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Sample records for islands east antarctica

  1. 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.

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

    Directory of Open Access Journals (Sweden)

    J. L. Roberts

    2012-07-01

    Full Text Available A borehole temperature record from the Mill Island (East Antarctic icecap reveals a large surface warming signal manifested as a 0.75 K temperature difference over the approximate 100 m depth below the seasonally varying zone. The temperature profile shows a break in gradient between 49 and 69 m depth, which we model with inverse numerical simulations, indicating that surface warming started around the austral summer of 1980/1981 AD ± 5 yr. This warming of approximately 0.37 K per decade is large by Antarctic standards and is only exceeded in regions of the Antarctic Peninsula. While this warming may reflect regional scale air temperature increases, the lack of comparable trends for other East Antarctic sites suggests local influences are largely responsible for the observed trend. 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 potentially play a key role at this location due to the proximity of the Shackleton Ice Shelf and sea-ice zone.

  3. Pine Island Glacier, Antarctica

    Science.gov (United States)

    2001-01-01

    This pair of MISR images of the Pine Island Glacier in western Antarctica was acquired on December 12, 2000 during Terra orbit 5246. At left is a conventional, true-color image from the downward-looking (nadir) camera. The false-color image at right is a composite of red band data taken by the MISR forward 60-degree, nadir, and aftward 60-degree cameras, displayed in red, green, and blue colors, respectively. Color variations in the left (true-color) image highlight spectral differences. In the multi-angle composite, on the other hand, color variations act as a proxy for differences in the angular reflectance properties of the scene. In this representation, clouds show up as light purple. Blue to orange gradations on the surface indicate a transition in ice texture from smooth to rough. For example, the bright orange 'carrot-like' features are rough crevasses on the glacier's tongue. In the conventional nadir view, the blue ice labeled 'rough crevasses' and 'smooth blue ice' exhibit similar coloration, but the multi-angle composite reveals their different textures, with the smoother ice appearing dark purple instead of orange. This could be an indicator of different mechanisms by which this ice is exposed. The multi-angle view also reveals subtle roughness variations on the frozen sea ice between the glacier and the open water in Pine Island Bay.To the left of the 'icebergs' label are chunks of floating ice. Additionally, smaller icebergs embedded in the frozen sea ice are visible below and to the right of the label. These small icebergs are associated with dark streaks. Analysis of the illumination geometry suggests that these streaks are surface features, not shadows. Wind-driven motion and thinning of the sea ice in the vicinity of the icebergs is one possible explanation.Recently, Robert Bindschadler, a glaciologist at the NASA Goddard Space Flight Center discovered in Landsat 7 imagery a newly-formed crack traversing the Pine Island Glacier. This crack is

  4. 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.

  5. Continuous and discrete measurements of atmospheric methane from an ice core from Roosevelt Island, East Ross Sea, Antarctica

    Science.gov (United States)

    Blunier, T.; Simonsen, M. F.; Brook, E.; Lee, J.; Vallelonga, P. T.; Bertler, N. A. N.

    2014-12-01

    A new ice core from Roosevelt Island was drilled for the Roosevelt Island Climate Evolution (RICE) project to establish the history of deglaciation of the Ross Sea. Evidence of glacial retreat in the Ross Sea Embayment shows that deglaciation happened in several stages of rapid collapse and persisted well after the melting of the Northern Hemisphere ice sheets was complete. The drill location on a small island surrounded by sea ice makes dating the core a challenge. We present a timescale for Roosevelt Island using mixing ratios of methane in air preserved within the ice core measured continuously with a Picarro laser spectrometer as well as in high-resolution with gas chromatography (GC). Discrete data from GC analysis over the top 400m of core replicate both the magnitude and variations from other high-resolution ice core records from WAIS Divide, Law Dome, GISP2 and NEEM S1. Both the continuous and discrete methane records of the RICE core were matched to these established records and provide an accurate and consistent depth-age relationship for the past 3.6kyr. The deeper part of the core was measured continuously in July 2014. First inspection of the data suggests that the oldest section of the core reaches into the previous interglacial (Eemian). We will present preliminary evaluated continuous methane data for the deeper part of the core together with a first time scale for the Roosevelt Island ice core.

  6. Late Quaternary environmental and climate history of Rauer Group, East Antarctica

    NARCIS (Netherlands)

    Berg, S.; Wagner, B.; Cremer, H.; Leng, M.J.; Melles, M.

    2010-01-01

    The Rauer Group is an archipelago in Prydz Bay, East Antarctica. The ice-free islands and the surrounding shallow marine areas provide valuable archives for the reconstruction of the late Pleistocene and Holocene environmental and climatic history of the region. Two sediment records from two marine

  7. Abrupt climate warming in East Antarctica during the early Holocene

    NARCIS (Netherlands)

    Cremer, H.; Heiri, O.; Wagner, B.; Wagner-Cremer, F.

    2007-01-01

    We report a centennial-scale warming event between 8600 and 8400 cal BP from Amery Oasis, East Antarctica, that is documented by the geochemical record in a lacustrine sediment sequence. The organic carbon content, the C/S ratio, and the sedimentation rate in this core have distinctly elevated value

  8. Ice plug prevents irreversible discharge from East Antarctica

    Science.gov (United States)

    Mengel, M.; Levermann, A.

    2014-06-01

    Changes in ice discharge from Antarctica constitute the largest uncertainty in future sea-level projections, mainly because of the unknown response of its marine basins. Most of West Antarctica's marine ice sheet lies on an inland-sloping bed and is thereby prone to a marine ice sheet instability. A similar topographic configuration is found in large parts of East Antarctica, which holds marine ice equivalent to 19 m of global sea-level rise, that is, more than five times that of West Antarctica. Within East Antarctica, the Wilkes Basin holds the largest volume of marine ice that is fully connected by subglacial troughs. This ice body was significantly reduced during the Pliocene epoch. Strong melting underneath adjacent ice shelves with similar bathymetry indicates the ice sheet's sensitivity to climatic perturbations. The stability of the Wilkes marine ice sheet has not been the subject of any comprehensive assessment of future sea level. Using recently improved topographic data in combination with ice-dynamic simulations, we show here that the removal of a specific coastal ice volume equivalent to less than 80 mm of global sea-level rise at the margin of the Wilkes Basin destabilizes the regional ice flow and leads to a self-sustained discharge of the entire basin and a global sea-level rise of 3-4 m. Our results are robust with respect to variation in ice parameters, forcing details and model resolution as well as increased surface mass balance, indicating that East Antarctica may become a large contributor to future sea-level rise on timescales beyond a century.

  9. The establishment of GPS network in Grove Mountains, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The Grove Mountains are located in Princess Elizabeth Land, East Antarctica, extending from 72° to 73°S latitude and 73° to 76°E longitude, covering approximately 8000 km2 areas. During the 2002/2003 austral summer season, the 19th CHINARE (Chinese National Antarctic Research Expedition) carried out the third expedition in Grove Mountains, East Antarctica. The Geodetic network was established, which can provide ground control for the satellite image map for the multi-discipline expedition in the Grove Mountains where seven permanent GPS benchmarks were set up supported by the helicopter and snow vehicles. All GPS sites besides Z001 were observed at least for one hour using the dual frequencies Trimble 4000ssi GPS receivers. The data were processed by the comprehensive GPS analysis package-GAMIT/GLOBK and the precision is good enough to satisfy with the acquirement of satellite mapping in this area.

  10. Summer weather characteristics on the Grove Mountain of East Antarctica

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The summer weather characteristics of the Grove Mountain, East Antarctica, are presented based on the data obtained by Chinese National Antarctic Expedition (CHINARE) in January 1999. The result shows that the pattern of daily variation of temperature and the prevailing wind direction in Grove is similar to that of Zhongshan Station. However, the daily range of temperature and strong wind frequency are much higher than those of Zhongshan Station. The change of wind direction is close to the weather system that impacted the Grove Mountain. The warm and wet air from northern parts often causes the precipitation. The clear weather appears when controlled by eastern winds in January.

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

    Science.gov (United States)

    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. 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.

  13. Mass balance of the Lambert Glacier basin, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Since it is the largest glacier system in Antarctica, the Lambert Glacier basin plays an important role in the mass balance of the overall Antarctic ice sheet. The observed data and shallow core studies from the inland traverse investigations in recent years show that there are noticeable differences in the distribution and variability of the snow accumulation rate between east and west sides. On the east side, the accumulation is higher on the average and has increased in the past decades, while on the west side it is contrary. The ice movement measurement and the ice flux calculation indicate that the ice velocity and the flux are larger in east than in west, meaning that the major part of mass supply for the glacier is from the east side. The mass budget estimate with the latest data gives that the integrated accumulation over the upstream area of the investigation traverse route is larger than the outflow ice flux by 13%, suggesting that the glacier basin is in a positive mass balance state and the ice thickness will increase if the present climate is keeping.

  14. Electrical structure beneath Schirmacher Oasis, East Antarctica: a magnetotelluric study

    Directory of Open Access Journals (Sweden)

    D.N. Murthy

    2013-11-01

    Full Text Available Maitri Station (70.76°S; 11.73°E is located in Schirmacher Oasis, a coastal nunatak in north-central Dronning Maud Land covering an area of 35 km2. Here, we report results from the first magnetotelluric experiments and delineate the deep electrical conductivity structure under Schirmacher Oasis using the data acquired during the 24th Indian Antarctic Scientific Expedition. The magnetotelluric method has the advantage of shallow to deeper level coverage as the data acquisition covers a wide frequency band of 10−3–103 Hz, permitting different penetration depths depending on the frequency and conductivity of the layer under investigation. The modelling results indicate the presence of a highly resistive (8000–10 000 ohm m upper crust, which shows a lateral variation in thickness from 20 km (below site 6 in the east to 10 km (between sites 1 and 2 in the west. It is underlain by a less resistive (500–600 ohm m lower crust. The highly resistive upper crustal structure supports the existing notion that western Dronning Maud Land is a stable, cratonic platform. Results of free-air gravity, seismic, geomagnetic and surface wave dispersion investigations in East Antarctica also indicate a cratonic-type crust. The results of our study allow us to identify a westward thinning of the upper crust with a marked boundary between sites 1 and 2. We also find evidence for the continuity of the Mozambique mobile belt in East Antarctica on the western side of Schirmacher Oasis.

  15. Volcanic hazard on Deception Island (South Shetland Islands, Antarctica)

    Science.gov (United States)

    Bartolini, S.; Geyer, A.; Martí, J.; Pedrazzi, D.; Aguirre-Díaz, G.

    2014-09-01

    Deception Island is the most active volcano in the South Shetland Islands and has been the scene of more than twenty identified eruptions over the past two centuries. In this contribution we present the first comprehensive long-term volcanic hazard assessment for this volcanic island. The research is based on the use of probabilistic methods and statistical techniques to estimate volcanic susceptibility, eruption recurrence and the most likely future eruptive scenarios. We perform a statistical analysis of the time series of past eruptions and the spatial extent of their products, including lava flows, fallout, pyroclastic density currents and lahars. The Bayesian event tree statistical method HASSET is applied to calculate eruption recurrence, while the QVAST tool is used in an analysis of past activity to calculate the possibility that new vents will open (volcanic susceptibility). On the basis of these calculations, we identify a number of significant scenarios using the GIS-based VORIS 2.0.1 and LAHARZ software and evaluate the potential extent of the main volcanic hazards to be expected on the island. This study represents a step forward in the evaluation of volcanic hazard on Deception Island and the results obtained are potentially useful for long-term emergency planning.

  16. Reconstruction of the East Africa and Antarctica continental margins

    Science.gov (United States)

    Nguyen, Luan C.; Hall, Stuart A.; Bird, Dale E.; Ball, Philip J.

    2016-06-01

    The Early Jurassic separation of Antarctica from Africa plays an important role in our understanding of the dispersal of Gondwana and Pangea. Previous reconstruction models contain overlaps and gaps in the restored margins that reflect difficulties in accurately delineating the continent-ocean-boundary (COB) and determining the amount and distribution of extended continental crust. This study focuses on the evolution of the African margin adjacent to the Mozambique Basin and the conjugate Antarctic margin near the Riiser-Larsen Sea. Satellite-derived gravity data have been used to trace the orientations and landward limits of fracture zones. A 3-D gravity inversion has produced a crustal thickness model that reliably quantifies the extent and amount of stretched crust. Crustal thicknesses together with fracture zone terminations reveal COBs that are significantly closer to the African and Antarctic coasts than previously recognized. Correlation of fracture zone azimuths and identified COBs suggests Antarctica began drifting away from Africa at approximately 171 Ma in a roughly SSE direction. An areal-balancing method has been used to restore the crust to a uniform prerift thickness so as to perform a nonrigid reconstruction for both nonvolcanic and volcanic margins. Both margins reveal a trend of increasing extension from east to west. Our results suggest Africa underwent extension of 60-120 km, while Antarctic crust was stretched by 105-180 km. Various models tested to determine the direction of extension during rifting suggest that Antarctica moved away from Africa in a WNW-ESE direction during the period between 184 and 171 Ma prior to the onset of seafloor spreading.

  17. Surface and snowdrift sublimation at Princess Elisabeth station, East Antarctica

    Directory of Open Access Journals (Sweden)

    W. Thiery

    2012-04-01

    Full Text Available In the near-coastal regions of Antarctica, a significant fraction of the snow precipitating onto the surface is removed again through sublimation – either directly from the surface or from drifting snow particles. Meteorological observations from an Automatic Weather Station (AWS near the Belgian research station Princess Elisabeth in Dronning Maud Land, East-Antarctica, are used to study surface and snowdrift sublimation and to assess their impacts on both the surface mass balance and the surface energy balance. Comparison to three other AWSs in Dronning Maud Land shows that sublimation has a significant influence on the surface mass balance at katabatic locations by removing 10–23 % of their total precipitation, but at the same time reveals anomalously low surface and snowdrift sublimation rates at Princess Elisabeth (18 mm w.e. yr–1 compared to 42 mm w.e. yr–1 at Svea Cross and 52 mm w.e. yr–1 at Wasa/Aboa. This anomaly is attributed to local topography, which shields the station from strong katabatic influence, and therefore on the one hand allows for a strong surface inversion to persist throughout most of the year and on the other hand causes a lower probability of occurrence of intermediately strong winds. These wind speed classes turn out to contribute most to the total snowdrift sublimation mass flux, given their ability to lift a high number of particles while still allowing for considerable undersaturation.

  18. Properties of soils in Grove Mountains, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    LI; Xiaoli(李潇丽); LIU; Xiaohan(刘小汉); JU; Yitai(琚宜太); HUANG; Feixin(黄费新)

    2003-01-01

    Three cold desert soil sites were first found in the southern Mount Harding, GroveMountains, East Antarctica. The soils are characteristics of the widespread occurrence of surfacedesert pavement, abundant water-soluble salts, strongly stained upper portion of soil profile,slightly acid and negligible organic matter content. A 1:5 soil-water extracts analysis indicates thatthe dominant cations are Mg2+ and Na+, followed by Ca2+ and K+, and the main anion is SO42-, thenCl- and NO-3. The accumulation of water-soluble salts indicates ion transportation in the frigid andarid Antarctica environment. The distribution of the salts is related to the maximum content ofmoisture and clay mineral. Clay fraction migration occurs in the soils, which is different from that ofother cold desert soils. The upper horizons of some profiles are generally stained, namely rubifica-tion, primarily because of the weathering of iron-bearing minerals. The reddish hues of cold desertsoils have been attributed to relatively high concentrations of dithionite-extractable Fe (Fed). Theweathering features of soils suggest that the soil age of this area is 0.5-3.5 Ma. No remnants ofglaciations were found on the soil sites of Mount Harding, which suggests that the Antarctic glaci-ations have not reached the soil sites since at least 0.5 Ma, even during the Last Glacial Maxi-mum.

  19. 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.

  20. Occurrence of arbuscular mycorrhizal fungi on King George Island, South Shetland Islands, Antarctica

    Directory of Open Access Journals (Sweden)

    MARISÂNGELA V. BARBOSA

    2017-08-01

    Full Text Available ABSTRACT Arbuscular mycorrhizal fungi make up an important ecological niche in ecosystems, and knowledge of their diversity in extreme environments is still incipient. The objective of this work was to evaluate the density and diversity of arbuscular mycorrhizal fungi in the soil of King George Island in the South Shetland Islands archipelago, Antarctica. For that, soil and roots of Deschampsia antarctica were collected at the brazilian research station in Antarctica. The spore density, species diversity and mycorrhizal colonization in the roots were evaluated. There was a low density of spores (27.4 ± 17.7 and root mycorrhizal colonization (6 ± 5.1%, which did not present statistical difference. Four species of arbuscular mycorrhizal fungi were identified, distributed in two genera: three species of the genus Glomus (Glomus sp1, Glomus sp2 and Glomus sp3 and one of the genus Acaulospora, which was identified at species level (Acaulospora mellea. Greater soil diversity was verified with pH 5.9 and phosphorus concentration of 111 mg dm-3, occurring two species of genus Glomus and A. mellea. Based on literature data, this may be the first record of this species of Acaulospora mellea in Antarctic soils, colonizing D. antarctica plants.

  1. Characteristics of macrobenthic assemblage from sub-littoral sediment off the Lazarev Sea, East Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Ingole, B.S.

    Comparative account of the occurrence and abundance of benthic macro-organisms collected from the Lazarev Sea in Queen Maud Land, (east Antarctica), during austral summer of 1984-85 and 1992-93 (fourth and twelfth Indian Antarctic expeditions...

  2. 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...

  3. Ocean mixing beneath Pine Island Glacier ice shelf, West Antarctica

    Science.gov (United States)

    Kimura, Satoshi; Jenkins, Adrian; Dutrieux, Pierre; Forryan, Alexander; Naveira Garabato, Alberto C.; Firing, Yvonne

    2016-12-01

    Ice shelves around Antarctica are vulnerable to an increase in ocean-driven melting, with the melt rate depending on ocean temperature and the strength of flow inside the ice-shelf cavities. We present measurements of velocity, temperature, salinity, turbulent kinetic energy dissipation rate, and thermal variance dissipation rate beneath Pine Island Glacier ice shelf, West Antarctica. These measurements were obtained by CTD, ADCP, and turbulence sensors mounted on an Autonomous Underwater Vehicle (AUV). The highest turbulent kinetic energy dissipation rate is found near the grounding line. The thermal variance dissipation rate increases closer to the ice-shelf base, with a maximum value found ˜0.5 m away from the ice. The measurements of turbulent kinetic energy dissipation rate near the ice are used to estimate basal melting of the ice shelf. The dissipation-rate-based melt rate estimates is sensitive to the stability correction parameter in the linear approximation of universal function of the Monin-Obukhov similarity theory for stratified boundary layers. We argue that our estimates of basal melting from dissipation rates are within a range of previous estimates of basal melting.

  4. 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.

  5. Surface and snowdrift sublimation at Princess Elisabeth station, East Antarctica

    Directory of Open Access Journals (Sweden)

    W. Thiery

    2012-08-01

    Full Text Available In the near-coastal regions of Antarctica, a significant fraction of the snow precipitating onto the surface is removed again through sublimation – either directly from the surface or from drifting snow particles. Meteorological observations from an Automatic Weather Station (AWS near the Belgian research station Princess Elisabeth in Dronning Maud Land, East-Antarctica, are used to study surface and snowdrift sublimation and to assess their impacts on both the surface mass balance and the surface energy balance during 2009 and 2010. Comparison to three other AWSs in Dronning Maud Land with 11 to 13 yr of observations shows that sublimation has a significant influence on the surface mass balance at katabatic locations by removing 10–23% of their total precipitation, but at the same time reveals anomalously low surface and snowdrift sublimation rates at Princess Elisabeth (17 mm w.e. yr−1 compared to 42 mm w.e. yr−1 at Svea Cross and 52 mm w.e. yr−1 at Wasa/Aboa. This anomaly is attributed to local topography, which shields the station from strong katabatic influence, and, therefore, on the one hand allows for a strong surface inversion to persist throughout most of the year and on the other hand causes a lower probability of occurrence of intermediately strong winds. This wind speed class turns out to contribute most to the total snowdrift sublimation mass flux, given its ability to lift a high number of particles while still allowing for considerable undersaturation.

  6. Paleomagnetism of King George Island, South Shetlands, Antarctica

    Science.gov (United States)

    Slotznick, S. P.; Kirschvink, J. L.; Raub, T. D.; Swanson-Hysell, N.; Edgar, L.

    2011-12-01

    During December of 2009 when the US R/V Lawrence M. Gould was iced out of the Antarctic Peninsula, we collected core and block samples from 17 different flows and dikes at three sampling areas on Weaver Peninsula and Fildes Peninsula, King George Island, South Shetland Islands, Antarctica. Two of the three sampling areas on Weaver Peninsula and Fildes Peninsula were near dikes with Ar-Ar ages of 54.6 ± 3.8 Ma and 57.4 ± 2.1 Ma respectively, close in age to the Paleocene Eocene Thermal Maximum (PETM) (Kraus 2005, Kraus et al. 2007). After removal of significant magnetically soft components by low-temperature cycling and weak AF demagnetization, the basaltic flows from the Weaver Peninsula preserve a dual-polarity characteristic remanence isolated by higher-field AF demagnetization with an in-situ magnetization of D = 166.3, I= 65.4 (n/N = 24/30, α95 = 6.31). This direction, prior to correction for bedding tilt, is indistinct from a plausible Cenozoic reversed polarity magnetization for the site, while correcting for bedding tilt results in anomalously shallow inclinations. This result implies a post-tilting thermochemical remagnetization origin for the characteristic remanence. Analyses of the baked contact, dikes, and conglomerate tests help constrain the age of this event in context of subsequent Cenozoic magmatism on King George Island. Rock magnetic and Kappabridge experiments show that the magnetic mineralogy of the samples is often dominated by magnetite, with titanomagnetite and hematite present in some flows. The results of this multi-site study of Weaver and Fildes Peninsulas add to a growing paleomagnetic database for volcanic rocks from King George Island (Valencio et al. 1979, Kraus et al. 2010, Watts et al. 1984, Nawrocki et al. 2010) and contribute to a better understanding of the complex tectonic and magmatic activity of the South Shetland Islands.

  7. Ambient noise correlation on the Amery Ice Shelf, East Antarctica

    Science.gov (United States)

    Zhan, Zhongwen; Tsai, Victor C.; Jackson, Jennifer M.; Helmberger, Don

    2014-03-01

    The structure of ice shelves is important for modelling the dynamics of ice flux from the continents to the oceans. While other, more traditional techniques provide many constraints, passive imaging with seismic noise is a complementary tool for studying and monitoring ice shelves. As a proof of concept, here we study noise cross-correlations and autocorrelations on the Amery Ice Shelf, East Antarctica. We find that the noise field on the ice shelf is dominated by energy trapped in a low-velocity waveguide caused by the water layer below the ice. Within this interpretation, we explain spectral ratios of the noise cross-correlations as P-wave resonances in the water layer, and obtain an independent estimate of the water-column thickness, consistent with other measurements. For stations with noise dominated by elastic waves, noise autocorrelations also provide similar results. High-frequency noise correlations also require a 50-m firn layer near the surface with P-wave velocity as low as 1 km s-1. Our study may also provide insight for future planetary missions that involve seismic exploration of icy satellites such as Titan and Europa.

  8. Eocene paleosols of King George Island, Maritime Antarctica

    Science.gov (United States)

    Spinola, Diogo; Portes, Raquel; Schaefer, Carlos; Kühn, Peter

    2016-04-01

    Red layers between lava flows on King George Island, Maritime Antarctica, were formed during the Eocene, which was one of the warmest periods on Earth in the Cenozoic. Our hypothesis is that these red layers are paleosols formed in periods of little or no volcanic activity. Therefore, our main objective was to identify the main pedogenic properties and features to distinguish these from diagenetic features formed after the lava emplacement. Additionally, we compared our results with volcanic soils formed under different climates to find the best present analogue. The macromorphological features indicate a pedogenic origin, because of the occurrence of well-defined horizons based on colour and structure. Micromorphological analyses showed that most important pedogenic features are the presence of biological channels, plant residues, anisotropic b-fabric, neoformed and illuvial clay and distinct soil microstructure. Although the paleosols are not strongly weathered, the geochemical data also support the pedogenic origin despite of diagenetic features as the partial induration of the profiles and zeolites filling nearly all voids in the horizons in contact with the overlying lava flow, indicating circulation of hydrothermal fluids. The macromorphological and micromorphological features of these paleosols are similar to the soils formed under seasonal climates. Thus, these paleosol features do not correspond to the other proxies (e.g. sediment, plant fossils), which indicate a wet, non-seasonal climate, as in Valdivian Forest, Chile, during the Eocene in King George Island

  9. 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.

  10. 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

  11. Antarctica

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    ANYONEwhohasbeentoAntarctica,asIhave,willviewplanetearthfromanewangle.Whenyoutravel10,000kilometers,walkoutontothevastpolarcontinentandbreatheinitscrystallineair,aheightenedsenseoflivingonaglobe,ofbelongingtoalargeruniverse,willtakerootinyourmind.AnU...

  12. Ice Surface Elevation Changes in East Antarctica from Satellite Altimetry

    Science.gov (United States)

    Zwally, H. Jay; Brenner, Anita C.; DiMarzio, John

    1998-01-01

    Estimates of the overall mass balance and seasonal and inter-annual variations in the surface mass balance are obtainable from time-series of ice surface elevations measured by satellite altimetry. Beginning in 2001, NASA's ICESat laser altimeter and lidar mission will significantly improve the range accuracy, the orbit accuracy, and the spatial coverage for measurement of ice sheet elevations (to 86 S) , as compared to previous radar altimeters designed for ocean measurements The radar altimeters on Seasat and Geosat provided ice sheet measurements to 72 S, and on ERS-1 and ERS-2 to 81 S. Although radar altimetry has significant limitations in coverage (due to loss of tracking) and accuracy over sloping surfaces, information on ice-sheet surface-elevation changes has been derived for parts of Antarctica. Recently, the accuracy of the ice measurements by Seasat (3 months of 1978) and Geosat (1985 to 1989) have been improved by new calculations of the satellite orbit heights and other altimeter corrections. Residual orbit errors and inter-satellite biases are evaluated by crossover analysis and by global adjustments to an ocean surface derived from altimeter data. The standard deviation of the orbit error is less than 9 cm, and the long-term trend in the error appears to be less than 1 cm/yr. Orbit errors can be further reduced by adjustment to the ocean surface, but false signals of several cm/yr may be also introduced by the adjustments. These false signals are caused mainly by residual errors in the altimeter corrections over the ocean, and secondary by real changes in the ocean surface elevation. Maps of ice sheet elevation changes north of 72 S are derived from Seasat-Geosat crossovers and from 4.5 years of Geosat crossovers. A notable ice thinning rate of about 50 cm/yr is found at elevations below 2200 meters between 70 and 72 S to the East of the Amery ice shelf, in both the Seasat-Geosat and Geosat-Geosat time intervals Above 2200 meters, to the ridge

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

    Directory of Open Access Journals (Sweden)

    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

  14. Detection of integron integrase genes on King George Island, Antarctica

    Institute of Scientific and Technical Information of China (English)

    Vernica Antelo; Hctor Romero; Silvia Batista

    2015-01-01

    The presence and diversity of class 1 integrase gene (intI) sequences were evaluated by PCR using previously designed primers. Two clone libraries were constructed from DNA in sediment and microbial mat samples collected on Fildes Peninsula, King George Island, Antarctica.The libraries constructed from samples collected at Halfthree Point (HP) and Norma Cove (NC) contained 62 and 36 partial intI sequences, respectively. These sequences clustered into 10 different groups with <95% amino acid identity. Alignment of the deduced amino acid sequences with those from recognized integron-encoded integrases demonstrated the presence of highly conserved motifs characteristic of intI integrases. The HP library contained 42 nucleotide sequences identical to the class 1 intI gene found in a collection of trimethoprim-resistant (Tmpr) Antarctic Enterobacter sp. isolates, previously collected in the same area. These integrons, located on plasmids, had a genetic organization similar to that of pKOX105 from Klebsiella oxytoca. The 20 remaining HP and NC library sequences were similar to integrase sequences previously determined in a metagenomic analysis of environmental samples. We have demonstrated the presence of integron integrase genes in Antarctic sediment samples. About half these genes were very similar to the class 1 integrons found in human-associated microbiota, suggesting that they originated from human-dominated ecosystems. The remaining integrase genes were probably associated with endemic bacteria.

  15. Polyphasic characterization of 10 selected ecologically relevant filamentous cyanobacterial strains from the South Shetland Islands, Maritime Antarctica.

    Science.gov (United States)

    Jancusova, Miroslava; Kovacik, Lubomir; Pereira, Antonio Batista; Dusinsky, Roman; Wilmotte, Annick

    2016-07-01

    The evolutionary relationships of 10 Antarctic cyanobacterial strains of the order Oscillatoriales isolated from King George and Deception Islands, South Shetland Islands were studied by a polyphasic approach (morphology, 16S rRNA and internal transcribed spacer sequences). The studied taxa are characteristic of coastal Antarctic biotopes, where they form distinct populations and ecologically delimited communities. They were isolated from terrestrial habitats: microbial mats in seepages; crusts on soil, rocks, bones and mosses; mud, sometimes close to bird colonies; and from guano. Based on major phenotypic features, the strains were divided into four distinct morphotypes: Leptolyngbya borchgrevinkii (A), Leptolyngbya frigida (B), Microcoleus sp. (C) and Wilmottia murrayi (D). This morphological identification was in agreement with the phylogenetic relationships. For the first time, the 16S rRNA gene sequence of a strain corresponding to the L. borchgrevinkii morphotype was determined. Morphotype B is most related to sequences assigned to L. frigida isolated from microbial mats of coastal lakes in East Antarctica. Morphotype C belongs to a cluster including strains with morphotypes corresponding to Microcoleus attenuatus, Microcoleus favosus and Microcoleus sp., which are from Antarctica and other continents. Morphotype D is grouped with sequences assigned to W. murrayi mostly isolated from Antarctica.

  16. Ultrastructure of Lobosphaera reniformis (Watanabe) Komárek et Fott (Chlorellales) from King George Island, South Shetland Islands, Antarctica

    OpenAIRE

    A. Massalski; T. Mrozińska; Olech, M.

    2014-01-01

    Lobosphaera reniformis (Wat.) Kom. et Fott (=Chlorella reniformis Wat.) so far known only from Japan, and Papua Island, was for the first time found in Antarctica (King George Island, South Shetland Islands). In laboratory cultures a complete life cycle was obtained, and most of its stages were followed by the electron microscopy. Reproduction is by morphologically different autospores. In some large vegetative cells two Golgi apparatuses lying side by side were observed.

  17. Ultrastructure of Lobosphaera reniformis (Watanabe Komárek et Fott (Chlorellales from King George Island, South Shetland Islands, Antarctica

    Directory of Open Access Journals (Sweden)

    A. Massalski

    2014-01-01

    Full Text Available Lobosphaera reniformis (Wat. Kom. et Fott (=Chlorella reniformis Wat. so far known only from Japan, and Papua Island, was for the first time found in Antarctica (King George Island, South Shetland Islands. In laboratory cultures a complete life cycle was obtained, and most of its stages were followed by the electron microscopy. Reproduction is by morphologically different autospores. In some large vegetative cells two Golgi apparatuses lying side by side were observed.

  18. 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.

  19. Tasmania in Nuna: Witness to a ~1.4 Ga East Antarctica-Laurentia Connection

    Science.gov (United States)

    Halpin, J. A.; Mulder, J. A.; Daczko, N. R.

    2015-12-01

    Most recent reconstructions of the supercontinent Nuna juxtapose the North Australian craton, Mawson continent (South Australia-East Antarctica), and Laurentia between 1.6 Ga and 1.3 Ga, but differ in their relative positioning. Tasmania (SE Australia) has not been considered in previous Nuna reconstructions. Prior to late Neoproterozoic rifting, this crustal fragment was likely part of the eastern margin of East Antarctica. The significance of Tasmania's position within Nuna has recently been highlighted with the discovery that the majority of a >10-km-thick marine shelfal package exposed in northwest Tasmania (Rocky Cape Group) was deposited between 1.45 and 1.30 Ga. The detrital zircon signatures of these strata are distinct from other Mesoproterozoic basins in Australia, and instead closely resemble time-equivalent upper parts of the Belt-Purcell Basin of Laurentia, suggesting correlations within Nuna. We investigate the provenance of the Rocky Cape Group quartzites by comparing new detrital zircon U-Pb-Hf isotopic data to an extensive compilation of zircon data from Australia, East Antarctica, and Laurentia. Our analysis demonstrates that the Rocky Cape Group is unlikely to have been sourced from any geological terrane exposed in present-day Australia. Instead, zircon isotopic signatures from basement terranes in Laurentia and East Antarctica show striking similarities to the Rocky Cape Group detrital signature. Paleocurrent data indicate a northwest-southeast-trending paleoshoreline
and suggest that the majority of sediment was sourced from Paleoproterozoic crust in SW Laurentia, which was to the southeast (present-day coordinates) of Tasmania. These new data support a SWEAT-like (southwest United States-East Antarctica) configuration for Nuna. We suggest that rifting propagated southward from ca. 1.4 Ga, leaving a thinned continental connection between East Antarctica and southwest Laurentia onto which the lower-middle RCG was deposited prior to 1.3 Ga.

  20. Rifts in the tectonic structure of East Antarctica

    Science.gov (United States)

    Golynsky, Dmitry; Golynsky, Alexander

    2010-05-01

    It was established that riftogenic and/or large linear tectonic structures in East Antarctica are distributed with a steady regularity with average distance between them about 650 km. All these structures (13) represent objects of undoubted scientific and practical interest and might be considered as immediate objects for conducting integrated geological and geophysical investigations. Analysis and generalization of the RADARSAT satellite system imagery and radio-echosounding survey data collected in the eastern part of Princess Elizabeth Land allow us to distinguish spatial boundaries of previously unknown continental rift system that was proposed to name Gaussberg (Golynsky & Golynsky, 2007). The rift is about 500 km long, and taking into consideration its western continuation in the form of short (fragmented) faults, may exceed 700 km. The elevation difference between depressions and horsts reaches 3 km. The rift structure consists of two sub-parallel depressions separated by segmented horst-like rises (escarpments). Deep depressions within the rift reach more than 800 m bsl near the West Ice Shelf and within the central graben occupied by the Phillipi Glacier. The width of the Gaussberg Rift system varies from 60 km in the south-western area to 150 km near the West Ice Shelf. The Gaussberg rift is considered as a part of the Lambert rift system, which has a complicated structure clearly recognized over both the continent and also its margin. The Gaussberg rift probably exploited a weak zone between the Proterozoic mobile belt and the Archaean Vestfold-Rauer cratonic block. Supposedly it initiated at the turn of Jurassic and Permian epoch or a little bit earlier as in case of the Lambert rift where the Permian graben formation with coal-bearing deposits predetermined the subsequent development of submeridional rift zone. The Gaussberg and also the Scott rift developed in the Queen Marie Land, may be considered as continuations of the Mahanadi Valley rift and

  1. A two thousand year annual record of snow accumulation rates for Law Dome, East Antarctica

    Directory of Open Access Journals (Sweden)

    J. Roberts

    2014-11-01

    AD 663–704, AD 933–975 and AD 1429–1468 were below average. The calculated snow accumulation rates show good correlation with atmospheric reanalysis estimates, and significant spatial correlation over a wide expanse of East Antarctica, demonstrating that the Law Dome record captures larger scale variability across a large region of East Antarctica well beyond the immediate vicinity of the Law Dome summit. Spectral analysis reveals periodicities in the snow accumulation record which may be related to ENSO and Interdecadal Pacific Oscillation frequencies.

  2. Colonization and demographic structure of Deschampsia antarctica and Colobanthus quitensis along an altitudinal gradient on Livingston Island, South Shetland Islands, Antarctica

    Directory of Open Access Journals (Sweden)

    María Luisa Vera

    2011-05-01

    Full Text Available The colonization capacity and demographic structure of populations of Deschampsia antarctica and Colobanthus quitensis were studied in different microhabitats between 10 and 147 m a.s.l. on Livingston Island, South Shetland Islands, near the Spanish Antarctic base Juan Carlos I, in February 2002. At the highest site (147 m a.s.l., mean temperatures were about 1°C lower than at sea level. Both species are less common in inland areas and at the highest altitudes only occur at restricted sites that are frequently snow-free in the early austral summer. The diameters of the largest plants (C. quitensis cushions 7–8 cm; D. antarctica tufts 10–11 cm in the populations growing at the highest altitudes (110 and 147 m a.s.l. suggest that these populations were established about 24–28 years ago. The largest diameter plants (Deschampsia 20 cm; Colobanthus 18 cm were found at the lowest altitudes on deep soil. The presence of numerous seedlings and young individuals on the periphery of populations established several years ago or at recently colonized sites suggests an active process of expansion. There were more emerged seedlings of C. quitensis than of D. antarctica, but the density of established individuals was higher for D. antarctica, suggesting these species have different demographic strategies.

  3. Surface and snowdrift sublimation at Princess Elisabeth station, East Antarctica

    NARCIS (Netherlands)

    Thiery, W.; Gorodetskaya, I.V.; Bintanja, R.; van Lipzig, N.P.M.; van den Broeke, M.R.; Reijmer, C.H.; Kuipers Munneke, P.

    2012-01-01

    In the near-coastal regions of Antarctica, a significant fraction of the snow precipitating onto the surface is removed again through sublimation – either directly from the surface or from drifting snow particles. Meteorological observations from an Automatic Weather Station (AWS) near the Belgian r

  4. 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

  5. Climate Controlled Sedimentation in Maxwell Bay, King George Island, Antarctica

    Science.gov (United States)

    Hass, H.; Kuhn, G.; Wittenberg, N.; Woelfl, A.; Betzler, C.

    2012-12-01

    Climatic change in Antarctica is strongest over the Antarctic Peninsula where in places the annual mean temperatures increased by 0.5 K per decade through the past 60 years. The impact of this warming trend is clearly visible in the form of retreating glaciers and melting ice sheets, loss of sea ice and strong meltwater discharge into the coastal zone. While it is generally accepted that the rapidity of the present climate change bears a significant anthropogenic aspect, it is not clear whether the effects caused by the warming trend are exceptional and unprecedented or whether the reaction of the environment is similar to that of earlier climate phases such as the Medieval Warm Period (MWP) about 1,000 years ago. One of the major goals of the joint international research project IMCOAST is to investigate the strength of the recent warming trend and its impact on the marine environment of the West Antarctic Peninsula (WAP). The study we present here reveals the Upper Holocene climatic history based on high-resolution sediment cores from Maxwell Bay (King George Island, WAP) and information on the actual processes triggered or altered by the recent warming trend based on sedimentologic and hydroacoustic investigations in Potter Cove, a tributary fjord to Maxwell Bay. Long sediment cores from Maxwell Bay reveal grain-size changes that can be linked to cold and warm phases such as the Little Ice Age (LIA) and the MWP. Generally, warm phases are finer grained than cold phases as a result of longer and stronger melting processes during the warm phases. It is suggested that meltwater plumes carry fine-grained sediment out of the surrounding fjords into Maxwell Bay where it settles in suitable areas to produce sediments that have a modal value around 16 μm. This mode is largely absent in sediments deposited during e.g. the LIA. However, post LIA sediments are depleted in the 16 μm-mode sediment suggesting slightly different conditions during the last century. One reason

  6. Observations of volcanic earthquakes and tremor at Deception Island - Antarctica

    Directory of Open Access Journals (Sweden)

    J. Morales

    1999-06-01

    Full Text Available Deception Island - South Shetlands, Antarctica is site of active volcanism. Since 1988 field surveys have been carried out with the aim of seismic monitoring, and in 1994 a seismic array was set up near the site of the Spanish summer base in order to better constrain the source location and spectral properties of the seismic events related to the volcanic activity. The array was maintained during the Antarctic summer of 1995 and the last field survey was carried out in 1996. Data show the existence of three different groups (or families of seismic events: 1 long period events, with a quasi-monochromatic spectral content (1-3 Hz peak frequency and a duration of more than 50 s, often occurring in small swarms lasting from several minutes to some day; 2 volcanic tremor, with a spectral shape similar to the long period events but with a duration of several minutes (2-10; 3 hybrid events, with a waveform characterised by the presence of a high frequency initial phase, followed by a low frequency phase with characteristics similar to those of the long period events. The high frequency phase of the hybrid events was analysed using polarisation techniques, showing the presence of P waves. This phase is presumably located at short epicentral distances and shallow source depth. All the analysed seismic events show back-azimuths between 120 and 330 degrees from north (corresponding to zones of volcanic activity showing no seismic activity in the middle of the caldera. Particle motion, Fourier spectral and spectrogram analysis show that the low frequency part of the three groups of the seismic signals have similar patterns. Moreover careful observations show that the high frequency phase which characterises the hybrid events is present in the long period and in the tremor events, even with lower signal to noise ratios. This evidence suggests that long period events are events in which the high frequency part is simply difficult to observe, due to a very

  7. 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.

  8. A positive test of East Antarctica-Laurentia juxtaposition within the Rodinia supercontinent.

    Science.gov (United States)

    Goodge, J W; Vervoort, J D; Fanning, C M; Brecke, D M; Farmer, G L; Williams, I S; Myrow, P M; DePaolo, D J

    2008-07-11

    The positions of Laurentia and other landmasses in the Precambrian supercontinent of Rodinia are controversial. Although geological and isotopic data support an East Antarctic fit with western Laurentia, alternative reconstructions favor the juxtaposition of Australia, Siberia, or South China. New geologic, age, and isotopic data provide a positive test of the juxtaposition with East Antarctica: Neodymium isotopes of Neoproterozoic rift-margin strata are similar; hafnium isotopes of approximately 1.4-billion-year-old Antarctic-margin detrital zircons match those in Laurentian granites of similar age; and a glacial clast of A-type granite has a uraniun-lead zircon age of approximately 1440 million years, an epsilon-hafnium initial value of +7, and an epsilon-neodymium initial value of +4. These tracers indicate the presence of granites in East Antarctica having the same age, geochemical properties, and isotopic signatures as the distinctive granites in Laurentia.

  9. Isolation and characterization of Campylobacter spp. from Antarctic fur seals (Arctocephalus gazella) at Deception Island, Antarctica.

    Science.gov (United States)

    García-Peña, F J; Pérez-Boto, D; Jiménez, C; San Miguel, E; Echeita, A; Rengifo-Herrera, C; García-Párraga, D; Ortega-Mora, L M; Pedraza-Díaz, S

    2010-09-01

    The presence of Campylobacter spp. was investigated in 41 Antarctic fur seals (Arctocephalus gazella) and 9 Weddell seals (Leptonychotes weddellii) at Deception Island, Antarctica. Infections were encountered in six Antarctic fur seals. The isolates, the first reported from marine mammals in the Antarctic region, were identified as Campylobacter insulaenigrae and Campylobacter lari.

  10. A preliminary study of freshwater meiofaunal communities at Greenwich Island, South Shetland Islands, Antarctica

    Institute of Scientific and Technical Information of China (English)

    Soraya J. Silva; Minerva Cordovés; Nory González; Leinny González

    2015-01-01

    Meiofaunal communities of three small, shallow freshwater habitats sampled during the austral summer of 2013 in Greenwich Island, South Shetland Islands, Antarctica, are reported. Communities are dominated by tardigrades (85%), nematodes (11%), and rotifers (3%). Collembola, Oligochaeta, crustacean larvae (nauplii) and unidentified organisms account for 0.3%. Total meiofaunal densities reach 11 770 ind∙cm-2, with mean densities (ind∙cm−2) of 1 365.83 ± 2 716.65 (Zone A), 523.67 ± 1 166.48 (Zone B) and 72.17 ± 110.78 (Zone C). Given the age of freshwater habitats, and the general lack of higher-trophic level predatory taxa, those species we report are likely early stage colonizers, and these communities are at an early stage of ecological succession. Non-parametrical analysis revealed the main variables influencing meiofaunal density and distribution are related to granulometric characteristics of sediments and microphytobenthic biomass. There were close relationships between meiofaunal abundance and microphytobenthic biomass, which indicates that benthic microalgae significantly influence meiofaunal distribution. A strong correlation between nematode abundance and the percentage of silt, clay and carbon in the sediment was also shown by canonical correspondence analysis and Spearman rank correlation.

  11. Experimental culture of non-indigenous Juncus bufonius from King George Island, South Shetland Island, Antarctica

    Institute of Scientific and Technical Information of China (English)

    Marely Cuba-Díaz; Eduardo Fuentes; Mauricio Rondanelli-Reyes; Ángela Machuca

    2015-01-01

    Juncus bufonius L. (Juncaceae) is recognized by the US Department of Agriculture as a weed or invasive plant. Recently, we reported on J. bufonius L. var. bufonius associated with the native vascular plants Deschampsia antarctica and Colobanthus quitensis in the environs of the Polish Arctowski Station, King George Island, in the Maritime Antarctica. In this study, we evaluated the developmental stages and morphological characteristics of J. bufonius plants cultivated in controlled conditions beginning with seeds obtained from plants of the Antarctic population. Germination occurred at 3 weeks and the germination percentage was low (22.5%). The average time between the anthesis and seed formation was 7 weeks, similar to that reported for other species in the Juncaceae. According to data reported in the literature, Antarctic individuals were significantly smaller than their relatives growing in other conditions, except for the number of inflorescences. The morphological characteristics of a species vary according to its distribution and the edaphoclimatic environment where it occur; cosmopolitan plants shuch as J. bufonius also have reduced stature in cold environments. The low percentage germination may have been due to water availability in the plant chamber in which the study was conducted. J. bufonius is intolerant of dry environments, and once it suffers hydric stress its recovery is very low; thus, a moister environment could be beneficial. J. bufonius has become established amongst native vegetation near Arctowski Station and without careful control or eradication; it may have the potential to spread far beyond the site, as has happened with the alien grass Poa annua as human disturbance and climate warming increase.

  12. A comparison of basal reflectivity and ice velocity in East Antarctica

    Directory of Open Access Journals (Sweden)

    R. W. Jacobel

    2010-08-01

    Full Text Available Ground-based radio echo sounding data acquired along the 1700 km US-ITASE traverse have been used to determine ice attenuation and relative basal reflectivity across the major catchments funneling ice from East Antarctica to the Ross Ice Shelf. We find that basal reflectivity varies locally by up to 40 dB which we interpret as due to changes in the phase state at the bed. Some, though not all, areas of high local reflectivity are observed to have flat-lying bed reflections indicative of sub-glacial lakes. We compare basal reflectivity to ice balance velocity and find a general association of higher flow speeds with high radar reflection strength. This set of observations from two independent remotely sensed geophysical data sets extends the range of field observations to the interior of East Antarctica and confirms the importance of basal lubrication on modulating the ice dynamics of the largest ice sheet on the planet.

  13. A comparison of basal reflectivity and ice velocity in East Antarctica

    Directory of Open Access Journals (Sweden)

    R. W. Jacobel

    2010-10-01

    Full Text Available Ground-based radio echo sounding data acquired along the 1700 km US-ITASE traverse have been used to determine ice attenuation and relative basal reflectivity across the major catchments funneling ice from East Antarctica to the Ross Ice Shelf. We find that basal reflectivity varies locally by up to 40 dB which we interpret as due to changes in the phase state at the bed. Some, though not all, areas of high local reflectivity are observed to have flat-lying bed reflections indicative of sub-glacial lakes. We compare basal reflectivity to ice balance velocity and find a general association of higher flow speeds with high radar reflection strength. This set of observations from two independent remotely sensed geophysical data sets extends the range of field observations to the interior of East Antarctica and confirms the importance of basal lubrication on modulating the ice dynamics of the largest ice sheet on the planet.

  14. Evidence for warmer event from quartz grains in the soil of Grove Mountains, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    Yan Xin; Li Xiaoli; Liu Xiaohan; Zhang Ru-fan

    2005-01-01

    The cold desert soil has been discovered at first time in southern ridgeof Mount Harding, Grove Mountains of interior East Antarctica Ice Sheet. Based on the micro structural observation, dominant characteristics of quartz grains include: distinct surface stria and fractures, and clean features of frost action at both of crystal margins and micro crannies of quartz grains. These features show a pedogenesis environment of few water, short transportation and frost action, revealing a warmer climatic event existed in this region.

  15. Erosion-driven uplift in the Gamburtsev Subglacial Mountains of East Antarctica.

    OpenAIRE

    Paxman, G. J. G.; Watts, A. B.; Ferraccioli, F.; Jordan, T.A.; R. E. Bell; Jamieson, S.S.R.; Finn, C A

    1999-01-01

    The relative roles of climate and tectonics in mountain building have been widely debated. Central to this debate is the process of flexural uplift in response to valley incision. Here we quantify this process in the Gamburtsev Subglacial Mountains, a paradoxical tectonic feature in cratonic East Antarctica. Previous studies indicate that rifting and strike-slip tectonics may have provided a key trigger for the initial uplift of the Gamburtsevs, but the contribution of more recent valley inci...

  16. Preliminary report on metamict cerianite from Nesoya, Lutzow-Holmbunkta, East Antarctica

    OpenAIRE

    Matsumoto,Yukio/Sakamoto,Arata

    1982-01-01

    Mineralogical studies of a blackish mineral with strong radioactivity from microcline pegmatites of Nesoya, Lutzow-Holmbukta, East Antarctica, were performed. This mineral has been completely or almost completely transformed into a metamict state. However, in a heat treatment (1000℃, 7 hours), the powder pattern is identical with cerianite, and the unit cell dimension calculated from the powder X-ray diffraction data is α_0=5.451A. According to the qualitative analysis by an electron probe X-...

  17. Monitoring atmospheric nitrous oxide background concentrations at Zhongshan Station, east Antarctica.

    Science.gov (United States)

    Ye, Wenjuan; Bian, Lingen; Wang, Can; Zhu, Renbin; Zheng, Xiangdong; Ding, Minghu

    2016-09-01

    At present, continuous observation data for atmospheric nitrous oxide (N2O) concentrations are still lacking, especially in east Antarctica. In this paper, nitrous oxide background concentrations were measured at Zhongshan Station (69°22'25″S, 76°22'14″E), east Antarctica during the period of 2008-2012, and their interannual and seasonal characteristics were analyzed and discussed. The mean N2O concentration was 321.9nL/L with the range of 320.5-324.8nL/L during the five years, and it has been increasing at a rate of 0.29% year(-1). Atmospheric N2O concentrations showed a strong seasonal fluctuation during these five years. The concentrations appeared to follow a downtrend from spring to autumn, and then increased in winter. Generally the highest concentrations occurred in spring. This trend was very similar to that observed at other global observation sites. The overall N2O concentration at the selected global sites showed an increasing annual trend, and the mean N2O concentration in the Northern Hemisphere was slightly higher than that in the Southern Hemisphere. Our result could be representative of atmospheric N2O background levels at the global scale. This study provided valuable data for atmospheric N2O concentrations in east Antarctica, which is important to study on the relationships between N2O emissions and climate change.

  18. The lichen and bryophyte vegetation of Cuverville Island, Antarctica

    NARCIS (Netherlands)

    de Leeuw, C; Aptroot, A; van Zanten, B

    1998-01-01

    In the Antarctic summer of 1993 the vegetation of Cuverville Island, a small island near the west coast of the Antarctic Peninsula, was mapped and described. Eleven different plant communities of algae, lichens, bryophytes and spermatophytes have been distinguished. The 51 species Vary from endemic

  19. Elders Point East Marsh Island Restoration Monitoring Data Analysis

    Science.gov (United States)

    2017-09-21

    ER D C/ EL C R- 17 -1 Elders Point East Marsh Island Restoration Monitoring Data Analysis En vi ro nm en ta l L ab or at or y David...Point East Marsh Island Restoration Monitoring Data Analysis David S. Davis and David Yozzo HDR 1 International Boulevard Suite 1000 Mahwah, NJ...Engineers Washington, DC 20314-1000 Under Project #454750, “Elders Point East Marsh Island Restoration: Monitoring Data Analysis ” ERDC/EL CR-17-1 ii

  20. 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.

  1. Annually-resolved temperature reconstructions of the past 2000 years from Dome-Fuji, East Antarctica

    Science.gov (United States)

    Motizuki, Yuko; Takahashi, Kazuya; Nakai, Yoichi; Motoyama, Hideaki

    2016-04-01

    We present annually-resolved temperature and SST reconstructions of the past 2000 years based on water (oxygen and deuterium) isotope measurement on a shallow ice core drilled in 2010 at Dome Fuji station, East Antarctica. These time series records will be an essential contribution to the PAGES 2k project from sparse data area in Antarctica. Dome Fuji station is located on a summit of Dronning Maud Land at an altitude of 3810 m a.s.l. (above sea level) (77o19'01'' S, 39o42'12'' E) in East Antarctica. The 10 m depth mean snow temperature at Dome Fuji is -57.3oC1). The inland area around Dome Fuji has been recognized to be especially unique: The snow and ice there contain much stratospheric information. The direct evidence for this comes from tritium contents originated from the nuclear bomb tests in the 1960s; the tritium fallout at the Dome Fuji site is outstandingly high among 16 snow pit samples widely collected over Antarctica2). To date the concerned Dome Fuji ice core, we applied volcanic signature matching to transfer the West Antarctic Ice Sheet (WAIS) Divide ice core chronology constructed by annual layer counting as used in the study by Sigl et al. (2014)3). In our presentation, we confine ourselves to discuss the oscillation periodicity that we observed in the oxygen isotope record in our data: The periods of approximately 10, 20, and 200 years were found. We will present the time series analyses for this in detail, and will discuss the origin of this periodicity. References: 1) Kameda, T., Motoyama, H., Fujita, S., and Takahashi, S.: "Past temporal and spatial variability of surface mass balance at Dome Fuji", East Antarctica, by the stake method from 1995 to 2006, J. Glaciol., 54, 107-116, 2008. 2) Fourre, E., Jean-Baptiste, P., Dapoigny, A., Baumier, D., Petit, J.-R., and Jouzel, J.: "Past and recent tritium levels in Arctic and Antarctic polar caps", Earth Planet. Sc. Lett., 245, 56-64, 2006. 3) Sigl, M., J. McConnell, M. Toohey, M. Curran, S. Das, R

  2. Chlorinated biphenyls and pesticides in migrating and resident seabirds from East and West Antarctica.

    Science.gov (United States)

    Corsolini, Simonetta; Borghesi, Nicoletta; Ademollo, Nicoletta; Focardi, Silvano

    2011-11-01

    The unhatched eggs of the following seabirds were analyzed to quantify PCBs, hexachlorobenzene (HCB), α-, β-, γ-, δ-hexachlorocyclohexanes (HCHs), o,p' and p,p' isomers of DDT, DDD and DDE: resident Adèlie (Pygoscelis adèliae, ADPE) and Emperor (Aptenodytes forsteri, EMPE) penguins, migrating snow petrel (Pagodroma nivea, SNPT) and South Polar skua (Catharacta maccormicki, SPSK) from the Ross Sea (East Antarctica); and migrating Brown skua (Catharacta antartica, BRSK) and resident ADPE from the Brainsfield Strait (West Antarctica). The general aims were to evaluate the contaminant accumulation in eggs of migrating and resident species in the two study areas, and to compare levels in penguins and skuas nesting in East and West Antarctica. PCB congener and HCH and DDT isomer profiles were also assessed. Comparisons were evaluated using seven PCB congeners (IUPAC nos. 28, 52, 101, 118+149, 138, 153, and 180), p,p'-DDE, ΣDDTs, and ΣHCHs. Higher contaminant concentrations were detected in migrating seabirds (South polar skua and brown skua)>sub-Antarctic species (snow petrel)>Antarctic species (penguins) from both the sampling sites, suggesting contamination events at lower latitudes for those birds migrating northward. HCHs showed the lowest concentrations in all species (from 0.03±0.03 ng/g wet wt in SPSK to 1.81±1.23 ng/g wet wt in ADPE from West Antarctica), and PCBs were the most abundant contaminants (from 4.34±2.15 ng/g wet wt. in EMPE to 53.41±19.61 ng/g wet wt. in brown skua). Among pesticides, it is relevant the detection of p,p'-DDT in Adèlie penguin from West Antarctica and in both species of skua; the detection of this pesticide can confirm its actual use in certain malaria-endemic countries from where it is transferred through the long range transport to the polar regions. Contaminants did not show any significant temporal trend during a ten year time span, from 1994/95 to 2004/05, in organisms collected in East Antarctica and they did not

  3. Eocene relatives of cod icefishes (Perciformes: Notothenioidei) from Seymour Island, Antarctica

    DEFF Research Database (Denmark)

    Bieńkowska-Wasiluk, Małgorzata; Bonde, Niels Christensøn; Møller, Peter Rask

    2013-01-01

    Fragmentary skull bones and vertebra from the Upper Eocene La Meseta Formation on Seymour (Marambio) Island, Antarctic Peninsula have been described as gadiform fishes, informally named “Mesetaichthys”. Here we describe jaws as Mesetaichthys jerzmanskae n. g. and n. sp., and refer this taxon to t...... of notothenioids in connection with the deterioration of the climate in Antarctica during the Late Eocene-Oligocene is discussed....

  4. A review of scientific research trends within ASPA No. 126 Byers Peninsula, South Shetland Islands, Antarctica

    OpenAIRE

    2013-01-01

    Byers Peninsula, Livingston Island, was one of the first sites in Antarctica designated for environmental conservation and scientific protection. Research on Byers Peninsula has been predominantly international, with 88 indexed publications (93% of them published during last 20 years) from 209 authors affiliated to 110 institutions from 22 nations, all of which are signatories to the Antarctic Treaty. Palaeontological research represented 20% of the published articles. The variety of freshwat...

  5. The environmental impact of sewage and wastewater outfalls in Antarctica: An example from Davis station, East Antarctica.

    Science.gov (United States)

    Stark, Jonathan S; Corbett, Patricia A; Dunshea, Glenn; Johnstone, Glenn; King, Catherine; Mondon, Julie A; Power, Michelle L; Samuel, Angelingifta; Snape, Ian; Riddle, Martin

    2016-11-15

    We present a comprehensive scientific assessment of the environmental impacts of an Antarctic wastewater ocean outfall, at Davis station in East Antarctica. We assessed the effectiveness of current wastewater treatment and disposal requirements under the Protocol on Environmental Protection to the Antarctic Treaty. Macerated wastewater has been discharged from an outfall at Davis since the failure of the secondary treatment plant in 2005. Water, sediment and wildlife were tested for presence of human enteric bacteria and antibiotic resistance mechanisms. Epibiotic and sediment macrofaunal communities were tested for differences between sites near the outfall and controls. Local fish were examined for evidence of histopathological abnormalities. Sediments, fish and gastropods were tested for uptake of sewage as measured by stable isotopes of N and C. Escherichia coli carrying antibiotic resistance determinants were found in water, sediments and wildlife (the filter feeding bivalve Laternula eliptica). Fish (Trematomus bernacchii) within close proximity to the outfall had significantly more severe and greater occurrences of histopathological abnormalities than at controls, consistent with exposure to sewage. There was significant enrichment of (15)N in T. bernacchii and the predatory gastropod Neobuccinum eatoni around the outfall, providing evidence of uptake of sewage. There were significant differences between epibiotic and sediment macrofaunal communities at control and outfall sites (environmental drivers such as sea ice. The combined evidence indicated that the discharge of wastewater from the Davis outfall is causing environmental impacts. These findings suggest that conditions in Antarctic coastal locations, such as Davis, are unlikely to be conducive to initial dilution and rapid dispersal of wastewater as required under the Protocol on Environmental Protection to the Antarctic Treaty. Current minimum requirements for wastewater treatment and disposal in

  6. The tectonic development and erosion of the Knox Subglacial Sedimentary Basin, East Antarctica

    Science.gov (United States)

    Maritati, A.; Aitken, A. R. A.; Young, D. A.; Roberts, J. L.; Blankenship, D. D.; Siegert, M. J.

    2016-10-01

    Sedimentary basins beneath the East Antarctic Ice Sheet (EAIS) have immense potential to inform models of the tectonic evolution of East Antarctica and its ice-sheet. However, even basic characteristics such as thickness and extent are often unknown. Using airborne geophysical data, we resolve the tectonic architecture of the Knox Subglacial Sedimentary Basin in western Wilkes Land. In addition, we apply an erosion restoration model to reconstruct the original basin geometry for which we resolve geometry typical of a transtensional pull-apart basin. The tectonic architecture strongly indicates formation as a consequence of the rifting of India from East Gondwana from ca. 160-130 Ma, and we suggest a spatial link with the western Mentelle Basin offshore Western Australia. The erosion restoration model shows that erosion is confined within the rift margins, suggesting that rift structure has strongly influenced the evolution of the Denman and Scott ice streams.

  7. Distribution and Diversity of Soil Microfauna from East Antarctica: Assessing the Link between Biotic and Abiotic Factors

    OpenAIRE

    Alejandro Velasco-Castrillón; Schultz, Mark B.; Federica Colombo; 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 fro...

  8. Expressed sequence tag analysis of Antarctic hairgrass Deschampsia antarctica from King George Island, Antarctica.

    Science.gov (United States)

    Lee, Hyoungseok; Cho, Hyun Hee; Kim, Il-Chan; Yim, Joung Han; Lee, Hong Kum; Lee, Yoo Kyung

    2008-04-30

    Deschampsia antarctica is the only monocot that thrives in the tough conditions of the Antarctic region. It is an invaluable resource for the identification of genes associated with tolerance to various environmental pressures. In order to identify genes that are differentially regulated between greenhouse-grown and Antarctic field-grown plants, we initiated a detailed gene expression analysis. Antarctic plants were collected and greenhouse plants served as controls. Two different cDNA libraries were constructed with these plants. A total of 2,112 cDNA clones was sequenced and grouped into 1,199 unigene clusters consisting of 243 consensus and 956 singleton sequences. Using similarity searches against several public databases, we constructed a functional classification of the ESTs into categories such as genes related to responses to stimuli, as well as photosynthesis and metabolism. Real-time PCR analysis of various stress responsive genes revealed different patterns of regulation in the different environments, suggesting that these genes are involved in responses to specific environmental factors.

  9. Evidence for plant viruses in the region of Argentina Islands, Antarctica.

    Science.gov (United States)

    Polischuk, Valery; Budzanivska, Irena; Shevchenko, Tetyana; Oliynik, Svitlana

    2007-02-01

    This work focused on the assessment of plant virus occurrence among primitive and higher plants in the Antarctic region. Sampling occurred during two seasons (2004/5 and 2005/6) at the Ukrainian Antarctic Station 'Academician Vernadskiy' positioned on Argentina Islands. Collected plant samples of four moss genera (Polytrichum, Plagiatecium, Sanionia and Barbilophozia) and one higher monocot plant species, Deschampsia antarctica, were further subjected to enzyme-linked immunosorbent assay to test for the presence of common plant viruses. Surprisingly, samples of Barbilophozia and Polytrichum mosses were found to contain antigens of viruses from the genus Tobamovirus, Tobacco mosaic virus and Cucumber green mottle mosaic virus, which normally parasitize angiosperms. By contrast, samples of the monocot Deschampsia antarctica were positive for viruses typically infecting dicots: Cucumber green mottle mosaic virus, Cucumber mosaic virus and Tomato spotted wilt virus. Serological data for Deschampsia antarctica were supported in part by transmission electron microscopy observations and bioassay results. The results demonstrate comparatively high diversity of plant viruses detected in Antarctica; the results also raise questions of virus specificity and host susceptibility, as the detected viruses normally infect dicotyledonous plants. However, the means of plant virus emergence in the region remain elusive and are discussed.

  10. Molecular organic geochemical peculiarities of lacustrine core sediments in Fildes Peninsula, King George Island,Antarctica

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The peculiarities of lipids in lacustrine core sediments from Fildes Peninsula, King George Island, Antarctica, are reported. The origin of high-molecular-weight n-alkanes, alkenes,fatty acids, alcohols is supposed to be related to the abundant moss occurring in the sediments.Abundant iso-and anteiso-fatty acids that occur in the sediments indicate a relatively strong bacterial activity in non-ice-cover zone than in other regions in Antarctica. The C18:2 unsaturated fatty acids mainly originate from autochthonous algae in the sediment pool, and the C18:2/C18:0ratios in the profile are controlled more by paleotemperatures than source assemblies. Long-chain alkenones were identified in freshwater lacustrine sediment in Antarctica for the first time, of which Prymnesiophyceae is assumed to be the source organism. High relative abundance of C37:4honologue in long-chain alkenone well correlates to the severely cold climate in Antarctica.

