thus encompasses the last glacial period, the Last Glacial Maximum (LGM), the deglaciation and the beginning of the Holocene. Four Dome B ice core samples from the LGM were selected, and the mineralogical fingerprint of dust particles was investigated. Dust in central Antarctic ice cores is clay to finest silt, the volume-size distribution of particles showing modal values around 2-2.6 µm at the Dome B site. Detrital minerals of such a fine grain-size range are exceedingly difficult to determine one by one, a task that to the best of our knowledge has never been accomplished so far. In order to meet this challenge, we have developed a new protocol for the preparation and analysis of particles between 1 and 5 µm in diameter, in a clean room at the EuroCold Lab and at the Laboratory for Provenance Studies of Milano-Bicocca University. Three slides were prepared for each sample, and 962 particles were studied overall. In total, 41 different minerals were recognized, including species derived from granitoid, metamorphic or siliciclastic rocks (e.g., quartz, feldspars and phyllosilicates), from volcanic source rocks (e.g., sanidine, anorthite, pyroxenes, zeolites) associated with biogenic marine aragonite and iron oxides probably derived from erosion of soil profiles. Our observations indicate southern South America as the most

  1. Right: Left:: East: West. Evidence that individuals from East Asian and South Asian cultures emphasize right hemisphere functions in comparison to Euro-American cultures.

    Science.gov (United States)

    Rozin, Paul; Moscovitch, Morris; Imada, Sumio

    2016-09-01

    We present evidence that individuals from East or South Asian cultures (Japanese college students in Japan and East or South Asian born and raised college students in the USA) tend to exhibit default thinking that corresponds to right hemisphere holistic functions, as compared to Caucasian individuals from a Western culture (born and raised in the USA). In two lateralized tasks (locating the nose in a scrambled face, and global-local letter task), both Asian groups showed a greater right hemisphere bias than the Western group. In a third lateralized task, judging similarity in terms of visual form versus functional/semantic categorizations, there was not a reliable difference between the groups. On a classic, ambiguous face composed of vegetables, both Eastern groups displayed a greater right hemisphere (holistic face processing) bias than the Western group. These results support an "East - Right Hemisphere, West - Left Hemisphere" hypothesis, as originally proposed by Ornstein (1972). This hypothesis is open as to the degree to which social-cultural forces were involved in hemispheric specialization, or the opposite, or both. Our aim is to encourage a more thorough analysis of this hypothesis, suggesting both lateralization studies corresponding to documented East-West differences, and East-West studies corresponding to lateralization differences. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Continent-wide risk assessment for the establishment of nonindigenous species in Antarctica

    Science.gov (United States)

    Chown, Steven L.; Huiskes, Ad H. L.; Gremmen, Niek J. M.; Lee, Jennifer E.; Terauds, Aleks; Crosbie, Kim; Frenot, Yves; Hughes, Kevin A.; Imura, Satoshi; Kiefer, Kate; Lebouvier, Marc; Raymond, Ben; Tsujimoto, Megumu; Ware, Chris; Van de Vijver, Bart; Bergstrom, Dana Michelle

    2012-01-01

    Invasive alien species are among the primary causes of biodiversity change globally, with the risks thereof broadly understood for most regions of the world. They are similarly thought to be among the most significant conservation threats to Antarctica, especially as climate change proceeds in the region. However, no comprehensive, continent-wide evaluation of the risks to Antarctica posed by such species has been undertaken. Here we do so by sampling, identifying, and mapping the vascular plant propagules carried by all categories of visitors to Antarctica during the International Polar Year's first season (2007–2008) and assessing propagule establishment likelihood based on their identity and origins and on spatial variation in Antarctica's climate. For an evaluation of the situation in 2100, we use modeled climates based on the Intergovernmental Panel on Climate Change's Special Report on Emissions Scenarios Scenario A1B [Nakićenović N, Swart R, eds (2000) Special Report on Emissions Scenarios: A Special Report of Working Group III of the Intergovernmental Panel on Climate Change (Cambridge University Press, Cambridge, UK)]. Visitors carrying seeds average 9.5 seeds per person, although as vectors, scientists carry greater propagule loads than tourists. Annual tourist numbers (∼33,054) are higher than those of scientists (∼7,085), thus tempering these differences in propagule load. Alien species establishment is currently most likely for the Western Antarctic Peninsula. Recent founder populations of several alien species in this area corroborate these findings. With climate change, risks will grow in the Antarctic Peninsula, Ross Sea, and East Antarctic coastal regions. Our evidence-based assessment demonstrates which parts of Antarctica are at growing risk from alien species that may become invasive and provides the means to mitigate this threat now and into the future as the continent's climate changes. PMID:22393003

  3. Linking regional variation of epibiotic bacterial diversity and trophic ecology in a new species of Kiwaidae (Decapoda, Anomura) from East Scotia Ridge (Antarctica) hydrothermal vents.

    Science.gov (United States)

    Zwirglmaier, Katrin; Reid, William D K; Heywood, Jane; Sweeting, Christopher J; Wigham, Benjamin D; Polunin, Nicholas V C; Hawkes, Jeff A; Connelly, Douglas P; Pearce, David; Linse, Katrin

    2015-02-01

    We analyzed the diversity of bacterial epibionts and trophic ecology of a new species of Kiwa yeti crab discovered at two hydrothermal vent fields (E2 and E9) on the East Scotia Ridge (ESR) in the Southern Ocean using a combination of 454 pyrosequencing, Sanger sequencing, and stable isotope analysis. The Kiwa epibiont communities were dominated by Epsilon- and Gammaproteobacteria. About 454 sequencing of the epibionts on 15 individual Kiwa specimen revealed large regional differences between the two hydrothermal vent fields: at E2, the bacterial community on the Kiwa ventral setae was dominated (up to 75%) by Gammaproteobacteria, whereas at E9 Epsilonproteobacteria dominated (up to 98%). Carbon stable isotope analysis of both Kiwa and the bacterial epibionts also showed distinct differences between E2 and E9 in mean and variability. Both stable isotope and sequence data suggest a dominance of different carbon fixation pathways of the epibiont communities at the two vent fields. At E2, epibionts were putatively fixing carbon via the Calvin-Benson-Bassham and reverse tricarboxylic acid cycle, while at E9 the reverse tricarboxylic acid cycle dominated. Co-varying epibiont diversity and isotope values at E2 and E9 also present further support for the hypothesis that epibionts serve as a food source for Kiwa. © 2014 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.

  4. Pollen evidence for a mid-Holocene East Asian summer monsoon maximum in northern China

    Science.gov (United States)

    Wen, Ruilin; Xiao, Jule; Fan, Jiawei; Zhang, Shengrui; Yamagata, Hideki

    2017-11-01

    There is a controversy regarding whether the high precipitation delivered by an intensified East Asian summer monsoon occurred during the early Holocene, or during the middle Holocene, especially in the context of the monsoonal margin region. The conflicting views on the subject may be caused by chronological uncertainties and ambiguities in the interpretation of different climate proxies measured in different sedimentary sequences. Here, we present a detailed record of the Holocene evolution of vegetation in northern China based on a high-resolution pollen record from Dali Lake, located near the modern summer monsoon limit. From 12,000-8300 cal BP, the sandy land landscape changed from desert to open elm forest and shrubland, while dry steppe dominated the hilly lands and patches of birch forest developed in the mountains. Between 8300 and 6000 cal BP, elm forest was extensively distributed in the sandy lands, while typical steppe covered the hilly lands and mixed coniferous-broadleaved forests expanded in the mountains. Our pollen evidence contradicts the view that the monsoonal rainfall increased during the early Holocene; rather, it indicates that the East Asian summer monsoon did not become intensified until ∼8000 cal BP in northern China. The low precipitation during the early Holocene can be attributed to the boundary conditions, i.e., to the remnant high-latitude Northern Hemisphere ice sheets and the relatively low global sea level.

  5. Bringing Antarctica Home

    Science.gov (United States)

    Constible, Juanita; Williams, Lauren; Faure, Jaime; Lee, Richard E., Jr.

    2012-01-01

    When one thinks of the amazing creatures of Antarctica, an insect probably does not come to mind. But this unlikely animal, and a scientific expedition to Antarctica, was the foundation for a learning event that created a community of learners spanning kindergarten through sixth grade and extended beyond the classroom. Miami University's Antarctic…

  6. Geological and geomorphological evidence for the southwestern extension of the East Anatolian Fault Zone, Turkey

    Science.gov (United States)

    Yönlü, Önder; Altunel, Erhan; Karabacak, Volkan

    2017-07-01

    The left lateral strike slip East Anatolian Fault Zone (EAFZ) is the main structural link between the North Anatolian Fault Zone (NAFZ) in north and subduction in the Mediterranean Sea and the transform Dead Sea Fault Zone (DSFZ) in south. We studied the southwestern continuation of the EAFZ using combined field investigations including geomorphology, geology and paleoseismology. Mapping of offset drainages, lineaments, shutter ridges and fault planes in young geological units suggests existence of active faults between the Mediterranean coast and Türkoğlu where it intersects with the DSFZ. Yumurtalık and Toprakkale faults are the main tectonic structures and detailed examination of geological and geomorphological evidences suggest their Quaternary activity. Paleoseismic trenching on these faults provided evidence for at least two surface rupturing events in the last 9,000 yr. Detailed examination of paleo-valleys of the Ceyhan River suggests that the course of the river migrated due to the activity of the Toprakkale Fault. Obtained geological and geomorphological data indicates that the EAFZ continues across the Amanos Mountains and the slip transfer is mainly accommodated by the Toprakkale and Yumurtalık faults.

  7. Sauropodomorph dinosaur trackways from the Fleming Fjord Formation of East Greenland: Evidence for Late Triassic sauropods

    Directory of Open Access Journals (Sweden)

    Jens N. Lallensack

    2017-11-01

    Full Text Available The Late Triassic (Norian–early Rhaetian Fleming Fjord Formation of central East Greenland preserves a diverse fossil fauna, including both body and trace fossils. Trackways of large quadrupedal archosaurs, although already reported in 1994 and mentioned in subsequent publications, are here described and figured in detail for the first time, based on photogrammetric data collected during fieldwork in 2012. Two trackways can be referred to Eosauropus, while a third, bipedal trackway may be referred to Evazoum, both of which have been considered to represent sauropodomorph dinosaur tracks. Both the Evazoum and the Eosauropus trackways are distinctly larger than other trackways referred to the respective ichnogenera. The trackmaker of the best preserved Eosauropus trackway is constrained using a synapomorphy-based approach. The quadrupedal posture, the entaxonic pes structure, and five weight-bearing digits indicate a derived sauropodiform trackmaker. Other features exhibited by the tracks, including the semi-digitigrade pes and the laterally deflected unguals, are commonly considered synapomorphies of more exclusive clades within Sauropoda. The present trackway documents an early acquisition of a eusauropod-like pes anatomy while retaining a well-developed claw on pedal digit IV, which is reduced in eusauropods. Although unequivocal evidence for sauropod dinosaurs is no older than the Early Jurassic, the present trackway provides evidence for a possible Triassic origin of the group.

  8. Remote sensing evidence of decadal changes in major tropospheric ozone precursors over East Asia

    Science.gov (United States)

    Souri, Amir Hossein; Choi, Yunsoo; Jeon, Wonbae; Woo, Jung-Hun; Zhang, Qiang; Kurokawa, Jun-ichi

    2017-02-01

    Recent regulatory policies in East Asia reduce ozone precursors, but these changes are spatially and temporally nonuniform. This study investigates variations in the long-term trends of tropospheric NO2, HCHO, and HCHO/NO2 ratios to diagnose ozone sensitivity to changes in NOx and volatile organic compound using the Ozone Monitoring Instrument (OMI). Using an adaptive-degree polynomial filter, we identify extremums of time series of NO2 to determine when and how NO2 change. Due to the regulations in China, trends which were predominantly upward turned downward. The years undergoing these changes primarily happened in 2011 and 2012. OMI column densities, however, suggest that NOx sources in South Korea, the Pearl River Delta (PRD), Taiwan, and Japan have not consistently decreased. Specifically, as Chinese exports of NO2 started subsiding, increasing trends in NO2 columns over several Korean cities, including Seoul, become evident. To quantify the changes in NOx emissions from summertime 2010 to 2014, we conduct a 3D-Var inverse modeling using a regional model with MIX-Asia inventory and estimate NOx emissions (in 2010 and 2014) for the PRD (1.6 and 1.5 Gg/d), the Yangtze River Delta (3.9 and 3.0 Gg/d), north China (15.6 and 14.3 Gg/d), South Korea (1.6 and 1.5 Gg/d), and Japan (2.7 and 2.6 Gg/d). OMI HCHO shows upward trends in East Asia resulting from anthropogenic effects; however, the magnitudes are negative in the PRD, Japan, North Korea, and Taiwan. OMI HCHO/NO2 ratios reveal that while South Korea, Japan, and the south of China have undergone toward more NOx-sensitive regime, areas around the Bohai Sea have become more NOx saturated.

  9. Environmental and climate changes in Antarctica in the Geological Past

    Directory of Open Access Journals (Sweden)

    G. L. Leitchenkov

    2014-01-01

    Full Text Available In the Cretaceous time, Antarctica was characterized by subtropical and tropical climate. The Early Eocene was warmest in the Antarctic history but this Climatic Optimum terminated with a long-term cooling trend that culminated in continental-scale glaciation of Antarctica at about 34 Ma ago. There is indirect evidence that small ice caps developed within central Antarctica in the Late Eocene (42−34 Ma. From the Early Oligocene to the Middle Miocene (34−13 Ma ice sheet was wet-based and fluctuated considerably in volume, but about 14 m.y. ago it became dry-based and more stable.  Seismic data collected on the East Antarctic margin give valuable information on dynamics of the past ice sheets. These data shows that the sedimentary cover of the western Wilkes Land margin includes a giant (c. 200 000 km2 deep-water fan which formed between c. 43 and 34 Ma ago. The average rate of sedimentation in the central part of fan was 230–250 m/m.y. Active input of terrigenous sediments into deep-water denotes high-energy fluvial system within the Wilkes Land. Emergence of this fluvial system evidences earliest glaciation in the Antarctic interior which fed full-flowing rivers. The thickness of strata deposited during post-Early Oligocene glaciations on the Antarctic margin generally reflects the averaged energy of depositional environments. The thickest sediments (up to 2.0 km, i.e. almost twice more than in other parts of East Antarctic margin and inferred highest energy are seen in the central Cooperation Sea, on the central Wilkes Land margin and in the D'Urville Sea. The areas with the thickest post-Early Oligocene strata correlate with places where present-day ice discharge is highest, such as via the Lambert, Totten and Mertz/Ninnis Glaciers. The correlation points to high ice (and sediment flux in the same areas since the Early Oligocene.

  10. Are Fluctuations in Energy Consumption Transitory or Permanent? Evidence From a Panel of East Asia & Pacific Countries

    Directory of Open Access Journals (Sweden)

    Hakan Kum

    2012-07-01

    Full Text Available This paper examines the unit root properties of energy consumption per capita for 15 East Asia & Pacific countries employing the Lagrange Multiplier (LM panel unit root test with one structural break for 1971-2007. When we apply the LM univariate test without break, we find a unit root in per capita consumption for Brunei Darussalam, Indonesia, Japan, North Korea, South Korea and Myanmar. However, when we apply LM unit root with structural break, we find overwhelming evidence that there is no unit root in per capita energy consumption for these 15 East Asia & Pacific countries.

  11. Waterborne outbreak of cryptosporidiosis in the South East of Ireland: weighing up the evidence.

    Science.gov (United States)

    Mahon, M; Doyle, S

    2017-11-01

    In late Spring 2012, 12 cases of cryptosporidiosis in a town in the South East of Ireland were notified to the regional Department of Public Health. The purpose of this paper is to describe the outbreak and the investigative process which led to the conclusion that the source was a public drinking water supply. Outbreak and incident control teams were convened to investigate and control the outbreak. Eleven cases were speciated as Cryptosporidium parvum. GP60 analysis demonstrated that 10 were C. parvum IIaA20G3R1, indicating that the cases were linked. The public water supply was the only common risk factor identified. Increased water sampling identified Cryptosporidium muris/andersoni in the treated water at one of two water treatment plants (Water Treatment Plant, WTP A) for the supply, and on the network. C. parvum was subsequently identified in raw water from WTP A. The Health Service Executive (HSE) concluded that this outbreak was "probably associated with water" produced at WTP A based on (1) descriptive epidemiological evidence suggesting water-related illness and excluding other obvious explanations; and (2) water treatment failure at WTP A. WTP A was closed to facilitate an upgrade. No boil water notice was required as a supplementary supply was available. The upgrade was completed and the incident closed in 2013.

  12. Combined Gravimetric-Seismic Crustal Model for Antarctica

    Science.gov (United States)

    Baranov, Alexey; Tenzer, Robert; Bagherbandi, Mohammad

    2017-09-01

    The latest seismic data and improved information about the subglacial bedrock relief are used in this study to estimate the sediment and crustal thickness under the Antarctic continent. Since large parts of Antarctica are not yet covered by seismic surveys, the gravity and crustal structure models are used to interpolate the Moho information where seismic data are missing. The gravity information is also extended offshore to detect the Moho under continental margins and neighboring oceanic crust. The processing strategy involves the solution to the Vening Meinesz-Moritz's inverse problem of isostasy constrained on seismic data. A comparison of our new results with existing studies indicates a substantial improvement in the sediment and crustal models. The seismic data analysis shows significant sediment accumulations in Antarctica, with broad sedimentary basins. According to our result, the maximum sediment thickness in Antarctica is about 15 km under Filchner-Ronne Ice Shelf. The Moho relief closely resembles major geological and tectonic features. A rather thick continental crust of East Antarctic Craton is separated from a complex geological/tectonic structure of West Antarctica by the Transantarctic Mountains. The average Moho depth of 34.1 km under the Antarctic continent slightly differs from previous estimates. A maximum Moho deepening of 58.2 km under the Gamburtsev Subglacial Mountains in East Antarctica confirmed the presence of deep and compact orogenic roots. Another large Moho depth in East Antarctica is detected under Dronning Maud Land with two orogenic roots under Wohlthat Massif (48-50 km) and the Kottas Mountains (48-50 km) that are separated by a relatively thin crust along Jutulstraumen Rift. The Moho depth under central parts of the Transantarctic Mountains reaches 46 km. The maximum Moho deepening (34-38 km) in West Antarctica is under the Antarctic Peninsula. The Moho depth minima in East Antarctica are found under the Lambert Trench (24

  13. Combined Gravimetric-Seismic Crustal Model for Antarctica

    Science.gov (United States)

    Baranov, Alexey; Tenzer, Robert; Bagherbandi, Mohammad

    2018-01-01

    The latest seismic data and improved information about the subglacial bedrock relief are used in this study to estimate the sediment and crustal thickness under the Antarctic continent. Since large parts of Antarctica are not yet covered by seismic surveys, the gravity and crustal structure models are used to interpolate the Moho information where seismic data are missing. The gravity information is also extended offshore to detect the Moho under continental margins and neighboring oceanic crust. The processing strategy involves the solution to the Vening Meinesz-Moritz's inverse problem of isostasy constrained on seismic data. A comparison of our new results with existing studies indicates a substantial improvement in the sediment and crustal models. The seismic data analysis shows significant sediment accumulations in Antarctica, with broad sedimentary basins. According to our result, the maximum sediment thickness in Antarctica is about 15 km under Filchner-Ronne Ice Shelf. The Moho relief closely resembles major geological and tectonic features. A rather thick continental crust of East Antarctic Craton is separated from a complex geological/tectonic structure of West Antarctica by the Transantarctic Mountains. The average Moho depth of 34.1 km under the Antarctic continent slightly differs from previous estimates. A maximum Moho deepening of 58.2 km under the Gamburtsev Subglacial Mountains in East Antarctica confirmed the presence of deep and compact orogenic roots. Another large Moho depth in East Antarctica is detected under Dronning Maud Land with two orogenic roots under Wohlthat Massif (48-50 km) and the Kottas Mountains (48-50 km) that are separated by a relatively thin crust along Jutulstraumen Rift. The Moho depth under central parts of the Transantarctic Mountains reaches 46 km. The maximum Moho deepening (34-38 km) in West Antarctica is under the Antarctic Peninsula. The Moho depth minima in East Antarctica are found under the Lambert Trench (24

  14. Further Evidence for Bats as the Evolutionary Source of Middle East Respiratory Syndrome Coronavirus

    Directory of Open Access Journals (Sweden)

    S. J. Anthony

    2017-04-01

    Full Text Available The evolutionary origins of Middle East respiratory syndrome (MERS coronavirus (MERS-CoV are unknown. Current evidence suggests that insectivorous bats are likely to be the original source, as several 2c CoVs have been described from various species in the family Vespertilionidae. Here, we describe a MERS-like CoV identified from a Pipistrellus cf. hesperidus bat sampled in Uganda (strain PREDICT/PDF-2180, further supporting the hypothesis that bats are the evolutionary source of MERS-CoV. Phylogenetic analysis showed that PREDICT/PDF-2180 is closely related to MERS-CoV across much of its genome, consistent with a common ancestry; however, the spike protein was highly divergent (46% amino acid identity, suggesting that the two viruses may have different receptor binding properties. Indeed, several amino acid substitutions were identified in key binding residues that were predicted to block PREDICT/PDF-2180 from attaching to the MERS-CoV DPP4 receptor. To experimentally test this hypothesis, an infectious MERS-CoV clone expressing the PREDICT/PDF-2180 spike protein was generated. Recombinant viruses derived from the clone were replication competent but unable to spread and establish new infections in Vero cells or primary human airway epithelial cells. Our findings suggest that PREDICT/PDF-2180 is unlikely to pose a zoonotic threat. Recombination in the S1 subunit of the spike gene was identified as the primary mechanism driving variation in the spike phenotype and was likely one of the critical steps in the evolution and emergence of MERS-CoV in humans.

  15. Living and Working in Antarctica.

    Science.gov (United States)

    Kemp, Noel

    This source book, designed for 11- to 14-year-old students, seeks to describe what life is like in Antarctica. In spite of extreme weather conditions, people go to Antarctica to work every summer. Some of them stay there during the winter as well. This book seeks to supply answers to such questions as: How do people get to Antarctica? Why do they…

  16. Coastal structural remains on the east coast of India: Evidence of maritime activities and their significance

    Digital Repository Service at National Institute of Oceanography (India)

    Tripati, S.

    in relation to the maritime history of the east coast of India. Keywords: Coastal structures, Ancient ports, Maritime activities, Structural remains, East coast of India. Introduction The Indian Peninsula has noticed a chain of development of seaports... number of ancient ports of India were located at the mouth of rivers and in case of lagoons at the outlets to the sea, where cargo can be handled easily and vessels can be anchored properly. Further, to corroborate the fact, the ancient Indian text...

  17. Excess water generation during reaction-inducing intrusion of granitic melts into ultramafic rocks at crustal P-T conditions in the Sør Rondane Mountains of East Antarctica

    Science.gov (United States)

    Uno, Masaoki; Okamoto, Atsushi; Tsuchiya, Noriyoshi

    2017-07-01

    Arc magmas are one of the main sources of aqueous geofluids in the crust, and the movement of fluids above magma chambers has been geophysically imaged. Here, we constrain the water budget (i.e., supply, consumption and release of H2O) in these areas above magma chamber by examining the hydration caused by crust-melt reactions in the Sør Rondane Mountains of East Antarctica. The study area contains a phlogopite-pargasite-peridotite unit that has been intruded by numerous granitic dikes, creating hydration reaction zones at the dike-peridotite boundary. These reactions occurred at 0.5 GPa and 700 °C, corresponding to middle crustal conditions, and generated a series of reaction zones with distance from the granitic dikes as follows: (i) granitic dike, (ii) pargasite-actinolite zone, (iii) tremolite-phlogopite zone, (iv) anthophyllite-phlogopite zone, (v) phlogopite-olivine-orthopyroxene zone, and (vi) unaltered pargasite-phlogopite peridotite. The presence of amphiboles with a preferred orientation perpendicular to the dike margins and an absence of Cr-rich magnetite indicate that the pargasite-actinolite zone [zone (ii)] grew from the dike margins as a result of the dike reacting with the host rock, with an initial melt/rock boundary located between zones (ii) and (iii). The H2O contents of reaction zones (ii)-(v) are higher than the content in the hosting pargasite-phlogopite peridotite, suggesting that the intrusion of the dike was associated with hydration reactions. Geochemical analysis along a profile through the reaction zones indicates Mg and Fe depletion, and Si enrichment in zones (iii)-(iv), and Ca depletion and K enrichment in zones (iv)-(v) relative to the hosting pargasite-phlogopite peridotite. In contrast, zone (ii) is characterized by Ca, Fe, and Mg enrichments relative to the granitic dike. These observations suggest that the reaction zone sequence was formed by the elemental transfer between granitic dike and parasite-phlogopite peridotite: Ca

  18. Cancer Control Programs in East Asia: Evidence From the International Literature

    Directory of Open Access Journals (Sweden)

    Malcolm A. Moore

    2014-07-01

    Full Text Available Cancer is a major cause of mortality and morbidity throughout the world, including the countries of North-East and South-East Asia. Assessment of burden through cancer registration, determination of risk and protective factors, early detection and screening, clinical practice, interventions for example in vaccination, tobacco cessation efforts and palliative care all should be included in comprehensive cancer control programs. The degree to which this is possible naturally depends on the resources available at local, national and international levels. The present review concerns elements of cancer control programs established in China, Taiwan, Korea, and Japan in North-East Asia, Viet Nam, Thailand, Malaysia, and Indonesia as representative larger countries of South-East Asia for comparison, using the published literature as a guide. While major advances have been made, there are still areas which need more attention, especially in South-East Asia, and international cooperation is essential if standard guidelines are to be generated to allow effective cancer control efforts throughout the Far East.

  19. A Novel Adenovirus in Chinstrap Penguins (Pygoscelis antarctica in Antarctica

    Directory of Open Access Journals (Sweden)

    Sook-Young Lee

    2014-05-01

    Full Text Available Adenoviruses (family Adenoviridae infect various organ systems and cause diseases in a wide range of host species. In this study, we examined multiple tissues from Chinstrap penguins (Pygoscelis antarctica, collected in Antarctica during 2009 and 2010, for the presence of novel adenoviruses by PCR. Analysis of a 855-bp region of the hexon gene of a newly identified adenovirus, designated Chinstrap penguin adenovirus 1 (CSPAdV-1, showed nucleotide (amino acid sequence identity of 71.8% (65.5% with South Polar skua 1 (SPSAdV-1, 71% (70% with raptor adenovirus 1 (RAdV-1, 71.4% (67.6% with turkey adenovirus 3 (TAdV-3 and 61% (61.6% with frog adenovirus 1 (FrAdV-1. Based on the genetic and phylogenetic analyses, CSPAdV-1 was classified as a member of the genus, Siadenovirus. Virus isolation attempts from kidney homogenates in the MDTC-RP19 (ATCC® CRL-8135™ cell line were unsuccessful. In conclusion, this study provides the first evidence of new adenovirus species in Antarctic penguins.

  20. The Pleistocene evolution of the East Antarctic Ice Sheet in the Prydz bay region: Stable isotopic evidence from ODP Site 1167

    Science.gov (United States)

    Theissen, K.M.; Dunbar, R.B.; Cooper, A. K.; Mucciarone, D.A.; Hoffmann, D.

    2003-01-01

    Ocean Drilling Program Leg 188, Prydz Bay, East Antarctica is part of a larger initiative to explore the Cenozoic history of the Antarctic Ice Sheet through direct drilling and sampling of the continental margins. In this paper, we present stable isotopic results from Ocean Drilling Program (ODP) Site 1167 located on the Prydz Channel Trough Mouth Fan (TMF), the first Antarctic TMF to be drilled. The foraminifer-based ??18O record is interpreted along with sedimentary and downhole logging evidence to reconstruct the Quaternary glacial history of Prydz Bay and the adjacent Lambert Glacier Amery Ice Shelf System (LGAISS). We report an electron spin resonance age date of 36. 9 ?? 3.3 ka at 0.45 m below sea floor and correlate suspected glacial-interglacial cycles with the global isotopic stratigraphy to improve the chronology for Site 1167. The ??18O record based on planktonic (Neogloboquadrina pachyderma (s.)) and limited benthic results (Globocassidulina crassa), indicates a trend of ice sheet expansion that was interrupted by a period of reduced ice volume and possibly warmer conditions during the early-mid-Pleistocene (0.9-1.38 Ma). An increase in ?? 18O values after ??? 900 ka appears to coincide with the mid-Pleistocene climate transition and the expansion of the northern hemisphere ice sheet. The ??18O record in the upper 50 m of the stratigraphic section indicates as few as three glacial-interglacial cycles, tentatively assigned as marine isotopic stages (MIS) 16-21, are preserved since the Brunhes/Matuyama paleomagnetic reversal (780 ka). This suggests that there is a large unconformity near the top of the section and/or that there may have been few extreme advances of the ice sheet since the mid-Pleistocene climate transition resulting in lowered sedimentation rates on the Prydz Channel TMF. The stable isotopic record from Site 1167 is one of the few available from the area south of the Antarctic Polar Front that has been linked with the global isotopic

  1. The Empirical Evidence on Government Bond Market Integration in East Asia

    Directory of Open Access Journals (Sweden)

    Lian Liu

    2016-03-01

    Full Text Available This research intends to investigate the progress made in East Asian bond market integration thus far. Price-based measures (AAD indicator and beta-convergence measure, quantity-based measures and econometric techniques (co-integration test, error correction model based Granger causality test are employed in the analysis. Even though East Asian government bond markets have become more integrated since 2001, the differentials among the markets still remain significantly high. The bond market integration process seems slow. The convergence of bond markets sped up in 2003 and after the 2008 world financial crisis, implying the important role of government policies in integrating the regional bond markets. East Asian bond market integration may need more government-directed measures.

  2. Pb isotope evidence for contributions from different Iceland mantle components to Palaeogene East Greenland flood basalts

    DEFF Research Database (Denmark)

    Peate, David; Stecher, Ole

    2003-01-01

    We present new Pb isotope data on 21 samples of break-up-related flood basalts (56–54 Ma) from the Blosseville Kyst region of East Greenland. These samples show a considerable range in isotopic composition (206Pb/204Pb 17.6 to 19.3) that broadly correlates with compositional type. The ‘low-Ti’ type...... in the selected samples. Uncontaminated Palaeogene East Greenland flood basalts appear to have sampled the same broad range in mantle compositions seen in Recent Iceland basalts. In contrast to the peripheral lava suites from the British Isles and Southeast Greenland, where the inferred uncontaminated magmas have...

  3. Antarctica: Discovery & Exploration.

    Science.gov (United States)

    Gascoigne, Toss; Collett, Peter

    An examination of Antarctica, from the first sightings to the heroic explorations of the late 18th and early 19th centuries to modern-day research, is presented in this book. Twelve chapters are as follows: (1) The search begins; (2) Whalers and sealers: bites and nibbles; (3) The new continent: first sight; (4) Wintering: the first party; (5)…

  4. Apprenticeship, Vocational Training, and Early Labor Market Outcomes--Evidence from East and West Germany

    Science.gov (United States)

    Riphahn, Regina T.; Zibrowius, Michael

    2016-01-01

    We study the returns to apprenticeship and vocational training for three early labor market outcomes all measured at age 25 for East and West German youths: non-employment (i.e. unemployment or out of the labor force), permanent fulltime employment, and wages. We find strong positive effects of apprenticeship and vocational training. There are no…

  5. Major population expansion of East Asians began before neolithic time: evidence of mtDNA genomes.

    Science.gov (United States)

    Zheng, Hong-Xiang; Yan, Shi; Qin, Zhen-Dong; Wang, Yi; Tan, Jing-Ze; Li, Hui; Jin, Li

    2011-01-01

    It is a major question in archaeology and anthropology whether human populations started to grow primarily after the advent of agriculture, i.e., the Neolithic time, especially in East Asia, which was one of the centers of ancient agricultural civilization. To answer this question requires an accurate estimation of the time of lineage expansion as well as that of population expansion in a population sample without ascertainment bias. In this study, we analyzed all available mtDNA genomes of East Asians ascertained by random sampling, a total of 367 complete mtDNA sequences generated by the 1000 Genome Project, including 249 Chinese (CHB, CHD, and CHS) and 118 Japanese (JPT). We found that major mtDNA lineages underwent expansions, all of which, except for two JPT-specific lineages, including D4, D4b2b, D4a, D4j, D5a2a, A, N9a, F1a1'4, F2, B4, B4a, G2a1 and M7b1'2'4, occurred before 10 kya, i.e., before the Neolithic time (symbolized by Dadiwan Culture at 7.9 kya) in East Asia. Consistent to this observation, the further analysis showed that the population expansion in East Asia started at 13 kya and lasted until 4 kya. The results suggest that the population growth in East Asia constituted a need for the introduction of agriculture and might be one of the driving forces that led to the further development of agriculture.

  6. Influence of Persistent Wind Scour on the Surface Mass Balance of Antarctica

    Science.gov (United States)

    Das, Indrani; Bell, Robin E.; Scambos, Ted A.; Wolovick, Michael; Creyts, Timothy T.; Studinger, Michael; Fearson, Nicholas; Nicolas, Julien P.; Lenaerts, Jan T. M.; vandenBroeke, Michiel R.

    2013-01-01

    Accurate quantification of surface snow accumulation over Antarctica is a key constraint for estimates of the Antarctic mass balance, as well as climatic interpretations of ice-core records. Over Antarctica, near-surface winds accelerate down relatively steep surface slopes, eroding and sublimating the snow. This wind scour results in numerous localized regions (Antarctica. The scour zones are persistent because they are controlled by bedrock topography. On the basis of our Dome A observations, we develop an empirical model to predict wind-scour zones across the Antarctic continent and find that these zones are predominantly located in East Antarctica. We estimate that approx. 2.7-6.6% of the surface area of Antarctica has persistent negative net accumulation due to wind scour, which suggests that, across the continent, the snow mass input is overestimated by 11-36.5 Gt /yr in present surface-mass-balance calculations.

  7. Credit risk determinants in Sub-Saharan banking systems: Evidence from five countries and lessons learnt from Central East and South East European countries

    Directory of Open Access Journals (Sweden)

    Eftychia Nikolaidou

    2017-06-01

    Full Text Available Banking systems in Sub-Saharan Africa (SSA have grown notably over the past decades due to benign macroeconomic, regulatory and financial trends. Nonetheless, downside risks remain elevated by structural issues, commodity price fluctuations, reversal of capital flows and spill-over effects from external shocks in a manner similar to the Central East and South East European (CESEE countries. In the light of the 2008–2009 Global Financial Crisis, great attention has been given to understanding the causes of banking instability with most of the research focusing on advanced economies and, to a lesser extent, large emerging markets while little attention has been paid to the bank-based financial sectors of Sub-Saharan Africa. Furthermore, there is scarcity of studies aiming at knowledge-sharing among different emerging economies. This paper aims to identify the determinants of bank credit risk by focusing on five SSA countries: Kenya, Namibia, South Africa, Zambia and Uganda. Using the ARDL approach to cointegration, findings indicate that increased money supply conditions have a decreasing effect on NPLs in all counties, banking industry-specific variables play a significant role in the case of South Africa and Uganda while NPLs are driven by country-specific variables in the case of Kenya, South Africa and Zambia. The effect of the Global Financial Crisis is evidenced indirectly. Drawing on evidence from CESEE countries with long experience in banking crises, reforms and financial deepening process, the paper provides lessons for SSA countries and offers policy recommendations in the direction of strengthening banks’ balance sheets to ensure financial stability.

  8. Antarctica, supercontinents and the palaeogeography of the Cambrian 'explosion'

    Science.gov (United States)

    Dalziel, Ian

    2014-05-01

    Laurentia is bordered by latest Precambrian-Cambrian rifted margins and must therefore have been located within a Precambrian supercontinent. Geochronologic and geochemical evidence indicates that it was attached to parts of the East Antarctic craton within the Rodinian supercontinent in the late Mesoproterozoic. The Mawson craton of Antarctica rifted from the proto-Pacific margin of Laurentia during the Neooproterozoic, colliding with the present 'southern cone' of Laurentia at ~600 Ma along the Shackleton Range suture zone as Gondwana and Laurentia amalgamated to form the ephemeral Pannotia supercontinental assembly at the end of the Precambrian. The abrupt appearance of almost all animal phyla in the fossil record is often colloquially referred to as the Cambrian 'explosion' of life on Earth. It is also named 'Darwin's dilemma,' as he appreciated that this seemingly mysterious event posed a major problem for his theory of evolution by natural selection. It coincided with a time of major marine transgression over all the continents. Although the metazoan 'explosion' is now seen as more protracted than formerly recognized, it is still regarded one of the most critical events in the history of the biosphere. One of the most striking aspects of the earliest Cambrian fossils is geographic differentiation. In particular, the first benthic trilobite faunas on Laurentia, ancestral North America, and the newly amalgamated southern supercontinent of Gondwana are distinctly different. This has led to the suggestion of an unknown vicariant event intervening between an ancestral trilobite clade and higher members that are represented in the fossil record, possibly one related to the breakup of a supercontinent. Igneous rocks along the Panthalassic margin of Gondwana, including South America, southernmost Africa and the Ellsworth-Whitmore crustal block of Antarctica, and along the proto-Appalachian margin of Laurentia indicate that final separation of Laurentia from

  9. Evidence that a West-East admixed population lived in the Tarim Basin as early as the early Bronze Age

    Directory of Open Access Journals (Sweden)

    Zhang Quanchao

    2010-02-01

    Full Text Available Abstract Background The Tarim Basin, located on the ancient Silk Road, played a very important role in the history of human migration and cultural communications between the West and the East. However, both the exact period at which the relevant events occurred and the origins of the people in the area remain very obscure. In this paper, we present data from the analyses of both Y chromosomal and mitochondrial DNA (mtDNA derived from human remains excavated from the Xiaohe cemetery, the oldest archeological site with human remains discovered in the Tarim Basin thus far. Results Mitochondrial DNA analysis showed that the Xiaohe people carried both the East Eurasian haplogroup (C and the West Eurasian haplogroups (H and K, whereas Y chromosomal DNA analysis revealed only the West Eurasian haplogroup R1a1a in the male individuals. Conclusion Our results demonstrated that the Xiaohe people were an admixture from populations originating from both the West and the East, implying that the Tarim Basin had been occupied by an admixed population since the early Bronze Age. To our knowledge, this is the earliest genetic evidence of an admixed population settled in the Tarim Basin.

  10. Evidence that a West-East admixed population lived in the Tarim Basin as early as the early Bronze Age.

    Science.gov (United States)

    Li, Chunxiang; Li, Hongjie; Cui, Yinqiu; Xie, Chengzhi; Cai, Dawei; Li, Wenying; Mair, Victor H; Xu, Zhi; Zhang, Quanchao; Abuduresule, Idelisi; Jin, Li; Zhu, Hong; Zhou, Hui

    2010-02-17

    The Tarim Basin, located on the ancient Silk Road, played a very important role in the history of human migration and cultural communications between the West and the East. However, both the exact period at which the relevant events occurred and the origins of the people in the area remain very obscure. In this paper, we present data from the analyses of both Y chromosomal and mitochondrial DNA (mtDNA) derived from human remains excavated from the Xiaohe cemetery, the oldest archeological site with human remains discovered in the Tarim Basin thus far. Mitochondrial DNA analysis showed that the Xiaohe people carried both the East Eurasian haplogroup (C) and the West Eurasian haplogroups (H and K), whereas Y chromosomal DNA analysis revealed only the West Eurasian haplogroup R1a1a in the male individuals. Our results demonstrated that the Xiaohe people were an admixture from populations originating from both the West and the East, implying that the Tarim Basin had been occupied by an admixed population since the early Bronze Age. To our knowledge, this is the earliest genetic evidence of an admixed population settled in the Tarim Basin.

  11. Ancient East Polynesian voyaging spheres: new evidence from the Vitaria Adze Quarry (Rurutu, Austral Islands)

    OpenAIRE

    radu iovita; Eric West; John Sinton; Barry Rolett

    2015-01-01

    The use of adze sourcing to study interaction spheres opens new perspectives on ancient Polynesian voyaging. Our work contributes to this effort by documenting the discovery and geochemical signature of the Vitaria Adze Quarry, a major adze quarry complex in the central East Polynesia core area. We present WD-XRF geochemical data for the Vitaria raw material and ethnographically collected adzes from Raivavae and Tubuai Islands, also part of the Australs. Comparison of our results with previou...

  12. Evidence of a Cooler Continental Climate in East China during the Warm Early Cenozoic.

    Science.gov (United States)

    Zhang, Qian-Qian; Smith, Thierry; Yang, Jian; Li, Cheng-Sen

    2016-01-01

    The early Cenozoic was characterized by a very warm climate especially during the Early Eocene. To understand climatic changes in eastern Asia, we reconstructed the Early Eocene vegetation and climate based on palynological data of a borehole from Wutu coal mine, East China and evaluated the climatic differences between eastern Asia and Central Europe. The Wutu palynological assemblages indicated a warm temperate vegetation succession comprising mixed needle- and broad-leaved forests. Three periods of vegetation succession over time were recognized. The changes of palynomorph relative abundance indicated that period 1 was warm and humid, period 2 was relatively warmer and wetter, and period 3 was cooler and drier again. The climatic parameters estimated by the coexistence approach (CA) suggested that the Early Eocene climate in Wutu was warmer and wetter. Mean annual temperature (MAT) was approximately 16°C and mean annual precipitation (MAP) was 800-1400 mm. Comparison of the Early Eocene climatic parameters of Wutu with those of 39 other fossil floras of different age in East China, reveals that 1) the climate became gradually cooler during the last 65 million years, with MAT dropping by 9.3°C. This cooling trend coincided with the ocean temperature changes but with weaker amplitude; 2) the Early Eocene climate was cooler in East China than in Central Europe; 3) the cooling trend in East China (MAT dropped by 6.9°C) was gentler than in Central Europe (MAT dropped by 13°C) during the last 45 million years.

  13. Evidence of a Cooler Continental Climate in East China during the Warm Early Cenozoic.

    Directory of Open Access Journals (Sweden)

    Qian-Qian Zhang

    Full Text Available The early Cenozoic was characterized by a very warm climate especially during the Early Eocene. To understand climatic changes in eastern Asia, we reconstructed the Early Eocene vegetation and climate based on palynological data of a borehole from Wutu coal mine, East China and evaluated the climatic differences between eastern Asia and Central Europe. The Wutu palynological assemblages indicated a warm temperate vegetation succession comprising mixed needle- and broad-leaved forests. Three periods of vegetation succession over time were recognized. The changes of palynomorph relative abundance indicated that period 1 was warm and humid, period 2 was relatively warmer and wetter, and period 3 was cooler and drier again. The climatic parameters estimated by the coexistence approach (CA suggested that the Early Eocene climate in Wutu was warmer and wetter. Mean annual temperature (MAT was approximately 16°C and mean annual precipitation (MAP was 800-1400 mm. Comparison of the Early Eocene climatic parameters of Wutu with those of 39 other fossil floras of different age in East China, reveals that 1 the climate became gradually cooler during the last 65 million years, with MAT dropping by 9.3°C. This cooling trend coincided with the ocean temperature changes but with weaker amplitude; 2 the Early Eocene climate was cooler in East China than in Central Europe; 3 the cooling trend in East China (MAT dropped by 6.9°C was gentler than in Central Europe (MAT dropped by 13°C during the last 45 million years.

  14. Evidence of a Cooler Continental Climate in East China during the Warm Early Cenozoic

    Science.gov (United States)

    Zhang, Qian-Qian; Smith, Thierry; Yang, Jian; Li, Cheng-Sen

    2016-01-01

    The early Cenozoic was characterized by a very warm climate especially during the Early Eocene. To understand climatic changes in eastern Asia, we reconstructed the Early Eocene vegetation and climate based on palynological data of a borehole from Wutu coal mine, East China and evaluated the climatic differences between eastern Asia and Central Europe. The Wutu palynological assemblages indicated a warm temperate vegetation succession comprising mixed needle- and broad-leaved forests. Three periods of vegetation succession over time were recognized. The changes of palynomorph relative abundance indicated that period 1 was warm and humid, period 2 was relatively warmer and wetter, and period 3 was cooler and drier again. The climatic parameters estimated by the coexistence approach (CA) suggested that the Early Eocene climate in Wutu was warmer and wetter. Mean annual temperature (MAT) was approximately 16°C and mean annual precipitation (MAP) was 800–1400 mm. Comparison of the Early Eocene climatic parameters of Wutu with those of 39 other fossil floras of different age in East China, reveals that 1) the climate became gradually cooler during the last 65 million years, with MAT dropping by 9.3°C. This cooling trend coincided with the ocean temperature changes but with weaker amplitude; 2) the Early Eocene climate was cooler in East China than in Central Europe; 3) the cooling trend in East China (MAT dropped by 6.9°C) was gentler than in Central Europe (MAT dropped by 13°C) during the last 45 million years. PMID:27196048

  15. COAL MINING OPERATIONS AND ITS IMPACT ON SECTORAL AND REGIONAL AREA: EVIDENCE OF EAST KALIMANTAN, INDONESIA

    Directory of Open Access Journals (Sweden)

    Rian Hilmawan

    2016-12-01

    Full Text Available Mining sector plays important roles for Indonesian economic performance, especially in East Kalimantan. This study investigates: (a whether economic linkages of the mining sector related with other economic sectors in East Kalimantan, (b who gets benefit from such mining activities; (c how is the impact of mining sector for rural and urban households; and (d what happens if coal mining, oil and gas productions are completely depleted. The quantitative analysis framework using Input-Output and Social Accounting Matrix Tables in period 2009-2010 has been implemented as main data set. The result shows that mining sector was underdeveloped sector in East Kalimantan, including Kutai Kartanegara district. Activities from mining sector tended to give benefit for the owners of capital, which is larger than that benefit for workers employed. Structural Path Analysis (SPA shows that urban households gain the greatest advantages from the activities of this sector. The result also shows that the total output decreased by 65.12% when the mining, oil and gas dissapeared. A drastic reducing income after mining and oil and gas era will have an impact on the decline in the purchasing power in the region. However, the interesting finding of this research shows that the loss of mining and oil or gas sectors actually increases the strength of employment multiplier by 19%.

  16. Population Genetic Structure and Evidence of Demographic Expansion of the Ayu (Plecoglossus altivelis in East Asia

    Directory of Open Access Journals (Sweden)

    Ye-Seul Kwan

    2012-10-01

    Full Text Available Plecoglossus altivelis (ayu is an amphidromous fish widely distributed in Northeastern Asia from the East China Sea to the northern Japanese coastal waters, encompassing the Korean Peninsula within its range. The shore lines of northeastern region in Asia have severely fluctuated following glaciations in the Quaternary. In the present study, we investigate the population genetic structure and historical demographic change of P. altivelis at a population level in East Asia. Analysis of molecular variance (AMOVA based on 244 mitochondrial control region DNA sequences clearly showed that as the sampling scope extended to a larger geographic area, genetic differentiation began to become significant, particularly among Northeastern populations. A series of hierarchical AMOVA could detect the genetic relationship of three closely located islands between Korea and Japan that might have been tightly connected by the regional Tsushima current. Neutrality and mismatch distribution analyses revealed a strong signature of a recent population expansion of P. altivelis in East Asia, estimated at 126 to 391 thousand years ago during the late Pleistocene. Therefore it suggests that the present population of P. altivelis traces back to its approximate demographic change long before the last glacial maximum. This contrasts our a priori expectation that the most recent glacial event might have the most crucial effect on the present day demography of marine organisms through bottleneck and subsequent increase of effective population size in this region.

  17. Seismic imaging of glaciomarine sediments of Antarctica: Optimizing the acquisition parameters

    Digital Repository Service at National Institute of Oceanography (India)

    Pandey, D.; Chaubey, A.K.; Rajan, S.

    of Marine Sciences Vol. 37(4), December 2008, pp. 412-418 Seismic imaging of glaciomarine sediments of Antarctica: Optimizing the acquisition parameters Dhananjai Pandey1*, Anil Chaubey2, S Rajan1 1National Centre for Antarctic and Ocean... discussions on the reflection signature of the glaciomarine sediments of the continental slope and rise off Prydz Bay in east Antarctica in terms of depositional processes. The present study is based on synthetic seismogram modeling using finite...

  18. Ozone Hole Over Antarctica

    Science.gov (United States)

    2002-01-01

    These images from the Total Ozone Mapping Spectrometer (TOMS) show the progressive depletion of ozone over Antarctica from 1979 to 1999. This 'ozone hole' has extended to cover an area as large as 10.5 million square miles in September 1998. The previous record of 10.0 million square miles was set in 1996. The Antarctic ozone hole develops each year between late August and early October. Regions with higher levels of ozone are shown in red. NASA and NOAA instruments have been measuring Antarctic ozone levels since the early 1970s. Large regions of depleted ozone began to develop over Antarctica in the early 1980s. Ozone holes of substantial size and depth are likely to continue to form during the next few years, scientists hope to see a reduction in ozone loss as levels of ozone-destroying CFCs (chlorofluorocarbons) are gradually reduced. Credit: Images by Greg Shirah, NASA Goddard Space Flight Center Scientific Visualization Studio

  19. Trichoderma biodiversity in China: evidence for a North to South distribution of species in East Asia.

    Science.gov (United States)

    Zhang, Chu-long; Druzhinina, Irina S; Kubicek, Christian P; Xu, Tong

    2005-10-15

    Towards assessing the biodiversity and biogeography of Trichoderma, we have analyzed the occurrence of Trichoderma species in soil and litter from four areas in China: North (Hebei province), South-East (Zhejiang province), West (Himalayan, Tibet) and South-West (Yunnan province). One hundred and thirty five isolates were grouped according to tentative morphological identification. A representative 64 isolates were verified at the species level by the oligonucleotide barcode program TrichO Key v.1.0 and the custom BLAST server TrichoBLAST, using sequences of the ITS1 and 2 region of the rRNA cluster and from the longest intron of the tef1 (translation elongation factor 1-alpha) gene. Eleven known species (Trichoderma asperellum, T. koningii, T. atroviride, T. viride, T. velutinum, T. cerinum, T. virens, T. harzianum, T. sinensis, T. citrinoviride, T. longibrachiatum) and two putative new species (T. sp. C1, and T. sp. C2), distinguished from known species both by morphological characters and phylogenetic analysis, were identified. A significant difference in the occurrence of these species was found between the North (Hebei) and South-West (Yunnan) areas, which correlates with previously reported species distributions in Siberia and South-East Asia, respectively. As in previous studies, T. harzianum accounted for almost half of the biodiversity; although, in this study, it was exclusively found in the North, and was predominantly represented by an ITS1 and 2 haplotype, which has so far been rarely found elsewhere. This study therefore reveals a North-South gradient in species distribution in East Asia, and identifies Northern China as a potential center of origin of a unique haplotype of T. harzianum.

  20. Formal and informal Patronage among Jews in the Islamic East: evidence from the Cairo Geniza

    Directory of Open Access Journals (Sweden)

    Rustow, Marina

    2008-12-01

    Full Text Available This paper investigates the political culture of the Islamic East under Fatimid and Buwayhid rule (tenth-twelfth centuries via relationships between patrons, clients, protégés, and partners. The main body of evidence I utilize are letters and petitions from the Cairo Geniza that employ the same specialized vocabulary of patron-client relationships one finds in Arabic histories of the period: idioms referring to the exchange of benefit, reciprocal service, protection, oversight, patronage, and loyalty. The Geniza letters, written without regard for posterity, suggest that these idioms were used well beyond the courts and were understood and deployed by men and women, the literate and illiterate, the important and the inconsequential. Yet the use of certain terms in Judaeo-Arabic also differs from their use in Arabic: some reflect devaluation over time, while others hardened into formulaic phrases. These differences suggest that some forms of patronage did not thrive beyond the hothouse of the court; viewed from another perspective, they also suggest that even outside courtly literature, one can retrieve fossils of older forms of patronage in the terms used to describe relationships between leaders and their followers as well as among people more nearly equal in station. A society’s use of social metaphors reveals something of what its members value, what they choose to retain and perpetuate from the past, how they function in moments of crisis, and how successfully their rulers have managed to convince them of the legitimacy of the social and political order. Conversely, the vocabulary of patronage was a social technique that allowed Jews to conduct business, engage in politics and communal regulation, and to amass and retain followers in a variety of spheres, including that of the rabbinic academies who proffered the construction of Judaism that became hegemonic over the course of the Middle Ages.

    Este artículo aborda la cultura pol

  1. Weather and forecasting at Wilkins ice runway, Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Carpentier, Scott, E-mail: s.carpentier@bom.gov.a [Bureau of Meteorology, 111 Macquarie Street, Hobart, Tasmania, 7001 (Australia)

    2010-08-15

    Aviation forecasts for Wilkins ice runway in East Antarctica are developed within the conceptual framework of flow against a single dome shaped hill. Forecast challenges include the sudden onset of blizzards associated with the formation of an internal gravity wave; frontal weather; transient wake vortices and mesoscale lows; temperature limitations on runway use; and snow and fog events. These key weather aspects are presented within the context of synoptic to local scale climatologies and numerical weather prediction models.

  2. Late Quaternary surface circulation in the east equatorial South Atlantic: Evidence from Alkenone sea surface temperatures

    Science.gov (United States)

    Schneider, Ralph R.; Müller, Peter J.; Ruhland, GöTz

    1995-04-01

    Angola Basin and Walvis Ridge records of past sea surface temperatures (SST) derived from the alkenone Uk37 index are used to reconstruct the surface circulation in the east equatorial South Atlantic for the last 200,000 years. Comparison of SST estimates from surface sediments between 5° and 20°S with modern SST data suggests that the alkenone temperatures represent annual mean values of the surface mixed layer. Alkenone-derived temperatures for the warm climatic maxima of the Holocene and the penultimate interglacial are 1 to 4°C higher than latest Holocene values. All records show glacial to interglacial differences of about 3.5°C in annual mean SST, which is about 1.5°C greater than the difference estimated by CLIMAP (1981) for the eastern Angola Basin. At the Walvis Ridge, significant SST variance is observed at all of the Earth's orbital periodicities. SST records from the Angola Basin vary predominantly at 23- and 100-kyr periodicities. For the precessional cycle, SST changes at the Walvis Ridge correspond to variations of boreal summer insolation over Africa and lead ice volume changes, suggesting that the east equatorial South Atlantic is sensitive to African monsoon intensity via trade-wind zonality. Angola Basin SST records lag those from the Walvis Ridge and the equatorial Atlantic by about 3 kyr. The comparison of Angola Basin and Walvis Ridge SST records implies that the Angola-Benguela Front (ABF) (currently at about 14-16°S) has remained fairly stationary between 12° and 20°S (the limits of our cores) during the last two glacial-interglacial cycles. The temperature contrast associated with the ABF exhibits a periodic 23-kyr variability which is coherent with changes in boreal summer insolation over Africa. These observations suggest that surface waters north of the present ABF have not directly responded to monsoon-modulated changes in the trade-wind vector, that the central field of zonally directed trades in the southern hemisphere was not

  3. Market Discipline and Bank Risk Taking: Evidence from the East Asian Banking Sector

    Directory of Open Access Journals (Sweden)

    Fazelina Sahul Hamid

    2017-03-01

    Full Text Available The third pillar of the Basel II highlights the role of market discipline in easing the existing pressure on traditional monitoring measures like capital requirement and government supervision. This study test the effectiveness of market discipline in inducing prudential risk management practices among the East Asian banks over the 1995 to 2005 period. Market discipline is measured using information disclosure and interbank deposit holdings. We find that only the latter is an effective market discipline tool. However, the former becomes effective when market concentration is higher. We find that government owned, foreign owned and recapilatised banks are subject to market disciplining when disclosure in taken account but the opposite is true when interbank deposits is taken into account. Finally, we find that banks that disclose more risk related information hold more capital against their non-performing loan. The implications of the findings are discussed.

  4. Educational health inequalities in former Yugoslavia: evidence from the South-East European Social Survey Project.

    Science.gov (United States)

    Eikemo, Terje Andreas; Huisman, Martijn; Perlman, Francesca; Ringdal, Kristen

    2010-12-01

    An important gap in our knowledge of social inequalities in health is the former Yugoslavia, a region of culturally and historically diverse countries, with recent conflict. The aim of the present paper is to investigate relative and absolute inequalities in self-assessed health in former Yugoslavia (Bosnia-Herzegovina, Croatia, Kosovo, Macedonia, Montenegro, Slovenia and Serbia) by sex and education. The data source is the South-East European Social Survey Project fielded in December 2003 to Winter 2004, covering the former Yugoslavia with a total sample of 18 481 respondents. Data from Slovenia were obtained from the 2004-wave of the European Social Survey. The health outcome variables were self-reported general health (SRH) and limiting longstanding illness (LLI). Both absolute and relative educational health inequalities were present throughout the former Yugoslavia to a larger or lesser extent, although odds ratios (ORs) for LLI and SRH were not significant for Montenegrin women [LLI OR = 1.12, 95% confidence interval (CI): 0.92-1.37; SRH OR = 1.16, 95% CI: 0.96-1.40] and with respect to the reporting of LLI among Slovenian men (OR = 1.16, 95% CI: 0.96-1.44). Overall, Montenegro held the best position. The prevalence of poor health and the degree of relative inequality in self-assessed health in the former Yugoslavian countries were similar in order to one another, and to other East European countries during the same period. Influences on subjective health require further elucidation. Further research should study a wider range of health outcomes using larger survey samples and a wider range of cultural and other predictor variables.

  5. Evidence of debris flow occurrence after wildfire in upland catchments of south-east Australia

    Science.gov (United States)

    Nyman, Petter; Sheridan, Gary J.; Smith, Hugh G.; Lane, Patrick N. J.

    2011-02-01

    Numerous reports of "flash floods", "mud torrents" and "landslides" in burnt landscapes of south-east Australia were only recently linked to debris flows and recognised as a significant process that warrant more detailed investigation. This paper provides a systematic documentation of high-magnitude erosion events after wildfire in south-east Australia, focusing on small (fire runoff generated debris flows in Australia, so the discussion draws on literature from the western USA, where a large body of research has been dedicated to evaluating the risk posed by post-fire debris flows and their role in landscape processes. Typical features common to both systems include low infiltration capacity of burnt catchments; widespread sheet erosion and levee lined rills on steep upper hillslopes; and severe channel erosion initiated in response to convergent flow in previously un-scoured drainage lines. The depth of sheet erosion on surveyed slopes in the upper catchments (4.6 ± 0.96 mm to 18.4 ± 2.7 mm) indicates that hillslope material provides an important source of sediment. The average channel entrainment rate of three debris flows ranged from 0.6 to 1.4 m 3 m -1. Runoff generated debris flows were not recorded in wet or damp forest types suggesting that this process is unlikely to operate in these forest environments. One isolated case of mass failure generated debris flow was recorded in wet forest. The outcome of the study indicates that runoff generated debris flows in dry eucalypt forest are an important process to be considered during post-fire risk assessment of hydrological hazards.

  6. Widespread surface meltwater drainage in Antarctica

    Science.gov (United States)

    Kingslake, J.; Ely, J.; Das, I.; Bell, R. E.

    2016-12-01

    Surface meltwater is thought to cause ice-shelf disintegration, which accelerates the contribution of ice sheets to sea-level rise. Antarctic surface melting is predicted to increase and trigger further ice-shelf disintegration during this century. These climate-change impacts could be modulated by an active hydrological network analogous to the one in operation in Greenland. Despite some observations of Antarctic surface and sub-surface hydrological systems, large-scale active surface drainage in Antarctica has rarely been studied. We use satellite imagery and aerial photography to reveal widespread active hydrology on the surface of the Antarctic Ice Sheet as far south as 85o and as high as 1800 m a.s.l., often near mountain peaks that protrude through the ice (nunataks) and relatively low-albedo `blue-ice areas'. Despite predominantly sub-zero regional air temperatures, as simulated by a regional climate model, Antarctic active drainage has persisted for decades, transporting water through surface streams and feeding vast melt ponds up to 80 km long. Drainage networks (the largest are over 100 km in length) form on flat ice shelves, steep outlet glaciers and ice-sheet flanks across the West and East Antarctica Ice Sheets. Motivated by the proximity of many drainage systems to low-albedo rock and blue-ice areas, we hypothesize a positive feedback between exposed-rock extent, BIA formation, melting and ice-sheet thinning. This feedback relies on drainage moving water long distances from areas near exposed rock, across the grounding line onto and across ice shelves - a process we observe, but had previously thought to be unlikely in Antarctica. This work highlights previously-overlooked processes, not captured by current regional-scale models, which may accelerate the retreat of the Antarctic Ice Sheet.

  7. Middle East respiratory syndrome coronavirus (MERS-CoV): evidence and speculations.

    Science.gov (United States)

    Abdel-Moneim, Ahmed S

    2014-07-01

    In 2012, a novel human coronavirus emerged and was tentatively named "Middle East respiratory syndrome coronavirus" (MERS-CoV). The high mortality rate of MERS-CoV focused attention on the ecology of the virus. It has been found that MERS-CoV belongs to the group C lineage of the genus Betacoronavirus. Coronavirus surveillance studies in different populations of bats have suggested that they are probable reservoirs for this novel virus, and phylogenetic analysis of both the spike (S1) and RNA-dependent RNA polymerase proteins of MERS-CoV have revealed that it is related to bat viruses. Recently, the MERS-CoV and its neutralizing antibodies were detected in dromedary camels. Despite the limited number of reported cases of person-to-person transmission, the rapid evolution of the virus poses a continuous threat to humans worldwide. This paper reviews the current state of knowledge regarding the virology, clinical spectrum, evolution, diagnosis and treatment of MERS-CoV infections.

  8. Meteorites, Ice, and Antarctica

    Science.gov (United States)

    Cassidy, William A.

    2003-08-01

    Bill Cassidy led meteorite recovery expeditions in the Antarctic for fifteen years and his searches have resulted in the collection of thousands of meteorite specimens from the ice. This personal account of his field experiences on the U.S. Antarctic Search for Meteorites Project reveals the influence the work has had on our understanding of the moon, Mars and the asteroid belt. Cassidy describes the hardships and dangers of fieldwork in a hostile environment, as well as the appreciation he developed for its beauty. William Cassidy is Emeritus Professor of Geology and Planetary Science at the University of Pittsburgh. He initiated the U.S. Antarctic Search for Meteorites (ANSMET) nroject and led meteorite recovery expeditions in Antarctica in1976. His name is found attached to a mineral (cassidyite), on the map of Antarctica (Cassidy Glacier), and in the Catalog of Asteroids (3382 Cassidy). Profiled in "American Men of Science," and "Who's Who in America," he is also a recipient of The Antarctic Service Medal from the United States and has published widely in Science, Meteoritics and Planetary Science, and The Journal of Geophysical Research.

  9. Accelerated ice-sheet mass loss in Antarctica from 18-year satellite laser ranging measurements

    Directory of Open Access Journals (Sweden)

    Shuanggen Jin

    2016-02-01

    Full Text Available Accurate estimate of the ice-sheet mass balance in Antarctic is very difficult due to complex ice sheet condition and sparse in situ measurements. In this paper, the low-degree gravity field coefficients of up to degree and order 5 derived from Satellite Laser Ranging (SLR measurements are used to determine the ice mass variations in Antarctica for the period 1993–2011. Results show that the ice mass is losing with -36±13 Gt/y in Antarctica, -42±11 Gt/y in the West Antarctica and 6±10 Gt/y in the East Antarctica from 1993 to 2011. The ice mass variations from the SLR 5×5 have a good agreement with the GRACE 5×5, GRACE 5×5 (1&2 and GRACE (60×60 for the entire continent since 2003, but degree 5 from SLR is not sufficient to quantify ice losses in West and East Antarctica, respectively. The rate of ice loss in Antarctica is -28±17 Gt/y for 1993-2002 and -55±17 Gt/y for 2003-2011, indicating significant accelerated ice mass losses since 2003. Furthermore, the results from SLR are comparable with GRACE measurements.

  10. Evidence of Historical Mining Impacts on Saltmarshes from east Cornwall, UK

    Science.gov (United States)

    Iurian, Andra-Rada; Taylor, Alex; Millward, Geoff; Blake, William

    2016-04-01

    In landscapes with extensive mining history, saltmarshes can become sinks for contaminants that are vulnerable to release with sea-level rise and increased storminess. Given the prolonged residence time of heavy metals in the environment, data is urgently required to contextualise the impacts of past and present mining and pollution events and provide a baseline against which to assess Water Framework Directive (WFD) (2000/60/EC) compliance within an integrated catchment management framework. The geology of east Cornwall, UK (with intrusions of granite into the surrounding sedimentary rocks) was favourable for a prosperous mining industry, although large scale operations did not start until about 1830. Tin, cooper, lead and tungsten were the most important ores in the region. In order to quantify the spatial and temporal extent of contamination from past mining, sediment cores were collected from three saltmarshes, namely: Antony Marsh and Treluggan Marsh on the Lower Basin of River Lynher, and Port Eliot Marsh on the Lower Basin of River Tiddy. Core sections at 1 cm intervals were analysed by gamma-ray spectrometry for Pb-210, Ra-226, Cs-137 and Am-241, and the well-established Constant Rate of Supply (CRS) model was employed to derive Pb-210 geochronology with bomb-derived Cs-137 and Am-241 as independent chronological markers. The geochronological data provided the sedimentary accumulation and temporal context for the study. In terms of sediment quality with respect to mining pollution, core sections were analysed using Q-ICP-MS techniques and, additionally, WD-XRF instrumentation at Plymouth University. Measurements were performed for target elements that are normally associated with mining and smelting activities (e.g. Pb, Cu, Sn, Zn, Cr, Cd, etc.), and lithogenic elements (e.g. Fe, Al, Ti) that allow enrichment factors for the anthropogenically-derived elements to be determined. The grain size distribution was determined to identify storminess events and to

  11. Optimal screening mammography reading volumes; evidence from real life in the East Midlands region of the NHS Breast Screening Programme

    Energy Technology Data Exchange (ETDEWEB)

    Cornford, E., E-mail: eleanor.cornford@nuh.nhs.u [Nottingham Breast Institute, Nottingham University Hospitals, Nottingham (United Kingdom); Reed, J.; Murphy, A. [East Midlands QA Reference centre, Nottingham (United Kingdom); Bennett, R. [Cancer Screening Evaluation Unit, Institute of Cancer Research, Sutton (United Kingdom); Evans, A. [Centre for Oncology and Molecular Medicine, University of Dundee (United Kingdom)

    2011-02-15

    Aim: To assess real-life reader performance as a function of both volume of mammograms read and reading experience in a multicentre cohort. Materials and methods: Thirty-seven film readers from the East Midlands Breast Screening Programme had 3 years of consecutive screen reading results available for comparison. Markers of screening performance as the first film reader [cancer detection rates, small cancer detection rates, recall rates, positive predictive value of recall (PPV), and missed cancers] were compared with both volume of films read and years of film reading experience. For reading volume, readers were categorized according to film reading volume over the 3 year period: <15,000 (i.e., on average less than the recommended 5000/year); 15-<20,000; 20-<25,000; and {>=}25,000. For years of experience, readers were categorized into the following groups: <5 years, 5-<10 years, 10-<15 years, and 15-<20 years. Results: There was no evidence to suggest a relationship between years of film reading experience and film-reading performance. For reading volume, there was a significant difference in the distribution of cancer-detection rate between the four groups (p = 0.01); however, there was no difference in small cancer-detection rates, missed cancers or PPV. The median cancer detection rate in the high-volume group ({>=}25,000 mammograms/3 years) was significantly lower than the other groups combined (6.9 per 1000 women screened versus 7.9 per 1000 women screened). The lowest median recall rate was also in the high-volume group, whilst those readers not meeting the NHSBSP minimum requirement had the highest median recall rate; however, there was borderline evidence to suggest a difference in the distribution of recall rates between the four groups. Conclusion: The data from the East Midlands do not provide any evidence for reducing the threshold volume of 5000 cases /year. However, there appears to be an upper limit above which reader performance deteriorates in

  12. Establishing the evidence base for maintaining biodiversity and ecosystem function in the oil palm landscapes of South East Asia

    Science.gov (United States)

    Foster, William A.; Snaddon, Jake L.; Turner, Edgar C.; Fayle, Tom M.; Cockerill, Timothy D.; Ellwood, M. D. Farnon; Broad, Gavin R.; Chung, Arthur Y. C.; Eggleton, Paul; Khen, Chey Vun; Yusah, Kalsum M.

    2011-01-01

    The conversion of natural forest to oil palm plantation is a major current threat to the conservation of biodiversity in South East Asia. Most animal taxa decrease in both species richness and abundance on conversion of forest to oil palm, and there is usually a severe loss of forest species. The extent of loss varies significantly across both different taxa and different microhabitats within the oil palm habitat. The principal driver of this loss in diversity is probably the biological and physical simplification of the habitat, but there is little direct evidence for this. The conservation of forest species requires the preservation of large reserves of intact forest, but we must not lose sight of the importance of conserving biodiversity and ecosystem processes within the oil palm habitat itself. We urgently need to carry out research that will establish whether maintaining diversity supports economically and ecologically important processes. There is some evidence that both landscape and local complexity can have positive impacts on biodiversity in the oil palm habitat. By intelligent manipulation of habitat complexity, it could be possible to enhance not only the number of species that can live in oil palm plantations but also their contribution to the healthy functioning of this exceptionally important and widespread landscape. PMID:22006968

  13. Evidence for distinct coastal and offshore communities of bottlenose dolphins in the north east Atlantic.

    Directory of Open Access Journals (Sweden)

    Machiel G Oudejans

    Full Text Available Bottlenose dolphin stock structure in the northeast Atlantic remains poorly understood. However, fine scale photo-id data have shown that populations can comprise multiple overlapping social communities. These social communities form structural elements of bottlenose dolphin (Tursiops truncatus [corrected] populations, reflecting specific ecological and behavioural adaptations to local habitats. We investigated the social structure of bottlenose dolphins in the waters of northwest Ireland and present evidence for distinct inshore and offshore social communities. Individuals of the inshore community had a coastal distribution restricted to waters within 3 km from shore. These animals exhibited a cohesive, fission-fusion social organisation, with repeated resightings within the research area, within a larger coastal home range. The offshore community comprised one or more distinct groups, found significantly further offshore (>4 km than the inshore animals. In addition, dorsal fin scarring patterns differed significantly between inshore and offshore communities with individuals of the offshore community having more distinctly marked dorsal fins. Specifically, almost half of the individuals in the offshore community (48% had characteristic stereotyped damage to the tip of the dorsal fin, rarely recorded in the inshore community (7%. We propose that this characteristic is likely due to interactions with pelagic fisheries. Social segregation and scarring differences found here indicate that the distinct communities are likely to be spatially and behaviourally segregated. Together with recent genetic evidence of distinct offshore and coastal population structures, this provides evidence for bottlenose dolphin inshore/offshore community differentiation in the northeast Atlantic. We recommend that social communities should be considered as fundamental units for the management and conservation of bottlenose dolphins and their habitat specialisations.

  14. Evidence for distinct coastal and offshore communities of bottlenose dolphins in the north east Atlantic.

    Science.gov (United States)

    Oudejans, Machiel G; Visser, Fleur; Englund, Anneli; Rogan, Emer; Ingram, Simon N

    2015-01-01

    Bottlenose dolphin stock structure in the northeast Atlantic remains poorly understood. However, fine scale photo-id data have shown that populations can comprise multiple overlapping social communities. These social communities form structural elements of bottlenose dolphin (Tursiops truncatus) [corrected] populations, reflecting specific ecological and behavioural adaptations to local habitats. We investigated the social structure of bottlenose dolphins in the waters of northwest Ireland and present evidence for distinct inshore and offshore social communities. Individuals of the inshore community had a coastal distribution restricted to waters within 3 km from shore. These animals exhibited a cohesive, fission-fusion social organisation, with repeated resightings within the research area, within a larger coastal home range. The offshore community comprised one or more distinct groups, found significantly further offshore (>4 km) than the inshore animals. In addition, dorsal fin scarring patterns differed significantly between inshore and offshore communities with individuals of the offshore community having more distinctly marked dorsal fins. Specifically, almost half of the individuals in the offshore community (48%) had characteristic stereotyped damage to the tip of the dorsal fin, rarely recorded in the inshore community (7%). We propose that this characteristic is likely due to interactions with pelagic fisheries. Social segregation and scarring differences found here indicate that the distinct communities are likely to be spatially and behaviourally segregated. Together with recent genetic evidence of distinct offshore and coastal population structures, this provides evidence for bottlenose dolphin inshore/offshore community differentiation in the northeast Atlantic. We recommend that social communities should be considered as fundamental units for the management and conservation of bottlenose dolphins and their habitat specialisations.

  15. Evidence for Distinct Coastal and Offshore Communities of Bottlenose Dolphins in the North East Atlantic

    Science.gov (United States)

    Oudejans, Machiel G.; Visser, Fleur; Englund, Anneli; Rogan, Emer; Ingram, Simon N.

    2015-01-01

    Bottlenose dolphin stock structure in the northeast Atlantic remains poorly understood. However, fine scale photo-id data have shown that populations can comprise multiple overlapping social communities. These social communities form structural elements of bottlenose dolphin (Tursiops truncatus) populations, reflecting specific ecological and behavioural adaptations to local habitats. We investigated the social structure of bottlenose dolphins in the waters of northwest Ireland and present evidence for distinct inshore and offshore social communities. Individuals of the inshore community had a coastal distribution restricted to waters within 3 km from shore. These animals exhibited a cohesive, fission-fusion social organisation, with repeated resightings within the research area, within a larger coastal home range. The offshore community comprised one or more distinct groups, found significantly further offshore (>4 km) than the inshore animals. In addition, dorsal fin scarring patterns differed significantly between inshore and offshore communities with individuals of the offshore community having more distinctly marked dorsal fins. Specifically, almost half of the individuals in the offshore community (48%) had characteristic stereotyped damage to the tip of the dorsal fin, rarely recorded in the inshore community (7%). We propose that this characteristic is likely due to interactions with pelagic fisheries. Social segregation and scarring differences found here indicate that the distinct communities are likely to be spatially and behaviourally segregated. Together with recent genetic evidence of distinct offshore and coastal population structures, this provides evidence for bottlenose dolphin inshore/offshore community differentiation in the northeast Atlantic. We recommend that social communities should be considered as fundamental units for the management and conservation of bottlenose dolphins and their habitat specialisations. PMID:25853823

  16. Mineral resources potential of Antarctica

    National Research Council Canada - National Science Library

    Splettstoesser, John F; Dreschhoff, Gisela A. M

    1990-01-01

    .... This volume includes not only papers that are the culmination of many years of research conducted in Antarctica by leading scientists, but also additional studies from the United States, Australia...

  17. Mineral resources potential of Antarctica

    National Research Council Canada - National Science Library

    Splettstoesser, John F; Dreschhoff, Gisela A. M

    1990-01-01

    .... This volume of the Antarctic Research Series results from an attempt to assemble a summary of current factual knowledge and scientific data related to issues of mineral resources in Antarctica...

  18. Triassic amphibian from Antarctica.

    Science.gov (United States)

    Barrett, P J; Baillie, R J; Colbert, E H

    1968-08-02

    A fossil bone fragment-the first record of tetrapod life from Antarctica-was found near Graphite Peak in the upper Beardmore Glacier area (85 degrees 3.3'S; 172 degrees 19'E). The fragment was embedded in a pebbly quartzose sandstone, probably of fluvial origin, in the lower part of the Triassic Fremouw Formation (as yet undefined), which contains Dicroidium in the upper part. The fossil horizon is only 76 meters, stratigraphically, above the Glossopteris-bearing Buckley Formation, a coal-bearing sequence of Permian age. The bone fragment is the back portion of a left mandibular ramus of a labyrinthodont amphibian. This identification is based on the characteristic labyrinthodont external surface sculpturing, with indications of "mucous grooves," as well as on other osteological features.

  19. Landscape evolution of Antarctica

    Science.gov (United States)

    Jamieson, S.S.R.; Sugden, D.E.

    2007-01-01

    The relative roles of fluvial versus glacial processes in shaping the landscape of Antarctica have been debated since the expeditions of Robert Scott and Ernest Shackleton in the early years of the 20th century. Here we build a synthesis of Antarctic landscape evolution based on the geomorphology of passive continental margins and former northern mid-latitude Pleistocene ice sheets. What makes Antarctica so interesting is that the terrestrial landscape retains elements of a record of change that extends back to the Oligocene. Thus there is the potential to link conditions on land with those in the oceans and atmosphere as the world switched from a greenhouse to a glacial world and the Antarctic ice sheet evolved to its present state. In common with other continental fragments of Gondwana there is a fluvial signature to the landscape in the form of the coastal erosion surfaces and escarpments, incised river valleys, and a continent-wide network of river basins. A selective superimposed glacial signature reflects the presence or absence of ice at the pressure melting point. Earliest continental-scale ice sheets formed around 34 Ma, growing from local ice caps centered on mountain massifs, and featured phases of ice-sheet expansion and contraction. These ice masses were most likely cold-based over uplands and warm-based across lowlands and near their margins. For 20 million years ice sheets fluctuated on Croll-Milankovitch frequencies. At ~14 Ma the ice sheet expanded to its maximum and deepened a preexisting radial array of troughs selectively through the coastal mountains and eroded the continental

  20. Long-Term Variability of Surface Albedo and Its Correlation with Climatic Variables over Antarctica

    Directory of Open Access Journals (Sweden)

    Minji Seo

    2016-11-01

    Full Text Available The cryosphere is an essential part of the earth system for understanding climate change. Components of the cryosphere, such as ice sheets and sea ice, are generally decreasing over time. However, previous studies have indicated differing trends between the Antarctic and the Arctic. The South Pole also shows internal differences in trends. These phenomena indicate the importance of continuous observation of the Polar Regions. Albedo is a main indicator for analyzing Antarctic climate change and is an important variable with regard to the radiation budget because it can provide positive feedback on polar warming and is related to net radiation and atmospheric heating in the mainly snow- and ice-covered Antarctic. Therefore, in this study, we analyzed long-term temporal and spatial variability of albedo and investigated the interrelationships between albedo and climatic variables over Antarctica. We used broadband surface albedo data from the Satellite Application Facility on Climate Monitoring and data for several climatic variables such as temperature and Antarctic oscillation index (AAO during the period of 1983 to 2009. Time series analysis and correlation analysis were performed through linear regression using albedo and climatic variables. The results of this research indicated that albedo shows two trends, west trend and an east trend, over Antarctica. Most of the western side of Antarctica showed a negative trend of albedo (about −0.0007 to −0.0015 year−1, but the other side showed a positive trend (about 0.0006 year−1. In addition, albedo and surface temperature had a negative correlation, but this relationship was weaker in west Antarctica than in east Antarctica. The correlation between albedo and AAO revealed different relationships in the two regions; west Antarctica had a negative correlation and east Antarctica showed a positive correlation. In addition, the correlation between albedo and AAO was weaker in the west. This

  1. Antarctica and the strategic plan for biodiversity.

    Science.gov (United States)

    Chown, Steven L; Brooks, Cassandra M; Terauds, Aleks; Le Bohec, Céline; van Klaveren-Impagliazzo, Céline; Whittington, Jason D; Butchart, Stuart H M; Coetzee, Bernard W T; Collen, Ben; Convey, Peter; Gaston, Kevin J; Gilbert, Neil; Gill, Mike; Höft, Robert; Johnston, Sam; Kennicutt, Mahlon C; Kriesell, Hannah J; Le Maho, Yvon; Lynch, Heather J; Palomares, Maria; Puig-Marcó, Roser; Stoett, Peter; McGeoch, Melodie A

    2017-03-01

    The Strategic Plan for Biodiversity, adopted under the auspices of the Convention on Biological Diversity, provides the basis for taking effective action to curb biodiversity loss across the planet by 2020-an urgent imperative. Yet, Antarctica and the Southern Ocean, which encompass 10% of the planet's surface, are excluded from assessments of progress against the Strategic Plan. The situation is a lost opportunity for biodiversity conservation globally. We provide such an assessment. Our evidence suggests, surprisingly, that for a region so remote and apparently pristine as the Antarctic, the biodiversity outlook is similar to that for the rest of the planet. Promisingly, however, much scope for remedial action exists.

  2. Antarctica and the strategic plan for biodiversity.

    Directory of Open Access Journals (Sweden)

    Steven L Chown

    2017-03-01

    Full Text Available The Strategic Plan for Biodiversity, adopted under the auspices of the Convention on Biological Diversity, provides the basis for taking effective action to curb biodiversity loss across the planet by 2020-an urgent imperative. Yet, Antarctica and the Southern Ocean, which encompass 10% of the planet's surface, are excluded from assessments of progress against the Strategic Plan. The situation is a lost opportunity for biodiversity conservation globally. We provide such an assessment. Our evidence suggests, surprisingly, that for a region so remote and apparently pristine as the Antarctic, the biodiversity outlook is similar to that for the rest of the planet. Promisingly, however, much scope for remedial action exists.

  3. Present Permafrost Thaw in Central Yakutia, North-East Siberia: Surficial Geology and Hydrology Evidence

    Science.gov (United States)

    Czerniawska, Jolanta; Chlachula, Jiri

    2017-04-01

    Current climate change in the high-latitudes of Eurasia is a generally accepted phenomenon characterized by increased annual temperature values and marked weather anomalies observed in the sub-polar and polar regions. In the northern and NE Siberia, this trend of the MAT rise, documented particularly over the last three decades, is believed to account for the territorial lowland as well as insular mountain frozen ground thaw that in turn has triggered ecosystem feedbacks on the local as well as regional scales. In the northern regions of Yakutia, this is principally witnessed by accelerated near-surface dynamics of seasonally activated de-freezing grounds and inter-linked geomorphic and hydrological actions affecting large-scale tundra landscape settings. In the southern and central taiga-forest areas with perennial alpine and continuous permafrost conditions, respectively, an increased depth of the seasonally melted top-soil layers has become evident accompanied by thermokarst lake expansion and ground surface collapsing. Some cryogenic depressions generated from small gullies over the past decades eloquently demonstrate the intensity and scales of the current permafrost degradation in the Siberian North. The fluvial discharge is most dynamic in late spring to mid-summer because of the cumulative effect of snow-melting because of a high solar radiation and short intervals of torrential rains. Yet, the climate-change-dependent and most active geomorphic agent is the accelerated permafrost thaw seen in landslides and tundra-forest cover decay due to a higher water table. Numerous preserved biotic fossiliferous records Pleistocene and early Holocene in age are being exposed in this process providing unique palaeoecology evidence at particular sites. These climate-generated processes have mostly highly negative effects to the natural habitats (migratory animal routes and riverine biota due to an earlier ice-melting) as well as the local settlement communities

  4. Can earthquake fissures predispose hillslopes to landslides? - Evidence from Central and East Asia

    Science.gov (United States)

    Sidle, Roy C.; Gomi, Takashi; Rajapbaev, Muslim; Chyngozhoev, Nurstan

    2017-04-01

    Factors affecting earthquake-initiated landslides include earthquake magnitude, focal depth, and seismic wave propagation and attenuation. In contrast to rainfall-initiated landslides, earthquake-induced landslides often occur on convex slopes and near ridgelines. Here we present evidence from Fergana Basin, Kyrgyzstan and Kumamoto, Japan on how fissures developed during earthquakes may promote subsequent initiation of rainfall-triggered landslides. More than 1800 recent major landslides in hilly terrain and soft sediments of the Fergana Basin have been largely attributed to accumulation of heavy rainfall and snowmelt. While no large earthquakes have occurred in the Fergana Basin, smaller earthquakes have generated fissures near ridgelines and on convex slopes. The connection of fissures, developed years or decades before slope failure, with preferential transport of rainwater and runoff into the soil has not been previously investigated. Fissures have been observed to expand with time, particularly during subsequent minor earthquakes, further promoting preferential infiltration. Because the soil mantle does not have large contrasts in permeability that would define a slip plane for landslides, it appears that the position and depth of these fissures may control the location and depth of failures. Zones in the soil where surficial inputs of water are preferentially transported, augment natural subsurface accumulation of antecedent rainfall. Many landslides in the eastern Fergana Basin occur after several months of accumulated precipitation and groundwater has been observed emerging on critical hillside locations (near ridgelines and on convex slopes) prior to slope failure. During the 2016 Kumamoto Earthquake (M 7.3), many landslides were triggered in forest and grassland hillslopes near Mount Aso. All of these earthquakes were shallow (focal depths about 10 km), causing high shaking intensity and ground rupturing. Because soils were relatively dry during these

  5. Dynamics of the ice mass in Antarctica in the time of warming

    Directory of Open Access Journals (Sweden)

    V. M. Kotlyakov

    2017-01-01

    Full Text Available The modern age of global warming affect the general state of the Antarctic ice sheet and its mass balance. Studies of the Southern polar region of the Earth during the International Geophysical Year  (1957–1958 called the assumption of growth in the modern ice mass in East Antarctica. However, with the development of new methods, this conclusion has been questioned. At the turn of the century the study of global processes Earth started to use the satellite radar or laser altimetry and satellite gravimetry, which allows determining change of different masses on the Earth, including ice bodies. From the beginning of the XXI century, these methods have been used to calculate the continental ice balance. In our study, we analyze different data of recent years, supporting the earlier conclusion on continued growth of the ice mass in East Antarctica. How‑ ever, in West Antarctica and the Antarctic Peninsula, on the contrary, there is increased loss of ice, leveling the increased income of ice mass of in the Central Antarctica. So all in all in the modern era of global warm‑ ing, the ice mass in Antarctica appears to be decreasing despite some growth of the East Antarctic ice sheet. Fluctuations of land ice mass reflect in the sea level variations, but in comparison with the scale of the Ant‑ arctic ice sheet its contribution to sea‑level rise is not so significant. The main reason for this is that the mass accumulation in East Antarctica with significant probability prevails over the ice outflow.