  11. 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

  12. Geoologic controls on the architecture of the Antarctic Ice Sheet's basal interface: New results from West and East Antarctica from long range geophysics (Invited)

    Science.gov (United States)

    Young, D. A.; Blankenship, D. D.; Greenbaum, J. S.; Richter, T.; Aitken, A.; Siegert, M. J.; Roberts, J. L.

    2013-12-01

    The ice-rock interface underlying the Antarctic Ice Sheet was shaped by interactions between underlying gondwanan geology and the overlying ice sheet. The ice sheet now preserves from sedimentary infill an incredibly rugged terrain which now plays a critical role in shaping subglacial hydrology, and thus shape ice sheet behavior. This terrain can by imaged through aerogeophysical means, in particular through ice penetrating radar, while airborne potential fields measurements provide insight into the geological framework that controlled erosion. Over the post IPY era, the density of airborne coverage is only now reaching the point where small scale structure can be identified and placed in context. Of particular importance is understanding the formation of focused erosional valleys, 30-50 km wide, representing now buried subglacial fjords. After initial data from the GIMBLE project in West Antarctica, and five years of sustained long range ICECAP surveys over East Antarctica , we now have a better view of the diversity of these features. The local erosion of these valleys, often cutting through significant topographic barriers, irregularly samples the underlying geology, provided a complex story in the sediment to the Antarctic margin. These valleys now provide the subglacial conduits for significant ice sheet catchments, in particular for subglacial water, including the inland catchments of DeVicq, Thwaites, and Pine Island Glaciers in West Antarctica, and Denman Glacier, Totten Glacier, Byrd Glacier and Cook Ice Shelf in East Antarctica. We find that these features, now sometimes hundreds of kilometers inland of the modern grounding line, often nucleate on or are aligned with structure inherited from the assembly of the Antarctic continent. While many of these features currently host active outlet glaciers or their tributaries, some do not, implying avenues for ice sheet change. In West Antarctica, we find a new deep connection between the coast and interior basin

  13. Advances in seismic monitoring at Deception Island volcano (Antarctica since the International Polar Year

    Directory of Open Access Journals (Sweden)

    Enrique Carmona

    2014-06-01

    Full Text Available Deception Island is an active volcano located in the south Shetland Islands, Antarctica. It constitutes a natural laboratory to test geophysical instruments in extreme conditions, since they have to endure not only the Antarctic climate but also the volcanic environment. Deception is one of the most visited places in Antarctica, both by scientists and tourists, which emphasize the importance of volcano monitoring. Seismic monitoring has been going on since 1986 during austral summer surveys. The recorded data include volcano-tectonic earthquakes, long-period events and volcanic tremor, among others. The level of seismicity ranges from quiet periods to seismic crises (e.g. 1992-1993, 1999. Our group has been involved in volcano monitoring at Deception Island since 1994. Based on this experience, in recent years we have made the most of the opportunities of the International Polar Year 2007-2008 to introduce advances in seismic monitoring along four lines: (1 the improvement of the seismic network installed for seismic monitoring during the summer surveys; (2 the development and improvement of seismic arrays for the detection and characterization of seismo-volcanic signals; (3 the design of automated event recognition tools, to simplify the process of data interpretation; and (4 the deployment of permanent seismic stations. These advances help us to obtain more data of better quality, and therefore to improve our interpretation of the seismo-volcanic activity at Deception Island, which is a crucial step in terms of hazards assessment.

  14. Radioactive concentrations of the Livingston Island soils (Antarctica). Dosimetry considerations

    Energy Technology Data Exchange (ETDEWEB)

    Baeza, A.; Rio, M. del; Paniagua, J.M. (Facultad de Veterinaria, Ctra. de Trujillo, Caceres (Spain)); Navarro, E.; Rodriguez, M.J.; Sanchez, F. (Centro Mixto Univ. de Valencia (Spain). Inst. de Fisica Corpuscular)

    1994-06-01

    The radioactive concentrations of natural and man-made ([sup 90]Sr and [sup 137]Cs) emitters were studied in soil samples collected from an area of 2.3 km[sup 2] around the Spanish Antarctic Base on Livingston Island in the South Shetlands. The levels of radiation detected, for natural radioisotopes, as well as consequently the measured levels of effective dose equivalent rate, are of the order of half the values commonly assigned as world averages for these magnitudes. (Author).

  15. Marine ice sheet collapse and terrestrial climate stability in Pliocene East Antarctica

    Science.gov (United States)

    Hill, Daniel; Smith, Yvonne

    2016-04-01

    New marine evidence is emerging of ice sheet collapses in vulnerable marine basins of the East Antarctica during warm periods of the Pliocene. This contrasts the long-standing terrestrial evidence from the Dry Valleys and wider Transantarctic Mountains, showing landscape and climatic stability since the middle Miocene. This terrestrial evidence has been used to infer that the East Antarctic Ice Sheet has been large and in a similar state to today for at least 10 million years. Here we present a series of sensitivity experiments using the HadCM3 General Circulation Model, simulating the impact of ice sheet retreats on Pliocene climate. Major collapses in the marine basins cause changes in the atmospheric circulation around East Antarctica and propagate warmer and wetter air masses into the interior of the ice sheet. However, remaining areas of upland ice sheet act to protect areas of the interior from increases in temperature and precipitation. Only when ice retreats from the upland areas between the subglacial basins and the Transantarctic Mountains of Northern Victoria Land are the Dry Valleys exposed to mean summer temperatures significantly above freezing and the full increases in modelled precipitation. This suggests that collapses of the marine portions of the Wilkes Subglacial Basin and Aurora Subglacial Basin would not have significantly altered the palaeoenvironmental record of the Dry Valleys. These results provide a reconciliation of the records of East Antarctic ice sheet retreat and climate stability and further corroborate the findings from marine cores. We also present the results of an iceberg modelling study that shows that observed losses of Wilkes Land IRD in the Prydz Bay region cannot be explained by climate induced changes in melting or iceberg trajectory, but probably requires the loss of the marine margin of the Wilkes Land sector of the East Antarctic Ice Sheet.

  16. Hydroacoustic habitat mapping in Potter Cove (King George Island, Antarctica)

    Science.gov (United States)

    Hass, H. Christian; Wölfl, Anne-Cathrin; Kuhn, Gerhard; Jerosch, Kerstin; Scharf, Frauke; Abele, Doris

    2016-04-01

    Climate change increasingly affects the coastal areas off Antarctica. Strongest environmental response occurs in the transition zones that mediate between the polar and subpolar latitudes. Potter Cove, a minor fjord at the northern tip of the Antarctic Peninsula is significantly affected by rising temperatures and retreating ice sheets. Large amounts of turbid meltwaters affect both, the seafloor and the water column and cause stress for many biota. There is an increasing demand to monitor the ongoing change and to work out means for comparison with similar coastal ecosystems under pressure. Marine habitat maps provide information on the seafloor characteristics that allow to describe and evaluate the status of the recent coastal ecosystem and to predict its future development. We used a RoxAnn acoustic ground discrimination system, a sidescan sonar, grab samples (grain size and TOC) and underwater video footage to gain habitat information. Supervised and unsupervised classification routines (including fuzzy k-means clustering and LDA) were employed to calculate models ranging from two classes (soft bottom habitat, stone habitat) to 7 classes (including classes of rocks with and without macroalgae as well as classes of gravels, sands and silts). Including organic carbon in the database allowed to identify a carbon-depleted class proximal to the glacier front. Potter Cove reveals features that are related to the climate-controlled environmental change: very rough seafloor topography in a small basin close to the fjord head which was cleared by the retreating tidewater glacier through the past two decades. The increasing distance to the glacier down-fjord causes existing habitats to smooth and mature and new habitats to form. This process will change the terrestrial and marine face of Potter Cove until the ongoing climatic change stops or even reverses. It becomes apparent that the final interpretation of the results benefits significantly from the different

  17. Gastrointestinal parasites in Chinstrap Penguins from Deception Island, South Shetlands, Antarctica.

    Science.gov (United States)

    Vidal, V; Ortiz, J; Diaz, J I; de Ybañez, M R Ruiz; Amat, M T; Palacios, M J; Benzal, J; Valera, F; de la Cruz, C; Motas, M; Barbosa, A

    2012-08-01

    Knowledge about parasites of Antarctic birds is fragmented and scarce. The aim of this work is to contribute to the knowledge of gastrointestinal parasites of the Chinstrap Penguin (Pygoscelis antarctica) from Deception Island (South Shetlands, Antarctica). Gastrointestinal tracts of 64 fresh dead individuals (61 chicks and three adults) were collected from December 2006 to February 2009 and examined for macroparasites. Three adult parasite species were found: two Cestoda species (Parorchites zederi and Tetrabothrius pauliani) and one Nematoda species (Stegophorus macronectes). Also, immature acanthocephalans (Corynosoma sp.) were found in one penguin. The low parasite richness observed could be related to the stenophagic and pelagic diet of the host species. False negatives were found in coprological studies.

  18. Observations on ca. 175-year old human remains from Antarctica (Cape Shirreff, Livingston Island, South Shetlands).

    Science.gov (United States)

    Torres, D

    1999-04-01

    Information is presented on human remains from Antarctica and the circumstances under which they were found at Cape Shirreff (62 degrees 27' S., 60 degrees 47' W.), Livingston Island, South Shetlands. Support is given to the hypothesis that all the recovered bones belonged to the same person. A thorough anthropometric analysis revealed that the skull belonged to a mestizo female, 21 years of age, who may have hailed from the Chilean southern channels and whose arrival to Antarctica was possible aboard a sealer boat. Death appears to have occurred in the Antarctic during the sealing period (1819-1825). Signs of nutritional stress, anaemia, and an external otitis were identified. It is intended to use DNA analyses to prove that the femurs recovered in 1988 and 1993 belonged to the same person whose skull was found at Cape Shirreff in 1985.

  19. 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.

  20. India-East Antarctica conjugate margins: rift-shear tectonic setting inferred from gravity and bathymetry data

    Science.gov (United States)

    Chand, Shyam; Radhakrishna, M.; Subrahmanyam, C.

    2001-02-01

    The Eastern Continental Margin of India (ECMI) has evolved as a consequence of breakup of India from East Antarctica during the Early Cretaceous (ca. 130 Ma). The conjugate margin of ECMI in East Antarctica is represented by the margin extending from Gunneris Ridge in the west to about 95°E in the east. To understand the isostatic compensation mechanism operating beneath these conjugate margins, we have examined the cross spectral correlation between gravity and bathymetry along 21 profiles across the ECMI and 16 profiles across the conjugate East Antarctica Margin using both ship and satellite-derived gravity data. The ECMI is considered as a composite of two segments, one north of 16°N extending beyond 20°N, which is based on its rifted margin character, and the other, south of 16°N extending up to Sri Lanka, which has a transform-rift character. Similarly, the conjugate margin of East Antarctica is also considered to be a composite of two segments, west and east of the central bulge at 50-55°E. Admittance analysis and comparison with various isostatic models suggest a flexural plate model with an elastic thickness of 10-25 km for the northern segment of ECMI and its conjugate segment which is the east Enderby land Margin, comparable to results obtained from the eastern North American Margin. For the southern segment of ECMI, low elastic plate thickness of less than 5 km or a local compensation is obtained with matching results for the west Enderby land Margin. These, in turn, appear comparable to the low Te values inferred for the Ghana transform margin of North Africa and Grand Banks Margin of eastern Canada, thereby indicating that the southern segment of ECMI and its conjugate in East Antarctica have developed as a consequence of shearing rather than rifting in the early stages of continental separation.

  1. Broadband seismic deployments in East Antarctica: IPY contribution to monitoring the Earth’s interiors

    Directory of Open Access Journals (Sweden)

    Masaki Kanao

    2014-06-01

    Full Text Available “Deployment of broadband seismic stations on the Antarctica continent” is an ambitious project to improve the spatial resolution of seismic data across the Antarctic Plate and surrounding regions. Several international collaborative programs for the purpose of geomonitoring were conducted in Antarctica during the International Polar Year (IPY 2007-2008. The Antarctica’s GAmburtsev Province (AGAP; IPY #147, the GAmburtsev Mountain SEISmic experiment (GAMSEIS, a part of AGAP, and the Polar Earth Observing Network (POLENET; IPY #185 were major contributions in establishing a geophysical network in Antarctica. The AGAP/GAMSEIS project was an internationally coordinated deployment of more than 30 broadband seismographs over the crest of the Gambursev Mountains (Dome-A, Dome-C and Dome-F area. The investigations provide detailed information on crustal thickness and mantle structure; provide key constraints on the origin of the Gamburtsev Mountains; and more broadly on the structure and evolution of the East Antarctic craton and subglacial environment. From GAMSEIS and POLENET data obtained, local and regional seismic signals associated with ice movements, oceanic loading, and local meteorological variations were recorded together with a significant number of teleseismic events. In this chapter, in addition to the Earth’s interiors, we will demonstrate some of the remarkable seismic signals detected during IPY that illustrate the capabilities of broadband seismometers to study the sub-glacial environment, particularly at the margins of Antarctica. Additionally, the AGAP and POLENET stations have an important role in the Federation of Digital Seismographic Network (FDSN in southern high latitude.

  2. Volcanic geology of Admiralty Bay, King George Island, Antarctica

    Institute of Scientific and Technical Information of China (English)

    邢光福; 王德滋; 金庆民; 沈渭洲; 陶奎元

    2002-01-01

    At Admiralty Bay of central King George Island, Keller Peninsula, Ullman Spur and Point Hennequin are main Tertiary volcanic terranes. Field investigation and isotopic datings indicate that, there occurred three periods of eruptions ( three volcanic cycles) and accompanying N-toward migration of the volcanic center on Keller Peninsula. After the second period of eruptions, the crater collapsed and a caldera was formed, then later eruptions were limited at the northern end of the peninsula and finally migrated to Ullman Spur. Thus Keller Peninsula is a revived caldera, and its volcanism migrated toward E with time. Point Hennequin volcanism happened more or less simultaneously with the above two areas, but has no clear relation in chemical evolution with them, frequently it belongs to another independent volcanic center.

  3. Climatic signals from 76 shallow firn cores in Dronning Maud Land, East Antarctica

    Directory of Open Access Journals (Sweden)

    S. Altnau

    2014-12-01

    Full Text Available The spatial and temporal distribution of surface mass balance (SMB and δ18O were investigated in the first comprehensive study of a set of 76 firn cores retrieved by various expeditions during the past three decades in Dronning Maud Land, East Antarctica. The large number of cores was used to calculate stacked records of SMB and δ18O, which considerably increased the signal-to-noise ratio compared to earlier studies and facilitated the detection of climatic signals. Considerable differences between cores from the interior plateau and the coastal cores were found. The δ18O of both the plateau and the ice shelf cores exhibit a slight positive trend over the second half of the 20th century. In the corresponding period, the SMB has a negative trend in the ice shelf cores, but increases on the plateau. Comparison with meteorological data from Neumayer Station revealed that for the ice shelf regions atmospheric dynamic effects are more important than thermodynamics, while on the plateau, the temporal variations of SMB and δ18O occur mostly in parallel, thus can be explained by thermodynamic effects. The Southern Annular Mode (SAM exhibits a positive trend since the mid-1960s, which is assumed to lead to a cooling of East Antarctica. This is not confirmed by the firn core data in our data set. Changes in the atmospheric circulation that result in a changed seasonal distribution of precipitation/accumulation could partly explain the observed features in the ice shelf cores.

  4. Spatial distribution and source apportionment of PAHs in marine surface sediments of Prydz Bay, East Antarctica.

    Science.gov (United States)

    Xue, Rui; Chen, Ling; Lu, Zhibo; Wang, Juan; Yang, Haizhen; Zhang, Jie; Cai, Minghong

    2016-12-01

    This paper reports the concentrations of polycyclic aromatic hydrocarbons (PAHs) in marine sediments sampled from Prydz Bay, East Antarctica. Total PAH concentrations ranged from 12.95 to 30.93 ng/g, with a mean of 17.99 ± 5.57 ng/g. Two- and three-ring PAHs were the most abundant compounds found at the majority of the sampling stations of Prydz Bay. Long-range atmospheric transportation was found to play an important role in determining the spatial distribution of PAHs in the sediments sampled here. However, transport by ocean currents and release from melting glaciers were also found to influence PAH distributions in the sediments of East Antarctica. The vertical migration of PAHs in sediments showed a decreasing trend with depth, with higher concentrations in the relatively shallow-water regions (1000 m) of the Amery Basin and associated Canyons, respectively. A Pearson correlation analysis between PAH concentrations and sediment parameters demonstrated that PAHs has poor correlations with grain size, but has positive correlation with total organic carbon, indicated complex processing during transfer to remote environments. The results of qualitative and quantitative analyses indicate that the PAHs sampled here were derived mainly from a mixture of biomass combustion, traffic emissions, and petrogenic sources.

  5. Analysis of mercury and other heavy metals accumulated in lichen Usnea antarctica from James Ross Island, Antarctica.

    Science.gov (United States)

    Zvěřina, Ondřej; Láska, Kamil; Cervenka, Rostislav; Kuta, Jan; Coufalík, Pavel; Komárek, Josef

    2014-12-01

    The study was designed to investigate the content and distribution of selected heavy metals (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Fe, Pb and Zn) in samples of fruticose macrolichen Usnea antarctica from James Ross Island. A special emphasis was devoted to mercury and its species (elemental mercury and methylmercury). It was found that mercury contents were relatively high (up to 2.73 mg kg(-1) dry weight) compared to other parts of the Antarctic Peninsula region, while the concentrations of most other elements were within reported ranges. Mercury contents in lichens originating from the interior were higher than those from the coast, which is probably the result of local microclimate conditions. Similar trends were observed for Hg(0) and MeHg(+), whose contents were up to 0.14 and 0.098 mg kg(-1) dry weight, respectively. While mercury did not show a significant correlation with any other element, the mutual correlation of some litophile elements probably refers to the influence on thalli of resuspended weathered material. The influence of habitat and environmental conditions could play an essential role in the bioaccumulation of contaminants rather than just the simple presence of sources. Thus, the study of the thalli of this species can bring a new perspective on the interpretation of contaminant accumulation in lichens of the polar region.

  6. Preliminary evidence for 17 coastal terraces on Fildes Peninsula, King George Island, Antarctica

    Institute of Scientific and Technical Information of China (English)

    CHU Zhuding; YIN Xuebin; SUN Liguang; WANG Yuhong

    2015-01-01

    This study confirms the presence of 17 coastal terraces on Fildes Peninsula, Antarctica based on field observations and grain size analysis. The terraces formed by isostatic uplift during climate warming and glacier melting, and each level corresponds to a relatively stable period of climate. The grain size characteristics indicate an overlapping sedimentary origin for the sediments on the coastal terraces. The consistency of regional sea level rise, climate change, and glacial area suggest the presence of similar coastal terraces on King George Island since 18.0 ka.

  7. DISCOVERY OF LATE CRETACEOUS PALYNOFLORA FROM FILDES PENINSULA, KING GEORGE ISLAND, ANTARCTICA AND ITS SIGNIFICANCE

    Institute of Scientific and Technical Information of China (English)

    1990-01-01

    This paper makes an analysis and study on altogether 8 palyniferous samples from the volcano-sedimentary rock series in the Half Three Point area of the Fildes Peninsula, King George Island, Antarctica, the rock series being grey tuffaceous siltstone in lithological characters, about 5m in thickness. Only after making a number of analyses, could we find the relatively abundant sporopollen fossils from 4 samples (Nos. GWP 4—7). But the fossils are poorly preserved, and most of them can hardly be identifi...

  8. Modern sedimentation patterns in Potter Cove, King George Island, Antarctica

    Science.gov (United States)

    Hass, H. Christian; Kuhn, Gerhard; Wölfl, Anne-Cathrin; Wittenberg, Nina; Betzler, Christian

    2013-04-01

    IMCOAST among a number of other initiatives investigates the modern and the late Holocene environmental development of south King George Island with a strong emphasis on Maxwell Bay and its tributary fjord Potter Cove (maximum water depth: about 200 m). In this part of the project we aim at reconstructing the modern sediment distribution in the inner part of Potter Cove using an acoustic ground discrimination system (RoxAnn) and more than136 ground-truth samples. Over the past 20 years the air temperatures in the immediate working area increased by more than 0.6 K (Schloss et al. 2012) which is less than in other parts of the West Antarctic Peninsula (WAP) but it is still in the range of the recovery of temperatures from the Little Ice Age maximum to the beginning of the 20th century. Potter Cove is a small fjord characterized by a series of moraine ridges produced by a tidewater glacier (Fourcade Glacier). Presumably, the farthest moraine is not much older than about 500 years (LIA maximum), hence the sediment cover is rather thin as evidenced by high resolution seismic data. Since a few years at least the better part of the tidewater glacier retreated onto the island's mainland. It is suggested that such a fundamental change in the fjord's physiography has also changed sedimentation patterns in the area. Potter Cove is characterized by silty-clayey sediments in the deeper inner parts of the cove. Sediments are coarser (fine to coarse sands and boulders) in the shallower areas; they also coarsen from the innermost basin to the mouth of the fjord. Textural structures follow the seabed morphology, i.e. small v-shaped passages through the moraine ridges. The glacier still produces large amounts of turbid melt waters that enter the cove at various places. We presume that very fine-grained sediments fall out from the meltwater plumes and are distributed by mid-depth or even bottom currents, thus suggesting an anti-estuarine circulation pattern. Older sediments that are

  9. Geochemical markers of soil anthropogenic contaminants in polar scientific stations nearby (Antarctica, King George Island).

    Science.gov (United States)

    Prus, Wojciech; Fabiańska, Monika J; Łabno, Radosław

    2015-06-15

    The organic contamination of Antarctic soils and terrestrial sediments from nearby of five polar scientific stations on King George Island (Antarctica) was investigated. Gas chromatography-mass spectrometry (GC-MS) was applied to find composition of dichloromethane extracts of soil and terrestrial sediments. The presence of geochemical markers, such as n-alkanes, steranes, pentacyclic triterpenoids, and alkyl PAHs, their distribution types, and values of their ratios indicates the predominating source of organic fossil fuels and products of their refining rather than from the natural Antarctic environment. Fossil fuel-originated compounds well survived in conditions of Antarctic climate over long times thus enabling to characterize geochemical features of source fossil fuel identified as petroleum expelled from kerogen II of algal/bacterial origins deposited in sub-oxic conditions and being in the middle of catagenesis. Both microbial activity and water leaching play an important role in degradation of terrestrial oil spills in the Antarctica climate, and petroleum alteration occurs lowly over long periods of time. Synthetic anthropogenic compounds found in terrestrial Antarctica sediments included diisopropylnaphthalenes, products of their sulfonates degradation in paper combustion, and organophosporus compounds used as retardants and plasticizers.

  10. Post-LGM deglaciation in Pine Island Bay, West Antarctica

    Science.gov (United States)

    Kirshner, Alexandra E.; Anderson, John B.; Jakobsson, Martin; O'Regan, Matthew; Majewski, Wojciech; Nitsche, Frank O.

    2012-03-01

    To date, understanding of ice sheet retreat within Pine Island Bay (PIB) following the Last Glacial Maximum (LGM) was based on seven radiocarbon dates and only fragmentary seafloor geomorphic evidence. During the austral summer 2009-2010, restricted sea ice cover allowed for the collection of 27 sediment cores from the outer PIB trough region. Combining these cores with data from prior cruises, over 133 cores have been used to conduct a detailed sedimentological facies analysis. These results, augmented by 23 new radiocarbon dates, are used to reconstruct the post-LGM deglacial history of PIB. Our results record a clear retreat stratigraphy in PIB composed of, from top to base; terrigenous sandy silt (distal glacimarine), pebbly sandy mud (ice-proximal glacimarine), and till. Initial retreat from the outer-continental shelf began shortly after the LGM and before 16.4 k cal yr BP, as a likely response to rising sea level. Bedforms in outer PIB document episodic retreat in the form of back-stepping grounding zone wedges and are associated with proximal glacimarine sediments. A sub-ice shelf facies is observed in central PIB and spans ˜12.3-10.6 k cal yr BP. It is possible that widespread impingement of warm water onto the continental shelf caused an abrupt and widespread change from sub-ice shelf sedimentation to distal glacimarine sedimentation dominated by widespread dispersal of terrigenous silt between 7.8 and 7.0 k cal yr BP. The final phase of retreat ended before ˜1.3 k cal yr BP, when the grounding line migrated to a location near the current ice margin.

  11. 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...

  12. 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...

  13. Soil micromorphology, geochemistry and microbiology at two sites on James Ross Island, Maritime Antarctica

    Science.gov (United States)

    Meier, Lars A.; Krauze, Patryk; Prater, Isabel; Scholten, Thomas; Wagner, Dirk; Kühn, Peter; Mueller, Carsten W.

    2017-04-01

    Referring to the fundamental question in ecosystem research, how biotic and abiotic processes interact, only a few studies exist for polar regions that integrate microbiological and soil scientific studies . Soils comprise the complex structure and environment that fosters water storage and nutrient cycling determined by its unique chemical, physical and biological properties with respect to the specific climate and parent material. In the extreme environment of Antarctica, soil biological processes are primarily controlled by microbial communities (Bacteria, Archaea and Fungi), and thus microbiota may also determine soils chemical and physical properties in a landscape lacking higher plants at an average air temperature below 0°C. James Ross Island, Maritime Antarctica, offers a pristine laboratory and an exceptional opportunity to study pedogenesis without the influence of vascular plants and burrowing animals. We analysed micromorphological features, chemical and microbiological measures at two sites on James Ross Island (Brandy Bay and St. Martha Cove) with similar substrates (mostly fine-grained calcareous sandstones and siltstones of the Alpha Member of the Santa Martha Formation with varying amounts of conglomerates and mudstones) at similar topographic positions (small plateaus at similar elevation (80m a.s.l.)). The sites represent luv- and leeward conditions with respect to the main southwesterly winds. The climate on James Ross Island is to be described as semi-arid polar-continental, which is in clear contrast to the Southern Shetlands (e.g. King George Island) north of the Antarctic Peninsula. We will present first results of soil physical (bulk density, soil moisture and grains size distribution), pedochemical (SOC, total N and S, pH, CECeff, and pedogenic oxides) micromorphological and microbial analyses (Microbial DNA content, microbial abundances).

  14. Complex Wind-Induced Variations of Surface Snow Accumulation Rates over East Antarctica

    Science.gov (United States)

    Das, I.; Scambos, T. A.; Koenig, L.; van den Broeke, M.; Lenaerts, J.

    2015-12-01

    Accurate quantification of surface snow-accumulation over Antarctica is important for mass balance estimates and climate studies based on ice core records. Using airborne radar, lidar and thresholds of surface slope, modeled surface mass balance (SMB) and wind fields, we have predicted continent-wide distribution of wind-scour zones over Antarctica. These zones are located over relatively steep ice surfaces formed by ice flow over bedrock topography. Near-surface winds accelerate over these steeper slopes and erode and sublimate the snow. This results in numerous localized regions (typically ≤ 200 km2) with reduced or negative surface accumulation. Although small zones of re-deposition occur at the base of the steeper slope areas, the redeposited mass is small relative to the ablation loss. Total losses from wind-scour and wind-glaze areas amounts to tens of gigatons annually. Near the coast, winds often blow significant amounts of surface snow from these zones into the ocean. Large uncertainties remain in SMB estimates over East Antarctica as climate models do not adequately represent the small-scale physical processes that lead to mass loss or redistribution over the wind-scour zones. In this study, we also use Operation IceBridge's snow radar data to provide evidence for a gradual ablation of ~16-18 m of firn (~200 years of accumulation) from wind-scour zones over the upper Recovery Ice Stream catchment. The maximum ablation rates observed in this region are ~ -54 kg m-2 a-1 (-54 mm water equivalent a-1). Our airborne radio echo-sounding analysis show snow redeposition downslope of the wind-scour zones is <10% of the cumulative mass loss. Our study shows that the local mass loss is dominated by sublimation to water vapor rather than wind-transport of snow.

  15. Deposition of organochlorine pesticides into the surface snow of East Antarctica.

    Science.gov (United States)

    Kang, Jung-Ho; Son, Min-Hee; Hur, Soon Do; Hong, Sungmin; Motoyama, Hideaki; Fukui, Kotaro; Chang, Yoon-Seok

    2012-09-01

    Organochlorine pesticides (OCPs) were measured in surface snow collected on a ~1400-km inland traverse beginning from the coastal regions of East Antarctica during the Japanese Antarctic Research Expedition (JARE) of 2007/2008. Of the 22 OCPs, α-hexachlorocyclohexane (HCH), γ-HCH, and hexachlorobenzene (HCB) were frequently detected in the snow with concentration ranges of 17.5-83.2, 33-137, and ND-182 pg L(-1), respectively. The most abundant pesticide was γ-HCH, with a mean concentration of 69.9 pg L(-1), followed by α-HCH, with an average concentration of 44.5 pg L(-1). The spatial variability of α-HCH and γ-HCH was narrow, and the concentrations of α-HCH and γ-HCH increased slightly with increasing altitude along the traverse route. Dome Fuji, the highest altitude sampling point, had the highest γ-HCH concentrations in the snow. Backward air trajectory analysis showed that the air masses at the sampling sites came mainly from the Indian and Atlantic Oceans and over the Antarctic continent, indicating that the OCPs were subjected to long-range atmospheric transport and were deposited in the surface snow. Our data suggest that the snow of Antarctica contains low levels of OCPs.

  16. 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.

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

    Science.gov (United States)

    Bigot, Marie; Curran, Mark A. J.; Moy, Andrew D.; Muir, Derek C. G.; Hawker, Darryl W.; Cropp, Roger; Teixeira, Camilla F.; Bengtson Nash, Susan M.

    2016-10-01

    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.

  18. [Diversity and viability of prokaryotes in primitive soils of the larsemann oasis (East Antarctica)].

    Science.gov (United States)

    Kudinova, A G; Lysak, L V; Lapygina, E V; Soina, V S; Mergelov, N S

    2015-01-01

    The diversity and viability of prokaryotic communities in the primitive organomineral soils of East Antarctica have been studied; it has been shown that the total number of bacteria is smaller than and the viability of bacteria is similar to that in soils of the temperate zone. The prokaryotic communities are characterized by the occurrence of a major part of cells in filterable forms, which is higher than the analogous parameter for the temperate soils. The method of fluorescence in situ hybridization (FISH) revealed that the distribution of the main taxons is similar to that in the temperate soils: the portion of the domain Archaea is smaller than that of the domain Bacteria; the total content of Gram-negative bacteria (the phyla Proteobacteria, Acidobacteria, and Planctomycetes) is higher than that of Gram-positive bacteria (Actinobacteria). Within the phylum Proteobacteria, a significant variation of three proteobacterial classes has been noted along the profiles of the soils studied.

  19. 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

  20. New aerogeophysical evidences of riftogenic crust over Princess Elizabeth Land, East Antarctica

    Science.gov (United States)

    Golynsky, Dmitry; Golynsky, Alexander; Kiselev, Alexander

    2014-05-01

    Analysis of radio-echosounding and RADARSAT mosaic data by Golynsky & Golynsky (2007) reveals at least 500 km long structure called the Gaussberg rift over the eastern part of Princess Elizabeth Land, East Antarctica. This previously unknown continuous structure consists of two sub-parallel depressions separated by segmented horst-like escarpments that are largely hidden under the East Antarctic Ice Sheet. One of these segments is Mount Brown escarpment, which reaches a height of 1982 m. It was suggested that the rift was probably initiated at the same time as the Lambert graben, marked by the deposition of coal-bearing Permian sediment and probably inherited the tectonically weak zone of the Proterozoic igneous belt along its boundary with the Vestfold-Rauer Archean cratonic block. The Gaussberg rift may be considered as a hypothetical accommodation zone of the Carboniferous-Permian intracontinental rift along 4000 km of the West Australian and East Indian margins, which filled with thick Permian-Triassic sediment including alluvial coals (Harrowfield et al., 2005). Supposedly, the Gaussberg rift corresponds to the Mahanadi Valley of East India and the Lambert rift system has across-rift alignment with Godavari Valley. New Russian ice penetrating radar data collected in 2012-13 over western part of the suggested rift shows that in places the floor of the central depression is more than 1000 m below sea level. Horst and graben systems are heavily segmented by N-S running transverse lineaments that in addition clearly discernible in the RADARSAT data. New high-quality magnetic data show that severe changes in the magnetic fabric observed in vicinity, along strike and over borders of the structure are though to be due to the tectonic nature. Interruption of the long wavelength high-intensity magnetic anomaly belt associated with southern boundary of the Vestfold-Rauer cratonic block near the western depression can't be explained by a subglacial erosion, in our

  1. Climatic signals from 76 shallow firn cores in Dronning Maud Land, East Antarctica

    Directory of Open Access Journals (Sweden)

    S. Altnau

    2015-05-01

    Full Text Available The spatial and temporal distribution of surface mass balance (SMB and δ18O were investigated in the first comprehensive study of a set of 76 firn cores retrieved by various expeditions during the past 3 decades in Dronning Maud Land, East Antarctica. The large number of cores was used to calculate stacked records of SMB and δ18O, which considerably increased the signal-to-noise ratio compared to earlier studies and facilitated the detection of climatic signals. Considerable differences between cores from the interior plateau and the coastal cores were found. The δ18O of both the plateau and the ice shelf cores exhibit a slight positive trend over the second half of the 20th century. In the corresponding period, the SMB has a negative trend in the ice shelf cores, but increases on the plateau. Comparison with meteorological data from Neumayer Station revealed that for the ice shelf regions, atmospheric dynamic effects are more important than thermodynamics while on the plateau; the temporal variations of SMB and δ18O occur mostly in parallel, and thus can be explained by thermodynamic effects. The Southern Annular Mode (SAM has exhibited a positive trend since the mid-1960s, which is assumed to lead to a cooling of East Antarctica. This is not confirmed by the firn core data in our data set. Changes in the atmospheric circulation that result in a changed seasonal distribution of precipitation/accumulation could partly explain the observed features in the ice shelf cores.

  2. 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

  3. Occurrence of organochlorine pesticides in the environmental matrices from King George Island, west Antarctica.

    Science.gov (United States)

    Zhang, Qinghua; Chen, Zhaojing; Li, Yingming; Wang, Pu; Zhu, Chaofei; Gao, Guanjun; Xiao, Ke; Sun, Huizhong; Zheng, Shucheng; Liang, Yong; Jiang, Guibin

    2015-11-01

    Antarctica is considered as a final sink of many persistent organic pollutants (POPs). This work aims to investigate the levels, distributions and potential sources of organochlorine pesticides (OCPs) with HRGC/HRMS technique. Twenty-three OCPs were measured in various environmental matrices from King George Island, west Antarctica. The total concentrations (Σ23OCPs) were at quite low levels, ranging 93.6-1260 pg g(-1) dry weight (dw) in soil and sediment, 223-1053 pg g(-1) dw in moss and 373-812 pg g(-1) dw in lichen. Hexachlorobenzene (HCB), dichloro-diphenyl-trichloroethane (DDT) and its metabolites (especially p,p'-DDE) and hexachlorocyclohexanes (HCHs) were the main contaminants in all samples. Lower α-HCH/γ-HCH and higher p,p'-DDE/p,p'-DDT ratios compared with the technical products indicated long-range atmospheric transport (LRAT) of recent lindane and aged technical DDT. Significant dependence of many OCPs concentrations on total organic carbon (TOC) was observed. Apart from LRAT, local biotic activities could also contribute and influence the spatial distribution of the contaminants.

  4. A century of climate variability in central Dronning Maud Land, East Antarctica, and its relation to Southern Annular Mode and El Nino-Southern Oscillation

    Digital Repository Service at National Institute of Oceanography (India)

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

    Stable isotope records of oxygen and hydrogen were studied from a 65 m long ice core retrieved from central Dronning Maud Land, East Antarctica, in order to reconstruct the coastal Antarctic climate variability during the last century and its...

  5. Cenozoic terrestrial palynological assemblages in the glacial erratics from the Grove Mountains, east Antarctica

    Institute of Scientific and Technical Information of China (English)

    Aimin Fang; Xiaohan Liu; Weiming Wang; Feixin Huang; Lianjun Yu

    2009-01-01

    Fossiliferous glacial erratics have been found in moraines of the Grove Mountains, east Antarctica since 1998 by Chinese National Antarctic Research Expedition (CHNARE) teams. These erratics were derived from a suite of glaciogene strata hidden beneath the Ant-arctic Ice Sheet in the Lambert glacier drainage system, and thus provide a record of Cenozoic paleoenvironmental conditions and fossil biotas that are so far unknown from outcrops and drill cores in this region. By microfossil analysis, sparse Neogene spores and pollen grains are revealed, including: Toroisporis (Lygodiaceae), Granulatisporites (Pteridaceae?), Osmunda (Osmundaceae), Polypodiaceae, Magnastriatites (Parkeriaceae), Deltoidospora, Araucariaceae, Taxodiaceae, Podocarpus (Podocarpaceae), Dacrydium (Podocarpaceae), Pinus (Pinaceae), Keteleeria (Pinaceae), Picea (Pinaceae), Tsuga (Pinaceae), Chenopodiaceae, Artemisia (Asteraceae), Asteraceae, Grami-neae, Fraxinoipollenites (Oleaceae), Oleoidearumpollenites (Oleaceae), Oleaceae, Operculumpollis, Nothofagidites (Nothofagus), Rhus, Quercus (Fagaceae), Juglans (Juglandaceae), Pterocarya (Juglandaceae), Liquidambar (Hamamelidaceae), Ulmus (Ulmaceae), Ulmoidep-ites (Ulmaceae), Tilia, Proteacidites (Proteaceae) and Tricolpopollenites; but without any marine diatoms. Most of the spores and pollen grains in the erratics are considered to originate from local sources except for some older exotic components that might be recycled from the basement sedimentary rocks by the ice sheet, so they are in situ sporo-palynological assemblages. Furthermore, since the source areas of the glaciogenic sedimentary rocks are assumed to be local or in the up glacier areas, the palynological assemblages in these erratics represent an inland terrestrial flora during a warmer period of the ice-sheet evolutionary history. The ages of these erratics are also dis-cussed based on the occurrence of some diagnostic pollens such as the Artemisia, Chenopodiaceae and Nothofagus, which

  6. Grounding line variability and subglacial lake drainage on Pine Island Glacier, Antarctica

    Science.gov (United States)

    Joughin, Ian; Shean, David E.; Smith, Ben E.; Dutrieux, P.

    2016-09-01

    We produced a 6 year time series of differential tidal displacement for Pine Island Ice Shelf, Antarctica, using speckle-tracking methods applied to fine-resolution TerraSAR-X data. These results reveal that the main grounding line has maintained a relatively steady position over the last 6 years, following the speedup that terminated in ~2009. In the middle of the shelf, there are grounded spots that migrate downstream over the 6 year record. Examination of high-resolution digital elevation models reveals that these grounded spots form where deep keels (thickness anomalies) advect over an approximately flow-parallel bathymetric high, maintaining intermittent contact with the bed. These data sets also reveal several subsidence and uplift events associated with subglacial lake drainages in the fast-flowing region above the grounding line. Although these drainages approximately double the rate of subglacial water flow over periods of a few weeks, they have no discernible effect on horizontal flow speed.

  7. Holocene environmental change according to lake core in Fildes Peninsula of King George Island, Antarctica

    Institute of Scientific and Technical Information of China (English)

    李小梅; 袁宝印; 赵俊琳

    2002-01-01

    Lake core sampled from Xihu in Fildes Peninsula of King Gorge Island, Antarctica could reveal the environmental change of the district. The lake core(GA7) , 9.28 meters long ,was sectioned at an interval of 2 cm. Through measuring the organic carbon, magnetic susceptibility, granularity and organic carbon isotope of GA7, by use of 14C age it was estimated that there were four periods of high temperature in Fildes Peninsula: 4800-4400 aB.P., 3600-3350 aB.P.,2100-1800 aB.P. and 900 aB.P. - present. Meanwhile, results showed that there was a strikingly positive correlation between the content of organic carbon and that of organic carbon isotope(δC13org) which could be the substitute indicators of environmental temperature.

  8. Cretaceous (Late Albian) coniferales of Alexander Island, Antarctica. 2. Leaves, reproductive structures and roots.

    Science.gov (United States)

    Cantrill, D J.; Falcon-Lang, H J.

    2001-06-01

    Coniferous foliage from the Albian of Alexander Island, Antarctica, is assigned to the Araucariaceae, Podocarpaceae, and Taxodiaceae based on attached or associated fertile remains. Araucarian foliage represented by Araucaria alexandrensis sp. nov. and A. chambersii sp. nov. is associated with ovulate cone scales described as Araucarites wollemiaformis sp. nov. and A. citadelbastionensis sp. nov., respectively. The Podocarpaceae is represented by Bellingshausium willeyii sp. nov. and the Taxodiaceae by Athrotaxites ungeri, both with attached cones. Sterile foliage is widespread belonging to the form genera Podozamites, Elatocladus, Brachyphyllum and Pagiophyllum. The conifers in this Albian southern high-latitude flora make up ca. 15% of the species diversity. Evidence from leaf litter distribution on palaeosols and leaf morphology suggest that the majority of conifers were large canopy-forming trees, although a few were probably small understorey shrubs.

  9. Anthropogenic and biogenic hydrocarbons in soils and vegetation from the South Shetland Islands (Antarctica).

    Science.gov (United States)

    Cabrerizo, Ana; Tejedo, Pablo; Dachs, Jordi; Benayas, Javier

    2016-11-01

    Two Antarctic expeditions (in 2009 and 2011) were carried out to assess the local and remote anthropogenic sources of aliphatic and aromatic hydrocarbons, as well as potential biogenic hydrocarbons. Polycyclic aromatic hydrocarbons (PAHs), n-alkanes, biomarkers such as phytane (Ph) and pristane (Pr), and the aliphatic unresolved complex mixture (UCM), were analysed in soil and vegetation samples collected at Deception, Livingston, Barrientos and Penguin Islands (South Shetland Islands, Antarctica). Overall, the patterns of n-alkanes in lichens, mosses and grass were dominated by odd-over-even carbon number alkanes. Mosses and vascular plants showed high abundances of n-C21 to n-C35, while lichens also showed high abundances of n-C17 and n-C19. The lipid content was an important factor controlling the concentrations of n-alkanes in Antarctic vegetation (r(2)=0.28-0.53, p-level<0.05). n-C12 to n-C35 n-alkanes were analysed in soils with a predominance of odd C number n-alkanes (n-C25, n-C27, n-C29, and n-C31), especially in the background soils not influenced by anthropogenic sources. The large values for the carbon predominance index (CPI) and the correlations between odd alkanes and some PAHs suggest the potential biogenic sources of these hydrocarbons in Antarctica. Unresolved complex mixture and CPI values ~1 detected at soils collected at intertidal areas and within the perimeter of Juan Carlos research station, further supported the evidence that even a small settlement (20 persons during the austral summer) can affect the loading of aliphatic and aromatic hydrocarbons in nearby soils. Nevertheless, the assessment of Pr/n-C17 and Ph/n-C18 ratios showed that hydrocarbon degradation is occurring in these soils.

  10. Radionuclides in soils of Byers Peninsula, South Shetland Islands, Western Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Navas, A. [Estacion Experimental de Aula Dei, CSIC, Apartado 202, Zaragoza (Spain)]. E-mail: anavas@eead.csic.es; Soto, J. [Dpt. Ciencias Medicas y Quirurgicas, Universidad de Cantabria, Avda, Cardenal Herrera Oria s/n. 39011 Santander (Spain); Lopez-Martinez, J. [Dpt. Quimica Agricola, Geologia y Geoquimica, Facultad de Ciencias, Universidad Autonoma, de Madrid, 28049 Madrid (Spain)

    2005-05-01

    As a part of a broader study of the surface formations in maritime Antarctica, a preliminary survey on the content of radionuclides has been carried out in soils of Byers Peninsula, located in the western end of Livingston Island, South Shetland Islands. Data on natural and artificial radionuclides are very scarce in Antarctica and the studied soil samples can be representative of the maritime Antarctic environment. Byers Peninsula has an extensive presence of permafrost and an active layer, the studied soils being Criosols and Cryic Leptosols. A series of soil cores between 13 and 40 cm depth have been collected in different lithological and altitudinal contexts. In the southwestern sector of the peninsula, soils have been sampled in seven different sites along a transect on different geomorphological units from an upper marine platform (88 m above sea level) to a Holocene raised beach at an altitude of 24 m a.s.l. The parent materials are mainly Upper Jurassic-Lower Cretaceous marine sandstones and conglomerates and Lower Cretaceous volcanoclastic materials. Individual samples have been obtained from the cores according to textural and colour criteria and analysed for {sup 238}U, {sup 226}Ra, {sup 232}Th, {sup 40}K and {sup 137}Cs by gamma spectrometry. Radionuclides show variations in the depth profile as well as in the different morphoedaphic environments studied. Variability in some radionuclides seems to be related to mineralogy derived from parent materials as well as with cryogenic and soil processes affecting the depth distribution of the granulometric fractions and the organic matter.

  11. Relation between surface topography and sea-salt snow chemistry from Princess Elizabeth Land, East Antarctica

    Directory of Open Access Journals (Sweden)

    K. Mahalinganathan

    2012-04-01

    Full Text Available Previous studies on Antarctic snow have established an unambiguous correlation between variability of sea-salt records and site specific features like elevation and proximity to the sea. On the other hand, variations of Cl/Na+ ratios in snow have been attributed to the reaction mechanisms involving atmospheric acids. In the present study, the annual records of Na+, Cl and SO42− were investigated using snow cores along a 180 km coast to inland transect in Princess Elizabeth Land, East Antarctica. Exceptionally high Na+ concentrations and large variations in Cl/Na+ ratios were observed up to 50 km (∼1100 m elevation of the transect. The steepest slope in the entire transect (49.3 m km−1 was between 20 and 30 km and the sea-salt records in snow from this area revealed extensive modifications, with Cl/Na+ ratios as low as 0.2. Statistical analysis showed a strong association between the slope and variations in Cl/Na+ ratios along the transect (r = −0.676, 99% confidence level. While distance from the coast accounted for some variability, the altitude by itself has no significant control over the sea-salt ion variability. However, the steep slopes influence the deposition of sea-salt aerosols in snow. The wind redistribution of snow due to the steep slopes on the coastal escarpment increases the concentration of Na+, resulting in a low Cl/Na+ ratios. We propose that the slope variations in the coastal regions of Antarctica could significantly influence the sea-salt chemistry of snow.

  12. 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

  13. Cloud and precipitation properties from ground-based remote sensing instruments in East Antarctica

    Directory of Open Access Journals (Sweden)

    I. V. Gorodetskaya

    2014-07-01

    Full Text Available A new comprehensive cloud-precipitation-meteorological observatory has been established at Princess Elisabeth base, located in the escarpment zone of Dronning Maud Land, East Antarctica. The observatory consists of a set of ground-based remote sensing instruments (ceilometer, infrared pyrometer and vertically profiling precipitation radar combined with automatic weather station measurements of near-surface meteorology, radiative fluxes, and snow accumulation. In this paper, the observatory is presented and the potential for studying the evolution of clouds and precipitating systems is illustrated by case studies. It is shown that the synergetic use of the set of instruments allows for distinguishing ice, mixed-phase and precipitating clouds, including some information on their vertical extent. In addition, wind-driven blowing snow events can be distinguished from deeper precipitating systems. Cloud properties largely affect the surface radiative fluxes, with liquid-containing clouds dominating the radiative impact. A statistical analysis of all measurements (in total 14 months mainly occurring in summer/autumn indicates that these liquid-containing clouds occur during as much as 20% of the cloudy periods. The cloud occurrence shows a strong bimodal distribution with clear sky conditions 51% of the time and complete overcast conditions 35% of the time. Snowfall occurred 17% of the cloudy periods with a predominance of light precipitation and only rare events with snowfall > 1 mm h−1 water equivalent (w.e.. Three of such intensive snowfall events occurred during 2011 contributing to anomalously large annual snow accumulation. This is the first deployment of a precipitation radar in Antarctica allowing to assess the contribution of the snowfall to the local surface mass balance. It is shown that on the one hand large accumulation events (>10 mm w.e. day−1 during the measurement period of 26 months were always associated with snowfall, but that

  14. Erosion-driven uplift in the Gamburtsev Subglacial Mountains of East Antarctica

    Science.gov (United States)

    Paxman, G. J. G.; Watts, A. B.; Ferraccioli, F.; Jordan, T. A.; Bell, R. E.; Jamieson, S. S. R.; Finn, C. A.

    2016-10-01

    The relative roles of climate and tectonics in mountain building have been widely debated. Central to this debate is the process of flexural uplift in response to valley incision. Here we quantify this process in the Gamburtsev Subglacial Mountains, a paradoxical tectonic feature in cratonic East Antarctica. Previous studies indicate that rifting and strike-slip tectonics may have provided a key trigger for the initial uplift of the Gamburtsevs, but the contribution of more recent valley incision remains to be quantified. Inverse spectral (free-air admittance and Bouguer coherence) methods indicate that, unusually for continents, the coherence between free-air gravity anomalies and bedrock topography is high (>0.5) and that the elastic thickness of the lithosphere is anomalously low (erosion are quantified: dendritic fluvial incision overprinted by Alpine-style glacial erosion in the Gamburtsevs and outlet glacier-type selective linear erosion in the Lambert Rift, part of the East Antarctic Rift System. 3D flexural models indicate that valley incision has contributed ca. 500 m of peak uplift in the Gamburtsevs and up to 1.2 km in the Lambert Rift, which is consistent with the present-day elevation of Oligocene-Miocene glaciomarine sediments. Overall, we find that 17-25% of Gamburtsev peak uplift can be explained by erosional unloading. These relatively low values are typical of temperate mountain ranges, suggesting that most of the valley incision in the Gamburtsevs occurred prior to widespread glaciation at 34 Ma. The pre-incision topography of the Gamburtsevs lies at 2-2.5 km above sea-level, confirming that they were a key inception point for the development of the East Antarctic Ice Sheet. Tectonic and/or dynamic processes were therefore responsible for ca. 80% of the elevation of the modern Gamburtsev Subglacial Mountains.

  15. Direct evidence of histopathological impacts of wastewater discharge on resident Antarctic fish (Trematomus bernacchii) at Davis Station, East Antarctica.

    Science.gov (United States)

    Corbett, Patricia A; King, Catherine K; Stark, Jonathan S; Mondon, Julie A

    2014-10-15

    During the 2009/2010 summer, a comprehensive environmental impact assessment (EIA) of the wastewater discharge at Davis Station, East Antarctica was completed. As part of this, histological alteration of gill and liver tissue in Antarctic Rock-cod (Trematomus bernacchii) from four sites along a spatial gradient from the wastewater outfall were assessed. All fish within 800 m of the outfall exhibited significant histological changes in both tissues. Common pathologies observed in fish closest to the outfall include proliferation of epithelial cells with associated secondary lamellar fusion in the gills and multifocal granulomata with inflammation and necrosis as well as cysts in the liver. Fish from sites >800 m from the outfall also exhibited alterations but to a lesser degree, with prevalence and severity decreasing with increasing distance from the outfall. This study highlights the value of histopathological investigations as part of EIAs and provides the first evidence of sub-lethal alteration associated with wastewater discharge in East Antarctica.

  16. 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

  17. 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

  18. Deformational evolution of a Cretaceous subduction complex: Elephant Island, South Shetland Islands, Antarctica

    Science.gov (United States)

    Trouw, Rudolph A. J.; Passchier, Cees W.; Valeriano, Claudio M.; Simões, Luiz Sérgio A.; Paciullo, Fabio V. P.; Ribeiro, André

    2000-03-01

    New structural data from Elephant Island and adjacent islands are presented with the objective to improve the understanding of subduction kinematics in the area northeast of the Antarctic Peninsula. On the island, a first deformation phase, D 1, produced a strong SL fabric with steep stretching and mineral lineations, partly defined by relatively high pressure minerals, such as crossite and glaucophane. D 1 is interpreted to record southward subduction along an E-W trench with respect to the present position of the island. A second phase, D 2, led to intense folding with steep E-W-trending axial surfaces. The local presence of sinistral C'-type shear bands related to this phase and the oblique inclination of the L 2 stretching lineations are the main arguments to interpret this phase as representing oblique sinistral transpressive shear along steep, approximately E-W-trending shear zones, with the northern (Pacific) block going down with respect to the southern (Antarctic Peninsula) block. The sinistral strike-slip component may represent a trench-linked strike-slip movement as a consequence of oblique subduction. Lithostatic pressure decreased and temperature increased to peak values during D 2, interpreted to represent the collision of thickened oceanic crust with the active continental margin. The last deformation phase, D 3, is characterised by post-metamorphic kink bands, partially forming conjugate sets consistent with E-W shortening and N-S extension. The rock units that underlie the island probably rotated during D 3, in Cenozoic times, together with the trench, from an NE-SW to the present ENE-WSW position, during the progressive opening of the Scotia Sea. The similarity between the strain orientation of D 3 and that of the sinistral NE-SW Shackleton Fracture Zone is consistent with this interpretation.

  19. Plant Community and Nutrient Status of the Soils of Schirmacher Oasis, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    Shiv Mohan Singh; Jagdev Sharma; Rasik Ravindra; Purnima Singh

    2008-01-01

    Investigations on plant community and micronutrient status of Schirmacher Oasis,East Antarctica have been presented in this paper.The dominant plant communities include moss and lichen.The frequency of species occurrence and changes in species composition at different location varied.Thirty four soil samples were analyzed for chemical properties of the soils of Schirmacher Oasis and Nunatak,East Antarctica.The most common plant species growing throughout the areas of Schirmacher Oasis and Nunataks are: Candelariella flava (lichen) and Bryum pseudotriquetrum (moss).Large variations were observed among different soil samples in all the nutrients and other measured soil chemical parameters.The soils are characterized by acidic pH ranging from 4.42-6.80.The mean organic carbon content was 0.62 and ranged from 0.06-1.29%.The electrical conductivity in 1:2 soil water ratio ranged from 0.06-1.29.The average content of macronutrient cation,which are ammonium acetate extractable was in the order of Ca>K>Na>Mg.The average content of DTPA extractable micronutrient cations was in the order of Fe>Mn>Cu>Zn.Thirty one out of 34 samples contained less than 0.80 ppm DTPA extractable Zn.Correlation studies revealed that content of macronutrient cationssignificantly and positively correlated to that of chlorides.Electrical conductivity exhibited significant and positive relationship with pH,K,Ca,Mg,Na and chloride content.Sodium (r=0.876 **) exhibited highest correlation followed by K (r=0.831 **) with chloride content.The correlation coefficient for chlorides was higher with electrical conductivity (r=0.732 **) than pH (r=0.513 **).Organic carbon content of the soil was positively correlated with Fe (r=0.442 *).The nutrient status did not appear to be a limiting factor in growth of plants.Lichen and moss community structure and composition inthe study area were not related with fertility status of soil.Terrestrial mosses are most abundant and luxuriant along the soil habitats

  20. Biodegradation of phenanthrene by indigenous microorganisms in soils from Livingstone Island, Antarctica.

    Science.gov (United States)

    Okere, Uchechukwu V; Cabrerizo, Ana; Dachs, Jordi; Jones, Kevin C; Semple, Kirk T

    2012-04-01

    Biodegradation of polycyclic aromatic hydrocarbons (PAHs) in soils has been linked to history of exposure to PAHs and prevailing environmental conditions. This work assessed the capacity of indigenous microorganisms in soils collected in Livingstone Island (South Shetlands Islands, Antarctica) with no history of pollution (∑PAHs: 0.14-1.47 ng g(-1) dw) to degrade (14) C-phenanhthrene at 4, 12 and 22 °C. The study provides evidence of the presence of phenanthrene-degrading microorganisms in all studied soils. Generally, the percentage of (14) C-phenanhthrene mineralized increased with increasing temperature. The highest extent of (14) C-phenanhthrene mineralization (47.93%) was observed in the slurried system at 22 °C. This work supports findings of the presence of PAH-degrading microorganisms in uncontaminated soils and suggests the case is the same for uncontaminated Antarctic remote soils. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

  1. Analysis of phosphorus forms in sediment cores from ephemeral ponds on Ardley Island, West Antarctica

    Institute of Scientific and Technical Information of China (English)

    YANG Lianjiao; QIN Xianyan; SUN Liguang; HUANG Tao; WANG Yuhong

    2015-01-01

    The guano of penguins, other seabirds, and pinnipeds is an important source of phosphorus in the ecosystems of Antarctica. To study the vertical distribution of phosphorus in sediments influenced by penguins, we measured phosphorus forms in two sediment cores (G1 and Q2) from ephemeral ponds on Ardley Island. We also investigated the correlations between these phosphorus forms and physicochemical characteristics. Inorganic phosphorus was the main form of phosphorus in both cores. The vertical distribution patterns of phosphorus forms in G1 and Q2 differed, indicating different sedimentary sources. The G1 sediment profile was more influenced by penguin guano than the Q2 profile, and as a result sediments in the G1 core had higher total phosphorus, non-apatite inorganic phosphorus, and apatite phosphorus content. The findings from two ephemeral ponds on Ardley Island indicate that the contribution of penguin guano to organic matter in G1 core has increased in recent times, while Q2 showed a relatively larger contribution from mosses in ancient times, evident from the lithology and the vertical trend in organic matter.

  2. Molecular characterisation of anthropogenic sources of sedimentary organic matter from Potter Cove, King George Island, Antarctica.

    Science.gov (United States)

    Dauner, Ana Lúcia L; Hernández, Edgardo A; MacCormack, Walter P; Martins, César C

    2015-01-01

    Although relatively recent, human activities in Antarctica, such as growing tourism, fishery activities, and scientific operations, have affected some areas of this continent. These activities eventually release pollutants, such as petroleum and its derivatives and sewage, into this environment. Located on King George Island (25 de Mayo Island), Potter Cove (62°14'S, 58°39'W) is home to the Argentine Carlini research station. To evaluate the anthropogenic impacts surrounding Potter Cove, sediment samples were collected and analysed for sewage and fuel introduction via the determination of organic markers. The highest concentrations were found in the central portion of the fjords, where fine sediments are deposited and the accumulation of organic molecules is favoured. Aliphatic hydrocarbons were mainly derived from biogenic sources, evidenced by the predominance of odd short-chain n-alkanes. Anthropogenic impacts were evidenced primarily by the presence of PAHs, which were predominantly related to petrogenic sources, such as vessel and boat traffic. Sewage marker concentrations were much lower than those found in other Antarctic regions. These results indicate that oil hydrocarbons and sewage inputs to Potter Cove may be considered low or only slightly influential.

  3. Inland diatoms from the McMurdo Dry Valleys and James Ross Island, Antarctica

    Science.gov (United States)

    Esposito, R.M.M.; Spaulding, S.A.; McKnight, Diane M.; Van De Vijver, B.; Kopalova, K.; Lubinski, D.; Hall, B.; Whittaker, T.

    2008-01-01

    Diatom taxa present in the inland streams and lakes of the McMurdo Dry Valleys and James Ross Island, Antarctica, are presented in this paper. A total of nine taxa are illustrated, with descriptions of four new species (Luticola austroatlantica sp. nov., Luticola dolia sp. nov., Luticola laeta sp. nov., Muelleria supra sp. nov.). In the perennially ice-covered lakes of the McMurdo Dry Valleys, diatoms are confined to benthic mats within the photic zone. In streams, diatoms are attached to benthic surfaces and within the microbial mat matrix. One species, L. austroatlantica, is found on James Ross Island, of the southern Atlantic archipelago, and the McMurdo Dry Valleys. The McMurdo Dry Valley populations are at the lower range of the size spectrum for the species. Streams flow for 6-10 weeks during the austral summer, when temperatures and solar radiation allow glacial ice to melt. The diatom flora of the region is characterized by species assemblages favored under harsh conditions, with naviculoid taxa as the dominant group and several major diatom groups conspicuously absent. ?? 2008 NRC.

  4. Acquisition of isotopic composition for surface snow in East Antarctica and the links to climatic parameters

    Science.gov (United States)

    Touzeau, Alexandra; Landais, Amaëlle; Stenni, Barbara; Uemura, Ryu; Fukui, Kotaro; Fujita, Shuji; Guilbaud, Sarah; Ekaykin, Alexey; Casado, Mathieu; Barkan, Eugeni; Luz, Boaz; Magand, Olivier; Teste, Grégory; Le Meur, Emmanuel; Baroni, Mélanie; Savarino, Joël; Bourgeois, Ilann; Risi, Camille

    2016-04-01

    The isotopic compositions of oxygen and hydrogen in ice cores are invaluable tools for the reconstruction of past climate variations. Used alone, they give insights into the variations of the local temperature, whereas taken together they can provide information on the climatic conditions at the point of origin of the moisture. However, recent analyses of snow from shallow pits indicate that the climatic signal can become erased in very low accumulation regions, due to local processes of snow reworking. The signal-to-noise ratio decreases and the climatic signal can then only be retrieved using stacks of several snow pits. Obviously, the signal is not completely lost at this stage, otherwise it would be impossible to extract valuable climate information from ice cores as has been done, for instance, for the last glaciation. To better understand how the climatic signal is passed from the precipitation to the snow, we present here results from varied snow samples from East Antarctica. First, we look at the relationship between isotopes and temperature from a geographical point of view, using results from three traverses across Antarctica, to see how the relationship is built up through the distillation process. We also take advantage of these measures to see how second-order parameters (d-excess and 17O-excess) are related to δ18O and how they are controlled. d-excess increases in the interior of the continent (i.e., when δ18O decreases), due to the distillation process, whereas 17O-excess decreases in remote areas, due to kinetic fractionation at low temperature. In both cases, these changes are associated with the loss of original information regarding the source. Then, we look at the same relationships in precipitation samples collected over 1 year at Dome C and Vostok, as well as in surface snow at Dome C. We note that the slope of the δ18O vs. temperature (T) relationship decreases in these samples compared to those from the traverses, and thus caution is

  5. Exploration of Gamburtsev Subglacial Mountains, East Antarctica: Background and Plans for the Near Future

    Science.gov (United States)

    Talalay, Pavel; Sun, Youhong; Zhao, Yue; Li, Yuansheng; Cao, Pinlu; Xu, Huiwen; Zheng, Zhichuan; Wang, Rusheng; Zhang, Nan; Markov, Alexey; Yu, Dahui; Fan, Xiaopeng; Hu, Zhengyi; Yang, Cheng; Gong, Da; Hong, Jialing; Liu, Chunpeng; Han, Junjie; Yu, Chengfeng; Wang, Lili

    2014-05-01

    The Gamburtsev Subglacial Mountains (GSM), located in the central part of East Antarctica, were discovered by the Soviet team of the 3rd Complex Antarctic Expedition in 1958-1959. The GSM has highly dissected Alpine topography reaching maximum elevations of 3000 m and are completely covered by over 600 m of ice and snow. The mechanism driving uplift of the young-shaped GSM in the middle of the old East Antarctic Shield is unknown. With only limited constraints available on the topography, geology, and lithospheric structure, the origin of the GSM has been a matter of considerable speculation. The latest interpretation suggested that the GSM were formed during Permian and Cretaceous (roughly 250-100 Ma ago) due to the combination of rift-flank uplift, root buoyancy and the isostatic response. Later on, the Antarctic Ice Sheet covered the range and protected it from erosion. However, this theory cannot explain lack of erosion process during many millions years in between uplifting and beginning of glaciation. The next step of the GSM exploration focuses on the direct observation of ice sheet bed by drilling. In order to penetrate into subglacial bedrock in the GSM region the development activity already has been started in China. Drilling operations in Antarctica are complicated by extremely low temperature at the surface and within ice sheet, by ice flow, the absence of roads and infrastructures, storms, winds, snowfalls, etc. All that are the reasons that up to the present moment bedrock cores were never obtained at inland of Antarctica. It is proposed to use cable-suspended drilling technology in which an armored cable with a winch is used instead of a pipe-string to provide power to the down-hole motor system and to retrieve the down-hole unit. It is assumed to choose the drill site with the ice thickness at most of 1000 m and to pierce into the mountain slope to a depth of few meters. Proposed borehole construction includes five following steps: (1) dry core

  6. Oxygen isotope mass balance of atmospheric nitrate at Dome C, East Antarctica, during the OPALE campaign

    Science.gov (United States)

    Savarino, Joël; Vicars, William C.; Legrand, Michel; Preunkert, Suzanne; Jourdain, Bruno; Frey, Markus M.; Kukui, Alexandre; Caillon, Nicolas; Gil Roca, Jaime

    2016-03-01

    Variations in the stable oxygen isotope composition of atmospheric nitrate act as novel tools for studying oxidative processes taking place in the troposphere. They provide both qualitative and quantitative constraints on the pathways determining the fate of atmospheric nitrogen oxides (NO + NO2 = NOx). The unique and distinctive 17O excess (Δ17O = δ17O - 0.52 × δ18O) of ozone, which is transferred to NOx via oxidation, is a particularly useful isotopic fingerprint in studies of NOx transformations. Constraining the propagation of 17O excess within the NOx cycle is critical in polar areas, where there exists the possibility of extending atmospheric investigations to the glacial-interglacial timescale using deep ice core records of nitrate. Here we present measurements of the comprehensive isotopic composition of atmospheric nitrate collected at Dome C (East Antarctic Plateau) during the austral summer of 2011/2012. Nitrate isotope analysis has been here combined for the first time with key precursors involved in nitrate production (NOx, O3, OH, HO2, RO2, etc.) and direct observations of the transferrable Δ17O of surface ozone, which was measured at Dome C throughout 2012 using our recently developed analytical approach. Assuming that nitrate is mainly produced in Antarctica in summer through the OH + NO2 pathway and using concurrent measurements of OH and NO2, we calculated a Δ17O signature for nitrate on the order of (21-22 ± 3) ‰. These values are lower than the measured values that ranged between 27 and 31 ‰. This discrepancy between expected and observed Δ17O(NO3-) values suggests the existence of an unknown process that contributes significantly to the atmospheric nitrate budget over this East Antarctic region. However, systematic errors or false isotopic balance transfer functions are not totally excluded.