  6. Monitoring of a southern giant petrel Macronectes giganteus population on the Frazier Islands, Wilkes Land, Antarctica

    NARCIS (Netherlands)

    Creuwels, J.C S; Stark, J.S.; Woehler, E.J.; van Franeker, J.A; Ribic, C.A.

    Since 1956, Southern Giant Petrels on the Frazier Islands, East Antarctica, have been counted with different census techniques, sometimes varying within seasons and among islands, which hindered analysis of the data. Protective measures for the islands from 1986 onwards have increased the need for

  7. Monitoring of a southern giant petrel Macronectes giganteus population on the Frazier Islands, Wilkes Land, Antarctica

    NARCIS (Netherlands)

    Creuwels, J.C.S.; Stark, J.S.; Woehler, E.J.; Franeker, van J.A.; Ribic, C.A.

    2005-01-01

    Since 1956, Southern Giant Petrels on the Frazier Islands, East Antarctica, have been counted with different census techniques, sometimes varying within seasons and among islands, which hindered analysis of the data. Protective measures for the islands from 1986 onwards have increased the need for

  8. Stable isotope evidence for shifting Mediterranean climatic influences in Western Romania, East-Central Europe

    Science.gov (United States)

    Perşoiu, Aurel; Viorica, Nagavciuc; Carmen, Bădăluţă

    2015-04-01

    The stable isotopic composition of oxygen and hydrogen in precipitation, preserved in various sedimentary archives (speleothems, cave ice, tree rings) is being intensively used to reconstruct past climatic variability in western Romania. These studies heavily rely on the assumption that air temperature is the main factor controlling the isotopic composition of precipitation and hence this climatic parameter is the one reconstructed. However, ongoing monitoring studies are increasingly showing that this, especially along Romania's western border, moisture source is playing an important role in determining the isotopic composition of precipitation, hence complicating the simplistic picture outlined above. One of the main factors influencing climate variability in Romania is the North Atlantic Oscillation (NAO), a measure of the strength of the Icelandic Low and Azores High. Over During the positive NAO phase, the Atlantic storms are displaced northward and, although reduced in strength, Mediterranean cyclones penetrate further north. During the negative phase however, the Atlantic storms track is displaced southward, restricting the area receiving Mediterranean precipitation to the SW corner of Romania. Here we present isotopic evidence for a shift in the source of precipitation from North Atlantic to Mediterranean ones in SW Romania that masks the temperature signal recorded in the stable isotopic composition of precipitation. Between April 2012 and 2014 we have collected monthly samples of precipitation along a N-S transect in Western Romania and have analyzed them for their δ18O and δ2H. Precipitation in NW Romania are derived solely from North Atlantic sources, while those in SW Romania mix moisture evaporated from both the North Atlantic and the Mediterranean Sea. The northern boundary of the Mediterranean influence is shifting in phase with the NAO index and the position of the jet-stream. As a result, during periods with high NAO index, the stable isotope

  9. A reference model for crust and uppermost mantle beneath Antarctica

    Science.gov (United States)

    Shen, W.; Wiens, D.; Gerstoft, P.; Bromirski, P. D.; Stephen, R. A.; Aster, R. C.; Nyblade, A.; Winberry, J. P.; Huerta, A. D.; Anandakrishnan, S.; Hansen, S. E.; Wilson, T. J.; Heeszel, D.

    2016-12-01

    Since the last decade of the 20th Century, over 300 broad-band seismic stations have been deployed across the continent of Antarctica (e.g., temporary networks such as TAMSEIS, AGAP/GAMSEIS, POLENET/ANET, TAMNNET and RIS/DRIS by US geoscientists, as well as stations deployed by other countries). In this presentation, we discuss our recent effort that builds a reference crustal and uppermost mantle shear velocity (Vs) model for continental Antarctica based on those seismic arrays. The data analysis for this effort consists of four steps. First, we compute ambient noise cross-correlations between all possible station pairs and use them to construct Rayleigh wave phase and group velocity maps at a continental scale. Coherence of the new maps with maps generated from teleseismic earthquake data from an earlier study (Heeszel et al., 2016) confirms the high quality of both maps and the minor difference helps quantify the map uncertainties. Second, we compute P receiver function waveforms for each station in Antarctica. Third, we collect Rayleigh waves generated by teleseismic earthquakes and measure their horizontal to vertical (H/V) ratio at each station. Fourth and finally, by combing all seismic measurements from the first three steps together with the phase velocity maps by Heeszel et al.(2016) using a non-linear Monte Carlo (MC) inversion algorithm, we built a 3-D model for the crust and uppermost mantle beneath continental Antarctica and its periphery to a depth of 150 km. This high resolution model, together with associated uncertainty estimates from the MC inversion, serve as a starting point for further improvement and geological interpretation. A variety of tectonic features, including a slower but highly heterogeneous West Antarctica and a much faster East Antarctica, are present in the 3D model. A better image of these features from the 3D model helps further investigation of the thermal and dynamic state of Antarctica's lithosphere and underlying

  10. My IGY in Antarctica

    Science.gov (United States)

    Bentley, Charles

    2012-01-01

    Dr Charles Bentley is the A.P. Crary Professor Emeritus of Geophysics, Department of Geology and Geophysics, University of Wisconsin-Madison. Dr. Bentley joined the Arctic Institute of North America in 1956 to participate in International Geophysical Year (IGY)-related activities in the Antarctic. He wintered over consecutively in 1957 and 1958 at Byrd Station, a station in the interior of West Antarctica that housed 24 men each winter - 12 Navy support people and 12 civilian scientists/technicians. During the austral summers, he also participated in over-snow traverses, first as co-leader, then leader (the other coleader went home after the first year). These traverses consisted of six men and three vehicles, and lasted several months. These traverses covered more than 1609 kilometers (1000 miles) of largely unmapped and unphotographed terrain. During these traverses, connections to Byrd Station were by radio (daily, when the transmission conditions were good enough) and roughly every 2 weeks by resupply flight.

  11. Pulsating star research from Antarctica

    Science.gov (United States)

    Chadid, Merieme

    2017-09-01

    This invited talk discusses the pulsating star research from the heart of Antarctica and the scientific polar challenges in the extreme environment of Antarctica, and how the new polar technology could cope with unresolved stellar pulsation enigmas and evolutionary properties challenges towards an understanding of the mysteries of the Universe. PAIX, the first robotic photometer Antarctica program, has been successfully launched during the polar night 2007. This ongoing program gives a new insight to cope with unresolved stellar enigmas and stellar oscillation challenges with a great opportunity to benefit from an access to the best astronomical site on Earth, Dome C. PAIX achieves astrophysical measurement time-series of stellar fields, challenging photometry from space. A continuous and an uninterrupted series of multi-color photometric observations has been collected each polar night - 150 days - without regular interruption, Earth's rotation effect. PAIX shows the first light curve from Antarctica and first step for the astronomy in Antarctica giving new insights in remote polar observing runs and robotic instruments towards a new technology.

  12. Can evidence from genome-wide association studies and positive natural selection surveys be used to evaluate the thrifty gene hypothesis in East Asians?

    Directory of Open Access Journals (Sweden)

    Xuan-Han Koh

    Full Text Available Body fat deposition and distribution differ between East Asians and Europeans, and for the same level of obesity, East Asians are at higher risks of Type 2 diabetes (T2D and other metabolic disorders. This observation has prompted the reclassifications of body mass index thresholds for the definitions of "overweight" and "obese" in East Asians. However, the question remains over what evolutionary mechanisms have driven the differences in adiposity morphology between two population groups that shared a common ancestor less than 80,000 years ago. The Thrifty Gene hypothesis has been suggested as a possible explanation, where genetic factors that allowed for efficient food-energy conversion and storage are evolutionarily favoured by conferring increased chances of survival and fertility. Here, we leveraged on the existing findings from genome-wide association studies and large-scale surveys of positive natural selection to evaluate whether there is currently any evidence to support the Thrifty Gene hypothesis. We first assess whether the existing genetic associations with obesity and T2D are located in genomic regions that are reported to be under positive selection, and if so, whether the risk alleles sit on the extended haplotype forms. In addition, we interrogate whether these risk alleles are the derived forms that differ from the ancestral alleles, and whether there is significant evidence of population differentiation at these SNPs between East Asian and European populations. Our systematic survey did not yield conclusive evidence to support the Thrifty Gene hypothesis as a possible explanation for the differences observed between East Asians and Europeans.

  13. Can evidence from genome-wide association studies and positive natural selection surveys be used to evaluate the thrifty gene hypothesis in East Asians?

    Science.gov (United States)

    Koh, Xuan-Han; Liu, Xuanyao; Teo, Yik-Ying

    2014-01-01

    Body fat deposition and distribution differ between East Asians and Europeans, and for the same level of obesity, East Asians are at higher risks of Type 2 diabetes (T2D) and other metabolic disorders. This observation has prompted the reclassifications of body mass index thresholds for the definitions of "overweight" and "obese" in East Asians. However, the question remains over what evolutionary mechanisms have driven the differences in adiposity morphology between two population groups that shared a common ancestor less than 80,000 years ago. The Thrifty Gene hypothesis has been suggested as a possible explanation, where genetic factors that allowed for efficient food-energy conversion and storage are evolutionarily favoured by conferring increased chances of survival and fertility. Here, we leveraged on the existing findings from genome-wide association studies and large-scale surveys of positive natural selection to evaluate whether there is currently any evidence to support the Thrifty Gene hypothesis. We first assess whether the existing genetic associations with obesity and T2D are located in genomic regions that are reported to be under positive selection, and if so, whether the risk alleles sit on the extended haplotype forms. In addition, we interrogate whether these risk alleles are the derived forms that differ from the ancestral alleles, and whether there is significant evidence of population differentiation at these SNPs between East Asian and European populations. Our systematic survey did not yield conclusive evidence to support the Thrifty Gene hypothesis as a possible explanation for the differences observed between East Asians and Europeans.

  14. Multiple meteoroid impact in Antarctica

    Science.gov (United States)

    Weihoupt, J. W.; Rice, A.; van der Hoeven, F.

    2006-12-01

    In the late 1950's, geophysical field parties undertaking gravity surveys across Antarctica observed over a large area of Wilkes Land (> 240km across) an exceptionally pronounced negative free air anomaly ((to -158.3 mgal). This area was later interpreted as a possible meteor impact site because the gravity profiles were similar to those of known impact sites (apparent rim structures, circular basins, central peaks or rings), they possessed appropriate aspect ratios (e.g., crater diameter vs crater depth), anomalously steep negative free air gravity anomaly gradients (to 4.71 mgal/km) were characteristic of impact craters and uncharacteristic of solely mantle-related or geologic crustal variations, etc. The condition of the ice covering the anomaly (heavily crevassed), the apparent lack of isostatic compensation with surrounding environs, etc suggested the impact was geologically recent and that perhaps a tektite strewn field was associated with it. The distance from the postulated impact to the Australian strewn field was appropriate as are the ages of the tektites there. This early work has been augmented with the detection of a dominant cluster of negative free air gravity anomalies crossing the continental-oceanic boundary, and the East and West Antarctic structural boundary (i.e., Transantarctic Mountains). These anomalies are coincident with complex subglacial craterform topographic features inferred from radiosounding (to -500m below MSL). The major interior positive free air gravity anomalies are associated with subglacial topographic highs. The elliptical distribution of the negative gravity anomalies resemble known multiple impact distributions (scatter ellipses with the larger anomalies forward and the lesser ones aft). This more recent information favors expanding the original proposal to that of a multiple meteoroid impact. The multiple impact hypotheses would explain aeromagnetic surveys revealing ring-shaped structures in the subglacial rock surface

  15. Meltwater produced by wind-albedo interaction stored in an East Antarctic ice shelf

    Science.gov (United States)

    Lenaerts, J. T. M.; Lhermitte, S.; Drews, R.; Ligtenberg, S. R. M.; Berger, S.; Helm, V.; Smeets, C. J. P. P.; Broeke, M. R. Van Den; van de Berg, W. J.; van Meijgaard, E.; Eijkelboom, M.; Eisen, O.; Pattyn, F.

    2017-01-01

    Surface melt and subsequent firn air depletion can ultimately lead to disintegration of Antarctic ice shelves causing grounded glaciers to accelerate and sea level to rise. In the Antarctic Peninsula, foehn winds enhance melting near the grounding line, which in the recent past has led to the disintegration of the most northerly ice shelves. Here, we provide observational and model evidence that this process also occurs over an East Antarctic ice shelf, where meltwater-induced firn air depletion is found in the grounding zone. Unlike the Antarctic Peninsula, where foehn events originate from episodic interaction of the circumpolar westerlies with the topography, in coastal East Antarctica high temperatures are caused by persistent katabatic winds originating from the ice sheet’s interior. Katabatic winds warm and mix the air as it flows downward and cause widespread snow erosion, explaining >3 K higher near-surface temperatures in summer and surface melt doubling in the grounding zone compared with its surroundings. Additionally, these winds expose blue ice and firn with lower surface albedo, further enhancing melt. The in situ observation of supraglacial flow and englacial storage of meltwater suggests that ice-shelf grounding zones in East Antarctica, like their Antarctic Peninsula counterparts, are vulnerable to hydrofracturing.

  16. Pulsating star research from Antarctica

    Directory of Open Access Journals (Sweden)

    Chadid Merieme

    2017-01-01

    PAIX, the first robotic photometer Antarctica program, has been successfully launched during the polar night 2007. This ongoing program gives a new insight to cope with unresolved stellar enigmas and stellar oscillation challenges with a great opportunity to benefit from an access to the best astronomical site on Earth, Dome C. PAIX achieves astrophysical measurement time-series of stellar fields, challenging photometry from space. A continuous and an uninterrupted series of multi-color photometric observations has been collected each polar night – 150 days – without regular interruption, Earth’s rotation effect. PAIX shows the first light curve from Antarctica and first step for the astronomy in Antarctica giving new insights in remote polar observing runs and robotic instruments towards a new technology.

  17. Mesoscale cyclogenesis dynamics over the southwestern Ross Sea, Antarctica

    Science.gov (United States)

    Carrasco, Jorge F.; Bromwich, David H.

    1993-07-01

    Previous work has shown that frequent mesoscale cyclogenesis adjacent to Franklin Island is linked to the strong and persistent katabatic winds from East Antarctica which funnel into Terra Nova Bay and then blow out over the southwestern Ross Sea. Four mesoscale cyclones that formed near Terra Nova Bay between February 16 and 20, 1988 are examined to more clearly define the governing mechanisms. These events are investigated using all available observations, including automatic weather station data, high-resolution satellite images, satellite soundings, and hemispheric synoptic analyses. The first two cyclones formed on low-level baroclinic zones established by the synoptic scale advection of warm moist air toward the cold continental air blowing gently from East Antarctica. In the second case, baroclinic instability of this small-scale cold front was apparently triggered by the enhanced upward vertical motion associated with the approach of a midtropospheric trough. The third mesocyclone formed shortly after on a baroclinic zone over the polar plateau; the second vortex completely disrupted the usual katabatic drainage over the plateau and forced warm moist air over the coastal slopes. All three cyclones moved to the north in the prevailing cyclonic flow, but the plateau vortex lasted for only 6 hours. The fourth mesoscale low formed in conjunction with an abrupt and intense surge of katabatic air from Terra Nova Bay which resharpened the coastal baroclinic zone. At the same time a transiting midtropospheric trough probably associated with lower tropospheric upward vertical motion apparently accelerated the katabatic winds and triggered the vortex formation. A similar katabatic wind-forced mesocyclone formed near Byrd Glacier. The two vortices moved to the east-southeast and northeast, respectively, apparently being steered by the generating katabatic airstreams, and merged just to the north of the Ross Ice Shelf. The combined vortex reintensified as another

  18. Multiproxy Evidence for a Positive Hydrological Budget during the Little Ice Age in the East African Rift, Kenya

    Science.gov (United States)

    Goman, M.; Ashley, G. M.; Hover, V. C.; Owen, R.

    2011-12-01

    Hominin evolution took place in Africa during the Plio-Pleistocene and climate change is thought to be a factor, with Africa experiencing a general cooling and increasing aridification over the last several million years. Today, the climate of the East African Rift Valley of Kenya is characterized as semi-arid with evapotranspiration four times precipitation. Water resources are a valuable commodity for the many millions of inhabitants of the Valley. The short instrumental record shows precipitation fluctuates at sub-decadal timeframes as a result of the ENSO cycle; while during prehistory variations in monsoonal precipitation occurred on Milankovitch timescales (i.e. African Humid Period). Both timescales exhibit significant impacts on the distribution of surface water. However, little is known regarding precipitation variability over sub-millennial timescales. Emerging paleoclimate data indicates that the near surface presence of water has also varied over century length timescales. We present paleoclimate data from multiple sites along a north-south 600 km transect of the Gregory Rift Valley (Kenya) that indicate the region experienced wetter conditions during the Little Ice Age (A.D. 1400-1850). Our reconstructions of landscape and climate during this time frame rely upon a multiproxy and interdisciplinary approach. We discuss data from a variety of environmental settings (e.g. lakes, wetlands, and springs) that indicate an overall increase in hydrologic balance. Evidence is derived from biologic microfossils such as pollen, diatom and testate amoebae assemblages as well as inorganic components of the sedimentary record and geomorphic changes. The data differs significantly from studies undertaken to the west in Uganda and the Congo, where negative hydrologic balances occurred during the Little Ice Age. While the atmospheric dynamics causing this disparity are not yet recognized, interactions between the Intertropical Convergence Zone and the Congo Air Boundary

  19. Potential methane reservoirs beneath Antarctica

    NARCIS (Netherlands)

    Wadham, J.L.; Arndt, S.|info:eu-repo/dai/nl/304835706; Tulaczyk, S.; Stibal, M.; Tranter, M.; Telling, J.; Lis, G.P.; Lawson, E.; Ridgwell, A.; Dubnick, A.; Sharp, M.J.; Anesio, A.M.; Butler, C.E.H.

    2012-01-01

    Once thought to be devoid of life, the ice-covered parts of Antarctica are now known to be a reservoir of metabolically active microbial cells and organic carbon. The potential for methanogenic archaea to support the degradation of organic carbon to methane beneath the ice, however, has not yet been

  20. Direct gravimetric determination of aerosol mass concentration in central antarctica.

    Science.gov (United States)

    Annibaldi, Anna; Truzzi, Cristina; Illuminati, Silvia; Scarponi, Giuseppe

    2011-01-01

    In Antarctica, experimental difficulties due to extreme conditions have meant that aerosol mass has rarely been measured directly by gravimetry, and only in coastal areas where concentrations were in the range of 1-7 μg m(-3). The present work reports on a careful differential weighing methodology carried out for the first time on the plateau of central Antarctica (Dome C, East Antarctica). To solve problems of accurate aerosol mass measurements, a climatic room was used for conditioning and weighing filters. Measurements were carried out in long stages of several hours of readings with automatic recording of temperature/humidity and mass. This experimental scheme allowed us to sample from all the measurements (up to 2000) carried out before and after exposure, those which were recorded under the most stable humidity conditions and, even more importantly, as close to each other as possible. The automatic reading of the mass allowed us in any case to obtain hundreds of measurements from which to calculate average values with uncertainties sufficiently low to meet the requirements of the differential weighing procedure (±0.2 mg in filter weighing, between ±7% and ±16% both in aerosol mass and concentration measurements). The results show that the average summer aerosol mass concentration (aerodynamic size ≤10 μm) in central Antarctica is about 0.1 μg m(-3), i.e., about 1/10 of that of coastal Antarctic areas. The concentration increases by about 4-5 times at a site very close to the station.

  1. The Possible Physical Barrier and Coastal Dispersal Strategy for Japanese Grenadier Anchovy, Coilia nasus in the East China Sea and Yellow Sea: Evidence from AFLP Markers

    Directory of Open Access Journals (Sweden)

    Zhi-Qiang Han

    2015-02-01

    Full Text Available In order to ascertain the taxonomic status of the Ariake Sea population of Japanese grenadier anchovy, Coilia nasus, and assess the contemporary possible genetic barrier between the west and east coastal waters of the East China Sea, we used amplified fragment length polymorphism (AFLP markers to detect the genetic structure of C. nasus, in the East China Sea and Yellow Sea. Eighty-one individuals of C. nasus were collected from five locations and 12 individuals of Coilia mystus were sampled from the Yangtze River Estuary. A total of 371 loci were detected by five primer combinations, 310 of which were polymorphic (83.56%. Analysis of molecular variation (AMOVA and pairwise fixation index (FST revealed significant genetic differentiation among five samples, indicating limited gene flow among populations. The dendrogram for populations by neighbor-joining (NJ cluster analysis provided evidence of a clear relationship between genetic and geographic patterns, supporting significant genetic differentiation between China coastal populations and Ariake Sea populations. Compared to the genetic divergence between C. nasus and C. mystus, the level of genetic differentiation between China and the Ariake Sea populations of C. nasus is obvious below the species level, indicating isolated populations of C. nasus in the Ariake Sea. Isolation by distance analysis revealed that direct ocean distance with deep-water at the continental slope and high salinity between west and east coastal waters of the East China Sea served as major physical barrier to C. nasus, supporting the coastal dispersal pattern in this estuarine species, and rejecting offshore dispersal strategy.

  2. Explosive seismic reflection data from dome Halfarryggen, Antarctica

    Science.gov (United States)

    Hofstede, Coen

    2010-05-01

    Here we present the results from a explosive seismic survey performed in January 2010, at the ice dome Halfarryggen, close to the ice shelf Ekströmisen in East Antarctica. The dome lies 120 km south east of the German research station Neumayer. Two 6 km long perpendicular lines were shot over the dome, large enough to capture the structure of the present Raymond bump. For recording we used a 60 channel 1500 m long snow streamer. To reduce spatial aliasing two shots were combined into one data record. The focus of the seismic survey lies upon the physics that can be extracted from the internal and basal ice reflections. This includes bed conditions, crystal orientation fabric and seismic wave velocities.

  3. Use of evidence-based practices in pregnancy and childbirth: South East Asia Optimising Reproductive and Child Health in Developing Countries project.

    Directory of Open Access Journals (Sweden)

    M Laopaiboon

    2008-07-01

    Full Text Available The burden of mortality and morbidity related to pregnancy and childbirth remains concentrated in developing countries. SEA-ORCHID (South East Asia Optimising Reproductive and Child Health In Developing countries is evaluating whether a multifaceted intervention to strengthen capacity for research synthesis, evidence-based care and knowledge implementation improves adoption of best clinical practice recommendations leading to better health for mothers and babies. In this study we assessed current practices in perinatal health care in four South East Asian countries and determined whether they were aligned with best practice recommendations.We completed an audit of 9550 medical records of women and their 9665 infants at nine hospitals; two in each of Indonesia, Malaysia and The Philippines, and three in Thailand between January-December 2005. We compared actual clinical practices with best practice recommendations selected from the Cochrane Library and the World Health Organization Reproductive Health Library. Evidence-based components of the active management of the third stage of labour and appropriately treating eclampsia with magnesium sulphate were universally practiced in all hospitals. Appropriate antibiotic prophylaxis for caesarean section, a beneficial form of care, was practiced in less than 5% of cases in most hospitals. Use of the unnecessary practices of enema in labour ranged from 1% to 61% and rates of episiotomy for vaginal birth ranged from 31% to 95%. Other appropriate practices were commonly performed to varying degrees between countries and also between hospitals within the same country.Whilst some perinatal health care practices audited were consistent with best available evidence, several were not. We conclude that recording of clinical practices should be an essential step to improve quality of care. Based on these findings, the SEA-ORCHID project team has been developing and implementing interventions aimed at increasing

  4. Use of evidence-based practices in pregnancy and childbirth: South East Asia Optimising Reproductive and Child Health in Developing Countries project.

    Science.gov (United States)

    Laopaiboon, M; Lumbiganon, P; McDonald, S J; Henderson-Smart, D J; Green, S; Crowther, C A

    2008-07-09

    The burden of mortality and morbidity related to pregnancy and childbirth remains concentrated in developing countries. SEA-ORCHID (South East Asia Optimising Reproductive and Child Health In Developing countries) is evaluating whether a multifaceted intervention to strengthen capacity for research synthesis, evidence-based care and knowledge implementation improves adoption of best clinical practice recommendations leading to better health for mothers and babies. In this study we assessed current practices in perinatal health care in four South East Asian countries and determined whether they were aligned with best practice recommendations. We completed an audit of 9550 medical records of women and their 9665 infants at nine hospitals; two in each of Indonesia, Malaysia and The Philippines, and three in Thailand between January-December 2005. We compared actual clinical practices with best practice recommendations selected from the Cochrane Library and the World Health Organization Reproductive Health Library. Evidence-based components of the active management of the third stage of labour and appropriately treating eclampsia with magnesium sulphate were universally practiced in all hospitals. Appropriate antibiotic prophylaxis for caesarean section, a beneficial form of care, was practiced in less than 5% of cases in most hospitals. Use of the unnecessary practices of enema in labour ranged from 1% to 61% and rates of episiotomy for vaginal birth ranged from 31% to 95%. Other appropriate practices were commonly performed to varying degrees between countries and also between hospitals within the same country. Whilst some perinatal health care practices audited were consistent with best available evidence, several were not. We conclude that recording of clinical practices should be an essential step to improve quality of care. Based on these findings, the SEA-ORCHID project team has been developing and implementing interventions aimed at increasing compliance with

  5. Antarctica and the strategic plan for biodiversity

    Science.gov (United States)

    Chown, Steven L.; Brooks, Cassandra M.; Terauds, Aleks; Le Bohec, Céline; van Klaveren-Impagliazzo, Céline; Whittington, Jason D.; Butchart, Stuart H. M.; Coetzee, Bernard W. T.; Collen, Ben; Convey, Peter; Gaston, Kevin J.; Gilbert, Neil; Gill, Mike; Höft, Robert; Johnston, Sam; Kennicutt, Mahlon C.; Kriesell, Hannah J.; Le Maho, Yvon; Lynch, Heather J.; Palomares, Maria; Puig-Marcó, Roser; Stoett, Peter; McGeoch, Melodie A.

    2017-01-01

    The Strategic Plan for Biodiversity, adopted under the auspices of the Convention on Biological Diversity, provides the basis for taking effective action to curb biodiversity loss across the planet by 2020—an urgent imperative. Yet, Antarctica and the Southern Ocean, which encompass 10% of the planet’s surface, are excluded from assessments of progress against the Strategic Plan. The situation is a lost opportunity for biodiversity conservation globally. We provide such an assessment. Our evidence suggests, surprisingly, that for a region so remote and apparently pristine as the Antarctic, the biodiversity outlook is similar to that for the rest of the planet. Promisingly, however, much scope for remedial action exists. PMID:28350825

  6. Raising Awareness on Health Impact of the Chemicals Used in Consumer Products: Empirical Evidence from East-Central Europe

    Directory of Open Access Journals (Sweden)

    Florin-Alexandru Luca

    2018-01-01

    Full Text Available Recent research and guidance provided by regulatory authorities address the growing concerns on the control of chemicals used in consumer products. In this context, this study responds to literature alerts emphasizing the need for promoting risk reduction by decreasing the use of damaging chemicals and raising public awareness on this issue. It focuses on East-Central Europe and investigates whether consumers are worried about the impact on health of chemicals, and whether they think there is enough information available in this sense. The study uses logistic regression in order to analyze the secondary data from Special Eurobarometer No. 416 (part of Eurobarometer Wave EB 81.3, European Commission, 2014, namely 27,998 interviews collected in all 28 EU countries, of which 11,460 are from East-Central Europe. The research reveals a profile of East-Central Europeans, who consider that they lack information on the topic, and identifies the most effective way of reaching these people according to their perceptions and habits. Reporting results on a representative sample in East-Central Europe, the study indicates the channels, sources of information, and trusted institutions in order to support a campaign for raising public awareness on the health impact of chemicals used in consumer products.

  7. Pressures of Partial Crystallization along the East Pacific Rise: Preliminary Results and Evidence for Deep Crustal Chambers?

    Science.gov (United States)

    Zerda, C.; Scott, J. L.; Barton, M.

    2013-12-01

    The fast spreading East Pacific Rise (EPR) between 8°N and 14°N is characterized by ~20 ridge axis discontinuities. Previous work has suggested that magmas erupted at some of these discontinuities, specifically at transform faults, partially crystallize at higher pressures than magmas erupted along 'normal' ridge segments. In order to evaluate the factors that control the plumbing systems of MORB, we have determined the pressures (P) of partial crystallization of magmas beneath the EPR from 8°N to 14°N using 2,837 published chemical analyses of basalt glasses. Pressures were calculated using the two different methods described by Herzberg, 2004 (H) and Kelley and Barton, 2008 (KB). These two methods are expected to yield minimum and maximum values for calculated pressures. However, for the samples used in this work both methods yield virtually identical pressures for the entire data set (average pressures: H=182.3×143.6 MPa and KB=200.9×153.3 MPa) and we elected to use results obtained with the KB method for detailed analysis of the results. Based on sample frequency, the EPR was divided into 10 sections that include 'normal' segments lacking axial discontinuities and segments that include discontinuities such as a transform fault, an overlapping spreading center (OSC), or a deviation from axial linearity, or one or more of these features. The average pressure of partial crystallization for 'normal' segments is 145.6×59.9 MPa, and is essentially constant along the whole length of the ridge studied. These results are consistent with crystallization at depths of ~ 5km near the base of the crust and, as with results obtained for the Juan da Fuca and Reykjanes ridge, provide no evidence for crystallization in the upper mantle along 'normal' ridge segments. The pressures of partial crystallization of magmas at or near axial discontinuities show a wider range than those for magmas erupted along normal ridge segments. The maximum pressures for samples from the

  8. Giant seismites and megablock uplift in the East African Rift: evidence for Late Pleistocene large magnitude earthquakes.

    Science.gov (United States)

    Hilbert-Wolf, Hannah Louise; Roberts, Eric M

    2015-01-01

    In lieu of comprehensive instrumental seismic monitoring, short historical records, and limited fault trench investigations for many seismically active areas, the sedimentary record provides important archives of seismicity in the form of preserved horizons of soft-sediment deformation features, termed seismites. Here we report on extensive seismites in the Late Quaternary-Recent (≤ ~ 28,000 years BP) alluvial and lacustrine strata of the Rukwa Rift Basin, a segment of the Western Branch of the East African Rift System. We document examples of the most highly deformed sediments in shallow, subsurface strata close to the regional capital of Mbeya, Tanzania. This includes a remarkable, clastic 'megablock complex' that preserves remobilized sediment below vertically displaced blocks of intact strata (megablocks), some in excess of 20 m-wide. Documentation of these seismites expands the database of seismogenic sedimentary structures, and attests to large magnitude, Late Pleistocene-Recent earthquakes along the Western Branch of the East African Rift System. Understanding how seismicity deforms near-surface sediments is critical for predicting and preparing for modern seismic hazards, especially along the East African Rift and other tectonically active, developing regions.

  9. Genetic evidence of successful establishment of the Nile perch (Lates spp. L. in East African lakes and implications for management

    Directory of Open Access Journals (Sweden)

    Matthew Tenywa Mwanja

    2012-12-01

    Full Text Available Nile perch establishment in novel ranges in East Africa is one of the most successful freshwater invasion stories in the recent history. Itbecame ecologically dominant and well established in several lakes in the Lake Victoria Region in a period of less than 5 decades. Geneticdiversity of both introduced and native populations were assessed and patterns compared in order to establish the genetic consequences oftheir introductions. Genetic variation was surveyed at both the mitochondrial control region (CR and at nine microsatellite loci. A total of 527 Nile perch fish were sampled from 5 East African lakes: native source populations were examined from lakes Albert and Turkana while introduced populations were sampled from lakes Kyoga, Nabugabo and Victoria. Both types of markers revealed higher average geneticdiversity for invasive species (HE = 0.70, h = 0.81 than for native source populations (HE = 0.66, h = 0.69. Both populations scoredrelatively higher than the average for freshwater fishes (HE = 0.62. Both native and introduced populations had 2 underlying geneticgroupings in similar proportions as revealed by the STRUCTURE program. The high genetic diversity was most probably a consequence ofhigher numbers of propagules than outlined by official records of introductions. Use of high number of individuals at stocking is probably the reason for apparently minimized ‘founder effects’ of Nile perch in the introduced ranges. The two underling populations revealed through genetic analysis may be representatives of the two subspecies of Nile perch previously reported in other studies. Implications to the management of this fishery in the East African region is that with the relatively high genetic diversity, the species could be sustainably exploited if it were effectively managed. In addition, further studies of the life histories and other attributes of the two genetic groupings of Nile perch in the region are recommended, as they may

  10. Primary domestication and early uses of the emblematic olive tree: palaeobotanical, historical and molecular evidence from the Middle East.

    Science.gov (United States)

    Kaniewski, David; Van Campo, Elise; Boiy, Tom; Terral, Jean-Frédéric; Khadari, Bouchaïb; Besnard, Guillaume

    2012-11-01

    Our knowledge of the origins of olive tree domestication in the Middle East and on the processes governing its extension and persistence in different vegetation types from prehistory through antiquity to modern times derives from diverse sources, spanning the biological sciences to the humanities. Nonetheless, it lacks a robust overview that may lead to floating interpretations. This is especially true in the Middle East, considered as the cradle of agriculture, and where the evolutionary history of this emblematic tree is intertwined with that of civilizations. Olive fruit, oil and wood have been, since Prehistoric times, characteristic products of the lands bordering the Mediterranean Sea. In the domestic economy of these countries, the olive tree gradually became a traditional tree crop since the first oil extraction, through the emergence of regional commerce that accompanied the rise and fall of early Near-Middle Eastern urbanism, until the development of modern trade, with an oil production estimated at circa 3000000 tons per year. The rising importance of the olive tree in human life has turned the tree into an endless source of fascination in the Aegean and Eastern Mediterranean, a symbol and a sacred tree, widely cited in the Bibles, the Koran, and in ancient literature. Here we argue that advances in radiocarbon chronology, palaeobotany, genetics, and archaeology-history have profoundly refined the history of olive trees in the Middle East. This review shows that the heartland of primary olive domestication must be enlarged to the Levant and not only focus on the Jordan Valley. The domestication of the olive tree is a long and ongoing process, linked to the early production of oil and the development of the olive trade. We also suggest that the olive tree became a particular icon, a sacred tree, during the Biblical period in the Levant. © 2012 The Author. Biological Reviews © 2012 Cambridge Philosophical Society.

  11. Building capacity for evidence generation, synthesis and implementation to improve the care of mothers and babies in South East Asia: methods and design of the SEA-ORCHID Project using a logical framework approach

    OpenAIRE

    Short Jacki; Henderson-Smart David J; Mohammad Hakimi; Ho Jacqueline J; Festin Mario R; Thinkhamrop Jadsada; Lumbiganon Pisake; Chamberlain Catherine; Turner Tari; McDonald Steve; Crowther Caroline A; Martis Ruth; Green Sally

    2010-01-01

    Abstract Background Rates of maternal and perinatal mortality remain high in developing countries despite the existence of effective interventions. Efforts to strengthen evidence-based approaches to improve health in these settings are partly hindered by restricted access to the best available evidence, limited training in evidence-based practice and concerns about the relevance of existing evidence. South East Asia - Optimising Reproductive and Child Health in Developing Countries (SEA-ORCHI...

  12. Lead ingots from a shipwreck off Poompuhar, Tamil Nadu, east coast of India: Evidence for overseas trade and their significance

    Digital Repository Service at National Institute of Oceanography (India)

    Tripati, S.; Parthiban, G.; Vora, K.H.; Sundaresh; Bandodkar, S.N.

    . Metal objects found on land or underwater are of great interest to archaeologists in search of knowledge of origin, use and metallurgical process of ancient times. In India, for the first time, in 1991 a large number of lead ingots have been noticed from... a wreck off Poompuhar, Tamil Nadu on the east coast of India. It is true that metals like gold, silver, copper, zinc and to some extent lead were traded in ancient times but in later periods, particu- larly, lead was the main metal carried by vessels...

  13. Evidence and modeling of 3D divertor footprint induced by lower hybrid waves on EAST with tungsten divertor operations

    Science.gov (United States)

    Feng, W.; Wang, L.; Rack, M.; Liang, Y.; Guo, H. Y.; Xu, G. S.; Xu, J. C.; Liu, J. B.; Sun, Y. W.; Jia, M. N.; Yang, Q. Q.; Zhang, B.; Zou, X. L.; Liu, H.; Zhang, T.; Ding, F.; Chen, J. B.; Duan, Y. M.; Zheng, X. W.; Dai, S. Y.; Deng, G. Z.; Chen, R.; Hu, G. H.; Yan, N.; Si, H.; Liu, S. C.; Xu, S.; Wang, M.; Li, M. H.; Ding, B. J.; Wingen, A.; Huang, J.; Gao, X.; Luo, G. N.; Gong, X. Z.; Garofalo, A. M.; Li, J.; Wan, B. N.; the EAST team

    2017-12-01

    Three dimensional (3D) divertor particle flux footprints induced by the lower hybrid wave (LHW) have been systematically investigated in the EAST superconducting tokamak during the recent experimental campaign. We find that the striated particle flux (SPF) peaks away from the strike point (SP) closely fit the pitch of the edge magnetic field line for different safety factors q 95, as predicted by a field line tracing code taking into account the helical current filaments (HCFs) in the scrape-off-layer (SOL). As LHW power increases, it requires the fuelling to be increased e.g. by super molecular beam injection (SMBI), to maintain a similar plasma density, which may be attributed to the pump-out effect due to LHW, and may thus be beneficial for EAST steady state operations. The 3D SPF structure is observed with a LHW power threshold (P LHW ~ 0.9 MW). The ratio of the particle fluxes between SPF and outer strike point (OSP), i.e. {{Γ }ion,SPF}/{{Γ }ion,OSP} , increases with the LHW power. Upon transition to divertor detachment, the particle flux at the main OSP decreases, as expected, however, the particle flux at SPF continues increasing, in contrast to the RMP-induced striations that vanish with increasing divertor density. In addition, we also find that the in–out asymmetry of the 3D particle flux footprint pattern exhibits a clear dependence on the toroidal field direction (B  ×    ∇   B  ↓  and B  ×    ∇   B↑). Experiments using neon impurity seeding show a promising capability in 3D particle and heat flux control on EAST. LHW-induced particle and heat flux striations are also present in the H-mode plasmas, reducing the peak heat flux and erosion at the main strike point, thus facilitating long-pulse operation with a new steady-state H-mode over 60 s being recently achieved in EAST.

  14. Paleo ice flow and subglacial meltwater dynamics in Pine Island Bay, West Antarctica

    Directory of Open Access Journals (Sweden)

    F. O. Nitsche

    2013-02-01

    Full Text Available Increasing evidence for an elaborate subglacial drainage network underneath modern Antarctic ice sheets suggests that basal meltwater has an important influence on ice stream flow. Swath bathymetry surveys from previously glaciated continental margins display morphological features indicative of subglacial meltwater flow in inner shelf areas of some paleo ice stream troughs. Over the last few years several expeditions to the eastern Amundsen Sea embayment (West Antarctica have investigated the paleo ice streams that extended from the Pine Island and Thwaites glaciers. A compilation of high-resolution swath bathymetry data from inner Pine Island Bay reveals details of a rough seabed topography including several deep channels that connect a series of basins. This complex basin and channel network is indicative of meltwater flow beneath the paleo-Pine Island and Thwaites ice streams, along with substantial subglacial water inflow from the east. This meltwater could have enhanced ice flow over the rough bedrock topography. Meltwater features diminish with the onset of linear features north of the basins. Similar features have previously been observed in several other areas, including the Dotson-Getz Trough (western Amundsen Sea embayment and Marguerite Bay (SW Antarctic Peninsula, suggesting that these features may be widespread around the Antarctic margin and that subglacial meltwater drainage played a major role in past ice-sheet dynamics.

  15. GIS portal site of Japanese Antarctica Research

    Directory of Open Access Journals (Sweden)

    Yoshifumi Nogi

    2010-11-01

    Full Text Available GIS (Geographic Information Systems based on digitized spatial informations have been employed in various fields recently. GIS portal site of Japanese Antarctica research has been built under the project of transdisciplinary research integration of Research Organization of Information and Systems to make good use of Antarctic map data for researchers and the public. The map data of Antarctica that the Geospatial Information Authority of Japan and the National Institute of Polar Research hold were digitized for use on the GIS portal site Web services. Fundamental spatial information on the Antarctic region was prepared, and GIS portal site of Japanese Antarctica research provides basic map operation services on the Web. GIS portal site of Japanese Antarctica research also serves data set of the map that are available for Google Earth and the other GIS application. Although the location errors of various kind of map data should be fixed, substantial use of GIS portal site of Japanese Antarctica research are expected.

  16. Benthic faunal composition along Princess Astrid Coast, East Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Sreepada, R.A.; Jayasree, V.; Parulekar, A.H.

    stream_size 5 stream_content_type text/plain stream_name DOD_Tech_Publ_1995_8_181.pdf.txt stream_source_info DOD_Tech_Publ_1995_8_181.pdf.txt Content-Encoding ISO-8859-1 Content-Type text/plain; charset=ISO-8859-1 ...

  17. Limnology of freshwater lakes of Schirmacher Oasis, East Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Ingole, B.S.; Parulekar, A.H.

    taxonomic groups with minimum and maximum faunal density of 43 and 823 individuals in 10 cm/2 respectively was recorded from covered and uncovered sediments. Faunal density showed a strong correlation with organic carbon content and the sediment texture...

  18. Morpho-Tectonic Evidence of Multi-Stage Uplift History of the Southeastern Ethiopian Plateau, the East African Rift System

    Science.gov (United States)

    Xue, L.; Abdelsalam, M. G.

    2016-12-01

    We used Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) to extract geomorphic proxies (normalized steepness, stream length gradient, shape factor, and valley height ratio) for the Southwestern Ethiopian Plateau. We also imaged the Moho beneath the plateau using two-dimensional power radially-average power spectral analysis of World Gravity Model (WGM 2012) satellite gravity data. Our aim is to examine the uplift history of the plateau that might be associated with the uprising of the Afar mantle plume and opening of the East African Rift System. This plateau, which is bounded by the Afar Depression in the north and the Main Ethiopian Rift in the east, exposes Cenozoic volcanic rocks at the top underlain by Mesozoic sedimentary rocks. Studies in the Northwestern Ethiopian Plateau resulted in two contrasting models for explaining the uplift history of the region. Thermogeochronology studies suggest a continuous and steady uplift rate since 30 Ma possibly driven by the ascending Afar mantle plume. While, the interpretation of incision of drainage systems in the plateau suggests three stage and accelerated uplift. Our work found two areas with high rate of tectonic uplift located around the Mendebo and the Ahmar mountains. These regions show two distinct phases of uplift of the Southeastern Ethiopian Plateau. Also, a chronological framework has been provided to the knickpoint migration and associated Quaternary basalt event by knickpoint celerity model.

  19. Friis Hills glacial history: an international collaboration to examine Miocene climate in Antarctica

    Science.gov (United States)

    Halberstadt, A. R. W.; Kowalewski, D. E.

    2016-12-01

    The Friis Hills, Antarctica (western McMurdo Dry Valleys) contain unique, well-preserved records of Miocene climate. These terrestrial deposits hold geomorphic clues for deciphering the glacial history in a region directly adjacent to the East Antarctic Ice Sheet. Stacked till sheets, interbedded with lake sediments and non-glacial deposits, reveal a complex history of ice flow and erosion throughout multiple glacial-interglacial cycles (Lewis and Ashworth, 2015). Fossiliferous beds containing Nothofagus, diatoms, algal cells, pollen, insects, and mosses provide past climatological constraints. The Friis Hills sustained multiple alpine glaciations as well as full ice-sheet development, recording glacial drainage reorganization and evidence of previous ice configurations that possibly overrode the Transantarctic Mountains (Lewis and Ashworth, 2015) exposing only scattered nunataks (i.e. a portion of Friis Hills). Lack of chronological control has previously hindered efforts to link the Friis Hills glacial history with regional context; a tephra deposit at the base of the glacial drifts currently provides a single age constraint within the drift deposits. To build upon previous studies, an international collaboration between the USAP, Antarctic New Zealand, and the Italian Antarctic community proposes to core a paleo-lake in the center of the Friis Hills in November 2016, thereby acquiring one of the oldest continuous sedimentological records within the McMurdo Dry Valleys. Here we report discoveries from this year's fieldwork, and reconstruct paleoenvironment at the periphery of the East Antarctic Ice Sheet for the mid-early Miocene, a critical time when marine isotopic records indicate dramatic ice fluctuations. Ash within the sediment core stratigraphy will provide a more robust chronology for the region, and will also suggest possible outcrop locations of corresponding ash deposits to pursue while in the field. We anticipate that the Friis Hills stratigraphy will

  20. Genetic evidence of an East Asian origin and paleolithic northward migration of Y-chromosome haplogroup N.

    Directory of Open Access Journals (Sweden)

    Hong Shi

    Full Text Available The Y-chromosome haplogroup N-M231 (Hg N is distributed widely in eastern and central Asia, Siberia, as well as in eastern and northern Europe. Previous studies suggested a counterclockwise prehistoric migration of Hg N from eastern Asia to eastern and northern Europe. However, the root of this Y chromosome lineage and its detailed dispersal pattern across eastern Asia are still unclear. We analyzed haplogroup profiles and phylogeographic patterns of 1,570 Hg N individuals from 20,826 males in 359 populations across Eurasia. We first genotyped 6,371 males from 169 populations in China and Cambodia, and generated data of 360 Hg N individuals, and then combined published data on 1,210 Hg N individuals from Japanese, Southeast Asian, Siberian, European and Central Asian populations. The results showed that the sub-haplogroups of Hg N have a distinct geographical distribution. The highest Y-STR diversity of the ancestral Hg N sub-haplogroups was observed in the southern part of mainland East Asia, and further phylogeographic analyses supports an origin of Hg N in southern China. Combined with previous data, we propose that the early northward dispersal of Hg N started from southern China about 21 thousand years ago (kya, expanding into northern China 12-18 kya, and reaching further north to Siberia about 12-14 kya before a population expansion and westward migration into Central Asia and eastern/northern Europe around 8.0-10.0 kya. This northward migration of Hg N likewise coincides with retreating ice sheets after the Last Glacial Maximum (22-18 kya in mainland East Asia.

  1. Evidence for a bi-partition of the Younger Dryas Stadial in East Asia associated with inversed climate characteristics compared to Europe

    Science.gov (United States)

    Schlolaut, Gordon; Brauer, Achim; Nakagawa, Takeshi; Lamb, Henry F.; Tyler, Jonathan J.; Staff, Richard A.; Marshall, Michael H.; Bronk Ramsey, Christopher; Bryant, Charlotte L.; Tarasov, Pavel E.

    2017-03-01

    The Younger Dryas Stadial (YDS) was an episode of northern hemispheric cooling which occurred within the Last Glacial Interglacial Transition (LGIT). A major driver for the YDS climate was a weakening of the Atlantic Meridional Overturning Circulation (AMOC). It has been inferred that the AMOC began to strengthen mid-YDS, producing a bipartite structure of the YDS in records from continental Europe. These records imply that the polar front and westerlies shifted northward, producing a warmer second phase of the YDS in Europe. Here we present multi-proxy data from the sediments of Lake Suigetsu (Japan), as evidence that a related bi-partition of the YDS also occurred in East Asia. Besides showing for the first time that the bi-partition was not limited to the North Atlantic/European region, the data also imply a climatic dipole between Europe and East Asia since the cold-warm characteristics are reversed at Lake Suigetsu. We suggest that changes in eastward moisture transport from the North Atlantic are the primary mechanism by which the teleconnection can be explained.

  2. Tracking Seed Fates of Tropical Tree Species: Evidence for Seed Caching in a Tropical Forest in North-East India

    Science.gov (United States)

    Sidhu, Swati; Datta, Aparajita

    2015-01-01

    Rodents affect the post-dispersal fate of seeds by acting either as on-site seed predators or as secondary dispersers when they scatter-hoard seeds. The tropical forests of north-east India harbour a high diversity of little-studied terrestrial murid and hystricid rodents. We examined the role played by these rodents in determining the seed fates of tropical evergreen tree species in a forest site in north-east India. We selected ten tree species (3 mammal-dispersed and 7 bird-dispersed) that varied in seed size and followed the fates of 10,777 tagged seeds. We used camera traps to determine the identity of rodent visitors, visitation rates and their seed-handling behavior. Seeds of all tree species were handled by at least one rodent taxon. Overall rates of seed removal (44.5%) were much higher than direct on-site seed predation (9.9%), but seed-handling behavior differed between the terrestrial rodent groups: two species of murid rodents removed and cached seeds, and two species of porcupines were on-site seed predators. In addition, a true cricket, Brachytrupes sp., cached seeds of three species underground. We found 309 caches formed by the rodents and the cricket; most were single-seeded (79%) and seeds were moved up to 19 m. Over 40% of seeds were re-cached from primary cache locations, while about 12% germinated in the primary caches. Seed removal rates varied widely amongst tree species, from 3% in Beilschmiedia assamica to 97% in Actinodaphne obovata. Seed predation was observed in nine species. Chisocheton cumingianus (57%) and Prunus ceylanica (25%) had moderate levels of seed predation while the remaining species had less than 10% seed predation. We hypothesized that seed traits that provide information on resource quantity would influence rodent choice of a seed, while traits that determine resource accessibility would influence whether seeds are removed or eaten. Removal rates significantly decreased (p seed size. Removal rates were significantly

  3. Lithospheric Structure of Antarctica and Implications for Geological and Cryospheric Evolution

    Science.gov (United States)

    Wiens, Douglas; Heeszel, David; Sun, Xinlei; Lloyd, Andrew; Nyblade, Andrew; Anandakrishnan, Sridhar; Aster, Richard; Chaput, Julien; Huerta, Audrey; Hansen, Samantha; Wilson, Terry

    2013-04-01

    Recent broadband seismic deployments, including the AGAP/GAMSEIS array of 24 broadband seismographs over the Gamburtsev Subglacial Mountains (GSM) in East Antarctica and the POLENET/ANET deployment of 33 seismographs across much of West Antarctica, reveal the detailed crust and upper mantle structure of Antarctica for the first time. The seismographs operate year-around even in the coldest parts of Antarctica, due to novel insulated boxes, power systems, and modified instrumentation developed in collaboration with the IRIS PASSCAL Instrument Center. We analyze the data using several different techniques to develop high-resolution models of Antarctic seismic structure. We use Rayleigh wave phase velocities at periods of 20-180 s determined using a modified two-plane wave decomposition of teleseismic Rayleigh waves to invert for the three dimensional shear velocity structure. In addition, Rayleigh wave group and phase velocities obtained by ambient seismic noise correlation methods provide constraints at shorter periods and shallower depths. Receiver functions provide precise estimates of crustal structure beneath the stations, and P and S wave tomography provides models of upper mantle structure down to ~ 500 km depth along transects of greater seismic station density. The new seismic results show that the high elevations of the GSM are supported by thick crust (~ 55 km), and are underlain by thick Precambrian continental lithosphere that initially formed during Archean to mid-Proterozoic times. The absence of lithospheric thermal anomalies suggests that the mountains were formed by a compressional orogeny during the Paleozoic, thus providing a locus for ice sheet nucleation throughout a long period of geological time. Within West Antarctica, the crust and lithosphere are extremely thin near the Transantarctic Mountain Front and topographic lows such as the Bentley Trench and Byrd Basin, which represent currently inactive Cenozoic rift systems. Slow seismic

  4. Mineralogical evidence of reduced East Asian summer monsoon rainfall on the Chinese loess plateau during the early Pleistocene interglacials

    Science.gov (United States)

    Meng, Xianqiang; Liu, Lianwen; Wang, Xingchen T.; Balsam, William; Chen, Jun; Ji, Junfeng

    2018-03-01

    The East Asian summer monsoon (EASM) is an important component of the global climate system. A better understanding of EASM rainfall variability in the past can help constrain climate models and better predict the response of EASM to ongoing global warming. The warm early Pleistocene, a potential analog of future climate, is an important period to study EASM dynamics. However, existing monsoon proxies for reconstruction of EASM rainfall during the early Pleistocene fail to disentangle monsoon rainfall changes from temperature variations, complicating the comparison of these monsoon records with climate models. Here, we present three 2.6 million-year-long EASM rainfall records from the Chinese Loess Plateau (CLP) based on carbonate dissolution, a novel proxy for rainfall intensity. These records show that the interglacial rainfall on the CLP was lower during the early Pleistocene and then gradually increased with global cooling during the middle and late Pleistocene. These results are contrary to previous suggestions that a warmer climate leads to higher monsoon rainfall on tectonic timescales. We propose that the lower interglacial EASM rainfall during the early Pleistocene was caused by reduced sea surface temperature gradients across the equatorial Pacific, providing a testable hypothesis for climate models.

  5. The effect of hydrothermal circulation on subsidence on ocean basins : evidence from the South East Indian Ocean

    Science.gov (United States)

    Géli, L.; Francheteau, J.

    2003-04-01

    While it is generally accepted that off-axis hydrothermal circulation is responsible for the majority of the observed oceanic heat flow anomalies (e. g. for the "missing" conductive heatflow through oceanic lithosphere), the effect of water circulation on the subsidence of ocean basins at the scale of tens of millions years has not been thoroughly recognized. We present a very simple model (based on the half-space model) showing that, that in some particular circumstances, hydrothermal circulation may be held responsible for unexplained subsidence rate anomalies at the scale of ocean basins. An example is given for the poorly sedimented South-East Indian Ridge flanks of age Ma1/2 ) can be more readily explained by the observed sedimentation pattern and the subsequent pattern in hydrothermal circulation than by ad hoc variations in the mantle thermal parameters. Our model assumes that in absence of sedimentation, hydrothermal circulation convectively maintains low temperatures within the upper crust at ages as old as 20 to 30 Ma. Agreement with re-assesed subsidence estimates supports the model hypothesis.

  6. Evidence for geographic substructuring of mtDNA variation in the East European Hermit beetle (Osmoderma barnabita

    Directory of Open Access Journals (Sweden)

    Matti Landvik

    2017-07-01

    Full Text Available The genus Osmoderma is a flagship taxon of invertebrate conservation in Europe and encompasses a complex of four accepted species. While species limits amongst Osmoderma have been intensively studied, patterns of intraspecific variation are poorly known. In this paper, the authors focus on clarifying the phylogeographic structure of the East European Osmoderma barnabita using samples from Croatia to Finland. Samples of hind legs were collected from populations in Latvia and Finland (n=186 and combined with previously-published sequences from GenBank and museum specimens (n=10. In a partial sequence of the mitochondrial COI gene (759 bp, 26 closely related haplotypes were found. Beetle samples from different parts of Europe were distinct and showed no overlap in haplotype composition. The solitary population of Finland proved to be monomorphic and all 97 individuals sampled here belonged to a single haplotype unique to this region. The results suggest the Northern parts of Eastern Europe to be dominated by a single COI haplotype to which most of the other haplotypes are linked by one or two mutations. The pattern seems to reflect a founder effect or a strong bottleneck event. While O. barnabita is widely distributed over Eastern Europe, current patterns of mitochondrial genetic diversity appear influenced by population history and little homogenisation by ongoing gene flow. From a conservation perspective, the patterns suggest that regional populations might need to be managed as subunits and that the population of Finland may be affected by low genetic diversity.

  7. Change and Variability in East Antarctic Sea Ice Seasonality, 1979/80?2009/10

    OpenAIRE

    Massom, Robert; Reid, Philip; Stammerjohn, Sharon; Raymond, Ben; Fraser, Alexander; Ushio, Shuki

    2013-01-01

    Recent analyses have shown that significant changes have occurred in patterns of sea ice seasonality in West Antarctica since 1979, with wide-ranging climatic, biological and biogeochemical consequences. Here, we provide the first detailed report on long-term change and variability in annual timings of sea ice advance, retreat and resultant ice season duration in East Antarctica. These were calculated from satellite-derived ice concentration data for the period 1979/80 to 2009/10. The pattern...

  8. Iceberg Firn Temperatures, Antarctica, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — Since November of 2005, 12 thermistors were planted in the upper 2.5 meters of the firn on iceberg C16, Antarctica. Temperature data are collected every 20 minutes...

  9. Biosecurity on thin ice in Antarctica

    Czech Academy of Sciences Publication Activity Database

    Hulme, P. E.; Pyšek, Petr; Winter, M.

    2012-01-01

    Roč. 336, č. 6085 (2012), s. 1101-1102 ISSN 0036-8075 Institutional support: RVO:67985939 Keywords : biological invasions * Antarctica * management Subject RIV: EF - Botanics Impact factor: 31.027, year: 2012

  10. Wind profiler installed in Antarctica

    Science.gov (United States)

    Balsley, B. B.; Carey, J.; Woodman, R. F.; Sarango, M.; Urbina, J.; Rodriguez, R.; Ragaini, E.

    A VHF (50 MHz) wind profiler was installed in Antarctica at the Peruvian Base “Machu Picchu” on King George Island from January 21 to 26. The wind profiler will provide a first look at atmospheric dynamics over the region.The profiler—the first of its kind in Antarctica—is a National Science Foundationsponsored cooperative project of the University of Colorado, the Geophysical Institute of Peru, the University of Piura (Peru), and the Peruvian Navy. This venture was also greatly facilitated by Peru's Comision Nacional de Asuntos Antartidos and Consejo Nacional de Ciencias y Tecnologia, with additional logis tics support provided by the Argentinean Navy and the Uruguayan Air Force.

  11. Observational evidences on the modulation of the South American Low Level Jet east of the Andes according the ENSO variability

    Directory of Open Access Journals (Sweden)

    G. A. M. Silva

    2009-02-01

    Full Text Available The differences on the phase and wavelength of the quasi-stationary waves over the South America generated by El Niño (EN and La Niña (LN events seem to affect the daily evolution of the South American Low Level Jet east of the Andes (SALLJ. For the austral summer period of 1977–2004 the SALLJ episodes detected according to Bonner criterion 1 show normal to above-normal frequency in EN years, and in LN years the episodes show normal to below-normal frequency.

    During EN and LN years the SALLJ episodes were associated with positive rainfall anomalies over the La Plata Basin, but more intense during LN years. During EN years the increase in the SALLJ cases were associated to intensification of the Subtropical Jet (SJ around 30° S and positive Sea Level Pressure (SLP anomalies over the western equatorial Atlantic and tropical South America, particularly over central Brazil. This favored the intensification of the northeasterly trade winds over the northern continent and it channeled by the Andes mountain to the La Plata Basin region where negative SLP are found. The SALLJ cases identified during the LN events were weaker and less frequent when compared to those for EN years. In this case the SJ was weaker than in EN years and the negative SLP anomalies over the tropical continent contributed to the inversion of the northeasterly trade winds. Also a southerly flow anomaly was generated by the geostrophic balance due to the anomalous blocking over southeast Pacific and the intense cyclonic transient over the southern tip of South America. As result the warm tropical air brought by the SALLJ encounters the cold extratropical air from the southerly winds over the La Plata basin. This configuration can increase the conditional instability over the La Plata basin and may explain the more intense positive rainfall anomalies in SALLJ cases during LN years than in EN years.

  12. Geophysical evidence and inferred triggering factors of submarine landslides on the western continental margin of the Ulleung Basin, East Sea

    Science.gov (United States)

    Cukur, Deniz; Kim, Seong-Pil; Kong, Gee-Soo; Bahk, Jang-Jun; Horozal, Senay; Um, In-Kwon; Lee, Gwang-Soo; Chang, Tae-Soo; Ha, Hun-Jun; Völker, David; Kim, Jung-Ki

    2016-12-01

    Submarine landslides form very complex depositional and erosional features on the seafloor, and their dynamics and triggering processes are yet to be understood completely. Numerous studies are being undertaken both because of the scientific significance but also for their potential harm to seafloor infrastructure and coastal areas. This study investigates the styles and causes of landsliding along the western margin of the Ulleung Basin in the East Sea, based on multiple sparker, subbottom profiler, multibeam echosounder and sediment core datasets collected in 2015. The bathymetric analyses indicate that the southern slope of the Ulleung Basin has experienced at least seven submarine failures. These failures left clear arcuate-shaped scarps that initiated at water depths of 600 m. The observed headwall scarps have heights that exceed 60 m and appear to be the result of retrogressive-type failures. Seismic reflection data clearly image the basal sliding surface that is characterized by a prominent high-amplitude reflector. Chaotic-to-transparent seismic facies occur immediately downslope of the headwall scarps; these represent 20 m thick landslide deposits. Gravity cores taken from areas adjacent to the scars suggest that these slides are older than ca. 97 ka. Interpretation of the present data shows that faults appear to cut recent sediments upslope of scarps, and that the slope may still be in an active phase of failure. Seismic data also image various overpressurized gases and/or gas fluids, as evidenced by the occurrence of pockmarks and seismic chimneys in upslope or adjacent areas of the scarps. Hence, earthquakes associated with tectonic activity and development of fluid overpressure may have acted as the main conditioning factor for destabilizing the slope sediments. Geotechnical stability analyses indicate that the sampled slope sediments are exceptionally stable under present-day conditions, even under seismic loading. This finding points to additional

  13. Tors, Eustatic Shorelines, and Mammoths: Evidence Against Ice Sheets on Wrangel Island, East Siberian/Chukchi Seas

    Science.gov (United States)

    Gualtieri, L.; Vartanyan, S.; Brigham-Grette, J.; Anderson, P.

    2001-12-01

    Assumed glacial flutings on the Chukchi Rise (Polyak et al., 2001) have reinvigorated hypotheses concerning the past presence of the same type of ice sheet or ice shelf on the Chukchi and/or East Siberian Sea shelf. Fieldwork on wrangle Island has been aimed at determining the glacial and sea level history of this geographically strategic island to address these various hypotheses. Cosmogenic isotope ages (Be and Al) on bedrock are all older that 35 ka , at a minimum, the rates of pervasive pariglacial processes. Tors, commonly forming columns 10 m high, are ubiquitous throughout the mountains of Wrangel Island. Eustatic shorelines (and not glacioisostatic shorelines) across the northern tundra plain marked by remnant marine sediments and ancient barrier beaches up to 40 m above seal level are all older than the range of radiocarbon dating and yield amino acid age estimates (D/L Aspartic as well as aIle/Ile) in excess of 400-500 ka, similar to sediments found in the Alaskan North Slope. Radiocarbon dates on mammoth borres, teeth and tusks and other animals (rhinos, bison) yield ages that range continuously through time from >38 ka to 3700 years ago indicating the local presence of large mammals during the Last Glacial Maximum (LGM) and most of the Holocene. These data preclude the presence of an ice sheet during the LGM and probably over the past half million years. Glacial ice extent on the island during the LGM was limited to a few small north facing cirque glaciers. The flutings on the Chukchi Rise could not have been formed by an ice sheet over or near Wrangel Island in at least the last four or five major glacial/interglacial cycles.

  14. Observational evidences on the modulation of the South American Low Level Jet east of the Andes according the ENSO variability

    Directory of Open Access Journals (Sweden)

    G. A. M. Silva

    2009-02-01

    Full Text Available The differences on the phase and wavelength of the quasi-stationary waves over the South America generated by El Niño (EN and La Niña (LN events seem to affect the daily evolution of the South American Low Level Jet east of the Andes (SALLJ. For the austral summer period of 1977–2004 the SALLJ episodes detected according to Bonner criterion 1 show normal to above-normal frequency in EN years, and in LN years the episodes show normal to below-normal frequency. During EN and LN years the SALLJ episodes were associated with positive rainfall anomalies over the La Plata Basin, but more intense during LN years. During EN years the increase in the SALLJ cases were associated to intensification of the Subtropical Jet (SJ around 30° S and positive Sea Level Pressure (SLP anomalies over the western equatorial Atlantic and tropical South America, particularly over central Brazil. This favored the intensification of the northeasterly trade winds over the northern continent and it channeled by the Andes mountain to the La Plata Basin region where negative SLP are found. The SALLJ cases identified during the LN events were weaker and less frequent when compared to those for EN years. In this case the SJ was weaker than in EN years and the negative SLP anomalies over the tropical continent contributed to the inversion of the northeasterly trade winds. Also a southerly flow anomaly was generated by the geostrophic balance due to the anomalous blocking over southeast Pacific and the intense cyclonic transient over the southern tip of South America. As result the warm tropical air brought by the SALLJ encounters the cold extratropical air from the southerly winds over the La Plata basin. This configuration can increase the conditional instability over the La Plata basin and may explain the more intense positive rainfall anomalies in SALLJ cases during LN years than in EN years.

  15. Molecular evidence for nitrite-dependent anaerobic methane-oxidising bacteria in the Jiaojiang Estuary of the East Sea (China).

    Science.gov (United States)

    Li-Dong, Shen; Qun, Zhu; Shuai, Liu; Ping, Du; Jiang-Ning, Zeng; Dong-Qing, Cheng; Xiang-Yang, Xu; Ping, Zheng; Bao-Lan, Hu

    2014-06-01

    Nitrite-dependent anaerobic methane oxidation (N-DAMO) is a recently discovered process linking the global carbon and nitrogen cycles. This process was reported to be mediated by "Candidatus Methylomirabilis oxyfera". To date, M. oxyfera-like bacteria have been detected in a limited number of freshwater habitats, but whether these bacteria occur in estuarine habitats is currently unknown. In this study, the distribution, diversity and abundance of M. oxyfera-like bacteria were studied in the sediment of the Jiaojiang Estuary of the East Sea (China). Both the 16S ribosomal RNA (rRNA) and pmoA genes confirmed the occurrence of M. oxyfera-like bacteria in the examined estuary. The recovered 16S rRNA gene sequences showed 91.5-97.2 % identity to the 16S rRNA gene of M. oxyfera, and the recovered pmoA gene sequences showed 85.1-95.4 % identity to the pmoA gene of M. oxyfera. Quantitative PCR further confirmed the occurrence of M. oxyfera-like bacteria in this estuary, with the abundance varying from 5.80 ± 0.28 × 10(4) to 8.35 ± 0.52 × 10(7) copies g (dry weight)(-1). Correlation analysis indicated that the sediment organic content was the most important factor affecting the distribution of M. oxyfera-like bacterial communities in the examined sediments among the environmental factors investigated. This study demonstrated for the first time the existence of M. oxyfera-like bacteria in an estuarine environment and showed the correlations between the distribution of these bacteria and the estuarine environmental conditions.

  16. Geoethical approach to mineral activities in Antarctica

    Science.gov (United States)

    Talalay, Pavel

    2013-04-01

    Antarctica is the outermost from civilization space continent. From 14.0 million km2 of surface area about 98% of Antarctica is covered by ice that averages at least 1.6 km in thickness. Geologically, the continent is the least explored in the world, and it is almost absolutely unknown what mineral resources Antarctica has as they are buried in rock that is covered by a thick ice sheet. It is thought to have large and valuable mineral deposits under the ice. This is because of what has been found in samples taken from the small areas of rock that are exposed, and also from what has been found in South Africa and South America. Up until 180 million years ago, Antarctica was a part of the Gondwanaland super continent, attached to South America, the Southern part of Africa, India and Australia, these continents then drifted apart until they reached their current positions. This leads to a possibility that Antarctica may also share some of the mineral wealth of these continents. Right now on the ice-free areas of Antarctica iron ore, chromium, copper, gold, nickel, platinum, coal and hydrocarbons have been found. The Protocol on Environmental Protection to the Antarctic Treaty, also known as the Madrid Protocol, was signed in 1991 by the signatories to the Antarctic Treaty and became law in January 1998. The Protocol provides for comprehensive protection of the Antarctic environment and associated ecosystems and includes a ban on all commercial mining for at least fifty years (this is up for review in 2041). Current climate change and melting ice in Polar Regions is opening up new opportunities to exploit mineral and oil resources. Even Antarctica's weather, ice and distance from any industrialized areas mean that mineral extraction would be extremely expensive and also extremely dangerous, the depletion of mineral recourses on the Earth can reverse banning of mining in Antarctica in future. There is no question that any resource exploitation in Antarctica will cause

  17. Limnology of Priyadarshani Lake, Schirmacher Oasis, Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Ingole, B.S.; Parulekar, A.H.

    -17(1990). Printed in Great Britain Limnology of Priyadarshani Lake, Schirmacher Oasis, Antarctica B. S. Ingole and A. H. Parulekar National Institute of Oceanography, Dona Paula, Goa 40300, India Received December 1988 13 ABS1RACT Priyadarshani, an oligotrophic lake... in Schinnacher Oasis (Antarctica), was surveyed during the austral summers of 1984-85 and 1986-87 in limnological and benthic studies. Benthic microfaWla included seven taxonomic groups, dominated numerically by protozoa, rotifera, nematoda, turbellaria...

  18. Heavy metals in some parts of Antarctica and the southern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Kureishy, T.W.; Sengupta, R.; Mesquita, A.; Sanzgiri, S.

    11/November 1993 Marine Polhaion Bulletin, Volume 26, No. I 1, pp. 651-652, 1993. Printed in Great Britain, 0025-326X/93 $6.00+0.00 © 1993 Pergamon Press Ltd Heavy Metals in Some Parts of Antarctica and the Southern Indian Ocean TARIQ W...(}ha, Qatar Though remote in its geographical location Antarctica is known to be indirectly affected by industrial and agricultural activities on other continents. This is evident in the concentrations of synthetic chemicals such as the organochlorine...

  19. Proteocephalid tapeworms (Cestoda: Onchoproteocephalidea) of loaches (Cobitoidea): Evidence for monophyly and high endemism of parasites in the Far East.

    Science.gov (United States)

    Scholz, Tomáš; de Chambrier, Alain; Shimazu, Takeshi; Ermolenko, Alexey; Waeschenbach, Andrea

    2017-02-01

    The parasite fauna of loaches (Cypriniformes: Cobitoidea), a group of small bottom-dwelling freshwater fishes with a mostly Eurasian distribution, remains a largely unknown quantity. Here we revise the taxonomy of tapeworms of the genus Proteocephalus Weinland, 1858 (Cestoda: Proteocephalidae) that had been found in loaches from the Palaearctic Region (Central Europe, Japan and Russia [Primorsky Region]). Molecular phylogenetic analysis based on two nuclear (ssr- and lsrDNA) and two mitochondrial genes (cox1 and rrnL) revealed a monophyletic group consisting of four valid species nesting within the Proteocephalus-aggregate: (i) Proteocephalus sagittus (Grimm, 1872) from Barbatula barbatula (Europe, Russia and Tajikistan), (ii) Proteocephalus demshini n. sp. from Barbatula toni (Russian Far East - Primorsky Region), (iii) Proteocephalus midoriensis Shimazu, 1990 from Lefua echigonia (Japan) and L. costata (Russia) (new host and geographical record), and (iv) Proteocephalus misgurni n. sp. from Misgurnus anguillicaudatus (Russia; Primorsky Region). Proteocephalus sagittus and P. demshini, and P. midoriensis and P. misgurni were recovered as sister taxa, respectively. Proteocephalus sagittus and P. demshini are characterized by having proglottids that are wider than long, an elongate to pyriform cirrus-sac and the vitelline follicles that form wide lateral bands. Proteocephalus midoriensis and P. misgurni are characterized by having proglottids that are more elongate and an ovoid to almost spherical cirrus-sac and the vitelline follicles forming narrow lateral bands. Proteocephalus demshini differs from P. sagittus in the posterolateral extent of the vitelline follicles, whereas P. misgurni can be distinguished from P. midoriensis mainly by the relative size of the ovary, posterior extent of the vitelline follicles and width of the scolex. Unlike most species of the Proteocephalus-aggregate that possess an apical sucker, all species from loaches are devoid of any

  20. The health loss from ischemic stroke and intracerebral hemorrhage: evidence from the North East Melbourne Stroke Incidence Study (NEMESIS

    Directory of Open Access Journals (Sweden)

    Dewey Helen M

    2010-05-01

    Full Text Available Abstract Background People suffering different types of stroke have differing demographic characteristics and survival. However, current estimates of disease burden are based on the same underlying assumptions irrespective of stroke type. We hypothesized that average Quality Adjusted Life Years (QALYs lost from stroke would be different for ischemic stroke and intracerebral hemorrhage (ICH. Methods We used 1 and 5-year data collected from patients with first-ever stroke participating in the North East Melbourne Stroke Incidence Study (NEMESIS. We calculated case fatality rates, health-adjusted life expectancy, and quality-of-life (QoL weights specific to each age and gender category. Lifetime 'health loss' for first-ever ischemic stroke and ICH surviving 28-days for the 2004 Australian population cohort was then estimated. Multivariable uncertainty analyses and sensitivity analyses (SA were used to assess the impact of varying input parameters e.g. case fatality and QoL weights. Results Paired QoL data at 1 and 5 years were available for 237 NEMESIS participants. Extrapolating NEMESIS rates, 31,539 first-ever strokes were expected for Australia in 2004. Average discounted (3% QALYs lost per first-ever stroke were estimated to be 5.09 (SD 0.20; SA 5.49 for ischemic stroke (n = 27,660 and 6.17 (SD 0.26; SA 6.45 for ICH (n = 4,291; p Discussion People with ICH incurred greater loss of health over a lifetime than people with ischemic stroke. This is explained by greater stroke related case fatality at a younger age, but longer life expectancy with disability after the first 12 months for people with ICH. Thus, studies of disease burden in stroke should account for these differences between subtype and gender. Otherwise, in countries where ICH is more common, health loss for stroke may be underestimated. Similar to other studies of this type, the generalisability of the results may be limited. Sensitivity and uncertainty analyses were used to provide

  1. The health loss from ischemic stroke and intracerebral hemorrhage: evidence from the North East Melbourne Stroke Incidence Study (NEMESIS).

    Science.gov (United States)

    Cadilhac, Dominique A; Dewey, Helen M; Vos, Theo; Carter, Rob; Thrift, Amanda G

    2010-05-14

    People suffering different types of stroke have differing demographic characteristics and survival. However, current estimates of disease burden are based on the same underlying assumptions irrespective of stroke type. We hypothesized that average Quality Adjusted Life Years (QALYs) lost from stroke would be different for ischemic stroke and intracerebral hemorrhage (ICH). We used 1 and 5-year data collected from patients with first-ever stroke participating in the North East Melbourne Stroke Incidence Study (NEMESIS). We calculated case fatality rates, health-adjusted life expectancy, and quality-of-life (QoL) weights specific to each age and gender category. Lifetime 'health loss' for first-ever ischemic stroke and ICH surviving 28-days for the 2004 Australian population cohort was then estimated. Multivariable uncertainty analyses and sensitivity analyses (SA) were used to assess the impact of varying input parameters e.g. case fatality and QoL weights. Paired QoL data at 1 and 5 years were available for 237 NEMESIS participants. Extrapolating NEMESIS rates, 31,539 first-ever strokes were expected for Australia in 2004. Average discounted (3%) QALYs lost per first-ever stroke were estimated to be 5.09 (SD 0.20; SA 5.49) for ischemic stroke (n = 27,660) and 6.17 (SD 0.26; SA 6.45) for ICH (n = 4,291; p < 0.001). QALYs lost also differed according to gender for both subtypes (ischemic stroke: males 4.69 SD 0.38, females 5.51 SD 0.46; ICH: males 5.82 SD 0.67, females 6.50 SD 0.40). People with ICH incurred greater loss of health over a lifetime than people with ischemic stroke. This is explained by greater stroke related case fatality at a younger age, but longer life expectancy with disability after the first 12 months for people with ICH. Thus, studies of disease burden in stroke should account for these differences between subtype and gender. Otherwise, in countries where ICH is more common, health loss for stroke may be underestimated. Similar to other studies

  2. Improving capacity for evidence-based practice in South East Asia: evaluating the role of research fellowships in the SEA-ORCHID Project

    Directory of Open Access Journals (Sweden)

    Martis Ruth

    2010-05-01

    Full Text Available Abstract Background Fellowships are a component of many professional education programs. They provide opportunities to develop skills and competencies in an environment where time is protected and resources and technical support are more readily available. The SEA-ORCHID fellowships program aimed to increase capacity for evidence-based practice and research synthesis, and to encourage fellows to become leaders in these areas. Methods Fellows included doctors, nurses, midwives and librarians working in the maternal and neonatal areas of nine hospitals in South East Asia. Fellowships were undertaken in Australia and involved specific outputs related to evidence-based practice or research synthesis. Training and support was tailored according to the type of output and the fellow's experience and expertise. We evaluated the fellowships program quantitatively and qualitatively through written evaluations, interviews and follow-up of fellowship activities. Results During 2006-07, 23 fellows from Thailand, Indonesia, Malaysia and the Philippines undertook short-term fellowships (median four weeks in Australia. The main outputs were drafts of Cochrane systematic reviews, clinical practice guidelines and protocols for randomised trials, and training materials to support evidence-based practice. Protocols for Cochrane systematic reviews were more likely to be completed than other outcomes. The fellows identified several components that were critical to the program's overall success; these included protected time, tailored training, and access to technical expertise and resources. On returning home, fellows identified a lack of time and limited access to the internet and evidence-based resources as barriers to completing their outputs. The support of colleagues and senior staff was noted as an important enabler of progress, and research collaborators from other institutions and countries were also important sources of support. Conclusions The SEA

  3. Dietary factors and type 2 diabetes in the Middle East: what is the evidence for an association?--a systematic review.

    Science.gov (United States)

    Al-Khudairy, Lena; Stranges, Saverio; Kumar, Sudhesh; Al-Daghri, Nasser; Rees, Karen

    2013-09-26

    This review aims to search and summarise the available evidence on the association between dietary factors and type 2 diabetes mellitus (T2DM) in Middle Eastern populations, where diabetes prevalence is among the highest in the world. Electronic databases were searched; authors, libraries, and research centres in the Middle East were contacted for further studies and unpublished literature. Included studies assessed potential dietary factors for T2DM in Middle Eastern adults. Two reviewers assessed studies independently. Extensive searching yielded 17 studies which met the inclusion criteria for this review. The findings showed that whole-grain intake reduces the risk of T2DM, and potato consumption was positively correlated with T2DM. Vegetables and vegetable oil may play a protective role against T2DM. Dietary patterns that are associated with diabetes were identified, such as Fast Food and Refined Grains patterns. Two studies demonstrated that lifestyle interventions decreased the risk of T2DM. In summary, the identified studies support an association between some dietary factors and T2DM; however, many of the included studies were of poor methodological quality so the findings should be interpreted with caution. The review draws attention to major gaps in current evidence and the need for well-designed studies in this area.

  4. Dietary Factors and Type 2 Diabetes in the Middle East: What Is the Evidence for an Association?––A Systematic Review

    Directory of Open Access Journals (Sweden)

    Nasser Al-Daghri

    2013-09-01

    Full Text Available This review aims to search and summarise the available evidence on the association between dietary factors and type 2 diabetes mellitus (T2DM in Middle Eastern populations, where diabetes prevalence is among the highest in the world. Electronic databases were searched; authors, libraries, and research centres in the Middle East were contacted for further studies and unpublished literature. Included studies assessed potential dietary factors for T2DM in Middle Eastern adults. Two reviewers assessed studies independently. Extensive searching yielded 17 studies which met the inclusion criteria for this review. The findings showed that whole-grain intake reduces the risk of T2DM, and potato consumption was positively correlated with T2DM. Vegetables and vegetable oil may play a protective role against T2DM. Dietary patterns that are associated with diabetes were identified, such as Fast Food and Refined Grains patterns. Two studies demonstrated that lifestyle interventions decreased the risk of T2DM. In summary, the identified studies support an association between some dietary factors and T2DM; however, many of the included studies were of poor methodological quality so the findings should be interpreted with caution. The review draws attention to major gaps in current evidence and the need for well-designed studies in this area.

  5. Dietary Factors and Type 2 Diabetes in the Middle East: What Is the Evidence for an Association?––A Systematic Review

    Science.gov (United States)

    Al-Khudairy, Lena; Stranges, Saverio; Kumar, Sudhesh; Al-Daghri, Nasser; Rees, Karen

    2013-01-01

    This review aims to search and summarise the available evidence on the association between dietary factors and type 2 diabetes mellitus (T2DM) in Middle Eastern populations, where diabetes prevalence is among the highest in the world. Electronic databases were searched; authors, libraries, and research centres in the Middle East were contacted for further studies and unpublished literature. Included studies assessed potential dietary factors for T2DM in Middle Eastern adults. Two reviewers assessed studies independently. Extensive searching yielded 17 studies which met the inclusion criteria for this review. The findings showed that whole-grain intake reduces the risk of T2DM, and potato consumption was positively correlated with T2DM. Vegetables and vegetable oil may play a protective role against T2DM. Dietary patterns that are associated with diabetes were identified, such as Fast Food and Refined Grains patterns. Two studies demonstrated that lifestyle interventions decreased the risk of T2DM. In summary, the identified studies support an association between some dietary factors and T2DM; however, many of the included studies were of poor methodological quality so the findings should be interpreted with caution. The review draws attention to major gaps in current evidence and the need for well-designed studies in this area. PMID:24077241

  6. Trade and foreign direct investment: Evidence from South East European countries and new European Union member states

    Directory of Open Access Journals (Sweden)

    Bardhyl Dauti

    2016-06-01

    Full Text Available The goal of this research is to provide an empirical assessment of the complementarity or substituting relationship between Trade and FDI in a link to country characteristics, using bilateral level data between FDI and trade for the period 1994 – 2010. In the research, an augmented gravity model has been used to test the relationship between Trade (both export and import, FDI stock and country characteristics between OECD-20 countries and SEE-5 and EU-NMS-10 countries. The empirical model considers how the relationship between FDI and Trade determine whether type of FDI into SEE-5 and EU-NMS-10 from core OECD-20 countries, is vertical or horizontal. With regard to the relationship between exports and FDI, the findings of the research showed mixed evidence, thus supporting vertical FDI for EU-NMS-10 countries, and horizontal FDI for SEE-5 countries. On the other hand, based on the relationship between imports and FDI, the results of the research supported vertical FDI for both EU-NMS-10 and SEE-5 group of countries. The basic conclusion is that the research provides an empirical evidence on the mixed nature of FDI into the host SEE-5 and EU-NMS-10 countries, supporting both complementary and substituting relationship between trade and FDI in the host countries.

  7. Joint seismic and geodynamic evidence for a long-lived, stable mantle upwelling under the East Pacific Rise

    Science.gov (United States)

    Forte, A. M.; Glisovic, P.; Rowley, D. B.; Simmons, N. A.; Grand, S. P.

    2013-12-01

    Global seismic tomography has consistently imaged large-scale structures in the lower mantle under the Pacific Ocean and under Africa that are characterised by strongly reduced seismic shear velocities. These so-called "low shear-velocity provinces" (LVSP) have been variously interpreted as hot, stagnant thermochemical "piles" that are compositionally dense, or as deeply rooted expressions of positively buoyant, active upwellings. To distinguish which of these two end-member models is relevant to the actual dynamics in the deep mantle requires robust constraints on the density structure of these LVSP. Recent global tomography models reveal what appear to be three distinct 'lobes' of the Pacific LVSP: one located in the Western-Pacific mantle under the Caroline Islands, another in the South-Central-Pacific mantle under French Polynesia, and another below the East Pacific Rise (EPR), centred under Easter Island. To understand the dynamics and time-dependent evolution of these structures we employ recent tomography models derived from the joint inversion of global seismic and geodynamic data sets, which also include constraints from mineral physics (Simmons et al., GJI 2009, JGR 2010). A critically important feature of these joint tomography models is the inclusion of a laterally variable scaling between density and seismic shear velocity, thereby accounting for the spatially localized effect of compositional heterogeneity in the lower mantle. These lower-mantle compositional contributions to density are directly constrained by long-wavelength gravity anomaly data and the excess ellipticity of the CMB. We show that it is not possible to properly account for this compositional heterogeneity using a constant, or simple depth-dependent density-velocity scaling. We have carried out very-long-time mantle convection simulations employing as a starting condition the joint seismic-geodynamic inferences of mantle density structure (Glisovic et al., GJI 2012). We demonstrate

  8. Geoid and gravity anomaly data of conjugate regions of Bay of Bengal and Enderby Basin: New constraints on breakup and early spreading history between India and Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Krishna, K.S.; Michael, L.; Bhattacharyya, R.; Majumdar, T.J.

    the rifting process in the north between combined north ECMI-Elan Bank and MacRobertson Land and in the south between southwest Sri Lanka and Gunnerus Ridge region of East Antarctica. Approximately during the period between the anomalies M1 and M0 and soon...