  7. Oxygen isotope mass balance of atmospheric nitrate at Dome C, East Antarctica, during the OPALE campaign

    Directory of Open Access Journals (Sweden)

    J. Savarino

    2015-09-01

    Full Text Available Variations in the stable oxygen isotope composition of atmospheric nitrate act as novel tools for studying oxidative processes taking place in the troposphere. They provide both qualitative and quantitative constraints on the pathways determining the fate of atmospheric nitrogen oxides (NO + NO2 = NOx. The unique and distinctive 17O-excess (Δ17O = δ17O − 0.52 × δ18O of ozone, which is transferred to NOx via oxidation, is a particularly useful isotopic fingerprint in studies of NOx transformations. Constraining the propagation of 17O-excess within the NOx cycle is critical in polar areas where there exists the possibility of extending atmospheric investigations to the glacial/interglacial time scale using deep ice core records of nitrate. Here we present measurements of the comprehensive isotopic composition of atmospheric nitrate collected at Dome C (East Antarctic plateau during the austral summer of 2011/12. Nitrate isotope analysis has been here combined for the first time with key precursors involved in nitrate production (NOx, O3, OH, HO2, RO2, etc. and direct observations of the transferrable Δ17O of surface ozone, which was measured at Dome C throughout 2012 using our recently developed analytical approach. Assuming that nitrate is mainly produced in Antarctica in summer through the OH + NO2 pathway and using concurrent measurements of OH and NO2, we calculated a Δ17O signature for nitrate in the order of (21–22 ± 3 ‰. These values are lower than the measured values that ranged between 27 and 31 ‰. This discrepancy between expected and observed Δ17O(NO3− values suggests the existence of an unknown process that contributes significantly to the atmospheric nitrate budget over this east Antarctic region.

  8. 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

  9. 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.

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

    Science.gov (United States)

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

    2016-12-01

    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.

  11. New estimations of precipitation and surface sublimation in East Antarctica from snow accumulation measurements

    Energy Technology Data Exchange (ETDEWEB)

    Frezzotti, Massimo; Gragnani, Roberto; Proposito, Marco [l' Energia e l' Ambiente, ' Progetto Clima Globale' , Ente per le Nuove Tecnologie, Rome (Italy); Pourchet, Michel; Gay, Michel; Vincent, Christian; Fily, Michel [CNRS, Laboratoire de Glaciologie et Geophysique de l' Environnement, Saint Martin d' Heres (France); Flora, Onelio [University of Trieste, Dipartimento di Scienze Geologiche, Ambientali e Marine, Trieste (Italy); Gandolfi, Stefano [University of Bologna, Dipartimento di Ingegneria delle Strutture, dei Trasporti, delle Acque, del Rilevamento, del Territorio, Bologna (Italy); Urbini, Stefano [Istituto Nazionale di Geofisica e Vulcanologia, Rome (Italy); Becagli, Silvia; Severi, Mirko; Traversi, Rita; Udisti, Roberto [University of Florence, Dipartimento di Chimica, Florence (Italy)

    2004-12-01

    Surface mass balance (SMB) distribution and its temporal and spatial variability is an essential input parameter in mass balance studies. Different methods were used, compared and integrated (stake farms, ice cores, snow radar, surface morphology, remote sensing) at eight sites along a transect from Terra Nova Bay (TNB) to Dome C (DC) (East Antarctica), to provide detailed information on the SMB. Spatial variability measurements show that the measured maximum snow accumulation (SA) in a 15 km area is well correlated to firn temperature. Wind-driven sublimation processes, controlled by the surface slope in the wind direction, have a huge impact (up to 85% of snow precipitation) on SMB and are significant in terms of past, present and future SMB evaluations. The snow redistribution process is local and has a strong impact on the annual variability of accumulation. The spatial variability of SMB at the kilometre scale is one order of magnitude higher than its temporal variability (20-30%) at the centennial time scale. This high spatial variability is due to wind-driven sublimation. Compared with our SMB calculations, previous compilations generally over-estimate SMB, up to 65% in some areas. (orig.)

  12. Limnology and ecology of lakes along the Sôya Coast, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    Sakae Kudoh; Yukiko Tanabe

    2014-01-01

    The Sôya Coast in East Antarctica has several ice-free areas where many small (<1 km2) and shallow (<50 m depth) glacial lakes display various limnological features. Geological, biological, and ecological studies conducted by the Japanese Antarctic Research Expeditions since 1957 are reviewed herein. Most of the lakes along the coast are oligotrophic;however, water quality is highly variable depending on differences in lake morphology and history. Geophysical and paleolimnological studies suggest that most of the lakes appeared after the Last Glacial Maximum (LGM) and have since maintained a lacustrine condition. The ubiquitous occurrence of benthic microbial assemblages with low phytoplankton biomasses is a common feature of other Antarctic lakes. However, diverse benthic assemblages such as moss pillars and large pinnacle microbial structures are found in the lake basins. Frequent and continuous limnological studies have revealed three typical water circulation patterns, underwater light climate features (too much light, which includes UV radiation during the ice free season), and the structure of benthic assemblages based on their photosynthetic physiology. The phenomenon of mass lfoatation of benthic assemblages was observed in a lake during the ice-covered season;this was explained by seasonal environmental conditions. Thus, a hypothesis was formulated based on ecological matter cycling, eutrophication, and lake succession processes.

  13. Ice flow modelling at EPICA Dome C and Dome Fuji, East Antarctica

    Directory of Open Access Journals (Sweden)

    F. Parrenin

    2007-01-01

    Full Text Available 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 on 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 surface elevation with time.

  14. 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.

  15. 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.

  16. Ecophysiological properties of cultivable heterotrophic bacteria and yeasts dominating in phytocenoses of Galindez Island, maritime Antarctica.

    Science.gov (United States)

    Vasileva-Tonkova, Evgenia; Romanovskaya, Victoria; Gladka, Galina; Gouliamova, Dilnora; Tomova, Iva; Stoilova-Disheva, Margarita; Tashyrev, Oleksandr

    2014-04-01

    Antarctic plants are stable specific microenvironments for microbial colonization that are still less explored. In this study, we investigated cultivable heterotrophic bacteria and yeasts dominating in plant samples collected from different terrestrial biotopes near Ukrainian Antarctic Base on Galindez Island, maritime Antarctica. Phylogenetic analysis revealed affiliation of the bacterial isolates to genera Pseudomonas, Stenotrophomonas, Brevundimonas, Sporosarcina, Dermacoccus, Microbacterium, Rothia and Frondihabitans, and the yeast isolates to genera Rhodosporidium, Cryptococcus, Leucosporidiella, Candida and Exophiala. Some ecophysiological properties of isolated strains were determined that are important in response to different stresses such as psychro- and halotolerance, UV-resistance and production of hydrolytic enzymes. The majority of isolates (88 %) was found to be psychrotolerant; all are halotolerant. Significant differences in survival subsequent to UV-C radiation were observed among the isolates, as measured by culturable counts. For the bacterial isolates, lethal doses in the range 80-600 J m⁻² were determined, and for the yeast isolates--in the range 300-1,000 J m⁻². Dermacoccus profundi U9 and Candida davisiana U6 were found as most UV resistant among the bacterial and yeast isolates, respectively. Producers of caseinase, gelatinase, β-glucosidase, and cellulase were detected. To the best of our knowledge, this is the first report on isolation of UV resistant strain D. profundi, and Frondihabitans strain from Antarctica, and on detection of cellulase activity in Antarctic yeast strain C. davisiana. The results obtained contribute to clarifying adaptation strategies of Antarctic microbiota and its possible role in functional stability of Antarctic biocenoses. Stress tolerant strains were detected that are valuable for ecological and applied studies.

  17. Active layer dynamics in three sites with contrasted topography in the Byers Peninsula (Livingston Island, Antarctica)

    Science.gov (United States)

    Oliva, Marc; Ruiz-Fernández, Jesús; Vieira, Gonçalo

    2015-04-01

    Topography exerts a key role on permafrost distribution in areas where mean annual temperatures are slightly negative. This is the case of low-altitude environments in Maritime Antarctica, namely in the South Shetland Islands, where permafrost is marginal to discontinuous until elevations of 20-40 m asl turning to continuous at higher areas. Consequently, the active layer dynamics is also strongly conditioned by the geomorphological setting. In January 2014 we installed three sites for monitoring the active layer dynamics across the Byers Peninsula (Livingston Island, South Shetland Islands) in different geomorphological environments at elevations between 60 and 100 m. The purpose was to examine the role of the topography and microclimatic conditions on the active layer dynamics. At each site a set of loggers was set up to monitor: air temperatures, snow thickness, ground temperatures until 80 cm together with the coupling atmosphere-ground temperatures. During the first year of monitoring the mean annual air temperatures show similar values in the three sites, in all cases slightly below freezing. The snowy conditions during this year in this archipelago have resulted in a late melting of snow, which has also conditioned the duration of frozen conditions in the uppermost soil layers. Topography has a strong influence on snow cover duration, which in turn affects frozen ground conditions. The Domo site is located in a higher position with respect to the central plateau of Byers; here, the wind is stronger and snow cover thinner, which has conditioned a longer thawing season than in the other two sites (Cerro Negro, Escondido). These two sites are located in topographically protected areas favouring snow accumulation. The longer persistence of snow conditions a longer duration of negative temperatures in the active layer of the permafrost. This research was financially supported by the HOLOANTAR project (Portuguese Science Foundation) and the AXA Research Fund.

  18. An assessment of the record in compositional variations from mantle source to magmatism at East Island, Crozet archipelago

    Science.gov (United States)

    Meyzen, C. M.; Marzoli, A.; Bellieni, G.

    2013-12-01

    The Crozet archipelago, located midway between Madagascar and Antarctica, constitutes the emerged part of the easternmost bank of the Crozet plateau, which lies upon upper Cretaceous oceanic seafloor derived from the Southeast Indian Ridge. It forms an elongated chain of five islands and islets, divided into two groups: an older eastern island group (Terres Australes et Antarctiques Francaises' expedition in 1969 from the northern part of East Island. Our alkali basalts from the Crozet archipelago are distinct from other oceanic within-plate magmatic rocks in showing ubiquitous large depletions in LILE with respect to other incompatible elements, although these rocks constitute one of the most incompatible-element-enriched suites among Earth's oceanic island basalts (OIB). The similarity of their trace element ratios and parallelism of their rare earth element patterns indicate: (1) a mantle source homogeneity over at least 1 Ma; (2) an uniformity of the melting conditions (i.e. degree of melting and residual mineralogy) during most of the sub-aerial eruptive history involving very small melting degrees of a garnet-phlogopite bearing, enriched mantle source, as to be expected to occur beneath an old tectonic plate where the bottom of the lithosphere is likely near the garnet to spinel transition. We will present new geodynamical and geochemical constraints on the mechanisms of formation for such garnet-phlogopite-bearing sources in oceanic island environments.

  19. Oligocene to Miocene terrestrial climate change and the demise of forests on Wilkes Land, East Antarctica

    Science.gov (United States)

    Salzmann, Ulrich; Strother, Stephanie; Sangiorgi, Francesca; Bijl, Peter; Pross, Joerg; Woodward, John; Escutia, Carlota; Brinkhuis, Henk

    2016-04-01

    The question whether Cenozoic climate was warm enough to support a substantial vegetation cover on the Antarctic continent is of great significance to the ongoing controversial debate on the dynamic behaviour of Antarctic land ice during the transition from a greenhouse to an icehouse world. Here we present palynological results from an Oligocene to Miocene sediment record provided by the Integrated Ocean Drilling Program Expedition 318 to the Wilkes Land margin (East Antarctica). The Oligocene assemblages (33.9-23 Ma) are dominated by pollen and spores from temperate forest and sub-Antarctic shrub vegetation inhabiting different altitudinal zones. These include a lowland cold temperate forest with Dacrydium and Lagarostrobos (both common in southern forests of New Zealand and Tasmania today) and a high altitude tundra shrubland comprising Microcachrys, Nothofagus (southern beech) and Podocarpaceae conifers. A decline in pollen percentages of Dacrydium and Lagarostrobos and absence of Proteaceae indicate climate cooling during the late Oligocene (~25-23 Ma). However, the continuous presence of Lagarostrobos suggests that the full transition to a tundra environment had not yet occurred and climate on Wilkes Land during the late Oligocene was still warm enough to support forest vegetation in sheltered areas. Temperature reconstructions derived from the fossil pollen assemblages using the Coexistence Approach suggest mean annual temperatures (MATs) between 6.7-13.7°C during the early Oligocene and a drop of minimum MATs to 5.8°C in the late Oligocene. Pollen of "unambiguous" forest indicators, such as Lagarostrobos, are absent in the Miocene sediment record (16.2 -12.5 Ma) but temperatures were still high enough (minimum MATs > 5°C) to sustain a woody sub-Antarctic vegetation under partially ice-free conditions. Wilkes Land provides a unique record of Antarctic vegetation change from a subtropical, highly diverse Eocene rainforest to an Oligocene cold temperate

  20. Application of a quantitative histological health index for Antarctic rock cod (Trematomus bernacchii) from Davis Station, East Antarctica.

    Science.gov (United States)

    Corbett, Patricia A; King, Catherine K; Mondon, Julie A

    2015-08-01

    A quantitative Histological Health Index (HHI) was applied to Antarctic rock cod (Trematomus bernacchii) using gill, liver, spleen, kidney and gonad to assess the impact of wastewater effluent from Davis Station, East Antarctica. A total of 120 fish were collected from 6 sites in the Prydz Bay region of East Antarctica at varying distances from the wastewater outfall. The HHI revealed a greater severity of alteration in fish at the wastewater outfall, which decreased stepwise with distance. Gill and liver displayed the greatest severity of alteration in fish occurring in close proximity to the wastewater outfall, showing severe and pronounced alteration respectively. Findings of the HHI add to a growing weight of evidence indicating that the current level of wastewater treatment at Davis Station is insufficient to prevent impact to the surrounding environment. The HHI for T. bernacchii developed in this study is recommended as a useful risk assessment tool for assessing in situ, sub-lethal impacts from station-derived contamination in coastal regions throughout Antarctica.

  1. SIPEX 2012: Extreme sea-ice and atmospheric conditions off East Antarctica

    Science.gov (United States)

    Heil, P.; Stammerjohn, S.; Reid, P.; Massom, R. A.; Hutchings, J. K.

    2016-09-01

    In 2012, Antarctic sea-ice coverage was marked by weak annual-mean climate anomalies that consisted of opposing anomalies early and late in the year (some setting new records) which were interspersed by near-average conditions for most of the austral autumn and winter. Here, we investigate the ocean-ice-atmosphere system off East Antarctica, prior to and during the Sea Ice Physics and Ecosystems eXperiment [SIPEX] 2012, by exploring relationships between atmospheric and oceanic forcing together with the sea-ice and snow characteristics. During August and September 2012, just prior to SIPEX 2012, atmospheric circulation over the Southern Ocean was near-average, setting up the ocean-ice-atmosphere system for near-average conditions. However, below-average surface pressure and temperature as well as strengthened circumpolar winds prevailed during June and July 2012. This led to a new record (19.48×106 km2) in maximum Antarctic sea-ice extent recorded in late September. In contrast to the weak circum-Antarctic conditions, the East Antarctic sector (including the SIPEX 2012 region) experienced positive sea-ice extent and concentration anomalies during most of 2012, coincident with negative atmospheric pressure and sea-surface temperature anomalies. Heavily deformed sea ice appeared to be associated with intensified wind stress due to increased cyclonicity as well as an increased influx of sea ice from the east. This increased westward ice flux is likely linked to the break-up of nearly 80% of the Mertz Glacier Tongue in 2010, which strongly modified the coastal configuration and hence the width of the westward coastal current. Combined with favourable atmospheric conditions the associated changed coastal configuration allowed more sea ice to remain within the coastal current at the expense of a reduced northward flow in the region around 141°-145°E. In addition a westward propagating positive anomaly of sea-ice extent from the western Ross Sea during austral winter

  2. Local influences of geothermal anomalies on permafrost distribution in an active volcanic island (Deception Island, Antarctica)

    Science.gov (United States)

    Goyanes, G.; Vieira, G.; Caselli, A.; Cardoso, M.; Marmy, A.; Santos, F.; Bernardo, I.; Hauck, C.

    2014-11-01

    This study aims at understanding the spatial distribution and characteristics of the frozen and unfrozen terrain in an alluvial fan on Deception Island, which is an active strato-volcano located in the Bransfield Strait (South Shetland Islands) with recent eruptions in 1967, 1969 and 1970. The alluvial fan is dominated by debris-flow, run-off and rock fall processes and permafrost occurs in several parts in the vicinity of anomalous geothermal heat flux. The aim is to assess the ways volcanic activity controls permafrost development and associated geomorphic dynamics using shallow subsurface, surface and air temperature measurements as well as thaw depth and electrical resistivity tomography (ERT) surveys. Results show a temperature increase with depth in the lower part of the fan reaching 13 °C at 0.80 m depth, without the presence of permafrost. The shallow borehole located at this site showed a stable thermal stratification all year-round, with only the upper 0.20 m reacting to meteorological forcing. In the upper part of the alluvial fan and debris cones, c. 100 m from the coast, frozen ground is present at c. 0.70 m depth. There, the shallow borehole shows a good coupling with air temperatures and the thermal regime favours the presence of permafrost. ERT shows the lowest resistivity values in the lower part of the alluvial fan and a highly resistivity zone in the upper sector of the fan and in the debris cones. These large variations in resistivity mark the presence of a saline water wedge from the sea into the fan, reaching frozen ground conditions about 100 m inland. It can be shown that the volcano-hydrothermal activity only inhibits frost development very locally, with frozen ground conditions occurring about 100 m away.

  3. Relative sea-level rise around East Antarctica during Oligocene glaciation

    NARCIS (Netherlands)

    Stocchi, P.; Escutia, C.; Houben, A.J.P.; Vermeersen, B.L.A.; Bijl, P.K.; Brinkhuis, H.; Deconto, R.M.; Galeotti, S.; Passchier, S.; Pollard, D.

    2013-01-01

    During the middle and late Eocene (∼ 48-34 Myr ago), the Earth's climate cooled and an ice sheet built up on Antarctica. The stepwise expansion of ice on Antarctica induced crustal deformation and gravitational perturbations around the continent. Close to the ice sheet, sea level rose despite an ove

  4. Relative sea-level rise around East Antarctica during Oligocene glaciation

    NARCIS (Netherlands)

    Stocchi, P.; Escutia, C.; Houben, A.J.P.; Vermeersen, B.L.A.; Bijl, P.K.; Brinkhuis, H.; DeConto , R.M.; Galeotti, S.; Passchier, S.; Pollard, D.; IODP Expedition 318 Scientists; Houben, A.J.P.

    2013-01-01

    During the middle and late Eocene (similar to 48-34 Myr ago), the Earth's climate cooled(1,2) and an ice sheet built up on Antarctica. The stepwise expansion of ice on Antarctica(3,4) induced crustal deformation and gravitational perturbations around the continent. Close to the ice sheet, sea level

  5. Relative sea-level rise around East Antarctica during Oligocene glaciation

    NARCIS (Netherlands)

    Stocchi, P.; Escutia, C.; Houben, A.J.P.; Vermeersen, B.L.A.; Bijl, P.K.; Brinkhuis, H.; Deconto, R.M.; Galeotti, S.; Passchier, S.; Pollard, D.

    2013-01-01

    During the middle and late Eocene (∼ 48-34 Myr ago), the Earth's climate cooled and an ice sheet built up on Antarctica. The stepwise expansion of ice on Antarctica induced crustal deformation and gravitational perturbations around the continent. Close to the ice sheet, sea level rose despite an ove

  6. Relative sea-level rise around East Antarctica during Oligocene glaciation

    NARCIS (Netherlands)

    Stocchi, P.; Escutia, C.; Houben, A.J.P.; Vermeersen, B.L.A.; Bijl, P.K.; Brinkhuis, H.; DeConto , R.M.; Galeotti, S.; Passchier, S.; Pollard, D.; IODP Expedition 318 Scientists; Houben, A.J.P.

    2013-01-01

    During the middle and late Eocene (similar to 48-34 Myr ago), the Earth's climate cooled(1,2) and an ice sheet built up on Antarctica. The stepwise expansion of ice on Antarctica(3,4) induced crustal deformation and gravitational perturbations around the continent. Close to the ice sheet, sea level

  7. Climate signals in Late Holocene sediments from Maxwell Bay and English Strait (South Shetland Islands, Antarctica)

    Science.gov (United States)

    Hass, H. Christian; Schröder, Simon; Kuhn, Gerhard

    2017-04-01

    Climate fluctuations of the past two millennia such as the Little Ice Age and the Medieval Warm Period are reported mainly from the Northern Hemisphere. Evidence from Antarctica is comparably sparse and reveals regional and temporal differences, which are particularly evident at the western and eastern sides of the Antarctic Peninsula. High-resolution coastal-marine sediment cores from the northernmost tip of the West Antarctic Peninsula reveal periods dominated by finer sediments between periods that lack the finer sediment component. In Maxwell Bay this fine sediment (grain size mode around 16 µm) has been traced back to sediment related to the occurrence of glacial meltwater. It was found in sheltered places and meltwater creeks of Potter Cove, a small tributary fjord to Maxwell Bay. In the sediment core this sediment occurs predominantly between 600 and 1250 AD (Medieval Warm Period) whereas it is only sparsely affecting the record between 1450 and 1900 AD (Little Ice Age). The temporal pattern is very similar to global-temperature reconstructions and even resembles temperature reconstructions from the Northern Hemisphere. To avoid local effects that may occur in Maxwell Bay more sediment cores were taken from bays and straits further south of King George Island during Cruise PS97 of RV "Polarstern" in 2016. A core from English Strait reveals completely different sedimentary conditions with no detectable meltwater signal (16 µm). However, the mean grain size record resembles that of the cores from Maxwell Bay. The lack of a clear-cut meltwater sediment class as it occurs further north is likely the result of a much smaller hinterland (Greenwich and Robert islands) when compared to Maxwell Bay between Nelson Island and the much bigger King George Island where glaciers and ice sheets discharge large quantities of very turbid meltwater directly into the bay. It is concluded that during the warmer climate periods a large amount of meltwater was released along the

  8. Ice core evidence for a 20th century increase in surface mass balance in coastal Dronning Maud Land, East Antarctica

    Science.gov (United States)

    Philippe, Morgane; Tison, Jean-Louis; Fjøsne, Karen; Hubbard, Bryn; Kjær, Helle A.; Lenaerts, Jan T. M.; Drews, Reinhard; Sheldon, Simon G.; De Bondt, Kevin; Claeys, Philippe; Pattyn, Frank

    2016-10-01

    Ice cores provide temporal records of surface mass balance (SMB). Coastal areas of Antarctica have relatively high and variable SMB, but are under-represented in records spanning more than 100 years. Here we present SMB reconstruction from a 120 m-long ice core drilled in 2012 on the Derwael Ice Rise, coastal Dronning Maud Land, East Antarctica. Water stable isotope (δ18O and δD) stratigraphy is supplemented by discontinuous major ion profiles and continuous electrical conductivity measurements. The base of the ice core is dated to AD 1759 ± 16, providing a climate proxy for the past ˜ 250 years. The core's annual layer thickness history is combined with its gravimetric density profile to reconstruct the site's SMB history, corrected for the influence of ice deformation. The mean SMB for the core's entire history is 0.47 ± 0.02 m water equivalent (w.e.) a-1. The time series of reconstructed annual SMB shows high variability, but a general increase beginning in the 20th century. This increase is particularly marked during the last 50 years (1962-2011), which yields mean SMB of 0.61 ± 0.01 m w.e. a-1. This trend is compared with other reported SMB data in Antarctica, generally showing a high spatial variability. Output of the fully coupled Community Earth System Model (CESM) suggests that, although atmospheric circulation is the main factor influencing SMB, variability in sea surface temperatures and sea ice cover in the precipitation source region also explain part of the variability in SMB. Local snow redistribution can also influence interannual variability but is unlikely to influence long-term trends significantly. This is the first record from a coastal ice core in East Antarctica to show an increase in SMB beginning in the early 20th century and particularly marked during the last 50 years.

  9. Control of barrier island shape by inlet sediment bypassing: East Frisian Islands, West Germany

    Science.gov (United States)

    FitzGerald, D.M.; Penland, S.; Nummedal, D.

    1984-01-01

    A study of the East Frisian Islands has shown that the plan form of these islands can be explained by processes of inlet sediment bypassing. This island chain is located on a high wave energy, high tide range shoreline where the average deep-water significant wave height exceeds 1.0 m and the spring tidal range varies from 2.7 m at Juist to 2.9 m at Wangerooge. An abundant sediment supply and a strong eastward component of wave power (4.4 ?? 103 W m-1) have caused a persistent eastward growth of the barrier islands. The eastward extension of the barriers has been accommodated more by inlet narrowing, than by inlet migration. It is estimated from morphological evidence that a minimum of 2.7 ?? 105 m3 of sand is delivered to the inlets each year via the easterly longshore transport system. Much of this sand ultimately bypasses the inlets in the form of large, migrating swash bars. The location where the swash bars attach to the beach is controlled by the amount of overlap of the ebb-tidal delta along the downdrift inlet shoreline. The configuration of the ebbtidal delta, in turn, is a function of inlet size and position of the main ebb channel. The swash bar welding process has caused preferential beach nourishment and historical shoreline progradation. Along the East Frisian Islands this process has produced barrier islands with humpbacked, bulbous updrift and bulbous downdrift shapes. The model of barrier island development presented in this paper not only explains well the configuration of the German barriers but also the morphology of barriers along many other mixed energy coasts. ?? 1984.

  10. GEODESY AND DIGITAL CARTOGRAPHIC SURVEY IN FILDES PENINSULA,REY JORGE ISLAND,ANTARCTICA

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The present paper summarizes a joint effort undertaken by the Instituto Geográfico Militar de Chile (IGM) and the Instituto Antártico Chileno (INACH) in order to obtain digital cartography of the Fildes Peninsula,Rey Jorge Island,Antarctica.This peninsula constitutes the prototype project area for the main IGM_INACH project N° 153 “Cartographic Survey and Geographic Information System of the South Shetlands Islands" The Digital Cartography was implemented at the 1∶5 000 scale,using geodetic GPS control points referenced to ITRF 92 and WGS 84 Data.The UTM Projection was used.All products were produced in compliance with the cartographic standards of the IGM. This cartography was designed in order to satisfy the requirements of a Geographic Information System developed by INACH.This geo_referenced database incorporates a variety of thematic information,enabling it to support scientific investigations,environmental and multi_disciplinary studies,and other applications. As a result of this project the Instituto Geográfico Militar de Chile produced a map at 1∶5 000 scale in digital format,and also a 1∶10 000 topographic map,in paper format,with two editions: first edition of two charts and a second edition with one chart covering the whole project area. Chile and other countries have a number of important permanent activities in this area. These maps are designed to support several and diverse geo_spatial studies related to these activities.

  11. Investigations of the tropospheric halogen chemistry around Ross Island, Antarctica, during austral spring 2012

    Science.gov (United States)

    Zielcke, Johannes; Pöhler, Denis; Frieß, Udo; Hay, Tim; Kreher, Karin; Kalnajs, Lars; Platt, Ulrich

    2013-04-01

    A unique feature of the polar troposphere is the strong impact of halogen photochemistry, in which reactive halogen species (RHS) are responsible for ozone depletion as well as the oxidation of elemental mercury and dimethyl sulphide. The source, however, as well as release and recycling mechanisms of these halogen species are far from being completely understood, especially the role of chlorine and iodine compounds. Reactive chlorine, bromine and iodine compounds are thought to be released from sea salt particles or produced by the photolysis of halocarbons and I2 emitted by the ocean. Here we present observations of halogen oxides, ozone and nitrogen dioxide conducted for three months during austral spring 2012 on Ross Island, Antarctica. Measurements were performed with a suite of remote sensing instruments. An active long-path differential optical absorption spectroscopy (LP-DOAS) system was set up, measuring several species (BrO, O3, NO2, OBrO, IO, OIO, I2, ClO, OClO, CHOCHO, HCHO, HONO) continuously for the whole period, with two light paths over first year sea ice. In addition, a passive MAX-DOAS as well as a new Cavity-Enhanced (CE)-DOAS system were used for mobile halogen oxide measurements on a variety of locations around Ross Island (sea ice, shelf ice, snow, coastal, etc.), with top surface layer pH measurements performed at the different measurement sites. First results show highly variable ozone concentrations including partial Ozone Depletion Events (ODEs), as well as concentrations of BrO up to 16ppt and NO2 up to 15ppb. Suprisingly, a high variation of ozone was observed without significant amounts of BrO, indicating already depleted air masses transported to the measurement site and/or NOx chemistry inhibiting halogen radical reactions.

  12. Distribution and interaction patterns of bacterial communities in an ornithogenic soil of Seymour Island, Antarctica.

    Science.gov (United States)

    Rampelotto, Pabulo Henrique; Barboza, Anthony Diego Muller; Pereira, Antônio Batista; Triplett, Eric W; Schaefer, Carlos Ernesto G R; de Oliveira Camargo, Flávio Anastácio; Roesch, Luiz Fernando Wurdig

    2015-04-01

    Next-generation, culture-independent sequencing offers an excellent opportunity to examine network interactions among different microbial species. In this study, soil bacterial communities from a penguin rookery site at Seymour Island were analyzed for abundance, structure, diversity, and interaction networks to identify interaction patterns among the various taxa at three soil depths. The analysis revealed the presence of eight phyla distributed in different proportions among the surface layer (0-8 cm), middle layer (20-25 cm), and bottom (35-40 cm). The bottom layer presented the highest values of bacterial richness, diversity, and evenness when compared to surface and middle layers. The network analysis revealed the existence of a unique pattern of interactions in which the soil microbial network formed a clustered topology, rather than a modular structure as is usually found in biological communities. In addition, specific taxa were identified as important players in microbial community structure. Furthermore, simulation analyses indicated that the loss of potential keystone groups of microorganisms might alter the patterns of interactions within the microbial community. These findings provide new insights for assessing the consequences of environmental disturbances at the whole-community level in Antarctica.

  13. Shallow marine sedimentation within an active margin basin, James Ross Island, Antarctica

    Science.gov (United States)

    Pirrie, Duncan

    1989-06-01

    The Santa Marta Formation exposed on northern James Ross Island, Antarctica, represents shallow marine shelf sedimentation within an active margin basin. The formation is approximately 1000 m thick, is of uppermost Santonian to Campanian age and represents part of a 5000-6000 m thick sedimentary sequence forming the Larsen Basin. The Larsen Basin represents either a back-arc basin, or a half-graben basin, developed on the extending margin of the Weddell Sea. Twelve sedimentary facies have been recognised, which can be subdivided into two groups: those which are controlled by shelf processes and those which are related to active arc volcanism. Background shelf processes include fair-weather suspension sedimentation, storm sands and rare tidal current reworking. Active arc processes include direct settling of airfall detritus and rapid resedimentation of volcaniclastic detritus by sandy debris-flows and both high- and low-concentration turbidity currents. In addition sheet conglomerates represent debris flows that evolved from syn-sedimentary slumps. Two facies associations representing a mid to outer shelf and an inner shelf depositional setting respectively can be distinguished, with an apparent regression in the ?mid to late Campanian.

  14. Radon and thoron daughter activities in the environment of the King George Island (West Antarctica

    Directory of Open Access Journals (Sweden)

    A. T. Solecki

    2005-06-01

    Full Text Available Results of 253 gamma spectrometric analyses of radon daughters in soil and bedrocks of the King George Island (West Antarctica are presented. Measured values range from 0.1 to 58.4 Bq/kg, and from 4.9 to 75.5 Bq/kg for 214Bi and 208Tl respectively, but most measurements fall in the lower part of this range due to predominantly basaltic character of the geological basement. Obtained gamma spectrometric data correspond well to very low soil gas radon content measured by means of Kodak LR115 being below 454 Bqm-3. Low soil gas radon content and characteristic type of architecture is responsible for low indoor radon activity in Arctowski Station being as low as 10- 15 Bqm-3. The highest 105 Bqm-3 indoor Rn activity has been measured in the greenhouse bungalow of the station. This increased value was probably connected with the presence of about 1000 kg of imported soil material in the greenhouse room of the bungalow. Local zones of increased uranium and thorium content, discovered as a result of radiometric mapping, can potentaily influence atmospheric radon used for meteorological interpretation.

  15. Freshwater mineral nitrogen and essential elements in autotrophs in James Ross Island, West Antarctica

    Directory of Open Access Journals (Sweden)

    Coufalík Pavel

    2016-12-01

    Full Text Available The lakes and watercourses are habitats for various communities of cyanobacteria and algae, which are among the few primary producers in Antarctica. The amount of nutrients in the mineral-poor Antarctic environment is a limiting factor for the growth of freshwater autotrophs in most cases. In this study, the main aim was to assess the availability of mineral nitrogen for microorganisms in cyanobacterial mats in James Ross Island. The nitrate and ammonium ions in water environment were determined as well as the contents of major elements (C, N, P, S, Na, K, Ca, Mg, Al, Fe, Mn in cyanobacterial mats. The molar ratios of C:N, C:P and N:P in mats were in focus. The growth of freshwater autotrophs seems not to be limited by the level of nitrogen, according to the content of available mineral nitrogen in water and the biogeochemical stoichiometry of C:N:P. The source of nutrients in the Ulu Peninsula is not obvious. The nitrogen fixation could enhance the nitrogen content in mats, which was observed in some samples containing the Nostoc sp.

  16. Polyphenolic substrates and dyes degradation by yeasts from 25 de Mayo/King George Island (Antarctica).

    Science.gov (United States)

    Rovati, José I; Pajot, Hipólito F; Ruberto, Lucas; Mac Cormack, Walter; Figueroa, Lucía I C

    2013-11-01

    Antarctica offers a range of extreme climatic conditions, such as low temperatures, high solar radiation and low nutrient availability, and constitutes one of the harshest environments on Earth. Despite that, it has been successfully colonized by ’cold-loving’ fungi, which play a key role in decomposition cycles in cold ecosystems. However, knowledge about the ecological role of yeasts in nutrient or organic matter recycling/mineralization remains highly fragmentary. The aim of this work was to study the yeast microbiota in samples collected on 25 de Mayo/King George Island regarding the scope of their ability to degrade polyphenolic substrates such as lignin and azo dyes. Sixty-one yeast isolates were obtained from 37 samples, including soil, rocks, wood and bones. Molecular analyses based on rDNA sequences revealed that 35 yeasts could be identified at the species level and could be classified in the genera Leucosporidiella, Rhodotorula, Cryptococcus, Bullera and Candida. Cryptococcus victoriae was by far the most ubiquitous species. In total, 33% of the yeast isolates examined showed significant activity for dye decolorization, 25% for laccase activity and 38% for ligninolytic activity. Eleven yeasts did not show positive activity in any of the assays performed and no isolates showed positive activity across all tested substrates. A high diversity of yeasts were isolated in this work, possibly including undescribed species and conspicuous Antarctic yeasts, most of them belonging to oligotrophic, slow-growing and metabolically diverse basidiomycetous genera.

  17. An automatic DI-flux at the Livingston Island geomagnetic observatory, Antarctica: requirements and lessons learned

    Science.gov (United States)

    Marsal, Santiago; José Curto, Juan; Torta, Joan Miquel; Gonsette, Alexandre; Favà, Vicent; Rasson, Jean; Ibañez, Miquel; Cid, Òscar

    2017-07-01

    The DI-flux, consisting of a fluxgate magnetometer coupled with a theodolite, is used for the absolute manual measurement of the magnetic field angles in most ground-based observatories worldwide. Commercial solutions for an automated DI-flux have recently been developed by the Royal Meteorological Institute of Belgium (RMI), and are practically restricted to the AutoDIF and its variant, the GyroDIF. In this article, we analyze the pros and cons of both instruments in terms of its suitability for installation at the partially manned geomagnetic observatory of Livingston Island (LIV), Antarctica. We conclude that the GyroDIF, even if it is less accurate and more power demanding, is more suitable than the AutoDIF for harsh conditions due to the simpler infrastructure that is necessary. Power constraints in the Spanish Antarctic Station Juan Carlos I (ASJI) during the unmanned season require an energy-efficient design of the thermally regulated box housing the instrument as well as thorough power management. Our experiences can benefit the geomagnetic community, which often faces similar challenges.

  18. An automatic DI-flux at the Livingston Island geomagnetic observatory, Antarctica: requirements and lessons learned

    Directory of Open Access Journals (Sweden)

    S. Marsal

    2017-07-01

    Full Text Available The DI-flux, consisting of a fluxgate magnetometer coupled with a theodolite, is used for the absolute manual measurement of the magnetic field angles in most ground-based observatories worldwide. Commercial solutions for an automated DI-flux have recently been developed by the Royal Meteorological Institute of Belgium (RMI, and are practically restricted to the AutoDIF and its variant, the GyroDIF. In this article, we analyze the pros and cons of both instruments in terms of its suitability for installation at the partially manned geomagnetic observatory of Livingston Island (LIV, Antarctica. We conclude that the GyroDIF, even if it is less accurate and more power demanding, is more suitable than the AutoDIF for harsh conditions due to the simpler infrastructure that is necessary. Power constraints in the Spanish Antarctic Station Juan Carlos I (ASJI during the unmanned season require an energy-efficient design of the thermally regulated box housing the instrument as well as thorough power management. Our experiences can benefit the geomagnetic community, which often faces similar challenges.

  19. Variability of Basal Melt Beneath the Pine Island Glacier Ice Shelf, West Antarctica

    Science.gov (United States)

    Bindschadler, Robert; Vaughan, David G.; Vornberger, Patricia

    2011-01-01

    Observations from satellite and airborne platforms are combined with model calculations to infer the nature and efficiency of basal melting of the Pine Island Glacier ice shelf, West Antarctica, by ocean waters. Satellite imagery shows surface features that suggest ice-shelf-wide changes to the ocean s influence on the ice shelf as the grounding line retreated. Longitudinal profiles of ice surface and bottom elevations are analyzed to reveal a spatially dependent pattern of basal melt with an annual melt flux of 40.5 Gt/a. One profile captures a persistent set of surface waves that correlates with quasi-annual variations of atmospheric forcing of Amundsen Sea circulation patterns, establishing a direct connection between atmospheric variability and sub-ice-shelf melting. Ice surface troughs are hydrostatically compensated by ice-bottom voids up to 150m deep. Voids form dynamically at the grounding line, triggered by enhanced melting when warmer-than-average water arrives. Subsequent enlargement of the voids is thermally inefficient (4% or less) compared with an overall melting efficiency beneath the ice shelf of 22%. Residual warm water is believed to cause three persistent polynyas at the ice-shelf front seen in Landsat imagery. Landsat thermal imagery confirms the occurrence of warm water at the same locations.

  20. Description of Pseudomonas gregormendelii sp. nov., a Novel Psychrotrophic Bacterium from James Ross Island, Antarctica.

    Science.gov (United States)

    Kosina, Marcel; Švec, Pavel; Černohlávková, Jitka; Barták, Miloš; Snopková, Kateřina; De Vos, Paul; Sedláček, Ivo

    2016-07-01

    During the microbiological research performed within the scope of activities of Czech expeditions based at the Johann Gregor Mendel Station at James Ross Island, Antarctica, two psychrotrophic gram-stain negative non-fluorescent strains CCM 8506T and CCM 8507 from soil were extensively characterized using genotypic and phenotypic methods. Initial characterization using ribotyping with HindIII restriction endonuclease and phenotyping implies that both isolates belong to a single Pseudomonas species. Sequencing of rrs, rpoB, rpoD and glnA genes of strain CCM 8506(T) confirmed affiliation of investigated strains within the genus Pseudomonas. Further investigation using automated ribotyping with EcoRI (RiboPrinter(®) Microbial Characterisation System), whole-cell protein profiling using the Agilent 2100 Bioanalyzer system, extensive biochemical testing and DNA-DNA hybridization experiments confirmed that both investigated strains are members of a single taxon which is clearly separated from all hitherto described Pseudomonas spp. Based on all findings, we describe a novel species Pseudomonas gregormendelii sp. nov. with the type strain CCM 8506(T) (=LMG 28632T).

  1. Study of PCBs and PBDEs in King George Island, Antarctica, using PUF passive air sampling

    Science.gov (United States)

    Li, Yingming; Geng, Dawei; Liu, Fubin; Wang, Thanh; Wang, Pu; Zhang, Qinghua; Jiang, Guibin

    2012-05-01

    Polyurethane foam (PUF)-disk based passive air samplers were deployed in King George Island, Antarctica, during the austral summer of 2009-2010, to investigate levels, distributions and potential sources of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in Antarctic air. The atmospheric levels of ∑ indicator PCBs and ∑14 PBDEs ranged from 1.66 to 6.50 pg m-3 and from 0.67 to 2.98 pg m-3, respectively. PCBs homologue profiles were dominated by di-PCBs, tri-PCBs and tetra-PCBs, whereas BDE-17 and BDE-28 were the predominant congeners of PBDEs, which could be explained by long-range atmospheric transport processes. However, the sampling sites close to the Antarctic research stations showed higher atmospheric concentrations of PCBs and PBDEs than the other sites, reflecting potential local sources from the Antarctic research stations. The non-Aroclor congener PCB-11 was found in all the air samples, with air concentrations of 3.60-31.4 pg m-3 (average 15.2 pg m-3). Comparison between the results derived from PUF-disk passive air sampling and high-volume air sampling validates the feasibility of using the passive air samplers in Antarctic air. To our knowledge, this study is the first employment of PUF-disk based passive air samplers in Antarctic atmosphere.

  2. Radar diagnosis of the subglacial conditions in Dronning Maud Land, East Antarctica

    Directory of Open Access Journals (Sweden)

    S. Fujita

    2012-10-01

    Full Text Available In order to better understand the spatial distribution of subglacial environments, ground-based radar profiling data were analyzed for a total distance of ~ 3300 km across Dronning Maud Land, East Antarctica. The relationship between geometrically corrected bed returned power [Pcbed]dB in decibels and ice thickness H was examined. When H is smaller than a~critical value that varies according to location, [Pcbed]dB tends to decrease relatively smoothly with increasing H, which is explicable primarily by the cumulative effect of dielectric attenuation within the ice. However, at locations where H is larger than the critical H values, anomalous increases and fluctuations in [Pcbed]dB were observed, regardless of the choice of radar frequency or radar-pulse width. In addition, the amplitude of the fluctuations often range 10 ~ 20 dB. We argue that the anomalous increases are caused by higher bed reflectivity associated with the existence of subglacial water. We used these features to delineate frozen and temperate beds. Approximately two-thirds of the investigated area was found to have a temperate bed. The beds of the inland part of the ice sheet tend to be temperate, with the exception of subglacial high mountains. In contrast, the beds of coastal areas tend to be frozen, with the exception of fast-flowing ice on the subglacial lowland or troughs. We argue that this new analytical method can be applied to other regions.

  3. 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.

  4. Radar diagnosis of the subglacial conditions in Dronning Maud Land, East Antarctica

    Directory of Open Access Journals (Sweden)

    S. Fujita

    2012-05-01

    Full Text Available In order to better understand the spatial distribution of subglacial environments, ground-based radar sounding data for a total distance of ~3300 km across Dronning Maud Land, East Antarctica, were analyzed. The relationship between geometrically corrected bed returned power [Pcbed]dB in decibels and ice thickness H was examined. When H is smaller, [Pcbed]dB was found to decrease simply with increasing H, which is explicable by the thickness variation of dielectric attenuation. However, an anomalous increase in [Pcbed]dB at larger H occurred, which was independent of the choice of radar frequencies or radar-pulse widths. We suggest that the existence of water at the ice/substrate interfaces at larger H caused this anomalous increase. We herein propose a new analytical method using these features to delineate frozen and temperate bed areas. Approximately two-thirds of the investigated area was found to have a temperate bed. Basal melting tends to occur when H is larger and the surface elevation is lower. In other words, beds inland of the ice sheet tend to be temperate, with the exception of subglacial high mountains. In contrast, beds of coastal areas tend to be frozen, with the exception of fast-flowing ice at subglacial lowland or troughs. These observations suggest that subglacial water is dominantly produced at the bed of wide inland plateau and that the water is discharged to the sea dominantly through a bed of fast-flowing ice. We also found that a 20-km-wide bed in the subglacial high mountains of an inland plateau near Dome Fuji is frozen, suggesting the existence of very old ice above the bed.

  5. Improvement of Basal Conditions in Wilkes Land, East Antarctica, Using Data Assimilation

    Science.gov (United States)

    Mosbeux, C.; Gillet-chaulet, F.; Gagliardini, O.

    2015-12-01

    The current global warming seems to have direct consequences on ice-sheet mass loss. Reproducing the responsible mechanisms and forecasting the potential ice-sheets contribution to 21st century sea level rise is one of the major challenges in ice-sheet and ice flow modelling. Such short term projections are very sensitive to model initial state which is usually build from field observations. However, some parameters are not observable on the field, such as the basal drag at the interface between the ice-sheet and the bedrock. Data assimilation methods are widely used to constrain this parameter, using ice surface velocities. However, other parameters remain poorly known, especially the bedrock elevation which is only known along fight tracks often distant from several tens of kilometres from each other. These remaining uncertainties lead to ice flux divergence anomalies affecting the free surface evolution and consequently the model projections. In this study, we developed two different assimilation algorithms to better constrain both basal drag and bedrock elevation parameters in the Wilkes Land region, East Antarctica. These two algorithms have been implemented in Elmer/Ice and tested beforehand in a twin experiment showing a clear improvement of both parameters knowledge. The application of these algorithms to Wilkes Land reduces the uncertainty on basal conditions in this region showing more accuracy through below outlet glaciers when compared to usually used DEM of bedrock. Reconstruction of both bedrock elevation and basal drag significantly decreases ice flux divergence anomalies and allows to better constrain future contribution to sea level rise.

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

    Science.gov (United States)

    Hansen, Melissa A.; Passchier, Sandra

    2016-12-01

    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.

  7. Sapphirine in the high grade quartzofeldspathic gneiss of the Larsemann Hills, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    Ren Liudong; Wang Yanbin; Zhao Yue

    2008-01-01

    Study of sapphirine and related mineral association in the high grade region of the Larsemann Hills,East Antarctica,shows that sapphirine of the area is characterized by its magnesio ,iron and aluminum rich,but silica poor feature,and the obvious intra and intergrain changes in compositions.The change is mainly manifested as the Tschermark substitution (Mg,Fe)+Si=2Al.In the high grade metamorphism and anatexis process the multistage crystallization of minerals occurred and resulted in the complexity of the mineral association,such as the differentiation of leuco and melano components.Among them,themafic rich minerals formed earlier,and the differentiation of magnesio and iron components is responsible for the earlier presence of iron rich minerals and later crystallization of magnesio rich minerals,thus the successive associations of multistage occurred.The rock composition is an important but not critical factor to the occurrence of sapphirine.It is the mobilization of components that accounts for the formation of sapphirine.The multistage evolution of mineral association to some degree reflects the changing composition and opening of the setting.It is therefore deduced that the protolith from which sapphirine is derived is not necessarily magnesio rich pelite.The heterogeneity of sapphirine composition is resulted from the various media,not the PT changes. Sapphirine formed at 840~880 ℃,not the so called ultrahigh temperature condition(>1000 ℃).Its formation is related to both the filtration and diffusion processesin high grade metamorphism and anatexis.

  8. 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.

  9. Diatom and Geochemical Constraints on Pliocene Sea Surface Conditions on the Wilkes Land Margin, East Antarctica

    Science.gov (United States)

    Riesselman, C. R.; Taylor-Silva, B.

    2015-12-01

    The mid-Pliocene is the most recent interval in Earth's history to sustain global temperatures within the range of warming predicted for the 21st century, providing an appealing analog with which to examine the changes we might encounter in the coming century. Diatom-based Southern Ocean sea surface and sea ice reconstructions by the USGS Pliocene Research Interpretations and Synoptic Mapping (PRISM) Group suggest an average +2° summer SST anomaly during the 3.3-3.0 Ma interval relative to modern. Here, we present a reconstruction of Pliocene sea surface conditions from a marine sediment core collected at IODP Site U1361, on the continental rise of the Wilkes Land margin. U1361 biogenic silica concentrations document the alternation of diatom-rich and diatom-poor lithologies; we interpret 8 diatom-rich mudstones within this sequence to record interglacial conditions between 3.8 and 2.8 Ma, across the transition from obliquity control to precession control on East Antarctic ice volumes. This progression also preserves 3 packages of interglacial sediments within the 3.3-3.0 PRISM interval, providing an opportunity for direct comparison to proximal PRISM site Eltanin 50-28. Diatom assemblages in both cores are characterized by Fragilariopsis barronii and Rouxia antarctica, extinct species with an inferred ecological preference for waters south of the polar front. However F. weaveri, an extinct diatom with inferred preference for more northerly waters and moderate abundance in E50-28, has not been identified at U1361. This may indicate that the polar frontal zone migrated across E50-28 (62° 54'S) but remained north of U1361 (64° 25'S) during the mid-Pliocene. This interpretation is bolstered by the low abundance of extant polar front species (e.g., Thalassiosira oliverana, T. lentiginosa) at U1361; these diatoms dominate the E50-28 assemblage. In contrast, the U1361 assemblage includes a number of extant sea ice indicators (F. sublinearis, F. curta, Chaetoceros

  10. Recent surface temperature trends in the interior of East Antarctica from borehole firn temperature measurements and geophysical inverse methods

    Science.gov (United States)

    Muto, A.; Scambos, T.A.; Steffen, K.; Slater, A.G.; Clow, G.D.

    2011-01-01

    We use measured firn temperatures down to depths of 80 to 90 m at four locations in the interior of Dronning Maud Land, East Antarctica to derive surface temperature histories spanning the past few decades using two different inverse methods. We find that the mean surface temperatures near the ice divide (the highest-elevation ridge of East Antarctic Ice Sheet) have increased approximately 1 to 1.5 K within the past ???50 years, although the onset and rate of this warming vary by site. Histories at two locations, NUS07-5 (78.65S, 35.64E) and NUS07-7 (82.07S, 54.89E), suggest that the majority of this warming took place in the past one or two decades. Slight cooling to no change was indicated at one location, NUS08-5 (82.63S, 17.87E), off the divide near the Recovery Lakes region. In the most recent decade, inversion results indicate both cooler and warmer periods at different sites due to high interannual variability and relatively high resolution of the inverted surface temperature histories. The overall results of our analysis fit a pattern of recent climate trends emerging from several sources of the Antarctic temperature reconstructions: there is a contrast in surface temperature trends possibly related to altitude in this part of East Antarctica. Copyright 2011 by the American Geophysical Union.

  11. Simultaneous disintegration of outlet glaciers in Porpoise Bay (Wilkes Land), East Antarctica, driven by sea ice break-up

    Science.gov (United States)

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

    2017-02-01

    The floating ice shelves and glacier tongues which fringe the Antarctic continent are important because they help buttress ice flow from the ice sheet interior. Dynamic feedbacks associated with glacier calving have the potential to reduce buttressing and subsequently increase ice flow into the ocean. However, there are few high temporal resolution studies on glacier calving, especially in East Antarctica. Here we use ENVISAT ASAR wide swath mode imagery to investigate monthly glacier terminus change across six marine-terminating outlet glaciers in Porpoise Bay (76° S, 128° E), Wilkes Land (East Antarctica), between November 2002 and March 2012. This reveals a large near-simultaneous calving event in January 2007, resulting in a total of ˜ 2900 km2 of ice being removed from glacier tongues. We also observe the start of a similar large near-simultaneous calving event in March 2016. Our observations suggest that both of these large calving events are driven by the break-up of the multi-year sea ice which usually occupies Porpoise Bay. However, these break-up events appear to have been driven by contrasting mechanisms. We link the 2007 sea ice break-up to atmospheric circulation anomalies in December 2005 weakening the multi-year sea ice through a combination of surface melt and a change in wind direction prior to its eventual break-up in January 2007. In contrast, the 2016 break-up event is linked to the terminus of Holmes (West) Glacier pushing the multi-year sea ice further into the open ocean, making the sea ice more vulnerable to break-up. In the context of predicted future warming and the sensitivity of sea ice to changes in climate, our results highlight the importance of interactions between landfast sea ice and glacier tongue stability in East Antarctica.

  12. Glaciomarine sedimentation and landforms in Admiralty Bay, South Shetland Islands, Antarctica

    Science.gov (United States)

    Magrani, Fabio; Ayres Neto, Arthur; Vieira, Rosemary

    2015-04-01

    This work consists on the integration and interpretation of high-resolution seismic profiles, geological sampling and multibeam bathymetry in order to analyze and understand the evolution of the deglaciation of Admiralty Bay, South Shetland Islands, Antarctica, since the Last Glacial Maximum (LGM). Data were obtained from three expeditions to Antarctica between 2009 and 2013, totaling 500 km of seismic lines and five geological cores. The characterization of the bottom geology was performed by analyzing the echocharacters and the sedimentary thickness of the glaciomarine deposits. Its correlation with the collected samples provided interpretation of the depositional paleoenvironments, allowing the reconstruction and evolution of the glaciers since the LGM and the recognition of glaciomarine processes. Multibeam bathymetry also provided records of submarine landforms related to glacial events and changes in positions of glaciers in the region. In this way, we ought to answer the question: which glaciomarine records are present in Admiralty Bay that can broaden our understanding of the evolution of its deglaciation during the advances and retreats of glaciers that once dominated the fjord, and its sedimentary processes? Four different echocharacters have been identified. Echoes I and II show good resolution and are characterized by continuous and sharp echoes with sub-parallel reflections and the presence of glaciomarine muds. Very prolonged echoes and absence of sub-parallel reflectors characterizes Echoes III and IV. Eco III is associated with the shallower portions of the bay, with little sediment thickness, sandier content and presence of ice rafted debris. Eco IV is associated with morainical banks and grounding zones. Seabed landform features show that the region experienced major glacial advance, with subsequent rapid retreat of the glaciers in the deeper parts of the fjord, followed by slower retreat, with the presence of several recessional moraines in the

  13. The sediments of lake on the Ardley Island, Antarctica:Identification of penguin-dropping soil Sun Liguang

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    During CHINARE-15(Dec. 1998 - Mar. 1999), a lake core 67. 5 cm in length, was sampled in Y2 lake, which is located on the Ardley Island, Antarctica.The concentrations of some chemical elements in Y2 lake sediments were analyzed.According to comparative research on elementary characters of sediments in Antarctic West Lake, fresh penguin dropping as well as guano soil on the Ardley Island and Pacific Island in South China Sea, it presents that the Y2 lake sediments were ameliorated by penguin dropping. The result of element cluster analysis shows that the type elements in the sediment impacted by penguin dropping include Sr, F, S,P,Ca,Se,Cu, Zn and Ba. This can provide a base for further interpreting the climatic and environmental event recorded in the sediment.

  14. Active layer thermal monitoring at Fildes Peninsula, King George Island, Maritime Antarctica

    Directory of Open Access Journals (Sweden)

    R. F. M. Michel

    2014-07-01

    Full Text Available International attention to the climate change phenomena has grown in the last decade; the active layer and permafrost are of great importance in understanding processes and future trends due to their role in energy flux regulation. The objective of the this paper is to present active layer temperature data for one CALM-S site located at Fildes Peninsula, King George Island, Maritime Antarctica over an fifth seven month period (2008–2012. The monitoring site was installed during the summer of 2008 and consists of thermistors (accuracy of ± 0.2 °C, arranged vertically with probes at different depths, recording data at hourly intervals in a~high capacity data logger. A series of statistical analysis were performed to describe the soil temperature time series, including a linear fit in order to identify global trend and a series of autoregressive integrated moving average (ARIMA models were tested in order to define the best fit for the data. The controls of weather on the thermal regime of the active layer have been identified, providing insights about the influence of climate chance over the permafrost. The active layer thermal regime in the studied period was typical of periglacial environment, with extreme variation at the surface during summer resulting in frequent freeze and thaw cycles. The active layer thickness (ALT over the studied period showed variability related to different annual weather conditions, reaching a maximum of 117.5 cm in 2009. The ARIMA model was considered appropriate to treat the dataset, enabling more conclusive analysis and predictions when longer data sets are available. Despite the variability when comparing temperature readings and active layer thickness over the studied period, no warming trend was detected.

  15. Autonomous ocean observations beneath Pine Island Glacier Ice Shelf, West Antarctica

    Science.gov (United States)

    Dutrieux, P.; Jenkins, A.; Jacobs, S.; Heywood, K. J.

    2015-12-01

    Warm circumpolar deep water reaching 3.5ºC above the in situ freezing point pervasively fills a network of glacially carved troughs in the Amundsen sea, West Antarctica, and melts and thins neighbouring ice shelves, including Pine Island glacier Ice Shelf (PIIS). Hydrographic, current, and microstructure observations obtained in austral summer 2009 and 2014 by an autonomous underwater vehicle beneath the PIIS are used here to detail the complex ice-ocean interaction and resulting ocean circulation. The theoretical schematic of deeply incoming warm and saline water melting the grounding line and generating a buoyant plume upwelling along the ice draft is generally consistent with observations. The cavity beneath PIIS is clearly divided in two by a seabed ridge, constraining the oceanic circulation and water masses distribution. On the seaward side of the ridge, a thick warm deep water layer circulates cyclonically and is overlaid by a thin meltwater layer. Only intermediate depth waters are allowed to overflow from the ridge top into the inner cavity, where a much thinner warm water layer is now overlaid by a thicker meltwater layer. At the ice/ocean interface, melt induced freshening is forcing an upwelling which in turn injects cyclonic vorticity and participates in creating a vigorous cyclonic recirculation in the inner cavity. The top of the ridge, where warm waters overflow in the inner cavity, is a dynamical boundary characterized by northward along-ridge currents up to 0.2 m/s and enhanced shear, thermal gradient, and mixing. Observations at two points at the ice interface indicate that the ocean remains stratified within 2 meters of the ice.

  16. Distribution and characterization of soils and landform relationships in Byers Peninsula, Livingston Island, Maritime Antarctica

    Science.gov (United States)

    Moura, Pedro Adnet; Francelino, Marcio R.; Schaefer, Carlos Ernesto G. R.; Simas, Felipe N. B.; de Mendonça, Bruno A. F.

    2012-06-01

    This paper presents the spatial distribution of soils from the northern part of Byers Peninsula, Livingston Island, which is the largest ice-free area of the South Shetlands archipelago, Maritime Antarctica. Physical and chemical characteristics are presented for 23 soil profiles. Soil parent materials vary from marine sedimentary to volcanic and volcanoclastic rocks, intruded by igneous bodies. To assess soil-landscape relationships, twenty-three soil profiles were described and sampled. Soil samples of selected horizons were submitted to chemical, physical and mineralogical analyses. Soil mapping was based on the soil profiles, integrated with the existent topographic map (1:25.000 scale), a digital elevation model, the geological map and a satellite image. Twenty different soil units were identified and mapped. According to the World Reference Base for Soil Resources (WRB) system, soils were classified as Fluvisols, Regosols, Leptosols or Cryosols, which correspond mostly to Fluvents, Orthents/Psamments, Inceptsols and Gelisols, respectively, according to the Soil Taxonomy. Soils from northern Byers Peninsula are generally shallow and coarse textured, with low organic matter content. Three soils from the rocky platforms of the northern coastal region possess ornithogenic character, with lower pH, higher P, Al3 + and organic C values when compared to soils not influenced by sea birds. In non-ornithogenic soils, the presence of easily weatherable minerals in the clay fraction indicates that physical weathering occurs with limited chemical alteration of primary minerals. The influence of penguin and other birds on coastal soils alters clay mineralogy, with formation of poorly crystalline P-rich phases. A better understanding of the depth of the permafrost table and the spatial distribution of permafrost is necessary for a more conclusive classification of Cryosols or Gelisols.

  17. Puriifcation and characterization of a thermostable glutamate dehydrogenase from a thermophilic microorganism from Deception Island, Antarctica

    Institute of Scientific and Technical Information of China (English)

    Patricio A Flores M; Freddy Boehmwald; Jenny M Blamey A

    2016-01-01

    Glutamate dehydrogenase (GDH) catalyzes the oxidative deamination of glutamate toα-ketoglutarate and ammonium ions. Currently the determination of ammonium and glutamate is carried out using a bovine GDH enzyme, which lacks optimal thermostability for long term storage at room temperature. From samples of Deception Island, Antarctica, we obtained the thermophilic bacteria PID 15 belonging to theBacillus genera with high GDH speciifc activity. This new enzyme exhibited NAD+dependent activity and no activity was observed when NADP+was used. This enzyme shows a speciifc activity of 4.7 U∙mg-1 for the oxidative deamination reaction and 15.4 U∙mg-1 for the reduction ofα-ketoglutarate. This enzyme has an optimum temperature of 65°C and pH of 8.5 for the oxidative deamination. For the reduction ofα-ketoglutarate, the optimum temperature is 60°C, with a pH of 8.0. One of the most important characteristics of this enzyme is its ability to retain more than 60% of its activity when it is incubated for 8 h at 65°C. The enzyme is also able to retain full activity when it is incubated for 48 d at 4°C and over 80% of its activity when it is incubated at 25°C. Characterization of its kinetics suggests that it primarily catalyzes the formation of α-ketoglutarate. This enzyme has an important biological role in the catabolism of glutamate and may have some interesting biotechnological applications based on its thermostable properties.

  18. Cretaceous (Late Albian) coniferales of Alexander Island, Antarctica. 1: Wood taxonomy: a quantitative approach.

    Science.gov (United States)

    Falcon-Lang; Cantrill

    2000-08-01

    Silicified conifer woods are very common in the mid-Cretaceous (Late Albian, 100Ma) Triton Point Member of the Neptune Glacier Formation (Fossil Bluff Group), SE Alexander Island, Antarctica. These occur as up to 7m high in situ tree trunks and stumps rooted in carbonaceous palaeosols and as allochthonous logs and wood fragments in fluvial channel and sheet sandstone facies. Sixty-eight wood samples were examined in this study and were classified in terms of five form taxa using a quantitative approach. Araucarioxylon (1.5% of specimens) is characterised by dominantly multiseriate, alternately arranged bordered pitting on radial tracheid walls and by 1-4 araucarioid cross-field pitting. Araucariopitys (11.8% of specimens) is characterised by dominantly uniseriate tracheid pitting with subordinate biseriate, alternate tracheid pitting and by 1-4 araucarioid cross-field pitting. Podocarpoxylon sp. 1 (63.1% of specimens) is characterised by contiguous, uniseriate tracheid pitting and 1-2 podocarpoid cross-field pits. Podocarpoxylon sp. 2 (22.1% of specimens) is similar to P. sp. 1, differing only in that ray height is lower, tracheid pits are dominantly spaced more than one pit diameter apart and abundant axial parenchyma is present. These first four taxa all possess growth rings with subtle boundaries. Taxodioxylon (1.5% of specimens) is characterised by 1-2 seriate, oppositely arranged, bordered tracheid pitting, 1-2 taxodioid cross-field pitting and very marked ring boundaries. These woods were derived from large trees with basal stump diameters of up to 0.5m and probable heights of up to 29m. Data from leaf traces suggest that Araucariopitys and Podocarpoxylon sp. 1 and sp. 2 (97% of specimens) were evergreen with leaf retention times of >5years. These predominantly evergreen conifer forests grew in a mild, high latitude (75 degrees S) environment during the mid-Cretaceous greenhouse climate phase.