  9. Breeding strategies of Antarctic Petrels Thalassoica antarctica and Southern Fulmars Fulmarus glacialoides in the high Antarctic and implications for reproductive success

    NARCIS (Netherlands)

    Creuwels, J.C.S.; Franeker, van J.A.; Doust, S.J.; Beinssen, A.; Harding, B.; Hentschel, O.

    2008-01-01

    Breeding strategies of two closely related fulmarine petrels were studied on Ardery Island, on the continental coast of East Antarctica, where short summers are expected to narrow the time-window for reproduction. Both species had a similar breeding period (97 days from laying to fledging) but

  10. Breeding strategies of Antarctic Petrels Thalassoica antarctica and Southern Fulmars Fulmarus glacialoides in the high Antarctic and implications for reproductive success

    NARCIS (Netherlands)

    Creuwels, Jeroen C. S.; Van Franeker, Jan A.; Doust, Susan J.; Beinssen, Anna; Harding, Belinda; hentschel, Oliver

    Breeding strategies of two closely related fulmarine petrels were studied on Ardery Island, on the continental coast of East Antarctica, where short summers are expected to narrow the time-window for reproduction. Both species had a similar breeding period (97 days from laying to fledging) but

  11. Seafloor spreading magnetic anomalies in the Enderby Basin, East Antarctic

    Digital Repository Service at National Institute of Oceanography (India)

    Ramana, M.V.; Ramprasad, T.; Desa, M.

    - netic anomalies along the few available regional pro¢les of di¡erent azimuths in the Bay of Ben- gal. The lack of a good data set in the Enderby Basin, o¡ East Antarctica, further prevented re- solving the opening time of the northeastern In- dian Ocean.... Consequently, there was no consen- sus on the precise timing of the separation of India from Antarctica. Two di¡erent opinions have prevailed. Curray et al. [22] and other work- ers [25,26] suggested a separation time around chron M0 time, though the presence...

  12. Blowing snow sublimation and transport over Antarctica from 11 years of CALIPSO observations

    Science.gov (United States)

    Palm, Stephen P.; Kayetha, Vinay; Yang, Yuekui; Pauly, Rebecca

    2017-11-01

    Blowing snow processes commonly occur over the earth's ice sheets when the 10 m wind speed exceeds a threshold value. These processes play a key role in the sublimation and redistribution of snow thereby influencing the surface mass balance. Prior field studies and modeling results have shown the importance of blowing snow sublimation and transport on the surface mass budget and hydrological cycle of high-latitude regions. For the first time, we present continent-wide estimates of blowing snow sublimation and transport over Antarctica for the period 2006-2016 based on direct observation of blowing snow events. We use an improved version of the blowing snow detection algorithm developed for previous work that uses atmospheric backscatter measurements obtained from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar aboard the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) satellite. The blowing snow events identified by CALIPSO and meteorological fields from MERRA-2 are used to compute the blowing snow sublimation and transport rates. Our results show that maximum sublimation occurs along and slightly inland of the coastline. This is contrary to the observed maximum blowing snow frequency which occurs over the interior. The associated temperature and moisture reanalysis fields likely contribute to the spatial distribution of the maximum sublimation values. However, the spatial pattern of the sublimation rate over Antarctica is consistent with modeling studies and precipitation estimates. Overall, our results show that the 2006-2016 Antarctica average integrated blowing snow sublimation is about 393 ± 196 Gt yr-1, which is considerably larger than previous model-derived estimates. We find maximum blowing snow transport amount of 5 Mt km-1 yr-1 over parts of East Antarctica and estimate that the average snow transport from continent to ocean is about 3.7 Gt yr-1. These continent-wide estimates are the first of their kind

  13. The oldest gibbon fossil (Hylobatidae from insular Southeast Asia: evidence from Trinil, (East Java, Indonesia, Lower/Middle Pleistocene.

    Directory of Open Access Journals (Sweden)

    Thomas Ingicco

    Full Text Available A fossil femur excavated by Eugène Dubois between 1891-1900 in the Lower/Middle Pleistocene bonebed of the Trinil site (Java, Indonesia was recognised by us as that of a Hylobatidae. The specimen, Trinil 5703 of the Dubois Collection (Leiden, The Netherlands, has the same distinctive form of fossilization that is seen in many of the bonebed fossils from Trinil in the collection. Anatomical comparison of Trinil 5703 to a sample of carnivore and primate femora, supported by morphometric analyses, lead to the attribution of the fossil to gibbon. Trinil 5703 therefore provides the oldest insular record of this clade, one of the oldest known Hylobatidae fossils from Southeast Asia. Because living Hylobatidae only inhabit evergreen rain forests, the paleoenvironment within the river drainage in the greater Trinil area evidently included forests of this kind during the Lower/Middle Pleistocene as revealed here.

  14. The oldest gibbon fossil (Hylobatidae) from insular Southeast Asia: evidence from Trinil, (East Java, Indonesia), Lower/Middle Pleistocene.

    Science.gov (United States)

    Ingicco, Thomas; de Vos, John; Huffman, O Frank

    2014-01-01

    A fossil femur excavated by Eugène Dubois between 1891-1900 in the Lower/Middle Pleistocene bonebed of the Trinil site (Java, Indonesia) was recognised by us as that of a Hylobatidae. The specimen, Trinil 5703 of the Dubois Collection (Leiden, The Netherlands), has the same distinctive form of fossilization that is seen in many of the bonebed fossils from Trinil in the collection. Anatomical comparison of Trinil 5703 to a sample of carnivore and primate femora, supported by morphometric analyses, lead to the attribution of the fossil to gibbon. Trinil 5703 therefore provides the oldest insular record of this clade, one of the oldest known Hylobatidae fossils from Southeast Asia. Because living Hylobatidae only inhabit evergreen rain forests, the paleoenvironment within the river drainage in the greater Trinil area evidently included forests of this kind during the Lower/Middle Pleistocene as revealed here.

  15. Spatial and Temporal Variability in Seismicity of the East Pacific Rise: Constraints from Hydroacoustic Monitoring and Evidence for Triggering of Transform Earthquakes

    Science.gov (United States)

    Gregg, P. M.; Smith, D. K.; Lin, J.

    2003-12-01

    We utilize hydroacoustic data collected since May 1996 by NOAA's Equatorial Pacific autonomous hydrophone array to investigate the first order spatial and temporal variability of seismicity at the East Pacific Rise (EPR) within the array. We also investigate earthquake stress interaction and triggering at three sites: the Clipperton and Siqueirous transform faults, which are part of the Ridge2000 EPR Integrated Study Site (ISS), as well as a section of the ridge at 5.4° S near the Gofar transform fault. Our analyses reveal strong evidence of seismic clustering along the EPR. The majority of earthquakes (>90%) clustered in seismic swarms, in which individual events occurred within a few km and within minutes or hours of each other. Through correlating hydrophone data to teleseismically recorded events, we have located several moderate size earthquakes on the Siqueiros and Clipperton transforms. Some of these moderate size events occurred closely in space and time, suggesting the possibility of earthquake triggering. At 5.4° S we found evidence for possible interaction between two moderate size events, one of which occurred on the EPR axis and the other about 100 km northward on the Gofar transform fault. Stress calculations were carried out for several pairs of the moderate size events. The close correlation of the calculated Coulomb stress changes with the observed spatial and temporal variations in seismicity patterns provide strong evidence for possible earthquake triggering along the transform faults. This might have important implications for processes acting in the EPR ISS, including the relationship between seismicity and changes in hydrothermal circulation patterns.

  16. Textural evidence of the significance of compaction in the formation of adcumulates in the Skaergaard intrusion, East Greenland

    Science.gov (United States)

    Vukmanovic, Zoja; Holness, Marian; Mariani, Elisabetta

    2017-04-01

    It has been argued that the upwards decrease in incompatible element concentration in the Skaergaard Layered Series is due to an upwards increasing significance of compaction driven by gravitational loading. The suggested mechanisms for compaction are dislocation creep and dissolution-reprecipitation creep. Localised elongate zones of strong modal banding in the upper part of the Layered Series, known as trough bands, have also been interpreted as the result of localised recrystallization during compaction. In this study we examine the microstructures of Skaergaard gabbros to determine whether their fabrics (foliations and lineations) preserve a record of compaction. The most common microstructures formed by dislocation creep are low angle boundaries and, as a result of ongoing recovery processes, new grains. The (010)[001] slip system in plagioclase is commonly observed to be a "soft" orientation, creating a crystallographic preferred orientation (CPO) defined by the alignment of (010) planes, with [001] parallel to lineation. Previous work on dissolution-reprecipitation creep, shows a CPO with (010) planes aligned parallel to the principal compressive stress, and preferential mineral growth on (010) planes to form an SPO defined by grains elongated perpendicular to (010). In the Skaergaard Layered Series, the shape of cumulus plagioclase grains (as viewed in thin section) changes systematically up through the stratigraphy from highly tabular to equant. Foliations, defined both by a plagioclase SPO (with tabular grains aligned horizontally) and an associated CPO ((010) parallel to foliation), are strongest lower in the stratigraphy and reduce in strength upwards. Evidence for crystal plasticity is limited to bending of some plagioclase crystals and small numbers of low angle boundaries in all phases. There are no signs of recovery associated with dislocation creep. Compositional zoning is present on all plagioclase growth faces in the lower part of the

  17. Estimating radiotherapy demands in South East Asia countries in 2025 and 2035 using evidence-based optimal radiotherapy fractions.

    Science.gov (United States)

    Yahya, Noorazrul; Roslan, Nurhaziqah

    2018-01-08

    As about 50% of cancer patients may require radiotherapy, the demand of radiotherapy as the main treatment to treat cancer is likely to rise due to rising cancer incidence. This study aims to quantify the radiotherapy demand in countries in Southeast Asia (SEA) in 2025 and 2035 using evidence-based optimal radiotherapy fractions. SEA country-specific cancer incidence by tumor site for 2015, 2025 and 2035 was extracted from the GLOBOCAN database. We utilized the optimal radiotherapy utilization rate model by Wong et al. (2016) to calculate the optimal number of fractions for all tumor sites in each SEA country. The available machines (LINAC & Co-60) were extracted from the IAEA's Directory of Radiotherapy Centres (DIRAC) from which the number of available fractions was calculated. The incidence of cancers in SEA countries are expected to be 1.1 mil cases (2025) and 1.4 mil (2035) compared to 0.9 mil (2015). The number of radiotherapy fractions needed in 2025 and 2035 are 11.1 and 14.1 mil, respectively, compared to 7.6 mil in 2015. In 2015, the radiotherapy fulfillment rate (RFR; required fractions/available fractions) varied between countries with Brunei, Singapore and Malaysia are highest (RFR > 1.0 - available fractions > required fractions), whereas Cambodia, Indonesia, Laos, Myanmar, Philippines, Timor-Leste and Vietnam have RFR fractions, estimation for number of machines required can be obtained which will guide acquisition of machines in SEA countries. RFR is low with access varied based on the economic status. © 2018 John Wiley & Sons Australia, Ltd.

  18. SNOW SURFACE FEATURES ALONG THE TRAVERSE ROUTE FROM THE COAST TO DOME FUJI STATION, QUEEN MAUD LAND, ANTARCTICA

    OpenAIRE

    フルカワ, テルオ; カミヤマ, コキチ; マエノ, ヒデオ; Teruo, Furukawa; Kokichi, Kamiyama; Hideo, MAENO

    1996-01-01

    Frequencies of snow surface features such as sastrugi, dunes and thermal cracks were measured along the traverse route from the coastal region to the summit of the Queen Maud Land ice sheet, Dome Fuji Station, East Antarctica. The study route can be clearly divided into three regions on the basis of the regional characteristics of snow surface features : coastal region, katabatic wind region and inland plateau region. The coastal region is characterized by high frequency of small sastrugi and...

  19. 13C/Palynological evidence of differential residence times of organic carbon prior to its sedimentation in East African Rift Lakes and peat bogs

    Science.gov (United States)

    Hillaire-Marcel, Claude; Aucour, Anne-Marie; Bonnefille, Raymonde; Riollet, Guy; Vincens, Annie; Williamson, David

    Most terrestrial plants producing large amounts of organic matter in the East African Rift follow the Calvin (C3) photosynthetic pathway. Their end products have δ13C values of ca. -27 ± 2‰ (vs. PDB). On the contrary, most Cyperaceae (notably Cyperus papyrus and C. latifolius) are characterized by higher 13C contents ° 13C = -10.5 ± 1‰ ) in relation to their Hatch and Slack (C4) photosynthetic cycle. In consequence, δ13C values in total organic matter (TOM) from peat bog or lake cores essentially responded to the proportion of detritus from C4-Cyperaceae. Immediate evidence of the development or disappearance of Cyperaceae around lake margins or in peat bogs can be found in pollen assemblages. Lag times between pollen signals and correlative ° 13C shifts in TOM from cores are therefore indicative of the residence time of organic matter prior to its sedimentation. Delayed sedimentation of TOM will result in 14C anomalies which depend on several parameters, most of them being site specific as shown by examples from a peat bog in Burundi and from southern Lake Tanganyika. An independent assessment of the chronology by high resolution paleomagnetic correlations indicates a ca. 1.5 ka apparent 14C age of TOM in Lake Tanganyika at the Pleistocene-Holocene transition.

  20. Evidence for coherent spicule oscillations from correcting Hinode/SOT Ca II H in the south-east limb of the Sun

    Science.gov (United States)

    Ahangarzadeh Maralani, A. R.; Tavabi, E.; Ajabshirizadeh, A.

    2017-05-01

    Wave theories of heating of the chromosphere, corona and solar wind due to photospheric fluctuations are strengthened by the existence of the wave coherency observed up to the transition region. The coherency of intensity oscillations of solar spicules was explored using the Solar Optical Telescope (SOT) on the Hinode spacecraft with increasing height above the solar limb in the active region. We used time sequences near the south-east region from the Hinode/SOT for the Ca II H line obtained on 2015 April 3 and applied the de-convolution procedure to the spicule to illustrate how effectively our restoration method works on fine structures such as spicules. Moreover, the intensity oscillations at different heights above the solar limb were analysed through wavelet transforms. Afterwards, the phase difference was measured between oscillations at two heights in search of evidence for coherent oscillations. The results of the wavelet transformations revealed dominant period peaks for 2, 4, 5.5 and 6.5 min at four separate heights. The dominant frequencies for a coherency level higher than 75 per cent were found to be around 5.5 and 8.5 mHz. Mean phase speeds of 155-360 km s-1 were measured. We found that the mean phase speeds increased with height. The results suggest that the energy flux carried by coherent waves into the corona and heliosphere may be several times larger than previous estimates that were based solely on constant velocities. We provide compelling evidence for the existence of upwardly propagating coherent waves.

  1. A Vibroseis Seismic Source for Climate, Ice Sheet and Tectonic Studies in Antarctica

    Science.gov (United States)

    Speece, M. A.; Luyendyk, B. P.; Powell, R. D.; Wilson, D. S.; Pekar, S. F.; Harwood, D. M.; Tulaczyk, S. M.

    2012-12-01

    -glacial lakes and water-routing systems, and (5) investigating the seismic properties of ice sheets. Suggested seismic profiles include the South Pole traverse route across the Ross Ice Shelf with diversion routes to Coulman High and the Siple Coast. Additional profiles are planned for Byrd Station to West Antarctic Ice Sheet (WAIS) Divide camp and continuing to Pine Island Glacier, and over the 'Discovery Deep' trough, seaward of Byrd Glacier in the eastern Ross Embayment. Projects to consider for the long term include the boundary between West and East Antarctica that is expressed as the Transantarctic Mountains Front. Existing seismic data to define the structures at this boundary are limited. Basins in bedrock behind these mountains are proposed to be sediment free but no seismic reflection data exist to support that hypothesis. The recent detailed mapping of the bedrock of the Gamburtsev Mountains and the nearby Lambert Graben offer further targets for exploration of East Antarctica. An overland traverse has been established between South Pole and the AGAP South site where aerogeophysical surveys over these mountains were based, and this traverse route could be the starting point of a vibroseis research program in East Antarctica.

  2. Radarsat survey provides accurate map of Antarctica

    Science.gov (United States)

    Showstack, Randy

    Explorers of Antarctica have trudged with dog sleds, wintered in boats trapped in ice, and daringly flown across the coldest, windiest, highest, driest, and most desolate continental expanse. Their names are legendary: Ross, Scott, Amundsen, Byrd. And now add Radarsat.Taking about 5,500 microwave images over 18 days—from September 26 through October 14—a synthetic aperture radar (SAR) on this Earth-orbiting satellite completed the first-ever, real-time and high-resolution radar survey of Antarctica last week. The Canadian Space Agency (CSA) satellite, orbiting 800 km above Antarctica, accomplished this task by performing an unusual 180° yaw, or rotational maneuver, for NASA and the National Oceanic and Atmospheric Administration (NOAA).

  3. The Landsat Image Mosaic of Antarctica (LIMA): A Cutting-Edge Way for Students and Teachers to Learn about Antarctica

    Science.gov (United States)

    Campbell, Brian; Bindschadler, Robert

    2009-01-01

    By studying Antarctica via satellite and through ground-truthing research, we can learn where the ice is melting and why. The Landsat Image Mosaic of Antarctica (LIMA), a new and cutting-edge way for scientists, researchers, educators, students, and the public to look at Antarctica, supports this research and allows for unprecedented views of our…

  4. Discovery of large conical stromatolites in Lake Untersee, Antarctica.

    Science.gov (United States)

    Andersen, D T; Sumner, D Y; Hawes, I; Webster-Brown, J; McKay, C P

    2011-05-01

    Lake Untersee is one of the largest (11.4 km(2)) and deepest (>160 m) freshwater lakes in East Antarctica. Located at 71°S the lake has a perennial ice cover, a water column that, with the exception of a small anoxic basin in the southwest of the lake, is well mixed, supersaturated with dissolved oxygen, alkaline (pH 10.4) and exceedingly clear. The floor of the lake is covered with photosynthetic microbial mats to depths of at least 100 m. These mats are primarily composed of filamentous cyanophytes and form two distinct macroscopic structures, one of which--cm-scale cuspate pinnacles dominated by Leptolyngbya spp.--is common in Antarctica, but the second--laminated, conical stromatolites that rise up to 0.5 m above the lake floor, dominated by Phormidium spp.--has not previously been reported in any modern environment. The laminae that form the conical stromatolites are 0.2-0.8 mm in thickness consisting of fine clays and organic material; carbon dating implies that laminations may occur on near decadal timescales. The uniformly steep sides (59.6 ± 2.5°) and the regular laminar structure of the cones suggest that they may provide a modern analog for growth of some of the oldest well-described Archean stromatolites. Mechanisms underlying the formation of these stromatolites are as yet unclear, but their growth is distinct from that of the cuspate pinnacles. The sympatric occurrence of pinnacles and cones related to microbial communities with distinct cyanobacterial compositions suggest that specific microbial behaviors underpin the morphological differences in the structures. © 2011 Blackwell Publishing Ltd.

  5. Scientific Experiences Using Argentinean Sounding Rockets in Antarctica

    Science.gov (United States)

    Sánchez-Peña, Miguel

    2000-07-01

    Argentina in the sixties and seventies, had experience for developing and for using sounding rockets and payloads to perform scientific space experiments. Besides they have several bases in Antarctica with adequate premises and installations, also duly equipped aircrafts and trained crews to flight to the white continent. In February 1965, scientists and technical people from the "Instituto de Investigacion Aeronáutica y Espacial" (I.I.A.E.) with the cooperation of the Air Force and the Tucuman University, conducted the "Matienzo Operation" to measure X radiation and temperature in the upper atmosphere, using the Gamma Centauro rocket and also using big balloons. The people involved in the experience, the launcher, other material and equipment flew from the south tip of Argentina to the Matienzo base in Antarctica, in a C-47 aircraft equipped with skies an additional jet engine Marbore 2-C. Other experience was performed in 1975 in the "Marambio" Antartic Base, using the two stages solid propellent sounding rocket Castor, developed in Argentina. The payload was developed in cooperation with the Max Planck Institute of Germany. It consist of a special mixture including a shape charge to form a ionized cloud producing a jet of electrons travelling from Marambio base to the conjugate point in the Northern hemisphere. The cloud was observed by several ground stations in Argentina and also by a NASA aircraft with TV cameras, flying at East of New York. The objective of this experience was to study the electric and magnetic fields in altitude, the neutral points, the temperature and electrons profile. The objectives of both experiments were accomplished satisfactorily.

  6. Acting Antarctica: science on stage

    Science.gov (United States)

    Ciceri, Piera; Tizzoni, Paola; Pierro, Luigia

    2016-04-01

    Key-words: Polar science, Earth science, Theatre, Hands on activities The legendary Antarctic Expedition of sir E. Shackleton and his crew of 27 aboard the Endurance (1914/16) trapped in the Antarctic ice has become the starting point to learn about Polar Science and Climate Change. While the students were involved into this incredible adventure by the astonishing images of the Australian photographer Frank Hurley (who joined the crew), they discovered the world in which this story happened. Students were then involved in hands-on activities and role plays and have become the writers of the play "Uomini a scienza ai confini del mondo". They act the story of Shackelton's expedition and they tell at the same time to the audience about ice pack, ice cores and their role in understanding the past of the climate, physical and geographical characteristic of polar regions, thermal phenomena related to adaptations of polar animals, solar radiation at different latitude, day/night duration. The theater was the place to "stage" some scientific experiments and to explain the current research carried out in polar regions and their importance in climate change studies and to stress some similarities between Antarctica and space. The project was carried out from teachers of science, letters and geography and was born in collaboration with the "Piccolo Teatro di Milano" and the association "Science Under 18" with the support of a professional actor and director and was played for other schools at "EXPO 2015" in Milano (Italy). In our opinion drama activities improve reading comprehension, and both verbal and non-verbal communication skills. To be able to write and to act, students need a deep understanding of contents. Arts, including theatre, are a good key to involve emotionally students. To have an audience different from their own teachers and classmates offers a real task and the opportunity to play and let grow real skills.

  7. Implementing evidence-based continuous quality improvement strategies in an urban Aboriginal Community Controlled Health Service in South East Queensland: a best practice implementation pilot.

    Science.gov (United States)

    Hogg, Sandra; Roe, Yvette; Mills, Richard

    2017-01-01

    The Institute for Urban Indigenous Health believes that continuous quality improvement (CQI) contributes to the delivery of high-quality care, thereby improving health outcomes for Aboriginal and Torres Strait Islander people. The opening of a new health service in 2015 provided an opportunity to implement best practice CQI strategies and apply them to a regional influenza vaccination campaign. The aim of this project was to implement an evidence-based CQI process within one Aboriginal Community Controlled Health Service in South East Queensland and use staff engagement as a measure of success. A CQI tool was selected from the Joanna Briggs Institute Practical Application of Clinical Evidence System (PACES) to be implemented in the study site. The study site was a newly established Aboriginal and Torres Strait Islander Community Controlled Health Service located in the northern suburbs of Brisbane. This project used the evidence-based information collected in PACES to develop a set of questions related to known variables resulting in proven CQI uptake. A pre implementation clinical audit, education and self-directed learning, using the Plan Do Study Act framework, included a total of seven staff and was conducted in April 2015. A post implementation audit was conducted in July 2015. There were a total of 11 pre- and post-survey respondents which included representation from most of the clinical team and medical administration. The results of the pre implementation audit identified a number of possible areas to improve engagement with the CQI process including staff training and support, understanding CQI and its impacts on individual work areas, understanding clinical data extraction, clinical indicator benchmarking, strong internal leadership and having an external data extractor. There were improvements to all audit criteria in the post-survey, for example, knowledge regarding the importance of CQI activity, attendance at education and training sessions on CQI

  8. Phaeosphaeria deschampsii (Ascomycota): A new parasite species of Deschampsia antarctica (Poaceae) described to Antarctica.

    Science.gov (United States)

    Putzke, Jair; Pereira, Antonio B

    2016-01-01

    This study presents the description of Phaeosphaeria deschampsii, which was found in plant communities from Half Moon Island, South Shetland Archipelago, Antarctica, in February 2014. Many patches of Deschampsia antarctica (Poaceae), the only indigenous Poaceae specie in Antarctic, were found dead, parasitized by a fungi pathogen. Based on the shape of its perithecia, with oblique neck, erumpent in the grass tissues, ascospore form and septation, the specie was identified as new to science.

  9. New evidence for Kuroshio inflow and deepwater circulation in the Okinawa Trough, East China Sea: Sedimentary mercury variations over the last 20 kyr

    Science.gov (United States)

    Lim, Dhongil; Kim, Jihun; Xu, Zhaokai; Jeong, Kapsik; Jung, Hoisoo

    2017-06-01

    The evolution of the Kuroshio Current (KC) in the Okinawa Trough (OT) has long been of paleoceanographic interest and has been the focus of many investigations because of its large impacts on both the ocean environment and the climate in East Asia. Here we present a new high-resolution mercury (Hg) record from the OT sediments that provides robust evidence for the glacial-interglacial variabilities of KC inflow. The Hg levels are anomalously high in the Holocene deposits, which feature a large and abrupt Hg increase at 9.6 ka and a significant drop at 4.5-3.2 ka. Our observations show that most Hg was derived from seafloor hydrothermal plumes via active lateral transportation. Thus, the generally high Hg levels since 9.6 ka are associated with enhanced basin-wide deepwater circulation triggered by the KC inflow. This driving mechanism for the deposition and widespread of Hg is also evidenced by an abrupt drop in Hg levels during the late Holocene neoglacial cold period ( 5-3 ka) when the KC inflow was temporarily interrupted and deepwater circulation was consequently weak or even absent in the OT. The changes in sedimentary Hg appear to be synchronous with those in other geochemical proxies that suggest that bottom water conditions switched from anoxic to oxic due to increased upwelling from the bottom in tandem with the strengthening KC and reduced freshwater effect since 9.6 ka. This study shows that the hydrothermal Hg is a sensitive and independent tool for the reconstruction of paleodynamics of KC in the OT.

  10. Read--and Walk--to Antarctica

    Science.gov (United States)

    Harr, Natalie; Doneyko, Kathleen; Lee, Richard E., Jr.

    2012-01-01

    The students at Crestwood Primary School proved that they have what it takes to exercise their bodies and their minds. In an effort to support their teacher's scientific expedition to Antarctica, students from kindergarten to second grade pledged to read books and do physical activity that equated to the 12,900 km (8,000-mile) journey to the…

  11. Antarctica: Is It More Than Just Ice?

    Science.gov (United States)

    Johnson, Cheryl; Gutierrez, Melida

    2009-01-01

    The authors introduced polar science in a fourth-grade classroom by means of 3 hands-on activities that addressed (1) the melting of glaciers and ice, (2) the differences between the North and the South Pole, and (3) the geography and landforms of Antarctica. An assessment 4 months after the original activity showed that students remembered the…

  12. Physical properties of aerosols at Maitri, Antarctica

    Indian Academy of Sciences (India)

    Measurements of the submicron aerosol size distribution made at the Indian Antarctic station, Maitri (70° 45′S, 11° 44′E) from January 10th to February 24th, 1997, are reported. Total aerosol concentrations normally range from 800 to 1200 particles cm-3 which are typical values for the coastal stations at Antarctica in ...

  13. First airborne transient em survey in antarctica

    DEFF Research Database (Denmark)

    Auken, Esben; Mikucki, J. J.; Sørensen, Kurt Ingvard K.I.

    2012-01-01

    A first airborne transient electromagnetic survey was flown in Antarctica in December 2011 with the SkyTEM system. This transient airborne EM system has been optimized in Denmark for almost ten years and was specially designed for ground water mapping. The SkyTEM tool is ideal for mapping...

  14. Ostracoda from Vestfold Hill lake terraces, Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Setty, M.G.A.P.

    Six species of ostracodes are recorded from two transects of terraces of Deep Lake, Vestfold Hills, Antarctica. Two species (@iXesteleberis@@ sp. and @iBradleya dictyon@@) range from Cretaceous to Recent, @iPoseidonamicus aff. P. major@@ ranges from...

  15. Challenges in protecting the wilderness of Antarctica

    Science.gov (United States)

    Tina Tin; Alan Hemmings

    2011-01-01

    Since 1998, the wilderness values of Antarctica have been among those given legal recognition under the Protocol on Environmental Protection to the Antarctic Treaty. Despite the legal obligation, on-the-ground implementation has attracted little interest. The term "wilderness" and its consequential operational implication, including the designation of...

  16. Postspreading rifting in the Adare Basin, Antarctica: Regional tectonic consequences

    Science.gov (United States)

    Granot, R.; Cande, S. C.; Stock, J. M.; Davey, F. J.; Clayton, R. W.

    2010-08-01

    Extension during the middle Cenozoic (43-26 Ma) in the north end of the West Antarctic rift system (WARS) is well constrained by seafloor magnetic anomalies formed at the extinct Adare spreading axis. Kinematic solutions for this time interval suggest a southward decrease in relative motion between East and West Antarctica. Here we present multichannel seismic reflection and seafloor mapping data acquired within and near the Adare Basin on a recent geophysical cruise. We have traced the ANTOSTRAT seismic stratigraphic framework from the northwest Ross Sea into the Adare Basin, verified and tied to DSDP drill sites 273 and 274. Our results reveal three distinct periods of tectonic activity. An early localized deformational event took place close to the cessation of seafloor spreading in the Adare Basin (˜24 Ma). It reactivated a few normal faults and initiated the formation of the Adare Trough. A prominent pulse of rifting in the early Miocene (˜17 Ma) resulted in normal faulting that initiated tilted blocks. The overall trend of structures was NE-SW, linking the event with the activity outside the basin. It resulted in major uplift of the Adare Trough and marks the last extensional phase of the Adare Basin. Recent volcanic vents (Pliocene to present day) tend to align with the early Miocene structures and the on-land Hallett volcanic province. This latest phase of tectonic activity also involves near-vertical normal faulting (still active in places) with negligible horizontal consequences. The early Miocene extensional event found within the Adare Basin does not require a change in the relative motion between East and West Antarctica. However, the lack of subsequent rifting within the Adare Basin coupled with the formation of the Terror Rift and an on-land and subice extension within the WARS require a pronounced change in the kinematics of the rift. These observations indicate that extension increased southward, therefore suggesting that a major change in

  17. Did clockwise rotation of Antarctica cause the break-up of Gondwanaland? An investigation in the 'deep-keeled cratons' frame for global dynamics

    Science.gov (United States)

    Osmaston, M. F.

    2012-04-01

    Introduction. The 'deep-keeled cratons' frame for global dynamics is the result of seeking Earth-behaviour answers to the following outside-the-box proposition:- "If cratons have tectospheric keels that reach or approach the 660 km discontinuity, AND the 660 level is an effective barrier to mantle circulation, then obviously (i) when two cratons separate, the upper mantle to put under the nascent ocean must arrive by a circuitous route and, conversely, (ii) if they approach one another, the mantle volume that was in between them must get extruded sideways." Surprisingly it has turned out [1 - 4] that Earth dynamical behaviour for at least the past 150 Ma provides persuasive affirmation of both these expectations and that there is a rational petrological explanation for the otherwise-unexpected immobility of subcratonic material to such depths [5 - 7]. Clockwise rotation of Antarctica? This contribution greatly amplifies my original plate dynamical arguments for suggesting [8] that such rotation is ongoing. Convection is unsuited to causing rotation about a pole within the plate so, as noted then, a gearwheel-like linkage to Africa at the SWIR would provide its clearly CCW (Biscay-Caucasus) relationship to the Mediterranean belt for the past 100 Ma, also seen in its separation from South America. Gearwheel-like linkage of motion requires the presence of some kind of E-W restraint further north. In that case it was the N Africa/Arabia involvement in the Alpide belt, but the earlier opening of the central Atlantic by the eastward motion of Africa, suggests its rigid Gondwanan attachment to Antarctica rotation at that time, with little constraint in the north. Further east, the seafloor data show that Australia-Antarctica separation involved no such opposite rotational linkage, so, with no E-W mechanical constraint in the north by Indonesia, they must have rotated together, as is recorded by Australia's eastward motion to generate the Mesozoic seafloor at its western

  18. Association of the OCA2 polymorphism His615Arg with melanin content in east Asian populations: further evidence of convergent evolution of skin pigmentation.

    Directory of Open Access Journals (Sweden)

    Melissa Edwards

    2010-03-01

    Full Text Available The last decade has witnessed important advances in our understanding of the genetics of pigmentation in European populations, but very little is known about the genes involved in skin pigmentation variation in East Asian populations. Here, we present the results of a study evaluating the association of 10 Single Nucleotide Polymorphisms (SNPs located within 5 pigmentation candidate genes (OCA2, DCT, ADAM17, ADAMTS20, and TYRP1 with skin pigmentation measured quantitatively in a sample of individuals of East Asian ancestry living in Canada. We show that the non-synonymous polymorphism rs1800414 (His615Arg located within the OCA2 gene is significantly associated with skin pigmentation in this sample. We replicated this result in an independent sample of Chinese individuals of Han ancestry. This polymorphism is characterized by a derived allele that is present at a high frequency in East Asian populations, but is absent in other population groups. In both samples, individuals with the derived G allele, which codes for the amino acid arginine, show lower melanin levels than those with the ancestral A allele, which codes for the amino acid histidine. An analysis of this non-synonymous polymorphism using several programs to predict potential functional effects provides additional support for the role of this SNP in skin pigmentation variation in East Asian populations. Our results are consistent with previous research indicating that evolution to lightly-pigmented skin occurred, at least in part, independently in Europe and East Asia.

  19. Seismic Investigations of the Crust and Upper Mantle Structure in Antarctica and Madagascar

    Science.gov (United States)

    Ramirez, Cristo

    In the three studies that form this dissertation, seismic data from Antarctica and Madagascar have been analyzed to obtain new insights into crustal structure and mantle flow. Until recently, there have been little seismic data available from these areas for interrogating Earth structure and processes. In Antarctica, I analyzed datasets from temporary deployments of broadband seismic stations in both East and West Antarctica. In Madagascar, I analyzed data from a temporary network of broadband stations, along with data from three permanent stations. The seismic data have been processed and modeled using a wide range of techniques to characterize crust and mantle structure. Crustal structure in the East Antarctic Craton resembles Precambrian terrains around the world in its thickness and shear wave velocities. The West Antarctic Rift System has thinner crust, consistent with crustal thickness beneath other Cretaceous rifts. The Transantarctic Mountains show thickening of the crust from the costal regions towards the interior of the mountain range, and high velocities in the lower crust at several locations, possibly resulting from the Ferrar magmatic event. Ross Island and Marie Byrd Land Dome have elevated crustal Vp/Vs ratios, suggesting the presence of partial melt and/or volcaniclastic material within the crust. The pattern of seismic anisotropy in Madagascar is complex and cannot arise solely due to mantle flow from the African superplume, as previously proposed. To explain the complex pattern of anisotropy, a combination of mechanisms needs to be invoked, including mantle flow from the African superplume, mantle flow from the Comoros hotspot, small scale upwelling in the mantle induced by lithospheric delamination, and fossil anisotropy in the lithospheric mantle along Precambrian shear zones.

  20. Improved representation of East Antarctic surface mass balance in a regional atmospheric climate model

    NARCIS (Netherlands)

    Van Wessem, J. M.; Reijmer, C. H.; Morlighem, M.; Mouginot, J.; Rignot, E.; Medley, B.; Joughin, I.; Wouters, B.; Depoorter, M. A.; Bamber, J. L.; Lenaerts, J. T M; Van De Berg, W. J.; Van Den Broeke, M. R.; Van Meijgaard, E.

    2014-01-01

    This study evaluates the impact of a recent upgrade in the physics package of the regional atmospheric climate model RACMO2 on the simulated surface mass balance (SMB) of the Antarctic ice sheet. The modelled SMB increases, in particular over the grounded ice sheet of East Antarctica (+44Gt a-1),

  1. East Antarctic rifting triggers uplift of the Gamburtsev Mountains.

    Science.gov (United States)

    Ferraccioli, Fausto; Finn, Carol A; Jordan, Tom A; Bell, Robin E; Anderson, Lester M; Damaske, Detlef

    2011-11-16

    The Gamburtsev Subglacial Mountains are the least understood tectonic feature on Earth, because they are completely hidden beneath the East Antarctic Ice Sheet. Their high elevation and youthful Alpine topography, combined with their location on the East Antarctic craton, creates a paradox that has puzzled researchers since the mountains were discovered in 1958. The preservation of Alpine topography in the Gamburtsevs may reflect extremely low long-term erosion rates beneath the ice sheet, but the mountains' origin remains problematic. Here we present the first comprehensive view of the crustal architecture and uplift mechanisms for the Gamburtsevs, derived from radar, gravity and magnetic data. The geophysical data define a 2,500-km-long rift system in East Antarctica surrounding the Gamburtsevs, and a thick crustal root beneath the range. We propose that the root formed during the Proterozoic assembly of interior East Antarctica (possibly about 1 Gyr ago), was preserved as in some old orogens and was rejuvenated during much later Permian (roughly 250 Myr ago) and Cretaceous (roughly 100 Myr ago) rifting. Much like East Africa, the interior of East Antarctica is a mosaic of Precambrian provinces affected by rifting processes. Our models show that the combination of rift-flank uplift, root buoyancy and the isostatic response to fluvial and glacial erosion explains the high elevation and relief of the Gamburtsevs. The evolution of the Gamburtsevs demonstrates that rifting and preserved orogenic roots can produce broad regions of high topography in continental interiors without significantly modifying the underlying Precambrian lithosphere. © 2011 Macmillan Publishers Limited. All rights reserved

  2. Coastal-change and glaciological map of the Amery Ice Shelf area, Antarctica: 1961–2004

    Science.gov (United States)

    Foley, Kevin M.; Ferrigno, Jane G.; Swithinbank, Charles; Williams, Richard S.; Orndorff, Audrey L.

    2013-01-01

    Reduction in the area and volume of Earth’s two polar ice sheets is intricately linked to changes in global climate and to the resulting rise in sea level. Measurement of changes in area and mass balance of the Antarctic ice sheet was given a very high priority in recommendations by the Polar Research Board of the National Research Council. On the basis of these recommendations, the U.S. Geological Survey used its archive of satellite images to document changes in the cryospheric coastline of Antarctica and analyze the glaciological features of the coastal regions. Amery Ice Shelf, lying between 67.5° and 75° East longitude and 68.5° and 73.2° South latitude, is the largest ice shelf in East Antarctica. The latest measurements of the area of the ice shelf range between 62,620 and 71,260 square kilometers. The ice shelf is fed primarily by Lambert, Mellor, and Fisher Glaciers; its thickness ranges from 3,000 meters in the center of the grounding line to less than 300 meters at the ice front. Lambert Glacier is considered to be the largest glacier in the world, and its drainage basin is more than 1 million square kilometers in area. It is possible to see some coastal change on the outlet glaciers along the coast, but most of the noticeable change occurs on the Amery Ice Shelf front.

  3. The application of Dempster-Shafer theory of evidence for assessing groundwater vulnerability at Galal Badra basin, Wasit governorate, east of Iraq

    Science.gov (United States)

    Al-Abadi, Alaa M.

    2017-07-01

    The process of delineating areas that are more susceptible to pollution from anthropogenic sources has become an important issue for groundwater resources management and land-use planning. In this study, an attempt was made to delineate aquifer vulnerability zones for nitrate contamination at Galal Badra basin, east of Iraq using Dempster-Shafer method of evidence in GIS platform. First, an inventory map of the wells with elevated nitrate concentration (>3 mg/L) was prepared. The map showed that there are 63 wells with elevated nitrate concentrations in the study area. These data were partitioned randomly into two sets, for training and testing. The partition criterion was 70/30, 44 wells for training and 19 wells for testing. Then, the most influencing evidential thematic factors in determining aquifer vulnerability were selected depending on the availability of data. These factors were groundwater depth, hydraulic conductivity, slope, soil, and land use land cover (LULC). The spatial association between well locations and evidential thematic layers was investigated by means of mass functions (belief, disbelief, uncertainty, and plausibility) of Dempster-Shafer method. The integrated belief function was used to produce groundwater aquifer vulnerability index (GVI) for the study area. The pixel values of GVI were reclassified into five categories: very low, low, moderate, high, and very high using Jenks classification scheme. The very low-low zones cover 32 % (209 km2). These classes mainly concentrate on the eastern parts of the study area and occupy small zone in the central part. The moderate zone extends over an area of 42 % (279 km2) and mainly encompasses the western part of the study area. The high-very high zones cover 26 % (170 km2) and these zones concentrate on the central part of the study area. The results indicate that the aquifer system in the study area is moderately vulnerable to contamination by nitrate. The model was validated by using relative

  4. Post-bomb coral Δ14C record from Iki Island, Japan: possible evidence of oceanographic conditions on the northern East China Sea shelf

    Science.gov (United States)

    Mitsuguchi, Takehiro; Hirota, Masashi; Group, Paleo Labo AMS Dating; Yamazaki, Atsuko; Watanabe, Tsuyoshi; Yamano, Hiroya

    2016-10-01

    In this study, a sea-surface water Δ14C record of AD 1966-2000 (i.e., after the atmospheric nuclear-bomb testing period of the mid-1950s to early 1960s) was reconstructed from a coral sample collected from Iki Island, western Japan. The island is located in the Tsushima Strait where the Tsushima Current flows from the East China Sea (ECS) continental shelf into the Sea of Japan, indicating a strong influence of the ECS shelf water on the island. It is widely accepted that the Tsushima Current originates in the area between the ECS shelf break and the Nansei Islands further offshore as a branch of the Kuroshio Current, although another possible origin is the Taiwan-Tsushima Current System. The Δ14C record from Iki Island shows the following evidence of a response to the atmospheric nuclear testing: (1) an increase from ~55‰ in 1966 to ~133‰ in 1970, (2) a plateau ranging between ~123 and ~142‰ during the 1970s to the late 1980s, and (3) a gradual decrease from ~115‰ in 1990 to ~83‰ in 2000. Comparison of this record with coral Δ14C records from the Nansei Islands (Okinawa Island, Ishigaki Island and Kikai Island), located ~160-280 km off the ECS shelf break and little influenced by the shelf water, suggests that the surface-water Δ14C around Iki Island was ~30-45‰ lower than that of the Nansei Islands from the mid-1960s to late 1970s, and that the Δ14C difference between Iki Island and the Nansei Islands decreased from the end of the 1970s to ~0-15‰ in the mid-1980s to 2000. The lower Δ14C around Iki Island can be explained as follows: (1) in contrast to the Nansei Islands area, the ECS shelf area is a vertically mixed, highly concentrated carbon reservoir significantly connected to subsurface and deeper waters outside the shelf area, strongly suggesting that the surface-water Δ14C of the shelf area (perhaps excepting very shallow innermost shelf areas) was significantly less sensitive to the atmospheric nuclear-bomb 14C spike than that of the

  5. Surface ozone characterization at Larsemann Hills and Maitri, Antarctica.

    Science.gov (United States)

    Ali, Kaushar; Trivedi, D K; Sahu, S K

    2017-04-15

    Data are analyzed in terms of daily average ozone, its diurnal variation and its relation with meteorological parameters like dry bulb temperature (T), wet bulb temperature (T w ), atmospheric pressure and wind speed based on measurement of these parameters at two Indian Antarctic stations (Larsemann Hills, and Maitri) during 28th Indian Scientific Expedition of Antarctica (ISEA) organized during Antarctic summer of the year 2008-09. The work has been carried out to investigate summer time ozone level and its day-to-day and diurnal variability at these coastal locations and to highlight possible mechanism of ozone production and destruction. The result of the analysis indicates that daily average ozone concentration at Larsemann Hills varied from ~13 and ~20ppb with overall average value of ~16ppb and at Maitri, it varied from ~16 and ~21ppb with overall average value of ~18ppb. Photochemistry is found to partially contribute occasionally to the surface layer ozone at both the stations. Lower concentration of ozone at Maitri during beginning of the observational days may be due to destruction of ozone through activated halogens, whereas higher ozone on latter days may be due to photochemistry and advective transport from east to south-east areas. Ozone concentration during blizzard episodes at both the stations is reduced due to slow photochemical production of ozone, its photochemical removal and removal through deposition of ozone molecules on precipitation particles. Diurnal variation of ozone at Larsemann Hills and Maitri has been found to be absent. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Planetary geomorphology field studies: Iceland and Antarctica

    Science.gov (United States)

    Malin, M. C.

    1984-01-01

    Field studies of terrestrial landforms and the processes that shape them provide new directions to the study of planetary features. These studies, conducted in Iceland and in Antarctica, investigated physical and chemical weathering mechanisms and rates, eolitan processes, mudflow phenomena, drainage development, and catastrophic fluvial and volcanic phenomena. Continuing investigations in Iceland fall in three main catagories: (1) catastrophic floods of the Jokulsa a Fjollum, (2) lahars associated with explosive volcanic eruptions of Askja caldera, and (3) rates of eolian abrasion in cold, volcanic deserts. The ice-free valleys of Antarctica, in particular those in South Victoria Land, have much is common with the surface of Mars. In addition to providing independent support for the application of the Iceland findings to consideration of the martian erosional system, the Antarctic observations also provide analogies to other martian phenomena. For example, a family of sand dunes in Victoria Valley are stabilized by the incorporation of snow as beds.

  7. Heat Flux Distribution of Antarctica Unveiled

    Science.gov (United States)

    Martos, Yasmina M.; Catalán, Manuel; Jordan, Tom A.; Golynsky, Alexander; Golynsky, Dmitry; Eagles, Graeme; Vaughan, David G.

    2017-11-01

    Antarctica is the largest reservoir of ice on Earth. Understanding its ice sheet dynamics is crucial to unraveling past global climate change and making robust climatic and sea level predictions. Of the basic parameters that shape and control ice flow, the most poorly known is geothermal heat flux. Direct observations of heat flux are difficult to obtain in Antarctica, and until now continent-wide heat flux maps have only been derived from low-resolution satellite magnetic and seismological data. We present a high-resolution heat flux map and associated uncertainty derived from spectral analysis of the most advanced continental compilation of airborne magnetic data. Small-scale spatial variability and features consistent with known geology are better reproduced than in previous models, between 36% and 50%. Our high-resolution heat flux map and its uncertainty distribution provide an important new boundary condition to be used in studies on future subglacial hydrology, ice sheet dynamics, and sea level change.

  8. The oldest plesiosaur (Reptilia, Sauropterygia from Antarctica

    Directory of Open Access Journals (Sweden)

    Alexander Wilhelm Armin Kellner

    2011-06-01

    Full Text Available Antarctic plesiosaurs are known from the Upper Cretaceous López de Bertodano and Snow Hill Island formations (Campanian to upper Maastrichtian, which crop out within the James Ross Basin region of the Antarctic Peninsula. Here we describe the first plesiosaur fossils from the Lachman Crags Member of the Santa Marta Formation, north-western James Ross Island. This material constitutes the stratigraphically oldest plesiosaur occurrence presently known from Antarctica, extending the occurrence of plesiosaurians in this continent back to Santonian times (86.3–83.5 Mya. Furthermore, MN 7163-V represents the first plesiosaur from this region not referable to the Elasmosauridae nor Aristonectes, indicating a greater diversity of this group of aquatic reptiles in Antarctica than previously suspected.

  9. Antarctica - Lessons for a Mars exploration program

    Science.gov (United States)

    Mckay, C. P.

    1985-01-01

    The history of exploration and the international system of control of Antarctica has often been cited as a paradigm for the exploration of space. The small isolated research stations have been used to model the psychological stresses of future space missions. In addition, the programmatic structure of the U.S. Antarctic Research Program provides several possible analogs to future Mars Programs presently under discussion. These are: (1) Continued presence; (2) Civilian, military and private sector involvement; (3) Scientific activities; (4) Risk assessment and logistical support; (5) Accessibility for non-specialists; (6) Political and strategic motivations; (7) International cooperation/competition. Survival in Antarctica is contingent on advanced technology and the active transport of supplies. The scientific exploration of this remote and barren expanse without, of course, the aid and guidance of indigenous people certainly provides one of the closest analogs available to future science activities on the Martian surface.

  10. An east-west climate see-saw in the Mediterranean during the last 2.6 ka: evidence and mechanisms

    Science.gov (United States)

    Roberts, C.; Moreno-Caballud, A.; Valero-Garces, B. L.; Luterbacher, J.; Xoplaki, E.; Allcock, S. L.

    2012-12-01

    Global precipitation anomalies during the Common Era show a spatial coherency that appears to be about an order of magnitude lower (i.e. smaller) than for temperature changes, as some areas became wetter while others experienced drought (Seager et al., 2007, Quat. Sci. Rev. 26, 2322-36). The Mediterranean basin (10°W-40°E; 30°-45°N) is influenced by some of the main mechanisms acting upon the global climate system and its regional water resources are sensitive to hydro-climatic variations. Reconstructing the timing, intensity, and patterns of hydrological variability in the Mediterranean is important for testing spatial-temporal coherency in palaeo-precipitation, and for understanding underlying climate forcing mechanisms. The region offers a broad spectrum of documentary information and natural archives which allow high-resolution climate reconstructions (Luterbacher et al., 2012, In: Lionello et al. (eds) The Mediterranean Climate: from past to future. Elsevier, pp. 87-185). During the period of instrumental records, the NAO has strongly influenced inter-annual precipitation variations in the western Mediterranean, while parts of the eastern basin have shown an anti-phase relationship in precipitation and atmospheric pressure. A wide array of proxy-climate data from Iberia and Morocco indicate overall drier conditions during the Medieval Climate Anomaly (MCA) and a generally wetter climate in the Little Ice Age (LIA)(Moreno et al., 2012, Quat. Sci. Rev. 43, 16-32). This pattern is consistent with strong NAO forcing of western Mediterranean climate over the last 1.1 ka (Trouet et al., 2009; Science 324, 78-80). High-resolution palaeolimnological evidence from central Anatolia exhibit an opposite pattern, implying that an east-west climate see-saw operated in the Mediterranean basin during the LIA and MCA (Roberts et al., 2012; Glob. Planet. Change 84-85, 23-34). However, the strongest evidence for higher (lower) winter season precipitation during the MCA (LIA

  11. Installation of superconducting gravimeter in the Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Ikeda, H. [Research Facility Center for Science and Technology Cryogenics Division, University of Tsukuba, Tsukuba, Ibaraki 305-8577 (Japan)]. E-mail: ikeda@bk.tsukuba.ac.jp; Doi, K. [National Institute of Polar Research, Tokyo, Itabashi-ku 1-9-10, Kaga 173-8515 (Japan); Fukuda, Y. [Department of Geophysics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Shibuya, K. [National Institute of Polar Research, Tokyo, Itabashi-ku 1-9-10, Kaga 173-8515 (Japan); Yoshizaki, R. [Research Facility Center for Science and Technology Cryogenics Division, University of Tsukuba, Tsukuba, Ibaraki 305-8577 (Japan)

    2005-10-01

    In February 2003 to January 2004, a new superconducting gravimeter with a cryocooler was installed to replace the former one in Syowa Station on the Antarctica. It has a high sensitivity of one nano-Gal to survey inside the earth in the Global Geodynamics Project (GGP network). A new type of diaphragm was confirmed to well isolate the vibration from refrigerator cold-head and to prevent the solid air contamination perfectly. Real time remote monitoring system from Japan is also established.

  12. The Ice: A Journey to Antarctica

    Science.gov (United States)

    Ford, Arthur B.

    The title is misleading for a non—“OAE” (Old Antarctic Explorer, to whom “The Ice” is Antarctica) because The Ice is about far more than just ice. It does indeed cover just about all you'd want to know (or more) about Antarctic ice, from the vast south polar sheets and glaciers to the great tabular bergs, bergy bits, brash ice, pancake ice, frazil ice, and the pack of the polar seas; but it also explores nearly every aspect of this “Last of Lands” in an unusually comprehensive coverage. From the “Heroic Ages” of early 20th-century explorers Robert Scott, Ernest Shackleton, and Roald Amundsen to the present “Cruise Ship Age,”Antarctica has produced a wealth of literature in the “Journey to…” style — which Pyne's is not. Instead, his product from one short (3-month) visit under a National Endowment for the Humanities fellowship takes all readers o n a webwork journey through time, space, ice, and rocks for an appreciation of “ The Ice” in a way found in no other book. This, his fifth book (another one is Fire in America, Princeton University Press, Princeton, N.J., 1982), is a significant contribution to the literature of Antarctica. Pyne's prose cannot be paraphrased for a review, as the reader will be able to appreciate from the excerpts to follow.

  13. High Resolution Spatial Mapping of Human Footprint across Antarctica and Its Implications for the Strategic Conservation of Avifauna.

    Science.gov (United States)

    Pertierra, Luis R; Hughes, Kevin A; Vega, Greta C; Olalla-Tárraga, Miguel Á

    2017-01-01

    Human footprint models allow visualization of human spatial pressure across the globe. Up until now, Antarctica has been omitted from global footprint models, due possibly to the lack of a permanent human population and poor accessibility to necessary datasets. Yet Antarctic ecosystems face increasing cumulative impacts from the expanding tourism industry and national Antarctic operator activities, the management of which could be improved with footprint assessment tools. Moreover, Antarctic ecosystem dynamics could be modelled to incorporate human drivers. Here we present the first model of estimated human footprint across predominantly ice-free areas of Antarctica. To facilitate integration into global models, the Antarctic model was created using methodologies applied elsewhere with land use, density and accessibility features incorporated. Results showed that human pressure is clustered predominantly in the Antarctic Peninsula, southern Victoria Land and several areas of East Antarctica. To demonstrate the practical application of the footprint model, it was used to investigate the potential threat to Antarctica's avifauna by local human activities. Relative footprint values were recorded for all 204 of Antarctica's Important Bird Areas (IBAs) identified by BirdLife International and the Scientific Committee on Antarctic Research (SCAR). Results indicated that formal protection of avifauna under the Antarctic Treaty System has been unsystematic and is lacking for penguin and flying bird species in some of the IBAs most vulnerable to human activity and impact. More generally, it is hoped that use of this human footprint model may help Antarctic Treaty Consultative Meeting policy makers in their decision making concerning avifauna protection and other issues including cumulative impacts, environmental monitoring, non-native species and terrestrial area protection.

  14. Shifting baselines in Antarctic ecosystems; ecophysiological response to warming in Lissarca miliaris at Signy Island, Antarctica.

    Directory of Open Access Journals (Sweden)

    Adam J Reed

    Full Text Available The Antarctic Peninsula has experienced a rapid increase in atmospheric temperature over the last 50 years. Whether or not marine organisms thriving in this cold stenothermal environment are able to cope with warming is of concern. Here, we present changes to the growth and shell characteristics of the ecologically important, small and short lived brooding bivalve Lissarca miliaris from Signy Island, Antarctica. Using material collected from the 1970's to the present day, we show an increase in growth rate and adult shell deterioration accompanied by a decrease in offspring size, associated with an increase in annual average temperatures. Critical changes to the bivalve's ecology seen today evidence the problem of a shift in baseline since the onset of warming recorded in Antarctica. These small bivalves are demonstrating ecophysiological responses to subtle warming that, provided warming continues, could soon surpass a physiological tipping point, adding to warming associated threats such as increased predatory pressure and ocean acidification.

  15. Shifting baselines in Antarctic ecosystems; ecophysiological response to warming in Lissarca miliaris at Signy Island, Antarctica.

    Science.gov (United States)

    Reed, Adam J; Thatje, Sven; Linse, Katrin

    2012-01-01

    The Antarctic Peninsula has experienced a rapid increase in atmospheric temperature over the last 50 years. Whether or not marine organisms thriving in this cold stenothermal environment are able to cope with warming is of concern. Here, we present changes to the growth and shell characteristics of the ecologically important, small and short lived brooding bivalve Lissarca miliaris from Signy Island, Antarctica. Using material collected from the 1970's to the present day, we show an increase in growth rate and adult shell deterioration accompanied by a decrease in offspring size, associated with an increase in annual average temperatures. Critical changes to the bivalve's ecology seen today evidence the problem of a shift in baseline since the onset of warming recorded in Antarctica. These small bivalves are demonstrating ecophysiological responses to subtle warming that, provided warming continues, could soon surpass a physiological tipping point, adding to warming associated threats such as increased predatory pressure and ocean acidification.

  16. Mineral dust variability in central West Antarctica associated with ozone depletion

    Directory of Open Access Journals (Sweden)

    M. Cataldo

    2013-02-01

    Full Text Available We present here data of mineral dust variability retrieved from an ice core of the central West Antarctic, spanning the last five decades. Main evidence provided by the geochemical analysis is that northerly air mass incursions to the coring site, tracked by insoluble dust microparticles, have declined over the past 50 yr. This result contrasts with dust records from ice cores reported to the coastal West Antarctic that show increases since mid-20th century. We attribute this difference to regional climatic changes due to the ozone depletion and its implications to westerly winds. We found that the diameters of insoluble microparticles in the central West Antarctica ice core are significantly correlated with cyclone depth (energy and wind intensity around Antarctica.

  17. Phylogenetic analyses of the polyprotein coding sequences of serotype O foot-and-mouth disease viruses in East Africa: evidence for interserotypic recombination

    DEFF Research Database (Denmark)

    Balinda, Sheila; Siegismund, Hans; Muwanika, Vincent

    2010-01-01

    Background Foot-and-mouth disease (FMD) is endemic in East Africa with the majority of the reported outbreaks attributed to serotype O virus. In this study, phylogenetic analyses of the polyprotein coding region of serotype O FMD viruses from Kenya and Uganda has been undertaken to infer...... evolutionary relationships and processes responsible for the generation and maintenance of diversity within this serotype. FMD virus RNA was obtained from six samples following virus isolation in cell culture and in one case by direct extraction from an oropharyngeal sample. Following RT-PCR, the single long...... recombinant between serotypes A and O. A bootscan analysis of K/52/1992 with East African FMD serotype A viruses (A21/KEN/1964 and A23/KEN/1965) and serotype O viral isolate (K/117/1999) revealed that the P2 region is probably derived from a serotype A strain while the P3 region appears to be a mosaic derived...

  18. Large-scale population assessment informs conservation management for seabirds in Antarctica and the Southern Ocean: A case study of Adélie penguins

    Directory of Open Access Journals (Sweden)

    Colin Southwell

    2017-01-01

    Full Text Available Antarctica and the Southern Ocean are increasingly affected by fisheries, climate change and human presence. Antarctic seabirds are vulnerable to all these threats because they depend on terrestrial and marine environments to breed and forage. We assess the current distribution and total abundance of Adélie penguins in East Antarctica and find there are 3.5 (95% CI 2.9–4.2 million individuals of breeding age along the East Antarctic coastline and 5.9 (4.2–7.7 million individuals foraging in the adjacent ocean after the breeding season. One third of the breeding population numbering over 1 million individuals breed within 10 km of research stations, highlighting the potential for human activities to impact Adélie penguin populations despite their current high abundance. The 16 Antarctic Specially Protected Areas currently designated in East Antarctica offer protection to breeding populations close to stations in four of six regional populations. The East Antarctic breeding population consumes an average of 193 500 tonnes of krill and 18 800 tonnes of fish during a breeding season, with consumption peaking at the end of the breeding season. These findings can inform future conservation management decisions in the terrestrial environment under the Protocol on Environmental Protection to develop a systematic network of protected areas, and in the marine environment under the Convention for the Conservation of Antarctic Marine Living Resources to allow the consumption needs of Adélie penguins to be taken into account when setting fishery catch limits. Extending this work to other penguin, flying seabird, seal and whale species is a priority for conservation management in Antarctica and the Southern Ocean.

  19. Access to Risk Mitigating Weather Forecasts and Changes in Farming Operations in East and West Africa: Evidence from a Baseline Survey

    Directory of Open Access Journals (Sweden)

    Abayomi Samuel Oyekale

    2015-10-01

    Full Text Available Unfavorable weather currently ranks among the major challenges facing agricultural development in many African countries. Impact mitigation through access to reliable and timely weather forecasts and other adaptive mechanisms are foremost in Africa’s policy dialogues and socio-economic development agendas. This paper analyzed the factors influencing access to forecasts on incidence of pests/diseases (PD and start of rainfall (SR. The data were collected by Climate Change Agriculture and Food Security (CCAFS and analyzed with Probit regression separately for East Africa, West Africa and the combined dataset. The results show that 62.7% and 56.4% of the farmers from East and West Africa had access to forecasts on start of rainfall, respectively. In addition, 39.3% and 49.4% of the farmers from East Africa indicated that forecasts on outbreak of pests/diseases and start of rainfall were respectively accompanied with advice as against 18.2% and 41.9% for West Africa. Having received forecasts on start of rainfall, 24.0% and 17.6% of the farmers from East and West Africa made decisions on timing of farming activities respectively. Probabilities of having access to forecasts on PD significantly increased with access to formal education, farm income and previous exposure to climatic shocks. Furthermore, probabilities of having access to forecasts on SR significantly increased (p < 0.05 with access to business income, radio and perception of more erratic rainfall, among others. It was recommended that promotion of informal education among illiterate farmers would enhance their climatic resilience, among others.

  20. Genetic Evidence for Rift Valley Fever Outbreaks in Madagascar Resulting from Virus Introductions from the East African Mainland rather than Enzootic Maintenance▿†‡

    Science.gov (United States)

    Carroll, Serena A.; Reynes, Jean-Marc; Khristova, Marina L.; Andriamandimby, Soa Fy; Rollin, Pierre E.; Nichol, Stuart T.

    2011-01-01

    Rift Valley fever virus (RVFV), a mosquito-borne phlebovirus, has been detected in Madagascar since 1979, with occasional outbreaks. In 2008 to 2009, a large RVFV outbreak was detected in Malagasy livestock and humans during two successive rainy seasons. To determine whether cases were due to enzootic maintenance of the virus within Madagascar or to importation from the East African mainland, nine RVFV whole genomic sequences were generated for viruses from the 1991 and 2008 Malagasy outbreaks. Bayesian coalescent analyses of available whole S, M, and L segment sequences were used to estimate the time to the most recent common ancestor for the RVFVs. The 1979 Madagascar isolate shared a common ancestor with strains on the mainland around 1972. The 1991 Madagascar isolates were in a clade distinct from that of the 1979 isolate and shared a common ancestor around 1987. Finally, the 2008 Madagascar viruses were embedded within a large clade of RVFVs from the 2006–2007 outbreak in East Africa and shared a common ancestor around 2003 to 2004. These results suggest that the most recent Madagascar outbreak was caused by a virus likely arriving in the country some time between 2003 and 2008 and that this outbreak may be an extension of the 2006–2007 East African outbreak. Clustering of the Malagasy sequences into subclades indicates that the viruses have continued to evolve during their short-term circulation within the country. These data are consistent with the notion that RVFV outbreaks in Madagascar result not from emergence from enzootic cycles within the country but from recurrent virus introductions from the East African mainland. PMID:21507967

  1. Managing Human Activities in Antarctica : Should Wilderness Protection Count?

    NARCIS (Netherlands)

    Bastmeijer, C.J.

    2005-01-01

    Antarctica is often described as one of the world's last wildernesses. In harmony with this general perception, the wilderness values of Antarctica received legal status with the adoption of the Protocol on Environmental Protection to the Antarctic Treaty. Article 3(1) of the Protocol obliges each

  2. The genus Bryoerythrophyllum (Musci, Pottiaceae in Antarctica

    Directory of Open Access Journals (Sweden)

    Sollman Philip

    2015-07-01

    Full Text Available Antarctic material of the genus Bryoerythrophyllum P. C. Chen was studied from all specimens present in KRAM. Bryoerythrophyllum recurvirostrum (Hedw. P. C. Chen var. antarcticum L. I. Savicz & Smirnova is treated as a distinct species: B. antarcticum (L. I. Savicz & Smirnova P. Sollman, stat. nov. Three species are now known in the Antarctic region: B. antarcticum, B. recurvirostrum and B. rubrum (Jur. ex Geh. P. C. Chen. Bryoerythrophyllum rubrum is reported for the first time from the Antarctic. It is a bipolar species. A key to the taxa is given. These species are described and briefly discussed, with notes on illustrations, reproduction, habitat, world range, distribution and elevation in Antarctica.

  3. East Africa

    Science.gov (United States)

    2002-01-01

    This image shows the East African nations of Ethiopia, Eritrea, and Somalia, as well as portions of Kenya, Sudan, Yemen, and Saudi Arabia. Dominating the scene are the green Ethiopian Highlands. With altitudes as high as 4,620 meters (15,157 feet), the highlands pull moisture from the arid air, resulting in relatively lush vegetation. In fact, coffee-one of the world's most prized crops-originated here. To the north (above) the highlands is Eritrea, which became independent in 1993. East (right) of Ethiopia is Somalia, jutting out into the Indian Ocean. The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) captured this true-color image on November 29, 2000. Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  4. Building capacity for evidence generation, synthesis and implementation to improve the care of mothers and babies in South East Asia: methods and design of the SEA-ORCHID Project using a logical framework approach.

    Science.gov (United States)

    McDonald, Steve; Turner, Tari; Chamberlain, Catherine; Lumbiganon, Pisake; Thinkhamrop, Jadsada; Festin, Mario R; Ho, Jacqueline J; Mohammad, Hakimi; Henderson-Smart, David J; Short, Jacki; Crowther, Caroline A; Martis, Ruth; Green, Sally

    2010-07-01

    Rates of maternal and perinatal mortality remain high in developing countries despite the existence of effective interventions. Efforts to strengthen evidence-based approaches to improve health in these settings are partly hindered by restricted access to the best available evidence, limited training in evidence-based practice and concerns about the relevance of existing evidence. South East Asia--Optimising Reproductive and Child Health in Developing Countries (SEA-ORCHID) was a five-year project that aimed to determine whether a multifaceted intervention designed to strengthen the capacity for research synthesis, evidence-based care and knowledge implementation improved clinical practice and led to better health outcomes for mothers and babies. This paper describes the development and design of the SEA-ORCHID intervention plan using a logical framework approach. SEA-ORCHID used a before-and-after design to evaluate the impact of a multifaceted tailored intervention at nine sites across Thailand, Malaysia, Philippines and Indonesia, supported by three centres in Australia. We used a logical framework approach to systematically prepare and summarise the project plan in a clear and logical way. The development and design of the SEA-ORCHID project was based around the three components of a logical framework (problem analysis, project plan and evaluation strategy). The SEA-ORCHID logical framework defined the project's goal and purpose (To improve the health of mothers and babies in South East Asia and To improve clinical practice in reproductive health in South East Asia), and outlined a series of project objectives and activities designed to achieve these. The logical framework also established outcome and process measures appropriate to each level of the project plan, and guided project work in each of the participating countries and hospitals. Development of a logical framework in the SEA-ORCHID project enabled a reasoned, logical approach to the project design

  5. Building capacity for evidence generation, synthesis and implementation to improve the care of mothers and babies in South East Asia: methods and design of the SEA-ORCHID Project using a logical framework approach

    Directory of Open Access Journals (Sweden)

    Short Jacki

    2010-07-01

    Full Text Available Abstract Background Rates of maternal and perinatal mortality remain high in developing countries despite the existence of effective interventions. Efforts to strengthen evidence-based approaches to improve health in these settings are partly hindered by restricted access to the best available evidence, limited training in evidence-based practice and concerns about the relevance of existing evidence. South East Asia - Optimising Reproductive and Child Health in Developing Countries (SEA-ORCHID was a five-year project that aimed to determine whether a multifaceted intervention designed to strengthen the capacity for research synthesis, evidence-based care and knowledge implementation improved clinical practice and led to better health outcomes for mothers and babies. This paper describes the development and design of the SEA-ORCHID intervention plan using a logical framework approach. Methods SEA-ORCHID used a before-and-after design to evaluate the impact of a multifaceted tailored intervention at nine sites across Thailand, Malaysia, Philippines and Indonesia, supported by three centres in Australia. We used a logical framework approach to systematically prepare and summarise the project plan in a clear and logical way. The development and design of the SEA-ORCHID project was based around the three components of a logical framework (problem analysis, project plan and evaluation strategy. Results The SEA-ORCHID logical framework defined the project's goal and purpose (To improve the health of mothers and babies in South East Asia and To improve clinical practice in reproductive health in South East Asia, and outlined a series of project objectives and activities designed to achieve these. The logical framework also established outcome and process measures appropriate to each level of the project plan, and guided project work in each of the participating countries and hospitals. Conclusions Development of a logical framework in the SEA

  6. Detecting high spatial variability of ice shelf basal mass balance, Roi Baudouin Ice Shelf, Antarctica

    Directory of Open Access Journals (Sweden)

    S. Berger

    2017-11-01

    Full Text Available Ice shelves control the dynamic mass loss of ice sheets through buttressing and their integrity depends on the spatial variability of their basal mass balance (BMB, i.e. the difference between refreezing and melting. Here, we present an improved technique – based on satellite observations – to capture the small-scale variability in the BMB of ice shelves. As a case study, we apply the methodology to the Roi Baudouin Ice Shelf, Dronning Maud Land, East Antarctica, and derive its yearly averaged BMB at 10 m horizontal gridding. We use mass conservation in a Lagrangian framework based on high-resolution surface velocities, atmospheric-model surface mass balance and hydrostatic ice-thickness fields (derived from TanDEM-X surface elevation. Spatial derivatives are implemented using the total-variation differentiation, which preserves abrupt changes in flow velocities and their spatial gradients. Such changes may reflect a dynamic response to localized basal melting and should be included in the mass budget. Our BMB field exhibits much spatial detail and ranges from −14.7 to 8.6 m a−1 ice equivalent. Highest melt rates are found close to the grounding line where the pressure melting point is high, and the ice shelf slope is steep. The BMB field agrees well with on-site measurements from phase-sensitive radar, although independent radar profiling indicates unresolved spatial variations in firn density. We show that an elliptical surface depression (10 m deep and with an extent of 0.7 km × 1.3 km lowers by 0.5 to 1.4 m a−1, which we tentatively attribute to a transient adaptation to hydrostatic equilibrium. We find evidence for elevated melting beneath ice shelf channels (with melting being concentrated on the channel's flanks. However, farther downstream from the grounding line, the majority of ice shelf channels advect passively (i.e. no melting nor refreezing toward the ice shelf front. Although the absolute, satellite

  7. Detecting high spatial variability of ice shelf basal mass balance, Roi Baudouin Ice Shelf, Antarctica

    Science.gov (United States)

    Berger, Sophie; Drews, Reinhard; Helm, Veit; Sun, Sainan; Pattyn, Frank

    2017-11-01

    Ice shelves control the dynamic mass loss of ice sheets through buttressing and their integrity depends on the spatial variability of their basal mass balance (BMB), i.e. the difference between refreezing and melting. Here, we present an improved technique - based on satellite observations - to capture the small-scale variability in the BMB of ice shelves. As a case study, we apply the methodology to the Roi Baudouin Ice Shelf, Dronning Maud Land, East Antarctica, and derive its yearly averaged BMB at 10 m horizontal gridding. We use mass conservation in a Lagrangian framework based on high-resolution surface velocities, atmospheric-model surface mass balance and hydrostatic ice-thickness fields (derived from TanDEM-X surface elevation). Spatial derivatives are implemented using the total-variation differentiation, which preserves abrupt changes in flow velocities and their spatial gradients. Such changes may reflect a dynamic response to localized basal melting and should be included in the mass budget. Our BMB field exhibits much spatial detail and ranges from -14.7 to 8.6 m a-1 ice equivalent. Highest melt rates are found close to the grounding line where the pressure melting point is high, and the ice shelf slope is steep. The BMB field agrees well with on-site measurements from phase-sensitive radar, although independent radar profiling indicates unresolved spatial variations in firn density. We show that an elliptical surface depression (10 m deep and with an extent of 0.7 km × 1.3 km) lowers by 0.5 to 1.4 m a-1, which we tentatively attribute to a transient adaptation to hydrostatic equilibrium. We find evidence for elevated melting beneath ice shelf channels (with melting being concentrated on the channel's flanks). However, farther downstream from the grounding line, the majority of ice shelf channels advect passively (i.e. no melting nor refreezing) toward the ice shelf front. Although the absolute, satellite-based BMB values remain uncertain, we have

  8. Recent Studies on the increase in Seismicity in the Antarctic Plate: Observations from BB Seismological Observatory (MAIT) at Maitri, Antarctica

    Science.gov (United States)

    N, R.; Ec, M.

    2008-12-01

    The permanent Seismological Observatory was established in 1997 at Maitri in Central Dronning Maud Land, East Antarctica (70 °45' South 11 °43' East) primarily to monitor the seismicity in and around Antarctica, the space and time distribution of earthquake occurrences and obtain hypocentral parameters, magnitudes of earthquakes, velocity inversion for underground structure and earthquake source mechanism. The observatory has been upgraded during 25th Indian Silver Jubilee Scientific Expedition to Antarctica (December 2005 to February 2007) and 26th Indian Antarctic Expedition (IAE) with the new generation Geotech KS-2000M Seismometer and Smart 24R digitizer. During the 27th IAE the Seismic Observatory was further upgraded by adding Reftek 130 seismic system. Uninterrupted good quality digital Broad Band Seismic data is continuously being acquired. The SEISAN 8.1 software was used for final processing and analysis of about 300 earthquakes recorded. During the year 2006 the tele-seismic events, and quite a number of regional earthquakes of the order of 4 to 6.0 magnitude within Antarctic Plate, 23 in South Sandwich Islands, 7 in Scotia Sea, 2 in Macqurie Islands and 23 in Mid Oceanic Ridges in the Indian Ocean were recorded. 48 earthquakes of the magnitude above 4.5 from the nearby South Indian Ocean, South of South Africa, Chile, Argentina, Bolivia and about 40 earthquakes of the magnitude above 5.0 from the Indonesian Region were analysed. An earthquake of magnitude Ms=7.3 from the seismically active region of South Sandwich Islands Δ =16.5 °, Mb=7.8 earthquake from Tonga Islands and Mb=7.2 earthquake from Java were the large earthquakes that were recorded. Along with this the MOHO depth beneath MAIT was also estimated to be about 40km using receiver function analysis. All the analysed monthly data was reported to the I.S.C., U.K.,Global Data Centre for the final processing and inclusion in the yearly ISC Seismic Bulletin. The increasing seismic activity in

  9. Diversity of bacterial communities in the lakes of Schirmacher Oasis, Antarctica

    Science.gov (United States)

    Mojib, Nazia; Huang, Jonathan; Hoover, Richard B.; Pikuta, Elena V.; Storrie-Lombardi, Michael; Sattler, Birgit; Andersen, Dale; Bej, Asim K.

    2009-08-01

    Extreme conditions such as low temperature, aridness, low availability of organic matter, high salinity and UV-radiation in terrestrial Antarctica are key factors limiting the habitation of biotic communities and ecosystem dynamics. In recent studies, it has been discovered that the bacterial communities are highly diverse and distributed widely in the extreme ecosystem of Antarctica. Besides available morphometric data, geology, and thermal profile, limited study on the microbial identification, phylogenetic analysis, diversity and distribution of microorganisms in different lakes of Schirmacher Oasis in East Antarctica has been reported. The objective of this study was to assess the microbial biodiversity and distribution using culture-independent and culture-dependent methodologies based upon bacterial 16S rRNA gene analysis in three categories of lakes, i.e., the land-locked (L), epi-shelf (E), and pro-glacial (P) lakes in Schirmacher Oasis. The water and ice samples were collected during the 2008 Tawani International Scientific Expedition. Direct culturing of the samples on R2A agar media exhibited a wide variety of pigmented bacteria. Two of the pigmented bacteria that were cultured belong to the genera, Hymenobacter, and Flavobacterium. Cultureindependent methodology of one of the land-locked lakes L27C identified a rich microbial diversity consisting of six different phyla of bacteria. The majority of bacteria (56%) belong to the Class γ-proteobacteria within the phylum Proteobacteria. Within the Class γ-proteobacteria, Acinetobacter dominated (48%) the total microbial load. Characterization of the microbial diversity within the three different types of Antarctic lakes is important because it will help give us a better understanding of the survival mechanisms and the functionality of these bacteria in extremely cold and harsh Antarctic ecosystems.

  10. A robust bioassay to assess the toxicity of metals to the Antarctic marine microalga Phaeocystis antarctica.

    Science.gov (United States)

    Gissi, Francesca; Adams, Merrin S; King, Catherine K; Jolley, Dianne F

    2015-07-01

    Despite evidence of contamination in Antarctic coastal marine environments, no water-quality guidelines have been established for the region because of a paucity of biological effects data for local Antarctic species. Currently, there is limited information on the sensitivity of Antarctic microalgae to metal contamination, which is exacerbated by the lack of standard toxicity testing protocols for local marine species. In the present study, a routine and robust toxicity test protocol was developed using the Antarctic marine microalga Phaeocystis antarctica, and its sensitivity was investigated following 10-d exposures to dissolved copper, cadmium, lead, zinc, and nickel. In comparisons of 10% inhibition of population growth rate (IC10) values, P. antarctica was most sensitive to copper (3.3 μg/L), followed by cadmium (135 μg/L), lead (260 μg/L), and zinc (450 μg/L). Although an IC10 value for nickel could not be accurately estimated, the no-observed-effect concentration value for nickel was 1070 μg/L. Exposure to copper and cadmium caused changes in internal cell granularity and increased chlorophyll a fluorescence. Lead, zinc, and nickel had no effect on any of the cellular parameters measured. The present study provides valuable metal-ecotoxicity data for an Antarctic marine microalga, with P. antarctica representing one of the most sensitive microalgal species to dissolved copper ever reported when compared with temperate and tropical species. © 2015 SETAC.

  11. The Landsat Image Mosaic of Antarctica

    Science.gov (United States)

    Bindschadler, R.; Vornberger, P.; Fleming, A.; Fox, A.; Mullins, J.; Binnie, D.; Paulsen, S.J.; Granneman, B.; Gorodetzky, D.

    2008-01-01

    The Landsat Image Mosaic of Antarctica (LIMA) is the first true-color, high-spatial-resolution image of the seventh continent. It is constructed from nearly 1100 individually selected Landsat-7 ETM+ scenes. Each image was orthorectified and adjusted for geometric, sensor and illumination variations to a standardized, almost seamless surface reflectance product. Mosaicing to avoid clouds produced a high quality, nearly cloud-free benchmark data set of Antarctica for the International Polar Year from images collected primarily during 1999-2003. Multiple color composites and enhancements were generated to illustrate additional characteristics of the multispectral data including: the true appearance of the surface; discrimination between snow and bare ice; reflectance variations within bright snow; recovered reflectance values in regions of sensor saturation; and subtle topographic variations associated with ice flow. LIMA is viewable and individual scenes or user defined portions of the mosaic are downloadable at http://lima.usgs.gov. Educational materials associated with LIMA are available at http://lima.nasa.gov.

  12. Is there 1.5-million-year-old ice near Dome C, Antarctica?

    Science.gov (United States)

    Parrenin, Frédéric; Cavitte, Marie G. P.; Blankenship, Donald D.; Chappellaz, Jérôme; Fischer, Hubertus; Gagliardini, Olivier; Masson-Delmotte, Valérie; Passalacqua, Olivier; Ritz, Catherine; Roberts, Jason; Siegert, Martin J.; Young, Duncan A.

    2017-11-01

    Ice sheets provide exceptional archives of past changes in polar climate, regional environment and global atmospheric composition. The oldest dated deep ice core drilled in Antarctica has been retrieved at EPICA Dome C (EDC), reaching ˜ 800 000 years. Obtaining an older paleoclimatic record from Antarctica is one of the greatest challenges of the ice core community. Here, we use internal isochrones, identified from airborne radar coupled to ice-flow modelling to estimate the age of basal ice along transects in the Dome C area. Three glaciological properties are inferred from isochrones: surface accumulation rate, geothermal flux and the exponent of the Lliboutry velocity profile. We find that old ice (> 1.5 Myr, 1.5 million years) likely exists in two regions: one ˜ 40 km south-west of Dome C along the ice divide to Vostok, close to a secondary dome that we name Little Dome C (LDC), and a second region named North Patch (NP) located 10-30 km north-east of Dome C, in a region where the geothermal flux is apparently relatively low. Our work demonstrates the value of combining radar observations with ice flow modelling to accurately represent the true nature of ice flow, and understand the formation of ice-sheet architecture, in the centre of large ice sheets.

  13. Is there 1.5-million-year-old ice near Dome C, Antarctica?

    Directory of Open Access Journals (Sweden)

    F. Parrenin

    2017-11-01

    Full Text Available Ice sheets provide exceptional archives of past changes in polar climate, regional environment and global atmospheric composition. The oldest dated deep ice core drilled in Antarctica has been retrieved at EPICA Dome C (EDC, reaching ∼ 800 000 years. Obtaining an older paleoclimatic record from Antarctica is one of the greatest challenges of the ice core community. Here, we use internal isochrones, identified from airborne radar coupled to ice-flow modelling to estimate the age of basal ice along transects in the Dome C area. Three glaciological properties are inferred from isochrones: surface accumulation rate, geothermal flux and the exponent of the Lliboutry velocity profile. We find that old ice (> 1.5 Myr, 1.5 million years likely exists in two regions: one ∼ 40 km south-west of Dome C along the ice divide to Vostok, close to a secondary dome that we name Little Dome C (LDC, and a second region named North Patch (NP located 10–30 km north-east of Dome C, in a region where the geothermal flux is apparently relatively low. Our work demonstrates the value of combining radar observations with ice flow modelling to accurately represent the true nature of ice flow, and understand the formation of ice-sheet architecture, in the centre of large ice sheets.

  14. Tectonic Evolution of Mozambique Ridge in East African continental margin

    Science.gov (United States)

    Tang, Yong

    2017-04-01

    Tectonic Evolution of Mozambique Ridge in East African continental margin Yong Tang He Li ES.Mahanjane Second Institute of Oceanography,SOA,Hangzhou The East Africa passive continental margin is a depression area, with widely distributed sedimentary wedges from southern Mozambique to northern Somali (>6500km in length, and about 6km in thickness). It was resulted from the separation of East Gondwana, and was developed by three stages: (1) rifting in Early-Middle Jurassic; (2) spreading from Late Jurassic to Early Cretaceous; (3) drifting since the Cretaceous period. Tectonic evolution of the Mozambique continental margin is distinguished by two main settings separated by a fossil transform, the Davie Fracture Zone; (i) rifting and transform setting in the northern margin related to opening of the Somali and Rovuma basins, and (ii) rifting and volcanism setting during the opening of the Mozambique basin in the southern margin. 2D reflection seismic investigation of the crustal structure in the Zambezi Delta Depression, provided key piece of evidence for two rifting phases between Africa and Antarctica. The magma-rich Rift I phase evolved from rift-rift-rift style with remarkable emplacement of dyke swarms (between 182 and 170 Ma). Related onshore outcrops are extensively studied, the Karoo volcanics in Mozambique, Zimbabwe and South Africa, all part of the Karoo "triple-junction". These igneous bodies flow and thicken eastwards and are now covered by up to 5 km of Cretaceous and Tertiary sediments and recorded by seismic and oil exploration wells. Geophysical and geological data recorded during oceanographic cruises provide very controversial results regarding the nature of the Mozambique Ridge. Two conflicting opinions remains open, since the early expeditions to the Indian Ocean, postulating that its character is either magmatic (oceanic) or continental origin. We have carried out an China-Mozambique Joint Cruise(CMJC) on southern Mozambique Basin on 1st June to

  15. Antioxidant Responses Induced by UVB Radiation in Deschampsia antarctica Desv.

    OpenAIRE

    K?hler, Hans; Contreras, Rodrigo A.; Pizarro, Marisol; Cort?s-Ant?quera, Rodrigo; Z??iga, Gustavo E.

    2017-01-01

    Deschampsia antarctica Desv. is one of two vascular plants that live in the Maritime Antarctic Territory and is exposed to high levels of ultraviolet-B (UVB) radiation. In this work, antioxidant physiology of D. antarctica was studied in response to UVB induced oxidative changes. Samples were collected from Antarctica and maintained in vitro culture during 2 years. Plants were sub-cultured in a hydroponic system and exposed to 21.4 kJ m-2 day-1, emulating summer Antarctic conditions. Results ...

  16. Evidence for genetic association between East Asian and western North American Crataegus L. (Rosaceae) and rapid divergence of the eastern North American lineages based on multiple DNA sequences.

    Science.gov (United States)

    Lo, Eugenia Y Y; Stefanović, Sasa; Christensen, Knud Ib; Dickinson, Timothy A

    2009-05-01

    Phylogeographic relationships were constructed for 72 Old and New World Crataegus species using combinations of four chloroplast and up to five nuclear regions. Maximum parsimony, maximum likelihood, and Bayesian results yield consistent relationships among major lineages. The close associations of the East Asian and western North American species point toward ancient trans-Beringian migrations. Relationships among eastern North American species are poorly resolved and few groups are identified that are congruent with existing classifications. Scant variation and short internal branches among these species suggest rapid divergence associated with polyploidy and hybridization. Incongruence between the chloroplast and nuclear data, and morphology suggest hybrid origins of three species from an extinct European lineage (the male parent) and three different North American female parents. Europe and eastern North America are suggested as the most recent common areas for Crataegus; at least four dispersal events are inferred to explain the present distribution of the genus.