  19. Atmospheric nitrogen oxides (NO and NO2) at Dome C, East Antarctica, during the OPALE campaign

    Science.gov (United States)

    Frey, M. M.; Roscoe, H. K.; Kukui, A.; Savarino, J.; France, J. L.; King, M. D.; Legrand, M.; Preunkert, S.

    2015-07-01

    Mixing ratios of the atmospheric nitrogen oxides NO and NO2 were measured as part of the OPALE (Oxidant Production in Antarctic Lands & Export) campaign at Dome C, East Antarctica (75.1° S, 123.3° E, 3233 m), during December 2011 to January 2012. Profiles of NOx mixing ratios of the lower 100 m of the atmosphere confirm that, in contrast to the South Pole, air chemistry at Dome C is strongly influenced by large diurnal cycles in solar irradiance and a sudden collapse of the atmospheric boundary layer in the early evening. Depth profiles of mixing ratios in firn air suggest that the upper snowpack at Dome C holds a significant reservoir of photolytically produced NO2 and is a sink of gas-phase ozone (O3). First-time observations of bromine oxide (BrO) at Dome C show that mixing ratios of BrO near the ground are low, certainly less than 5 pptv, with higher levels in the free troposphere. Assuming steady state, observed mixing ratios of BrO and RO2 radicals are too low to explain the large NO2 : NO ratios found in ambient air, possibly indicating the existence of an unknown process contributing to the atmospheric chemistry of reactive nitrogen above the Antarctic Plateau. During 2011-2012, NOx mixing ratios and flux were larger than in 2009-2010, consistent with also larger surface O3 mixing ratios resulting from increased net O3 production. Large NOx mixing ratios at Dome C arise from a combination of continuous sunlight, shallow mixing height and significant NOx emissions by surface snow (FNOx). During 23 December 2011-12 January 2012, median FNOx was twice that during the same period in 2009-2010 due to significantly larger atmospheric turbulence and a slightly stronger snowpack source. A tripling of FNOx in December 2011 was largely due to changes in snowpack source strength caused primarily by changes in NO3- concentrations in the snow skin layer, and only to a secondary order by decrease of total column O3 and associated increase in NO3- photolysis rates. A

  20. Early Paleozoic (Pan African) thermal event of the Larsemann Hills and its neighbours, Prydz Bay, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    赵越; 宋彪; 张宗清; 富云莲; 陈廷愚; 王彦斌; 任留东; 姚玉鹏; 李继亮; 刘小汉

    1995-01-01

    The early Paleozoic (Pan African) thermal event of the Larsemann Hills and its adjacent areas, East Antarctica is discussed based upon the isotope ages we obtained. An Sm-Nd internal isochron for a representative mafic granulite yields an age of 540 Ma±75 Ma. Another Sm-Nd internal isochron, which is made up of the assemblage of the peak metamorphism and its whole rock as well, gives an age of 497 Ma ± 7 Ma The isotopic chronological data of single zircon stepwise evaporation dating and 40Ar-39Ar analysis provide further evidence for the early Paleozoic event of high-grade metamorphism in the region. The data from the field geological investigation in the Larsemann Hills also show that there is not only strong regional partial melting but also low-pressure granulite-facies metamorphism accompanied by it in the region. The early Paleozoic (Pan African) thermal event of the region may be related to the final formation of the East Antarctica craton, even of Gondwanaland.

  1. Tectonics of Antarctica

    Science.gov (United States)

    Hamilton, W.

    1967-01-01

    Antarctica consists of large and wholly continental east Antarctica and smaller west Antarctica which would form large and small islands, even after isostatic rebound, if its ice cap were melted. Most of east Antarctica is a Precambrian Shield, in much of which charnockites are characteristic. The high Transantarctic Mountains, along the Ross and Weddell Seas, largely follow a geosyncline of Upper Precambrian sedimentary rocks that were deformed, metamorphosed and intruded by granitic rocks during Late Cambrian or Early Ordovician time. The rocks of the orogen were peneplained, then covered by thin and mostly continental Devonian-Jurassic sediments, which were intruded by Jurassic diabase sheets and overlain by plateau-forming tholeiites. Late Cenozoic doming and block-faulting have raised the present high mountains. Northeastern Victoria Land, the end of the Transantarctic Mountains south of New Zealand, preserves part of a Middle Paleozoic orogen. Clastic strata laid unconformably upon the Lower Paleozoic plutonic complex were metamorphosed at low grade, highly deformed and intruded by Late Devonian or Early Carboniferous granodiorites. The overlying Triassic continental sedimentary rocks have been broadly folded and normal-faulted. Interior west Antarctica is composed of miogeosynclinal clastic and subordinate carbonate rocks which span the Paleozoic Era and which were deformed, metamorphosed at generally low grade, and intruded by granitic rocks during Early Mesozoic time and possibly during other times also. Patterns of orogenic belts, if systematic, cannot yet be defined; but fragmentation and rotation of crustal blocks by oroclinal folding and strike-slip faulting can be suggested. The Ellsworth Mountains, for example, consist of Cambrian-Permian metasedimentary rocks that strike northward toward the noncorrelative and latitudinally striking Mesozoic terrane of the Antarctic Peninsula in one direction and southward toward that of the Lower Paleozoic: terrane

  2. 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

  3. A new sediment-dwelling pholadid bivalve from Oligocene glaciomarine sediments of King George Island, West Antarctica

    Directory of Open Access Journals (Sweden)

    Krzysztof Hryniewicz

    2016-12-01

    Full Text Available We present a re-description of the pholadid bivalve from the Oligocene Polonez Cove Formation, King George Island, West Antarctica, previously identified as Penitella sp. The study is based on a collection of 210 specimens, preserved exclusively in life position in flask-shaped Gastrochaenolites type borings which have been subsequently buried by glaciomarine diamictite. The systematic study showed that this pholadid is a new species belonging to the genus Pholadidea rather than to Penitella and we name it Pholadidea gradzinskii sp. nov. The species is one of very few Late Cretaceous–Paleogene pholadids that we could safely identify as Pholadidea. All of them are known exclusively from the southern Pacific and adjacent areas (New Zealand, Antarctica, and Patagonia. We demonstrate that the genus attained its Recent broad distribution before the middle Miocene, when the first species of Pholadidea appeared in the Northern Hemisphere. The mass occurrence of P. gradzinskii in the Oligocene of West Antarctica results from favourable living condition in a shallow marine environment. Low sedimentation rate allowed the settlement of numerous larvae and their subsequent metamorphosis, growth, and maturity terminated by the mass mortality caused by the burial by marine diamictite. The sediment-boring Paleogene species of Pholadidea, among them P. gradzinskii, follow the wood-boring Late Cretaceous species P. (Hatasia wiffenae, which reflects a general pattern of evolution of substrate selection among pholadoid bivalves.

  4. 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

  5. Composition of plagioclases in volcanic rocks of King George Island, Antarctica with reference to the petrogenetic significance

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Plagioclases occur mainly as phenocrysts in volcanic rocks of King George Island, South Shetland Islands, West Antarctica. In basaltic andesites and andesites of Keller Peninsula and Ullman Spur (Admiralty Bay), they are high structure state labradorite-andesines; and in high-A1 basalts and basaltic andesites of Barton and Weaver peninsulas (Maxwell Bay), they are high structure state bytownite-anorthites.∑REE, La/Yb ratios and δEu values of plagioclases from Admiralty Bay are higher than those from Maxwell Bay. All plagioclases have rather identical chondritenormalized transitional element distribution patterns, probably reflecting that crystal structure rather than composition of plagioclase controls their diversity. Compositions of plagioclases depend chiefly on those of their host rocks, compositional differences of plagioclases reveal that basaltic magmas in the Admiralty Bay area are more evolved than in the Maxwell Bay area.

  6. Impact of model resolution on simulated wind, drifting snow and surface mass balance in Terre Adélie, East Antarctica

    NARCIS (Netherlands)

    Lenaerts, J.T.M.; van den Broeke, M.R.; Scarchilli, C.; Agosta, C.

    2012-01-01

    This paper presents the impact of model resolution on the simulated wind speed, drifting snow climate and surface mass balance (SMB) of Terre Ad´elie and its surroundings, East Antarctica. We compare regional climate model simulations at 27 and 5.5 km resolution for the year 2009. The wind speed max

  7. 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

  8. 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

  9. First evidence for a late LGM subglacial lake in Pine Island Bay, Antarctica

    Science.gov (United States)

    Kuhn, Gerhard; Hillenbrand, Claus-Dieter; Kasten, Sabine; Smith, James A.; Nitsche, Frank O.; Frederichs, Thomas; Wiers, Steffen; Ehrmann, Werner; Klages, Johann P.; Mogollón, José M.

    2016-04-01

    Subglacial lakes are widespread beneath the Antarctic Ice Sheet and as a source for subglacial meltwater they are assumed to modulate ice stream velocity. Further, the evacuation of subglacial meltwater at the ice sheet margin influences ocean circulation and geochemical cycles. However, despite their importance,, subglacial lakes are one of the least explored environments on our planet. As a consequence, their importance for ice sheet dynamics and their ability to harbour life remain poorly characterised. We present the first direct evidence for a palaeo-subglacial lake on the Antarctic continental shelf, documenting that subglacial meltwater was stored during the last glacial period and evacuated during the subsequent deglaciation. A distinct sediment facies observed in a core recovered from a small bedrock basin in Pine Island Bay, Amundsen Sea, is indicative of deposition within a low-energy subglacial lake setting. Diffusive modelling demonstrates that low chloride concentrations in the pore water of this characteristic sediment facies can only be explained by original deposition in a freshwater setting. We also show that the location of the subglacial lake within a basin on the inner shelf is consistent with the predicted distribution of subglacial lakes based on bathymetric data. This finding will enable future modelling studies to investigate how the geometry and capacity of subglacial lake systems can influence ice dynamics when the substrate and profile of the ice sheet is known - especially in the highly sensitive area known as the "weak underbelly" of the WAIS. With the exception of a direct lake water access at Subglacial Lake Vostok, and some centimetres of sediment retrieval from Subglacial Lake Whillans, the subglacial hydrological system in Antarctica has hitherto mostly been explored using remote sensing and numerical models that suggest the number of potential lake sites to more than 12.000. Our study not only provides first empirical evidence

  10. Sedimentary regimes at Potter Cove, King George Island, maritime Antarctica - from source to sink

    Science.gov (United States)

    Monien, Donata; Monien, Patrick; Brünjes, Robert M.; Widmer, Tatjana; Schnetger, Bernhard; Brumsack, Hans-Jürgen

    2013-04-01

    Increased particle run-off due to recently retreated ice masses along the Antarctic margins may play an important role in fertilizing the high-nutrient-low-chlorophyll regions of the Southern Ocean. At Potter Cove, King George Island, maritime Antarctica, small melt water streams at the south-eastern shoreline (Potter Peninsula) discharge up to 1,500 mg L-1 (av. 110 mg L-1) of suspended particle matter (SPM) per day into the coastal water body during the summer seasons. Apart from potential light limitation of plankton growth by the suspension load, the particle run-off affects benthic feeders, possibly changes the depositional regime and the preservation of chemical proxies in the outlet zones, and exports trace elements offshore. In Potter Cove's water column, the average particle size is low, and extreme turbidity events are restricted to the upper five to seven meters. High particle loads are often associated with low salinities, most probably induced by increased onshore precipitation. Sediment traps installed in the inner and outer cove at 5 and 20 m water depth suggest mass accumulation rates of 0.83 and 0.58 g cm-2 yr-1, and 0.13 and 0.11 g cm-2 yr-1 (considering 183 days of sedimentation), respectively. 210Pb measurements of short sediment cores reveal recent sediment accumulation rates of approximately 0.1 to 0.6 g cm-2 yr-1. The SPM sampled in the melt water streams and plumes is chemically different to surface sediments deposited in Potter Cove. Chemical characteristics suggest a significant impact of particle sorting: SPM and outer cove sediments are more clayey, whereas inner cove sediments contain more heavy minerals. Generally, sediment deposits in Potter Cove exhibit coarser grain sizes and are mainly derived from Barton Peninsula (northern shoreline), whereas the SPM consists of more fine-grained material originating from Potter Peninsula eluviations. Sequential leaching of the SPM by ascorbic acid showed that approximately 0.5 to 2% of the total

  11. 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

  12. Three-year monitoring of stable isotopes of precipitation at Concordia Station, East Antarctica

    Science.gov (United States)

    Stenni, Barbara; Scarchilli, Claudio; Masson-Delmotte, Valerie; Schlosser, Elisabeth; Ciardini, Virginia; Dreossi, Giuliano; Grigioni, Paolo; Bonazza, Mattia; Cagnati, Anselmo; Karlicek, Daniele; Risi, Camille; Udisti, Roberto; Valt, Mauro

    2016-10-01

    Past temperature reconstructions from Antarctic ice cores require a good quantification and understanding of the relationship between snow isotopic composition and 2 m air or inversion (condensation) temperature. Here, we focus on the French-Italian Concordia Station, central East Antarctic plateau, where the European Project for Ice Coring in Antarctica (EPICA) Dome C ice cores were drilled. We provide a multi-year record of daily precipitation types identified from crystal morphologies, daily precipitation amounts and isotopic composition. Our sampling period (2008-2010) encompasses a warmer year (2009, +1.2 °C with respect to 2 m air temperature long-term average 1996-2010), with larger total precipitation and snowfall amounts (14 and 76 % above sampling period average, respectively), and a colder and drier year (2010, -1.8 °C, 4 % below long-term and sampling period averages, respectively) with larger diamond dust amounts (49 % above sampling period average). Relationships between local meteorological data and precipitation isotopic composition are investigated at daily, monthly and inter-annual scale, and for the different types of precipitation. Water stable isotopes are more closely related to 2 m air temperature than to inversion temperature at all timescales (e.g. R2 = 0.63 and 0.44, respectively for daily values). The slope of the temporal relationship between daily δ18O and 2 m air temperature is approximately 2 times smaller (0.49 ‰ °C-1) than the average Antarctic spatial (0.8 ‰ °C-1) relationship initially used for the interpretation of EPICA Dome C records. In accordance with results from precipitation monitoring at Vostok and Dome F, deuterium excess is anti-correlated with δ18O at daily and monthly scales, reaching maximum values in winter. Hoar frost precipitation samples have a specific fingerprint with more depleted δ18O (about 5 ‰ below average) and higher deuterium excess (about 8 ‰ above average) values than other precipitation

  13. Seismic monitoring at Deception Island volcano (Antarctica): the 2010-2011 survey

    Science.gov (United States)

    Martín, R.; Carmona, E.; Almendros, J.; Serrano, I.; Villaseñor, A.; Galeano, J.

    2012-04-01

    As an example of the recent advances introduced in seismic monitoring of Deception Island volcano (Antarctica) during recent years, we describe the instrumental network deployed during the 2010-2011 survey by the Instituto Andaluz de Geofísica of University of Granada, Spain (IAG-UGR). The period of operation extended from December 19, 2010 to March 5, 2011. We deployed a wireless seismic network composed by four three-component seismic stations. These stations are based on 24-bit SL04 SARA dataloggers sampling at 100 sps. They use a PC with embedded linux and SEISLOG data acquisition software. We use two types of three-component seismometers: short-period Mark L4C with natural frequency of 1 Hz and medium-period Lennartz3D/5s with natural frequency of 0.2 Hz. The network was designed for an optimum spatial coverage of the northern half of Deception, where a magma chamber has been reported. Station locations include the vicinity of the Spanish base "Gabriel de Castilla" (GdC), Obsidianas Beach, a zone near the craters from the 1970 eruptions, and the Chilean Shelter located south of Pendulum Cove. Continuous data from the local seismic network are received in real-time in the base by wifi transmission. We used Ubiquiti Networks Nanostation2 antennas with 2.4 GHz, dual-polarity, 10 dBi gain, and 54 Mbps transmission rate. They have shown a great robustness and speed for real-time applications. To prioritize data acquisition when the battery level is low, we have designed a circuit that allows independent power management for the seismic station and wireless transmission system. The reception antenna located at GdC is connected to a computer running SEISCOMP. This software supports several transmission protocols and manages the visualization and recording of seismic data, including the generation of summary plots to show the seismic activity. These twelve data channels are stored in miniseed format and displayed in real time, which allows for a rapid evaluation of

  14. Trace metal concentrations of surface snow from Ingrid Christensen Coast, East Antarctica--spatial variability and possible anthropogenic contributions.

    Science.gov (United States)

    Thamban, Meloth; Thakur, Roseline C

    2013-04-01

    To investigate the distribution and source pathways of environmentally critical trace metals in coastal Antarctica, trace elemental concentrations were analyzed in 36 surface snow samples along a coast to inland transect in the Ingrid Christensen Coast of East Antarctica. The samples were collected and analyzed using the clean protocols and an inductively coupled plasma mass spectrometer. Within the coastal ice-free and ice-covered region, marine elements (Na, Ca, Mg, K, Li, and Sr) revealed enhanced concentrations as compared with inland sites. Along with the sea-salt elements, the coastal ice-free sites were also characterized by enhanced concentrations of Al, Fe, Mn, V, Cr, and Zn. The crustal enrichment factors (Efc) confirm a dominant crustal source for Fe and Al and a significant source for Cr, V, Co, and Ba, which clearly reflects the influence of petrological characteristics of the Larsemann Hills on the trace elemental composition of surface snow. The Efc of elements revealed that Zn, Cu, Mo, Cd, As, Se, Sb, and Pb are highly enriched compared with the known natural sources, suggesting an anthropogenic origin for these elements. Evaluation of the contributions to surface snow from the different sources suggests that while contribution from natural sources is relatively significant, local contamination from the increasing research station and logistic activities within the proximity of study area cannot be ignored.

  15. 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.

  16. Seasonal change of ice algal and phytoplankton assemblages in the Nella Fjord near Zhongshan Station, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The ice algal and phytoplankton assemblages were studied from Nella Fjord near Zhongshan Station, East Antarctica from April 12 to December 30, 1992. Algal blooms occurred about 3 cm thick on the bottom of sea ice in late April and mid November to early December respectively, and a phytoplankton bloom appeared in the underlying surface water in mid December following the spring ice algal bloom. The biomass in ice bottom was 1 to 3 orders of magnitude higher than that of surface water. Amphiprora kjellmanii, Berkeleya sp., Navicula glaciei, Nitzschia barkelyi, N. cylindrus /N. curta, N. lecointei and Nitzschia sp. were common in the sea ice temporarily or throughout the study period. The biomass in a certain ice segment was decreased gradually and the dominant species were usually succeeded as the season went on. Nitzschia sublineata and Dactyliosolen antarctica were two seasonal dominant species only observed in underlying water column. The assemblages between bottom of ice and underlying surface water were different except when spring ice algae bloomed. The evidence shows that the ice algal blooms occurred mainly by in situ growth of ice algae, and the phytoplankton bloom was mostly caused by the release of ice algae.

  17. Sedimentology and geochemistry of a perennially ice-covered epishelf lake in Bunger Hills Oasis, East Antarctica

    Science.gov (United States)

    Doran, P. T.; Wharton, R. A. Jr; Lyons, W. B.; Des Marais, D. J.; Andersen, D. T.; Wharton RA, J. r. (Principal Investigator)

    2000-01-01

    A process-oriented study was carried out in White Smoke lake, Bunger Hills, East Antarctica, a perennially ice-covered (1.8 to 2.8 m thick) epishelf (tidally-forced) lake. The lake water has a low conductivity and is relatively well mixed. Sediments are transferred from the adjacent glacier to the lake when glacier ice surrounding the sediment is sublimated at the surface and replaced by accumulating ice from below. The lake bottom at the west end of the lake is mostly rocky with a scant sediment cover. The east end contains a thick sediment profile. Grain size and delta 13C increase with sediment depth, indicating a more proximal glacier in the past. Sedimentary 210Pb and 137Cs signals are exceptionally strong, probably a result of the focusing effect of the large glacial catchment area. The post-bomb and pre-bomb radiocarbon reservoirs are c. 725 14C yr and c. 1950 14C yr, respectively. Radiocarbon dating indicates that the east end of the lake is >3 ka BP, while photographic evidence and the absence of sediment cover indicate that the west end has formed only over the last century. Our results indicate that the southern ice edge of Bunger Hills has been relatively stable with only minor fluctuations (on the scale of hundreds of metres) over the last 3000 years.

  18. [Archaeal diversity in permafrost deposits of Bunger Hills Oasis and King George Island (Antarctica) according to the 16S rRNA gene sequencing].

    Science.gov (United States)

    Karaevskaia, E S; Demchenko, L S; Demidov, N É; Rivkina, E M; Bulat, S A; Gilichinskiĭ, D A

    2014-01-01

    Archaeal communities of permafrost deposits of King George Island and Bunger Hills Oasis (Antarctica) differing in the content of biogenic methane were analyzed using clone libraries of two 16S rRNA gene regions. Phylotypes belonging to methanogenic archaea were identified in all horizons.

  19. Determination of element composition of three lichens and their distribution in King George Island, Antarctica

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Cross-section slices of Usnea antarctica Du Rietz, Usnea aurantiaco-atra (Jacq.) Bory. and Cladonia sp. at upper, middle and basal positions were prepared, respectively. The element composition and relative content were determined by SEM and EDS at the surface, intermediate and inner layers in each slice, respectively. The result indicated that the composition of element is mostly same in these lichens. The relative content of Al, Si, K and Ca elements is high, and P is close at each position. The result is of benefit to study the structure and physiological characteristics of lichens, and to analyze geological environment in Antarctica.

  20. Firn density profile at Megadunes, East Antarctica, calls for an improved densification model for low accumulation sites.

    Science.gov (United States)

    Suwa, M.; Severinghaus, J. P.

    2004-12-01

    We report a density profile of the firn at Megadunes, East Antarctica (80o78'S; 124o50'E). The Megadunes site is characterized by a low mass accumulation rate (2.9 g/cm2/yr) and cold temperature (mean annual = -49.5oC). Validating existing firn densification models using a density profile of such a site is important because such models, either purely empirical or mechanistic, have been calibrated with few sites that are analogous to a glacial condition (ultralow accumulation and temperature). We make use of CO2 concentrations in the lock-in (or non-diffusive) zone to obtain the accumulation rate, assuming that the gas in the lock-in zone ages at the same rate as the surrounding ice [Battle et al., 1996], and assuming that the gas enclosure rate must equal the long-term mean accumulation rate. This estimate is preliminary and may change when results from beta analysis of cores become available. Our density profile shows that the widely used pure empirical model by Herron and Langway [1980] overestimates the close-off depth by 16 %, and the semi-mechanistic model by Pimienta and Barnola [Barnola et al., 1991] also overestimates the close-off depth by 26 %. Our study at the Megadunes site indicates that the δ 15N of N2 paradox for glacial ice from East Antarctica would have partly resulted from a poorly calibrated densification model for a `glacial-like' condition and a thick convective zone as we observed at the Megadunes site [Severinghaus et al., in prep].

  1. 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

  2. Diversity and cold adaptation of culturable endophytic fungi from bryophytes in the Fildes Region, King George Island, maritime Antarctica.

    Science.gov (United States)

    Zhang, Tao; Zhang, Yu-Qin; Liu, Hong-Yu; Wei, Yu-Zhen; Li, Hai-Long; Su, Jing; Zhao, Li-Xun; Yu, Li-Yan

    2013-04-01

    Endophytic fungi associated with three bryophyte species in the Fildes Region, King George Island, maritime Antarctica, that is, the liverwort Barbilophozia hatcheri, the mosses Chorisodontium aciphyllum and Sanionia uncinata, were studied by culture-dependent method. A total of 128 endophytic fungi were isolated from 1329 tissue segments of 14 samples. The colonization rate of endophytic fungi in three bryophytes species were 12.3%, 12.1%, and 8.7%, respectively. These isolates were identified to 21 taxa, with 15 Ascomycota, 5 Basidiomycota, and 1 unidentified fungus, based on morphological characteristics and sequence analyses of ITS region and D1/D2 domain. The dominant fungal endophyte was Hyaloscyphaceae sp. in B. hatcheri, Rhizoscyphus sp. in C. aciphyllum, and one unidentified fungus in S. uncinata; and their relative frequencies were 33.3%, 32.1%, and 80.0%, respectively. Furthermore, different Shannon-Weiner diversity indices (0.91-1.99) for endophytic fungi and low endophytic fungal composition similarities (0.19-0.40) were found in three bryophyte species. Growth temperature tests indicated that 21 taxa belong to psychrophiles (9), psychrotrophs (11), and mesophile (1). The results herein demonstrate that the Antarctic bryophytes are an interesting source of fungal endophytes and the endophytic fungal composition is different among the bryophyte species, and suggest that these fungal endophytes are adapted to cold stress in Antarctica.

  3. Embedded ARM System for Volcano Monitoring in Remote Areas: Application to the Active Volcano on Deception Island (Antarctica

    Directory of Open Access Journals (Sweden)

    Luis Miguel Peci

    2014-01-01

    Full Text Available This paper describes the development of a multi-parameter system for monitoring volcanic activity. The system permits the remote access and the connection of several modules in a network. An embedded ARMTM processor has been used, allowing a great flexibility in hardware configuration. The use of a complete Linux solution (DebianTM as Operating System permits a quick, easy application development to control sensors and communications. This provides all the capabilities required and great stability with relatively low energy consumption. The cost of the components and applications development is low since they are widely used in different fields. Sensors and commercial modules have been combined with other self-developed modules. The Modular Volcano Monitoring System (MVMS described has been deployed on the active Deception Island (Antarctica volcano, within the Spanish Antarctic Program, and has proved successful for monitoring the volcano, with proven reliability and efficient operation under extreme conditions. In another context, i.e., the recent volcanic activity on El Hierro Island (Canary Islands in 2011, this technology has been used for the seismic equipment and GPS systems deployed, thus showing its efficiency in the monitoring of a volcanic crisis.

  4. Embedded ARM system for volcano monitoring in remote areas: application to the active volcano on Deception Island (Antarctica).

    Science.gov (United States)

    Peci, Luis Miguel; Berrocoso, Manuel; Fernández-Ros, Alberto; García, Alicia; Marrero, José Manuel; Ortiz, Ramón

    2014-01-02

    This paper describes the development of a multi-parameter system for monitoring volcanic activity. The system permits the remote access and the connection of several modules in a network. An embedded ARM™ processor has been used, allowing a great flexibility in hardware configuration. The use of a complete Linux solution (Debian™) as Operating System permits a quick, easy application development to control sensors and communications. This provides all the capabilities required and great stability with relatively low energy consumption. The cost of the components and applications development is low since they are widely used in different fields. Sensors and commercial modules have been combined with other self-developed modules. The Modular Volcano Monitoring System (MVMS) described has been deployed on the active Deception Island (Antarctica) volcano, within the Spanish Antarctic Program, and has proved successful for monitoring the volcano, with proven reliability and efficient operation under extreme conditions. In another context, i.e., the recent volcanic activity on El Hierro Island (Canary Islands) in 2011, this technology has been used for the seismic equipment and GPS systems deployed, thus showing its efficiency in the monitoring of a volcanic crisis.

  5. THE COMPILATION OF A DTM AND A NEW SATELLITE IMAGE MAP FOR KING GEORGE ISLAND,ANTARCTICA

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    An improved topographic database for King George Island,one of the most frequently visited regions in Antarctica,is presented.A first step consisted in combining data from differential GPS surveys gained during the austral summers 1997~1998 and 1999~2000,with the current coastline from a SPOT satellite image mosaic,topographic information from existing maps and from the Antarctic Digital Database.From this data sets,a digital terrain model (DTM) was generated using Arc/Info GIS.In a second step,a satellite image map at the scale 1∶100 000 was assembled from contour lines derived from the DTM and the satellite mosaic.A lack of accurate topographic information in the eastern part of the island was identified.Additional topographic surveying or SAR interferometry should be used to improve the data quality in that area.The GIS integrated database will be indispensable for glaciological and climatological studies and administrative and scientific purposes.In future,the application of GIS techniques will be mandatory for environmental impact studies and environmental monitoring as well as for management plans on King George Island.

  6. Persistent organic pollutants in blood samples of Southern Giant Petrels (Macronectes giganteus) from the South Shetland Islands, Antarctica.

    Science.gov (United States)

    Colabuono, Fernanda I; Vander Pol, Stacy S; Huncik, Kevin M; Taniguchi, Satie; Petry, Maria V; Kucklick, John R; Montone, Rosalinda C

    2016-09-01

    Seabirds play an important role as top consumers in the food web and can be used as biomonitors of exposure to pollutants. Contamination studies involving non-destructive sampling methods are of considerable importance, allowing better evaluation of the levels of pollutants and their toxic effects. In the present study, organohalogen contaminants were analyzed in 113 blood samples from Southern Giant Petrel (Macronectes giganteus) adults and chicks collected in the austral summer of 2011/2012 and 2012/2013 from colonies on Elephant and Livingston Islands, South Shetland, Antarctica. Polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), pentachlorobenzene (PeCB), mirex, dichlorodiphenyltrichloroetane and derivatives (DDTs) and chlordanes were detected in all birds, whereas polybrominated diphenyl ethers (PBDEs) were not detected in any blood samples. No significant differences were found in organochlorine levels between sampling events. Adults exhibited significantly higher levels than chicks, except for PeCB. PCBs, HCB, mirex and DDTs were statistically similar in males and females from Elephant Island. Females on Livingston Island exhibited higher HCB values than males, but no sex differences were found regarding other organochlorines. The similarity in organochlorine levels between sexes in birds with very marked sexual segregation in feeding habits during the breeding season may indicate that significant amounts of contaminants are acquired during migration to lower latitudes, when the diets of males and females are similar. Birds sampled on Livingston Island exhibited significantly lower levels of PCBs, HCB, DDTs, mirex and chlordanes in comparison to those on Elephant Island, which could be the result of distinct foraging patterns between the two colonies. Organochlorine levels were similar between years in birds captured in two consecutive breeding seasons. Blood samples from Southern Giant Petrels adults and chicks proved to be useful for the comparison

  7. Sedimentary environments of the Cenozoic sedimentary debris found in the moraines of the Grove Mountains, east Antarctica and its climatic implications

    Institute of Scientific and Technical Information of China (English)

    FANG Aimin; LIU Xiaohan; LEE Jong Ik; LI Xiaoli; HUANG Feixin

    2004-01-01

    During the field work of the 1998~1999's and 1999~2000's Chinese National Antarctic Research Expedition (CHNARE) in the Grove Mountains, east Antarctica, some Cenozoic sedimentary debris are found in two terminal moraine banks over the blue ice near Harding Mount in the center of this region. All the debris are of characteristics of glaciogenic diamicton and belong to the products of the glacial movements of the East Antarctic Ice Sheet. In this paper, the authors make a detailed study on the sedimentary environments of the sedimentary debris through petrologic, sedimentological, mineralogical, and geo-chemical methods. Characteristics of their sedimentary textures and structures, grain size distributions, quartz grains' surface textures and features, together with their geo-chemical compositions all show that these sedimentary rocks are a kind of subglacial lodgement tills which are deposited in the ice sheet frontal area by reactions of glacial movements and glaciogenic melt water. Their palaeoenvironmental implications in revealing the retreat history of East Antarctic Ice Sheet are discussed. The authors draw the conclusion from current study that the glacial frontal of the East Antarctica Ice Sheet might have been retreated to this area during the Pliocene Epoch, which represents a warm climate event accompanied by a large-scale ice sheet retreat in Antarctica at that time.

  8. Gastrointestinal helminths of Gentoo penguins (Pygoscelis papua) from Stranger Point, 25 de Mayo/King George Island, Antarctica.

    Science.gov (United States)

    Diaz, Julia Inés; Fusaro, Bruno; Longarzo, Lucrecia; Coria, Néstor Rubén; Vidal, Virginia; Jerez, Silvia; Ortiz, Juana; Barbosa, Andrés

    2013-05-01

    The aim of this work is to contribute to the knowledge of gastrointestinal parasites of the Gentoo penguin (Pygoscelis papua) from 25 de Mayo/King George Island (South Shetlands, Antarctica). Gastrointestinal tracts of 37 fresh dead individuals (21 chicks, 10 juveniles, and 6 adults) were collected from December 2006 to February 2012 and examined for macroparasites. Four adult parasite species were found: one Cestoda species (Parorchites zederi), two Nematoda species (Stegophorus macronectes and Tetrameres wetzeli), and one Acanthocephalan (Corynosoma shackletoni). Two species of immature acanthocephalans, Corynosoma hamanni and Corynosoma bullosum, were found in a single host. This is the first record of Tetrameres wetzeli in Gentoo penguins. The low parasite richness observed could be related to the stenophagic and pelagic diet of this host species which feeds almost exclusively on krill.

  9. 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

  10. The economic determinants of Greek return migration to the islands of the East Aegean.

    Science.gov (United States)

    Robolis, S; Xideas, E

    1996-01-01

    "The purpose of this article is to investigate the economic determinants of Greek return migration to the islands of the East Aegean, a region comprising hundreds of islands of different size in four administrative departments....[It] examines the sensitivity of return migration flows to changes in economic variables which influence decisions to return....The purpose...is to investigate the effect on return migration not only of economic development in the host country (push factors) but also of economic development in the islands of the East Aegean (pull factors), given their isolation from the mainland and their different economic structures." (SUMMARY IN SPA AND FRE)

  11. Ultrastructural observations on five pioneer soil algae from ice denuded areas (King George Island, West Antarctica)

    OpenAIRE

    MASSALSKI, ANDRZEJ; Mrozinska ,Teresa; Olech, Maria

    2001-01-01

    Morphological observations were made using transmission electron microscopy on five species of green soil algae, including Chlorosarcinopsis cf. gelatinosa Chantanachat & Bold, Muriella decolor visher, Tetracystis aeria Brown & Bold, Tetracystis pampae Brown & bold, and Stichococcus bacillaris Nageli. With an exception of the latter species, they are all new records in Antarctica. These species were the important pioneers in the colonization process of the areas recently denuded of ice. Colle...

  12. Lateral and vertical distribution of soil organic carbon in recently deglaciated areas of Elephant Point (Livingstone island, Maritime Antarctica)

    Science.gov (United States)

    Navas, Ana; Oliva, Marc; Ruiz-Fernández, Jesús; Quijano, Laura; Gaspar, Leticia; Lizaga, Iván

    2017-04-01

    In Maritime Antarctica important environmental changes are affecting ice-free environments of the South Shetland Islands and the northern Antarctica Peninsula. In the Elephant Point Peninsula (Livingstone Island) a rapid glacier retreat during the last decades has exposed already around 20% of its 1.16 km2 surface. Despite soil development is taken place in these new created lands little is known on the characteristics and properties of soils on different parent materials and landforms. One of the main soil properties is the organic carbon but the SOC pool dynamics in Antarctica environments is still poorly understood. This work aims to gain knowledge on the lateral and vertical variations of soil organic carbon (SOC) and organic carbon fractions in surface profiles that have been exposed succeeding the phases of glacier retreat. To this purpose a sampling scheme following the direction of the glacier retreat was established along a moraine extending from the western to the eastern coastlines and a sequence of Holocene marine terraces in Elephant Point. To assess the lateral and vertical variations of SOC and SOC fractions a total of 10 sites were sampled until a depth of 12 cm then sectioned at 3 cm depth intervals. According to its chemical stability and turnover times, SOC can be divided into the active carbon fraction (ACF) composed of labile aliphatic and carboxyl groups with turnover rates of days to few years and a more stable refractory aromatic carbon fraction (SCF) with turnover rates from few years to centuries, highly resistant to microbial and chemical decomposition. The SOC content (%) was measured at 550 °C by the dry combustion method using a LECO, RC-612 multiphase carbon analyser. For the characterization of the active and stable carbon fractions the temperature of the furnace was stepped at 350 °C and 550 °C, respectively. Estimates of SOC and SOC fractions inventories (kg m-2) were done to assess their stocks on the different landforms. SOC

  13. 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.

  14. 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. PMID:24498126

  15. Distribution of ice thickness and subglacial topography of the “Chinese Wall” around Kunlun Station, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    Cui Xiang-Bin; Sun Bo; Su Xiao-Gang; Guo Jing-Xue

    2016-01-01

    As fundamental parameters of the Antarctic Ice Sheet, ice thickness and subglacial topography are critical factors for studying the basal conditions and mass balance in Antarctica. During CHINARE 24 (the 24th Chinese National Antarctic Research Expedition, 2007/08), the research team used a deep ice-penetrating radar system to measure the ice thickness and subglacial topography of the “Chinese Wall” around Kunlun Station, East Antarctica. Preliminary results show that the ice thickness varies mostly from 1600 m to 2800 m along the “Chinese Wall”, with the thickest ice being 3444 m, and the thinnest ice 1255 m. The average bedrock elevation is 1722 m, while the minimum is just 604 m. Compared with the northern side of the ice divide, the ice thickness is a little greater and the subglacial topography lower on the southern side, which is also characterized by four deep valleys. We found no basal freeze-on ice in the Gamburtsev Subglacial Mountains area, subglacial lakes, or water bodies along the “Chinese Wall”. Ice thickness and subglacial topography data extracted from the Bedmap 2 database along the “Chinese Wall” are consistent with our results, but their resolution and accuracy are very limited in areas where the bedrock fl uctuates intensely. The distribution of ice thickness and subglacial topography detected by ice-penetrating radar clarifi es the features of the ice sheet in this “inaccessible” region. These results will help to advance the study of ice sheet dynamics and the determination of future locations of the GSM’s geological and deep ice core drilling sites in the Dome A region.

  16. Late Pliocene diatoms in a diatomite from Prydz Bay, East Antarctica

    Science.gov (United States)

    Mahood, A.D.; Barron, J.A.

    1996-01-01

    Very well-preserved Pliocene diatoms from a diatomite unit interbedded within glacial sediments at Ocean Drilling Program Site 742 in Prydz Bay, Antarctica are documented and illustrated. The presence of Thalassiosira kolbei, T. torokina, Actinocyclus actinochilus, A. karstenii and the absence of Nitzschia interfrigidaria. T. insigna and T. vulnifica in Sample 119-742A-15R-4, 44-46cm constrain its age to ca. 2.2-1.8 Ma (late Pliocene). Diatoms associated with sea ice constitute 35% of the Pliocene diatom assemblage, compared with 71% of the modern sediment assemblage at the site, suggesting that sea ice was present during the late Pliocene period of deposition of the sample, although it probably was not the significant feature it is today. Thalassiosira ellitipora (Donahue) Fenner is described and illustrated in detail and is validly published. An expanded description and numerous illustrations are also presented for T. torokina Brady.

  17. Inorganic chemistry, petrography and palaeobotany of Permian coals in the Prince Charles Mountains, East Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Holdgate, G.R. [School of Earth Sciences, The University of Melbourne, Victoria, 3010 (Australia); McLoughlin, S. [School of Natural Resource Sciences, Queensland University of Technology, P.O. Box 2434, Brisbane, Queensland 4001 (Australia); Drinnan, A.N. [School of Botany, The University of Melbourne, Victoria, 3010 (Australia); Finkelman, R.B.; Willett, J.C.; Chiehowsky, L.A. [U.S. Geological Survey, Mail Stop 956, Reston, VA 20092 (United States)

    2005-07-20

    Sampled outcrops of Permian coal seams of the Bainmedart Coal Measures in the Lambert Graben, eastern Antarctica, have been analysed for their proximates, ultimates, ash constituents and trace elements. A similar series of samples has been analysed for their principle maceral and microlithotype components and vitrinite reflectance. The coals are sub-bituminous to high volatile bituminous in rank; maturity increases markedly in southern exposures around Radok Lake where the oldest part of the succession is exposed and some strata have been intruded by mafic dykes and ultramafic sills. The coal ash is mostly silica and aluminium oxides, indicating that the mineral ash component is mostly quartz and various clay minerals. The ratio of silica to aluminium oxides appears to increase in an upward stratigraphic direction. The coal macerals include a relatively high liptinite content (mainly sporinite) that is significantly higher than for typical Gondwana coals. Greater degrees of weathering within the floodbasin/peat mire environments associated with climatic drying towards the end of the Permian might account for both preferential sporopollenin preservation and increased silica:aluminium oxide ratios up-section. Correlation of the coal maceral components to adjacent peninsula India coals indicates the closest comparative coals of similar age and rank occur within the Godavari Basin, rather then the Mahanadi Basin, which is traditionally interpreted to have been contiguous with the Lambert Graben before Gondwanan breakup. The petrological characteristics suggest that either previous interpretations of Palaeozoic basin alignments between Antarctica and India are incorrect, or that environmental settings and post-Permian burial histories of these basins were strongly independent of their tectonic juxtaposition. A permineralized peat bed within the succession reveals that the coals predominantly comprise wood- and leaf-rich debris derived from low-diversity forest

  18. 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

  19. Microstructural records of multiple retrograde local H2O supplement in the pelitic gneiss, Lützow-Holm Complex at Akarui Point, East Antarctica

    OpenAIRE

    Nakamura, Aya; Kitamura, Masao; Kawakami, Tetsuo

    2014-01-01

    The alkali-feldspar and biotite in the sillimanite-biotite-garnet gneiss from East Antarctica preserves characteristic microstructural evidence of multi-stage H2O supplement during the retrograde metamorphism. The first microstructural evidence is the "zoned feldspar, " in which the mesoperthitic zone, the anti-perthitic zone, and lamella-free plagioclase zone coexist within a single crystal. They are occasionally found next to biotite, and are always depleted in orthoclase (Or) component tow...

  20. 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.

  1. A PRIMARY STUDY OF FOSSIL HILL FLORA FROM FILDES PENINSULA OF KING GEORGE ISLAND, ANTARCTICA

    Institute of Scientific and Technical Information of China (English)

    1990-01-01

    The fossil plants studied in this paper were collected by the Chinese Antarctic Expeditions (1986—1987 and 1987—1988) from the locality Fossil Hill on the Fildes Peninsula southwest of the King George Island of the South Shetland Islands.

  2. Unique manifestations of mixed-phase cloud microphysics over Ross Island and the Ross Ice Shelf, Antarctica

    Science.gov (United States)

    Scott, Ryan C.; Lubin, Dan

    2016-03-01

    Spaceborne radar and lidar observations from the CloudSat and CALIPSO satellites are used to compare seasonal variations in the microphysical and radiative properties of clouds over Ross Island, Antarctica, with two contrasting Arctic atmospheric observatories located in Barrow, Alaska, and Summit, Greenland. At Ross Island, downstream from recurrent intrusions of marine air over the West Antarctic Ice Sheet and eastern Ross Ice Shelf, clouds exhibit a tendency toward the greatest geometrical thickness and coldest temperatures in summer, the largest average ice water content, IWC, at low altitude during summer and autumn, the most abundant IWC at cold mixed-phase temperatures (-40°C

  3. 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

  4. The oldest elasmosaurs (Sauropterygia, Plesiosauria from Antarctica, Santa Marta Formation (upper Coniacian? Santonian–upper Campanian and Snow Hill Island Formation (upper Campanian–lower Maastrichtian, James Ross Island

    Directory of Open Access Journals (Sweden)

    José P. O'Gorman

    2012-10-01

    Full Text Available Elasmosaurs are recorded for the first time in the Lachman Crags Member (Beta Member of the Santa Marta Formation (lower Campanian and in the Herbert Sound Member of the Snow Hill Island Formation (upper Campanian. These are the first elasmosaurids from James Ross Island, Antarctic Peninsula. These records greatly improve our knowledge of the taxonomic diversity of plesiosaurs of the Santa Marta Formation and Herbert Sound Member of the Snow Hill Island Formation, and extend the lower limit of the record of Elasmosauridae in Antarctica to the lower Campanian, making this the oldest record of an Antarctic elasmosaur.

  5. Oxygen and hydrogen stable isotope content in daily-collected precipitation samples at Dome C, East Antarctica

    Science.gov (United States)

    Dreossi, Giuliano; Stenni, Barbara; Del Guasta, Massimo; Bonazza, Mattia; Grigioni, Paolo; Karlicek, Daniele; Mognato, Riccardo; Scarchilli, Claudio; Turchetti, Filippo; Zannoni, Daniele

    2016-04-01

    Antarctic ice cores allow to obtain exceptional past climate records, thanks to their water stable isotope content, which provides integrated tracers of the atmospheric water cycle and local climate. Low accumulation sites of the East Antarctic plateau provide the oldest ice core records, with the record-breaking EPICA Dome C drilling covering the last eight climate cycles. However, the isotope-temperature relationship, commonly used to derive the temperature, may be characterized by significant geographical and temporal variations. Moreover, post-depositional effects may further complicate the climate interpretation. A continuous series of precipitation data is needed in order to gain a better understanding of the factors affecting the water stable isotopes in Antarctic precipitation at a specific site. In this study, we use the first and so-far only multi-year series of daily precipitation sampling and isotope measurements from the French-Italian Concordia Station, located at Dome C in East Antarctica (75°06'S 123°21'E; elevation: 3233 m a.s.l.; mean annual temperature: -54.5°C; snow accumulation rate: 25 kg m-2 yr-1), where the oldest deep Antarctic ice core has been retrieved. Surface air temperature data have been provided by the US automatic weather station (AWS), placed 1.5 km away from the base, while tropospheric temperature profiles are obtained by means of a radiosonde, launched once per day by the IPEV/Italian Antarctic Meteo-climatological Observatory. The new dataset also enables us for the first time to study the isotope-temperature relationship distinguishing between different types of precipitation, namely diamond dust, hoar frost and snowfall, identified by the observations carried out by the winter-over personnel collecting the snow samples. Here we present the complete data series of water stable isotopes in precipitation at Dome C spanning the time period from 2008 to 2014, in the framework of the PNRA PRE-REC project.

  6. Large flux of iron from the Amery Ice Shelf marine ice to Prydz Bay, East Antarctica

    Science.gov (United States)

    Herraiz-Borreguero, L.; Lannuzel, D.; van der Merwe, P.; Treverrow, A.; Pedro, J. B.

    2016-08-01

    The Antarctic continental shelf supports a high level of marine primary productivity and is a globally important carbon dioxide (CO2) sink through the photosynthetic fixation of CO2 via the biological pump. Sustaining such high productivity requires a large supply of the essential micronutrient iron (Fe); however, the pathways for Fe delivery to these zones vary spatially and temporally. Our study is the first to report a previously unquantified source of concentrated bioavailable Fe to Antarctic surface waters. We hypothesize that Fe derived from subglacial processes is delivered to euphotic waters through the accretion (Fe storage) and subsequent melting (Fe release) of a marine-accreted layer of ice at the base of the Amery Ice Shelf (AIS). Using satellite-derived Chlorophyll-a data, we show that the soluble Fe supplied by the melting of the marine ice layer is an order of magnitude larger than the required Fe necessary to sustain the large annual phytoplankton bloom in Prydz Bay. Our finding of high concentrations of Fe in AIS marine ice and recent data on increasing rates of ice shelf basal melt in many of Antarctica's ice shelves should encourage further research into glacial and marine sediment transport beneath ice shelves and their sensitivity to current changes in basal melt. Currently, the distribution, volume, and Fe concentration of Antarctic marine ice is poorly constrained. This uncertainty, combined with variable forecasts of increased rates of ice shelf basal melt, limits our ability to predict future Fe supply to Antarctic coastal waters.

  7. Seasonal variations of the near surfacelayer parameters over the Antarctic ice sheet in Princess Elizabeth Land, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Analysis of sensible heat flux(Qh), latent heat flux (Qe), Richardson number(Ri),bulk transport coefficient(Cd)and katabatic windsare presented by using the meteorological data in the near surface layer from an automatic weather station (AWS)in Princess Elizabeth Land, East Antarctica ice sheet and the data of corresponding period at Zhongshan station in 2002.It shows that annual mean air temperature at LGB69 is-25.(6.)C, which is 16.(4.)C lower than that at Zhongshan,where the elevation is lower and located on the coast.The temperature lapse rate is about 1.0°C/110 m for the initial from coast to inland.The turbulence heat flux at LGB69 displays obvious seasonal variations with the average sensible heat flux 17.9 W/m2 and latent heat flux -0.9 W/m2.The intensity (Qh+Qe) of coolling source is-18.8 W/m2 meaning the snow surface layer obtains heat from atmos phere.The near surface atmosphere is near-neutral stratified with bulk transport coefficients (Cd) around 2.8x10-3 ,and it is near constant when the wind speed higher than 8 m/s.The speed and the frequency of easterly Katabatic winds at LGB69 were higher than that at Zbongshan Station.

  8. Thermodynamic properties of snow cover on sea ice during the austral summer in Prydz Bay, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    HAN Hongwei; CHENG Peng; LI Zhijun; LEI Ruibo; LU Peng

    2014-01-01

    The thermodynamic properties of snow cover on sea ice play a key role in the ice-ocean-atmosphere system and have been a focus of recent scientiifc research. In this study, we investigated the thermodynamic properties of snow cover on sea ice in the Nella Fjord, Prydz Bay, East Antarctica (69°20′S, 76°07′E), near the Chinese Antarctic Zhongshan Station. Our observations were carried out during the 29th Chinese National Antarctic Research Expedition. We found that the vertical temperature proifle of snow cover changed considerably in response to changes in air temperature and solar radiation during the summer. Associated with the changes in the temperature proifle were lfuctuations in the temperature gradient within the upper 10 cm of the snow cover. Results of previous research have shown that the thermal conductivity of snow is strongly correlated with snow density. To calculate the thermal conductivity in this study, we measured densities in three snow pits. The calculated thermal conductivity ranged from 0.258-0.569 W∙m-1∙K-1. We present these datasets to show how involved parameters changed, and to contribute to a better understanding of melting processes in the snow cover on sea ice.

  9. Introduction: SIPEX-2: A study of sea-ice physical, biogeochemical and ecosystem processes off East Antarctica during spring 2012

    Science.gov (United States)

    Meiners, Klaus M.; Golden, Ken M.; Heil, Petra; Lieser, Jan L.; Massom, Rob; Meyer, Bettina; Williams, Guy D.

    2016-09-01

    This editorial introduces a suite of articles resulting from the second Sea Ice Physics and Ecosystems eXperiment (SIPEX-2) voyage by presenting some background information on the study area and Antarctic sea-ice conditions, and summarising the key findings from the project. Using the Australian icebreaker RV Aurora Australis, SIPEX-2 was conducted in the area between 115-125°E and 62-66°S off East Antarctica during September to November 2012. This region had been sampled during two previous experiments, i.e. ARISE in 2003 (Massom et al., 2006a) and SIPEX in 2007 (Worby et al., 2011a). The 2012 voyage combined traditional and newly developed sampling methods with satellite and other data to measure sea-ice physical properties and processes on large scales, which provided context for biogeochemical and ecological case studies. The specific goals of the SIPEX-2 project were to: (i) measure the spatial variability in sea-ice and snow-cover properties over small- to regional-length scales; (ii) improve understanding of sea-ice kinematic processes; and (iii) advance knowledge of the links between sea-ice physical characteristics, sea-ice biogeochemical cycling and ice-associated food-web dynamics. Our field-based activities were designed to inform modelling approaches and to improve our capability to assess impacts of predicted changes in Antarctic sea ice on Southern Ocean biogeochemical cycles and ecosystem function.

  10. New data on the Late Pleistocene and Holocene glacial, climate and relative sea-level changes at Fildes Peninsula, King George Island (South Shetlands Islands, West Antarctica)

    Science.gov (United States)

    Verkulich, Sergey; Pushina, Zina; Tatur, Andrej

    2010-05-01

    New data on the Late Pleistocene and Holocene glacial, climate and relative sea-level changes at Fildes Peninsula, King George Island (South Shetlands Islands, West Antarctica) Verkulich S. R. (Arctic and Antarctic Research Institute, St. Petersburg, Russia) Pushina Z.V. (Arctic and Antarctic Research Institute, St. Petersburg, Russia) Tatur A. (Department of Antarctic Biology, Polish Academy of Sciences, Warsaw, Poland) During the 2008-2009 austral summer, co-operative Russian - Polish paleogeographical investigations allowed to refine the understanding of the past environmental events at Fildes Peninsula, King George Island. Old marine deposits (ca. 30000 yrs BP) with shells, whale bones and marine algae in situ were found in the western coastal and northern inland territories at the altitudes of 20-40 m a.s.l. that evidences the covering of considerable part of the peninsula by relatively warm sea waters before the Last Glacial Maximum. Quite good preservation of these deposits supposes relatively small thickness and weak erosional potential of ice masses overlying the area during the LGM. The early Holocene phase of the peninsula deglaciation was caused by both climate warming and marine transgression, which left the deposits with fossil flora and fauna at heights up to 15 m a.s.l. (maximum rise of the relative sea-level 7000-8000 yrs BP). During the middle Holocene, glacier contraction in the area continued (on the whole) due to mainly favorable climatic conditions. The presence of marine and terrestrial deposit blocks (with shells, algae, mosses) in moraine ridges on the surface of Collins Ice Cap signifies that this glacier could vanish from the peninsula during climate optimum (ca. 4000-3000 yrs BP). The processes of new formation and growth of the ice cap started probably ca. 2000 yrs BP; within the last 1000 years the limited advance of the glacier occurred (likely corresponding to the Little Ice Age), and was replaced then by modern process of its decay.

  11. Hawaiian Islands East-West Deflections (DEFLEC96)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This 2' surface deflection of the vertical grid for the Principal Hawaiian Islands is the DEFLEC96 model. The computation used about 61,000 terrestrial and marine...

  12. Elements in the hair of South-east Asian islanders.

    Science.gov (United States)

    Foo, S C; Tan, T C

    1998-01-19

    Mercury (Hg), lead (Pb), cadmium (Cd) and copper (Cu) in hair samples from Singapore island (85 samples) and two islands off Batam, Indonesia (68 samples) were analysed to assess the environmental uptake of elements. Hair samples were washed with 0.1% Triton X-100 solution for 20 min in an ultrasonic bath, rinsed five times with de-ionized water and air dried. Ten to 20 mg of hair samples were digested with 1 ml of ultra-pure concentrated nitric acid in Parr bombs at 120 degrees C for 2 h. Hair digests were analysed by atomic absorption spectrophotometry (AAS). Hg was determined by the cold vapour AAS method and Pb, Cd and Cu by the electro-thermal graphite furnace AAS method. For Singapore hair, the contents of Cd (in microgram/g) averaged 0.17 (range 0.02-1.81); Cu 13.2 (range 3.1-70.1); Hg 5.92 (range 1.14-35.52); and Pb 6.74 (range 0.06-107.8). For the islands off Batam, Cd was 0.32 (range 0.06-1.80); Cu 21.1 (range 3.8-143.6); Hg 5.59 (range 0.78-60.86); and Pb 15.1 (range 0.13-116.6). Statistically significant differences in Cd, Pb and Hg contents were observed between the hair samples from Singapore and those of the islands off Batam in cumulative logit analysis. Hair from Singapore contained more Hg, but less Cd and Pb compared to hair from the islands off Batam. For Pb in hair, significant differences were also observed between the two islands off Batam (island 1, 18.9; and island 2, 10.2). These differences in hair metal contents are due to differences in community lifestyle (dietary, environmental or occupational intake).

  13. Net mass balance calculations for the Shirase Drainage Basin, east Antarctica, using the mass budget method

    Science.gov (United States)

    Nakamura, Kazuki; Yamanokuchi, Tsutomu; Doi, Koichiro; Shibuya, Kazuo

    2016-06-01

    We quantify the mass budget of the Shirase drainage basin (SHI), Antarctica, by separately estimating snow accumulation (surface mass balance; SMB) and glacier ice mass discharge (IMD). We estimated the SMB in the SHI, using a regional atmospheric climate model (RACMO2.1). The SMB of the mainstream A flow region was 12.1 ± 1.5 Gt a-1 for an area of 1.985 × 105 km2. Obvious overestimation of the model round the coast, ∼0.5 Gt a-1, was corrected for. For calculating the IMD, we employed a 15-m resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) with a digital elevation model (DEM) to determine the heights at the grounding line (GL), after comparison with the interpolated Bamber DEM grid heights; the results of this are referred to as the measured heights. Ice thickness data at the GL were inferred by using a free-board relationship between the measured height and the ice thickness, and considering the measured firn depth correction (4.2 m with the reference ice density of 910 kg m-3) for the nearby blue-ice area. The total IMD was estimated to be 14.0 ± 1.8 Gt a-1. Semi-empirical firn densification model gives the estimate within 0.1-0.2 Gt a-1 difference. The estimated net mass balance, -1.9 Gt a-1, has a two-σ uncertainty of ±3.3 Gt a-1, and probable melt water discharge strongly suggests negative NMB, although the associated uncertainty is large.

  14. 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.

  15. Analysis of Ionospheric Scintillation Characteristics in Sub-Antarctica Region with GNSS Data at Macquarie Island

    Science.gov (United States)

    Guo, Kai; Liu, Yang; Zhao, Yan; Wang, Jinling

    2017-01-01

    Ionospheric scintillation has a great impact on radio propagation and electronic system performance, thus is extensively studied currently. The influence of scintillation on Global Navigation Satellite System (GNSS) is particularly evident, making GNSS an effective medium to study characteristics of scintillation. Ionospheric scintillation varies greatly in relation with temporal and spatial distribution. In this paper, both temporal and spatial characteristics of scintillation are investigated based on Macquarie Island’s GNSS scintillation data collected from 2011 to 2015. Experiments demonstrate that occurrence rates of amplitude scintillation have a close relationship with solar activity, while phase scintillation is more likely to be generated by geomagnetic activity. In addition, scintillation distribution behaviors related to elevation and azimuth angles are statistically analyzed for both amplitude and phase scintillation. The proposed work is valuable for a deeper understanding of theoretical mechanisms of ionospheric scintillation in this region, and provides a reference for GNSS applications in certain regions around sub-Antarctica. PMID:28085087

  16. 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

  17. {sup 137}Cs in marine sediments of Admiralty Bay, King George Island, Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Paulo Alves de Lima [Instituto Oceanográfico, Universidade de São Paulo (IO-USP), Pça. do Oceanográfico, 191, Butantã, SP, 05508 900 (Brazil); Ribeiro, Andreza Portella, E-mail: andrezpr@usp.br [Instituto Oceanográfico, Universidade de São Paulo (IO-USP), Pça. do Oceanográfico, 191, Butantã, SP, 05508 900 (Brazil); Mestrado de Gestão Ambiental e Sustentabilidade, Universidade Nove de Julho (UNINOVE), Avenida Francisco Matarazzo, 612, prédio C, andar térreo, Água Branca, São Paulo, SP, 05001 100 (Brazil); Nascimento, Mylene Giseli do; Martins, Cesar de Castro [Centro de Estudos do Mar, Universidade Federal do Paraná (CEM-UFPR), Av. Beira-mar, no number, Balneário Pontal do Sul, Pontal do Paraná, PR, 83255 971 (Brazil); Mahiques, Michel Michaelovitch de; Montone, Rosalinda Carmelo; Figueira, Rubens Cesar Lopes [Instituto Oceanográfico, Universidade de São Paulo (IO-USP), Pça. do Oceanográfico, 191, Butantã, SP, 05508 900 (Brazil)

    2013-01-15

    The radionuclide cesium-137 ({sup 137}Cs) is produced exclusively by anthropogenic processes and primarily by nuclear explosions. This study determined the reference inventory that is {sup 137}Cs associated with the element's original input, and utilized the levels of activity of this radionuclide previously measured in five sediment profiles collected from Admiralty Bay, Antarctica, to investigate the mobility of this element in the environment. {sup 137}Cs has a half-life of 30 years. Because of this, it is environmentally persistent and has been shown to accumulate in marine organisms. The mean reference inventory of this radionuclide in Admiralty Bay sediments, determined using high resolution gamma ray spectrometry, was 20.23 ± 8.94 Bq m{sup −2}, and within the ambient {sup 137}Cs activity range. A model of {sup 137}Cs diffusion–convection was applied to data collected from 1 cm intervals in sediment cores with the aim of providing insights with respect to this element's behavior in sediments. Model results showed a significant correlation between measured and modeled values using the concentrations of {sup 137}Cs, and estimated input into the system from the global fallout of past nuclear tests and expected values based on local sedimentation rates. Results highlight the importance of accounting for the vertical diffusion of {sup 137}Cs in marine sediments when used as a tracer for environmental processes and for assessing potential bioavailability. - Highlights: ► Cesium-137 ({sup 137}Cs) is produced exclusively by anthropogenic processes. ► A model of diffusion–convection simulated {sup 137}Cs environmental behavior. ► This is important for assessing the bioavailability of this toxic element. ► In Antarctica ice cover influenced the input to the sediments.

  18. Post-depositional modification of NO-3 in snow layers at EastAntarctica and at the headwater of ürumqi River

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Acidic species, such as Nitrate, in polar snow and firn layers are “reversibly” deposited, and are sufficiently volatile to undergo significant postdepositional exchange between snow/firn and the atmosphere. Through comparison of the snowpit and snowpack nitrate concentrations from central East Antarctica and the headwater of ürumqi River, we conclude that the nitrate peaks in the uppermost surface snow layers in central Antarctica are not related to an atmospheric signal and must account for post-depositional effects. Such effects, however, are not found in the surface snowpack nitrate profiles from the headwater of ürumqi River. Two reasons may account for the post-depositional difference. At first, nitrate in the polar snow and firn layers appears to be hydrated ion, which can be taken up by the atmosphere, while at the headwater of ürumqi River it seems mainly as mineral ion, which assembles the behavior of aerosol-derived species that are “irreversibly” deposited and do not undergo significant post-depositional exchange with the atmosphere. Secondly, the chemical features of the snow and ice on the Antarctica are mainly determined by wet deposition, to the contrary, dry deposition is more significant at the headwater of lUrumqi River than that on the East Antarctic Plateau.

  19. Volcanic emissions of metals and halogens from White Island (New Zealand) and Erebus volcano (Antarctica) determined with chemical traps

    Science.gov (United States)

    Wardell, L. J.; Kyle, P. R.; Counce, D.

    2008-11-01

    Volcanic emission rates of As, Sb, Pb, Hg, Se, Cl, and F were determined at Erebus volcano, Antarctica and White Island, New Zealand, using chemical traps. The trace metal fluxes were determined by combining the species to S ratios in the solutions with SO 2 emission rates measured by correlation spectrometry at the two volcanoes. At Erebus volcano, fluxes for the metals Pb and Hg were 2.0 × 10 - 4 and 8.1 × 10 - 6 kg s - 11 , respectively. Fluxes for Cl, F, As, Sb and Se (0.35, 0.15, 2.5 × 10 - 4 , 1.2 × 10 - 5 , and 4.5 × 10 - 6 kg s - 1 , respectively) agreed within error limits for values determined previously by the LiOH impregnated filter method [Zreda-Gostynska, G., Kyle, P., Finnegan, D., Prestbo, K., 1997. Volcanic gas emissions from Mount Erebus and their impact on the Antarctic environment. Journal of Geophysical Research, 102(B7): 15039-15055.], demonstrating the utility of the chemical trap method. A fall in the As/S ratio from 7 × 10 - 4 in 1997/1999 to 3 × 10 - 4 in 2000 at Erebus coincided with a change in the frequency and style of eruptive activity that may have been due to injection of magma into the system. At White Island, chemical trap data indicated fluxes of Cl = 0.90, F = 0.0079, Pb = 2.7 × 10 - 4 , Hg = 1.1 × 10 - 5 , As = 1.3 × 10 - 4 , Sb = 1.9 × 10 - 5 and Se = 1.5 × 10 - 5 kg s - 1 . Samples collected 600 m downwind of the active crater were comparable to samples collected adjacent to the main gas vent, showing that this method can still be used at some distance from a degassing vent.

  20. Palynofacies as indicators of paleoenvironmental changes in a Cretaceous succession from the Larsen Basin, James Ross Island, Antarctica

    Science.gov (United States)

    Carvalho, Marcelo de A.; Ramos, Renato R. Cabral; Crud, Monika Beatriz; Witovisk, Luciana; Kellner, Alexander W. A.; Silva, Helder de P.; Grillo, Orlando N.; Riff, Douglas; Romano, Pedro S. R.