  17. Impacts of permafrost degradation on a stream in Taylor Valley, Antarctica

    Science.gov (United States)

    Sudman, Zachary; Gooseff, Michael N.; Fountain, Andrew G.; Levy, Joseph S.; Obryk, Maciej K.; Van Horn, David

    2017-05-01

    The McMurdo Dry Valleys (MDV) of Antarctica are an ice-free landscape that supports a complex, microbially dominated ecosystem despite a severely arid, cold environment (region is nearing a threshold of rapid landscape change. In 2012, substantial thermokarst development was observed along several kilometers of the west branch of Crescent Stream in Taylor Valley mostly in the form of bank failures, whereas the adjacent east branch was unaffected. The objective of this study was to quantify the changes to the stream banks of the west branch of Crescent Stream and to determine the impacts on the composition of the stream bed material. Three annually repeated terrestrial LiDAR scans were compared to determine the rates of ground surface change caused by thermokarst formation on the stream bank. The areal extent of the thermokarst was shown to be decreasing; however, the average vertical rate of retreat remained constant. Field measurements of bed materials indicated that the west branch and the reach downstream of the confluence (of east and west branches) consistently contained more fines than the unaffected east branch. This suggests that the finer bed material is a result of the thermokarst development on the west branch. These finer bed material compositions are likely to increase the mobility of the bed material, which will have implications for stream morphology, stream algal mat communities, and downstream aquatic ecosystems.

  18. The reflectance of rough snow surfaces in Antarctica from POLDER/ADEOS remote sensing data

    Science.gov (United States)

    Mondet, Jean; Fily, Michel

    The POLDER (POLarization and Directionality of the Earth's Reflectances) sensor was launched onboard the Japanese ADEOS satellite in August 1996. It measured the energy reflected by the Earth in the solar spectrum at 8 wavelengths. From this sensor, an Earth target could be seen up to 14 times along a single path providing a good characterization of the BRDF (Bidirectional Reflectance Distribution Function) from space. A set of one month of POLDER data over east Antarctica was analyzed. After cloud masking and atmospheric corrections, mean BRDFs were derived for different areas. In some parts of the ice sheet the BRDF is assymetric with a strong reflectance peak in the half space oriented towards the sun (backscatter). This peak is due to the anisotropic roughness of the surface (sastrugi) and its position depends on the sastrugi direction.

  19. Molecular variation of antarctic grass Deschampsia antarctica Desv. from King George Island (Antarctica

    Directory of Open Access Journals (Sweden)

    Katarzyna J. Chwedorzewska

    2011-01-01

    Full Text Available Deschampsia antarctica Desv. plants collected on King George Islands (Antarctica at two localities that differ in topographic and nutrition conditions exhibited morphological variation that differentiated plants of both locations. The molecular variation characteristic to individuals of both sites was tested using AFLP approach in order to verify whether morphological variation characteristic to the plants resulted from environmental factors or possibly from differences at the DNA level. Four primer pair combinations were used to generate 339 AFLP fragments, 132 of which were polymorphic and allowed evaluation of genetic relationships among D. antarctica individuals. Chi-square test revealed that only 12 signals were discriminative for the plants from both locations. Cluster analysis conducted on these AFLP fragments demonstrated that plants from the location rich in biogenes were more polymorphic than those from poor one. Our data suggest that the phenotypic variation specific to plants of both locations seem to be the result of adaptation to the environmental conditions like soil and moisture rather than reflect genetic differences.

  20. Rift processes and crustal structure of the Amundsen Sea Embayment, West Antarctica, from 3D potential field modelling

    Science.gov (United States)

    Kalberg, Thomas; Gohl, Karsten; Eagles, Graeme; Spiegel, Cornelia

    2015-12-01

    The Amundsen Sea Embayment of West Antarctica is of particular interest as it provides critical geological boundary conditions in better understanding the dynamic behavior of the West Antarctic Ice Sheet, which is undergoing rapid ice loss in the Amundsen Sea sector. One of the highly debated hypothesis is whether this region has been affected by the West Antarctic Rift System, which is one of the largest in the world and the dominating tectonic feature in West Antarctica. Previous geophysical studies suggested an eastward continuation of this rift system into the Amundsen Sea Embayment. This geophysical study of the Amundsen Sea Embayment presents a compilation of data collected during two RV Polarstern expeditions in the Amundsen Sea Embayment of West Antarctica in 2006 and 2010. Bathymetry and satellite-derived gravity data of the Amundsen Sea Embayment complete the dataset. Our 3-D gravity and magnetic models of the lithospheric architecture and development of this Pacific margin improve previous interpretations from 2-D models of the region. The crust-mantle boundary beneath the continental rise and shelf is between 14 and 29 km deep. The imaged basement structure can be related to rift basins within the Amundsen Sea Embayment, some of which can be interpreted as products of the Cretaceous rift and break-up phase and some as products of later propagation of the West Antarctic Rift System into the region. An estimate of the flexural rigidity of the lithosphere reveals a thin elastic thickness in the eastern embayment which increases towards the west. The results are comparable to estimates in other rift systems such as the Basin and Range province or the East African Rift. Based on these results, we infer an arm of the West Antarctic Rift System is superposed on a distributed Cretaceous rift province in the Amundsen Sea Embayment. Finally, the embayment was affected by magmatism from discrete sources along the Pacific margin of West Antarctica in the Cenozoic.

  1. Climate Proxies: An Inquiry-Based Approach to Discovering Climate Change on Antarctica

    Science.gov (United States)

    Wishart, D. N.

    2016-12-01

    An attractive way to advance climate literacy in higher education is to emphasize its relevance while teaching climate change across the curriculum to science majors and non-science majors. An inquiry-based pedagogical approach was used to engage five groups of students on a "Polar Discovery Project" aimed at interpreting the paleoclimate history of ice cores from Antarctica. Learning objectives and student learning outcomes were clearly defined. Students were assigned several exercises ranging from examination of Antarctic topography to the application of physical and chemical measurements as proxies for climate change. Required materials included base and topographic maps of Antarctica; graph sheets for construction of topographic cross-sectional profiles from profile lines of the Western Antarctica Ice Sheet (WAIS) Divide and East Antarctica; high-resolution photographs of Antarctic ice cores; stratigraphic columns of ice cores; borehole and glaciochemical data (i.e. anions, actions, δ18O, δD etc.); and isotope data on greenhouse gases (CH4, O2, N2) extracted from gas bubbles in ice cores. The methodology was to engage students in (2) construction of topographic profiles; (2) suggest directions for ice flow based on simple physics; (3) formulate decisions on suitable locations for drilling ice cores; (4) visual ice stratigraphy including ice layer counting; (5) observation of any insoluble particles (i.e. meteoritic and volcanic material); (6) analysis of borehole temperature profiles; and (7) the interpretation of several datasets to derive a paleoclimate history of these areas of the continent. The overall goal of the project was to improve the students analytical and quantitative skills; their ability to evaluate relationships between physical and chemical properties in ice cores, and to advance the understanding the impending consequences of climate change while engaging science, technology, engineering and mathematics (STEM). Student learning outcomes

  2. Iceberg Harmonic Tremor, Seismometer Data, Antarctica, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — Seismometers were placed on a 25 km by 50 km iceberg called C16 in the Ross Sea, Antarctica, to identify the Iceberg harmonic Tremor (IHT) source mechanism and to...

  3. RAMP AMM-1 SAR Image Mosaic of Antarctica

    Data.gov (United States)

    National Aeronautics and Space Administration — In 1997, the Canadian RADARSAT-1 satellite was rotated in orbit so that its Synthetic Aperture Radar (SAR) antenna looked south towards Antarctica. This permitted...

  4. Alkanes in Firn Air Samples, Antarctica and Greenland, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains ethane, propane, and n-butane measurements in firn air from the South Pole and the West Antarctic Ice Sheet (WAIS) Divide in Antarctica, and...

  5. The Twelfth Indian Scientific Expedition to Antarctica: Events and achievements

    Digital Repository Service at National Institute of Oceanography (India)

    Dhargalkar, V.K.

    The twelfth Indian Scientific Expedition to Antarctica comprising 56 members coming from different scientific organisations/institutions and the logistic contingent from three wings of defense services was flagged off by Shri Ravi Naik, Honourable...

  6. Eocene squalomorph sharks (Chondrichthyes, Elasmobranchii) from Antarctica

    Science.gov (United States)

    Engelbrecht, Andrea; Mörs, Thomas; Reguero, Marcelo A.; Kriwet, Jürgen

    2017-10-01

    Rare remains of predominantly deep-water sharks of the families Hexanchidae, Squalidae, Dalatiidae, Centrophoridae, and Squatinidae are described from the Eocene La Meseta Formation, Seymour Island, Antarctic Peninsula, which has yielded the most abundant chondrichthyan assemblage from the Southern Hemisphere to date. Previously described representatives of Hexanchus sp., Squalus weltoni, Squalus woodburnei, Centrophorus sp., and Squatina sp. are confirmed and dental variations are documented. Although the teeth of Squatina sp. differ from other Palaeogene squatinid species, we refrain from introducing a new species. A new dalatiid taxon, Eodalatias austrinalis gen. et sp. nov. is described. This new material not only increases the diversity of Eocene Antarctic elasmobranchs but also allows assuming that favourable deep-water habitats were available in the Eocene Antarctic Ocean off Antarctica in the Eocene. The occurrences of deep-water inhabitants in shallow, near-coastal waters of the Antarctic Peninsula agrees well with extant distribution patterns.

  7. [Microbiological studies of the Wanda Lake (Antarctica)].

    Science.gov (United States)

    Kriss, A E; Mitskevich, I N; Rozanova, E P; Osnitskaia, L K

    1976-01-01

    The deep-water (68 m) Wanda Lake in the Antarctica is noticeable by three characteristics: a relatively high temperature in the bottom layer, elevated salinity, and the presence of H2S. Only several (less often, dozens) saprophytic microorganisms per 40 ml of water are encountered in the lake. The total number of bacteria varies from 6-10(3) to 172-10(3) cells/ml. The highest content of the total bacterial population, and saprophytes, is found in intermediate layers, 30 and 40-50 m deep, respectively. Microbial strains isolated from water and ooze belong to the genera Pseudomonas, Chromobacterium, Bacillus, and Mycobacterium. Yeast organisms were also found. Sulphate reducing bacteria were detected only at one station in ooze of the lake while thionic bacteria could not be determined at all. Photosynthetic bacteria were isolated from ooze at all four stations.

  8. Cyanobacteria in Antarctica: ecology, physiology and cold adaptation.

    Science.gov (United States)

    Pandey, K D; Shukla, S P; Shukla, P N; Giri, D D; Singh, J S; Singh, P; Kashyap, A K

    2004-07-01

    Cyanobacterial species composition of fresh water and terrestrial ecosystems and chemical environment of water in Schirmacher Oasis in Continental Antarctica was investigated. Over 35 species of cyanobacteria were recorded. Diazotrophic species both heterocystous and unicellular contributed more than half to the count except in lake ecosystem. The species composition varied among the fresh water as well as terrestrial ecosystems. The physico-chemical analyses of water revealed its poor nurient content which might have supported the growth of diazotrophic cyanobacteria in an Antarctic environment. Among the cyanobacteria Oscillatoria, Phormidium and Nostoc commune were the dominant flora in most of the habitats. The physiological characteristics of isolated cyanobacteria strains indicated that N2-fixation, nitrate uptake, nitrate-reduction, ammonium-uptake, GS-transferase activity and photosynthesis was unaffected at low temperature (5 degrees C) which indicated low temperature adaptation for Antarctic cyanobacteria. This phenomenon was not evident in different strains of tropical origin. The temperature optima for N2-fixation for the different Antarctic cyanobacterial strains was in the range of 15-25 degrees C, nearly 10 degrees C lower than their respective reference strains of tropical origin. Similar results were obtained for cyanobacteria-moss association. The low endergonic activation energy exhibited by the above metabolic activities supported the view that cyanobacteria were adapted to Antarctic ecosystem.

  9. Vapor transport and sublimation on Mullins Glacier, Antarctica

    Science.gov (United States)

    Lamp, J. L.; Marchant, D. R.

    2017-05-01

    We utilize an environmental chamber capable of recreating the extreme polar conditions of the McMurdo Dry Valleys (MDV) of Antarctica to investigate the sublimation rate of the Mullins Valley debris-covered glacier (hereafter Mullins Glacier), reportedly one of the oldest debris-covered alpine glaciers in the world. We measure ice loss via sublimation beneath sediment thicknesses ranging from 0 to 69 mm; from this, we determine an effective diffusivity for Fickian vapor transport through Mullins till of (5.2 ± 0.3) ×10-6 m2s-1 at -10 °C. We use this value, coupled with micrometeorological data from Mullins Valley (atmospheric temperature, relative humidity, and soil temperature) to model the sublimation rate of buried glacier ice near the terminus of Mullins Glacier, where the overlying till thickness approaches 70 cm. We find that the ice-lowering rate during the modeled year (2011) was 0.066 mm under 70 cm of till, a value which is in line with previous estimates for exceedingly slow rates of ice sublimation. These results provide further evidence supporting the probable antiquity of Mullins Glacier ice and overall landscape stability in upland regions of the MDV.

  10. Note On The Ross Sea Shelf Water Downflow Processes (antarctica)

    Science.gov (United States)

    Bergamasco, A.; Defendi, V.; Spezie, G.; Budillon, G.; Carniel, S.

    In the framework of the CLIMA Project of the Italian National Program for Research in Antarctica, three different experimental data sets were acquired along the continental shelf break; two of them (in 1997 and 2001) close to Cape Adare, the 1998 one in the middle of the Ross Sea (i.e. 75 S, 177 W). The investigations were chosen in order to explore the downslope flow of the bottom waters produced in the Ross Sea, namely the High Salinity Shelf Water (HSSW, the densest water mass of the southern ocean coming from its formation site in the polynya region in Terra Nova bay), and the Ice Shelf Water (ISW, originated below the Ross Ice Shelf and outflowing northward). Both bottom waters spill over the shelf edge and mix with the Circumpolar Deep Water (CDW) contributing to the formation of the Antarctic Bottom Waters (AABW). Interpreting temperature, salinity and density maps in terms of cascading processes, both HSSW and ISW overflows are evidenced during, respectively, 1997 and 1998. During the 2001 acquisition there is no presence of HSSW along the shelf break, nevertheless distribution captures the evidence of a downslope flow process.

  11. Caloplaca coeruleofrigida sp. nova, a species from continental Antarctica

    DEFF Research Database (Denmark)

    Søchting, Ulrik; Seppelt, R.

    2003-01-01

    Caloplaca coeruleofrigida Søchting & Seppelt is described from Southern Victoria Land, continental Antarctica. It is characterized by vertically elongated papillae and a pale orange pigmentation on shaded parts, and black thallus and apothecia on exposed parts of the thallus......Caloplaca coeruleofrigida Søchting & Seppelt is described from Southern Victoria Land, continental Antarctica. It is characterized by vertically elongated papillae and a pale orange pigmentation on shaded parts, and black thallus and apothecia on exposed parts of the thallus...

  12. Evidence of Zonal-Flow-Driven Limit-Cycle Oscillations during L-H Transition and at H-mode Pedestal of a New Small-ELM Regime in EAST

    DEFF Research Database (Denmark)

    Xu, G.; Wang, H.; Guo, H.

    Small-amplitude edge localized oscillations have been observed, for the first time, in EAST preceding the L-H transition at marginal input power, which manifest themselves as dithering in the divertor D signals at a frequency under 4 kHz, much lower than the GAM frequency. Detailed measurements...... providing a direct evidence of the zonal flows for the L-H transition at marginal input power. Furthermore, near the transition threshold sawtooth heat pulses appear to periodically enhance the dithering, finally triggering the L-H transition after a big sawtooth crash. The zonal flow induced limit...... link between them. A novel predator-prey model, incorporating the evolution of zonal flows, pressure gradient and turbulences at two different frequency ranges, has been developed and successfully reproduced the key features of this newly observed small-ELM regime....

  13. Upper Mantle Seismic Anisotropy Beneath the Northern Transantarctic Mountains, Antarctica from PKS, SKS, and SKKS Splitting Analysis

    Science.gov (United States)

    Graw, J. H.; Hansen, S. E.

    2016-12-01

    Stretching 3500 km across Antarctica, the Transantarctic Mountains (TAMs) separate the stable East Antarctic craton from the West Antarctic Rift System. Using data from a new, 15-station seismic array, known as the Transantarctic Mountains Northern Network, this study aims to constrain azimuthal anisotropy beneath a previously unexplored portion of the TAMs to assess both past and present deformational processes occurring in this region. Shear wave splitting parameters, including fast anisotropic axis directions and delay times, have been calculated for PKS, SKS, and SKKS phases using both the rotation-correlation and eigenvalue methods within the MATLAB-based SplitLab software package. Results show a relatively consistent average fast direction across the study area of 43 degrees, with an average delay time of 1.0 second. However, stations closer to the Ross Sea coastline show larger delay times compared to those behind the TAMs front, averaging 1.62 seconds. Our findings are similar to those from previous shear wave splitting investigations in regions neighboring our study area. Behind the TAMs front, East Antarctica is underlain by cold, thick continental lithosphere, and we suggest that anisotropy in this area is primarily localized in the upper mantle, associated with relict tectonic fabric from deformation events early in Antarctica's tectonic history. In contrast, the larger delay times near the coast may reflect anisotropy associated with a recently identified upper mantle velocity anomaly. This feature has been interpreted as the signature of rift-related decompression melting and Cenozoic extension; hence, the anisotropic signature may be associated with current tectonic processes beneath the TAMs front.

  14. Persistent organic pollutants (POPs) in the atmosphere of coastal areas of the Ross Sea, Antarctica: Indications for long-term downward trends.

    Science.gov (United States)

    Pozo, Karla; Martellini, Tania; Corsolini, Simonetta; Harner, Tom; Estellano, Victor; Kukučka, Petr; Mulder, Marie D; Lammel, Gerhard; Cincinelli, Alessandra

    2017-07-01

    Passive air samplers were used to evaluate long-term trends and spatial distribution of trace organic compounds in Antarctica. Duplicate PUF disk samplers were deployed at six automatic weather stations in the coastal area of the Ross sea (East Antarctica), between December 2010 and January 2011, during the XXVI Italian Scientific Research Expedition. Among the investigated persistent organic compounds, Hexachlorobenzene was the most abundant, with air concentrations ranging from 0.8 to 50 pg m -3 . In general, the following decreasing concentration order was found for the air samples analyzed: HCB > PeCB > PCBs > DDTs > HCHs. While HCB concentrations were in the same range as those reported in the atmosphere of other Antarctic sampling areas and did not show a decline, HCHs and DDTs levels were lower or similar to those determined one or two decades ago. In general, the very low concentrations reflected the pristine state of the East Antarctica air. Backward trajectories indicated the prevalence of air masses coming from the Antarctic continent. Local contamination and volatilization from ice were suggested as potential sources for the presence of persistent organic pollutants in the atmosphere. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Surface studies of water isotopes in Antarctica for quantitative interpretation of deep ice core data

    Science.gov (United States)

    Landais, Amaelle; Casado, Mathieu; Prié, Frédéric; Magand, Olivier; Arnaud, Laurent; Ekaykin, Alexey; Petit, Jean-Robert; Picard, Ghislain; Fily, Michel; Minster, Bénédicte; Touzeau, Alexandra; Goursaud, Sentia; Masson-Delmotte, Valérie; Jouzel, Jean; Orsi, Anaïs

    2017-07-01

    Polar ice cores are unique climate archives. Indeed, most of them have a continuous stratigraphy and present high temporal resolution of many climate variables in a single archive. While water isotopic records (δD or δ18O) in ice cores are often taken as references for past atmospheric temperature variations, their relationship to temperature is associated with a large uncertainty. Several reasons are invoked to explain the limitation of such an approach; in particular, post-deposition effects are important in East Antarctica because of the low accumulation rates. The strong influence of post-deposition processes highlights the need for surface polar research programs in addition to deep drilling programs. We present here new results on water isotopes from several recent surface programs, mostly over East Antarctica. Together with previously published data, the new data presented in this study have several implications for the climatic reconstructions based on ice core isotopic data: (1) The spatial relationship between surface mean temperature and mean snow isotopic composition over the first meters in depth can be explained quite straightforwardly using simple isotopic models tuned to d-excess vs. δ18O evolution in transects on the East Antarctic sector. The observed spatial slopes are significantly higher (∼ 0.7-0.8‰·°C-1 for δ18O vs. temperature) than seasonal slopes inferred from precipitation data at Vostok and Dome C (0.35 to 0.46‰·°C-1). We explain these differences by changes in condensation versus surface temperature between summer and winter in the central East Antarctic plateau, where the inversion layer vanishes in summer. (2) Post-deposition effects linked to exchanges between the snow surface and the atmospheric water vapor lead to an evolution of δ18O in the surface snow, even in the absence of any precipitation event. This evolution preserves the positive correlation between the δ18O of snow and surface temperature, but is

  16. Paleoclimatic and paleolatitude settings of accumulation of radiolarian siliceous–volcanogenic sequences in the middle Mesozoic Pacific: Evidence from allochthons of East Asia

    Science.gov (United States)

    Vishnevskaya, V. S.; Filatova, N. I.

    2017-09-01

    Jurassic-Cretaceous siliceous-volcanogenic rocks from nappes of tectonostratigraphic sequences of the East Asia Middle Cretaceous Okhotsk-Koryak orogenic belt are represented by a wide range of geodynamic sedimentation settings: oceanic (near-spreading zones, seamounts, and deep-water basins), marginal seas, and island arcs. The taxonomic compositions of radiolarian communities are used as paleolatitude indicators in the Northern Pacific. In addition, a tendency toward climate change in the Mesozoic is revealed based on these communities: from the warm Triassic to the cold Jurassic with intense warming from the Late Jurassic to the Early Cretaceous. Cretaceous warming led to heating of ocean waters even at moderately high latitudes and to the development of Tethyan radiolarians there. These data are confirmed by a global Cretaceous temperature peak coinciding with a high-activity pulse of the planetary mantle superplume system, which created thermal anomalies and the greenhouse effect. In addition, the Pacific superplume attributed to this system caused accelerated movement of oceanic plates, which resulted in a compression setting on the periphery of the Pacific and the formation of the Okhotsk-Koryak orogenic belt on its northwestern framing in the Middle Cretaceous, where Mesozoic rocks of different geodynamic and latitudinal-climate settings were juxtaposed into allochthonous units.

  17. Determinants of inequality in the up-to-date fully immunization coverage among children aged 24-35 months: Evidence from Zhejiang province, East China.

    Science.gov (United States)

    Hu, Yu; Wang, Ying; Chen, Yaping; Li, Qian

    2017-08-03

    This study aimed to determine the degree and determinants of inequality in up-to-date fully immunization (UTDFI) coverage among children of Zhejiang province, east China. We used data from the Zhejiang provincial vaccination coverage survey of 2014 and the health outcome was the UTDFI status among children aged 24-35 months. The household income per month was used as an index of socio-economic status for the inequality analysis. The concentration index (CI) was used to quantify the degree of inequality and the decomposition approach was applied to quantify the contributions from demographic factors to inequality in UTDFI coverage. The UTDFI coverage was 80.63% and the CI for UTDFI coverage was 0.12028 (95% CI: 0.10852-0.13175), indicating that immunization practice significantly favored children with relatively higher socio-economic status. The results of decomposition analysis suggested that 68.2% of the socio-economic inequality in UTDFI coverage should be explained by the mother's education level. Furthermore, factors such as birth order, ethnic group, maternal employment status, residence, immigration status, GDP per-capital and percentage of public health spending of the total health spending also could explain the disparity in UTDFI coverage. There exists inequality in UTDFI coverage among the socio-economic disadvantage children. Health interventions of narrowing the socio-economic inequality in UTDFI coverage will benefit from being supplemented with strategies aimed at poverty and illiteracy reduction.

  18. The correlation between Prorocentrum donghaiense blooms and the Taiwan warm current in the East China Sea - evidence for the "Pelagic Seed Bank" hypothesis.

    Directory of Open Access Journals (Sweden)

    Xinfeng Dai

    Full Text Available During the last two decades, large-scale high biomass algal blooms of the dinoflagellate Prorocentrum donghaiense Lu have occurred frequently in the East China Sea (ECS. The role of increasing nutrient concentrations in driving those blooms is well-established, but the source population that initiates them is poorly understood. We hypothesized that the front of Taiwan Warm Current (TWC may serve as a 'seed bank' that initiates P. donghaiense blooms in the ECS, as the physiochemical conditions in the TWC are suitable for the growth of P. donghaiense. In order to test this hypothesis, two surveys at different spatio-temporal scales were conducted in 2010 and 2011. We found a strong correlation in space and time between the abundance of P. donghaiense and the TWC. The spatial extent of the P. donghaiense bloom coincided with the TWC front in both 2010 and 2011. During the early development of the blooms, P. donghaiense concentration was highest at the TWC front, and then the bloom mass shifted inshore over the course of our 2011 survey. The TWC also moved inshore, albeit after the appearance of P. donghaiense. Overall, these results support our hypothesis that P. donghaiense blooms develop from the population at the TWC front in the ECS, suggesting the role of the ocean current front as a seed bank to dinoflagellate blooms.

  19. An insight into asymmetric back-arc extension: Tecto-magmatic evidences from the Ulleung Basin, the East Sea (Sea of Japan)

    Science.gov (United States)

    Kim, Gi Bom; Yoon, Seok-Hoon

    2017-10-01

    This paper presents an ancient example of asymmetric back-arc extension found in the Ulleung Basin, the southwestern East Sea (Sea of Japan). The paper focuses on the formative processes of variable asymmetric features of the basin and on their relationship to the style of lithospheric stretching. In the Ulleung Basin, features resulting from asymmetric back-arc extension include: 1) the syn-extensional volcanism concentrated to the northern flank of the basin, 2) the overwhelming number of north-dipping syn-extensional normal faults, 3) the style of boundary faults different between the northern and southern conjugate margins, and 4) the thickness of the crust and the depth to the Moho discontinuity that together decrease toward north. We argue that the fundamental control of such asymmetric features was the simple-shear-style lithospheric extension, which presumably involved a crustal detachment, the mid-crustal extension of north-dipping syn-extensional listric normal faults. By the simple-shear-style extension, syn-extensional faults evolved to dip toward north, and at the same time volcanic activities that had been initially widespread throughout the basin became to concentrate to the north of the basin. The northward deviantion of volcanic centers and the zone underlain by maximally attenuated crust (possibly the extinct spreading center) might be the result of separation between the loci of basin subsidence and asthenospheric upwelling that is common in simple-shear cases.

  20. Analysis of mercury and other heavy metals accumulated in lichen Usnea antarctica from James Ross Island, Antarctica

    Czech Academy of Sciences Publication Activity Database

    Zvěřina, O.; Láska, K.; Červenka, R.; Kuta, J.; Coufalík, Pavel; Komárek, J.

    2014-01-01

    Roč. 186, č. 12 (2014), s. 9089-9100 ISSN 0167-6369 Institutional support: RVO:68081715 Keywords : antarctica * heavy metal * mercury * lichen Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 1.679, year: 2014

  1. Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea ice

    Directory of Open Access Journals (Sweden)

    R. S. Humphries

    2016-02-01

    Full Text Available Better characterisation of aerosol processes in pristine, natural environments, such as Antarctica, have recently been shown to lead to the largest reduction in uncertainties in our understanding of radiative forcing. Our understanding of aerosols in the Antarctic region is currently based on measurements that are often limited to boundary layer air masses at spatially sparse coastal and continental research stations, with only a handful of studies in the vast sea-ice region. In this paper, the first observational study of sub-micron aerosols in the East Antarctic sea ice region is presented. Measurements were conducted aboard the icebreaker Aurora Australis in spring 2012 and found that boundary layer condensation nuclei (CN3 concentrations exhibited a five-fold increase moving across the polar front, with mean polar cell concentrations of 1130 cm−3 – higher than any observed elsewhere in the Antarctic and Southern Ocean region. The absence of evidence for aerosol growth suggested that nucleation was unlikely to be local. Air parcel trajectories indicated significant influence from the free troposphere above the Antarctic continent, implicating this as the likely nucleation region for surface aerosol, a similar conclusion to previous Antarctic aerosol studies. The highest aerosol concentrations were found to correlate with low-pressure systems, suggesting that the passage of cyclones provided an accelerated pathway, delivering air masses quickly from the free troposphere to the surface. After descent from the Antarctic free troposphere, trajectories suggest that sea-ice boundary layer air masses travelled equatorward into the low-albedo Southern Ocean region, transporting with them emissions and these aerosol nuclei which, after growth, may potentially impact on the region's radiative balance. The high aerosol concentrations and their transport pathways described here, could help reduce the discrepancy currently present between

  2. Estimating the long-term costs of ischemic and hemorrhagic stroke for Australia: new evidence derived from the North East Melbourne Stroke Incidence Study (NEMESIS).

    Science.gov (United States)

    Cadilhac, Dominique A; Carter, Rob; Thrift, Amanda G; Dewey, Helen M

    2009-03-01

    Stroke is associated with considerable societal costs. Cost-of-illness studies have been undertaken to estimate lifetime costs; most incorporating data up to 12 months after stroke. Costs of stroke, incorporating data collected up to 12 months, have previously been reported from the North East Melbourne Stroke Incidence Study (NEMESIS). NEMESIS now has patient-level resource use data for 5 years. We aimed to recalculate the long-term resource utilization of first-ever stroke patients and compare these to previous estimates obtained using data collected to 12 months. Population structure, life expectancy, and unit prices within the original cost-of-illness models were updated from 1997 to 2004. New Australian stroke survival and recurrence data up to 10 years were incorporated, as well as cross-sectional resource utilization data at 3, 4, and 5 years from NEMESIS. To enable comparisons, 1997 costs were inflated to 2004 prices and discounting was standardized. In 2004, 27 291 ischemic stroke (IS) and 4291 intracerebral hemorrhagic stroke (ICH) first-ever events were estimated. Average annual resource use after 12 months was AU$6022 for IS and AU$3977 for ICH. This is greater than the 1997 estimates for IS (AU$4848) and less than those for ICH (previously AU$10 692). The recalculated average lifetime costs per first-ever case differed for IS (AU$57 106 versus AU$52 855 [1997]), but differed more for ICH (AU$49 995 versus AU$92 308 [1997]). Basing lifetime cost estimates on short-term data overestimated the costs for ICH and underestimated those for IS. Patterns of resource use varied by stroke subtype and, overall, the societal cost impact was large.

  3. High prevalence of common respiratory viruses and no evidence of Middle East respiratory syndrome coronavirus in Hajj pilgrims returning to Ghana, 2013.

    Science.gov (United States)

    Annan, Augustina; Owusu, Michael; Marfo, Kwadwo Sarfo; Larbi, Richard; Sarpong, Francisca Naana; Adu-Sarkodie, Yaw; Amankwa, Joseph; Fiafemetsi, Samuel; Drosten, Christian; Owusu-Dabo, Ellis; Eckerle, Isabella

    2015-06-01

    The Middle East respiratory syndrome coronavirus (MERS-CoV) emerged in 2012 on the Arabian Peninsula and has caused severe respiratory disease with more than 800 laboratory-confirmed cases. The return of infected pilgrims to their home countries with a putative spread of MERS-CoV necessitates further surveillance. A cross sectional study of 839 adult African Hajj pilgrims returning to Accra in Ghana, West Africa, was conducted in 2013 to assess the prevalence of respiratory symptoms as well as of MERS-CoV, human rhinovirus (HRV), respiratory syncytial virus (RSV) and influenza A virus (FLU A) infection. Six hundred and fifty-one (77.6%) pilgrims had respiratory symptoms. Tests were positive for at least one of the viruses other than MERS-CoV in 179 (21.3%) of all pilgrims, with 22.4% detection in symptomatic vs. 17.6% detection in asymptomatic pilgrims. No MERS-CoV was detected, although common respiratory viruses were prevalent, with positive findings for HRV in 141 individuals (16.8%), RSV in 43 individuals (5.1%) and FLU A in 11 individuals (1.3%). Results were positive for more than one virus in 16 (1.9%) individuals, including 14 (1.7%) RSV/HRV co-infections and 2 (0.2%) FLU A/HRV co-infections. A total 146 (22.4%) of the symptomatic returnees tested positive for at least one respiratory virus compared with 33 (17.6%) of the asymptomatic pilgrims who had at least one detectable virus in their sample. The prevalence of viral respiratory infections among Hajj pilgrims in both symptomatic and asymptomatic subjects was high. Although it is reassuring that MERS-CoV was not detected in the tested population, there is a need for active surveillance of Hajj pilgrims. © 2015 John Wiley & Sons Ltd.

  4. Tuna and dolphin associations in the North-east Atlantic: Evidence of different ecological niches from stable isotope and heavy metal measurements

    Energy Technology Data Exchange (ETDEWEB)

    Das, K.; Lepoint, G.; Loizeau, V.; Debacker, V.; Dauby, P.; Bouquegneau, J.M

    2000-02-01

    Associations of tunas and dolphins in the wild are quite frequent events and the question arises how predators requiring similar diet in the same habitat share their environmental resources. As isotopic composition of an animal is related to that of its preys, stable isotope ({sup 13}C/{sup 12}C and {sup 15}N/{sup 14}N) analyses were performed in three predator species from the North-east Atlantic: the striped dolphin, Stenella coeruleoalba, the common dolphin Delphinus delphis and the albacore tuna, Thunnus alalunga, and compared to their previously described stomach content. Heavy metals (Cd, Zn, Cu and Fe) are mainly transferred through the diet and so, have been determined in the tissues of the animals. Tuna muscles display higher {delta}{sup 15}N than in common and striped dolphins (mean: 11.4 vs. 10.3%o and 10.4%o, respectively) which reflects their higher trophic level nutrition. Higher {delta}{sup 13}C are found in common (-18.4%o) and striped dolphin (-18.1%o) muscles than in albacore tuna (-19.3%o) probably in relation with its migratory pattern. The most striking feature is the presence of two levels of cadmium concentrations in the livers of the tunas (32 mg kg{sup -1} dry weight (DW) vs. 5 mg kg{sup -1} DW). These two groups also differ by their iron concentrations and their {delta}{sup 15}N and {delta}{sup 13}C liver values. These results suggest that in the Biscay Bay, tunas occupy two different ecological niches probably based on different squid inputs in their diet.

  5. The late 1980s regime shift in the ecosystem of Tsushima warm current in the Japan/East Sea: Evidence from historical data and possible mechanisms

    Science.gov (United States)

    Tian, Yongjun; Kidokoro, Hideaki; Watanabe, Tatsuro; Iguchi, Naoki

    2008-05-01

    A climatic regime shift, an abrupt change from cooling to warming in the Japan/East Sea (JES), particularly in the Tsushima warm current (TWC) region, occurred in the late 1980s. The ecosystem of the JES responded strongly to the changing thermal regime. Many, but not all biological components of the ecosystem, spanning from plankton to predatory fishes, and including both warm-water pelagic and cold-water demersal species responded to this late 1980s climatic regime shift in the JES. Diatom abundance (cell number) in spring from a monitoring line located in the central part of JES showed decadal variations with a step change from positive to negative anomalies in 1991. Zooplankton biomass in spring and autumn was high in the 1970s, declined during the 1980s, and returned to higher, but quite variable levels during the 1990s. Japanese sardine catch increased after 1974 to its peak level in 1989 and then declined dramatically to 1974 levels by 1997 with step changes in 1979 and 1994. Conversely, catches of other small pelagic species such as Japanese anchovy and common squid, and several higher-trophic fishes, such as yellowtail and tunas increased markedly in the 1990s compared to the early-mid 1980s. Step changes were detected in these pelagic species during 1989-1992. Catch of demersal species (crab, pink shrimp, Pacific cod and walleye pollock) were high during most of the 1970-1980s, but declined at various times in the late 1980s to generally low catches in the 1990s. Detailed analysis of the demersal fish assemblage composition, abundance and distribution indicated a shift in the late 1980s with several years lag in the time of change. Cold-water species (e.g., walleye pollock, Pacific cod) decreased in abundance and the regions in which their abundances remained high became greatly reduced in extent. Conversely, warm-water species (e.g., pointhead flounder, shotted halibut) increased in abundance and/or extended their spatial range (as indicated by trawl

  6. Melting of subducted continental crust: Geochemical evidence from Mesozoic granitoids in the Dabie-Sulu orogenic belt, east-central China

    Science.gov (United States)

    Zhao, Zi-Fu; Liu, Zhi-Bin; Chen, Qi

    2017-09-01

    Syn-collisional and postcollisional granitoids are common in collisional orogens, and they were primarily produced by partial melting of subducted continental crust. This is exemplified by Mesozoic granitoids from the Dabie-Sulu orogenic belt in east-central China. These granitoids were emplaced in small volumes in the Late Triassic (200-206 Ma) and the Late Jurassic (146-167 Ma) but massively in the Early Cretaceous (111-143 Ma). Nevertheless, all of them exhibit arc-like trace element distribution patterns and are enriched in Sr-Nd-Hf isotope compositions, indicating their origination from the ancient continental crust. They commonly contain relict zircons with Neoproterozoic and Triassic U-Pb ages, respectively, consistent with the protolith and metamorphic ages for ultrahigh-pressure (UHP) metaigneous rocks in the Dabie-Sulu orogenic belt. Some granitoids show low zircon δ18O values, and SIMS in-situ O isotope analysis reveals that the relict zircons with Neoproterozoic and Triassic U-Pb ages also commonly exhibit low δ18O values. Neoproterozoic U-Pb ages and low δ18O values are the two diagnostic features that distinguish the subducted South China Block from the obducted North China Block. Thus, the magma source of these Mesozoic granitoids has a genetic link to the subducted continental crust of the South China Block. On the other hand, these granitoids contain relict zircons with Paleoproterozoic and Archean U-Pb ages, which are present in both the South and North China Blocks. Taken together, the Mesozoic granitoids in the Dabie-Sulu orogenic belt and its hanging wall have their magma sources that are predominated by the continental crust of the South China Block with minor contributions from the continental crust of the North China Block. The Triassic continental collision between the South and North China Blocks brought the continental crust into the thickened orogen, where they underwent the three episodes of partial melting in the Late Triassic, Late

  7. Seasonality of CO2 in coastal oceans altered by increasing anthropogenic nutrient delivery from large rivers: evidence from the Changjiang–East China Sea system

    Directory of Open Access Journals (Sweden)

    W.-C. Chou

    2013-06-01

    Full Text Available Model studies suggested that human-induced increase in nutrient load may have stimulated primary production and thus enhanced the CO2 uptake capacity in the coastal ocean. In this study, we investigated the seasonal variations of the surface water's partial pressure of CO2 (pCO2sw in the highly human-impacted Changjiang–East China Sea system between 2008 and 2011. The seasonality of pCO2sw has large spatial variations, with the largest extreme of 170 ± 75 μatm on the inner shelf near the Changjiang Estuary (from 271 ± 55 μatm in summer to 441 ± 51 μatm in autumn and the weakest extreme of 53 ± 20 μatm on the outer shelf (from 328 ± 9 μatm in winter to 381 ± 18 μatm in summer. During the summer period, stronger stratification and biological production driven by the eutrophic Changjiang plume results in a very low dissolved inorganic carbon (DIC in surface waters and a very high DIC in bottom waters of the inner shelf, with the latter returning high DIC to the surface water during the mixed period. Interestingly, a comparison with historical data shows that the average pCO2sw on the inner shelf near the Changjiang Estuary has decreased notably during summer, but has increased during autumn and winter from the 1990s to the 2000s. We suggest that this decadal change is associated with recently increased eutrophication. This would increase both the photosynthetic removal of DIC in surface waters and the respiratory release of DIC in bottom waters during summertime, thereby returning more DIC to the surface during the subsequent mixing seasons and/or episodic extreme weather events (e.g., typhoons. Our finding demonstrates that increasing anthropogenic nutrient delivery from a large river may enhance the sequestration capacity of CO2 in summer but may reduce it in autumn and winter. Consequently, the coastal ocean may not necessarily take up more atmospheric CO2 in response to increasing eutrophication, and the net effect largely depends

  8. Controlling mechanisms of Thwaites Glacier, West Antarctica

    Science.gov (United States)

    Seroussi, H. L.; Morlighem, M.; Rignot, E. J.; Larour, E. Y.; Mouginot, J.; Khazendar, A.