    2013-09-01

    In order to reconstruct the paleoenvironment of one of the most extensive marine Cretaceous successions in the Southern Hemisphere, palynofacies analyses were conducted on 83 samples from the Whisky Bay (Albian-Turonian), Hidden Lake (Coniacian) and Santa Marta (Santonian-Campanian) formations in the Larsen Basin, James Ross Island, Antarctica. Categories of particulate organic matter were counted and investigated by cluster analysis. The trends and parameters of palynofacies constituents were used to reconstruction paleoenvironments based on the existing sedimentological interpretation. The stratigraphic distribution of the four identified palynofacies associations (A-D) reflects a continuous terrestrial influx throughout the succession. From base to top, a conspicuous increase in woody elements, especially non-opaque particles, is observed. This increase in continental elements occurs despite the presence of marine elements. This finding corroborates the sedimentological interpretation of a deeper water paleoenvironment during deposition of the Whisky Bay Formation and initiation of a shallowing-upward trend in the Hidden Lake Formation, culminating with shallow marine shelf environment of the Santa Marta Formation.

  1. Elemental content of mosses and lichens from Livingston Island (Antarctica) as determined by instrumental neutron activation analysis (INAA).

    Science.gov (United States)

    Culicov, Otilia A; Yurukova, Liliana; Duliu, Octavian G; Zinicovscaia, Inga

    2017-02-01

    The total content of 8 major and 32 trace elements in four species of mosses and two of lichens as well as neighboring soil and rocks collected from different places of the Livingston Island Antarctica was determined by instrumental neutron activation analysis. The main goals of the project consisted of evidencing the possible trace of anthropogenic contamination as well as the influence of altitude on the distribution of considered elements. In the absence of a unanimously accepted descriptor, enrichment factor, geo-accumulation, and pollution load indices with respect to soil and rocks were used. The data, interpreted within the model of a reference plant, were compared with previous studies regarding the same organisms in similar geographic and climatological areas. The experimental results evidenced different capacity of mosses and lichens to retain the considered elements, but within experimental uncertainties, no traces of anthropogenic pollution were found. At the same time, it was found that the content of most of the elements decreased with the altitude.

  2. Potassium alum and aluminum sulfate micro-inclusions in polar ice from Dome Fuji, East Antarctica

    Science.gov (United States)

    Ohno, Hiroshi; Iizuka, Yoshinori; Horikawa, Shinichiro; Sakurai, Toshimitsu; Hondoh, Takeo; Motoyama, Hideaki

    2014-03-01

    Water-soluble trace constituents affect the physicochemical properties of polar ice. Their structural distribution provides important insights into the formation history of ice and inclusions. We report the first finding of KAl(SO4)2·12H2O (potassium alum) and Al2(SO4)3·nH2O (aluminum sulfate) micro-inclusions in the Dome Fuji ice core, East Antartica, using a micro-Raman technique. Eutectic temperatures of these water-soluble species determined using thermal analysis were -0.4 °C for potassium alum and -8.0 °C for aluminum sulfate. Although the formation process of the aluminum-bearing sulfates remains unclear, the occurrence of these salts largely depends on ice depth.

  3. 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

  4. 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

  5. Regional differences in the δO2/N2 records from East Antarctica over the last interglacial

    Science.gov (United States)

    Bazin, L.; Landais, A.; Masson-Delmotte, V.; Kageyama, M.; Paillard, D.; Bopp, L.; Ritz, C.; Leuenberger, M.

    2013-12-01

    Ice cores are the only climate archives offering samples of past atmosphere. The air is trapped at around 100 m under the surface, where the snow is compacted into ice. During this process, multiple influences may modify the air composition as the quantity of insolation received at the surface impacts snow metamorphism and hence air trapping conditions at the basis of the firn (top ~100m of the ice sheet). Analyses of trapped air in ice cores thus give us information on both local and global scales. In this study, we focus on temporal variations of elemental and isotopic composition of oxygen from East Antarctic ice cores. On the one hand, the δ18Oatm, uniformly distributed in the atmosphere, is known to be related to the hydrological cycle and the vegetation cover (Landais et al., 2010), and can be linked to the precession variations. The δO2/N2, on the other hand, appears to be influenced by the local insolation, probably because of modification of the snow structure affecting pore close-off. These two quantities have largely been used as orbital tuning tools for dating purposes in several ice cores from Antarctica (Bender 2002, Suwa et Bender 2008, Kawamura et al., 2007, Dreyfus et al., 2007,Landais et al., 2012, Bazin et al., 2013). Still, gaps in our understanding of the exact mechanisms explaining the δ18Oatm and δO2/N2 variations lead to quite large uncertainties when using these proxies as tie-points for dating purposes. In this study, we use several ice core records in low accumulation rate sites of East Antarctica to decipher global and local effects on the δO2/N2 records. First, we present a compilation of δO2/N2 measurements of the Dome F, Vostok and Dome C ice cores over the last interglacial period. While Dome F and Vostok data were corrected for gas loss during several years of storage at -25°C, new measurements of the air isotopic composition on the Dome C ice core were performed on well-conserved ice (-50°C). Different δO2/N2 mean levels

  6. UAV-based detection and spatial analyses of periglacial landforms on Demay Point (King George Island, South Shetland Islands, Antarctica)

    Science.gov (United States)

    Dąbski, Maciej; Zmarz, Anna; Pabjanek, Piotr; Korczak-Abshire, Małgorzata; Karsznia, Izabela; Chwedorzewska, Katarzyna J.

    2017-08-01

    High-resolution aerial images allow detailed analyses of periglacial landforms, which is of particular importance in light of climate change and resulting changes in active layer thickness. The aim of this study is to show possibilities of using UAV-based photography to perform spatial analysis of periglacial landforms on the Demay Point peninsula, King George Island, and hence to supplement previous geomorphological studies of the South Shetland Islands. Photogrammetric flights were performed using a PW-ZOOM fixed-winged unmanned aircraft vehicle. Digital elevation models (DEM) and maps of slope and contour lines were prepared in ESRI ArcGIS 10.3 with the Spatial Analyst extension, and three-dimensional visualizations in ESRI ArcScene 10.3 software. Careful interpretation of orthophoto and DEM, allowed us to vectorize polygons of landforms, such as (i) solifluction landforms (solifluction sheets, tongues, and lobes); (ii) scarps, taluses, and a protalus rampart; (iii) patterned ground (hummocks, sorted circles, stripes, nets and labyrinths, and nonsorted nets and stripes); (iv) coastal landforms (cliffs and beaches); (v) landslides and mud flows; and (vi) stone fields and bedrock outcrops. We conclude that geomorphological studies based on commonly accessible aerial and satellite images can underestimate the spatial extent of periglacial landforms and result in incomplete inventories. The PW-ZOOM UAV is well suited to gather detailed geomorphological data and can be used in spatial analysis of periglacial landforms in the Western Antarctic Peninsula region.

  7. Abundance and size patterns of echinoderms in coastal soft-bottoms at Deception Island (South Shetland Islands, Antarctica)

    Science.gov (United States)

    Angulo-Preckler, Carlos; Tuya, Fernando; Avila, Conxita

    2017-04-01

    Deception Island is an active volcano in Antarctic waters under high sedimentation regimes, which may affect the abundance and structure of soft-bottom assemblages. During the summer of 2012-2013, a survey of the shallow water soft-bottom assemblages of Deception Island was carried out to examine patterns of abundance and size structure of the three dominant echinoderms (Ophionotus victoriae, Sterechinus neumayeri and Odontaster validus) at 8 locations encompassing a gradient in proximity from the open ocean, including two depths (5 vs. 15 m) per location. Abundance patterns of the three species varied with depth; organisms were typically more abundant at 15 relative to 5 m depth. Our results partially supported the hypothesis that echinoderms from locations adjacent to the open ocean present larger abundances. Body sizes varied significantly among locations and depths for the three species and some places presented a density-size pattern. High sedimentation rates, combined with low ice-related disturbance, may be the reason behind the large abundances of echinoderms found in this waters.

  8. Tide-corrected strain rate and crevasses of Campbell Glacier Tongue in East Antarctica measured by SAR interferometry

    Science.gov (United States)

    Han, H.; Lee, H.

    2016-12-01

    Measurement of flow velocity strain rate of a floating glacier is critical to the investigation of detailed flow regime and crevassing mechanism. We measured the surface deformation of Campbell Glacier Tongue (CGT) in East Antarctica from the 14 COSMO-SkyMed one-day tandem differential interferometric SAR (DInSAR) image pairs obtained in 2011. By removing the vertical tidal deflection obtained from the double-differential InSAR (DDInSAR) signals, we derived the tide-corrected ice-flow velocity and strain rate of CGT. The vertical tidal deflection of CGT was estimated by multiplying the tidal variations corresponding to the DInSAR images by the DDInSAR-derived tide deflection ratio, which was removed from the DInSAR signals to extract ice velocity only. The orientation of crevasses in CGT was nearly perpendicular to the direction of the most tensile strain rate calculated from the tide-corrected ice velocity. This demonstrates that the crevasses form by ice flow in respect of the DInSAR accuracy, not by tidal deflection. The tide correction of DInSAR signals over floating glaciers by using the DDInSAR-derived tide deflection ratio is useful for estimating accurate ice velocity and strain rate for analyzing crevasses. The tide-corrected ice velocity and strain rate will thus be of great value in a better understating of ice dynamics of floating glaciers. This research was funded by National Research Foundation of Korea (NRF-2016R1D1A1A09916630).

  9. 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.

  10. Unusual biogenic calcite structures in two shallow lakes, James Ross Island, Antarctica

    OpenAIRE

    J. Elster; L. Nedbalová; R. Vodrážka; K. Láska; J. Haloda; Komárek, J.

    2015-01-01

    The floors of two shallow endorheic lakes, located on volcanic surfaces on James Ross Island, are covered with calcareous organosedimentary structures. Their biological and chemical composition, lake water characteristics, and seasonal variability of the thermal regime are introduced. The lakes are frozen down to the bottom eight-nine months per year and their water chemistry is characterized by low conductivity and neutral to slightly alkaline pH. The photosynthetic microbi...

  11. Unusual biogenic calcite structures in two shallow lakes, James Ross Island, Antarctica

    OpenAIRE

    J. Elster; L. Nedbalová; R. Vodrážka; K. Láska; J. Haloda; Komárek, J.

    2016-01-01

    The floors of two shallow endorheic lakes, located on volcanic surfaces on James Ross Island, are covered with calcareous organosedimentary structures. Their biological and chemical composition, lake water characteristics, and seasonal variability of the thermal regime are introduced. The lakes are frozen down to the bottom for 8–9 months a year and their water chemistry is characterised by low conductivity and neutral to slightly alkaline pH. The photosynthetic microbial ma...

  12. Eocene age of the Baranowski Glacier Group at Red Hill, King George Island, West Antarctica

    Directory of Open Access Journals (Sweden)

    Mozer Anna

    2015-12-01

    Full Text Available Radiometric and geochemical studies were carried out at Red Hill in the southern part of King George Island (South Shetland Islands, northern Antarctic Peninsula on the Bransfield Strait coast. The rock succession at Red Hill has been determined to represent the Baranowski Glacier Group that was previously assigned a Late Cretaceous age. Two formations were distinguished within this succession: the lower Llano Point Formation and the upper Zamek Formation. These formations have stratotypes defined further to the north on the western coast of Admiralty Bay. On Red Hill the Llano Point Formation consists of terrestrial lavas and pyroclastic breccia; the Zamek Formation consist predominantly of fine to coarse tuff, pyroclastic breccia, lavas, tuffaceous mud-, silt-, and sandstone, locally conglomeratic. The lower part of the Zamek Formation contains plant detritus (Nothofagus, dicotyledonous, thermophilous ferns and numerous coal seams (vitrinitic composition that confirm the abundance of vegetation on stratovolcanic slopes and surrounding lowlands at that time. Selected basic to intermediate igneous rocks from the succession have been analysed for the whole-rock K-Ar age determination. The obtained results indicate that the Red Hill succession was formed in two stages: (1 from about 51–50 Ma; and (2 46–42 Ma, i.e. during the Early to Middle Eocene. This, in combination with other data obtained from other Baranowski Glacier Group exposures on western coast of Admiralty Bay, confirms the recently defined position of the volcano-clastic succession in the stratigraphic scheme of King George Island. The new stratigraphic position and lithofacies development of the Red Hill succession strongly suggest its correlation with other Eocene formations containing fossil plants and coal seams that commonly occur on King George Island.

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

    Directory of Open Access Journals (Sweden)

    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.

  14. A 780-year record of explosive volcanism from DT263 ice core in east Antarctica

    Institute of Scientific and Technical Information of China (English)

    ZHOU Liya; LI Yuansheng; Jihong Cole-da; TAN Dejun; SUN BO; REN Jiawen; WEI Lijia; WANG Henian

    2006-01-01

    Ice cores recovered from polar ice sheet Received and preserved sulfuric acid fallout from explosive volcanic eruptions. DT263 ice core was retrieved from an east Antarctic location. The ice core is dated using a combination of annual layer counting and volcanic time stratigraphic horizon as 780 years (1215-1996 A.D.). The ice core record demonstrates that during the period of approximately 1460-1800 A.D., the accumulation is sharply lower than the levels prior to and after this period. This period coincides with the most recent neoglacial climatic episode, the "Little Ice Age (LIA)", that has been found in numerous Northern Hemisphere proxy and historic records.The non-sea-salt SO2-4 concentrations indicate seventeen volcanic events in DT263 ice core. Compared with those from previous Antarctic ice cores, significant discrepancies are found between these records in relative volcanic flux of several well-known events. The discrepancies among these records may be explained by the differences in surface topography, accumulation rate, snow drift and distribution which highlight the potential impact of local glaciology on ice core volcanic records, analytical techniques used for sulfate measurement, etc. Volcanic eruptions in middle and high southern latitudes affect volcanic records in Antarctic snow more intensively than those in the Iow latitudes.

  15. Validation of satellite altimetry by kinematic GNSS in central East Antarctica

    Science.gov (United States)

    Schröder, Ludwig; Richter, Andreas; Fedorov, Denis V.; Eberlein, Lutz; Brovkov, Evgeny V.; Popov, Sergey V.; Knöfel, Christoph; Horwath, Martin; Dietrich, Reinhard; Matveev, Alexey Y.; Scheinert, Mirko; Lukin, Valery V.

    2017-05-01

    Ice-surface elevation profiles of more than 30 000 km in total length are derived from kinematic GNSS (GPS and the Russian GLONASS) observations on sledge convoy vehicles along traverses between Vostok Station and the East Antarctic coast. These profiles have accuracies between 4 and 9 cm. They are used to validate elevation data sets from both radar and laser satellite altimetry as well as four digital elevation models. A crossover analysis with three different processing versions of Envisat radar altimetry elevation profiles yields a clear preference for the relocation method over the direct method of slope correction and for threshold retrackers over functional fit algorithms. The validation of CryoSat-2 low-resolution mode and SARIn mode data sets documents the progress made from baseline B to C elevation products. ICESat laser altimetry data are demonstrated to be accurate to a few decimetres over a wide range of surface slopes. A crossover adjustment in the region of subglacial Lake Vostok combining ICESat elevation data with our GNSS profiles yields a new set of ICESat laser campaign biases and provides new, independent evidence for the stability of the ice-surface elevation above the lake. The evaluation of the digital elevation models reveals the benefits of combining laser and radar altimetry.

  16. Iron and titanium geochemistry for paleoclimate reconstruction from Talos Dome ice core (East Antarctica)

    Science.gov (United States)

    Maggi, Valter; Marcelli, Augusto; Hampai, Dariush; Cibin, Giannantonio; Delmonte, Barbara; Baccolo, Giovanni

    2015-04-01

    Mineral dust affects the Earth's radiation budget. It can both scatter sunlight back to space (negative radiative forcing) and absorb solar and infrared radiation (positive forcing). Thus, in opposition to the greenhouse gases, the combination of absorption and reflection of solar radiation caused by dust microparticles can lead to a net (longwave and shortwave) negative radiative forcing at the surface and at the top of atmosphere. Transported from the Southern Hemisphere continental landmasses to the remote East Antarctic plateau (long-term transport), mineral dust travels in the high troposphere and interacts with climate. However, processes occurring during atmospheric transport from source areas to polar ice sheets are responsible for the strong reduction of dust concentration and size in the polar atmosphere. Moreover, concentration and grain size, such as mineralogy and shape of dust and aerosols, influencing the dust radiative effect are still poorly known. We present here new Synchrotron radiation spectroscopy data, i.e., X-ray Absorption Near Edge Structure (XANES) at the Fe and Ti K edge from Talos Dome dust samples (72°49'S, 159°110'E; 2315 m a.s.l.) spanning the last two climate cycles (ca. 250 kyrs). The analysis allows the reconstruction of dust geochemistry and Fe and Ti coordination state in selected climatic periods. Dust composition changes in time provide an important contribution to the scientific knowledge on palaeoclimate changes in near coastal regions of the Antarctic ice sheet and novel information on possible changes occurred at the source areas.

  17. 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.

  18. Quantitative ecological risk assessment of inhabitants exposed to polycyclic aromatic hydrocarbons in terrestrial soils of King George Island, Antarctica

    Science.gov (United States)

    Pongpiachan, S.; Hattayanone, M.; Pinyakong, O.; Viyakarn, V.; Chavanich, S. A.; Bo, C.; Khumsup, C.; Kittikoon, I.; Hirunyatrakul, P.

    2017-03-01

    This study aims to conduct a quantitative ecological risk assessment of human exposure to polycyclic aromatic hydrocarbons (PAHs) in terrestrial soils of King George Island, Antarctica. Generally, the average PAH concentrations detected in King George Terrestrial Soils (KGS) were appreciably lower than those of World Marine Sediments (WMS) and World Terrestrial Soils (WTS), highlighting the fact that Antarctica is one of the most pristine continents in the world. The total concentrations of twelve probably carcinogenic PAHs (ΣPAHs: a sum of Phe, An, Fluo, Pyr, B[a]A, Chry, B[b]F, B[k]F, B[a]P, Ind, D[a,h]A and B[g,h,i]P) were 3.21 ± 1.62 ng g-1, 5749 ± 4576 ng g-1, and 257,496 ± 291,268 ng g-1, for KGS, WMS and WTS, respectively. In spite of the fact that KGS has extremely low ΣPAHs in comparison with others, the percentage contribution of Phe is exceedingly high with the value of 50%. By assuming that incidental ingestion and dermal contact are two major exposure pathways responsible for the adverse human health effects, the cancer and non-cancer risks from environmental exposure to PAHs were carefully evaluated based on the ;Role of the Baseline Risk Assessment in Superfund Remedy Selection Decisions; memorandum provided by US-EPA. The logarithms of cancer risk levels of PAH contents in KGS varied from -11.1 to -7.18 with an average of -7.96 ± 7.73, which is 1790 times and 80,176 times lower than that of WMS and WTS, respectively. All cancer risk levels of PAH concentrations observed in KGS are significantly (p < 0.001) lower than those of WMS and WTS. Despite the Comandante Ferraz Antarctic Station fire occurred in February 25th, 2012, both the cancer and non-cancer risks of environmental exposure to PAHs were found in ;acceptable level;.

  19. Soil processes in recently deglaciated environments in Maritime Antarctica: a study case from Elephant Point (Livingston Island, South Shetland Islands)

    Science.gov (United States)

    Oliva, Marc; Ruiz-Fernández, Jesús; Quijano, Laura; Palazón, Leticia; Navas, Ana

    2016-04-01

    Many ice-free environments in the northern Antarctic Peninsula are undergoing rapid and substantial environmental changes in response to reent climate trends. This is the case of Elephant Point (Livingston Island, South Shetland Islands), where the glacier retreat recorded during the second half of the XX century, has exposed 17% of this small peninsula (1.16 km2). Glacier retreat has exposed new ice-free land surface in the northern part of Elephant Point: a moraine extending from the western to the eastern coastlines and a relatively flat proglacial surface. Besides, a sequence of present-day beach, Holocece marine terraces and bedrock plateaus are also distributed in the southern margin of the peninsula. Periglacial processes are widespread in all the peninsula, but the type and characteristics of soils depen on the timing of glacier retreat. In this research we aim to assess how the glacier retreat affects the recently formed soils. Ten sites were sampled along a transect crossing different geomorphological units (beach, raised beaches, moraine, proglacial environment), following the direction of glacier retreat. To this purpose the upper part of selected soil profiles was sectioned in 3 cm depth interval increments to examine main soil properties, grain size distribution, soil organic carbon and pH. Besides, elemental composition and patterns of fallout (FRNs) and environmental radionuclides (ERNs) were analysed to assess if soil profile characteristics within the active layer are affected by glacier retreat. The results obtained confirm the potential for using geomorphological, edaphic and geochemical data to derive information for assessing the influence of different stages of glacier retreat in the study soils.

  20. CEDEX research activities in Antarctica. Aquatic ecosystems in Byers Peninsula (Livingston Island, maritime Antarctica); Actividad investigadora del CEDEX en la Antartida. Ecosistemas acuaticos de la Peninsula Byers (Isla Livingston, Antartida)

    Energy Technology Data Exchange (ETDEWEB)

    Toro, M.; Quesada, A.; Camacho, A.; Oliva, M.; Alcami, A.; Antoniades, D.; Banon, M.; Fassnacht, S.; Fernandez-Valiente, E.; Galan, L.; Giralt, S.; Granados, I.; Justel, A.; Liu, E. J.; Lopez-Bravo, A.; Martinez-Cortizas, A.; Pla-Rabes, S.; Rastrojo, A.; Rico, E.; Rochera, C.; Van de Vijver, B.; Velazquez, D.; Villaescusa, J. A.; Vicent, W. F.

    2015-07-01

    Since 2001 CEDEX has taken part in many Antarctic joint research projects with different institutions from Spain and other countries, developing scientific activities in the International Camp of Byers Peninsular (Livingston Island, South Shetland Islands, Antarctica). This place was designed as an Antarctic Specially Protected Area (No.126) because the importance and value of its terrestrial and aquatic habitats. It is one of the largest ice-free areas of maritime Antarctica, with the highest diversity of environments and geological, hydrological and biological processes in the whole region, all of them in a pristine state. Byers Peninsula is considered the most significant limnological area in the Antarctic Peninsula region because it hosts a high number of lakes, ponds and streams, with an exceptional fauna and flora diversity, including the most singular, representative or endemic Antarctic species. Furthermore, the lakes sedimentary record is one of the widest and complete archives in Antarctic Peninsula region for the palaeocological and climatic study of the Holocene. Because Byers Peninsula is an Antarctic biodiversity hotspot, and it is located in one of the areas in the Earth where global warming is being more significant, it must be considered as a suitable international reference site for limnetic, terrestrial and coastal studies, and long term monitoring programmes. (Author)

  1. Distribution of subglacial sediments across the Wilkes Subglacial Basin, East Antarctica

    Science.gov (United States)

    Frederick, Bruce C.; Young, Duncan A.; Blankenship, Donald D.; Richter, Thomas G.; Kempf, Scott D.; Ferraccioli, Fausto; Siegert, Martin J.

    2016-04-01

    Topography, sediment distribution, and heat flux are all key boundary conditions governing the dynamics of the East Antarctic Ice Sheet (EAIS). EAIS stability is most at risk in Wilkes Land across vast expanses of marine-based catchments including the 1400 km × 600 km expanse of the Wilkes Subglacial Basin (WSB) region. Data from a recent regional aerogeophysical survey (Investigating the Cryospheric Evolution of the Central Antarctic Plate (ICECAP)/IceBridge) are combined with two historical surveys (Wilkes basin/Transantarctic Mountains System Exploration-Ice-house Earth: Stability or DYNamism? (WISE-ISODYN) and Wilkes Land Transect (WLK)) to improve our understanding of the vast subglacial sedimentary basins impacting WSB ice flow and geomorphology across geologic time. Analyzing a combination of gravity, magnetic and ice-penetrating radar data, we present the first detailed subglacial sedimentary basin model for the WSB that defines distinct northern and southern subbasin isopachs with average sedimentary basin thicknesses of 1144 m ± 179 m and 1623 m ± 254 m, respectively. Notably, more substantial southern subbasin sedimentary deposition in the WSB interior supports a regional Wilkes Land hypothesis that basin-scale ice flow and associated glacial erosion is dictated by tectonic basement structure and the inherited geomorphology of preglacial fluvial networks. Orbital, temperate/polythermal glacial cycles emanating from adjacent alpine highlands during the early Miocene to late Oligocene likely preserved critical paleoclimatic data in subglacial sedimentary strata. Substantially thinner northern WSB subglacial sedimentary deposits are generally restricted to fault-controlled, channelized basins leading to prominent outlet glacier catchments suggesting a more dynamic EAIS during the Pliocene.

  2. Talos Dome ice Core (East Antarctica) Mieral Dust Iron Geochemistry of the Last 160 ky.

    Science.gov (United States)

    Maggi, V.; Augusto, M.; Dariush, H.; Giannantonio, C.; Delmonte, B.; Baccolo, G.

    2015-12-01

    Earth's radiation budget is affected by the mineral dust blowing up from arid and semi-arid sources areas. It can act as negative radiative forcing (mainly by sunlight backscattering out to the space) and positive forcing (as absorbing solar and infrared radiation). The combination of absorption and reflection of solar radiation caused by dust microparticles can lead to a net (longwave and shortwave) negative radiative forcing at the surface and at the top of atmosphere, in opposition to the greenhouse gases.Transported from the Southern Hemisphere continental landmasses to the remote East Antarctic plateau (long-term transport), mineral dust travels in the high troposphere and interacts with climate. However, processes occurring during atmospheric transport from source areas to polar ice sheets are responsible for the strong reduction of dust concentration and size in the polar atmosphere. Moreover, concentration and grain size, such as mineralogy and shape of dust and aerosols, influencing the dust radiative effect are still poorly known.We present here new Synchrotron radiation spectroscopy data, i.e., X-ray Absorption Near Edge Structure (XANES) at the Fe and Ti K edge from Talos Dome dust samples (72°49'S, 159°110'E; 2315 m a.s.l.) spanning the last two climate cycles (ca. 250 kyrs). The analysis allows the reconstruction of dust geochemistry and Fe and Ti coordination state in selected climatic periods. Dust composition changes in time provide an important contribution to the scientific knowledge on palaeoclimate changes in near coastal regions of the Antarctic ice sheet and novel information on possible changes occurred at the source areas.

  3. Preliminary study on the spore-pollen assemblages found in the Cenozoic sedimentary rocks in Grove Mountains, east Antarctica and its climatic implications

    Institute of Scientific and Technical Information of China (English)

    Fang Aimin; Liu Xiaohan; Wang Weiming; Li Xiaoli; Yu Liangjun; Huang Feixin

    2005-01-01

    Glaciogene sedimentary rocks have been found in modem tills of the Grove Mountains, east Antarctica during the 1998 - 1999 Chinese National Antarctic Research Expedition (CHNARE). Based on the lithilogic and sedimentary features,these sedimentary rocks are correlated with Cenozoic sedimentary strata of the Pagodroma Group in the neighboring Prince Charles Mountains and the Sorsdal Formation in VestFold Hills. Sedimentary clasts contain sparsely Late Tertiary spores and pollens, including: Toroisporis (Lygodiaceae), Osmunda , Granulatisporites (Pteridaceae?), Polypodiaceae, Podocarpus, Araucariaceae, Artemisia, Rhus, Nothofagidites,Proteacidites ( Proteaceae ) , Quercus , Fraxinoipollenites (Oleaceae) , Oleoidearumpollenites(Oleaceae), Operculumpollis, and Tricolpopollenites. Most of the pollen and spores contained in these samples originate from local sources according to the conditions of their preservations as well as correlations with the microfossil assemblages found in the neighboring areas. The majority of the pollen assemblages, as represented by Podocarpus and Nothofagus, belong to the Weddellian biogeocenose, however some exotic components from the old sedimentary basement rocks may have been included during erosion of the proximal ice sheet. If the source areas of glaciogenic sedimentary rocks that bear the pollen and spores are assumed to be local, or in the up glacier areas, the pollen assemblages in these samples might represent an inland flora during a warmer period of the ice-sheet evolutionary history. The finding of the Artemisia and Chenopodiaceae in the pollen assemblages implies that they may belong to late Tertiary (most probably Pliocene). The absence of diatoms in the samples analyzed may indicate that there are no Cenozoic marine strata in the interior of the east Antarctica beyond the Grove Mountains. The significances of the finding of the Nothofagus in these pollen assemblages are discussed on the basis of current knowledge about the age

  4. Aerobic endospore-forming bacteria from geothermal environments in northern Victoria Land, Antarctica, and Candlemas Island, South Sandwich archipelago, with the proposal of Bacillus fumarioli sp. nov.

    Science.gov (United States)

    Logan, N A; Lebbe, L; Hoste, B; Goris, J; Forsyth, G; Heyndrickx, M; Murray, B L; Syme, N; Wynn-Williams, D D; De Vos, P

    2000-09-01

    Aerobic endospore-forming bacteria were isolated from soils taken from active fumaroles on Mount Rittmann and Mount Melbourne in northern Victoria Land, Antarctica, and from active and inactive fumaroles on Candlemas Island, South Sandwich archipelago. The Mt Rittmann and Mt Melbourne soils yielded a dominant, moderately thermophilic and acidophilic, aerobic endospore-former growing at pH 5.5 and 50 degrees C, and further strains of the same organism were isolated from a cold, dead fumarole at Clinker Gulch, Candlemas Island. Amplified rDNA restriction analysis, SDS-PAGE and routine phenotypic tests show that the Candlemas Island isolates are not distinguishable from the Mt Rittmann strains, although the two sites are 5600 km apart, and 16S rDNA sequence comparisons and DNA relatedness data support the proposal of a new species, Bacillus fumarioli, the type strain of which is LMG 17489T.

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

    Science.gov (United States)

    Legrand, Michel; Preunkert, Susanne; Savarino, Joël; Frey, Markus M.; Kukui, Alexandre; Helmig, Detlev; Jourdain, Bruno; Jones, Anna E.; Weller, Rolf; Brough, Neil; Gallée, Hubert

    2016-07-01

    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 the katabatic flow

  6. Measurements of OH and RO2 radicals at Dome C, East Antarctica

    Directory of Open Access Journals (Sweden)

    A. Kukui

    2014-06-01

    Full Text Available Concentrations of OH radicals and the sum of peroxy radicals, RO2, were measured in the boundary layer for the first time on the East Antarctic Plateau at the Concordia Station (Dome C, 75.10° S, 123.31° E during the austral summer 2011/2012. The median concentrations of OH and RO2 radicals were 3.1 × 106 molecule cm−3 and 9.9 × 107 molecule cm−3, respectively. These values are comparable to those observed at the South Pole, confirming that the elevated oxidative capacity of the Antarctic atmospheric boundary layer found at the South Pole is not restricted to the South Pole but common over the high Antarctic plateau. At Concordia, the concentration of radicals showed distinct diurnal profiles with the median maximum of 5.2 × 106 molecule cm−3 at 11:00 and the median minimum of 1.1 × 106 molecule cm−3 at 01:00 for OH radicals and 1.7 × 108 molecule cm−3 and 2.5 × 107 molecule cm−3 for RO2 radicals at 13:00 and 23:00, respectively (all times are local times. Concurrent measurements of O3, HONO, NO, NO2, HCHO and H2O2 demonstrated that the major primary source of OH and RO2 radicals at Dome C was the photolysis of HONO, HCHO and H2O2, with the photolysis of HONO contributing ∼75% of total primary radical production. However, photochemical modelling with accounting for all these radical sources overestimates the concentrations of OH and RO2 radicals by a factor of 2 compared to field observations. Neglecting the OH production from HONO in the photochemical modelling results in an underestimation of the concentrations of OH and RO2 radicals by a factor of 2. To explain the observations of radicals in this case an additional source of OH equivalent to about 25% of measured photolysis of HONO is required. Even with a factor of 4 reduction in the concentrations of HONO, the photolysis of HONO represents the major primary radical source at Dome C. Another major factor leading to the large concentration of OH radicals measured at

  7. Ice crystal c-axis orientation and mean grain size measurements from the Dome Summit South ice core, Law Dome, East Antarctica

    Science.gov (United States)

    Treverrow, Adam; Jun, Li; Jacka, Tim H.

    2016-06-01

    We present measurements of crystal c-axis orientations and mean grain area from the Dome Summit South (DSS) ice core drilled on Law Dome, East Antarctica. All measurements were made on location at the borehole site during drilling operations. The data are from 185 individual thin sections obtained between a depth of 117 m below the surface and the bottom of the DSS core at a depth of 1196 m. The median number of c-axis orientations recorded in each thin section was 100, with values ranging from 5 through to 111 orientations. The data from all 185 thin sections are provided in a single comma-separated value (csv) formatted file which contains the c-axis orientations in polar coordinates, depth information for each core section from which the data were obtained, the mean grain area calculated for each thin section and other data related to the drilling site. The data set is also available as a MATLAB™ structure array. Additionally, the c-axis orientation data from each of the 185 thin sections are summarized graphically in figures containing a Schmidt diagram, histogram of c-axis colatitudes and rose plot of c-axis azimuths. All these data are referenced by doi:10.4225/15/5669050CC1B3B and are available free of charge at https://data.antarctica.gov.au" target="_blank">https://data.antarctica.gov.au.<

  8. Causes of dust size variability in central East Antarctica (Dome B): Atmospheric transport from expanded South American sources during Marine Isotope Stage 2

    Science.gov (United States)

    Delmonte, Barbara; Paleari, Chiara Ileana; Andò, Sergio; Garzanti, Eduardo; Andersson, Per Sune; Petit, Jean Robert; Crosta, Xavier; Narcisi, Biancamaria; Baroni, Carlo; Salvatore, Maria Cristina; Baccolo, Giovanni; Maggi, Valter

    2017-07-01

    We here investigate the spatial and temporal variability of eolian dust particle sorting recorded in the Dome B (77° 05‧ S, 94° 55' E) ice core, central East Antarctica, during Marine Isotope Stage (MIS) 2. We address the question whether such changes reflect variable transport pathways from a unique source area or rather a variable apportionment from diverse Southern Hemisphere sources transported at different elevation in the troposphere. The Sr-Nd radiogenic isotope composition of glacial dust samples as well as single-particle Raman mineralogy support the hypothesis of a single dust provenance both for coarse and fine mode dust events at Dome B. The southern South American provenance of glacial dust in Antarctica deduced from these results indicate a dust composition coherent with a mixture of volcanic material and minerals derived from metamorphic and plutonic rocks. Additionally, Dome B glacial samples contain aragonite particles along with diatom valves of marine benthic/epiphytic species and freshwater species living today in the northern Antarctic Peninsula and southern South America. These data suggest contribution from the exposed Patagonian continental shelf and glacial outwash plains of southern Patagonia at the time when sea level reached its minimum. Our results confirm that dust sorting is controlled by the relative intensity of the two main patterns of tropospheric dust transport onto the inner Plateau, i.e. fast low-level advection and long-range high-altitude transport including air subsidence over Antarctica.

  9. Recent evolution of the overall radioactive levels in the ice of Livingston Island (Antarctica)

    Energy Technology Data Exchange (ETDEWEB)

    Baeza, A.; Del Rio, L.M.; Jimenez, A.; Miro, C.; Paniagua, J.M. [Universidad de Extremadura, Caceres (Spain). Departamento de Fisica; Navarro, E. [IFIC, Facutad de Fisicas, Valencia (Spain)

    1996-08-01

    A study was carried out of the physico-chemical characteristics of the different layers of ice to a depth of 8.32 m in the Hurd glacier on Livingston Island in the South Shetland archipelago (Antartica). No dependence on depth was observed for the pH, dry residue, or the concentrations of Ca{sup 2+}, Mg{sup 2+}, and K{sup +} ions. The only dependence observed was a systematic increase in density from 05 to 0.85 g cm{sup -3} due to the greater compaction of the deeper layers. The mean annual mass balance was determined by two methods; localization of the ashes emitted by a volcano on Deception Island and by means of a {sup 210}Pb dating method. The result in both cases was a value of 0.24 kg m{sup -2} kg m{sup -2} yr{sup -1}, which allowed us to date different layers of ice sampled. The mean annual {sup 210}Pb fallout was determined to be 1.9 Bq m{sup -2} yr{sup -1}. While no systematic variations in total {beta} activity were observed with depth, they were observed for total {alpha} and residual {beta} activities in the said ice layers. (Author).

  10. Deliberations on Microbial Life in the Subglacial Lake Vostok, East Antarctica

    Science.gov (United States)

    Bulat, S.; Alekhina, I.; Lipenkov, V.; Lukin, V.; Marie, D.; Petit, J.

    2004-12-01

    The objective was to estimate microbial contents of accretion (lake originating) ice from the Lake Vostok buried beneath 4-km thick East Antarctic ice sheet with the ultimate goal to discover microbial life in this extreme icy environment featured by no light, close to freezing point temperature, ultra-low DOC contents, and an excess of oxygen. The PCR based bacterial and archaeal 16S ribosomal RNA gene sequencing constrained by Forensic Biology and Ancient DNA research criteria was used as a main approach. Epifluorescent and confocal microscopies as well as flow cytometry were implemented. DNA study showed that the accretion ice is essentially bacteria- and archaea-free. Up to now, the only accretion ice type 1 featured by mica-clay sediments presence and namely one horizon of four studied (3607m) allowed the recovery a few bacterial phylotypes. This unexpectedly included the chemolithoautotrophic thermophile Hydrogenophilus thermoluteolus and two more unclassified phylotypes all passing numerous contaminant controls. In contrast, the deeper and cleaner accretion ice 2 (three cores) with no sediments presence and near detection limit gas contents gave no reliable signals. The microbes detected in accretion ice 1 are unbelievable to resist an excess of oxygen in the lake water body (700 - 1300 mg O2/l). They are supposed to be thriving in rather warm anoxic sediments in deep faults at the lake bottom and sporadically flushing out along with sediments to the lake veins in a shallow depth bay due to a seismotectonic activity likely operating in the lake environment. A few geophysical and geological evidences support this scenario. In the bay the presence of mica-clay sediments, higher accretion rate due to relief rise and likely oxygen-depleted upper layer of water can provide microbes with a chance to escape the high oxygen tension by the rapid entrapment into accretion ice 1. Sediment-free accretion ice 2, which forms above a deeper part of the lake, shows no

  11. Morphostructural analysis and Cenozoic evolution of Elephant Island, Southern Scotia Arc, Antarctica

    Science.gov (United States)

    Mink, S.; Maestro, A.; López-Martínez, J.; Schmid, T.; Galindo-Zaldívar, J.; Trouw, R. A. J.

    2015-04-01

    Elephant Island, located in the vicinity of the present-day active boundary of the South Shetland Block and the Antarctic and Scotia plates, is a region of particular interest for understanding the past and present geodynamic evolution of the southern Scotia Arc. Lineament from different data sources, field-measured fractures and geomorphological evidences have been analysed in this context. The lineaments extracted from aerial photographs (1,624), from a DEM (348) and from RADARSAT-2 satellite data (1,365) indicate four dominant lineament sets with NE-SW, NW-SE, N-S and W-E strikes. All data sources identified similar lineament families, but differences in the frequency distributions and subsequently on the dominant orientations were observed. The measurements direct of fractures were obtained from 23 sites in the field at which 278 planes were measured. Fracture planes indicate main modes trending in the NNE-SSW and NNW-SSE directions and a secondary mode in the E-W. The major trends of the fracture measurements and the lineaments display a good correlation in the E-W direction. However, there is an angular variation in the azimuth values of the NNE-SSE and NNW-SSE fractures with respect to the N-S, NE-SW and NW-SE orientations of the lineaments of approximately 20°. This trend deviation may be due to the fact that mapped lineaments are composed of small fracture sets that may be related to shear fractures that cannot be distinguished at the aerial photograph or radar satellite data scales. Submerged sea-floor morphological feature orientations match the studied morphostructures on the island and the main tectonic structures in this part of the Scotia Arc. A linkage of the main lineament families to the tectonic stages from the Oligocene to the present has been proposed, taking into account the information of the orientation and sense of movement of the fractures and stresses in the Elephant Island region.

  12. Strontium isotopic geochemistry of the volcanic rocks and associated megacrysts and inclusions from Ross Island and vicinity, Antarctica

    Science.gov (United States)

    Stuckless, J.S.; Ericksen, R.L.

    1976-01-01

    Twelve whole-rock samples of volcanic rocks and a composite of 11 basanitoid samples from Ross Island and vicinity, Antarctica show a narrow range of 87Sr/86Sr ratios from 0.70305 to 0.70339. This range is consistent with a model of differentiation from a single parent magma, but the data allow a 30% variation in the 87Rb/86Sr ratio in the source region if the average ratio is less than 0.057 and if the source region has existed as a closed system for 1.5 b.y. Megacrysts of titaniferous augite, kaersutite, and anorthoclase are isotopically indistinguishable from the host volcanic rocks and therefore are probably cogenetic with the volcanic sequence. A single trachyte sample is isotopically distinct from the rest of the volcanic rocks and probably was contaminated with crustal strontium. Ultramafic and mafic nodules found in association with basanitoids and trachybasalts have 87Sr/86Sr ratios ranging from 0.70275 to 0.70575. Several of these nodules exhibit evidence of reaction with the melt and are isotopically indistinguishable from their hosts, but data for seven granulite-facies nodules show an apparent isochronal relationship. Although this isochron may be fortuitous, the resulting age of 158??22 m.y. is similar to ages reported for the voluminous Ferrar Dolerites, and suggests isotopic re-equilibration within the lower crust and upper mantle. These nodules are not genetically related to the Ferrar Dolerites, as evidenced by their lower initial 87Sr/86Sr ratios. Three ultramafic nodules are texturally and isotopically distinct from the rest of the analyzed nodules. These are friable, have larger 87Sr/86Sr ratios, and may represent a deeper sampling of mantle rock than the granulite-facies nodules. They were, however, derived at a shallower depth than the alkalic magma. Thus they are not genetically related to either the magma or the granulite-facies nodules. ?? 1976 Springer-Verlag.

  13. Life between tides: Spatial and temporal variations of an intertidal macroalgal community at Potter Peninsula, South Shetland Islands, Antarctica

    Science.gov (United States)

    Marcías, María Laura; Deregibus, Dolores; Saravia, Leonardo Ariel; Campana, Gabriela Laura; Quartino, María Liliana

    2017-03-01

    Intertidal zones are one of the most studied habitats in the world. However, in Antarctica, further studies are needed for a more complete understanding of these systems. When conspicuous Antarctic intertidal communities occur, macroalgae are a key component. Given that intertidal communities have a fast response to variations in environmental conditions and could reflect climate fluctuations, we conducted a non-destructive study with photographic transects in an intertidal zone at Potter Peninsula, Isla 25 de Mayo/King George Island, over four years and during five months of the warm season. We tested the general hypothesis that macroalgal intertidal communities are mainly structured by the vertical stress gradient and that changes in temperature between seasons and between years have a great influence in the macroalgal community structure. Spatial, seasonal and inter-annual variations were studied using GLM, quantile regression and NMDS ordinations. The vertical stress gradient was the main factor that explained macroalgal cover. The Low and the Middle level shared similarities, but the latter was more variable. The High level had the lowest cover, richness and diversity. The dominant species here was the endemic red alga Pyropia endiviifolia, which is strongly adapted to extreme conditions. At the Middle level, there was a significant increase in macroalgal cover during spring months, and it stabilized in summer. Inter-annual variations showed that there is a strong variation in the total macroalgal cover and community structure over the studied years. Environmental conditions have a significant effect in shaping the studied intertidal community, which is very sensitive to climate oscillations. An increase in temperature produced a decrease of annual ice foot cover, number of snow days and - as a result - an increase in macroalgal cover. In a global climate-change scenario, a shift in species composition could also occur. Species with wide physiological

  14. The Holocene deglaciation of the Byers Peninsula (Livingston Island, Antarctica) based on the dating of lake sedimentary records

    Science.gov (United States)

    Oliva, M.; Antoniades, D.; Giralt, S.; Granados, I.; Pla-Rabes, S.; Toro, M.; Liu, E. J.; Sanjurjo, J.; Vieira, G.

    2016-05-01

    The process of deglaciation in the Antarctic Peninsula region has large implications for the geomorphological and ecological dynamics of the ice-free environments. However, uncertainties still remain regarding the age of deglaciation in many coastal environments, as is the case in the South Shetland Islands. This study focuses on the Byers Peninsula, the largest ice-free area in this archipelago and the one with greatest biodiversity in Antarctica. A complete lacustrine sedimentary sequence was collected from five lakes distributed along a transect from the western coast to the Rotch Dome glacier front: Limnopolar, Chester, Escondido, Cerro Negro and Domo lakes. A multiple dating approach based on 14C, thermoluminescence and tephrochronology was applied to the cores in order to infer the Holocene environmental history and identify the deglaciation chronology in the Byers Peninsula. The onset of the deglaciation started during the Early Holocene in the western fringe of the Byers Peninsula according to the basal dating of Limnopolar Lake (ca. 8.3 cal. ky BP). Glacial retreat gradually exposed the highest parts of the Cerro Negro nunatak in the SE corner of Byers, where Cerro Negro Lake is located; this lake was glacier-free since at least 7.5 ky. During the Mid-Holocene the retreat of the Rotch Dome glacier cleared the central part of the Byers plateau of ice, and Escondido and Chester lakes formed at 6 cal. ky BP and 5.9 ky, respectively. The dating of the basal sediments of Domo Lake suggests that the deglaciation of the current ice-free easternmost part of the Byers Peninsula occurred before 1.8 cal. ky BP.

  15. Per- and polyfluoroalkyl substances in snow, lake, surface runoff water and coastal seawater in Fildes Peninsula, King George Island, Antarctica.

    Science.gov (United States)

    Cai, Minghong; Yang, Haizhen; Xie, Zhiyong; Zhao, Zhen; Wang, Feng; Lu, Zhibo; Sturm, Renate; Ebinghaus, Ralf

    2012-03-30

    The multi-matrices samples from snow (n=4), lake water (n=4), surface runoff water (SRW) (n=1) and coastal seawater (n=10) were collected to investigate the spatial distribution and the composition profiles of per- and polyfluoroalkyl substances (PFASs) in Fildes Peninsula, King George Island, Antarctica in 2011. All samples were prepared by solid-phase extraction and analyzed by using high performance liquid chromatography/negative electrospray ionization-tandem mass spectrometry (HPLC/(-)ESI-MS/MS). 14 PFASs in snow, 12 PFASs in lake water, 9 PFASs in SRW and 13 PFASs in coastal seawater were quantified, including C(4), C(7), C(8), C(10) PFSAs, C(4)-C(9), C(11)-C(14), C(16) PFCAs, and FOSA. PFOA was detected in all samples with the highest concentration (15,096 pg/L) in coastal seawater indicating a possible influence of local sewage effluent. High concentration and mostly frequency of PFBA occurred in snow (up to 1112 pg/L), lake water (up to 2670 pg/L) and SRW (1431 pg/L) while detected in the range of method detection limited (MDL) in the coastal seawaters indicate that PFBA is mainly originated from atmospheric dust contamination and also affected by the degradation of their precursors. No geographical differences in PFOS concentrations (n=8, 18 ± 3 pg/L) were measured in all snow and lake water samples also suggests that PFOS could be originated from the degradation of their precursors which can transported by long-range atmospheric route, but in a very low level.

  16. Modern sedimentation in a rapidly warming fjord: Potter Cove, King George Island, Antarctica

    Science.gov (United States)

    Hass, H. C.; Kuhn, G.; Wittenberg, N.; Wölfl, A.

    2012-04-01

    The northern Antarctic Peninsula belongs to the fastest warming regions on earth. The winter-warming trend was strong and stable over the past 70 years. As a result, Potter Cove, a small fjord that opens into Maxwell Bay (King George Island, South Shetland Islands), shows significant environmental change. A former tidewater glacier (Fourcade Glacier) has retreated onto land exposing bedrock such as a small island close to the glacier front. It is suggested that the warming trend triggered excessive discharge of sediment-laden meltwaters in the form of turbid surface waters. The hypothesis for this study is that very fine-grained materials are present in Potter Cove and that meltwater plumes that exit Potter Cove can be traced downstream in the form of fans of fine-grained materials. In this study we investigate the modern sedimentation patterns in Potter Cove using hydroacoustics and seafloor samples to compare that with conditions from the past as recorded in sediment cores. Surface grain-size distributions reveal a distinct textural pattern in Potter Cove. Cluster analysis suggests 7 classes of sediment types. Four of them are unimodal, three classes show fine-skewed distributions with tendencies to bimodality. The finer sediment classes are found in the central inner part of the cove. The finest class (mode at 16 µm) forms only a small patch in the shelter of a small island. Sediments from close to the glacier front appear to be slightly depleted in fine-grained materials. From the glacier front to the outer fjord the sediments show influence of current sorting, i.e. the coarser mode becomes more significant and sorting increases. A sediment core from the deeper outer basin of Potter Cove reveals only one of the better-sorted, coarser classes that appears to form on the way from the glacier into the basin. There are 5 long sediment cores located less than 10 km off the mouth of Potter Cove in Maxwell Bay. All of which reveal sediments that belong either to the

  17. A 2,000-year record of mercury and ancient civilizations in seal hairs from King George Island, West Antarctica.

    Science.gov (United States)

    Sun, Liguang; Yin, Xuebin; Liu, Xiaodong; Zhu, Renbin; Xie, Zhouqing; Wang, Yuhong

    2006-09-01

    The concentrations of total mercury (Hg(T)) and three bio-essential elements (phosphor, potassium, sodium) were analyzed in Antarctic seal hairs from a lake core spanning the past 2,000 years and collected from King George Island (63 degrees 23'S, 57 degrees 00'W), West Antarctica. The Hg(T) concentration shows a significant fluctuation while the levels of the three bio-essential elements remain almost constant. The rise and fall of the Hg(T) concentration in the seal hairs are found to be closely coincided with ancient activities of gold and silver mining using Hg-amalgamation process around the world, especially in the Southern Hemisphere. Briefly, Hg(T) levels are high during five episodes of extensive gold and silver mining activities--Rome Empire and China Han Dynasty (approximately 18-300 A.D.), Maya period and China Tang (750-900 A.D.), Incas civilization and Christian Kingdom (1200-1500 A.D.), New world (1650-1800 A.D.), and modern industry period (1840 A.D.-present); they are low during four time periods of reduced gold and silver mining activities--the China Han and Rome fall (since 300 A.D.), Maya fall and Wartime period in China (1050-1250 A.D.), Pizarro coming (ca. 1532 A.D.) and Independence War of South America (1800-1830 A.D.). Two profiles of Hg(T) in other two lake cores, one affected by seal excrements and the other by penguin droppings, from the same region are similar to the one in seal hairs. The Hg concentration profile in the seal hairs is significantly correlated with the one in a peat bog of Southern Chile near King George Island. Since Hg is existent mainly at the form of methyl-mercury in seal hairs, this correlation supports a relationship and link between atmospheric mercury concentration and methyl-mercury production. Comparing with samples from American and European continents, the Antarctic seal hairs provide an archive of total mercury concentration in surface seawater of the South Ocean less affected by regional human activities

  18. Chevkinite-group minerals from granulite-facies metamorphic rocks and associated pegmatites of East Antarctica and South India

    Science.gov (United States)

    Belkin, H.E.; Macdonald, R.; Grew, E.S.

    2009-01-01

    Electron microprobe data are presented for chevkinite-group minerals from granulite-facies rocks and associated pegmatites of the Napier Complex and Mawson Station charnockite in East Antarctica and from the Eastern Ghats, South India. Their compositions conform to the general formula for this group, viz. A4BC2D2Si4O22 where, in the analysed specimens A = (rare-earth elements (REE), Ca, Y, Th), B = Fe2+, Mg, C = (Al, Mg, Ti, Fe2+, Fe3+, Zr) and D = Ti and plot within the perrierite field of the total Fe (as FeO) (wt.%) vs. CaO (wt.%) discriminator diagram of Macdonald and Belkin (2002). In contrast to most chevkinite-group minerals, the A site shows unusual enrichment in the MREE and HREE relative to the LREE and Ca. In one sample from the Napier Complex, Y is the dominant cation among the total REE + Y in the A site, the first reported case of Y-dominance in the chevkinite group. The minerals include the most Al-rich yet reported in the chevkinite group (49.15 wt.% Al2O3), sufficient to fill the C site in two samples. Conversely, the amount of Ti in these samples does not fill the D site, and, thus, some of the Al could be making up the deficiency at D, a situation not previously reported in the chevkinite group. Fe abundances are low, requiring Mg to occupy up to 45% of the B site. The chevkinite-group minerals analysed originated from three distinct parageneses: (1) pegmatites containing hornblende and orthopyroxene or garnet; (2) orthopyroxene-bearing gneiss and granulite; (3) highly aluminous paragneisses in which the associated minerals are relatively magnesian or aluminous. Chevkinite-group minerals from the first two parageneses have relatively high FeO content and low MgO and Al2O3 contents; their compositions plot in the field for mafic and intermediate igneous rocks. In contrast, chevkinite-group minerals from the third paragenesis are notably more aluminous and have greater Mg/Fe ratios. ?? 2009 The Mineralogical Society.

  19. Fluid components in accessory minerals of Pan-African granitoids in the S(o)r Rondane Mountains, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    LI Zi-long; CHEN Han-lin; YANG Shu-feng; TAINOSHO Yoshiaki; SHIRAISHI Kazuyuki; OWADA Masaaki

    2007-01-01

    Fluids (fluorine, chlorine, and OH) in accessory minerals (apatite, titanite and allanite) of Pan-African granitoids(Group-Ⅰ granitoids, Group-Ⅱ granitoids and Mefjell Plutonic Complex) from the Sor Rondane Mountains, East Antarctica were precisely measured by an electronic microprobe analyzer in this study. Apatites in the granites have commonly high fluorine contents. However, fluorine contents from the Group-Ⅰ, Group-Ⅱ granitoids and Mefjell Plutonic Complex (MPC) are of important variation, which F contents (3.21~7.20 wt%) in apatite from the Group-Ⅱ granitoids are much higher than those from the Group-Ⅰ granitoids (1.22~3.60 wt%) and the MPC (3.21~4.11 wt%). Titanite in the MPC has a low fluorine content (0.23~0.50 wt%), being less than those in the Group-Ⅰ granitoids (2.28 wt%) and Group-Ⅱ granitoids (1.85~2.78 wt%). Fluorine in allanite in the Group-Ⅱ granitoids seems to have much lower contents than those from the Group-Ⅰ granitoids and the MPC. Higher fluorine contents in the titanite from the Group-Ⅱ granitoids may be mainly controlled by late-magmatic fluid-rock interaction processes associated with melt, but may not be indicative of original magma contents based on its petrographic feature. Due to very lower chlorine contents from all of accessory minerals, the authors suggest that titanite and apatite with higher fluorine contents in the Group-Ⅱ granitoids have much lower H2O (OH) contents compared with those in the Group-Ⅰ granitoids according to the partition among (F, Cl, OH).Fluorine contents in whole-rock samples show a variation from the higher in the Group-Ⅰ granitoids to the lower in the Group-Ⅱ granitoids and the MPC, which are consistent with the changes of those from the biotite and hornblende as well as fluorite occurred in the Group-Ⅰ granitoids reported previously. Based on the above study of fluorine in accessory minerals and combined with the previous fluorine contents from biotites and

  20. 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.

  1. Holocene ice dynamics and bottom-water formation associated with Cape Darnley polynya activity recorded in Burton Basin, East Antarctica

    Science.gov (United States)

    Borchers, Andreas; Dietze, Elisabeth; Kuhn, Gerhard; Esper, Oliver; Voigt, Ines; Hartmann, Kai; Diekmann, Bernhard

    2016-03-01

    A multi-proxy study including sedimentological, mineralogical, biogeochemical and micropaleontological methods was conducted on sediment core PS69/849-2 retrieved from Burton Basin, MacRobertson Shelf, East Antarctica. The goal of this study was to depict the deglacial and Holocene environmental history of the MacRobertson Land-Prydz Bay region. A special focus was put on the timing of ice-sheet retreat and the variability of bottom-water formation due to sea ice formation through the Holocene. Results from site PS69/849-2 provide the first paleo-environmental record of Holocene variations in bottom-water production probably associated to the Cape Darnley polynya, which is the second largest polynya in the Antarctic. Methods included end-member modeling of laser-derived high-resolution grain size data to reconstruct the depositional regimes and bottom-water activity. The provenance of current-derived and ice-transported material was reconstructed using clay-mineral and heavy-mineral analysis. Conclusions on biogenic production were drawn by determination of biogenic opal and total organic carbon. It was found that the ice shelf front started to retreat from the site around 12.8 ka BP. This coincides with results from other records in Prydz Bay and suggests warming during the early Holocene optimum next to global sea level rise as the main trigger. Ice-rafted debris was then supplied to the site until 5.5 cal. ka BP, when Holocene global sea level rise stabilized and glacial isostatic rebound on MacRobertson Land commenced. Throughout the Holocene, three episodes of enhanced bottom-water activity probably due to elevated brine rejection in Cape Darnley polynya occured between 11.5 and 9 cal. ka BP, 5.6 and 4.5 cal. ka BP and since 1.5 cal. ka BP. These periods are related to shifts from warmer to cooler conditions at the end of Holocene warm periods, in particular the early Holocene optimum, the mid-Holocene warm period and at the beginning of the neoglacial. In

  2. 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

  3. Geology of the Grove Mountains in East Antarctica--New evidence for the final suture of Gondwana Land

    Institute of Scientific and Technical Information of China (English)

    LIU; Xiaohan(刘小汉); ZHAO; Yue(赵越); LIU; Xiaochun(刘晓春); YU; Liangjun(俞良军)

    2003-01-01

    Grove Mountains consists mainly of a series of high-grade (upper amphibolite to granulite facies) metamorphic rocks, including felsic granulite, granitic gneiss, mafic granulite lenses and charnockite, intruded by late tectonic gneissic granite and post-tectonic granodioritic veins. Geochemical analysis demonstrates that the charnockite, granitic gneiss and granite belonged to aluminous A type plutonic rocks, whereas the felsic and mafic granulite were from supracrustal materials as island-arc, oceanic island and middle oceanic ridge basalt. A few high-strained shear zones disperse in regional stable sub-horizontal foliated metamorphic rocks. Three generations of ductile deformation were identified, in which D1 is related to the event before Pan-African age, D2 corresponds to the regional granulite peak metamorphism, whereas D3 reflects ductile extension in late Pan-African orogenic period. The metamorphic reactions from granitic gneiss indicate a single granulite facies event, but 3 steps from mafic granulite, with P-T condition of M1 800℃, 9.3×105 Pa; M2 800-810℃, 6.4×105 Pa ; and M3 650℃ have been recognized. The U-Pb age data from representative granitic gneiss indicate (529±14) Ma of peak metamorphism, (534±5) Ma of granite emplacement, and (501±7) Ma of post-tectonic granodioritic veins. All these evidences suggest that a huge Pan-African aged mobile belt exists in the East Antarctic Shield extending from Prydz Bay via Grove Mountains to the southern Prince Charles Mountains. This orogenic belt could be the final suture during the Gondwana Land assemblage.

  4. Influence of climatic teleconnections on the temporal isotopic variability as recorded in a firn core from the coastal Dronning Maud Land, East Antarctica

    Indian Academy of Sciences (India)

    Sushant S Naik; Meloth Thamban; A Rajakumar; Witty D’Souza; C M Laluraj; Arun Chaturvedi

    2010-02-01

    Ice and firn core studies provide one of the most valuable tools for understanding the past climate change. In order to evaluate the temporal isotopic variability recorded in ice and its relevance to environmental changes, stable isotopes of oxygen and hydrogen were studied in a firn core from coastal Dronning Maud Land, East Antarctica. The annual 18O profile of the core shows a close relation to the El Niño Southern Oscillation (ENSO) variability. The ENSO indices show significant correlation with the surface air temperatures and 18O values of this region during the austral summer season and support an additional influence related to the Southern Annular Mode (SAM). The correlation between the combined ENSO-SAM index and the summer 18O record seems to have been caused through an atmospheric mechanism. Snow accumulation in this region illustrates a decreasing trend with opposite relationships with 18O data and surface air temperature prior and subsequent to the year 1997. A reorganization of the local water cycle is further indicated by the deuterium excess data showing a shift around 1997, consistent with a change in evaporation conditions. The present study thus illustrates the utility of ice-core studies in the reconstruction of past climate change and suggests possible influence of climatic teleconnections on the snow accumulation rates and isotopic profiles of snow in the coastal regions of east Antarctica.

  5. 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.

  6. Spatial and temporal variability of snow accumulation in Dronning Maud Land, East Antarctica, including two deep ice coring sites at Dome Fuji and EPICA DML

    Directory of Open Access Journals (Sweden)

    S. Fujita

    2011-08-01

    Full Text Available To better understand the spatio-temporal variability of the glaciological environment in Dronning Maud Land (DML, East Antarctica, investigations were carried out along the 2800-km-long Japanese-Swedish IPY 2007/2008 traverse. The route covers ice sheet ridges and two deep ice coring sites at Dome Fuji and EPICA DML. The surface mass balance (SMB distribution was derived based on analysis of isochrones within snow pits, firn cores and subsurface radar signals. The SMB averaged over various time scales in the Holocene was determined. This was then compared with various glaciological data. We find that the large-scale distribution of the SMB depends on the surface elevation, continentality and interactions between ice sheet ridges and the prevailing counterclockwise windfield in DML. A different SMB is found for the windward and leeward sides of the ridges. Local-scale variability in the SMB is essentially governed by bedrock topography which determines the local surface topography. In the eastern part of DML, the accumulation rate in the second half of the 20th century is found to be higher by 15 % compared to averages over longer periods of 722 a or 7.9 ka before AD 2008. A similar trend has been reported for many inland plateau sites in East Antarctica.

  7. Glacial retreat in the Amundsen Sea sector, West Antarctica - first cosmogenic evidence from central Pine Island Bay and the Kohler Range

    Science.gov (United States)

    Lindow, Julia; Castex, Marion; Wittmann, Hella; Johnson, Joanne S.; Lisker, Frank; Gohl, Karsten; Spiegel, Cornelia

    2014-08-01

    The Amundsen Sea Embayment of West Antarctica hosts one of the most rapidly changing sectors of the West Antarctic Ice Sheet. With the fastest-flowing ice streams in Antarctica, the region around Pine Island Bay is characterized by rapid ice-sheet thinning and grounding-line retreat. Published surface-exposure data are limited to a few isolated nunataks making it difficult to assess the long-term deglacial history of the area. To address this, we correlate existing records of lateral ice-stream retreat from marine sediment cores with onshore glacial thinning in two key areas of eastern Marie Byrd Land: the Kohler Range and Pine Island Bay. Our 10Be surface-exposure ages are the first from the isolated Kohler Range and show that the nunataks there became ice-free between 8.6 and 12.6 ka. This implies a minimum long-term average thinning rate of 3.3 ± 0.3 cm/yr, which is one order of magnitude lower than recent rates based on satellite data. We also present pre- to early Holocene 10Be surface-exposure ages from two islands located approximately 80 km downstream of the Pine Island Glacier ice-shelf front to constrain the lateral deglacial history in the Pine Island Bay area. This study provides insight into the significance of local ice sheet variations and suggests that the post-LGM history in the Amundsen Sea sector was characterized by glacial thinning as well as lateral retreat in pre- to early Holocene times.

  8. Unusual biogenic calcite structures in two shallow lakes, James Ross Island, Antarctica

    Science.gov (United States)

    Elster, J.; Nedbalová, L.; Vodrážka, R.; Láska, K.; Haloda, J.; Komárek, J.

    2016-01-01

    The floors of two shallow endorheic lakes, located on volcanic surfaces on James Ross Island, are covered with calcareous organosedimentary structures. Their biological and chemical composition, lake water characteristics, and seasonal variability of the thermal regime are introduced. The lakes are frozen down to the bottom for 8-9 months a year and their water chemistry is characterised by low conductivity and neutral to slightly alkaline pH. The photosynthetic microbial mat is composed of filamentous cyanobacteria and microalgae that are considered to be Antarctic endemic species. The mucilaginous black biofilm is covered by green spots formed by a green microalga and the macroscopic structures are packed together with fine material. Thin sections consist of rock substrate, soft biofilm, calcite spicules and mineral grains originating from different sources. The morphology of the spicules is typical of calcium carbonate monocrystals having a layered structure and specific surface texture, which reflect growth and degradation processes. The spicules' chemical composition and structure correspond to pure calcite. The lakes' age, altitude, morphometry, geomorphological and hydrological stability, including low sedimentation rates, together with thermal regime predispose the existence of this community. We hypothesise that the precipitation of calcite is connected with the photosynthetic activity of the green microalgae that were not recorded in any other lake in the region. This study has shown that the unique community producing biogenic calcite spicules is quite different to any yet described.

  9. 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

  10. Age Estimates of Holocene Glacial Retreat in Lapeyrère Bay, Anvers Island, Antarctica

    Science.gov (United States)

    Mead, K. A.; Wellner, J. S.; Rosenheim, B. E.

    2011-12-01

    Lapeyrère Bay is a fjord on the eastern side of Anvers Island, located off the Western Antarctic Peninsula. Anvers island has a maximum elevation of 2400m (comprised of ice overlaying bedrock), and experiences colder temperatures and more precipitation than the South Shetlands, which are ~230km to the north. Two glaciers enter Lapeyrère Bay, one large and vulnerable to avalanching, the Iliad Glacier, and one smaller glacier confined to a northern unnamed cove. Though several research cruises have visited Lapeyrère Bay, very little has been published on the fjord's glacial retreat history or sediment flux. The primary purpose of this study is to reconstruct the glacial retreat and sediment flux histories of Lapeyrère Bay using a SHALDRIL core and standard piston cores for chronology and sedimentary facies analysis, and multibeam swath bathymetry data for identifying seafloor morphological features. Preliminary core data from the proximal northern flank of Lapeyrère Bay show greenish grey sandy mud with scattered pebble and sand lens lithology. A core taken in the distal-most part of the fjord is largely diatomaceous sediment grading into grey silty mud with thin sandy turbidites. Multibeam data has exposed seafloor features including a grounding zone wedge at the entrance of the unnamed cove of northern Lapeyrère Bay, drumlins, glacial lineations, and a glacial outwash fan near the ocean-termination of the Iliad glacier. Additionally, this study seeks to assess the effectiveness of a novel 14C method of dating sediment lacking sufficient calcareous material for carbonate 14C dating. The method being tested is ramped pyrolysis radiocarbon analysis, which dates individual fractions of organic material. It is hypothesized that ramped pyrolysis will improve upon bulk acid insoluble organic material (AIOM) dating, as AIOM can include both autochthonous syndepositionally aged carbon and allochthonous pre-aged carbon, resulting in 14C ages inherently older than the

  11. Potential contribution of hydro power plants to the energy consumption of East Asian islands

    OpenAIRE

    Hoes, O. A. C.; Meijer, L.J.J.; Sarfianto, D.R.; R. J. van der Ent

    2014-01-01

    Population growth, increasing energy demand and depleting fossil fuel resei-ves put a pressure on conventional methods of electricity generation. Hydropower is an alternative energy source that is known to have a large capacity potential. However, previous estimations of the potential capacity have been inconsistent and incomplete. In this study we identified all locations on East Asian islands (from Japan, Taiwan Phillipines to Indonesia) which are suitable for hydropower. For this we combin...

  12. Environmental monitoring and management proposals for the Fildes Region, King George Island, Antarctica

    Directory of Open Access Journals (Sweden)

    Christina Braun

    2012-05-01

    Full Text Available The Antarctic terrestrial environment is under increasing pressure from human activities. The Fildes Region is characterized by high biodiversity, but is also a major logistic centre for the northern Antarctic Peninsula. Different interests, from scientific research, nature conservation, protection of geological and historical values, station operations, transport logistics and tourism, regularly overlap in space and time. This has led to increasing conflict among the multiple uses of the region and breaches of the legal requirements for environmental protection that apply in the area. The aim of this study was to assess the impacts of human activities in the Fildes Region by monitoring the distribution of bird and seal breeding sites and recording human activities and their associated environmental impacts. Data from an initial monitoring period 2003–06 were compared with data from 2008–10. We observed similar or increased levels of air, land and ship traffic, but fewer violations of overflight limits near Antarctic Specially Protected Area No. 150 Ardley Island. Open waste dumping and oil contamination are still major environmental impacts. Scientific and outdoor leisure activities undertaken by station personnel are more frequent than tourist activities and are likely to have a commensurate level of environmental impact. Despite the initial success of some existing management measures, it is essential that scientific and environmental values continue to be safeguarded, otherwise environmental impacts will increase and the habitat will be further degraded. We argue that the Fildes Region should be considered for designation as an Antarctic Specially Managed Area, a measure that has proven effective for environmental management of vulnerable areas of the Antarctic.

  13. Observation of a mesospheric front in a thermal-doppler duct over King George Island, Antarctica

    Directory of Open Access Journals (Sweden)

    J. V. Bageston

    2011-12-01

    Full Text Available A mesospheric front was observed with an all-sky airglow imager on the night of 9–10 July 2007 at Ferraz Station (62° S, 58° W, located on King George island on the Antarctic Peninsula. The observed wave propagated from southwest to northeast with a well defined wave front and a series of crests behind the main front. The wave parameters were obtained via a 2-D Fourier transform of the imager data providing a horizontal wavelength of 33 km, an observed period of 6 min, and a horizontal phase speed of 92 m s−1. Simultaneous mesospheric winds were measured with a medium frequency (MF radar at Rothera Station (68° S, 68° W and temperature profiles were obtained from the SABER instrument on the TIMED satellite. These wind and temperature profiles were used to estimate the propagation environment of the wave event. A wavelet technique was applied to the wind in the plane of wave propagation at the OH emission height spanning three days centered on the front event to define the dominant periodicities. Results revealed a dominance of near-inertial periods, and semi-diurnal and terdiurnal tides suggesting that the ducting structure enabling mesospheric front propagation occurred on large spatial scales. The observed tidal motions were used to reconstruct the winds employing a least-squares method, which were then compared to the observed ducting environment. Results suggest an important contribution of large-scale winds to the ducting structure, but with buoyancy frequency variations in the vertical also expected to be important. These results allow us to conclude that the wave front event was supported by a duct including contributions from both winds and temperature.

  14. Quantifying coastal connectivity of coral spawn and larvae around Ryukyu Islands in the East China Sea

    Science.gov (United States)

    Odani, S.; Uchiyama, Y.; Kashima, M.; Kamidaira, Y.; Mitarai, S.

    2016-12-01

    Ryukyu Islands in the East China Sea are in a subtropical climate, hosting desirable environment for abundant coral ecosystem. Okinawa Main Island is the most densely populated island among them with tremendous tourist attractions including enchanting coral reefs and beaches. Kamidaira et al. (2016) suggested that the Kuroshio warm water maintains warmer water temperature favorable to corals around the island due mainly to intermittent eddy heat transport. It is presumed that the Kuroshio and associated eddy mixing also promote the transport and dispersal of coral spawn and larvae across the islands, whereas the area has suffered from coral breeching in the recent decades. Therefore, for optimal preservation and protection of the coral habitats around Ryukyu Island, we conduct a double nested high-resolution synoptic ocean modeling using ROMS with grid spacing down to 1 km coupled with an offline Lagrangian particle tracking model to investigate dispersal of coral spawn and larvae released from about 20 major islands and lagoons. Based on the model outcome, we quantify connectivity using Lagrangian probability density functions (PDFs) of the Lagrangian particles (e.g., Mitarai et al., 2009) among Ryukyu Islands. We then focus on the larval dispersal released from Sekisei Lagoon in Yaeyama Islands close to Taiwan, where we have carried out a series of in-situ surface drifter measurement. To compare the observation with the model, 160 source and sink patches with a diameter of 3 km are defined around Sekisei Lagoon and Okinawa Main Island for quantification of the detailed connectivity between them. The advection time is assumed for no more than 3 weeks to represent the lifespan of coral spawn and larvae. A PDF analysis suggests that the particles mostly remain near the released areas with predominant clockwise circulation around the lagoon, while approximately less than 5 % of particles are trapped and transported northeastward in long distance by the Kuroshio. The

  15. A new biogeographically disjunct giant gecko (Gehyra: Gekkonidae: Reptilia) from the East Melanesian Islands

    Science.gov (United States)

    Oliver, Paul M.; Clegg, Jonathan R.; Fisher, Robert N.; Richards, Stephen J.; Taylor, Peter N.; Jocque, Merlijn M. T.

    2016-01-01

    The East Melanesian Islands have been a focal area for research into island biogeography and community ecology. However, previously undescribed and biogeographically significant new species endemic to this region continue to be discovered. Here we describe a phylogenetically distinct (~20% divergence at the mitochondrial ND2 gene) and biogeographically disjunct new species of gecko in the genus Gehyra, from the Admiralty and St Matthias Islands. Gehyra rohan sp. nov. can be distinguished from all congeners by the combination of its very large size, ring of bright orange scales around the eye, moderate degree of lateral folding on the limbs and body, and aspects of head, body and tail scalation. Molecular data indicate mid to late Miocene divergence of the new species from nearest relatives occurring nearly 2000 kilometres away in Vanuatu and Fiji. Large Gehyra have not been recorded on the intervening large islands of the Bismark Archipelago (New Britain and New Ireland) and the Solomon Islands, suggesting this dispersal pre-dated the current configuration of these islands, extinction in intervening regions, or potentially elements of both. Conversely, low genetic divergence between disjunct samples on Manus and Mussau implies recent overseas dispersal via either natural or anthropogenic means.

  16. Observation of a mesospheric front in a dual duct over King George Island, Antarctica

    Directory of Open Access Journals (Sweden)

    J. V. Bageston

    2011-05-01

    Full Text Available A mesospheric bore was observed with an all-sky airglow imager on the night of 9–10 July 2007 at Ferraz Station (62° S, 58° W, located on King George island on the Antarctic Peninsula. The observed bore propagated from southwest to northeast with a well defined wave front and a series of crests behind the main front. There was no evidence of dissipation during its propagation within the field of view. The wave parameters were obtained via a 2-D Fourier transform of the imager data providing a horizontal wavelength of 33 km, an observed period of 6 min, and a horizontal phase speed of 92 m s−1. Simultaneous mesospheric winds were measured with a medium frequency (MF radar at Rothera Station (68° S, 68° W and temperature profiles were obtained from the SABER instrument on the TIMED satellite. These wind and temperature profiles were used to estimate the propagation environment of the bore. A wavelet technique was applied to the wind in the plane of bore propagation at the OH emission height spanning three days centered on the bore event to define the dominant periodicities. Results revealed a dominance of near-inertial periods, and semi-diurnal and terdiurnal tides suggesting that the ducting structure enabling bore propagation occurred on large spatial scales. The observed tidal motions were used to reconstruct the winds employing a least-squares method, which were then compared to the observed ducting environment. Results suggest an important contribution of large-scale winds to the ducting structure, but with buoyancy frequency variations in the vertical also expected to be important. These results allow us to conclude that the bore was supported by a duct including contributions from both winds and temperature (or stability. A co-located airglow temperature imager operated simultaneously with the all-sky imager confirmed that the bore event was the dominant small-scale wave event during the analysis interval.

  17. Morphology and ecology of bivalve molluscs from Admiralty Bay, King George Island, Antarctica

    Directory of Open Access Journals (Sweden)

    Theresinha M. Absher

    1998-08-01

    Full Text Available Bivalve species were collected from shallow coastal areas of King George Island (Martel, Mackellar and Ezcurra Inlets of Admiralty Bay. Twenty one species belonging to 16 genera and 12 families were identified and their morphometric and morphological shell characteristics were described. Three main characteristics were found to be common to the majority of the bivalve species sampled: 1 thin fragile shells; 2 small size of individuals (76%, and 3 the lack of true cardinal teeth (72%. Comparison of calcium data from a tropical estuary and a subantarctic coastal shallow area suggested that the calcium in the sea water was not a constraint to shell building but shell thickness could be an adaptation to the efficiency of energy partitioning. Small individual size and the lack of true cardinal teeth are discussed in relation to a high deposition environment and widespread mud bottoms.Espécies de bivalves foram coletadas na região costeira rasa da Ilha Rei George (Enseadas Martel, Mackellar e Ezcurra da Baía do Almirantado. Vinte e uma espécies pertencentes a 16 gêneros e 12 famílias foram identificadas e as caractrísticas morfológicas e morfométricas das conchas descritas. Destacaram-se 3 características principais comuns à maioria das espécies: 1 conchas finas e frágeis; 2 pequeno tamanho dos indivíduos (76%, e 3 a ausência de dentes cardinais (72%. A comparação entre os dados de cálcio de um estuário tropical e uma região rasa costeira subantártica sugeriu que os valores de cálcio na água do mar não seriam uma restrição à formação das conchas, mas a espessura das conchas poderia ser uma adaptação à eficiência na distribuição da energia. Discute-se a ausência de dentes cardinais e pequeno tamanho dos indivíduos em ralação a um ambiente de alta deposição e abundância de fundos lodosos.

  18. Alicyclobacillus sp. strain CC2, a thermo-acidophilic bacterium isolated from Deception Island (Antarctica) containing a thermostable superoxide dismutase enzyme

    Institute of Scientific and Technical Information of China (English)

    Daniela N. Correa-Llantén; Maximiliano J. Amenábar; Patricio A. Muñoz; María T. Monsalves; Miguel E. Castro; Jenny M.Blamey

    2014-01-01

    A gram-positive, rod-shaped, aerobic, thermo-acidophilic bacterium CC2 (optimal temperature 55℃and pH 4.0), belonging to the genus Alicyclobacillus was isolated from geothermal soil collected from“Cerro Caliente”, Deception Island, Antarctica. Owing to the harsh environmental conditions found in this territory, microorganisms are exposed to conditions that trigger the generation of reactive oxygen species (ROS). They must have an effective antioxidant defense system to deal with this oxidative stress. We focused on one of the most important enzymes: superoxide dismutase, which was partially purified and characterized. This study presents the ifrst report of a thermo-acidophilic bacterium isolated from Deception Island with a thermostable superoxide dismutase (SOD).

  19. Active tectonics on Deception Island (West-Antarctica): A new approach by using the fractal anisotropy of lineaments, fault slip measurements and the caldera collapse shape

    Science.gov (United States)

    Pérez-López, R.; Giner-Robles, J.L.; Martínez-Díaz, J.J.; Rodríguez-Pascua, M.A.; Bejar, M.; Paredes, C.; González-Casado, J.M.

    2007-01-01

    The tectonic field on Deception Island (South Shetlands, West Antarctica) is determined from structural and fractal analyses. Three different analyses are applied to the study of the strain and stress fields in the area: (1) field measurements of faults (strain analysis), (2) fractal geometry of the spatial distribution of lineaments and (3) the caldera shape (stress analyses). In this work, the identified strain field is extensional with the maximum horizontal shortening trending NE-SW and NW-SE. The fractal technique applied to the spatial distribution of lineaments indicates a stress field with SHMAX oriented NE-SW. The elliptical caldera of Deception Island, determined from field mapping, satellite imagery, vents and fissure eruptions, has an elongate shape and a stress field with SHMAX trending NE-SW.

  20. Recent changes detected on two glaciers at the northern part of James Ross Island, Antarctica

    Science.gov (United States)

    Nývlt, Daniel; Kopačková, Veronika; Láska, Kamil; Engel, Zbyněk.

    2010-05-01

    Antarctic Peninsula is one of the regions, which have been exposed to the most rapid warming of the Earth since 1950. Consequences of climate changes are clearly documented by recent disintegration of ice shelves on both sides of the Antarctic Peninsula as well as by the retreat of land-based glaciers. James Ross Island, located close to the northernmost tip of the Antarctic Peninsula, represents an excellent place to study changes in the glacier mass-balance and their sensitivity to a regional warming trend. Two different types of glaciers of the Ulu Peninsula, the Whisky Glacier and the Davies Dome have been studied. Multi-temporal remote sensing data (aerial photographs, Landsat MSS, TM and ETM+ and Aster satellite optical and thermal multispectral data) and field survey allowed detecting changes in extent (2-D) as well as calculating glacier mass-balance changes (3-D) for these two glaciers from 1977 to 2009. The Whisky Glacier is a well-delimited valley glacier located mostly below the local Equilibrium line altitude (ELA). The glacier with high-flow velocities is fed by an intensive snow accumulation caused by prevailing southwestern winds. The Whisky Glacier covers an area of 2.3 km2 and its altitude varies from 215 to 475 m a.s.l. The Davies Dome is a flat-bottom dome glacier. Significant parts of its surface are located above the ELA and limited flow velocities are characteristic for the most parts of its body. However, the Davies Dome has a single 500-700 m wide southwestern outlet flowing towards the Whisky Bay. The Davies Dome extends an area of 6.7 km2 and its altitude ranges from 0 to 514 m a.s.l. Both glaciers experienced massive extension of their ice tongues towards the Brandy Bay during the mid Holocene. Lateral moraines located in front of the both glaciers heading down to the left coast of the Brandy Bay document this event. According to the remote sensing data and field investigations both glaciers have retreated since 1977. Between 2006 and

  1. 33 CFR 117.799 - Long Island, New York Inland Waterway from East Rockaway Inlet to Shinnecock Canal.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Long Island, New York Inland Waterway from East Rockaway Inlet to Shinnecock Canal. 117.799 Section 117.799 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements New York § 117.799 Long Island,...

  2. 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...

  3. 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...

  4. Permafrost and snow monitoring at Rothera Point (Adelaide Island, Maritime Antarctica): Implications for rock weathering in cryotic conditions

    Science.gov (United States)

    Guglielmin, Mauro; Worland, M. Roger; Baio, Fabio; Convey, Peter

    2014-11-01

    In February 2009 a new permafrost borehole was installed close to the British Antarctic Survey Station at Rothera Point, Adelaide Island (67.57195°S 68.12068°W). The borehole is situated at 31 m asl on a granodiorite knob with scattered lichen cover. The spatial variability of snow cover and of ground surface temperature (GST) is characterised through the monitoring of snow depth on 5 stakes positioned around the borehole and with thermistors placed at three different rock surfaces (A, B and C). The borehole temperature is measured by 18 thermistors placed at different depths between 0.3 and 30 m. Snow persistence is very variable both spatially and temporally with snow free days per year ranging from 13 and more than 300, and maximum snow depths varying between 0.03 and 1.42 m. This variability is the main cause of high variability in GST, that ranged between - 3.7 and - 1.5 °C. The net effect of the snow cover is a cooling of the surface. Mean annual GST, mean summer GST, and the degree days of thawing and the n-factor of thawing were always much lower at sensor A where snow persistence and depth were greater than in the other sensor locations. At sensor A the potential freeze-thaw events were negligible (0-3) and the thermal stress was at least 40% less than in the other sensor locations. The zero curtain effect at the rock surface occurred only at surface A, favouring chemical weathering over mechanical action. The active layer thickness (ALT) ranged between 0.76 and 1.40 m. ALT was directly proportional to the mean air temperature in summer, and inversely proportional to the maximum snow depth in autumn. ALT temporal variability was greater than reported at other sites at similar latitude in the Northern Hemisphere, or with the similar mean annual air temperature in Maritime Antarctica, because vegetation and a soil organic horizon are absent at the study site. Zero annual amplitude in temperature was observed at about 16 m depth, where the mean annual

  5. Surface mass balance of the Wilkes and Victoria Land region (90-180°E), East Antarctica, from 1950 to 2005

    Science.gov (United States)

    Magand, O.; Genthon, C.; Frezzotti, M.; Ekaykin, A.; Fily, M.

    2005-12-01

    Based on thousands of field measurements and using improved interpolation techniques, the evaluation of the mean Antarctic Surface Mass Balance (SMB) was recently [Vaughan, et al., 1999] increased by 15% compared to accepted estimates [Giovinetto and Bentley, 1985], with differences exceeding 50% at drainage basin scales. Recent re-calculations of the Antarctic SMB [Giovinetto and Zwally, 2000], using essentially the same field data but applying different sorting and interpolation techniques, appear to agree better with [Vaughan, et al., 1999] than with the older evaluations. However, they still differ by as much as 30% at drainage basin scales, and even by 15% at the scale of East Antarctica as a whole [Rignot and Thomas, 2002]. Obviously, the current uncertainty on the SMB of Antarctica still needs to be reduced. In spite of more than 2000 reported field measurements [Giovinetto and Zwally, 2000], there are 3 major difficulties to building an accurate observation-based full map of the Antarctic SMB. 1) Depending on measurement technique and time sampling, the reliability, accuracy and representativeness of a given data is highly variable and may be very poor; 2) There are still huge gaps in the spatial coverage of the available measurements, and much of the Antarctic SMB estimation currently relies on interpolation; 3) Various measurements sample and various time periods are time-inconsistent, so that real temporal variability can induce spurious spatial variability. The primary goal of the present study is to provide a SMB data analysis that is, as much as possible, spatially and temporally representative of the Mass Balance occurring in the Antarctic sector of 90-180° E from 1950 to 2005. The previous database gathered published SMB data with few or no review about the reliability and validity of all the proposed values. The resulting SMB database for this sector is significantly different from the previously published compilations in [Vaughan, et al., 1999

  6. Marine magnetic anomalies as a link between the granulite belts of east coast of India and enderby land of Antarctica

    Digital Repository Service at National Institute of Oceanography (India)

    Murthy, K.S.R.; Rao, M.M.M.; Venkateswarlu, K.; Subrahmanyam, A.S.; Lakshminarayana, S.; Rao, T.C.S.

    Magnetic data of the eastern continental margin of India (ECMI) helped in demarcating the offshore extension of the granulite belts of east coast of India and their possible link to those of the East Aantarctica. Short wavelength and high amplitude...

  7. 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

  8. Spatial variability of chemical tracers in surface snow along the traverse route from the coast to 1000 km inland at east Dronning Maud Land, Antarctica

    Institute of Scientific and Technical Information of China (English)

    Toshitaka Suzuki; Yoshinori Iizuka; Teruo Furukawa; Kenichi Matsuoka; Kokichi Kamiyama; Okitsugu Watanabe

    2003-01-01

    We measured the spatial variability of Cl-, Na+, SO2-4, NO-3 and 7Be concentrations in snow cover along the traverse route from S16 to Dome Fuji station in east Dronning Maud Land, Antarctica.The concentrations of Cl- and Na+ at the coast exponentially decreased with distance from the coast up to 200 km inland.Between 200-1000 km inland, the concentrations of Na+ were nearly constant.On the other hand, the concentrations of Cl- increased with distance beyond 750 km inland.Furthermore, the contribution factors between Cl- and Na+ decreased and the Cl-/Na+ ratio and the nssCl-/Cl- ratio increased toward the interior of the continent.These results indicate that sea salt aerosols are transported from the coastal region toward the inland region of the Antarctic continent, and that a source of Cl- other than sea salt exists in the inland plateau of Antarctica.The concentrations of SO2-4, NO-3 and 7Be in snow were relatively high in the coastal region and the inland plateau region compared with those in the katabatic-wind region.

  9. Records of climatic changes and volcanic events in an ice core from Central Dronning Maud Land (East Antarctica) during the past century

    Indian Academy of Sciences (India)

    V N Nijampurkar; D K Rao; H B Clausen; M K Kaul; A Chaturvedi

    2002-03-01

    The depth profiles of electrical conductance, 18O, 210Pb and cosmogenic radio isotopes 10Be and 36Cl have been measured in a 30 m ice core from east Antarctica near the Indian station, Dakshin Gangotri. Using 210Pb and 18O, the mean annual accumulation rates have been calculated to be 20 and 21 cm of ice equivalent per year during the past ∼150 years. Using these acumulation rates, the volcanic event that occurred in 1815 AD, has been identified based on electrical conductance measurements. Based on 18O measurements, the mean annual surface air temperatures (MASAT) data observed during the last 150 years indicates that the beginning of the 19th century was cooler by about 2°C than the recent past and the middle of 18th century. The fallout of cosmogenic radio isotope 10Be compares reasonably well with those obtained on other stations (73° S to 90°S) from Antarctica and higher latitudes beyond 77°N. The fallout of 36Cl calculated based on the present work agrees well with the mean global production rate estimated earlier by Lal and Peters (1967) The bomb pulse of 36Cl observed in Greenland is not observed in the present studies a result which is puzzling and needs to be studied on neighbouring ice cores from the same region.

  10. 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.

  11. Glacial evolution in King George and Livingston Islands (Antarctica) since the Last Glacial Maximum based on cosmogenic nuclide dating and glacier surface reconstruction - CRONOANTAR project

    Science.gov (United States)

    Ruiz Fernández, Jesús; Oliva, Marc; Fernández Menéndez, Susana del Carmen; García Hernández, Cristina; Menéndez Duarte, Rosa Ana; Pellitero Ondicol, Ramón; Pérez Alberti, Augusto; Schimmelpfennig, Irene

    2017-04-01

    CRONOANTAR brings together researchers from Spain, Portugal, France and United Kingdom with the objective of spatially and temporally reconstruct the deglaciation process at the two largest islands in the South Shetlands Archipelago (Maritime Antarctica), since the Global Last Glacial Maximum. Glacier retreat in polar areas has major implications at a local, regional and even planetary scale. Global average sea level rise is the most obvious and socio-economically relevant, but there are others such as the arrival of new fauna to deglaciated areas, plant colonisation or permafrost formation and degradation. This project will study the ice-free areas in Byers and Hurd peninsulas (Livingston Island) and Fildes and Potter peninsulas (King George Island). Ice-cap glacier retreat chronology will be revealed by the use of cosmogenic isotopes (mainly 36Cl) on glacially originated sedimentary and erosive records. Cosmogenic dating will be complemented by other dating methods (C14 and OSL), which will permit the validation of these methods in regions with cold-based glaciers. Given the geomorphological evidences and the obtained ages, a deglaciation calendar will be proposed and we will use a GIS methodology to reconstruct the glacier extent and the ice thickness. The results emerging from this project will allow to assess whether the high glacier retreat rates observed during the last decades were registered in the past, or if they are conversely the consequence (and evidence) of the Global Change in Antarctica. Acknowledgements This work has been funded by the Spanish Ministry of Economy, Industry and Competitiveness (Reference: CTM2016-77878-P).

  12. Structural control of the Gagua "Wedge" Zone east of Taiwan Island on the southern Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    ZHENG Yanpeng; LIU Baohua; WU Jinlong; LIANG Ruicai; LIU Chenguang; ZHANG Zhengmin

    2005-01-01

    Based on compositive analysis and interpretation of the observed and historical data, the geophysical field characters and structural properties of the Gagua "Wedge" Zone of the sea area east of Taiwan Island and the primary tectonic stress direction and its variabilities of backarc spreading in the southern Okinawa Trough are studied. It is concluded from the study results that the Gagua "Wedge" Zone is structurally consistent with the Gagua ridge and two fault basins on both sides of the Gagua ridge, and adjusts the moving direction and distance of the western Philippine Sea plate to make the northwestward motion of the plate on its east side change to the northward subduction of the plate on its west side so that the primary tectonic stress direction of the Okinawa Trough changed from NW-SE to nearly N-S, which provided the stress source for the Okinawa Trough to enter the second spreading stage.

  13. Modelling the upwelling offthe east Hainan Island coast in summer 2010

    Science.gov (United States)

    Bai, Peng; Gu, Yanzhen; Li, Peiliang; Wu, Kejian

    2016-11-01

    A synoptic-scale upwelling event that developed offthe east coast of the Hainan Island (EHIU) in the summer of 2010 is defined well via processing the Moderate Resolution Imaging Spectroradiometer (MODIS) sea surface temperature (SST) data. The Regional Ocean Modeling System (ROMS) with high spatial resolution has been used to investigate this upwelling event. By comparing the ROMS results against tide station data, Argo float profiles and MODIS SST, it is confirmed that the ROMS reproduces the EHIU well. The cooler-water core (CWC) distinguished by waters wind stress curl that dominated the east Qiongzhou Strait mouth area suppressed the intensity of the CWC by 0.2-0.4°C. Further, nonlinear interaction between tidal currents and wind stress enhanced vertical mixing greatly, which would benefit the development of the CWC.

  14. Methane and nitrous oxide fluxes in relation to vegetation covers and bird activity in ice-free soils of Rip Point, Nelson Island, Antarctica

    Directory of Open Access Journals (Sweden)

    Ângela Denise Hubert Neufeld

    2015-02-01

    Full Text Available This study aimed to quantify the nitrous oxide (N2O and methane (CH4 fluxes at sites with different vegetation covers and where bird activity was present or absent using the static chamber method, on Rip Point, Nelson Island, maritime Antarctic. The sites were soils covered by Sanionia uncinata, lichens, Prasiola crispa, Deschampsia antarctica and bare soil. Seabirds used the P. crispa and D. antarctica sites as nesting areas. Soil mineral N contents, air and soil temperature and water-filled pore space were measured, and the content of total organic C and particulate organic C, total N, bulk density and texture were determined to identify controlling variables of the gas emissions. The N2O and CH4 flux rates were low for all sampling events. Mean N2O flux rates ranged from 0.11±1.93 up to 21.25±22.14 µg N2O m−2 h−1 for the soils under lichen and P. crispa cover, respectively. For the CH4 fluxes, only the P. crispa site showed a low positive mean (0.47±3.61 µg CH4 m−2 h−1. The bare soil showed the greatest absorption of CH4 (−11.92±5.7 µg CH4 m−2 h−1, probably favoured by the coarse soil texture. Bare soil and S. uncinata sites had N2O accumulated emissions close to zero. Net CH4 accumulated emission was observed only at the P. crispa site, which was correlated with NH4+ (p<0.001. These results indicate that seabird activity influences N2O and CH4 soil fluxes, while vegetation has little influence, and bare soil areas in maritime Antarctica could be greenhouse gas sinks.

  15. Synergetic merging of Cartosat-1 and RAMP to generate improved digital elevation model of Schirmacher oasis, east Antarctica

    Science.gov (United States)

    Jawak, S. D.; Luis, A. J.

    2014-11-01

    Available digital elevation models (DEMs) of Antarctic region generated by using radar altimetry and the Antarctic digital database (ADD) indicate elevation variations of up to hundreds of meters, which necessitates the generation of local DEM and its validation by using ground reference. An enhanced digital elevation model (eDEM) of the Schirmacher oasis region, east Antarctica, is generated synergistically by using Cartosat-1 stereo pair-derived photogrammetric DEM (CartoDEM)-based point elevation dataset and multitemporal radarsat Antarctic mapping project version 2 (RAMPv2) DEM-based point elevation dataset. In this study, we analyzed suite of interpolation techniques for constructing a DEM from RAMPv2 and CartoDEM-based point elevation datasets, in order to determine the level of confidence with which the interpolation techniques can generate a better interpolated continuous surface, and eventually improves the elevation accuracy of DEM from synergistically fused RAMPv2 and CartoDEM point elevation datasets. RAMPv2 points and CartoDEM points were used as primary data for various interpolation techniques such as ordinary kriging (OK), simple kriging (SK), universal kriging (UK), disjunctive kriging (DK) techniques, inverse distance weighted (IDW), global polynomial (GP) with power 1 and 2, local polynomial (LP) and radial basis functions (RBF). Cokriging of 2 variables with second dataset was used for ordinary cokriging (OCoK), simple cokriging (SCoK), universal cokriging (UCoK) and disjunctive cokriging (DCoK). The IDW, GP, LP, RBF, and kriging methods were applied to one variable, while Cokriging experiments were employed on two variables. The experiment of dataset and its combination produced two types of point elevation map categorized as (1) one variable (RAMPv2 Point maps and CartoDEM Point maps) and (2) two variables (RAMPv2 Point maps + CartoDEM Point maps). Interpolated surfaces were evaluated with the help of differential global positioning system

  16. Spatial variability of the active layer thickness at the Limnopolar Lake CALM-S site (Byers Peninsula, Livingston Island, Antarctica) and the role of snow cover.

    Science.gov (United States)

    de Pablo, Miguel A.; Molina, Antonio; Ramos, Miguel

    2016-04-01

    Since its establishment in early 2009, thaw depth has been measured in late January - early February at the Limnopolar Lake CALM-S site (A25) in Byers Peninsula, Livingston Island, Antarctica (62°38'59.1''S, 61°06'16.9''W). Ground, surface, and air temperatures have been also measured, as well as snow cover deep, derived from an array of miniature temperature loggers mounted into a wood mast (iButton from Maxim) (Lewcovicz, 2008). Thermal characterization of the active layer has been already done based on this data (de Pablo et al., 2013), as well as the interannual variability (de Pablo et al., 2014) and the snow cover evolution analyses (de Pablo et al., submitted). The results show that permafrost could exist at 120 cm depth, although the active layer is reducing, probably caused by the elongation on the snow cover duration. While the snow cover thickness remains approximately similar each winter, the snow offset delays, reducing the period in which solar radiation could heat the ground. In fact, during the last years, thaw depth was not able to be measured (in spite we visited the area in the approximately the same dates) due to thick snow layer remained covering the CALM-S site. However, we have not yet developed an analysis of the spatial variability of the thaw depth we measured each year, and how it could be conditioned by the ground properties (as slope or grain-size) or external factors, such as snow cover. In order to confirm the effect of the snow cover in the evolution of the active layer thickness, here we analyze the spatial variability of the thaw depth for the entire CALM-S site, and try to correlate it respect to the ground surface characteristics (grain-size, ground patterns, among others), the ground surface temperature and the snow cover thickness. Some of those data were acquired while the surface was visible during Antarctic field trips few years ago, and others (snow cover thickness) was measured by mechanical probing in each node. This

  17. Structural and Chemical Modification of Fe-Rich Smectite Associated with Microbial Fe-Respiration By Psychrophilic Bacteria in King George Island, West Antarctica

    Science.gov (United States)

    Jung, J.; Kim, J.; Lim, H. S.; Yoon, H.; Lee, Y. K.; Park, K.; Lee, J.; Kim, J. W.

    2014-12-01

    Surface soil samples were collected from Antarctic exploration (2010/2011, 2011/2012) at Barton Peninsula, King George Island, West Antarctica to determine the feasible biological alteration of clay minerals in Antarctica where the physical weathering is considered to be a major process. Seven areas (1226-1, 1226-2, 0101-4, 0105-1, 0105-2, 0107-2, 0107-3) from the coast toward the inland were investigated. The duration of exposure of soil samples to the air depending on the retraction of ice to the inland may affect the microbial activity resulting in the biogeochemical mineral alteration. The multiline of techniques for example, X-ray diffraction (XRD), Scanning Electron Microscope (SEM), wet chemistry analysis including the extent of Fe(III) reduction, and batch experiments of microbe-mineral interaction under the low temperature that mimics the Antarctic condition to understand the mechanism of biogeochemical alteration of clay minerals. Clay minerals of smectite, mica, chlorite and kaolinite were detected in the XRD profiles. The variation of relative amount of clay minerals in the regions indicated that the physical/biological alteration might be different depending on the duration of ice retraction. From the batch experiment using Nontronite (NAu-1), moreover, we confirm that Psychrophilic bacteria (Shewanella sp. isolated from King George Island) reduce structural Fe(III) of clay mineral, and occur structural change of smectite at low temperature (4℃ and 15℃). The present study, therefore, would present the feasibility of biological effects on chemical modification through the structural changes in clay mineral in cold environment and suggest a new pathway of Fe-supply into the Antarctic Ocean.

  18. Observations of vertical tidal motions of a floating iceberg in front of Shirase Glacier, East Antarctica, using a geodetic-mode GPS buoy

    Science.gov (United States)

    Aoyama, Yuichi; Kim, Tae-Hee; Doi, Koichiro; Hayakawa, Hideaki; Higashi, Toshihiro; Ohsono, Shingo; Shibuya, Kazuo

    2016-06-01

    A dual-frequency GPS receiver was deployed on a floating iceberg downstream of the calving front of Shirase Glacier, East Antarctica, on 28 December 2011 for utilizing as floating buoy. The three-dimensional position of the buoy was obtained by GPS every 30 s with a 4-5-cm precision for ca. 25 days. The height uncertainty of the 1-h averaged vertical position was ∼0.5 cm, even considering the uncertainties of un-modeled ocean loading effects. The daily evolution of north-south (NS), east-west (EW), and up-down (UD) motions shows periodic UD variations sometimes attaining an amplitude of 1 m. Observed amplitudes of tidal harmonics of major constituents were 88%-93% (O1) and 85%-88% (M2) of values observed in the global ocean tide models FES2004 and TPXO-8 Atlas. The basal melting rate of the iceberg is estimated to be ∼0.6 m/day, based on a firn densification model and using a quasi-linear sinking rate of the iceberg surface. The 30-s sampling frequency geodetic-mode GPS buoy helps to reveal ice-ocean dynamics around the calving front of Antarctic glaciers.

  19. Zircon U-Pb Ages from an Ultra-High Temperature Metapelite, Rauer Group, East Antarctica: Implications for Overprints by Grenvillian and Pan-African Events

    Science.gov (United States)

    Wang, Yanbin; Tong, Laixi; Liu, Dunyi

    2007-01-01

    SHRIMP U-Pb dating of zircon from an ultra-high temperature (UHT, ~1000 °C) granulite-facies metapelite from the Rauer Group, Mather Peninsula, east Antarctica, has yielded evidence for two episodes of metamorphic zircon growth, at ~1.00 Ga and ~530 Ma, and two episodes of magmatism in the source region for the protolith sediment, at ~2.53 and ~2.65 Ga, were identified from the zircon cores. Successive zircon growth at ~1.00 Ga and ~530 Ma records a sequence of distinct, widely spaced high-temperature metamorphic and/or anatectic events related to Grenvillian and Pan-African orogenesis. This study presents the first robust geochronological evidence for the timing of UHT metamorphism of the Rauer Group, supporting arguments that the peak UHT metamorphic event occurred at ~1.00 Ga and was overprinted by a separate high-grade event at ~530 Ma. The new age data indicate that the UHT granulites of the Rauer Group experienced a complex, multi-stage tectonothermal history, which cannot simply be explained via a single Pan-African (~500 Ma) high-grade tectonic event. This is critical in understanding the role of the eastern Prydz Bay region during the assembly of the east Gondwana supercontinent, and the newly recognized inherited Archaean ages (~2.53 and ~2.65 Ga) suggest a close tectonic relationship between the Rauer Group and the adjacent Archaean of the Vestfold Hills

  20. Sm-Nd and U-Pb isotopic constraints for crustal evolution during Late Neoproterozic from rocks of the Schirmacher Oasis, East Antarctica: geodynamic development coeval with the East African Orogeny

    Science.gov (United States)

    Ravikant, V.; Laux, J.H.; Pimentel, M.M.

    2007-01-01

    Recent post-750 Ma continental reconstructions constrain models for East African Orogeny formation and also the scattered remnants of ~640 Ma granulites, whose genesis is controversial. One such Neoproterozoic granulite belt is the Schirmacher Oasis in East Antarctica, isolated from the distinctly younger Pan-African orogen to the south in the central Droning Maud Land. To ascertain the duration of granulite-facies events in these remnants, garnet Sm-Nd and monazite and titanite U-Pb IDTIMS geochronology was carried out on a range of metamorphic rocks. Garnet formation ages from a websterite enclave and gabbro were 660±48 Ma and 587±9 Ma respectively, and those from Stype granites were 598±4 Ma and 577±4 Ma. Monazites from metapelite and metaquartzite yielded lower intercept UPb ages of 629±3 Ma and 639±5 Ma, respectively. U-Pb titanite age from calcsilicate gneiss was 580±5 Ma. These indicate peak metamorphism to have occurred between 640 and 630 Ma, followed by near isobaric cooling to ~580 Ma. Though an origin as an exotic terrane from the East African Orogen cannot be discounted, from the present data there is a greater likelihood that Mesoproterozoic microplate collision between Maud orogen and a northerly Lurio-Nampula block resulted in formation of these granulite belt(s).

  1. GENOTOXICITY OF SHALLOW WATERS NEAR THE BRAZILIAN ANTARCTIC STATION "COMANDANTE FERRAZ" (EACF, ADMIRALTY BAY, KING GEORGE ISLAND, ANTARCTICA

    Directory of Open Access Journals (Sweden)

    Arthur José da Silva Rocha

    2015-03-01

    Full Text Available Series of biomonitoring surveys were undertaken weekly in February 2012 to investigate the genotoxicity of the shallow waters around the Brazilian Antarctic Station "Comandante Ferraz" (EACF. The comet assay was applied to assess the damage to the DNA of hemocytes of the crustacean amphipods Gondogeneia antarctica collected from shallow waters near the Fuel Tanks (FT and Sewage Treatment Outflow (STO of the research station, and compare it to the DNA damage of animals from Punta Plaza (PPL and Yellow Point (YP, natural sites far from the EACF defined as experimental controls. The damage to the DNA of hemocytes of G. antarctica was not significantly different between sites in the biomonitoring surveys I and II. In survey III, the damage to the DNA of animals captured in shallow waters near the Fuel Tanks (FT and Sewage Treatment Outflow (STO was significantly higher than that of the control site of Punta Plaza (PPL. In biomonitoring survey IV, a significant difference was detected only between the FT and PPL sites. Results demonstrated that the shallow waters in front of the station may be genotoxic and that the comet assay and hemocytes of G. antarctica are useful tools for assessing genotoxicity in biomonitoring studies of Antarctic marine coastal habitats.

  2. Snow accumulation variability in Adelie Land (East Antarctica) derived from radar and firn core data. A 600 km transect from Dome C

    Science.gov (United States)

    Verfaillie, D.; Fily, M.; Le Meur, E.; Magand, O.; Jourdain, B.; Arnaud, L.; Favier, V.

    2012-07-01

    Polar ice sheets mass balance is a timely topic intensively studied in the context of global change and sea-level rise. However, obtaining mass balance estimates in Antarctica in particular, remains difficult due to various logistical problems. In the framework of the TASTE-IDEA program, labeled as an International Polar Year project, continuous Ground Penetrating Radar (GPR) measurements were carried out during a traverse realised in Adelie Land (East Antarctica) during the 2008-2009 austral summer between the Italo-French Dome C (DC) polar plateau site and French Dumont D'Urville (DdU) coastal station. The aim of this study was to process and interpret GPR data in terms of snow accumulation, to analyse its spatial and temporal variability along the DC-DdU traverse and compare it with historical data and modeling. The emphasis has been put on the last 300 yr, from the pre-industrial to recent time period. Beta-radioactivity counting and gamma spectrometry were studied in cores at LGGE laboratory, providing a depth-age calibration for radar measurements. Over the 600 km of usable GPR data, depth and snow accumulation were determined with the help of three distinct layers visible on the radargrams (≈1730, 1799 and 1941 AD). Preliminary results reveal a gradual accumulation increase towards the coast and the occurrence of previously undocumented undulating structures between 300 and 600 km from DC. Results agree fairly well with data from previous studies and modeling. Concluding on temporal variations is difficult because of the margin of error introduced by density estimation. This study should have various applications such as for model validation.

  3. Snow accumulation variability in Adelie Land (East Antarctica derived from radar and firn core data. A 600 km transect from Dome C

    Directory of Open Access Journals (Sweden)

    D. Verfaillie

    2012-07-01

    Full Text Available Polar ice sheets mass balance is a timely topic intensively studied in the context of global change and sea-level rise. However, obtaining mass balance estimates in Antarctica in particular, remains difficult due to various logistical problems. In the framework of the TASTE-IDEA program, labeled as an International Polar Year project, continuous Ground Penetrating Radar (GPR measurements were carried out during a traverse realised in Adelie Land (East Antarctica during the 2008–2009 austral summer between the Italo-French Dome C (DC polar plateau site and French Dumont D'Urville (DdU coastal station. The aim of this study was to process and interpret GPR data in terms of snow accumulation, to analyse its spatial and temporal variability along the DC-DdU traverse and compare it with historical data and modeling. The emphasis has been put on the last 300 yr, from the pre-industrial to recent time period. Beta-radioactivity counting and gamma spectrometry were studied in cores at LGGE laboratory, providing a depth-age calibration for radar measurements. Over the 600 km of usable GPR data, depth and snow accumulation were determined with the help of three distinct layers visible on the radargrams (≈1730, 1799 and 1941 AD. Preliminary results reveal a gradual accumulation increase towards the coast and the occurrence of previously undocumented undulating structures between 300 and 600 km from DC. Results agree fairly well with data from previous studies and modeling. Concluding on temporal variations is difficult because of the margin of error introduced by density estimation. This study should have various applications such as for model validation.

  4. The impact of glacier retreat from the Ross Sea on local climate: Characterization of mineral dust in the Taylor Dome ice core, East Antarctica

    Science.gov (United States)

    Aarons, S. M.; Aciego, S. M.; Gabrielli, P.; Delmonte, B.; Koornneef, J. M.; Wegner, A.; Blakowski, M. A.

    2016-06-01

    Recent declines in ice shelf and sea ice extent experienced in polar regions highlight the importance of evaluating variations in local weather patterns in response to climate change. Airborne mineral particles (dust) transported through the atmosphere and deposited on ice sheets and glaciers in Antarctica and Greenland can provide a robust set of tools for resolving the evolution of climatic systems through time. Here we present the first high time resolution radiogenic isotope (strontium and neodymium) data for Holocene dust in a coastal East Antarctic ice core, accompanied by rare earth element composition, dust concentration, and particle size distribution during the last deglaciation. We aim to use these combined ice core data to determine dust provenance, with variations indicative of shifts in either dust production, sources, and/or transport pathways. We analyzed a series of 17 samples from the Taylor Dome (77°47‧47″S, 158°43‧26″E) ice core, 113-391 m in depth from 1.1-31.4 ka. Radiogenic isotopic and rare earth element compositions of dust during the last glacial period are in good agreement with previously measured East Antarctic ice core dust records. In contrast, the Holocene dust dataset displays a broad range in isotopic and rare earth element compositions, suggesting a shift from long-range transported dust to a more variable, local input that may be linked to the retreat of the Ross Ice Shelf during the last deglaciation. Observed changes in the dust cycle inferred from a coastal East Antarctic ice core can thus be used to infer an evolving local climate.

  5. Coastal-change and glaciological map of the Trinity Peninsula area and south Shetland Islands, Antarctica: 1843-2001: Chapter A in Coastal-change and glaciological maps of Antarctica

    Science.gov (United States)

    Ferrigno, Jane G.; Cook, Alison J.; Foley, Kevin M.; Williams, Richard S.; Swithinbank, Charles; Fox, Adrian J.; Thomson, Janet W.; Sievers, Jorn

    2006-01-01

    Changes in the area and volume of polar ice sheets are intricately linked to changes in global climate, and the resulting changes in sea level could severely impact the densely populated coastal regions on Earth. Melting of the West Antarctic part alone of the Antarctic ice sheet would cause a sea-level rise of approximately 6 meters (m). The potential sea-level rise after melting of the entire Antarctic ice sheet is estimated to be 65 m (Lythe and others, 2001) to 73 m (Williams and Hall, 1993). In addition to its importance, the mass balance (the net volumetric gain or loss) of the Antarctic ice sheet is highly complex, responding differently to different conditions in each region (Vaughan, 2005). In a review paper, Rignot and Thomas (2002) concluded that the West Antarctic ice sheet is probably becoming thinner overall; although it is thickening in the west, it is thinning in the north. Thomas and others (2004), on the basis of aircraft and satellite laser altimetry surveys, believe the thinning may be accelerating. Joughin and Tulaczyk (2002), on the basis of analysis of ice-flow velocities derived from synthetic aperture radar, concluded that most of the Ross ice streams (ice streams on the east side of the Ross Ice Shelf) have a positive mass balance, whereas Rignot and others (2004) infer even larger negative mass balance for glaciers flowing northward into the Amundsen Sea, a trend suggested by Swithinbank and others (2003a,b, 2004). The mass balance of the East Antarctic ice sheet is thought by Davis and others (2005) to be strongly positive on the basis of the change in satellite altimetry measurements made between 1992 and 2003. 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 (1986), in subsequent recommendations by the Scientific Committee on Antarctic Research (SCAR) (1989, 1993), and by the National Science

  6. 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

  7. Investigation of snow-firn thickness and ground in the East Antarctica by means of geophysical radar

    Directory of Open Access Journals (Sweden)

    S. V. Popov

    2014-01-01

    Full Text Available Results of field investigations of snow-and-firn thickness and ground structures performed with the use of geophysical radar GPR (Ground-Penetrating Radar are discussed in the paper. Industrial radar GSSI SIR10B (Geophysical Survey Systems, Inc., USA with «5106» antenna (pulses frequency of 200 MHz was used. Its mean wavelength is 1.57±0.18 km. The main purpose of this work was to test this new technique for solution of glaciological and geological problems. The works were done during the austral summer season of 2012–2013 (58th Russian Antarctic Expedition in the Eastern Antarctica and mainly concentrated in the vicinity of the Lake Vostok, between the Russian stations Vostok and Progress (the Larsemann Hills. The GPR sounding was carried out together with precise geodetic measurements. The electromagnetic wave propagation in the snow-firn layer was analyzed using the data on density obtained from the 5G borehole at the Vostok Station. Investigations near the Vostok Station focused on a huge snow ridge or so-called “megadune” located eastward from the station at a distance of 30 km. About 80 km of the GPR cross-sections were collected there. Eight internal layers were traced. They demonstrated wavy forms with amplitudes of about 10 m high which corresponded to the megadunes. Main result of GPR investigations in the Larsemann Hills was our understanding of the snow-firn and ground structures in this region. The GPR data collected on structures of crevasses near Progress-1, shallow glacier near the Progress-3, and ground not far from Progress-2 are also discussed. Methodological recommendations on using the GPR under conditions of the Eastern Antarctica were developed.

  8. Occurrence, bioaccumulation and long-range transport of short-chain chlorinated paraffins on the Fildes Peninsula at King George Island, Antarctica.

    Science.gov (United States)

    Li, Huijuan; Fu, Jianjie; Zhang, Aiqian; Zhang, Qinghua; Wang, Yawei

    2016-09-01

    As a candidate persistent organic pollutant of the Stockholm Convention, short-chain chlorinated paraffins (SCCPs) have recently received particular attention. In this study, we investigated, for the first time, the concentrations of SCCPs in biota samples collected from the Fildes Peninsula at King George Island and Ardley Island, Antarctica. The concentrations of SCCPs ranged from 3.5 to 256.6ng/g (dry weight, dw), with a mean of 76.6±61.8ng/g dw, which was lower than those detected in mid- and low-latitude regions. The long-range transport behaviour of SCCPs was confirmed by both the detection of SCCPs in Antarctic remote areas and their special congener profiles. Short carbon chain (C10) congeners predominated in the Antarctic samples, which accounted for 56.1% of the total SCCP contamination. Such enrichment of C10 congeners indicated the high potential for the long-range transport of shorter chain congeners. In addition, SCCPs tended to be enriched in the species with high lipid contents. The biomagnification potential of SCCPs was found between Archeogastropoda (Agas) and Neogastropoda (Ngas), and the biomagnification factors of shorter chain congeners of SCCPs were higher than that of the longer chain ones. Considering that the endemic species in polar regions may be sensitive and vulnerable to the adverse effects of environmental contaminants, more attention should be paid on the bioaccumulation and toxicological risks of SCCPs in polar environments.

  9. CRED Gridded Bathymetry of Bank 66 and east French Frigate Shoals (100-020) in the Northwestern Hawaiian Islands

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — File 100-020b is a 60-m ASCII grid of depth data collected near Bank 66, East French Frigate Shoals in the Northwestern Hawaiian Islands as of May 2003. This grid...

  10. Simulating climate change impacts on forests and associated vascular epiphytes in a subtropical island of East Asia

    NARCIS (Netherlands)

    Hsu, R.C.C.; Tamis, W.L.M.; Raes, N.; de Snoo, G.R.; Wolf, J.H.D.; Oostermeijer, G.; Lin, S.H.

    2012-01-01

    Aim: This study aims to assess the impact of climate change on forests and vascular epiphytes, using species distribution models (SDMs). Location: Island of Taiwan, subtropical East Asia. Methods: A hierarchical modelling approach incorporating forest migration velocity and forest type-epiphyte

  11. Parasites as valuable stock markers for fisheries in Australasia, East Asia and the Pacific Islands.

    Science.gov (United States)

    Lester, R J G; Moore, B R

    2015-01-01

    Over 30 studies in Australasia, East Asia and the Pacific Islands region have collected and analysed parasite data to determine the ranges of individual fish, many leading to conclusions about stock delineation. Parasites used as biological tags have included both those known to have long residence times in the fish and those thought to be relatively transient. In many cases the parasitological conclusions have been supported by other methods especially analysis of the chemical constituents of otoliths, and to a lesser extent, genetic data. In analysing parasite data, authors have applied multiple different statistical methodologies, including summary statistics, and univariate and multivariate approaches. Recently, a growing number of researchers have found non-parametric methods, such as analysis of similarities and cluster analysis, to be valuable. Future studies into the residence times, life cycles and geographical distributions of parasites together with more robust analytical methods will yield much important information to clarify stock structures in the area.

  12. Comparison of the glacial chronology of Eastern Baffin Island, East Greenland and Camp century accumulation record

    DEFF Research Database (Denmark)

    Andrews, John; Funder, Svend Visby; Hjort, Chritian;

    1974-01-01

    level between 120,000 and 70,000 B.P. may well be related to glacierization of high arctic land masses under conditions of heavy snowfall. The subsequent reduction of accumulation in these high arctic areas then leads to a reduction of ice volume with a dry, cold interstadial correlative in time......Independently derived glacial chronologies from eastern Baffin Island, Canadian Arctic, and from East Greenland show essentially similar glaciologic trends that arc notably different from the response of the southern margins of the Laurentide and FCllnoscandia Ice Sheets. The critical aspe......~ts of both chronologies and the related extcn t of the ice sheets are (1) an early and maximum glacial stade, during the early phase of the last glaciation, reaching its peak abqut 100,000 to 75,000 yr ago; (2) an in terstadial about .70,000 n.p.; (3) an ice advance peaking about 45,000 yr ago; (4...

  13. Molecular identification larvae of Onchobothrium antarcticum (Cestoda: Tetraphyllidea) from marbled rockcod, Notothenia rossii, in Admiralty Bay (King George Island, Antarctica).

    Science.gov (United States)

    Laskowski, Zdzislaw; Rocka, Anna

    2014-10-01

    Antarctic bony fishes are infected with cestode larvae belonging to the order Tetraphyllidea (parasites as adults in chondrichthyans). Larvae of the Tetraphyllidea differ from each other in the morphology of their scoleces and represent five forms. There are larvae with bothridia subdivided into one, two and three loculi, bothridia sac-like in shape and bothridia undivided with hook-like projections. Only one species of the family Onchobothriidae, Onchobothrium antarcticum, has been described from Antarctica and larvae with trilocular bothridia were assigned to this cestode species. In this study, ten larvae obtained from Notothenia rossii and three adult specimens of Onchobothrium antarcticum isolated from Bathyraja eatonii were examined. A partial sequence of cytochrome c oxidase subunit 1 of three adult specimens and four larvae was identical. The remaining six larval sequences differed from the sequences obtained from adult cestodes. Partial sequences of lsrDNA of all analyzed larvae were identical. These results confirm the taxonomic affiliation of the larvae with trilocular bothridia parasitizing marbled rockcod in Antarctica as Onchobothrium antarcticum.

  14. The atmospheric HCHO budget at coastal East and West Antarctica: Impact of photochemical productions and snow emissions

    Science.gov (United States)

    Legrand, Michel; Preunkert, Susanne; Pépy, Guillaume; Jourdain, Bruno

    2013-04-01

    HCHO year-round records are now available at three coastal Antarctic sites, Neumayer and Halley in the Weddell Sea region and Dumont d'Urville in Terre Adélie, revealing a similar seasonal pattern with winter minima and summer maxima. However, absolute values significantly differ from site to site, during summer and winter. Monthly summer means exceed 450 pptv at NM, whereas a HCHO maximum of 130 pptv is observed at HA. Summer HCHO levels at DDU are similar to those at HA although higher levels were expected in relation with a methane oxidation being promoted by a 5 times higher level of OH at DDU than at HA. On the other hand, to match observations at NM and HA, snow emissions have to be considered whereas photochemical HCHO sources and sinks alone seem to explain observations at DDU. With the aim to draw a more comprehensive picture of the HCHO budget at coastal Antarctica we reexamine and discuss the three records using 0-D and 2-D calculations. In summer, the gas phase photochemistry is at all sites dominated by the CH4 oxidation, well before the oxidation of DMS and light alkenes. The CH4 oxidation chemistry is some three times more efficient in producing HCHO at DDU than at the two other sites because of more rich oxidant air masses coming from the Antarctic plateau reach DDU. The halogen chemistry, even being more important in relation with much sea-ice at HA and NM than at DDU, remains a weak HCHO sink. HCHO snow emissions represent an important contribution at the two Weddell Sea sites whereas they contribute only weakly at DDU. Although they are probably of similar strength around the three sites, the far thinner atmospheric boundary layer at HA (and even more at NM) compared to DDU permit an efficient accumulation of HCHO emitted by this surface source. In addition these coastal Antarctic data sets will be opposed to HCHO mixing ratios and snow fluxes obtained at inland Antarctica (Dome C) within the framework of the OPALE (Oxidant Production over

  15. The state of permafrost surrounding "Gabriel de Castilla" Spanish Antarctic Station (Deception Island, Antarctica): Studying the possible degradation due to the infrastructures heating effect.

    Science.gov (United States)

    Recio, Cayetana; Ángel de Pablo, MIguel; Ramos, MIguel; Molina, Antonio

    2015-04-01

    Permafrost degradation is one of the effects of the global warming. Many studies reveal the increase of active layer and reduction on permafrost table thickness, also in Antarctica. However, these trends on permafrost can be accelerated by the human activities, as the heating produced by the Antarctic stations infrastructures when they are not properly isolated from the ground. In Deception island, South Shetland Archipelago, we started 3 years ago a monitoring program at the 26 years old "Gabriel de Castilla" Spanish Antarctic Station (SAS), It is focused on charactering the state of permafrost, since in the coastal scarps at tens of meters from the station an increase on erosion had been detected. Although the main cause of the erosion of this coastal volcanoclastic materials is the 2 meters thick icefield which forms during the winter in the inner sea of this volcanic island, we want to detect any possible contribution to the coastal erosion caused by the permafrost degradation related to the SAS presence. We present our preliminary analysis based on three years of continuous ground temperature data, monitored at a shallow borehole (70 cm deep) in the SAS edge, together with the active layer thickness measured around the station and their vicinities in two thawing seasons. We complete this study with the analysis of the continuous temperature data taken inside the SAS and the air and ground temperatures below the station, acquired during the last Antarctic Campaign (December 2014-February 2015). These preliminary results are fundamental 1) to discard any contribution from the SAS presence, and to help to improve its thermal isolation, 2) to help improve our knowledge about the thermal state of permafrost in the area, and 3) to help to understand the causes of the coastal erosion in the volcanic Deception Island.

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

    Science.gov (United States)

    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

  17. 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

  18. 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.

  19. Climatic Variability in Davis Sea Sector (east Antarctica) Over the Past 250 Years Based on the 105 KM Ice Core Geochemical Data

    Science.gov (United States)

    Vladimirova, Diana; Ekaykin, Alexey

    2014-05-01

    In this study we present the air temperature and snow accumulation rate reconstruction in the Davis sea sector of East Antarctica over the past 250 years based on the geochemical investigations of the ice core from 105 km borehole (105 km inland from Mirny Station) drilled in 1988. The core was dated by the counting of the annual layers in the stable water isotope content (dD and d18O) profile and using the absolute date marker (Tambora volcano layer). The accumulation values were deduced from the thickness of the layers multiplied by the core density. The isotope content was transformed into the air temperature by comparing to the instrumental meteorological data from Mirny station. The reconstructed temperature series demonstrates a 0.5°C warming over the last 250 years. At the same time, snow accumulation rate was decreasing at least since the middle of the XIXth century. The climatic characteristics demonstrate cyclic variability with the periods of 6, 9, 19, 32 and about 120 years. Interestingly, in frames of 19-year cycle the temperature and isotope content are negatively related, which could be explained by a zonal shift of the moisture source area. Based on the data of the sodium concentration and "deuterium excess" values in the ice core, we assumed an increased sea ice extent in the XIXth century comparing to the present day.

  20. Study of inter-annual variations in surface melting over Amery Ice Shelf, East Antarctica, using space-borne scatterometer data

    Indian Academy of Sciences (India)

    S R Oza; R K K Singh; N K Vyas; Abhijit Sarkar

    2011-04-01

    The widespread retreat of glaciers can be considered as a response to the climate change. Being the largest retreating glacier–ice shelf system in East Antarctica, the Amery Ice Shelf–Lambert Glacier system plays an important role in contributing to sea level rise as well as the surrounding environment and climate. The present study is focused on the investigation of surface melting over the ice shelf using QuikSCAT Ku-band scatterometer data for more than 100 months covering the period from January 2000 to July 2009. The corresponding weather data of Davis Station was obtained from the website of Australian Antarctic Division. Very prominent dips in the backscatter observed in the month of January form a distinct signature caused by physical process of significant melting of the ice/snow surface. The steep increase again in February is attributed to the initiation of the freezing phenomenon. The derived melting index compared well with the passive microwave-based melting index derived by other researchers. A strong relationship was found between the scatterometer-derived melting index and the cumulative monthly mean air temperature. The highest melting was observed in the summer (January) of 2004, and thereafter gradual cooling appeared to take place in the subsequent years. The snow pack thickness, inferred from the backscatter variations, was found to be higher during winters (June) of 2004 and 2005, compared with other years.

  1. Temporal and spatial variations of atmospheric methane concentration and δ13C-CH4 near the surface on the Millor Peninsula, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    Liu Yashu; Zhu Renbin; Li Xianglan; Xu Hua; Sun Liguang

    2009-01-01

    During the 22nd Chinese Antarctic Research Expedition (CHINARE-22,2005/06), the atmospheric gas samples near the surface were taken on the Millor Peninsula and adjacent areas, east Antarctica, using Tedlar gas bags. The methane (CH4) concentration and δ13C-CH4 in those samples were analyzed in the laboratory. The average value of atmospheric CH4 concentration on this peninsula was (1.87±0.12)×10-6, slightly higher than the global average CH4 concentration. The summertime variation of CH4 concentrations showed a large fluctuation, corresponding to the variation of air temperatures. The average δ13C-CH4 was (-38.26±0.52)‰. CH4 concentrations and δ13C-CH4 at different sites varied from 1.74×10-6 to 2.56×10-6 and from -39.31‰ to -31.25‰, respectively. The factors affecting CH4 concentrations and δ13C-CH4 values have also been discussed in this study.

  2. Ice thickness, internal layers, and surface and subglacial topography in the vicinity of Chinese Antarctic Taishan station in Princess Elizabeth Land, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    Tang Xue-Yuan; Guo Jing-Xue; Sun Bo; Wang Tian-Tian; Cui Xiang-Bin

    2016-01-01

    We present the results of two ground-based radio-echo-sounding (RES) and GPS surveys performed in the vicinity of new Chinese Taishan station, Princess Elizabeth Land, East Antarctica, obtained in two austral summers during CHINARE 21 (2004/2005) and CHINARE 29 (2012/2013). The radar surveys measured ice thickness and internal layers using 60- and 150-MHz radar systems, and GPS measurements showed smooth surface slopes around the station with altitudes of 2607–2636 m above sea level (a.s.l.). Radar profiles indicate an average ice thickness of 1900 m, with a maximum of 1949 m and a minimum of 1856 m, within a square area measuring approximately 2 km × 2 km in the vicinity of the station. The ice thickness beneath the station site is 1870 m. The subglacial landscape beneath the station is quiet sharp and ranges from 662 to 770 m a.s.l., revealing part of a mountainous topography. The ice volume in the grid is estimated to be 7.6 km3. Along a 60-MHz radar profi le with a length of 17.6 km at the region covering the station site, some disturbed internal layers are identifi ed and traced; the geometry of internal layers within the englacial stratigraphy may imply a complex depositional process in the area.

  3. 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.

  4. An independently dated 2000-yr volcanic record from Law Dome, East Antarctica, including a new perspective on the dating of the c. 1450s eruption of Kuwae, Vanuatu

    Directory of Open Access Journals (Sweden)

    C. T. Plummer

    2012-05-01

    Full Text Available Volcanic eruptions are an important cause of natural climate variability. In order to improve the accuracy of climate models, precise dating and magnitude of the climatic effects of past volcanism are necessary. Here we present a 2000-yr record of Southern Hemisphere volcanism recorded in ice cores from the high accumulation Law Dome site, East Antarctica. The ice cores were analyzed for a suite of chemistry signals and are independently dated via annual layer counting, with 11 ambiguous years by the end of the record. Independently dated records are important to avoid circular dating where volcanic signatures are assigned a date from some external information rather than using the date it is found in the ice core. Forty-five volcanic events have been identified using the sulfate chemistry of the Law Dome record. Comparisons between Law Dome and NGRIP (Greenland volcanic records suggest Law Dome is the most accurately dated Antarctic volcanic dataset and allows for the records to be synchronized with NGRIP, leading to an improved global volcanic forcing dataset. Volcanic sulfate deposition estimates are important for modeling the climatic response to eruptions. The largest volcanic sulfate events in our record are dated at 1458 CE (Kuwae, Vanuatu, 1257 and 423 CE (unidentified. Using our record we refine the dating of previously known volcanic events and present evidence for two separate eruptions during the period 1450–1460 CE, potentially causing confusion in the assignment of the Kuwae (Vanuatu eruption to volcanic signatures during this time interval.