    2013-12-01

    Ice shelves play a major role in the stability of fast flowing ice streams in Antarctica, by exerting buttressing on inland ice and controlling the discharge of ice into the ocean. However, the mechanisms at work remain poorly understood and interactions between floating and grounded ice need to be better characterized in order to estimate the impact of climate change on the ice sheets. Thwaites glacier, in West Antarctica, features a small and heavily fractured ice shelf that provides limited back stress pressure on inland ice but is pinned on the eastern part on a prominent ridge. Thwaites glacier has maintained a consistently high velocity and negative mass balance for at least 20 years. Recent observations show a widening of its fast flowing area as well as a sustained acceleration since 2006 and a rapid retreat of its grounding line in the center of the glacier. The objective of this work is to characterize the dynamic response of Thwaites glacier to changes in its floating tongue on decadal to centennial time scales. To achieve this objective, we rely on high resolution ice flow modeling and grounding line dynamics using the Ice Sheet System Model (ISSM). We will focus on the complex interplay between the main floating tongue of Thwaites Glacier and its eastern, slow moving ice shelf, which is pinned down by an ice rumple. The speed of the eastern ice shelf is strongly affected by the coupling with the main floating ice tongue, which results in significant fluctuations in speed of the eastern ice shelf the formation of ice shelf cracks at the grounding line during acceleration phases. Our results show that ice rigidity at the junction between the eastern and western part of the shelf controls the dynamic regime of the ice shelf and suggest that Thwaites Glacier is likely to undergo substantial changes in the coming decades. This work was performed at the California Institute of Technology's Jet Propulsion Laboratory and the University of California Irvine

  9. Chemodenitrification in the cryoecosystem of Lake Vida, Victoria Valley, Antarctica.

    Science.gov (United States)

    Ostrom, N E; Gandhi, H; Trubl, G; Murray, A E

    2016-11-01

    Lake Vida, in the Victoria Valley of East Antarctica, is frozen, yet harbors liquid brine (~20% salt, >6 times seawater) intercalated in the ice below 16 m. The brine has been isolated from the surface for several thousand years. The brine conditions (permanently dark, -13.4 °C, lack of O2 , and pH of 6.2) and geochemistry are highly unusual. For example, nitrous oxide (N2 O) is present at a concentration among the highest reported for an aquatic environment. Only a minor 17 O anomaly was observed in N2 O, indicating that this gas was predominantly formed in the lake. In contrast, the 17 O anomaly in nitrate (NO3-) in Lake Vida brine indicates that approximately half or more of the NO3- present is derived from atmospheric deposition. Lake Vida brine was incubated in the presence of 15 N-enriched substrates for 40 days. We did not detect microbial nitrification, dissimilatory reduction of NO3- to ammonium (NH4+), anaerobic ammonium oxidation, or denitrification of N2 O under the conditions tested. In the presence of 15 N-enriched nitrite (NO2-), both N2 and N2 O exhibited substantial 15 N enrichments; however, isotopic enrichment declined with time, which is unexpected. Additions of 15 N-NO2- alone and in the presence of HgCl2 and ZnCl2 to aged brine at -13 °C resulted in linear increases in the δ15 N of N2 O with time. As HgCl2 and ZnCl2 are effective biocides, we interpret N2 O production in the aged brine to be the result of chemodenitrification. With this understanding, we interpret our results from the field incubations as the result of chemodenitrification stimulated by the addition of 15 N-enriched NO2- and ZnCl2 and determined rates of N2 O and N2 production of 4.11-41.18 and 0.55-1.75 nmol L-1  day-1 , respectively. If these rates are representative of natural production, the current concentration of N2 O in Lake Vida could have been reached between 6 and 465 years. Thus, chemodenitrification alone is sufficient to explain the high levels of N2 O

  10. Proliferation of East Antarctic Adélie penguins in response to historical deglaciation.

    Science.gov (United States)

    Younger, Jane; Emmerson, Louise; Southwell, Colin; Lelliott, Patrick; Miller, Karen

    2015-11-18

    Major, long-term environmental changes are projected in the Southern Ocean and these are likely to have impacts for marine predators such as the Adélie penguin (Pygoscelis adeliae). Decadal monitoring studies have provided insight into the short-term environmental sensitivities of Adélie penguin populations, particularly to sea ice changes. However, given the long-term nature of projected climate change, it is also prudent to consider the responses of populations to environmental change over longer time scales. We investigated the population trajectory of Adélie penguins during the last glacial-interglacial transition to determine how the species was affected by climate warming over millennia. We focussed our study on East Antarctica, which is home to 30 % of the global population of Adélie penguins. Using mitochondrial DNA from extant colonies, we reconstructed the population trend of Adélie penguins in East Antarctica over the past 22,000 years using an extended Bayesian skyline plot method. To determine the relationship of East Antarctic Adélie penguins with populations elsewhere in Antarctica we constructed a phylogeny using mitochondrial DNA sequences. We found that the Adélie penguin population expanded 135-fold from approximately 14,000 years ago. The population growth was coincident with deglaciation in East Antarctica and, therefore, an increase in ice-free ground suitable for Adélie penguin nesting. Our phylogenetic analysis indicated that East Antarctic Adélie penguins share a common ancestor with Adélie penguins from the Antarctic Peninsula and Scotia Arc, with an estimated age of 29,000 years ago, in the midst of the last glacial period. This finding suggests that extant colonies in East Antarctica, the Scotia Arc and the Antarctic Peninsula were founded from a single glacial refuge. While changes in sea ice conditions are a critical driver of Adélie penguin population success over decadal and yearly timescales, deglaciation appears to have

  11. Bathymetric control of warm ocean water access along the East Antarctic Margin

    Science.gov (United States)

    Nitsche, F. O.; Porter, D.; Williams, G.; Cougnon, E. A.; Fraser, A. D.; Correia, R.; Guerrero, R.

    2017-09-01

    Observed thinning of the Totten Glacier in East Antarctica has cast doubt upon the stability of the East Antarctic Ice Sheet. Recent oceanographic observations at the front of the Totten Ice Shelf have confirmed the presence of modified Circumpolar Deep Water (mCDW), which likely promotes enhanced melting. Details of how this water accesses the shelf remain uncertain. Here we present new bathymetry and autumnal oceanographic data from the outer continental shelf, north of the Totten Glacier, that show up to 0.7°C mCDW in a >100 km wide and >500 m deep depression within the shelf break. In other parts of East Antarctica, a shelf break bathymetry shallower than 400 m prevents these warmer waters from entering the shelf environment. Our observations demonstrate that detailed knowledge of the bathymetry is critical to correctly model the across-shelf exchange of warm water to the various glaciers/ice shelves of Antarctica for future sea level prediction.

  12. Debris Flows and Water Tracks in Continental Antarctica: Water as a geomorphic agent in a hyperarid polar desert

    Science.gov (United States)

    Hauber, E.; Sassenroth, C.; De Vera, J.-P.; Schmitz, N.; Reiss, D.; Hiesinger, H.; Johnsson, A.

    2017-09-01

    Most studies using Antarctica as a Mars analogue have focused on the McMurdo Dry Valleys, which are among the coldest and driest places on Earth. However, other ice-free areas in continental Antarctica also display landforms that can inform the study of the possible geomorphic impact of water in a polar desert. Here we present a new analogue site in the interior of the Transantarctic Mountains in Northern Victoria Land. Gullies show unambiguous evidence for debris flows, and water tracks act as shallow subsurface pathways of water on top of the permafrost tale. Both processes are driven by meltwater from glacier ice and snow in an environ-ment which never experiences rainfall and in which the air temperatures probably never exceed 0°C.

  13. Haze episodes at Syowa Station, Antarctica

    Directory of Open Access Journals (Sweden)

    Keiichiro Hara

    2010-12-01

    Full Text Available During our aerosol measurement program at Syowa Station, Antarctica in 2004-2007, some low visibility (haze phenomena were observed under conditions with weak wind and without drifting snow and fog in winter-spring. In the "Antarctic haze" phenomenon, the number concentration of aerosol particles and black carbon concentration increased by one-two orders higher relative to background conditions at Syowa Station, while surface O_3 concentration simultaneously dropped especially after polar sunrise. Major aerosol constituents in the haze phenomenon were sea-salts (e.g., Na^+ and Cl^-. From the trajectory analysis and NAAPS model, the plumes from biomass burning in South America and southern Africa were transported to Syowa Station, Antarctic coast, during eastward (occasionally westward approach of cyclones in the Southern Ocean. Thus, poleward flow of the plume from mid-latitudes and injection of sea-salt particles during the transport may lead to the Antarctic haze phenomenon at Syowa Station. The difference of O_3 concentration between the background and the haze conditions tended to be larger in spring (polar sunrise relative to that in winter. Because enhancement of sea-salt particles can play an important role as an additional source of reactive halogen species, the haze episodes might make a significant contribution to surface O_3 depletion during the polar sunrise on the Antarctic coast.

  14. Optical Sky Brightness at Dome C, Antarctica

    Science.gov (United States)

    Kenyon, S.; Storey, J. W. V.; Burton, M. G.

    2006-08-01

    Dome C, Antarctica is a prime site for astronomical observations in terms of climate, wind speeds and turbulence. The infrared and terahertz sky backgrounds are the lowest of any inhabited place on Earth. However, at present little is known about the optical sky brightness and atmospheric extinction. Using a variety of modelling techniques together with data from the South Pole, we estimate the brightness of the night sky including the contributions from scattered sunlight, moonlight, aurorae, airglow, zodiacal light and artificial sources. We compare our results to another prime astronomical site, Mauna Kea. We find moonlight has significantly less effect at Dome C than at Mauna Kea. Aurorae are expected to have a minor impact at both sites, and zodiacal light is expected to be less at Dome C than at Mauna Kea. Airglow emissions at Dome C are expected to be similar to those at temperate sites. With proper planning, artificial sources of light pollution should be non-existent. The overall atmospheric extinction, or opacity, is expected to be the minimum possible. We conclude that Dome C is a very promising site not only for infrared and terahertz astronomy, but for optical astronomy as well..

  15. Social, occupational and cultural adaptation in Antarctica

    Science.gov (United States)

    Nicolas, Michel; Bishop, Sheryl; Weiss, Karine; Gaudino, Marvin

    2016-07-01

    Life in isolated and confined environments (ICEs, e.g., polar stations, submarine or space missions), is subject to important constraints which can generate psychosociological impaired outcomes. This study investigated psychological, social, occupational and cultural variables which are among the most important determinants in adaptation to a one-year wintering in Antarctica with 13 international participants. Our findings confirm and give further insight into the role of social (Cohesiveness, Social Support) and occupational (Implementation / Preparedness, Counterproductive Activity, Decision Latitude and Psychological Job Demands) dimensions of adaptation to ICE environments. Relationships between various social and occupational dimensions studies reflected detrimental effects ranging from decrements in cohesiveness, social support and work performance which differed across professional status and multicultural factors. These psychosocial issues have important implications for pre-mission selection and training, monitoring and support of crews during the mission and post-mission readaptation. Operational recommendations are suggested to improve adaptation, success and well-being for long-term ICE missions, e.g., to Mars and beyond.

  16. Crustal origin for coupled 'ultra-depleted' and 'plagioclase' signatures in MORB olivine-hosted melt inclusions: evidence from the Siqueiros Transform Fault, East Pacific Rise

    Science.gov (United States)

    Danyushevsky, Leonid; Perfit, Michael; Eggins, Stephen; Falloon, Trevor

    2002-11-01

    Geochemical data from melt inclusions in olivine phenocrysts in a picritic basalt from the Siqueiros Transform Fault on the northern East Pacific Rise provide insights into the petrogenesis of mid-ocean ridge basalts (MORB). The fresh lava contains 10% of olivine phenocrysts (Fo89.3-91.2) and rare, small (<1 mm) plagioclase phenocrysts with subhedral to irregular shapes with a range of compositions (An80-90, An57-63). Melt inclusions in olivine phenocrysts are glassy, generally rounded in shape and vary in size from a few to 200 µm. Although most of the inclusions have compositions that are generally consistent with being representative of parental melts for the pillow-rim glasses, several inclusions are clearly different. One inclusion, which contains a euhedral grain of high-Al, low-Ti spinel, has a composition unlike any melt inclusions previously described from primitive phenocrysts in MORB. It has a very high Al2O3 ( 20 wt%), very low TiO2 ( 0.04 wt%) and Na2O ( 1 wt%) contents, and a very high CaO/Na2O value ( 14). The glass inclusion is strongly depleted in all incompatible elements (La =0.052 ppm Yb =0.34; La/Sm(n) 0.27), but it has large positive Sr and Eu anomalies (Sr/Sr* 30; Eu/Eu* 3) and a negative Zr anomaly. It also has low S (0.015 wt%) and relatively high Cl (180 ppm). We suggest that this unusual composition is a consequence of olivine trapping plagioclase in a hot, strongly plagioclase-undersaturated magma and subsequent reaction between plagioclase and the host olivine producing melt and residual spinel. Two other melt inclusions in a different olivine phenocryst have compositions that are generally intermediate between 'normal' inclusions and the aluminous inclusion, but have even higher CaO and Sr contents. They are also depleted in incompatible elements, but to a lesser degree than the aluminous inclusion, and have smaller Sr and Eu anomalies. Similar inclusions have also been described in high-Fo olivine phenocrysts from Iceland and

  17. Re-assessment of recent (2008–2013 surface mass balance over Dome Argus, Antarctica

    Directory of Open Access Journals (Sweden)

    Minghu Ding

    2016-04-01

    Full Text Available At Dome Argus, East Antarctica, the surface mass balance (SMB from 2008 to 2013 was evaluated using 49 stakes installed across a 30×30 km area. Spatial analysis showed that at least 12 and 20 stakes are needed to obtain reliable estimates of SMB at local scales (a few hundred square metres and regional scales (tens of square kilometres, respectively. The estimated annual mean SMB was 22.9±5.9 kg m−2 yr−1, including a net loss by sublimation of −2.22±0.02 kg m−2 yr−1 and a mass gain by deposition of 1.37±0.01 kg m−2 yr−1. Therefore, ca. 14.3% of precipitation was modified after deposition, which should be considered when interpreting snow or ice core records produced by future drilling projects. The surface snow density and SMB in the western portion of Dome Argus are higher than in other areas, and these differences are likely related to the katabatic wind, which is strengthened by topography in this sector. A new digital elevation model (DEM of Dome Argus was generated, confirming that both peaks of the dome can be considered as the summit of the East Antarctic Ice Sheet. Findings from this study should be valuable for validating SMB estimates obtained from regional climate models and DEMs established using remote-sensing data.

  18. Fives decades of strong temporal variability in the flow of the Brunt Ice Shelf, Antarctica

    Science.gov (United States)

    De Rydt, Jan; Gudmundsson, Hilmar; Nagler, Thomas

    2017-04-01

    The Brunt Ice Shelf, East Antarctica, is a complex conglomerate of meteoric and marine ice, weakly connected to the much larger and faster-flowing Stancomb Wills Glacier Tongue to the east, and pinned down to the seabed in a small area around the McDonalds Ice Rumples in the north. The ice shelf is home to the UK research station Halley, from which changes to the ice shelf have been monitored closely since the 1960s. A unique 50-year record of the flow speed and an intense surveying programme over the past 10 years, have revealed a strong temporal variability in the flow. In particular, the speed of the ice shelf has increased by 10% each year over the past few years. In order to understand these rapid changes, we use a state-of-the-art flow model in combination with a range of satellite, ground-based and airborne radar data, to accurately simulate the historical flow and recent changes. In particular, we model the effects of a recently formed rift that is propagating at a speed of up to 600m/day and threatens to dislodge the ice shelf from its pinning point at the McDonalds Ice Rumples. We also report on the recent reactivation of a large chasm which has prompted the relocation of the station during the 2016/17 austral summer.

  19. Pollen and phytolith evidence for rice cultivation and vegetation change during the mid-late Holocene at the Jiangli site, Suzhou, East China.

    Science.gov (United States)

    Qiu, Zhenwei; Jiang, Hongen; Ding, Jinlong; Hu, Yaowu; Shang, Xue

    2014-01-01

    Pollen and phytolith analyses were undertaken at the Jiangli site in Suzhou, Jiangsu Province, combined with studies on macrofossils by flotation. The concentration of pollen decreased while the percentage of Poaceae pollen in the profile increased from the late phase of the Majiabang Culture to the Songze Culture suggesting that human impact on the local environment intensified gradually. The discovery of rice paddy implies a relatively advanced rice cultivation in this area during the middle-late Holocene. Other than phytoliths, the high percentage of Oryza-type Poaceae pollen (larger than 40 μm) supplied robust evidence for the existence of rice paddy. Moreover, the fact that the farther from the rice paddy, the lower the concentration and percentage of Poaceae pollen also proves that the dispersal and deposition of pollen is inversely proportional to the distance.

  20. Pollen and phytolith evidence for rice cultivation and vegetation change during the mid-late holocene at the Jiangli site, Suzhou, East China.

    Science.gov (United States)

    Qiu, Zhenwei; Jiang, Hongen; Ding, Jinlong; Hu, Yaowu; Shang, Xue

    2014-01-01

    Pollen and phytolith analyses were undertaken at the Jiangli site in Suzhou, Jiangsu Province, combined with studies on macrofossils by flotation. The concentration of pollen decreased while the percentage of Poaceae pollen in the profile increased from the late phase of the Majiabang Culture to the Songze Culture suggesting that human impact on the local environment intensified gradually. The discovery of rice paddy implies a relatively advanced rice cultivation in this area during the middle-late Holocene. Other than phytoliths, the high percentage of Oryza-type Poaceae pollen (larger than 40 µm) supplied robust evidence for the existence of rice paddy. Moreover, the fact that the farther from the rice paddy, the lower the concentration and percentage of Poaceae pollen also proves that the dispersal and deposition of pollen is inversely proportional to the distance.

  1. Pollen and phytolith evidence for rice cultivation and vegetation change during the mid-late Holocene at the Jiangli site, Suzhou, East China.

    Directory of Open Access Journals (Sweden)

    Zhenwei Qiu

    Full Text Available Pollen and phytolith analyses were undertaken at the Jiangli site in Suzhou, Jiangsu Province, combined with studies on macrofossils by flotation. The concentration of pollen decreased while the percentage of Poaceae pollen in the profile increased from the late phase of the Majiabang Culture to the Songze Culture suggesting that human impact on the local environment intensified gradually. The discovery of rice paddy implies a relatively advanced rice cultivation in this area during the middle-late Holocene. Other than phytoliths, the high percentage of Oryza-type Poaceae pollen (larger than 40 μm supplied robust evidence for the existence of rice paddy. Moreover, the fact that the farther from the rice paddy, the lower the concentration and percentage of Poaceae pollen also proves that the dispersal and deposition of pollen is inversely proportional to the distance.

  2. Pollen and phytolith evidence for rice cultivation and vegetation change during the mid-late holocene at the Jiangli site, Suzhou, East China.

    Directory of Open Access Journals (Sweden)

    Zhenwei Qiu

    Full Text Available Pollen and phytolith analyses were undertaken at the Jiangli site in Suzhou, Jiangsu Province, combined with studies on macrofossils by flotation. The concentration of pollen decreased while the percentage of Poaceae pollen in the profile increased from the late phase of the Majiabang Culture to the Songze Culture suggesting that human impact on the local environment intensified gradually. The discovery of rice paddy implies a relatively advanced rice cultivation in this area during the middle-late Holocene. Other than phytoliths, the high percentage of Oryza-type Poaceae pollen (larger than 40 µm supplied robust evidence for the existence of rice paddy. Moreover, the fact that the farther from the rice paddy, the lower the concentration and percentage of Poaceae pollen also proves that the dispersal and deposition of pollen is inversely proportional to the distance.

  3. 45 CFR 674.4 - Restrictions on collection of meteorites in Antarctica.

    Science.gov (United States)

    2010-10-01

    ... Antarctica. 674.4 Section 674.4 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL SCIENCE FOUNDATION ANTARCTIC METEORITES § 674.4 Restrictions on collection of meteorites in Antarctica. No person may collect meteorites in Antarctica for other than scientific research purposes. ...

  4. Multiple Meteoroid Impacts In Antarctica: Potential for Major Glacial Surges?

    Science.gov (United States)

    Rice, A. R.; Weihaupt, J.; van der Hoeven, F.

    2009-12-01

    Because of the similarity of an early gravity profile undertaken over a large area of Wilkes Land to those of known impact sites:[free air anomaly to -158mgal, apparent rim structures, circular basins, steep negative free air gravity anomaly gradients (to 4.71 mgal/km)] it was suggested that this anomaly might reflect a large impact site. The anomaly was uncharacteristic of mantle-related or geologic crustal variations,etc. Overlying crevassed ice, minor apparent effacing by glacial flow, rates of rebound,apparent lack of isostatic compensation, all lent to an interpretation of a relatively recent impact. Recent continuing work requires this early suggestion be modified to that of multiple impacts; this due to the discovery of a dominant cluster of negative free air gravity anomalies crossing the continental-oceanic boundary, and the East and West Antarctic structural boundary: the Transantarctic Mountains. These anomalies are coincident with complex subglacial craterform topographic features inferred from radiosounding. The distribution of the negative gravity anomalies lies within an elliptical area resembling scatter ellipses with the larger anomalies downrange and the lesser ones uprange. Aeromagnetic anomolies (large) correlate as well, revealing ring-shaped structures in the subglacial rock. These Antarctic gravity and magnetic anomalies do not depart significantly from those of known impact sites, deviations attributable to glacial scour. The distribution of the apparent impact structures therefore extends well beyond the original discovery into the Wilkes Subglacial Basin to the south, across the Transantarctic Mountains and into the Ross Embayment to the east, crossing regions of contrasting geology. The suggestion of impacts are supported by cores taken from the Ross Sea which have revealed the presence of material of high magnetic susceptibility (often taken as an indicator of meteor impact), impact glass and tektites. Cores taken off Wilkes Land reveal

  5. Contrasting Photo-physiological Responses of the Haptophyte Phaeocystis Antarctica and the Diatom Pseudonitzschia sp. in the Ross Sea (Antarctica

    Directory of Open Access Journals (Sweden)

    Sasha Tozzi

    2017-05-01

    Full Text Available The Antarctic is a unique environment in which substantial variations in irradiance occur over a number of time scales, and as a result phytoplankton need to acclimate and adapt to these changes. We conducted field and laboratory manipulations in the Ross Sea, Antarctica to examine photophysiological differences between Phaeocystis antarctica and Pseudonitzschia sp. a diatom that commonly occurrs in the Ross Sea, since these are the two functional groups that dominate abundance and productivity. Both exhibited reduced quantum yields due to high irradiances. P. antarctica, a haptophyte, displays a distinct photophysiological response to irradiance when compared to diatoms. P. antarctica showed a rapid recovery from high light exposure, as indicated by the rapid return to initial, high quantum yields, in contrast to diatoms, which responded more slowly. Absorption cross sections were high in both forms, but those in P. antarctica were significantly higher. Both organisms recovered within 24 h to initial quantum yields, suggesting that high irradiance exposure does not have a permanent effect on these organisms. Among all micronutrient additions (iron, cobalt, zinc and vitamin B12, only iron additions resulted in rapid impacts on quantum yields. Iron limitation also can result in reduced photosynthetic efficiency. Understanding these photophysiologial responses and the impact of oceanographic conditions provides constraints on modeling efforts of photosynthesis and primary productivity in the Antarctic.

  6. Live from Antarctica: The coldest, windiest place on Earth

    Science.gov (United States)

    In this first part of a four part 'Passport to Knowledge Special', hosted by Camille Jennings from Maryland Public Television, children from Maryland and Texas schools had the opportunity to directly interact with and ask questions of scientists and researchers in Antarctica live. The physical characteristics of Antarctica are featured, along with their effects on the human and microbiological organisms living in the region. The reasons behind the clothing worn in the Antarctic and the importance of the meteorological station are featured. Interviews with Professor Ian Dolziel (U of Texas) and Lt. commander John Joseph, NSFA (the head of the Navy Meteorology Center) occur with the school children, along with actual video footage of the surrounding geological features and geography. The 'Weatherops' is located at McMurdo Station, Antarctica.

  7. Ecological Biogeography of the Terrestrial Nematodes of Victoria Land, Antarctica

    Science.gov (United States)

    Adams, Byron J.; Wall, Diana H.; Virginia, Ross A.; Broos, Emma; Knox, Matthew A.

    2014-01-01

    Abstract The terrestrial ecosystems of Victoria Land, Antarctica are characteristically simple in terms of biological diversity and ecological functioning. Nematodes are the most commonly encountered and abundant metazoans of Victoria Land soils, yet little is known of their diversity and distribution. Herein we present a summary of the geographic distribution, habitats and ecology of the terrestrial nematodes of Victoria Land from published and unpublished sources. All Victoria Land nematodes are endemic to Antarctica, and many are common and widely distributed at landscape scales. However, at smaller spatial scales, populations can have patchy distributions, with the presence or absence of each species strongly influenced by specific habitat requirements. As the frequency of nematode introductions to Antarctica increases, and soil habitats are altered in response to climate change, our current understanding of the environmental parameters associated with the biogeography of Antarctic nematofauna will be crucial to monitoring and possibly mitigating changes to these unique soil ecosystems. PMID:25061360

  8. Automatic detection of subglacial lakes in radar sounder data acquired in Antarctica

    Science.gov (United States)

    Ilisei, Ana-Maria; Khodadadzadeh, Mahdi; Dalsasso, Emanuele; Bruzzone, Lorenzo

    2017-10-01

    Subglacial lakes decouple the ice sheet from the underlying bedrock, thus facilitating the sliding of the ice masses towards the borders of the continents, consequently raising the sea level. This motivated increasing attention in the detection of subglacial lakes. So far, about 70% of the total number of subglacial lakes in Antarctica have been detected by analysing radargrams acquired by radar sounder (RS) instruments. Although the amount of radargrams is expected to drastically increase, from both airborne and possible future Earth observation RS missions, currently the main approach to the detection of subglacial lakes in radargrams is by visual interpretation. This approach is subjective and extremely time consuming, thus difficult to apply to a large amount of radargrams. In order to address the limitations of the visual interpretation and to assist glaciologists in better understanding the relationship between the subglacial environment and the climate system, in this paper, we propose a technique for the automatic detection of subglacial lakes. The main contribution of the proposed technique is the extraction of features for discriminating between lake and non-lake basal interfaces. In particular, we propose the extraction of features that locally capture the topography of the basal interface, the shape and the correlation of the basal waveforms. Then, the extracted features are given as input to a supervised binary classifier based on Support Vector Machine to perform the automatic subglacial lake detection. The effectiveness of the proposed method is proven both quantitatively and qualitatively by applying it to a large dataset acquired in East Antarctica by the MultiChannel Coherent Radar Depth Sounder.

  9. Marisediminicola antarctica gen. nov., sp. nov., an actinobacterium isolated from the Antarctic.

    Science.gov (United States)

    Li, Hui-Rong; Yu, Yong; Luo, Wei; Zeng, Yin-Xin

    2010-11-01

    Strain ZS314(T) was isolated from a sandy intertidal sediment sample collected from the coastal area off the Chinese Antarctic Zhongshan Station, east Antarctica (6 9° 22' 13″ S 76 ° 21' 41″ E). The cells were Gram-positive, motile, short rods. The temperature range for growth was 0-26 °C and the pH for growth ranged from 5 to 10, with optimum growth occurring within the temperature range 18-23 °C and pH range 6.0-8.0. Growth occurred in the presence of 0-6 % (w/v) NaCl, with optimum growth occurring in the presence of 2-4 % (w/v) NaCl. Strain ZS314(T) had MK-10 as the major menaquinone and anteiso-C(15 : 0), iso-C(16 : 0) and anteiso-C(17 : 0) as major fatty acids. The cell-wall peptidoglycan type was B2β with ornithine as the diagnostic diamino acid. The major polar lipids were diphosphatidylglycerol and phosphatidylglycerol. The genomic DNA G+C content was approximately 67 mol%. Phylogenetic analysis based on 16S rRNA gene sequence similarity showed that strain ZS314(T) represents a new lineage in the family Microbacteriaceae. On the basis of the phylogenetic analyses and phenotypic characteristics, a new genus, namely Marisediminicola gen. nov., is proposed, harbouring the novel species Marisediminicola antarctica sp. nov. with the type strain ZS314(T) (=DSM 22350(T) =CCTCC AB 209077(T)).

  10. Validation of Airborne FMCW Radar Measurements of Snow Thickness Over Sea Ice in Antarctica

    Science.gov (United States)

    Galin, Natalia; Worby, Anthony; Markus, Thorsten; Leuschen, Carl; Gogineni, Prasad

    2012-01-01

    Antarctic sea ice and its snow cover are integral components of the global climate system, yet many aspects of their vertical dimensions are poorly understood, making their representation in global climate models poor. Remote sensing is the key to monitoring the dynamic nature of sea ice and its snow cover. Reliable and accurate snow thickness data are currently a highly sought after data product. Remotely sensed snow thickness measurements can provide an indication of precipitation levels, predicted to increase with effects of climate change in the polar regions. Airborne techniques provide a means for regional-scale estimation of snow depth and distribution. Accurate regional-scale snow thickness data will also facilitate an increase in the accuracy of sea ice thickness retrieval from satellite altimeter freeboard estimates. The airborne data sets are easier to validate with in situ measurements and are better suited to validating satellite algorithms when compared with in situ techniques. This is primarily due to two factors: better chance of getting coincident in situ and airborne data sets and the tractability of comparison between an in situ data set and the airborne data set averaged over the footprint of the antennas. A 28-GHz frequency modulated continuous wave (FMCW) radar loaned by the Center for Remote Sensing of Ice Sheets to the Australian Antarctic Division is used to measure snow thickness over sea ice in East Antarctica. Provided with the radar design parameters, the expected performance parameters of the radar are summarized. The necessary conditions for unambiguous identification of the airsnow and snowice layers for the radar are presented. Roughnesses of the snow and ice surfaces are found to be dominant determinants in the effectiveness of layer identification for this radar. Finally, this paper presents the first in situ validated snow thickness estimates over sea ice in Antarctica derived from an FMCW radar on a helicopterborne platform.

  11. Variations of snow accumulation rate in Central Antarctica over the last 250 years

    Directory of Open Access Journals (Sweden)

    A. A. Ekaykin

    2017-01-01

    Full Text Available The present-day global climate changes, very likely caused by anthropogenic activity, may potentially present a serious threat to the whole human civilization in a near future. In order to develop a plan of measures aimed at elimination of these threats and adaptation to these undesirable changes, one should deeply understand the mechanism of past and present (and thus, future climatic changes of our planet. In this study we compare the present-day data of instrumental observations of the air temperature and snow accumulation rate performed in Central Antarctica (the Vostok station with the reconstructed paleogeographic data on a variability of these parameters in the past. First of all, the Vostok station is shown to be differing from other East Antarctic stations due to relatively higher rate of warming (1.6 °C per 100 years since 1958. At the same time, according to paleogeographic data, from the late eighteenth century to early twenty-first one the total warming amounted to about 1 °C, which is consistent with data from other Antarctic regions. So, we can make a conclusion with high probability that the 30-year period of 1985–2015 was the warmest over the last 2.5 centuries. As for the snow accumulation rate, the paleogeographic data on this contain a certain part of noise that does not allow reliable concluding. However, we found a statistically significant relationship between the rate of snow accumulation and air temperature. This means that with further rise of temperature in Central Antarctica, the rate of solid precipitation accumulation will increase there, thus partially compensating increasing of the sea level.

  12. The IMBIE assessment of sea level rise due to Antarctica and Greenland

    Science.gov (United States)

    Shepherd, A.; Ivins, E. R.

    2016-12-01

    The Ice Sheet Mass Balance Inter-Comparison Exercise (IMBIE) is a joint-initiative of ESA and NASA aimed at producing a single estimate of the global sea level contribution due to the polar ice sheets. Within IMBIE, estimates of ice sheet mass balance are developed from satellite altimetry, gravimetry, and mass budget surveys using common spatial and temporal reference frames and using a common appreciation of the contributions due to glacial isostatic adjustment and surface mass balance. The project brings together the laboratories and space agencies that have been instrumental in developing independent estimates of ice sheet mass balance to date. In its first phase, IMBIE involved 27 teams, and delivered a first community assessment of ice sheet mass balance spanning a 20-year period up to 2012. There are now new satellite missions with longer data records, new geophysical corrections, and new teams producing assessments, and the period of overlap between independent satellite techniques has increased from 5 to 12 years. It is also clear that multiple satellite techniques are required to confidently separate mass changes associated with snowfall and ice dynamical imbalance. The second phase of IMBIE began in 2016, and the project now involves 70 teams from 14 nations including Australia, Austria, Belgium, Canada, Chile, Denmark, France, Germany, Ireland, Italy, the Netherlands, Sweden, the UK, and the USA. These teams are now working across five experimental groups, including 46 teams contributing independent satellite estimates of ice sheet mass balance and 24 teams contributing independent assessments of glacial isostatic adjustment and surface mass balance. Among the satellite surveys are 12 estimates of mass balance for the Antarctic Peninsula, 18 for West Antarctica, 15 for East Antarctica, and 7 for Greenland. These data sets will be contrasted and combined over summer to produce a single estimate of ice sheet mass balance for each of the polar ice sheets

  13. Coastal-change and glaciological map of the Ross Island area, Antarctica

    Science.gov (United States)

    Ferrigno, Jane G.; Foley, Kevin M.; Swithinbank, Charles; Williams, Richard S.

    2010-01-01

    Reduction in the area and volume of Earth?s two polar ice sheets is intricately linked to changes in global climate and to the resulting rise in sea level. Measurement of changes in area and mass balance of the Antarctic ice sheet was given a very high priority in recommendations by the Polar Research Board of the National Research Council. On the basis of these recommendations, the U.S. Geological Survey used its archive of satellite images to document changes in the cryospheric coastline of Antarctica and analyze the glaciological features of the coastal regions. The Ross Island area map is bounded by long 141? E. and 175? E. and by lat 76? S. and 81? S. The map covers the part of southern Victoria Land that includes the northwestern Ross Ice Shelf, the McMurdo Ice Shelf, part of the polar plateau and Transantarctic Mountains, the McMurdo Dry Valleys, northernmost Shackleton Coast, Hillary Coast, the southern part of Scott Coast, and Ross Island. Little noticeable change has occurred in the ice fronts on the map, so the focus is on glaciological features. In the western part of the map area, the polar plateau of East Antarctica, once thought to be a featureless region, has subtle wavelike surface forms (megadunes) and flow traces of glaciers that originate far inland and extend to the coast or into the Ross Ice Shelf. There are numerous outlet glaciers. Glaciers drain into the McMurdo Dry Valleys, through the Transantarctic Mountains into the Ross Sea, or into the Ross Ice Shelf. Byrd Glacier is the largest. West of the Transantarctic Mountains are areas of blue ice, readily identifiable on Landsat images, that have been determined to be prime areas for finding meteorites. Three subglacial lakes have been identified in the map area. Because McMurdo Station, the main U.S. scientific research station in Antarctica, is located on Ross Island in the map area, many of these and other features in the area have been studied extensively. The paper version of this map is

  14. Ice megadunes on Mars: analogy with Antarctica

    Science.gov (United States)

    Herny, Clémence; Massé, Marion; Bourgeois, Olivier; Carpy, Sabrina; Le Mouélic, Stéphane; Appéré, Thomas; Smith, Isaac; Spiga, Aymeric; Rodriguez, Sébastien

    2014-05-01

    Mass and energy balance of ice sheets are driven by complex interactions between the atmosphere and the cryosphere. Feedbacks between katabatic winds and the cryosphere may lead to the formation of sedimentation waves, so-called megadunes, at the surface of ice sheets. These have been first described in Antarctica. Here we use topographic data, optical images, and spectroscopic data acquired by Mars orbiters. We show that the surface of the Martian North Polar Cap displays two superimposed sets of sedimentation waves with differing wavelengths. These sedimentation waves have similarities with Antarctic ice megadunes regarding their surface morphology, texture, grain size, and internal stratigraphic architecture. Their shallow-dipping upwind sides, their tops and the intervening troughs are covered by young ice and occasional sastrugi fields, indicative of net accumulation. On the other hand, their steep-dipping downwind sides either expose exhumed layers of dusty old ice or correspond to smooth surfaces of coarse-grained ice, indicative of net ablation or reduced net accumulation associated with sublimation and metamorphism. These surface characteristics and the internal stratigraphic architecture revealed by radar sounding are consistent with the interpretation that both sets of Martian sedimentation waves grow and migrate upwind in response to the development of periodic accumulation/ablation patterns controlled by katabatic winds. The smaller waves, characterized by reduced net accumulation on their downwind sides, are probably analogous to the Antarctic megadunes that have been described so far. On the other hand, a terrestrial equivalent remains to be discovered for the larger ones, characterized by net ablation on their downwind sides. The recognition of these sedimentation waves provides the basis for the development of a common model of ice/wind interaction at the surface of Martian and terrestrial ice sheets and for future investigations on the respective

  15. Hydrocarbons in benthic marine algae of the Vestfold Hills, Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Dhargalkar, V.K.; Bhosle, N.B.

    1987-02-01

    Recently, Antarctic continent has been the center for diverse research activities. This has resulted in a large number of research and supply vessels visiting Antarctica, which may lead to the contamination of Antarctic environment due to unintentional release of petroleum products. It is, therefore, essential to monitor the concentration of various pollutants in water, sediment, flora and fauna of this region which may also serve as a baseline data for future comparison. With this in view, total hydrocarbon concentration in some marine benthic algae collected from the Vestfold Hills, Antarctica was studied using fluorescence spectroscopy.

  16. Declassified Intelligence Satellite Photography (DISP) Coverage of Antarctica

    Science.gov (United States)

    Bindschadler, Robert; Seider, Wendy

    1998-01-01

    This report summarizes the results of a nine-week summer project examining all Declassified Intelligence Satellite Photography (DISP) of Antarctica. It was discovered that the data were collected in three separate missions during 1962 and 1963. The first two missions covered only the coastal areas, while the third mission covered the entire continent. Many of the 1782 frames collected were cloudy. This is especially true of West Antarctica. An optimal set of photographs covering the entire Antarctic coastline is identified along with some examples that show changes in the coastline which have occurred since the early 1960s.

  17. Lead isotopic evidence for interaction between plume and lower crust during emplacement of peralkaline Lovozero rocks and related rare-metal deposits, East Fennoscandia, Kola Peninsula, Russia

    Science.gov (United States)

    Zartman, R. E.; Kogarko, L. N.

    2017-05-01

    country rock provides strong evidence that this old lower crust was the contaminant responsible for the deviation of the Lovozero rocks from a presumed original FOZO lead isotopic composition. Evaluating the presence of such a lower crustal component in the Lovozero rock samples suggests a 5-10% contamination by such rocks. Contamination by upper crustal rock is limited to only a negligible amount.

  18. Wind-driven ocean dynamic effects on the contrasting sea-ice trends around West Antarctica

    Science.gov (United States)

    Lee, Sang-Ki; Volkov, Denis; Lopez, Hosmay; Cheon, Woo Geun; Gordon, Arnold; Liu, Yanyun; Wanninkhof, Rik

    2017-04-01

    Since late 1978, Antarctic sea-ice extent in the East Pacific has retreated persistently over the Amundsen and Bellingshausen Seas in warm seasons, but expanded over the Ross and Amundsen Seas in cold seasons, while an almost opposite trend has occurred in the Atlantic over the Weddell Sea. Previous studies have shown that the contrasting sea-ice trends in the East Pacific and Atlantic could be explained by the strengthening Southern Hemisphere (SH) subpolar low over West Antarctica and associated cold- and warm-air advections and sea-ice drift. By using a surface-forced ocean and sea-ice coupled model, we show that regional wind-driven ocean dynamics also played a key role. In the East Pacific, the strengthening SH westerlies in the region enhanced Ekman upwelling of the warm upper Circumpolar Deep Water, which directly contributed to the retreat of sea ice in warm seasons, and increased the northward Ekman transport of cold Antarctic surface water, which supported the expansion of sea ice in cold seasons. In the Atlantic, the northern branch of the Weddell Gyre strengthened due to the poleward shifting SH westerlies in the region. This in turn sharply increased the meridional thermal gradient across it as constrained by the thermal wind balance. Ocean heat budget analysis further suggests that the strengthened northern branch of the Weddell Gyre acted as a barrier against the poleward ocean heat transport, and thus produced anomalous heat divergence within the Weddell Gyre and anomalous heat convergence north of the gyre. The associated cooling within the Weddell Gyre and the warming north of the gyre contributed to the expansion of sea ice in warm seasons and the retreat in cold seasons, respectively.

  19. Change and Variability in East Antarctic Sea Ice Seasonality, 1979/80–2009/10

    Science.gov (United States)

    Massom, Robert; Reid, Philip; Stammerjohn, Sharon; Raymond, Ben; Fraser, Alexander; Ushio, Shuki

    2013-01-01

    Recent analyses have shown that significant changes have occurred in patterns of sea ice seasonality in West Antarctica since 1979, with wide-ranging climatic, biological and biogeochemical consequences. Here, we provide the first detailed report on long-term change and variability in annual timings of sea ice advance, retreat and resultant ice season duration in East Antarctica. These were calculated from satellite-derived ice concentration data for the period 1979/80 to 2009/10. The pattern of change in sea ice seasonality off East Antarctica comprises mixed signals on regional to local scales, with pockets of strongly positive and negative trends occurring in near juxtaposition in certain regions e.g., Prydz Bay. This pattern strongly reflects change and variability in different elements of the marine “icescape”, including fast ice, polynyas and the marginal ice zone. A trend towards shorter sea-ice duration (of 1 to 3 days per annum) occurs in fairly isolated pockets in the outer pack from∼95–110°E, and in various near-coastal areas that include an area of particularly strong and persistent change near Australia's Davis Station and between the Amery and West Ice Shelves. These areas are largely associated with coastal polynyas that are important as sites of enhanced sea ice production/melt. Areas of positive trend in ice season duration are more extensive, and include an extensive zone from 160–170°E (i.e., the western Ross Sea sector) and the near-coastal zone between 40–100°E. The East Antarctic pattern is considerably more complex than the well-documented trends in West Antarctica e.g., in the Antarctic Peninsula-Bellingshausen Sea and western Ross Sea sectors. PMID:23705008

  20. Change and variability in East antarctic sea ice seasonality, 1979/80-2009/10.

    Science.gov (United States)

    Massom, Robert; Reid, Philip; Stammerjohn, Sharon; Raymond, Ben; Fraser, Alexander; Ushio, Shuki

    2013-01-01

    Recent analyses have shown that significant changes have occurred in patterns of sea ice seasonality in West Antarctica since 1979, with wide-ranging climatic, biological and biogeochemical consequences. Here, we provide the first detailed report on long-term change and variability in annual timings of sea ice advance, retreat and resultant ice season duration in East Antarctica. These were calculated from satellite-derived ice concentration data for the period 1979/80 to 2009/10. The pattern of change in sea ice seasonality off East Antarctica comprises mixed signals on regional to local scales, with pockets of strongly positive and negative trends occurring in near juxtaposition in certain regions e.g., Prydz Bay. This pattern strongly reflects change and variability in different elements of the marine "icescape", including fast ice, polynyas and the marginal ice zone. A trend towards shorter sea-ice duration (of 1 to 3 days per annum) occurs in fairly isolated pockets in the outer pack from∼95-110°E, and in various near-coastal areas that include an area of particularly strong and persistent change near Australia's Davis Station and between the Amery and West Ice Shelves. These areas are largely associated with coastal polynyas that are important as sites of enhanced sea ice production/melt. Areas of positive trend in ice season duration are more extensive, and include an extensive zone from 160-170°E (i.e., the western Ross Sea sector) and the near-coastal zone between 40-100°E. The East Antarctic pattern is considerably more complex than the well-documented trends in West Antarctica e.g., in the Antarctic Peninsula-Bellingshausen Sea and western Ross Sea sectors.

  1. Change and variability in East antarctic sea ice seasonality, 1979/80-2009/10.

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    Robert Massom

    Full Text Available Recent analyses have shown that significant changes have occurred in patterns of sea ice seasonality in West Antarctica since 1979, with wide-ranging climatic, biological and biogeochemical consequences. Here, we provide the first detailed report on long-term change and variability in annual timings of sea ice advance, retreat and resultant ice season duration in East Antarctica. These were calculated from satellite-derived ice concentration data for the period 1979/80 to 2009/10. The pattern of change in sea ice seasonality off East Antarctica comprises mixed signals on regional to local scales, with pockets of strongly positive and negative trends occurring in near juxtaposition in certain regions e.g., Prydz Bay. This pattern strongly reflects change and variability in different elements of the marine "icescape", including fast ice, polynyas and the marginal ice zone. A trend towards shorter sea-ice duration (of 1 to 3 days per annum occurs in fairly isolated pockets in the outer pack from∼95-110°E, and in various near-coastal areas that include an area of particularly strong and persistent change near Australia's Davis Station and between the Amery and West Ice Shelves. These areas are largely associated with coastal polynyas that are important as sites of enhanced sea ice production/melt. Areas of positive trend in ice season duration are more extensive, and include an extensive zone from 160-170°E (i.e., the western Ross Sea sector and the near-coastal zone between 40-100°E. The East Antarctic pattern is considerably more complex than the well-documented trends in West Antarctica e.g., in the Antarctic Peninsula-Bellingshausen Sea and western Ross Sea sectors.