  5. Cook Island artifact geochemistry demonstrates spatial and temporal extent of pre-European interarchipelago voyaging in East Polynesia.

    Science.gov (United States)

    Weisler, Marshall I; Bolhar, Robert; Ma, Jinlong; St Pierre, Emma; Sheppard, Peter; Walter, Richard K; Feng, Yuexing; Zhao, Jian-Xin; Kirch, Patrick V

    2016-07-19

    The Cook Islands are considered the "gateway" for human colonization of East Polynesia, the final chapter of Oceanic settlement and the last major region occupied on Earth. Indeed, East Polynesia witnessed the culmination of the greatest maritime migration in human history. Perennial debates have critiqued whether Oceanic settlement was purposeful or accidental, the timing and pathways of colonization, and the nature and extent of postcolonization voyaging-essential for small founding groups securing a lifeline between parent and daughter communities. Centering on the well-dated Tangatatau rockshelter, Mangaia, Southern Cook Islands, we charted the temporal duration and geographic spread of exotic stone adze materials-essential woodworking tools found throughout Polynesia- imported for more than 300 y beginning in the early AD 1300s. Using a technique requiring only 200 mg of sample for the geochemical analysis of trace elements and isotopes of fine-grained basalt adzes, we assigned all artifacts to an island or archipelago of origin. Adze material was identified from the chiefly complex on the Austral Islands, from the major adze quarry complex on Tutuila (Samoa), and from the Marquesas Islands more than 2,400 km distant. This interaction is the only dated example of down-the-line exchange in central East Polynesia where intermediate groups transferred commodities attesting to the interconnectedness and complexity of social relations fostered during postsettlement voyaging. For the Cook Islands, this exchange may have lasted into the 1600s, at least a century later than other East Polynesian archipelagos, suggesting that interarchipelago interaction contributed to the later development of social hierarchies.

  6. Baseline concentrations of faecal sterols and assessment of sewage input into different inlets of Admiralty Bay, King George Island, Antarctica.

    Science.gov (United States)

    Martins, César C; Aguiar, Sabrina N; Wisnieski, Edna; Ceschim, Liziane M M; Figueira, Rubens C L; Montone, Rosalinda C

    2014-01-15

    The Antarctic region is one of the best preserved environments in the world. However, human activities such as the input of sewage result in the alteration of this pristine site. We report baseline values of faecal sterols in Admiralty Bay, Antarctica. Four sediment cores were collected during the 2006/2007 austral summer at the Ezcurra (THP and BAR), Mackelar (REF) and Martel (BTP) inlets. Concentrations of faecal sterols (coprostanol+epicoprostanol) were sterols in core layers for THP, BAR, REF and BTP, were 0.04 ± 0.02, 0.03 ± 0.01, 0.07 ± 0.01 and 0.04 ± 0.02 μg g(-1), respectively. These results established as natural contributions of faecal sterols, suggesting that these markers can be useful indicators of human-derived faecal input and contributing to monitoring programs to prevent anthropogenic impacts. Copyright © 2013 Elsevier Ltd. All rights reserved.

  7. Ecological differences of south polar skua populations from Fildes Peninsula of King George Island and eastern Larsemann Hills,Antarctica

    Institute of Scientific and Technical Information of China (English)

    Wang Zipan; Hans-Ulrich Peter

    2004-01-01

    A study has been done on the comparison of nesting and feeding behavior, population variances as well as breeding success between two populations of south polar skua (Catharacta maccormicki) from near Great Wall station on Fildes Peninsula and near Zhongshan station in Eastern Larsemann Hills, Antarctica. There are evident differences in their population ecology. The foraging habit is much related to regional ecosystem and food resources near their territorial area. Dependence on human food waste influences skua's diet,which considerably affects their behavior even population variation in both areas. The skuas in Zhongshan Station,could shorten and/or regulate the timing for their egg laying and hatching, and take precedence of one chick brooding, for keeping their breeding success, and subsequent species continuation.

  8. Environmental conditions of interstadial (MIS 3 and features of the last glacial maximum on the King George island (West Antarctica

    Directory of Open Access Journals (Sweden)

    S. R. Verkulich

    2013-01-01

    Full Text Available The interstadial marine deposits stratum was described in the Fildes Peninsula (King George Island due to field and laboratory investigations during 2008–2011. The stratum fragments occur in the west and north-west parts of peninsula in following forms: sections of soft sediments, containing fossil shells, marine algae, bones of marine animals and rich marine diatom complexes in situ (11 sites; fragments of shells and bones on the surface (25 sites. According to the results of radiocarbon dating, these deposits were accumulated within the period 19–50 ky BP. Geographical and altitude settings of the sites, age characteristics, taxonomy of fossil flora and fauna, and good safety of the soft deposits stratum allow to make following conclusions: during interstadial, sea water covered significant part of King George Island up to the present altitude of 40 m a.s.l., and the King George Island glaciation had smaller size then; environmental conditions for the interstadial deposit stratum accumulation were at least not colder than today; probably, the King George island territory was covered entirely by ice masses of Last glacial maximum not earlier than 19 ky BP; during Last glacial maximum, King George Island was covered by thin, «cold», not mobile glaciers, which contribute to conservation of the soft marine interstadial deposits filled with fossil flora and fauna.

  9. Corticosterone in relation to body mass in Adelie penguins (Pygoscelis adeliae) affected by unusual sea ice conditions at Ross Island, Antarctica.

    Science.gov (United States)

    Cockrem, J F; Potter, M A; Candy, E J

    2006-12-01

    Penguins naturally fast each year during breeding and again whilst moulting, and may lose more than 40% of body mass during a fast. Fasting in emperor (Aptenodytes forsteri) and king (Aptenodytes patagonicus) penguins has been divided into three phases, with phase III characterised by an increased rate of body mass loss, increased plasma corticosterone concentrations, and a change in behaviour leading to abandonment of the breeding attempt and return to sea to feed. Initial corticosterone concentrations and corticosterone responses to a handling stressor were measured in the current study to determine if they increase during phase III of fasting in Adelie penguins (Pygoscelis adeliae). The study was conducted in 2001 at the northern Cape Bird colony on Ross Island, Antarctica. Penguin breeding on Ross Island was disrupted in the 2001-2002 summer by a large iceberg (B15A) which stopped the normal movement of sea ice in the Ross Sea. Penguins departing from the Cape Bird colony were lighter than returning or incubating birds (3.39+/-0.10cf. 4.16+/-0.06 and 4.07+/-0.08kg). It is likely that the departing birds were males that had been lighter than normal when they arrived at the colony. Initial plasma corticosterone concentrations were higher in departing than returning or incubating penguins (6.89+/-1.69cf. 2.36+/-0.42 and 1.08+/-0.19ng/ml). Corticosterone responses to handling were also greater in departing penguins. Initial plasma corticosterone, concentrations at 30min and total and corrected integrated corticosterone responses were inversely related to body mass in departing penguins, whereas there were no relationships in arriving penguins. beta-hydroxybutyrate and uric acid concentrations were consistent with departing birds having entered phase III of fasting. The results indicate that corticosterone and corticosterone responses are elevated in phase III of fasting in the Adelie penguin.

  10. Roosevelt Island Climate Evolution Project (RICE): A 65 Kyr ice core record of black carbon aerosol deposition to the Ross Ice Shelf, West Antarctica.

    Science.gov (United States)

    Edwards, Ross; Bertler, Nancy; Tuohy, Andrea; Neff, Peter; Proemse, Bernedette; Feiteng, Wang; Goodwin, Ian; Hogan, Chad

    2015-04-01

    Emitted by fires, black carbon aerosols (rBC) perturb the atmosphere's physical and chemical properties and are climatically active. Sedimentary charcoal and other paleo-fire records suggest that rBC emissions have varied significantly in the past due to human activity and climate variability. However, few paleo rBC records exist to constrain reconstructions of the past rBC atmospheric distribution and its climate interaction. As part of the international Roosevelt Island Climate Evolution (RICE) project, we have developed an Antarctic rBC ice core record spanning the past ~65 Kyr. The RICE deep ice core was drilled from the Roosevelt Island ice dome in West Antarctica from 2011 to 2013. The high depth resolution (~ 1 cm) record was developed using a single particle intracavity laser-induced incandescence soot photometer (SP2) coupled to an ice core melter system. The rBC record displays sub-annual variability consistent with both austral dry-season and summer biomass burning. The record exhibits significant decadal to millennial-scale variability consistent with known changes in climate. Glacial rBC concentrations were much lower than Holocene concentrations with the exception of several periods of abrupt increases in rBC. The transition from glacial to interglacial rBC concentrations occurred over a much longer time relative to other ice core climate proxies such as water isotopes and suggests . The protracted increase in rBC during the transition may reflected Southern hemisphere ecosystem / fire regime changes in response to hydroclimate and human activity.

  11. Denaturing gradient gel electrophoresis fingerprinting of soil bacteria in the vicinity of the Chinese Great Wall Station, King George Island, Antarctica.

    Science.gov (United States)

    Pan, Qi; Wang, Feng; Zhang, Yang; Cai, Minghong; He, Jianfeng; Yang, Haizhen

    2013-08-01

    Bacterial diversity was investigated in soil samples collected from 13 sites around the Great Wall Station, Fildes Peninsula, King George Island, Antarctica, using denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes. The classes alpha-, beta-, and gamma-Proteobacteria, as well as the phylum Actinobacteria, were found to be the dominant bacteria in the soils around the Great Wall Station. Although the selected samples were not contaminated by oil, a relationship between soil parameters, microbial biodiversity, and human impact was still seen. Sample sites in human impacted areas showed lower bacterial biodiversity (average H' = 2.65) when compared to non-impacted sites (average H' = 3.05). There was no statistically significant correlation between soil bacterial diversity and total organic carbon (TOC), total nitrogen, or total phosphorus contents of the soil. Canonical correlation analysis showed that TOC content was the most important factor determining bacterial community profiles among the measured soil parameters. In conclusion, microbial biodiversity and community characteristics within relatively small scales (1.5 km) were determined as a function of local environment parameters and anthropogenic impact.

  12. Denaturing gradient gel electrophoresis fingerprinting of soil bacteria in the vicinity of the Chinese Great Wall Station, King George Island, Antarctica

    Institute of Scientific and Technical Information of China (English)

    Qi Pan; Feng Wang; Yang Zhang; Minghong Cai; Jianfeng He; Haizhen Yang

    2013-01-01

    Bacterial diversity was investigated in soil samples collected from 13 sites around the Great Wall Station,Fildes Peninsula,King George Island,Antarctica,using denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes.The classes α-,β-,and γ-Proteobacteria,as well as the phylum Actinobacteria,were found to be the dominant bacteria in the soils around the Great Wall Station.Although the selected samples were not contaminated by oil,a relationship between soil parameters,microbial biodiversity,and human impact was still seen.Sample sites in human impacted areas showed lower bacterial biodiversity (average H' =2.65) when compared to non-impacted sites (average H' =3.05).There was no statistically significant correlation between soil bacterial diversity and total organic carbon (TOC),total nitrogen,or total phosphorus contents of the soil.Canonical correlation analysis showed that TOC content was the most important factor determining bacterial community profiles among the measured soil parameters.In conclusion,microbial biodiversity and community characteristics within relatively small scales (1.5 km) were determined as a function of local environment parameters and anthropogenic impact.

  13. Distribution and characteristics of marine habitats in a subpolar bay based on hydroacoustics and bed shear stress estimates—Potter Cove, King George Island, Antarctica

    Science.gov (United States)

    Wölfl, Anne-Cathrin; Lim, Chai Heng; Hass, H. Christian; Lindhorst, Sebastian; Tosonotto, Gabriela; Lettmann, Karsten Alexander; Kuhn, Gerhard; Wolff, Jörg-Olaf; Abele, Doris

    2014-10-01

    Marine habitats worldwide are increasingly pressurized by climate change, especially along the Antarctic Peninsula. Well-studied areas in front of rapidly retreating tidewater glaciers like Potter Cove are representative for similar coastal environments and, therefore, shed light on habitat formation and development on not only a local but also regional scale. The objective of this study was to provide insights into habitat distribution in Potter Cove, King George Island, Antarctica, and to evaluate the associated environmental processes. Furthermore, an assessment concerning the future development of the habitats is provided. To describe the seafloor habitats in Potter Cove, an acoustic seabed discrimination system (RoxAnn) was used in combination with underwater video images and sediment samples. Due to the absence of wave and current measurements in the study area, bed shear stress estimates served to delineate zones prone to sediment erosion. On the basis of the investigations, two habitat classes were identified in Potter Cove, namely soft-sediment and stone habitats that, besides influences from sediment supply and coastal morphology, are controlled by sediment erosion. A future expansion of the stone habitat is predicted if recent environmental change trends continue. Possible implications for the Potter Cove environment, and other coastal ecosystems under similar pressure, include changes in biomass and species composition.

  14. Weddellian marine/coastal vertebrates diversity from a basal horizon (Ypresian, Eocene of the Cucullaea I Allomember, La Meseta formation, Seymour (Marambio Island, Antarctica

    Directory of Open Access Journals (Sweden)

    Marcelo A. Reguero

    2013-06-01

    Full Text Available The La Meseta Formation crops out in Seymour/Marambio Island, Weddell Sea, northeast of the Antarctic Peninsula and contains one of the world's most diverse assemblages of Weddellian marine/coastal verte-brates of Early Eocene (Ypresian age. The La Meseta Formation is composed of poorly consolidated, marine sandstones and siltstones which were deposited in a coastal, deltaic and/or estuarine environment. It includes marine invertebrates and vertebrates as well as terrestrial vertebrates and plants. The highly fossiliferous basal horizon (Cucullaeashell bed, Telm 4 of Sadler 1988 of the CucullaeaI Allomember is a laterally extensive shell bed with sandy matrix. The fish remains, including 35 species from 26 families, of the Ypresian Cucullaeabed represent one of the most abundant and diverse fossil vertebrate faunas yet recorded in southern latitudes. Stratigraphic distribution and phylogenetic relationships of the Weddellian sphenisciforms are consistent with a first radiation of this group in the Early Eocene. The first inquestionable archaeocete from Antarctica is recorded in this unit and is referred to a new taxon.

  15. Identity and physiology of a new psychrophilic eukaryotic green alga, Chlorella sp., strain BI, isolated from a transitory pond near Bratina Island, Antarctica

    Science.gov (United States)

    Morgan-Kiss, R. M.; Ivanov, A.G.; Modla, S.; Czymmek, K.; Huner, N.P.A.; Priscu, J.C.; Lisle, J.T.; Hanson, T.E.

    2008-01-01

    Permanently low temperature environments are one of the most abundant microbial habitats on earth. As in most ecosystems, photosynthetic organisms drive primary production in low temperature food webs. Many of these phototrophic microorganisms are psychrophilic; however, functioning of the photosynthetic processes of these enigmatic psychrophiles (the 'photopsychrophiles') in cold environments is not well understood. Here we describe a new chlorophyte isolated from a low temperature pond, on the Ross Ice Shelf near Bratina Island, Antarctica. Phylogenetic and morphological analyses place this strain in the Chlorella clade, and we have named this new chlorophyte Chlorella BI. Chlorella BI is a psychrophilic species, exhibiting optimum temperature for growth at around 10??C. However, psychrophily in the Antarctic Chlorella was not linked to high levels of membrane-associated poly-unsaturated fatty acids. Unlike the model Antarctic lake alga, Chlamydomonas raudensis UWO241, Chlorella BI has retained the ability for dynamic short term adjustment of light energy distribution between photosystem II (PS II) and photosystem I (PS I). In addition, Chlorella BI can grow under a variety of trophic modes, including heterotrophic growth in the dark. Thus, this newly isolated photopsychrophile has retained a higher versatility in response to environmental change than other well studied cold-adapted chlorophytes. ?? 2008 Springer.

  16. Two-stage rifting of Zealandia-Australia-Antarctica: Evidence from 40Ar/39Ar thermochronometry of the Sisters shear zone, Stewart Island, New Zealand

    Science.gov (United States)

    Kula, Joseph; Tulloch, Andy; Spell, Terry L.; Wells, Michael L.

    2007-05-01

    The Sisters shear zone is a newly discovered Late Cretaceous detachment fault system exposed for 40 km along the southeast coast of Stewart Island, southernmost New Zealand. Footwall rocks consist of variably deformed ca. 310 and 105 Ma granites that range from undeformed to protomylonite, mylonite, and ultramylonite. The hanging wall includes non-marine conglomerate and brittley deformed granite. K-feldspar thermochronometry of the footwall indicates moderately rapid cooling (20 30 C°/m.y.) due to tectonic denudation over the interval ca. 89 82 Ma. Return to slow cooling at 82 Ma coincides with the age of the oldest seafloor adjacent to the Campbell Plateau and reflects the mechanical transition from continental extension to lithospheric rupture and formation of the Pacific-Antarctic Ridge. Our findings support a two-stage rift model for continental breakup of this part of the Gondwana margin. Stage one (ca. 101 88 Ma) is the northward propagation of continental extension and the Tasman Ridge as recorded in mylonite dredged from the Ross Sea and the Paparoa core complex. Stage two (ca. 89 82 Ma) is extension between the Campbell Plateau and West Antarctica leading to formation of the Pacific-Antarctic Ridge.

  17. COMPILATION OF GEOMORPHOLOGICAL MAP FOR RECONSTRUCTING THE DEGLACIATION OF ICE-FREE AREAS IN THE MARTEL INLET, KING GEORGE ISLAND, ANTARCTICA

    Directory of Open Access Journals (Sweden)

    Kátia Kellem Rosa

    2014-03-01

    Full Text Available We compiled a geomorphological map and a reconstruction map of glacier extension and ice-free areas in the Martel Inlet, located in King George Island, South Shetlands, Antarctica. Glacier extension data were derived of the digitized over a orthophotomosaic (2003, SPOT (February, 1988; March, 1995 and 2000, Quickbird (October, 2006 and Cosmo-Skymed (February, 2011 images. This mapping was supported by fieldworks carried out in the summers of 2007, 2010 and 2011, and by topographic surveys and geomorphic map in the proglacial area. Several types of glacial deposits were identified in the study area, such as frontal and lateral moraines, flutes, meltwater channels and erosional features like rock moutonnés, striations and U-shaped valleys. These features allowed reconstructing the evolution of the deglaciation environment in the Martel Inlet ice-free areas, which has been affected by a regional climate warming trend. The mapped data indicated the glaciers in study area lost about 0.71 km² of their ice masses (13.2% of the 50.3 km² total area, without any advances during 1979-2011. Since those years these glaciers receded by an average of 25.9 m a-1. These ice-free areas were susceptible to rapid post-depositional changes.

  18. Unglaciated areas in East Antarctica during the Last Glacial (Marine Isotope Stage 3) - New evidence from Rauer Group

    Science.gov (United States)

    Berg, Sonja; White, Duanne A.; Bennike, Ole; Fülöp, Réka-H.; Fink, David; Wagner, Bernd; Melles, Martin

    2016-12-01

    Limited information on the East Antarctic Ice Sheet (EAIS) geometry during Marine Isotope Stage 3 (MIS 3; 60-25 ka) restricts our understanding of its behaviour during periods of climate and sea level change. Ice sheet models forced by global parameters suggest an expanded EAIS compared to the Holocene during MIS 3, but field evidence from East Antarctic coastal areas contradicts such modelling, and suggests that the ice sheet margins were no more advanced than at present. Here we present a new lake sediment record, and cosmogenic exposure results from bedrock, which confirm that Rauer Group (eastern Prydz Bay) was ice-free for much of MIS 3. We also refine the likely duration of the Last Glacial Maximum (LGM) glaciation in the region. Lacustrine and marine sediments from Rauer Group indicate the penultimate period of ice retreat predates 50 ka. The lacustrine record indicates a change from warmer/wetter conditions to cooler/drier conditions after ca. 35 ka. Substantive ice sheet re-advance, however, may not have occurred until much closer to 20 ka. Contemporary coastal areas were still connected to the sea during MIS 3, restricting the possible extent of grounded ice in Prydz Bay on the continental shelf. In contrast, relative sea levels (RSL) deduced from field evidence indicate an extra ice load averaging several hundred metres thicker ice across the Bay between 45 and 32 ka. Thus, ice must either have been thicker immediately inland (with a steeper ice profile), or there were additional ice domes on the shallow banks of the outer continental shelf. Further work is required to reconcile the differences between empirical evidence of past ice sheet histories, and the history predicted by ice sheet models from far-field temperature and sea level records.

  19. 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- (large- (>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 <100 m in diameter, a regime shift which appeared at 20-40 m in the MIZ is absent. These results indicate that one role of wave-ice interaction is to modulate the FSD that already exists in the interior ice region, rather than directly determine it. The possibilities of floe-floe collisions and storm-induced lead formation are considered as possible formation processes of FSD in the interior pack.

  20. 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.

  1. Petrology and SHRIMP zircon geochronology of granulites from Vesleknausen, Lützow-Holm Complex, East Antarctica:Neoarchean magmatism and Neoproterozoic high-grade metamorphism

    Institute of Scientific and Technical Information of China (English)

    Toshiaki Tsunogae; Daniel J. Dunkley; Kenji Horie; Takahiro Endo; Tomoharu Miyamoto; Mutsumi Kato

    2014-01-01

    We report new petrological data and geochronological measurements of granulites from Vesleknausen in the highest-grade section of the Lützow-Holm Complex, part of the Gondwana-assembling collisional orogen in East Antarctica. The locality is dominated by felsic to intermediate orthogneiss (charnockite and minor biotite gneiss), mafic orthogneiss, and hornblende-pyroxene granulite, with deformed and undeformed dykes of metagranite and felsic pegmatite. Pseudosection analysis of charnockite in the system NCKFMASHTO, supported by geothermometry of mafic orthogneiss, was used to infer peak metamorphic temperatures of 750e850 ?C, approximately 150 ?C lower than those estimated for met-asedimentary gneisses from Rundvågshetta, 6 km to the northeast. SHRIMP U-Pb analysis of zircons from feldspar-pyroxene gneiss, which corresponds to a partially molten patch around mafic orthogneiss, yielded a Concordia upper intercept ages of 2507.9 ? 7.4 Ma, corresponding to the time of formation of the magmatic protolith to the orthogneiss. Partial melting during peak metamorphism probably took place between 591 and 548 Ma, as recorded in rims overgrew around magmatic zircon. Our results suggest that Rundvågshetta-Vesleknausen-Strandnibba region in southwestern Lützow-Holm Bay, where orthogneisses are dominant, consists of a single crustal block, possibly formed by ca. 2.5 Ga arc mag-matism. The Neoarchean magmatic terrane was tectonically mingled with other fragments (such as metasedimentary units in northern Lützow-Holm Bay) by subduction/collision events during the as-sembly of Gondwana supercontinent, and subsequently underwent w850 ?C granulite-facies meta-morphosed during Neoproterozoic to Cambrian final collisional event.

  2. Petrology and SHRIMP zircon geochronology of granulites from Vesleknausen, Lützow-Holm Complex, East Antarctica: Neoarchean magmatism and Neoproterozoic high-grade metamorphism

    Directory of Open Access Journals (Sweden)

    Toshiaki Tsunogae

    2014-03-01

    Full Text Available We report new petrological data and geochronological measurements of granulites from Vesleknausen in the highest-grade section of the Lützow-Holm Complex, part of the Gondwana-assembling collisional orogen in East Antarctica. The locality is dominated by felsic to intermediate orthogneiss (charnockite and minor biotite gneiss, mafic orthogneiss, and hornblende-pyroxene granulite, with deformed and undeformed dykes of metagranite and felsic pegmatite. Pseudosection analysis of charnockite in the system NCKFMASHTO, supported by geothermometry of mafic orthogneiss, was used to infer peak metamorphic temperatures of 750–850 °C, approximately 150 °C lower than those estimated for metasedimentary gneisses from Rundvågshetta, 6 km to the northeast. SHRIMP U-Pb analysis of zircons from feldspar-pyroxene gneiss, which corresponds to a partially molten patch around mafic orthogneiss, yielded a Concordia upper intercept ages of 2507.9 ± 7.4 Ma, corresponding to the time of formation of the magmatic protolith to the orthogneiss. Partial melting during peak metamorphism probably took place between 591 and 548 Ma, as recorded in rims overgrew around magmatic zircon. Our results suggest that Rundvågshetta-Vesleknausen-Strandnibba region in southwestern Lützow-Holm Bay, where orthogneisses are dominant, consists of a single crustal block, possibly formed by ca. 2.5 Ga arc magmatism. The Neoarchean magmatic terrane was tectonically mingled with other fragments (such as metasedimentary units in northern Lützow-Holm Bay by subduction/collision events during the assembly of Gondwana supercontinent, and subsequently underwent ∼850 °C granulite-facies metamorphosed during Neoproterozoic to Cambrian final collisional event.

  3. An independently dated 2000-yr volcanic record from Law Dome, East Antarctica, including a new perspective on the dating of the 1450s CE eruption of Kuwae, Vanuatu

    Directory of Open Access Journals (Sweden)

    C. T. Plummer

    2012-11-01

    Full Text Available Volcanic eruptions are an important cause of natural climate variability. In order to improve the accuracy of climate models, precise dating and magnitude of the climatic effects of past volcanism are necessary. Here we present a 2000-yr record of Southern Hemisphere volcanism recorded in ice cores from the high accumulation Law Dome site, East Antarctica. The ice cores were analysed for a suite of chemistry signals and are independently dated via annual layer counting, with 11 ambiguous years at 23 BCE, which has presently the lowest error of all published long Antarctic ice cores. Independently dated records are important to avoid circular dating where volcanic signatures are assigned a date from some external information rather than using the date it is found in the ice core. Forty-five volcanic events have been identified using the sulphate chemistry of the Law Dome record. The low dating error and comparison with the NGRIP (North Greenland Ice Core Project volcanic records (on the GICC05 timescale suggest Law Dome is the most accurately dated Antarctic volcanic dataset, which will improve the dating of individual volcanic events and potentially allow better correlation between ice core records, leading to improvements in global volcanic forcing datasets. One of the most important volcanic events of the last two millennia is the large 1450s CE event, usually assigned to the eruption of Kuwae, Vanuatu. In this study, we review the evidence surrounding the presently accepted date for this event, and make the case that two separate eruptions have caused confusion in the assignment of this event. Volcanic sulphate deposition estimates are important for modelling the climatic response to eruptions. The largest volcanic sulphate events in our record are dated at 1458 CE (Kuwae?, Vanuatu, 1257 and 422 CE (unidentified.

  4. Condition of larval (furcilia VI) and one year old juvenile Euphausia superba during the winter-spring transition in East Antarctica

    Science.gov (United States)

    Virtue, Patti; Meyer, Bettina; Freier, Ulrich; Nichols, Peter D.; Jia, Zhongnan; King, Rob; Virtue, Jacob; Swadling, Kerrie M.; Meiners, Klaus M.; Kawaguchi, So

    2016-09-01

    Antarctic krill, Euphausia superba, is an important species in the Southern Ocean ecosystem. Information on krill condition during winter and early spring is slowly evolving with our enhanced ability to sample at this time of year. However, because of the limited spatial and temporal data, our understanding of fundamental biological parameters for krill during winter is limited. Our study assessed the condition of larval (furcilia VI) and one year old juvenile krill collected in East Antarctica (115°E-130°E and 64°S-66°S) from September to October 2012. Krill condition was assessed using morphometric, elemental and biochemical body composition, growth rates, oxygen uptake and lipid content and composition. Diet was assessed using fatty acid biomarkers analysed in the krill. The growth rate of larvae was 0.0038 mm day with an inter-moult period of 14 days. The average oxygen uptake of juvenile krill was 0.30±0.02 μl oxygen consumed per mg dry weight per hour. Although protein was not significantly different amongst the krill analysed, the lipid content of krill was highly variable ranging from 9% to 27% dry weight in juveniles and from 4% to 13% dry weight in larvae. Specific algal biomarkers, fatty acids ratios, levels of both long-chain (≥C20) monounsaturated fatty acids and bacterial fatty acids found in krill were indicative of the mixed nature of dietary sources and the opportunistic feeding capability of larval and juvenile krill at the end of winter.

  5. 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

    2011-02-01

    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.

  6. 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.

  7. Tsunami generation in Stromboli island and impact on the south-east Tyrrhenian coasts

    Directory of Open Access Journals (Sweden)

    S. Tinti

    2003-01-01

    Full Text Available Stromboli is one of the most active volcanoes in the Aeolian island arc in south Tyrrhenian sea, Italy. In the last 100 years the most relevant volcanic eruptions have beenaccompanied by local tsunamis, that have caused damage and casualties. In some cases the direct mechanism of local tsunami generation is clear, i.e. pyroclastic flows entering the sea. In some others it is uncertain and some speculation concerning the collapse of the eruptive column on the sea surface or the failure of some underwater mass can be made. But the ordinary activity is unlikely to generate large regional tsunamis. These can be produced by the lateral collapse of the volcanic cone that geomorphological and volcanological  investigations have proven to have occurred repeatedly in the recent history of the volcano, with return period in the order of some thousands of years. The last episode is dated to less than 5 ka BP, and left the Sciara del Fuoco scar on the north-west flank of Stromboli. Based on previous studies, the possible collapse of the nortwestern sector of Stromboli and the consequent generation and propagation of a tsunami are explored. The impact on Stromboli and on the other islands of the Aeolian archipelago is estimated, as well as the impact on the coast of Sicily and the Tyrrhenian coasts of Calabria. The simulation is carried out by means of a double model: a Lagrangian block model to compute the motion of the collapsing mass, and a finite-element hydrodynamic model to compute the evolution of the tsunami. Two distinct tsunami simulations are carried out, one on a very fine grid around the source region to evaluate the tsunami near Stromboli, and one utilising a coarser grid covering the whole south-east Tyrrhenian sea to compute the tsunami propagation toward Sicily and Calabria. It is found that a huge-volume collapse of the north-western flank of the Stromboli cone is capable of producing a regional tsunami which is catastrophic at the source

  8. Archive of side scan sonar and swath bathymetry data collected during USGS cruise 10CCT03 offshore of the Gulf Islands National Seashore, Mississippi, from East Ship Island, Mississippi, to Dauphin Island, Alabama, April 2010

    Science.gov (United States)

    DeWitt, Nancy T.; Flocks, James G.; Pfeiffer, William R.; Gibson, James N.; Wiese, Dana S.

    2012-01-01

    In April of 2010, the U.S. Geological Survey (USGS) conducted a geophysical survey from the east end of East Ship Island, Miss., extending to the middle of Dauphin Island, Ala. (fig. 1). This survey had a dual purpose: (1) to interlink previously conducted nearshore geophysical surveys (shoreline to ~2 km) with those of offshore surveys (~2 to ~9 km) in the area, and (2) to extend the geophysical survey to include a portion of the Dauphin Island nearshore zone. The efforts were part of the USGS Gulf of Mexico Science Coordination partnership with the U.S. Army Corps of Engineers (USACE) to assist the Mississippi Coastal Improvements Program (MsCIP) and the Northern Gulf of Mexico (NGOM) Ecosystem Change and Hazards Susceptibility Project by mapping the shallow geological stratigraphic framework of the Mississippi Barrier Island Complex. These geophysical surveys will provide the data necessary for scientists to define, interpret, and provide baseline bathymetry and seafloor habitat for this area and to aid scientists in predicting future geomorpholocial changes of the islands with respect to climate change, storm impact, and sea-level rise. Furthermore, these data will provide information for barrier island restoration feasibility, particularly in Camille Cut, and efforts for the preservation of historical Fort Massachusetts. For more information refer to http://ngom.usgs.gov/gomsc/mscip/.

  9. Spatiotemporal variability of sedimentology and morphology in the East Frisian barrier island system

    Science.gov (United States)

    Herrling, Gerald; Winter, Christian

    2016-08-01

    The highly dynamic East Frisian barrier island system (southern North Sea) is characterized by a complex morphology of tidal inlets, ebb-tidal deltas and foreshore beaches that reacts to storms and fair-weather conditions with characteristic patterns of sediment grain-size distributions. The morphological and sedimentological response to varying hydrodynamic conditions yet occurs in short time spans that are not covered by common monitoring strategies with measuring intervals typically of years. This study applies process-based numerical modelling with multiple sediment fractions to interpolate morphological states in time between bathymetrical surveys conducted in the summer months of 2004 and 2006. Morphodynamic simulations driven by real-time boundary conditions of tides, wind and waves are carried out for a representative period of 2 years. The spatiotemporal variability of the nearshore sedimentology and morphology is assessed by graded ranges of bed dynamics (i.e. bed elevation range) and the definition of sediment grain-size variability (i.e. mean diameter range). The effect of storm events and timescales of the sedimentological adaptation after storms to typical fair-weather conditions are exemplified at an ebb-tidal delta lobe where the morphological and sedimentological variability is found to be largest in the study area. The proposed method may serve to identify areas of high sedimentological and morphological activity for system understanding or in the framework of coastal monitoring strategies.

  10. Dinophysis caudata generated lipophilic shellfish toxins in bivalves from the Nanji Islands, East China Sea

    Science.gov (United States)

    Jiang, Tao; Xu, Yixiao; Li, Yang; Qi, Yuzao; Jiang, Tianjiu; Wu, Feng; Zhang, Fan

    2014-01-01

    A 12-month program of monitoring potentially toxic microalgae (that produce lipophilic shellfish toxins; LSTs) and their toxins in bivalves was conducted from April 2006 to March 2007 in the Nanji Islands, East China Sea. Two Dinophysis species, D. caudata and D. acuminata, were identified, and D. caudata was found to be the dominant species. D. caudata was detected in water samples between April and June 2006, and between February and March 2007. It reached its highest abundances in May, with a mean abundance of 1.38×102 cells/L in surface water and 1.25×102 cells/L in bottom water (cultured bivalves sampled between April and June were contaminated with LSTs, with an average toxicity of 85 μg okadaic acid (OA) eq./100 g meat, which was four times higher than the Chinese regulatory limit (20 μg OA eq./100 g meat). Ten out of fifteen wild samples (66.7%) collected during the same period were positive for LSTs, and contained an average LST toxicity of 45 μg OA eq./100 g meat (more than twice the regulatory value). Cultured Patinopecten yessoensis collected on 15 May 2006 had the highest toxicity, 320 μg OA eq./100 g meat, and relatively high toxicities (80 to 160 μg OA eq./100 g meat) were found in bivalves until the end of July.

  11. Origin of Mineral Springs on the East Coast, North Island, NZ

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, T.M.; Glover, R.B.

    1995-01-01

    Strongly mineralized waters emerge as warm and cold springs from parts of a Cenozoic accretionary prism which extends along the East Coast of the North Island. The chemistry of these waters is consistent with them having been derived from connate sea water in deeply-buried marine sediments and is distinct from springs in other parts of the prism and elsewhere in New Zealand. Most of these mineral springs are associated with three, long-wavelength, magnetic anomalies which modeling suggests are caused by deeply-buried ophiolite bodies within the prism or by seamounts on the top of the subducted Pacific Plate underlying the prism. It is postulated that these deep-seated bodies have facilitated the dewatering of marine sediments from deep within the prism or from the subducted plate. This ''devolved sea water'' has then risen, been modified by contact with overlying sediments and mixed with near-surface meteoric waters, before emerging at the mineral springs.

  12. Potential changes in feeding behavior of Antarctic fish, Pseudotrematomus bernacchii (Boulenger, 1902) on the East Ongul Island, Antarctica

    Science.gov (United States)

    Chavanich, Suchana; Viyakarn, Voranop; Nomura, Daiki; Watanabe, Kentaro

    2015-12-01

    The feeding habits of the Antarctic fish Pseudotrematomus bernacchii (Previous name: Trematomus bernacchii) under the fast ice around Japanese Syowa Station were investigated in the summers of 2004/2005 and 2009/2010. The results showed that amphipods and krill were the major prey. However, there was a significant difference in the proportions of larger invertebrates such as squids, octopus and other crustaceans found in the fish stomachs between 2009/2010 and the previous years. Moreover, the percentage of amphipods and krill in fish stomachs declined over the 5-year period in all fish size classes. Several factors including sea ice melting, habitat and environmental changes might have influenced the pattern of feeding behavior.

  13. A precise monitoring of snow surface height in the region of Lambert Glacier basin-Amery Ice Shelf, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    XIAO Cunde; QIN Dahe; BIAN Lingen; ZHOU Xiuji; I. Allison; YAN Ming

    2005-01-01

    The net surface snow accumulation on the Antarctic ice sheet is determined by a combination of precipitation, sublimation and wind redistribution. We present a one-year record of hourly snow-height measurements at LGB69 (70°50'S, 77°04(E,1850 m a.s.l.), east side of Lambert Glacier basin (LGB), and 4 year record at G3 (70°53'S, 69°52'E, 84 m a.s.l.), Amery Ice Shelf (AIS). The measurements were made with ultrasonic sensors mounted on automatic weather stations installed at two sites. The snow accumulation at LGB69 is approximately 70 cm. Throughout the winter, between April and September, there was little change in surface snow height (SSH) at the two sites. The negative SSH change is due to densification at LGB69, and is due to both ablation and densification at G3. The strongest accumulation at two sites occurred during the period between Octobers and March (accounting for 101.6% at LGB69), with four episodic increasing events occurring during 2002 for LGB69, and eight events during 1999-2002 for G3 (2 to 3 events per year). At LGB69, these episodic events coincided with obvious humidity "pulses" and decreases of incoming solar radiation as recorded by the AWS. Observations of the total cloud amount at Davis station, 160 km NNE of LGB69, showed good correlation with major accumulation events recorded at LGB69. There was an obvious anti-correlation between the lowest cloud height at Davis and the daily accumulation rate at LGB69. Although there was no correlation over the total year between wind speed and accumulation at LGB69, large individual accumulation events are associated with episodes of strong wind (>7 m/s), we estimate drift snow may contribute to total SSH up to 35%. Strong accumulation events at LGB69 are associated with major storms in the region and inland transport of moist air masses from the coast.

  14. Factors controlling the geochemical composition of Limnopolar lake sediments (Byers Peninsula, South Shetland Island, Livingston Island, Antarctica during the last ∼ 1600 years

    Directory of Open Access Journals (Sweden)

    A. Martínez Cortizas

    2014-03-01

    Full Text Available We sampled a short (57 cm sediment core in Limnopolar Lake (Byers Peninsula, Livingston Island, South Shetlands Islands, which spans the last ~ 1600 years. The core was sectioned at high resolution and analyzed for elemental and mineralogical composition, and SEM-EDS analysis of glass mineral particles in selected samples. The chemical record was characterized by a contrasted pattern of layers with high Ca, Ti, Zr, and Sr concentrations and layers with higher concentrations of K and Rb. The first also enriched in plagioclase and, occasionally, in zeolites, while the later were relatively enriched in 2:1 phyllosilicates and quartz. This was interpreted as reflecting the abundance of volcaniclastic material (Ca-rich vs. Jurassic-Lower Cretaceous marine sediments (K-rich – the dominant geological material in the lake catchment. SEM-EDS analysis revealed the presence of abundant volcanic shards in the Ca-rich layers, pointing to tephras most probably related to the activity of Deception Island volcano (located 30 km to the SE. The ages of the four main peaks of volcanic-rich material (AD ~ 1840–1860 for L1, AD ~ 1570–1650 for L2, AD ~ 1450–1470 for L3, and AD ~ 1300 for L4 matched reasonably well the age of tephra layers (AP1 to AP3 previously identified in lakes of Byers Peninsula. Some of the analyzed metals (Fe, Mn, Cu and Cr showed enrichments in the most recent tephra layer (L1, suggesting relative changes in the composition of the tephras as found in previous investigations. No evidence of significant human impact on the cycles of most trace metals (Cu, Zn, Pb was found, probably due to the remote location of Livingston Island and the modest research infrastructures – local contamination was found by other researchers in soils, waters and marine sediments on areas with large, permanent, research stations. Chromium is the only metal showing a steady enrichment in the last 200 years that could be interpreted as recent anthropogenic

  15. Factors controlling the geochemical composition of Limnopolar lake sediments (Byers Peninsula, South Shetland Island, Livingston Island, Antarctica) during the last ˜ 1600 years

    Science.gov (United States)

    Martínez Cortizas, A.; Rozas Muñiz, I.; Taboada, T.; Toro, M.; Granados, I.; Giralt, S.; Pla-Rabés, S.

    2014-03-01

    We sampled a short (57 cm) sediment core in Limnopolar Lake (Byers Peninsula, Livingston Island, South Shetlands Islands), which spans the last ~ 1600 years. The core was sectioned at high resolution and analyzed for elemental and mineralogical composition, and SEM-EDS analysis of glass mineral particles in selected samples. The chemical record was characterized by a contrasted pattern of layers with high Ca, Ti, Zr, and Sr concentrations and layers with higher concentrations of K and Rb. The first also enriched in plagioclase and, occasionally, in zeolites, while the later were relatively enriched in 2:1 phyllosilicates and quartz. This was interpreted as reflecting the abundance of volcaniclastic material (Ca-rich) vs. Jurassic-Lower Cretaceous marine sediments (K-rich) - the dominant geological material in the lake catchment. SEM-EDS analysis revealed the presence of abundant volcanic shards in the Ca-rich layers, pointing to tephras most probably related to the activity of Deception Island volcano (located 30 km to the SE). The ages of the four main peaks of volcanic-rich material (AD ~ 1840-1860 for L1, AD ~ 1570-1650 for L2, AD ~ 1450-1470 for L3, and AD ~ 1300 for L4) matched reasonably well the age of tephra layers (AP1 to AP3) previously identified in lakes of Byers Peninsula. Some of the analyzed metals (Fe, Mn, Cu and Cr) showed enrichments in the most recent tephra layer (L1), suggesting relative changes in the composition of the tephras as found in previous investigations. No evidence of significant human impact on the cycles of most trace metals (Cu, Zn, Pb) was found, probably due to the remote location of Livingston Island and the modest research infrastructures - local contamination was found by other researchers in soils, waters and marine sediments on areas with large, permanent, research stations. Chromium is the only metal showing a steady enrichment in the last 200 years that could be interpreted as recent anthropogenic contamination. At the

  16. New insights into submarine geomorphology and depositional processes along the George V Land continental slope and upper rise (East Antarctica)

    Science.gov (United States)

    de Santis, Laura

    2010-05-01

    Swath bathymetry collected by the Italian Antarctic Program (PNRA), in the offshore of the George Vth Land, document evidence of cascading, cold and dense bottom currents, inside continental slope canyons, and suggest an active role of the sea floor morphology on modern and ancient process. The continental slope is incised by canyons locally heading to the shelf edge and bounding sedimentary ridges of Miocene age(ref1,2). Erosion by bottom water masses, up to present times, exhumed or prevented the burial of such relict sedimentary ridges originated by glacial processes. Dense shelf water is formed by coastal polynyas and is exported over the shelf break to produce Antarctic Bottom Water (AABW)(ref3,4). This locally formed AABW (often referred to as Adélie Land Bottom Water) is detected by CTD and mooring measurements up to about 3200 m of depth, in the Jussieu canyon and further to the west(ref5). The speed of the ALBW is enough to transport fine sand and silt from shallow to deep water. Evidence for exporting sediment off the shelf via bottom water, through the Holocene, is inferred by sedimentological and geophysical studies(ref6,7). Morphologic and geological data in the slope and rise confirm that the Jussieu canyon is a main conduit of high energetic bottom current, in present times as well as in the past(ref1,7). Coarse grain material and turbidites (up to 1 meter thick) were sampled from the canyon levees at 2500 and 3000 meters of water depth(ref1). At a depth of 2600 m, the Jussieu canyon converges with two canyons into a single branch, showing a meandering trend, up to about 3200 m of water depth. The asymmetry of the meandering section and the internal geometry of its levees are typical expressions of differential erosion and deposition from downslope flows. Sediment waves characterise the western flank of the Wega Channel, at depth of 2400-2800 meters, to the east of the Jussieu canyon(ref1). The waves are composed by fine grained sediments whose

  17. Petrology, geochemistry and zircon U-Pb geochronology of a layered igneous complex from Akarui Point in the Lützow-Holm Complex, East Antarctica: Implications for Antarctica-Sri Lanka correlation

    Science.gov (United States)

    Kazami, Sou; Tsunogae, Toshiaki; Santosh, M.; Tsutsumi, Yukiyasu; Takamura, Yusuke

    2016-11-01

    The Lützow-Holm Complex (LHC) of East Antarctica forms part of a complex subduction-collision orogen related to the amalgamation of the Neoproterozoic supercontinent Gondwana. Here we report new petrological, geochemical, and geochronological data from a metamorphosed and disrupted layered igneous complex from Akarui Point in the LHC which provide new insights into the evolution of the complex. The complex is composed of mafic orthogneiss (edenite/pargasite + plagioclase ± clinopyroxene ± orthopyroxene ± spinel ± sapphirine ± K-feldspar), meta-ultramafic rock (pargasite + olivine + spinel + orthopyroxene), and felsic orthogneiss (plagioclase + quartz + pargasite + biotite ± garnet). The rocks show obvious compositional layering reflecting the chemical variation possibly through magmatic differentiation. The metamorphic conditions of the rocks were estimated using hornblende-plagioclase geothermometry which yielded temperatures of 720-840 °C. The geochemical data of the orthogneisses indicate fractional crystallization possibly related to differentiation within a magma chamber. Most of the mafic-ultramafic samples show enrichment of LILE, negative Nb, Ta, P and Ti anomalies, and constant HFSE contents in primitive-mantle normalized trace element plots suggesting volcanic arc affinity probably related to subduction. The enrichment of LREE and flat HREE patterns in chondrite-normalized REE plot, with the Nb-Zr-Y, Y-La-Nb, and Th/Yb-Nb/Yb plots also suggest volcanic arc affinity. The felsic orthogneiss plotted on Nb/Zr-Zr diagram (low Nb/Zr ratio) and spider diagrams (enrichment of LILE, negative Nb, Ta, P and Ti anomalies) also show magmatic arc origin. The morphology, internal structure, and high Th/U ratio of zircon grains in felsic orthogneiss are consistent with magmatic origin for most of these grains. Zircon U-Pb analyses suggest Early Neoproterozoic (847.4 ± 8.0 Ma) magmatism and protolith formation. Some older grains (1026-882 Ma) are regarded as

  18. Up, Down, and All Around: Scale-Dependent Spatial Variation in Rocky-Shore Communities of Fildes Peninsula, King George Island, Antarctica

    Science.gov (United States)

    Valdivia, Nelson; Díaz, María J.; Holtheuer, Jorge; Garrido, Ignacio; Huovinen, Pirjo; Gómez, Iván

    2014-01-01

    Understanding the variation of biodiversity along environmental gradients and multiple spatial scales is relevant for theoretical and management purposes. Hereby, we analysed the spatial variability in diversity and structure of intertidal and subtidal macrobenthic Antarctic communities along vertical environmental stress gradients and across multiple horizontal spatial scales. Since biotic interactions and local topographic features are likely major factors for coastal assemblages, we tested the hypothesis that fine-scale processes influence the effects of the vertical environmental stress gradients on the macrobenthic diversity and structure. We used nested sampling designs in the intertidal and subtidal habitats, including horizontal spatial scales ranging from few centimetres to 1000s of metres along the rocky shore of Fildes Peninsula, King George Island. In both intertidal and subtidal habitats, univariate and multivariate analyses showed a marked vertical zonation in taxon richness and community structure. These patterns depended on the horizontal spatial scale of observation, as all analyses showed a significant interaction between height (or depth) and the finer spatial scale analysed. Variance and pseudo-variance components supported our prediction for taxon richness, community structure, and the abundance of dominant species such as the filamentous green alga Urospora penicilliformis (intertidal), the herbivore Nacella concinna (intertidal), the large kelp-like Himantothallus grandifolius (subtidal), and the red crustose red alga Lithothamnion spp. (subtidal). We suggest that in coastal ecosystems strongly governed by physical factors, fine-scale processes (e.g. biotic interactions and refugia availability) are still relevant for the structuring and maintenance of the local communities. The spatial patterns found in this study serve as a necessary benchmark to understand the dynamics and adaptation of natural assemblages in response to observed and

  19. Up, down, and all around: scale-dependent spatial variation in rocky-shore communities of Fildes Peninsula, King George Island, Antarctica.

    Directory of Open Access Journals (Sweden)

    Nelson Valdivia

    Full Text Available Understanding the variation of biodiversity along environmental gradients and multiple spatial scales is relevant for theoretical and management purposes. Hereby, we analysed the spatial variability in diversity and structure of intertidal and subtidal macrobenthic Antarctic communities along vertical environmental stress gradients and across multiple horizontal spatial scales. Since biotic interactions and local topographic features are likely major factors for coastal assemblages, we tested the hypothesis that fine-scale processes influence the effects of the vertical environmental stress gradients on the macrobenthic diversity and structure. We used nested sampling designs in the intertidal and subtidal habitats, including horizontal spatial scales ranging from few centimetres to 1000s of metres along the rocky shore of Fildes Peninsula, King George Island. In both intertidal and subtidal habitats, univariate and multivariate analyses showed a marked vertical zonation in taxon richness and community structure. These patterns depended on the horizontal spatial scale of observation, as all analyses showed a significant interaction between height (or depth and the finer spatial scale analysed. Variance and pseudo-variance components supported our prediction for taxon richness, community structure, and the abundance of dominant species such as the filamentous green alga Urospora penicilliformis (intertidal, the herbivore Nacella concinna (intertidal, the large kelp-like Himantothallus grandifolius (subtidal, and the red crustose red alga Lithothamnion spp. (subtidal. We suggest that in coastal ecosystems strongly governed by physical factors, fine-scale processes (e.g. biotic interactions and refugia availability are still relevant for the structuring and maintenance of the local communities. The spatial patterns found in this study serve as a necessary benchmark to understand the dynamics and adaptation of natural assemblages in response to

  20. Up, down, and all around: scale-dependent spatial variation in rocky-shore communities of Fildes Peninsula, King George Island, Antarctica.

    Science.gov (United States)

    Valdivia, Nelson; Díaz, María J; Holtheuer, Jorge; Garrido, Ignacio; Huovinen, Pirjo; Gómez, Iván

    2014-01-01

    Understanding the variation of biodiversity along environmental gradients and multiple spatial scales is relevant for theoretical and management purposes. Hereby, we analysed the spatial variability in diversity and structure of intertidal and subtidal macrobenthic Antarctic communities along vertical environmental stress gradients and across multiple horizontal spatial scales. Since biotic interactions and local topographic features are likely major factors for coastal assemblages, we tested the hypothesis that fine-scale processes influence the effects of the vertical environmental stress gradients on the macrobenthic diversity and structure. We used nested sampling designs in the intertidal and subtidal habitats, including horizontal spatial scales ranging from few centimetres to 1000s of metres along the rocky shore of Fildes Peninsula, King George Island. In both intertidal and subtidal habitats, univariate and multivariate analyses showed a marked vertical zonation in taxon richness and community structure. These patterns depended on the horizontal spatial scale of observation, as all analyses showed a significant interaction between height (or depth) and the finer spatial scale analysed. Variance and pseudo-variance components supported our prediction for taxon richness, community structure, and the abundance of dominant species such as the filamentous green alga Urospora penicilliformis (intertidal), the herbivore Nacella concinna (intertidal), the large kelp-like Himantothallus grandifolius (subtidal), and the red crustose red alga Lithothamnion spp. (subtidal). We suggest that in coastal ecosystems strongly governed by physical factors, fine-scale processes (e.g. biotic interactions and refugia availability) are still relevant for the structuring and maintenance of the local communities. The spatial patterns found in this study serve as a necessary benchmark to understand the dynamics and adaptation of natural assemblages in response to observed and

  1. Lithofacies, biofacies, and ichnoassemblage evolution of a shallow submarine volcaniclastic fan-shelf depositional system (Upper Cretaceous, James Ross Island, Antarctica)

    Science.gov (United States)

    Scasso, R. A.; Olivero, E. B.; Buatois, L. A.

    The Upper Cretaceous (Santonian-Campanian/lower Maastrichtian) Santa Marta Formation on James Ross Island, Antarctica, represents volcaniclastic shallow marine fan and shelf sedimentation adjacent to an active volcanic arc. A combined analysis of sedimentologic, paleoecologic, and ichnologic data allows for the recognition in this unit of six lithofacies associations, eight biofacies, and five trace fossils assemblages. Lithofacies are dominated by fine, massive, tuffaceous rocks; graded, turbidite-like tuffaceous sandstones; carbonaceous mudstones; resedimented conglomerates; coquinas; sandstones; silty sandstones; and minor stromatolite beds. Biofacies are defined by different composition and relative abundance of elements of the benthic fauna, mainly bivalves, gastropods, and serpulids, with minor elements represented by scaphopods, corals, brachiopods, and echinoids. Trace fossil assemblages include the most common elements of the Skolithos and Cruziana ichnofacies. A striking result of the analysis is that lithofacies, biofacies, and trace fossil assemblages form distinct, non-repetitive, vertically successive horizons, with their distribution boundaries roughly coincident. On this basis, seven major facies groups, showing a distinct combination of lithofacies, biofacies, and trace fossils, are distinguished in the Santa Marta Formation. These non-repetitive, vertically stacked facies groups reveal a one-way evolution of the depositional system during a transgressive-regressive cycle, with a new transgression at the top of the unit. The lower facies groups represent shallow marine settings with a very high rate of volcaniclastic sedimentation within subsiding basin. Shallow, volcaniclastic fan systems were probably formed at the base of delta slope and grew rapidly as a consequence of high sedimentary supply in equilibrium with basin subsidence. The upper facies groups probably represent sedimentation within the marine part of the envisaged deltaic system on a

  2. Lu-Hf systematics of the ultra-high temperature Napier Complex, East Antarctica: evidence for the early Archean formation of continental crust

    Science.gov (United States)

    Choi, S.; Mukasa, S. B.; Andronikov, A. V.; Osanai, Y.; Harley, S. L.; Kelly, N. M.

    2009-12-01

    The Napier Complex in East Antarctica comprises some of the oldest rocks on earth (~3.8 billion years old), overprinted by an ultra-high temperature (UHT) metamorphic event near the Archean-Proterozoic boundary. Garnet, orthopyroxene, sapphirine, osumilite, rutile and a whole rock representing an equilibrated assemblage from this belt yield a Lu-Hf isochron age of 2,403 ± 43 Ma. Preservation of the UHT mineral assemblage in the rock analyzed suggests rapid cooling with closure likely to have occurred for the Lu-Hf system at post-peak UHT conditions near a temperature of ~800C. Individual zircon grains from Gage Ridge within the Napier Complex yielded a remarkably uniform range of 176Hf/177Hf values between 0.280433 ± 7 and 0.280505 ± 10, corresponding to ɛHf > +5.6 at 3.85 Ga relative to the chondritic uniform reservoir (CHUR). Because of their exceedingly low Lu/Hf values (<0.001), the grains are effectively recording the initial Hf isotope composition of the magmatic systems from which the gneiss protoliths crystallized. These results indicate that (1) the source of the crustal materials that formed the Napier Complex at 3.85 Ga were depleted relative to the CHUR. The extent of depletion involved is higher than has been predicted by extrapolation from the Lu-Hf isotopic evolution inferred for the source of Proterozoic and Phanerozoic basalts, judging from an fLu/Hf value of 0.51, (2) the depleted mantle reservoir has been in existence since very early in Earth’s history, in agreement with the early differentiation of the Earth that the latest core formation models require, and (3) an extremely depleted source also mean that the bulk of continental crust was extracted from the mantle by ~3.8 Ga. Moreover, the results demonstrate that even the oldest silicic rocks in the complex are not likely to have formed from remobilized older crustal materials, but were instead juvenile products of mantle melting. In addition, zircons with metamorphic rims have a similar

  3. 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.

  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. Prograde infiltration of Cl-rich fluid into the granulitic continental crust from a collision zone in East Antarctica (Perlebandet, Sør Rondane Mountains)

    Science.gov (United States)

    Kawakami, Tetsuo; Higashino, Fumiko; Skrzypek, Etienne; Satish-Kumar, M.; Grantham, Geoffrey; Tsuchiya, Noriyoshi; Ishikawa, Masahiro; Sakata, Shuhei; Hirata, Takafumi

    2017-03-01

    Utilizing microstructures of Cl-bearing biotite in pelitic and felsic metamorphic rocks, the timing of Cl-rich fluid infiltration is correlated with the pressure-temperature-time (P-T-t) path of upper amphibolite- to granulite-facies metamorphic rocks from Perlebandet, Sør Rondane Mountains (SRM), East Antarctica. Microstructural observation indicates that the stable Al2SiO5 polymorph changed from sillimanite to kyanite + andalusite + sillimanite, and P-T estimates from geothermobarometry point to a counterclockwise P-T path characteristic of the SW terrane of the SRM. In situ laser ablation inductively coupled plasma mass spectrometry for U-Pb dating of zircon inclusions in garnet yielded ca. 580 Ma, likely representing the age of garnet-forming metamorphism at Perlebandet. Inclusion-host relationships among garnet, sillimanite, and Cl-rich biotite (Cl > 0.4 wt%) reveal that formation of Cl-rich biotite took place during prograde metamorphism in the sillimanite stability field. This process probably predated partial melting consuming biotite (Cl = 0.1-0.3 wt%). This was followed by retrograde, moderately Cl-bearing biotite (Cl = 0.1-0.3 wt%) replacing garnet. Similar timings of Cl-rich biotite formation in different samples, and similar f(H2O)/f(HCl) values of coexisting fluid estimated for each stage can be best explained by prograde Cl-rich fluid infiltration. Fluid-present partial melting at the onset of prograde metamorphism probably contributed to elevate the Cl concentration (and possibly salinity) of the fluid, and consumption of the fluid resulted in the progress of dehydration melting. The retrograde fluid was released from crystallizing Cl-bearing partial melts or derived externally. The prograde Cl-rich fluid infiltration in Perlebandet presumably took place at the uppermost part of the footwall of the collision boundary. Localized distribution of Cl-rich biotite and hornblende along large-scale shear zones and detachments in the SRM supports external

  6. 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...

  7. Evidence of macroalgal colonization on newly ice-free areas following glacial retreat in Potter Cove (South Shetland Islands), Antarctica.

    Science.gov (United States)

    Quartino, María Liliana; Deregibus, Dolores; Campana, Gabriela Laura; Latorre, Gustavo Edgar Juan; Momo, Fernando Roberto

    2013-01-01

    Climate warming has been related to glacial retreat along the Western Antarctic Peninsula. Over the last years, a visible melting of Fourcade Glacier (Potter Cove, South Shetland Islands) has exposed newly ice-free hard bottom areas available for benthic colonization. However, ice melting produces a reduction of light penetration due to an increase of sediment input and higher ice impact. Seventeen years ago, the coastal sites close to the glacier cliffs were devoid of macroalgae. Are the newly ice-free areas suitable for macroalgal colonization? To tackle this question, underwater video transects were performed at six newly ice-free areas with different degree of glacial influence. Macroalgae were found in all sites, even in close proximity to the retreating glacier. We can show that: 1. The complexity of the macroalgal community is positively correlated to the elapsed time from the ice retreat, 2. Algae development depends on the optical conditions and the sediment input in the water column; some species are limited by light availability, 3. Macroalgal colonization is negatively affected by the ice disturbance, 4. The colonization is determined by the size and type of substrate and by the slope of the bottom. As macroalgae are probably one of the main energy sources for the benthos, an expansion of the macroalgal distribution can be expected to affect the matter and energy fluxes in Potter Cove ecosystem.

  8. Evidence of macroalgal colonization on newly ice-free areas following glacial retreat in Potter Cove (South Shetland Islands, Antarctica.

    Directory of Open Access Journals (Sweden)

    María Liliana Quartino

    Full Text Available Climate warming has been related to glacial retreat along the Western Antarctic Peninsula. Over the last years, a visible melting of Fourcade Glacier (Potter Cove, South Shetland Islands has exposed newly ice-free hard bottom areas available for benthic colonization. However, ice melting produces a reduction of light penetration due to an increase of sediment input and higher ice impact. Seventeen years ago, the coastal sites close to the glacier cliffs were devoid of macroalgae. Are the newly ice-free areas suitable for macroalgal colonization? To tackle this question, underwater video transects were performed at six newly ice-free areas with different degree of glacial influence. Macroalgae were found in all sites, even in close proximity to the retreating glacier. We can show that: 1. The complexity of the macroalgal community is positively correlated to the elapsed time from the ice retreat, 2. Algae development depends on the optical conditions and the sediment input in the water column; some species are limited by light availability, 3. Macroalgal colonization is negatively affected by the ice disturbance, 4. The colonization is determined by the size and type of substrate and by the slope of the bottom. As macroalgae are probably one of the main energy sources for the benthos, an expansion of the macroalgal distribution can be expected to affect the matter and energy fluxes in Potter Cove ecosystem.

  9. A 125-year record of climate and chemistry variability at the Pine Island Glacier ice divide, Antarctica

    Science.gov (United States)

    Schwanck, Franciele; Simões, Jefferson C.; Handley, Michael; Mayewski, Paul A.; Auger, Jeffrey D.; Bernardo, Ronaldo T.; Aquino, Francisco E.

    2017-07-01

    The Mount Johns (MJ) ice core (79°55' S; 94°23' W) was drilled near the Pine Island Glacier ice divide on the West Antarctic Ice Sheet during the 2008-2009 austral summer, to a depth of 92.26 m. The upper 45 m of the record covers approximately 125 years (1883-2008), showing marked seasonal variability. Trace element concentrations in 2137 samples were determined using inductively coupled plasma mass spectrometry. In this study, we reconstruct mineral dust and sea salt aerosol transport and investigate the influence of climate variables on the elemental concentrations at the MJ site. The ice core record reflects changes in emissions as well as atmospheric circulation and transport processes. Our trajectory analysis shows distinct seasonality, with strong westerly transport in the winter months and secondary northeasterly transport in the summer. During summer months, the trajectories present slow-moving (short) transport and are more locally influenced than in other seasons. Finally, our reanalysis correlations with trace element suggest that marine-derived trace element concentrations are strongly influenced by sea ice concentration and sea surface temperature anomalies. The results show that seasonal elemental concentration maxima in sea salt elements correlate well with the sea ice concentration winter maxima in the west Amundsen and Ross seas. Lastly, we observed an increased concentration of marine aerosols when sea surface temperature decreased.

  10. Dust and associated trace element fluxes in a firn core from the coastal East Antarctica and its linkages with the Southern Hemisphere climate variability over the last ~ 50 yr

    Directory of Open Access Journals (Sweden)

    C. M. Laluraj

    2013-04-01

    Full Text Available High-resolution records of dust and trace element fluxes were studied in a firn core from the coastal Dronning Maud Land (cDML in East Antarctica to identify the influence of climate variability on accumulation of these components over the past ~ 50 yr. A doubling of dust deposition was observed since 1985, coinciding with a shift in the Southern Annular Mode (SAM index to positive values and associated increase in the wind speed. Back-trajectories showed that an increase in dust deposition is associated with the air parcels originating from north-west of the site, possibly indicating its origin from the Patagonian region. Our results suggest that while multiple processes could have influenced the increased dust formation, shift in SAM had a dominant influence on its transport. It is observed that since the 1985s the strength of easterlies increased significantly over the cDML region, which could sink air and dust material to the region that were brought by the westerlies through mass compensation. The correlation between the dust flux and δ18O records further suggest that enhanced dust flux in the firn core occurred during periods of colder atmospheric temperature, which reduced the moisture content and increased dust fall. Interestingly, the timing and amplitude of the insoluble dust peaks matched remarkably well with the fluxes of Ba, Cr, Cu, and Zn confirming that dust was the main carrier/source of atmospheric trace elements to East Antarctica during the recent past.

  11. Novel flame retardants (N-FRs), polybrominated diphenyl ethers (PBDEs) and dioxin-like polychlorinated biphenyls (DL-PCBs) in fish, penguin, and skua from King George Island, Antarctica.

    Science.gov (United States)

    Wolschke, Hendrik; Meng, Xiang-Zhou; Xie, Zhiyong; Ebinghaus, Ralf; Cai, Minghong

    2015-07-15

    Persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), are frequently detected in biota from Antarctica, whereas no data are available for their replacements, such as novel flame retardants (N-FRs). This study presented the occurrence of several N-FRs, PBDEs, and PCBs in tissue samples of an Antarctic rock cod (Trematomus bernacchii), a young gentoo penguin (Pygoscelis papua), and a brown skua (Stercorarius antarcticus) collected from King George Island. The total concentrations of N-FRs (ΣN-FRs; mean: 931 pg/g dry weight (dw)) were comparable to PBDEs (Σ8PBDEs; 681 pg/gdw), which were much lower than PCBs (ΣDL-PCBs; 12,800 pg/gdw). Overall, skua contained two to three orders of magnitude higher contamination than penguin and fish. In the future, more attention should be focused on the fate of N-FRs in Antarctica, where usages have increased since PBDEs were banned. To our knowledge, this is the first report of N-FRs in biota from Antarctica.

  12. A GIS FOR THE ANTARCTIC SPECIALLY MANAGED AREA OF ADMIRALTY BAY,KING GEORGE ISLAND,ANTARCTICA

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    ABSTRACT A GIS is proposed as a tool for the managing plan for the Antarctic specially managed area (ASMA) in Admiralty Bay.The ASMA comprises the area considered to be within the glacial drainage basin of the bay.Furthermore,it includes part of SSSI No.8 adjacent to the area but outside of the glacial drainage basin.Three stations and six refuges are located in the area.Using a SPOT satellite image map,the limits of the ASMA are marked and its area is re_calculated.It consists of 362 km2,including 186 km2 island ice field and small cirque glaciers and 32 km2 ice_free field.The rest comprises water of the bay and a small adjacent area (8 km2) of the Bransfield Strait. The ASMA_GIS will consists of 12 data layers ranging from the physiographic settings to the biological and administrative features.All data will be implemented into Arc/Info GIS according to the cartographic guidelines of the SCAR WG_GGI.First,five plans of information will be realised using a topographic database compiled from various sources and data from the revised bathymetric chart published by the Brazilian Navy Hydrographic Survey and also including: 1) Limits of the ASMA and protected areas;2) Glaciological features (e.g.drainage basin limits) and 3) Human presence (e.g.stations and historical sites).These basic GIS layers will be operational in early 2001.Then,additional data on the remaining layers (e.g.hydrology,geology and geomorphology) will be included from published sources. The ASMA_GIS will form an important database for environmental monitoring and studies surveying temporal changes of features such as glacier front positions or bird breading sites.

  13. Multiplets and Detection of Seismic Velocity Changes During the 1998-99 Seismic Series at Deception Island Volcano, Antarctica

    Science.gov (United States)

    Carmona, E.; Martini, F.; Ibanez, J. M.; Bean, C. J.

    2007-12-01

    During the 1998-1999 Antarctic summer, the pattern of seismicity at Deception Island Volcano changed significantly with respect to previous years. This was characterized by the occurrence of an intense swarm of local earthquakes. More than 2000 local earthquakes were recorded in the period January-February 1999. The average moment magnitude was around 0.5, with the exception of two earthquakes of magnitude 2.3 and 3.4; array analysis was used to establish the hypocentral distribution of the earthquakes. A regional origin of the seismicity, or direct involvement of magmatic fluids, was demonstrated to be unlikely. Most earthquakes in the series were found to be related to small (pressurized fluids (Ibanez et al. 2003). The presence of fluids in the source area could explain the fracturing process and is supported by the observation of hybrid events in the same source region. The study of the spatial distribution of the first motion of the P waves suggests that different source mechanisms acted in a very small volume, and often at the same time. Many distinct families of events with very similar waveforms were identified. When recorded at the same station, the similarity of repeating earthquakes indicates that source and wavepath are the same, and therefore any observed difference in waveforms is related to a change in the medium. Employing Coda Wave Interferometry (Snieder et al., 2002), the families of events identified in the series show a drop in the velocity over a short time period around the two events with bigger magnitudes. These variations may be related to cracking and/or fluid influx. After the seismic crisis, a change in the composition of the fumarolic gases was observed with the appearance of sulfur deposits around the fumaroles, and a clear uplift and inflation of a few centimeters was detected (Garcia et al., 2001). The seismic characteristics and the spatial and temporal behavior of the series, associated with other geochemical, bathymetric and

  14. Pre-Fukushima levels of artificial radionuclides activities in maritime samples from King George Island (South Shetlands, Antarctica)

    Energy Technology Data Exchange (ETDEWEB)

    Sobiech-Matura, K. [European Commision DG-JRC Institute for Reference Materials and Measurements, Retieseweg 111, Geel (Belgium); Institute of Botany, Zdzislaw Czeppe Department of Polar Research and Documentation, Jagiellonian University, Kopernika 27, Krakow (Poland); Mietelski, J.W. [The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, W.E. Radzikowskiego 152, Krakow (Poland); Olech, M.A. [Institute of Botany, Zdzislaw Czeppe Department of Polar Research and Documentation, Jagiellonian University, Kopernika 27, Krakow (Poland); Department of Antarctic Biology, Polish Academy of Sciences, Ustrzycka 10/12, Warsaw (Poland)

    2014-07-01

    Different maritime samples were collected at King George Island during Polish scientific expeditions in years 2005/2006 and 2006/2007. They originated mainly from Admiralty Bay region. Activities of {sup 137}Cs, {sup 238,239+240}Pu, {sup 90}Sr and {sup 241}Am were measured using γ-, β- and α-spectrometry. Our measurements allow estimating the state of radioactive pollution of Antarctic environment directly before the Fukushima accident. Examined samples included different elements of Antarctic marine environment: macro-algae (e.g. Cystosphaera jacquinotii, Ascoseira mirabilis), fishes(e.g. Notothenia coriiceps, Chaenocephalus aceratus), birds (e.g. Pygoscelis adeliae, P. papua), and crustaceans (e.g. Euphausia superba, Waldeckia obesa). Activity concentrations of {sup 137}Cs vary from <0.3 to 21.8 ± 2.1 Bq/kg d.w. In comparison with results obtained for samples of animals and macro-algae previously [1,2] our results are similar or lower. Activity concentrations of {sup 239+240}Pu range from <0.2 to 455 ± 56 mBq/kg d.w. and comparing to previous results [1,2] they were similar or lower. For maritime animals from Terra Nova Bay [3] results are also similar or lower than obtained in present project. Activity concentrations of {sup 238}Pu in samples varied from <0.2 to 79 ± 22 mBq/kg d.w. In comparison to results presented in [1,2,3] our values are similar or higher. Activity concentrations obtained for {sup 90}Sr varied from <1.5 to 73 ± 24 Bq/kg d.w. and are similar or lower then values given in [2,3]. Activity concentrations of {sup 241}Am varied from <9.4 to 29.8 ± 9.3 mBq/kg d.w. and they are similar or higher than values obtained in [3] and similar to that from [1]. Obtained results show that levels of radioactive contamination were very low and in many cases lower than the detection limit. Planned further investigation will allow estimating the environmental condition after the Fukushima accident. (authors)

  15. East Asian monsoon variation and climate changes in Jeju Island, Korea, during the latest Pleistocene to early Holocene

    Science.gov (United States)

    Lee, Seung Hyoun; Lee, Yong Il; Yoon, Ho Il; Yoo, Kyu-Cheul

    2008-09-01

    A 4.96-m-long sediment core from the Hanon paleo-maar in Jeju Island, Korea was studied to investigate the paleoclimatic change and East Asian monsoon variations during the latest Pleistocene to early Holocene (23,000-9000 cal yr BP). High-resolution TOC content, magnetic susceptibility, and major element composition data indicate that Jeju Island experienced the coldest climate around 18,000 cal yr BP, which corresponds to the last glacial maximum (LGM). Further, these multi-proxy data show an abrupt shift in climatic regime from cold and arid to warm and humid conditions at around 14,000 cal yr BP, which represents the commencement of the last major deglaciation. After the last major deglaciation, the TOC content decreased from 13,300 to 12,000 cal yr BP and from 11,500 to 9800 cal yr BP, thereby reflecting the weakening of the summer monsoon. The LGM in Jeju Island occurred later in comparison with the Chinese Loess Plateau. Such a disparity in climatic change events between central China and Jeju Island appears to be caused by the asynchrony between the coldest temperature event and the minimum precipitation event in central China and by the buffering effect of the Pacific Ocean.

  16. Pygoscelis antarcticus feathers as bioindicator of trace element risk in marine environments from Barton Peninsula, 25 de Mayo (King George) Island, Antarctica.

    Science.gov (United States)

    Catán, Soledad Perez; Bubach, Debora; Di Fonzo, Carla; Dopchiz, Laura; Arribére, Maria; Ansaldo, Martin

    2017-04-01

    We report the contents of elements in feathers of Chinstrap penguin (Pygoscelis antarcticus), which had not been informed up to now, such as silver and bromine and others listed as hazardous by the United States Environmental Protection Agency as arsenic, cobalt, chromium, and mercury. Analyses of the element concentrations in feathers, adult and chicken, from Barton Peninsulas at 25 de Mayo (King George) Island, South Shetlands, were made by Instrumental Neutron Activation Analysis. Samarium, lanthanum a, thorium, and uranium concentrations in Chinstrap penguin feathers were below 0.1 mg/kg. This suggests that the elements in feather do not come from atmospheric particles surface deposition. Arsenic (0.120 ± 0.050 mg/kg) and cobalt (0.030 ± 0.020 mg/kg) concentrations were lower than the reports for other colony of Chinstrap penguins, and essential elements as iron (26 ± 12 mg/kg), zinc (78.0 ± 5.3 mg/kg), and chromium (0.51 ± 0.27 mg/kg) were in the same range while Se (2.90 ± 0.65 mg/kg) content were the lowest reported. Mercury (0.43 ± 0.21 mg/kg), chromium (0.210 ± 0.060 mg/kg), and silver (0.083 ± 0.003 mg/kg) in chicks tended to be lower than in adults. Iron, cobalt, and arsenic concentrations in feathers found in this study were the lowest compared to measurements were in several penguin species in Antarctica. These results confirm to feathers like effective indicators for the trace elements incorporated in the penguins and it provide a data set which can adds to the baseline for bioindication studies using feathers.

  17. Seasonal variation of meteorological variables and recent surface ablation / accumulation rates on Davies Dome and Whisky Glacier, James Ross Island, Antarctica

    Science.gov (United States)

    Láska, K.; Nývlt, D.; Engel, Z.; Budík, L.

    2012-04-01

    In this study, surface mass balance data of two glaciers on James Ross Island, Antarctica, and its spatial and temporal variations are evaluated using snow ablation stakes, ground-penetrating radar, and dGPS measurements. The investigated glaciers are located on the Ulu Peninsula, northern part of James Ross Island. Davies Dome is an ice dome, which originates on the surface of a flat volcanic mesa at elevations >400 m a.s.l. and terminates with a single 700 m wide outlet in the Whisky Bay. Davies Dome has an area of ~6.5 km2 and lies in the altitude range of 0-514 m a.s.l. Whisky Glacier is a cold-based land-terminating valley glacier surrounded by an extensive moraine ridges made of debris-covered ice. The glacier has an area of ~2.4 km2 and lies in the altitude range of 215-520 m a.s.l. Within several summer austral summers, extensive field programme were carried out on both glaciers including the operation of two automatic weather stations, field mapping and mass balance measurements. Each station was equipped with albedometer CM7B (Kipp-Zonen, Netherlands), air temperature and humidity sensor EMS33 (EMS, Czech Republic), propeller anemometer 05103 (Young, USA), and snow depth sensors (Judd, USA). In the period 2009-2011, high seasonal and interdiurnal variability of incoming solar radiation and near-surface air temperature was found as a result of changes in the circulation patterns and synoptic-scale weather systems moving in the Circumpolar Trough. High ablation and accumulation rates were recorded mainly in the spring and summer seasons (October-February), while negligible changes were found in winter (May-September). The effects of positive degree-day temperatures on the surface ablation rates were examined using a linear regression model. In this approach, near-surface air temperature maps on the glacier surfaces were derived from digital elevation model according to actual temperature lapse rates. Mass balance investigations started in 2006 on Davies

  18. 东南极阿曼达湾湖泊沉积物物源的元素分析%GEOCHEMICAL ANALYSIS TO DETERMINE THE SOURCES OF LAKE SEDIMENTS FROM AMANDA BAY, EAST ANTARCTICA

    Institute of Scientific and Technical Information of China (English)

    黄涛; 孙立广

    2012-01-01

    2008年在东南极阿曼达湾帝企鹅聚集区附近岛屿开展了野外工作,于岛屿湖泊集水区采集到两个短沉积柱样,分别命名为EPI和PI.根据野外实地考察情况和室内分割样品发现EPI柱样主要为泥炭沉积,含有大量水生藻类;PI柱样为黑色泥质沉积,散发出浓烈的粪臭味,沉积物中含有大量的幼年帝企鹅绒毛和少量的残骨.对EPI和PI柱样沉积物、当地风化母岩及水生湖藻进行了部分生源元素和重金属元素浓度分析与对比,结果显示EPI柱样元素含量主要来源于背景母岩和湖藻沉积.PI柱样为帝企鹅粪土沉积序列,沉积物中的TC、TN、TP、Cu、Zn、Hg和Se的含量远远高于风化母岩中的浓度,其主要来源于帝企鹅粪的输入,而Pb元素主要来源于当地风化母岩的贡献.研究显示帝企鹅活动同样可以为南极贫瘠的陆地湖泊系统带来大量的营养物质,但同时也输入了大量的重金属污染元素.%Two short lake sediment cores,EPI and PI,were collected at N Island,Amanda Bay,East Antarctica,during the 2007-2008 seasons.The lithology and sedimentology of the EPI profile indicated a predominance of peat deposit.The PI sediments were composed of black mud,contained many penguin feathers and bones,and had a strong and unpleasant smell of penguin guano.Elemental concentrations in the sediments of the EPI and PI cores,local bedrock,and lake algae,were analyzed.The results indicated that elemental concentrations in the sediments of the EPI core were primarily derived from bedrock and lake algae.The abundance of total carbon (TC) ,total nitrogen (TN) ,total phosphorus (TP) ,Cu,Zn,Hg,and Se in the PI core sediments was much higher than that in local bedrock,suggesting that the sediments were mainly composed of emperor penguin guano,while the element Pb was derived from the geochemical background.This study demonstrates that emperor penguins transport marine-derived nutrients and heavy metal

  19. Surface winds over West Antarctica

    Science.gov (United States)

    Bromwich, David

    1993-01-01

    Five winter months (April-August 1988) of thermal infrared satellite images were examined to investigate the occurrence of dark (warm) signatures across the Ross Ice Shelf in the Antarctic continent. These features are inferred to be generated by katabatic winds that descend from southern Marie Byrd Land and then blow horizontally across the ice shelf. Significant mass is added to this airstream by katabatic winds blowing from the major glaciers that flow through the Transantarctic Mountains from East Antarctica. These negatively buoyant katabatic winds can reach the northwestern edge of the shelf - a horizontal propagation distance of up to 1,000 km - 14 percent of the time. Where the airstream crosses from the ice shelf to the ice-covered Ross Sea, a prominent coastal polynya is formed. Because the downslope buoyancy force is near zero over the Ross Ice Shelf, the northwestward propagation of the katabatic air mass requires pressure gradient support. The study shows that the extended horizontal propagation of this atmospheric density current occurred in conjunction with the passage of synoptic cyclones over the southern Amundsen Sea. These cyclones can strengthen the pressure gradient in the interior of West Antarctica and make the pressure field favorable for northwestward movement of the katabatic winds from West Antarctica across the ice shelf in a geostrophic direction. The glacier winds from East Antarctica are further accelerated by the synoptic pressure gradient, usually undergo abrupt adjustment beyond the exit to the glacier valley, and merge into the mountain-parallel katabatic air mass.

  20. Ontogenic changes in the feeding ecology of the early life stages of the Antarctic silverfish ( Pleuragramma antarcticum) documented by stable isotopes and diet analysis in the Dumont d’Urville Sea (East Antarctica)

    Science.gov (United States)

    Giraldo, Carolina; Cherel, Yves; Vallet, Carole; Mayzaud, Patrick; Tavernier, Eric; Moteki, Masato; Hosie, Graham; Koubbi, Philippe

    2011-08-01

    The feeding ecology of the notothenioid fish Pleuragramma antarcticum was studied in the Dumont d’Urville Sea (East Antarctica) near the French Antarctic station. Stable isotopes (δ 13C and δ 15N) and diet contents were used in order to study dietary shifts between fish larvae and juveniles. All specimens had low δ 13C values (<-24‰), a main characteristic of high-Antarctic pelagic species. Fish larvae showed differences in both carbon and nitrogen ratios when compared with juveniles. Muscle δ 15N values showed a difference of one trophic level (∼3‰) between larvae (6.7‰) and juveniles (9.7-10.0‰) and a trophic position of tertiary consumers. Diet content analyses (stereomicroscope and scanning electron microscopes) indicated that larvae are omnivorous, feeding on phytoplankton (mainly diatoms) as well as on zooplankton species. A positive relationship between δ 15N values and size was found and indicated a carnivorous diet for older specimens.

  1. Numerical simulation of the structure and variation of upwelling off the east coast of Hainan Island using QuikSCAT winds

    Institute of Scientific and Technical Information of China (English)

    LI Yineng; PENG Shiqiu; YANG Wei; WANG Dongxiao

    2012-01-01

    The spatial structure and variation of the upwelling in the waters east and northeast of Hainan Island,China during 2000-2007 were investigated using a nested high-resolution Princeton Ocean Model (POM) forced by QuikSCAT winds.The model produced good simulations of the summer upwelling and the seasonal and annual variability.Strong upwelling occurs from mid-July to mid-August with a peak east of Hainan Island associated with the southwesterly monsoon in the South China Sea.Sensitivity experiments indicated that when the local wind stress controls the variability of the upwelling,the large-scale circulation significantly enhances the upwelling northeast of Hainan Island by inducing a local upwelling and transporting cold water northeast-ward along the island's east coast.The joint effects of the local wind stress and large-scale circulation result in stronger upwelling northeast of Hainan Island.This implies that the annual variation of the upwelling northeast of Hainan Island is controlled not only by the local alongshore wind stress but also by the large-scale circulation.This result will help us investigate the decadal variation of the upwelling in this region in the future.

  2. Hello Antarctica

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    China has made 25 expeditions to the Antarctic over a quarter century Exactly 17,501.949 km-that’s the distance from Beijing to Changcheng (lit-erally meaning the Great Wall) Station,the first little piece of China on the continent of Antarctica. Twenty-five years ago, when the country was conceiving its first journey to the South Pole, that distance meant nothing

  3. Genomic islands of speciation separate cichlid ecomorphs in an East African crater lake.

    Science.gov (United States)

    Malinsky, Milan; Challis, Richard J; Tyers, Alexandra M; Schiffels, Stephan; Terai, Yohey; Ngatunga, Benjamin P; Miska, Eric A; Durbin, Richard; Genner, Martin J; Turner, George F

    2015-12-18

    The genomic causes and effects of divergent ecological selection during speciation are still poorly understood. Here we report the discovery and detailed characterization of early-stage adaptive divergence of two cichlid fish ecomorphs in a small (700 meters in diameter) isolated crater lake in Tanzania. The ecomorphs differ in depth preference, male breeding color, body shape, diet, and trophic morphology. With whole-genome sequences of 146 fish, we identified 98 clearly demarcated genomic "islands" of high differentiation and demonstrated the association of genotypes across these islands with divergent mate preferences. The islands contain candidate adaptive genes enriched for functions in sensory perception (including rhodopsin and other twilight-vision-associated genes), hormone signaling, and morphogenesis. Our study suggests mechanisms and genomic regions that may play a role in the closely related mega-radiation of Lake Malawi.

  4. Holoceno marino en la península Potter, Isla 25 de Mayo, Antártida Marine sediments of the early Holocene in the Potter Península, King George Island, Southern Shetland, Antarctica

    Directory of Open Access Journals (Sweden)

    R.A. del Valle

    2007-11-01

    Full Text Available La sucesión sedimentaria del Holoceno temprano expuesta en la terraza marina de 3,77 m s.n.m. en la costa sur de la caleta Potter (Isla 25 de Mayo/King George Island, islas Shetland del Sur, Antártida contiene invertebrados marinos, algas y huesos de foca y pingüino. Dataciones por radiocarbono de huesos de pingüino obtenidos en esta sucesión dieron edades de 7.562 a cal AP (años calibrados antes del Presente y 7.414 a cal AP. Las dataciones indican que los huesos están entre los restos de vertebrados más antiguos del Holoceno hallados en las Islas Shetland del Sur, y pueden ser consideradas como edades mínimas de ocupación por estas aves de las costas de las islas en el Holoceno temprano. Esto indica condiciones interglaciales en esa época, con situación clima/hielo marino similar a la presente y condiciones marinas estacionalmente abiertas.The early Holocene sedimentary succession exposed at the 3.77 m-high marine terrace on the south coast of Potter Cove (King George Island/Isla 25 de Mayo, South Shetland Islands, Antarctica contains marine invertebrates, seaweed and bones of seals and penguins. Radiocarbon dating on penguin bones from this succession yielded 7,562 cal yr BP and 7,414 cal yr BP. These dates suggest that the bones are among the oldest remains of Holocene vertebrates found in South Shetland Islands, and may be considered as minimum ages of penguin occupation of coastal areas on the islands during the early Holocene. This indicates interglacial conditions in this time, with climate/sea ice situation similar to the present and seasonally open marine conditions.

  5. CRED Gridded Bathymetry of East Necker Seamount (100-023) in the Northwestern Hawaiian Islands

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — File 100-023b is a 60-m ASCII grid of depth data collected near E. Necker Seamount in the Northwestern Hawaiian Islands as of May 2003. This grid has been produced...

  6. CRED Gridded Bathymetry of East Gardner Pinnacles (100-016) in the Northwestern Hawaiian Islands

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — File 100-016b is a 60-m ASCII grid of depth data collected near E Gardner Pinnacles in the Northwestern Hawaiian Islands as of May 2003. This grid has been produced...

  7. Assessment of survival, mortality and recovery of coral reefs of East Kish Island, Persian Gulf.

    Science.gov (United States)

    Jami, M J; Salehduost, A; Negarestan, H

    2010-10-15

    Coral reefs are specialized communities that develop clear, well-lit tropical and subtropical water; they provide shelter and canopy for great variety of organisms, living in mean temperature of 20 degrees C. Coral Bleaching and mortality have been associated with elevated seawater temperature. The aim of the study was to investigate coral bleaching and evaluate health condition of the corals. Distribution of coral reefs around Kish Island was determined by the Timed Swim (TS) technique. This survey carried out in 2 times (May and October, 2009) in 2 depths of 3-5 m and 6-10 m. Two Divers swam in constant speed for a set amount of time in three dive sites. The timed swim survey around the Kish Island showed that the most healthy live hard coral assemblages were found in the site called Persian Gulf seaport, whereas the greatest percentage of bleached corals were located in Jurassic Park station, located at the southeast of the Island. Branching corals (Acropora sp.) were bleached among all 3 stations and no sign of recovery could be detected. In Big coral site suitable substrate for accumulation of living organisms including Echinometra mathaie (sea urchin) existed due to presence of great amount of algae on dead corals and rocks. Based on the observation, it seems that the cause of reef destruction in Kish Island fall in to two categories, natural and human impacts.

  8. Architecture and evolution of an Early Permian carbonate complex on a tectonically active island in east-central California

    Science.gov (United States)

    Stevens, Calvin H.; Magginetti, Robert T.; Stone, Paul

    2015-01-01

    The newly named Upland Valley Limestone represents a carbonate complex that developed on and adjacent to a tectonically active island in east-central California during a brief interval of Early Permian (late Artinskian) time. This lithologically unique, relatively thin limestone unit lies within a thick sequence of predominantly siliciclastic rocks and is characterized by its high concentration of crinoidal debris, pronounced lateral changes in thickness and lithofacies, and a largely endemic fusulinid fauna. Most outcrops represent a carbonate platform and debris derived from it and shed downslope, but another group of outcrops represents one or possibly more isolated carbonate buildups that developed offshore from the platform. Tectonic activity in the area occurred before, probably during, and after deposition of this short-lived carbonate complex.

  9. 77 FR 43167 - Safety Zone; Electric Zoo Fireworks, East River, Randall's Island, NY

    Science.gov (United States)

    2012-07-24

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Electric Zoo Fireworks, East River, Randall... prior notice and opportunity to comment when the agency for good cause finds that those procedures are... finds that good cause exists for not publishing a notice of proposed rulemaking (NPRM) with respect...

  10. 75 FR 12688 - Drawbridge Operation Regulations; Long Island, New York Inland Waterway from East Rockaway Inlet...

    Science.gov (United States)

    2010-03-17

    ... Waterway from East Rockaway Inlet to Shinnecock Canal, NY, Maintenance AGENCY: Coast Guard, DHS. ACTION... to replace the motor locks at the bridge. The bridge can not open during the installation of the motor locks. Under this deviation the Wreck Lead Railroad Bridge may remain closed from 9 a.m. through...

  11. 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

  12. 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...

  13. Prevalence of soil-transmitted helminths in remote villages in East Kwaio, Solomon Islands

    Directory of Open Access Journals (Sweden)

    Humpress Harrington

    2015-08-01

    Full Text Available Objective: Although soil-transmitted helminths (STH are endemic in Solomon Islands, there are few recent reports on their prevalence. This study aimed to determine the prevalence of STH in residents of remote communities in Solomon Islands. Methods: A cross-sectional convenience-sampled survey of residents of four adjacent villages in Malaita, Solomon Islands was performed in Atoifi and Na’au in April 2011 and in Abitona and Sifilo in April 2012. All residents older than one year were invited to participate, which involved providing a single sample of faeces examined using a modified Kato-Katz technique and completing a questionnaire that asked demographic and STH-related behaviour questions. Results: The overall participation rate was 52.8%, with 402 participants comprising 49.8% males. Hookworm was the predominant STH with only a single case of trichuriasis found in Atoifi. The total prevalence of hookworm was 22.6% (95% confidence interval: 18.6–27.1; the prevalence of hookworm in Abitona, Na’au and Sifilo was 20.0%, 29.9% and 27.4%, respectively, whereas in Atoifi it was 2.3% (P < 0.001. Intensity was low in all villages. Although health behaviours differed significantly between Atoifi and the other three villages, the type of toilet used was the only significant association with hookworm. Discussion: Residents of Atoifi have a relative freedom from STH compared to the other three villages. Rather than a region-wide morbidity control approach, a “one village at a time” approach aiming to eliminate STH and dealing with each village as a separate autonomous unit empowered to manage its own challenges may be a preferred option.

  14. Prevalence of soil-transmitted helminths in remote villages in East Kwaio, Solomon Islands.

    Science.gov (United States)

    Harrington, Humpress; Bradbury, Richard; Taeka, James; Asugeni, James; Asugeni, Vunivesi; Igeni, Tony; Gwala, John; Newton, Lawrence; Fa, Chillion Evan; Kilivisi, Fawcett Laurence; Esau, Dorothy; Flores, Angelica; Ribeyro, Elmer; Liku, Daisy; Muse, Alwin; Asugeni, Lyndel; Talana, Jeptha; Shield, Jennifer; MacLaren, David J; Massey, Peter D; Muller, Reinhold; Speare, Rick

    2015-01-01

    Although soil-transmitted helminths (STH) are endemic in Solomon Islands, there are few recent reports on their prevalence. This study aimed to determine the prevalence of STH in residents of remote communities in Solomon Islands. A cross-sectional convenience-sampled survey of residents of four adjacent villages in Malaita, Solomon Islands was performed in Atoifi and Na'au in April 2011 and in Abitona and Sifilo in April 2012. All residents older than one year were invited to participate, which involved providing a single sample of faeces examined using a modified Kato-Katz technique and completing a questionnaire that asked demographic and STH-related behaviour questions. The overall participation rate was 52.8%, with 402 participants comprising 49.8% males. Hookworm was the predominant STH with only a single case of trichuriasis found in Atoifi. The total prevalence of hookworm was 22.6% (95% confidence interval: 18.6-27.1); the prevalence of hookworm in Abitona, Na'au and Sifilo was 20.0%, 29.9% and 27.4%, respectively, whereas in Atoifi it was 2.3% (P < 0.001). Intensity was low in all villages. Although health behaviours differed significantly between Atoifi and the other three villages, the type of toilet used was the only significant association with hookworm. Residents of Atoifi have a relative freedom from STH compared to the other three villages. Rather than a region-wide morbidity control approach, a "one village at a time" approach aiming to eliminate STH and dealing with each village as a separate autonomous unit empowered to manage its own challenges may be a preferred option.

  15. Factors affecting spring bloom in the South of Cheju Island in the East China Sea

    Institute of Scientific and Technical Information of China (English)

    FU Dongyang; HUANG Zhaojun; ZHANG Yuanzhi; PAN Delu; DING Youzhua; LIU Dazhao; ZHANG Ying; MAO Zhihua; CHEN Jianfang

    2015-01-01

    A soil circulation occurs in the south of Cheju Island in the spring. Nutrients and its influence on chloro-phyll a (Chla) around the circulations were studied from April 9 to May 6, 2007. Spring bloom with elevated concentrations of Chla was observed during the investigation. High concentrations of phosphate, nitrate and silicate at 0.6, 12, and 8 mmol/m3, respectively, were detected. A low water temperature prevented the growth of phytoplankton. Chla concentrations in the study area might be strongly associated with the high silicate concentration.

  16. Combined apatite fission-track and single grain apatite (U Th)/He ages from basement rocks of central Dronning Maud Land (East Antarctica) — Possible identification of thermally overprinted crustal segments?

    Science.gov (United States)

    Emmel, B.; Jacobs, J.; Crowhurst, P.; Daszinnies, M. C.

    2007-12-01

    Apatite fission-track (FT) and single grain (U-Th)/He ages from four vertical profiles in central Dronning Maud Land (East Antarctica) range from 312 ± 20 Ma to 135 ± 11 Ma and 304 ± 28 Ma to 104 ± 8 Ma, respectively. The combined age data allows to discriminate between undisturbed cooled (due to exhumation) and thermally overprinted crustal blocks. Profiles at the Zwieselhöhe and the Conradgebirge revealed unusual apatite FT vs. elevation relationships and (U-Th)/He ages older than the corresponding central apatite FT ages, possibly providing evidence for a Jurassic thermal overprint. Most probably Jurassic magmatism and associated advective heating led to total annealing of the apatite fission-tracks but helium only partially diffused. The model developed in this paper suggests that the (U-Th)/He ages from the Zwieselhöhe and Conradgebirge profiles are in part relicts of the pre-Jurassic cooling history. Two thermally undisturbed vertical profiles are used to record the long-term cooling history of central Dronning Maud Land. Time-temperature paths derived from modelled apatite FT data of these profiles revealed two phases of accelerated cooling during the Late Carboniferous and the Early Jurassic. Both phases are followed by slow cooling which is also documented by the spread in apatite (U-Th)/He single grain ages. The cooling at the end of the Carboniferous is most probably related to far field effects associated to the prevailing convergent tectonics. During the initial separation between East Antarctica and Mozambique erosion along an evolving rift shoulder caused the Jurassic cooling. Denudation of the basement was simultaneous with volcanism with both pre-dating (c. 20-10 Ma) sea-floor spreading in the Riser Larsen Sea (c. 155 Ma). Post Jurassic cooling was restricted to the lowest temperature sensitivity of both methods. Combined inverse modelled apatite FT data and forward modelled (U-Th)/He data suggest an Eocene/Oligocene cooling step, possibly

  17. X-RAY FLUORESCENT ANALYSIS OF THE 6 SPECIES OF BRYOPHYTE IN THE KING GEORGE ISLAND, ANTARCTICA%南极乔治王岛六种苔藓植物的X荧光分析

    Institute of Scientific and Technical Information of China (English)

    黄宇营; 巨新; 康士秀; 吴自勤; 沈显生; 孙立广; 尹雪斌; 张莉

    2001-01-01

    在无标样条件下,我们利用微束X荧光分析法对南极乔治王岛的6种苔藓植物的叶和茎进行重元素分析。它们是:Andreaea regularis, Bryum muehlenbeckii, Drepanocladus uncinatus, Brachythecium subpilosum, Tortula saxiola, Ditrichum austro-georgicum。研究结果发现,不同苔藓植物对各种不同重元素的吸收能力不同,即使是同一种植物,叶和茎中的重元素成分也有差异。在6种苔藓中,Andreaea regularis 体内的重元素种类最少,但其对Fe有较强的吸收。由于南极环境条件优越,在苔藓植物体内,尚未发现大量有毒重金属元素的存在。%Without a standard specimen, we analysed the heavy element content of 6 moss species in the King George Island of Antarctica by XRF. They are Andreaea regularis, Bryum muehlenbeckii, Drepanocladus uncinatus, Brachythecium subpilosum, Tortula saxiola and Ditrichum austro-georgicum. We found that various plants absorbed varied heavy elements. Even if the same moss, there are the different elements in leaves and stems. Andreaea regularis is possessed of the fewest heavy element varieties in 6 species of bryophyte, but it absorbs Fe more powerfully. Owing to superior environment, we didn't find a lot of poisonous heavy metal elements in bryophyte of Antarctica.

  18. NCCOS National Status and Trends Bioeffects Assessment: Chemical contaminant data in the St. Thomas East End Reserves, U.S. Virgin Islands, from 2010-05-04 to 2012-06-22 (NCEI Accession 0146168)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset provides valuable baseline data on sediment chemical contamination for the St. Thomas East End Reserve (STEER), U.S. Virgin Islands (USVI). From...

  19. THE ANALYSIS OF FACTORS AFFECTING THE PERFORMANCE AND BENEFIT OF KARAPAN (RACING CATTLE BUSINESS IN MADURA ISLAND, EAST JAVA, INDONESIA

    Directory of Open Access Journals (Sweden)

    Riszqina Riszqina

    2014-09-01

    Full Text Available A research was carried out to analyze the influence of productive factors on the performance ofkarapan (means racing cattle business in Madura Island, East Java Province, Indonesia. The researchwas conducted by a survey method, with 135 karapan cattle farmers as respondents in regencies ofBangkalan, Sampang, Pamekasan and Sumenep (mainland. The data were collected in the period ofApril to August 2012. Data of zootechnique indicators variables, farmer’s motivation, allocation time oflabour, labour skills, business scale, productivity of karapan cattle, farmers' performance and benefit ofkarapan cattle business were analysed by Lisrel 8.8 program. The results showed that factors ofzootechnique, farmer’s motivation, labour skills and business scale had highly significant influence(P<0.01 on productivity of karapan cattle, but allocation time of labour did not have significantinfluence (P>0.05. The performance of karapan cattle business was highly influenced by productivity ofkarapan cattle (P<0.01. The benefit of karapan cattle business was influenced (P<0.01 by performanceof karapan cattle business. It is concluded that the farmer's benefit of karapan cattle business wasinfluenced by performance of karapan cattle, which in turn was influenced by productivity of thekarapan cattle.

  20. The language attitude of border peoples Insular Riau, West Kalimantan, East Kalimantan, North Sulawesi, and the Eastern Sunda Islands

    Directory of Open Access Journals (Sweden)

    Dendy Sugono

    2011-04-01

    Full Text Available This research aims at describing (1 the language use of border area societies (Insular Riau, West Kalimantan, East Kalimantan, North Sulawesi, and the Eastern Sunda Islands in terms of local language (BD, Indonesian (BI, and foreign language (BA in the domains of family, society, and occupation, (2 language activity of border area societies relating to news observation, language attention, and language constraints in mass media, (3 language attitude of border area societies towards BD, BI, and BA. The findings are as follows. First, within the family and society at large, BD is more frequently used than BI and BA. This shows that BD functions in non-formal situations. In the professional field, however, BI is more frequently used than BD. Second, people in border provinces widely observe mass media, whether printed or electronic. They also often pay attention to the language the mass media uses. Third, border societies have a positive attitude towards BD as is shown (agree/totally agree by the answers to eight questions relating to BD. The language attitude of border societies towards BI is positive based on the answers (agree/totally agree to seven questions concerning BI. This also means that BI is prestigious for border people, especially in formal communication. The language attitude of border societies towards BA is mixed. In as far as it is negative it implies a positive evaluation of BD and BI because people appreciate them as part of their local and national identities.

  1. Geology and Genesis of Peraluminous Granites in East Tianshan Upper Paleozoic Island Arc Belt

    Institute of Scientific and Technical Information of China (English)

    顾连兴; 严正富; 等

    1996-01-01

    A peraluminous granite belt occurs along the connecting zone between the Turpan Hami Precambrian block and the Upper Paleozoic island arc belt.Muscovite granite and twomica granite are the essential lithological components of that belt.All the potassium feldspars in these granites are microcline.Heavy minerals are dominated by magnetite,SiO2 contents of these granites are greater than 73% with most of the A/NKC values greater than 1,1,norma tive corundum values greater than 1 Plots of CIPW norms in the (Al-K-Na) Ca(Fe2++Mg) diagran are mostly situated in the plagioclase cordierite-muscovite region.The rocks are characterized by very low contents of minor elements and ∑REE with strong Eu depletion δ18 O values between 6.6‰and 7.0‰,Rb-Sr isochron age of 260.2±6.2Ma and an initial 87Sr/86 Sr ration of 0.7052,These granites might have been produced by partial melting of moderately acidic volcanites and low-maturity sediments in the basement sequences and could be genetically connected with the southware A-type subduction of the Turpan-Hami block following the closure of the Middle Carboniferous back-arc basin.

  2. Extended correlation of the Paleogene Faroe Islands and East Greenland plateau basalts

    DEFF Research Database (Denmark)

    Søager, Nina; Holm, Paul Martin

    2008-01-01

    New analytical data are presented for 13 enriched high-Ti tholeiitic basalts from the top of the Faroese lava pile that was formed by the time of break-up of the North Atlantic  56-55  Ma ago and are located on the eastern continental margin of the Atlantic Ocean. The samples fall in three groups....../204Pb = 17.59-18.30 while the High-Ti3 group has 206Pb/204Pb = 18.88-19.12. The three Faroese lava groups can be correlated with the East Greenland syn-breakup basalt formations using their geochemistry, lava morphology and phenocryst contents. The High-Ti1 group correlates with the Milne Land......-Ti1 and Milne Land Formation lavas have a higher content of most incompatible elements compared to High-Ti2 and Geikie Plateau Formation. This is unexpected because the Zr/Nb ratio indicates that the High-Ti2 and Geikie Plateau Formation lavas are formed by lower degrees of melting. An explanation may...

  3. Late Cretaceous paleomagnetism of the East Ranges island arc complex, Kamchatka: Implications for terrane movements and kinematics of the northwest Pacific

    Science.gov (United States)

    Levashova, Natalia M.; Bazhenov, Mikhail L.; Shapiro, Mikhail N.

    1997-11-01

    A Campanian-lower Paleocene island arc complex was sampled for paleomagnetic studies at 12 sites in the East Ranges tectonic zone of Kamchatka. After thermal demagnetization, a reversed polarity characteristic remanent magnetization (ChRM) was isolated from most volcanoclastic and basaltic units as well as from lava debris from intraformational conglomerates. The fold and conglomerate tests are positive, and the ChRM in the studied rocks is likely primary. The formation-mean inclination of 66.3°±3.7° corresponds to a paleolatitude of 48.7°±5.0°N which is about 20° lower than the Late Cretaceous North American reference values. Because northward displacement of the studied terrane is indicated by the paleomagnetic data, we examine several models of intraoceanic transport with the Pacific and/or Kula plates and coastwise transport after terrane accretion, far to the south of the present-day position of Kamchatka. Our preferred interpretation is that the studied island arc complex accumulated at about 83-79 Ma; the island arc, to which the studied terrane had originally belonged, was active between this time and 65-60 Ma. According to geological data, the docking time nearly coincided with cessation of volcanic activity, and northward movement of the island arc took place simultaneously with the volcanic activity. The absolute motion of a subduction zone should have the same direction as the overriding plate; therefore, the subduction zone related to the East Ranges island arc is inferred to have moved northward with the Kula plate or with the Kula and Pacific plates, successively, consuming either the oceanic periphery of a continental plate or some unknown minor oceanic plate. This process went on until 65-55 Ma when the island arc and related subduction zone approached the continental margin and became extinct. The proposed models also place additional constraints on kinematics of the Kula-Pacific transform plate boundary.

  4. Dating a 109.9 m ice core from Dome A (East Antarctica) with volcanic records and a firn densification model

    Institute of Scientific and Technical Information of China (English)

    LI ChuanJin; XIAO CunDe; HOU ShuGui; REN JiaWen; DING MingHu; GUO Rui

    2012-01-01

    A 109.9 m ice core was extracted at a location about 300 m away from the Dome A summit (80°00′S,77°21″E) by the Chinese team of the International Trans-Antarctic Science Expedition (ITASE) during the 21st Chinese National Antarctica Research Expedition (CHINARE) in January 2005.Two independent methods were used for dating the ice core,volcanic event markers shown by prominent non-sea-salt sulfate (nss-SO42-) and the Herron and Langway (H-L) fim densification model.Six prominent volcanic events (Agung 1963 AD,Tambora 1815 AD,Kuwae 1453 AD,Unknown 1259 AD,Taupo 186 AD and Pinatubo 1050 BC) were identified by comparison with other Antarctic ice cores.Based on the mean accumulation rates between adjacent events,we estimate the age at the firn pore close-off depth (102 m) was 3516±100 a BP.This is the oldest close-off age ever reported from the Antarctic and the Greenland ice sheets.Calculations using the H-L model sho,w that the age at the same depth is 3581±100 a BP.The two dating techniques differ by 65 years,or-1.8% of the record.We calculated the bottom age of the ice core as 4009±150 a BP using the volcanic d,ating method and 4115±150 a BP using the H-L model method.

  5. Origin(s) of Antarctica's Wilkes subglacial basin

    NARCIS (Netherlands)

    Weihaupt, J.G.; Van der Hoeven, F.G.; Lorius, C.; Chambers, F.B.

    2013-01-01

    The Wilkes Subglacial Basin (WSB), the largest subglacial basin in East Antarctica, is a topographic depression of continental proportions that lies beneath the East Antarctic continental ice sheet. Discovered by the US Victoria Land Traverse 1959–60, the origin of the WSB and the influence of palae

  6. Reaction texture and Fe-Mg zoning in granulite garnet from Sstrene Island, Antarctica: Modeling and constraint on the time scale of metamorphism during the Pan-African Collisional event

    Indian Academy of Sciences (India)

    J Ganguly; B J Hensen; W Cheng

    2001-12-01

    Garnets from the Sstrene island, Antarctica, show reaction textures corresponding to two metamorphic episodes, one at c. 1000 Ma (M1) and the other at c. 500 Ma (M2). The latter is associated with a Pan-African tectono-metamorphic event that has been interpreted to represent a continent-continent collision followed by extensional collapse. Reaction-diffusion modeling of the compositional zoning of garnet associated with the development of reaction texture during M2 yields a time scale of ∼5-16 Myr for the duration of the peak of this overprinting metamorphism at ∼730 ± 20°C. The associated velocity of the reaction front is ∼∼5.0-1.6 m/Myr. The inferred duration of peak metamorphism during the Pan-African event seems to be in good agreement with the available U-Pb SHRIMP ages of zircon and monazite that may be interpreted to have formed at the beginning and end stages of crystallization of granite during the metamorphic peak.

  7. Transport of nutrients and contaminants from ocean to island by emperor penguins from Amanda Bay, East Antarctic.

    Science.gov (United States)

    Huang, Tao; Sun, Liguang; Wang, Yuhong; Chu, Zhuding; Qin, Xianyan; Yang, Lianjiao

    2014-01-15

    Penguins play important roles in the biogeochemical cycle between Antarctic Ocean and land ecosystems. The roles of emperor penguin Aptenodytes forsteri, however, are usually ignored because emperor penguin breeds in fast sea ice. In this study, we collected two sediment profiles (EPI and PI) from the N island near a large emperor penguin colony at Amanda Bay, East Antarctic and performed stable isotope and element analyses. The organic C/N ratios and carbon and nitrogen isotopes suggested an autochthonous source of organic materials for the sediments of EPI (C/N = 10.21 ± 0.28, n = 17; δ(13)C = -13.48 ± 0.50‰, δ(15)N = 8.35 ± 0.55‰, n = 4) and an allochthonous source of marine-derived organic materials for the sediments of PI (C/N = 6.15 ± 0.08, δ(13)C = -26.85 ± 0.11‰, δ(15)N = 21.21 ± 2.02‰, n = 20). The concentrations of total phosphorus (TP), selenium (Se), mercury (Hg) and zinc (Zn) in PI sediments were much higher than those in EPI, the concentration of copper (Cu) in PI was a little lower, and the concentration of element lead (Pb) showed no difference. As measured by the geoaccumulation indexes, Zn, TP, Hg and Se were from moderately to very strongly enriched in PI, relative to local mother rock, due to the guano input from juvenile emperor penguins. Because of its high trophic level and transfer efficiency, emperor penguin can transport a large amount of nutrients and contaminants from ocean to land even with a relatively small population, and its roles in the biogeochemical cycle between ocean and terrestrial environment should not be ignored. © 2013.

  8. History and distribution of steepland gullies in response to land use change, East Coast Region, North Island, New Zealand

    Science.gov (United States)

    Marden, Michael; Arnold, Gregory; Seymour, Anne; Hambling, Randolph

    2012-06-01

    Following the clearance of indigenous forest (~ 1880s to 1920s) for pastoral use, actively eroding gullies had by the late 1950s become a pervasive form of erosion occupying 0.7% of the 7468 km2 of pastoral hill country within the East Coast Region, North Island, New Zealand. Commencing in the early 1960s the primary strategy used to stabilise gully and other associated forms of erosion on degraded pastoral hill country was to establish exotic forest. We compare the status of gully erosion before reforestation commenced with that at the end of a ~ 40 year reforestation period (1957-1997) during which ~ 1350 km2 of exotic forest was planted. Trends in gully area and distribution by land cover (vegetation), but particularly in response to exotic reforestation, are examined for two contrasting geologic terrains. Over this ~ 40 year period, the incidence and extent of gully erosion in areas of hill country that have remained in pastoral use has declined. This was primarily due to the retirement and conversion of extensive areas of gully-prone farmland to exotic forest. Where implemented, the reforestation of this degraded pastoral hill country has proven to be efficient and successful in stabilising existing gullies. However, with the initiation of new gullies and growth of gullies that have remained untreated, the extent of land affected by gully erosion has increased by ~ 27% to ~ 0.9% of the regions' hill country area. To reverse this trend, further areas of severely eroding pastoral land will need to be retired with the aim of escalating the rate at which remaining gullies are treated and to prevent new ones developing, primarily through reforestation with exotic tree species or indigenous reversion.

  9. First exposure ages from the Amundsen Sea Embayment, West Antarctica: The Late Quaternary context for recent thinning of Pine Island, Smith, and Pope Glaciers

    Science.gov (United States)

    Johnson, Joanne S.; Bentley, Michael J.; Gohl, Karsten

    2008-03-01

    Dramatic changes (acceleration, thinning, and grounding-lineretreat of major ice streams) in the Amundsen Sea sector ofthe West Antarctic Ice Sheet (WAIS) have been observed duringthe past two decades, but the millennial-scale context for thesechanges is not yet known. We present the first surface exposureages recording thinning of Pine Island, Smith, and Pope Glaciers,which all drain into the Amundsen Sea. From these we infer progressivethinning of Pine Island Glacier at an average rate of 3.8 ±0.3 cm yr-1 for at least the past 4.7 k.y., and of Smithand Pope Glaciers at 2.3 ± 0.2 cm yr-1 over thepast 14.5 k.y. These rates are more than an order of magnitudelower than the 1.6 m yr-1 recorded by satellite altimetryfor Pine Island Glacier in the period 1992-1996. Similarlylow long-term rates (2.5-9 cm yr-1 since 10 ka)have been reported farther west in the Ford Ranges, Marie ByrdLand, but in that area, the same rates of thinning continueto the present day. Our data provide the first evidence thatputs into context recent rates of thinning of the WAIS in theAmundsen Sea Embayment and demonstrates that these are unusuallyrapid. The data also provide much-needed constraints for icesheet models, which are the primary tool for predicting thefuture behavior of the WAIS and its likely contribution to sea-levelrise.

  10. 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

  11. Interior flow re-organization along the great Byrd-Totten ice divide of East Antarctica: evidence from radar layer disruptions

    Science.gov (United States)

    Cavitte, M. G. P.; Blankenship, D. D.; Young, D. A.; Siegert, M. J.; Le Meur, E.; Chappellaz, J. A.

    2012-04-01

    Interior flow re-organization is an essential component in our understanding of the temporality and magnitude of sea-level variations, especially in non-marine portions of the East Antarctic ice sheet where most of the "sea-level rise potential" is stored. Internal structure in these regions can be evaluated using internal layers from radar sounding, which can be traced over hundreds of kilometers using airborne surveys. The exceptional acuity of phase-coherent radar surveys gives both vertical resolution and horizontal continuity to radar layers that makes them extremely useful for constraining glaciological models and contributing to ice core site selection as well as understanding transient ice sheet behavior. Specifically, when well dated, these ice layers can give us high resolution snapshots into temporal and spatial ice evolution including tributary penetration of ice divides. Present areas of tributary flow reaching into the interior are well constrained through remote sensing techniques, while evidence of such transient behavior in previous glacial cycles has long since been buried by subsequent accumulation. In these cases, radar imaging is the only technique useful for identifying buried episodes of transient ice flow as anomalous yet depth consistent layer disruptions. We focus on the great Byrd-Totten ice divide in the East Antarctic interior, between the Vostok and EPICA Dome C ice core sites, to identify periods of tributary encroachment. Several layers tracked between the two sites are used to correlate their chronologies and accurately date the horizons (M. Cavitte et al, in prep.). A strong advantage in using radar for the dating of these events is its negligible contribution to age uncertainties: radar uncertainties are of the order of hundreds of years, a factor of ten smaller than traditional ice core dating techniques. Combining the age-depth stratigraphy obtained for the area and visual identifications of tributary intrusions gives a

  12. Neoarchean-Early Paleoproterozoic and Early Neoproterozoic arc magmatism in the Lützow-Holm Complex, East Antarctica: Insights from petrology, geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes

    Science.gov (United States)

    Tsunogae, Toshiaki; Yang, Qiong-Yan; Santosh, M.

    2016-10-01

    The Lützow-Holm Complex (LHC) of East Antarctica forms part of the Neoproterozoic-Cambrian high-grade metamorphic segment of the East African-Antarctic Orogen. Here we present new petrological, geochemical, and zircon U-Pb and Lu-Hf isotopic data for meta-igneous rocks including charnockite, felsic gneiss, metagabbro, and mafic granulite from the LHC and evaluate the Neoarchean to Early Paleoproterozoic (ca. 2.5 Ga) and Early Neoproterozoic (ca. 1.0 Ga) arc magmatic events. The trace element geochemical signatures reveal a volcanic arc affinity for the charnockites from Sudare Rocks and Vesleknausen and felsic gneiss from Rundvågshetta, suggesting that the protoliths of these rocks were derived from felsic arc magmas. In contrast, metagabbros from Skallevikshalsen and Austhovde, occurring as boudins in metasediments, show non-arc signatures (within-plate basalt or mid-oceanic ridge basalt). The upper intercept ages of magmatic zircons in charnockite plotted on concordia diagrams yielded 2508 ± 14 Ma (Sudare Rocks) and 2490 ± 18 Ma (Vesleknausen), clearly suggesting a Neoarchean to Early Paleoproterozoic arc magmatic event. A subsequent thermal event during Early Neoproterozoic traced by 206Pb/238U age of oscillatory-zoned core of zircon in mafic granulite from Langhovde (973 ± 10 Ma) is consistent with a similar Early Neoproterozoic magmatic event reported from the LHC, suggesting a second stage of arc magmatism. The timing of peak metamorphism has been inferred from 206Pb/238U mean ages of structureless zircons in metagabbros from Skallevikshalsen and Austhovde, mafic granulite from Langhovde, and felsic gneiss from Rundvågshetta in the range of 551 ± 5.4 to 584 ± 5.0 Ma. Zircon Lu-Hf data of Neoarchean charnockites from Sudare Rocks and Vesleknausen indicate that the protolith magma was sourced from Paleo- to Neoarchean juvenile components mixed with reworked ancient crustal materials. Protolith magmatic rock of the felsic gneiss from Rundvågshetta might

  13. Benthic Habitats of Puerto Rico and the U.S. Virgin Islands;Photomosaic of U.S. Virgin Islands (St. Croix-East), 1999

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Habitat maps of Puerto Rico and the U.S. Virgin Islands were created by visual interpretation of aerial photographs using the Habitat Digitizer Extension. Aerial...

  14. Benthic Habitats of Puerto Rico and the U.S. Virgin Islands; Photomosaic of U.S. Virgin Islands (St. Croix-East), 1999

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Habitat maps of Puerto Rico and the U.S. Virgin Islands were created by visual interpretation of aerial photographs using the Habitat Digitizer Extension. Aerial...

  15. Paleomagnetism from Deception Island (South Shetlands archipelago, Antarctica), new insights into the interpretation of the volcanic evolution using a geomagnetic model

    Science.gov (United States)

    Oliva-Urcia, B.; Gil-Peña, I.; Maestro, A.; López-Martínez, J.; Galindo-Zaldívar, J.; Soto, R.; Gil-Imaz, A.; Rey, J.; Pueyo, O.

    2016-07-01

    Deception Island shows the most recent exposed active volcanism in the northern boundary of the Bransfield Trough. The succession of the volcanic sequence in the island is broadly divided into pre- and post-caldera collapse units although a well-constrained chronological identification of the well-defined successive volcanic episodes is still needed. A new paleomagnetic investigation was carried out on 157 samples grouped in 20 sites from the volcanic deposits of Deception Island (South Shetlands archipelago, Antarctic Peninsula region) distributed in: (1) volcanic breccia (3 sites) and lavas (2 sites) prior to the caldera collapse; (2) lavas emplaced after the caldera collapse (10 sites); and (3) dikes cutting pre- and the lowermost post-caldera collapse units (5 sites). The information revealed by paleomagnetism provides new data about the evolution of the multi-episodic volcanic edifice of this Quaternary volcano, suggesting that the present-day position of the volcanic materials is close to their original emplacement position. The new data have been combined with previous paleomagnetic results in order to tentatively propose an age when comparing the paleomagnetic data with a global geomagnetic model. Despite the uncertainties in the use of averaged paleomagnetic data per volcanic units, the new data in combination with tephra occurrences noted elsewhere in the region suggest that the pre-caldera units (F1 and F2) erupted before 12,000 year BC, the caldera collapse took place at about 8300 year BC, and post-caldera units S1 and S2 are younger than 2000 year BC.

  16. Variation of Stable Isotopes in Surface Snow along a Traverse from Coast to Plateau’s interior in East Antarctica and Its Climatic Significance

    Institute of Scientific and Technical Information of China (English)

    Jean; Jouzel; Michel; Stievenard

    2009-01-01

    The variations of stable water isotopes of surface snow in east Antarctic Ice Sheet, are discussed by a total of 251 samples, which were taken along a 330 km traverse from Zhongshan Station to the outer edge of the Antarctic plateau and from four snow pits excavated along the route. Analyzing results of the samples showed the expected linear relationship between the parameters ?D and ?18O with slope S1 and intercept d1. When the data set was examined using a sliding window with a width of 5 samples, it was found that there were two areas with different ratios of S1 and d1. The boundary between these two areas occurred at an elevation of about 2,000 m, suggesting two different sources of water vapour. Nearly half (47%) of the fresh-snow samples had negative deuterium excess (d=?D? 8?18O) values, but few of the snow pit samples did, suggesting that variations of ? are quickly smoothed by isotopic diffusion in the near-surface firn. Analysis of the phase relationship between ?D and deuterium excess in the snow pit stratigraphies showed that they were mostly in phase from Jan. 1994 to Sept. 1995, but mostly out of phase from Sept. 1995 to Jan. 1997.

  17. Sounding and Imaging of Ice Sheets Over Chinese Kunlun Station and Grove Mountains From East Antarctica as a Part of Chinese National Antarctic Research Expedition

    Science.gov (United States)

    Lang, Shinan; LIu, Xiaojun; Zhao, Bo; Fang, Guangyou; Wu, Qiang

    2017-04-01

    The ice thickness, fine resolution internal reflecting horizons (IRHs) and distinct bottom topography measurements are essential information for improving the next generation ice sheet models. Radars for sounding the Antarctic inland glaciers should have high sensitivity to overcome large attenuation losses and appropriate operation frequency and bandwidth along with moderate focused synthetic aperture radar (SAR) algorithm to improve radar sensitivity and reduce along-track surface clutter. We developed a progressively improved ice-sounding radar system, currently known as the High-resolution Ice-sounding Radar (HRISR), for sounding ice sheets both on long- and short-range vehicle-mounted survey, as a part of Chinese National Antarctic Research Expedition (CHINARE). We have sounded many key areas from the East Antarctic Ice Sheets (EAIS), including two major transects over Chinese Kunlun Station and Grove Mountains. We developed two focused SAR algorithm named the modified range migration algorithm using curvelets and the modified nonlinear Chirp Scaling (CS) algorithm to effectively reduce along-track surface clutter from collected data. In this paper, we describe the radar system and algorithms, and provide sample results to demonstrate the successful sounding of the ice sheet over the Antarctic ice sheets.

  18. Mineral resources of Antarctica

    Science.gov (United States)

    Compiled and edited by Wright, Nancy A.; Williams, Paul L.

    1974-01-01

    Although the existence of mineral deposits in Antarctica is highly probable, the chances of finding them are quite small. Minerals have been found there in great variety but only as occurrences. Manganese nodules, water (as ice), geothermal energy, coal, petroleum, and natural gas are potential resources that could perhaps be exploited in the future. On the basis of known mineral occurrences in Antarctica and relationships between geologic provinces of Antarctica and those of neighboring Gondwana continents, the best discovery probability for a base-metal deposit in any part of Antarctica is in the Andean orogen; it is estimated to be 0.075 (75 chances in 1,000).

  19. 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.

  20. Hydrologic effects of artificial-recharge experiments with reclaimed water at East Meadow, Long Island, New York

    Science.gov (United States)

    Schneider, B.J.; Ku, H.F.; Oaksford, E.T.

    1987-01-01

    Artificial recharge experiments were conducted at East Meadow, Long Island, New York, from October 1982 through January 1984 to evaluate the degree of groundwater mounding and the chemical effects of artificially replenishing the groundwater system with tertiary-treated wastewater. More than 800 million gallons of treated effluent was returned to the upper glacial aquifer through recharge basins and injection wells in the 15-month period. Reclaimed water was provided by the Cedar Creek advanced wastewater treatment facility in Wantagh, 6 miles away. The chlorinated effluent was pumped to the recharge facility, where it was fed to basins by gravity flow and to injection wells by pumps. Observations during the recharge tests indicate that the two most significant factors in limiting the rate of infiltration through the basin floor were the recharge test duration and quality of reclaimed water. Head buildup in the aquifer beneath the basins ranged from 4.3 to 6.7 ft, depending on the quantity and duration of water application. Head buildup near the injection wells within the aquifer ranged from 0.3 to 1.2 ft. Recharge basins provided a more effective means of moving large quantities of reclaimed water into the aquifer than injection wells. Results of 3-day and 176-day ponding tests in two basins indicate that reclaimed water is relatively unchanged chemically by percolation through the unsaturated zone because: (1) the sand and gravel of the upper glacial aquifer is unreactive, (2) the water moves to the water table rapidly, and (3) the water is highly treated before recharge. The quality of water in the aquifer zones affected by recharge improved, on the whole. Groundwater concentrations of nitrate nitrogen and several low molecular weight hydrocarbons, decreased to well within drinking water standards as a direct result of recharge. Sodium and chloride concentrations increased above background levels as a result of recharge but remained well within drinking water

  1. 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…

  2. Grain-size features of aeolian sand on the east coast of Hainan Island and the revealed evolutionary processes of the sedimentary environment

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The Mudui stratigraphic section represents the typical records of sedimentation processes of sand dunes and interdune depressions on the east coast of Hainan Island.Based on high-density sampling and optically stimulated luminescence(OSL) dating of the strata of the section,the grain-size composition,grain-size parameters,cumulative distribution probability curve,and grain-size-sensitivity indexes(SC/D) were analyzed.The analyzed results show that the grain-size features of aeolian sand,weakly developed sandy paleosol,two-facies(aeolian and aqueous) deposits,and lagoon deposits are all different.This indicates four evolutionary phases of the sedimentary environment of the east coast of Hainan Island since 38 ka B.P.Phase I:38-22 ka B.P.;phase II:22-17 ka B.P.;phase III:17-10 ka B.P.;phase IV:10 ka B.P.-present.The climate experienced the hot-wet/hot-dry,hot-wet/hot-dry,and warm-wet/hot-wet fluctuations,and the sedimentary environment also underwent lagoon deposition,dune and interdune depression deposition,dune stabilization and soil development,shifting sand deposition,and evolutionary processes.

  3. The prevalence of multiple sclerosis in the Outer Hebrides compared with north-east Scotland and the Orkney and Shetland Islands.

    Science.gov (United States)

    Dean, G; Goodall, J; Downie, A

    1981-01-01

    Multiple sclerosis has been reported to have a high prevalence in the Orkney and Shetland Islands and in Caithness in comparison with the highlands of Scotland and the Outer Hebrides-the Western Isles. For this reason a survey was undertaken in the Outer Hebrides and 25 probable and 30 probable and possible patients with multiple sclerosis were found. This is an increase from eight and 11 respectively found in 1954. The present prevalence rate of 97.3 per 100 000 for probable and possible multiple sclerosis is not significantly different from that found in a recent study in the Grampian region in north-east Scotland. Repeated studies in small populations generally show increasing prevalence of multiple sclerosis because some patients are missed in the earlier studies, and over a long period of time there may also be some increase in survival time. This increase has been found in the Orkney and Shetland Islands, in north-east Scotland, and also in the Outer Hebrides. PMID:7299334

  4. CHANGING CHARACTERISTICS OF BACTERIAL COMMUNITIES IN SOILS IMPACTED BY PENGUIN AND SEAL EXCRETA, EAST ANTARCTICA%东南极企鹅和海豹粪土层细菌群落的变化特征

    Institute of Scientific and Technical Information of China (English)

    马大卫; 朱仁斌; 丁玮; 褚海燕; 申聪聪

    2012-01-01

    Antarctic tundra soils impacted by marine animal excreta are an important source of nutrients in these terrestrial ecosystems. Bacterial communities in the Antarctic tundra soils play an important role in carbon and nitrogen cycling. However, the changing characteristics of these bacterial communities have received little attention. In this paper, the four penguin and seal colony soil profiles (DA1, DMG and DS, HS) were collected from East Antarctica , and soil enzyme activity, microbial biomass C, microbial quotient, soil respiration, metabolic quotient, DNA concentration and qPCR were measured from all the soil horizons, and the compositions of bacterial communities were simultaneously assessed through 16S rDNA-DGGE. The objectives were to investigate the changing characteristics of soil bacterial communities and their relationships with environmental factors. Soil invertase, urease, phosphatase activities, microbial biomass, soil respiration, microbial quotient and qPCR decreased with increasing depths in the soil. However, metabolic quotient increased, indicating that the deterioration of microbial environment caused the decrease in bacterial species, quantity, and enzyme secretion. Soil DNA concentrations were significantly related with soil pH, moisture content, TOC, TN, microbial biomass C, soil respiration and enzyme activity, indicating that these environmental factors greatly affect bacterial abundance. DGGE analysis revealed a complicated bacterial community structure in East Antarctic tundra soils, and lane numbers and type brightness decreased with increasing depth. Results from cluster analysis showed that the differences between lane types were significant in four profiles with relation to soil depth and bacterial genetic similarity (46% ). In addition, bacterial communities showed a significant difference between penguin and seal colony soils. Q-factor analysis for the four soil profiles revealed that the variation in bacterial abundances highly

  5. Ecology and reproductive patterns of the agamid lizard Japalura swinhonis on an east Asian island, with comments on the small clutch sizes of island lizards.

    Science.gov (United States)

    Huang, Wen-San

    2007-02-01

    I describe the habitat use, diet, and the male and female reproductive cycles of Japalura swinhonis, an oviparous agamid lizard inhabiting Orchid Island, a tropical island off the southeastern coast of Taiwan. Ninety percent of lizards (n=126) were observed on tree trunks or at the forest edge. The diet of J. swinhonis on Orchid Island consisted mostly of hymenopterans (53.33%) and orthopterans (16.67%). The mean snout-vent length (SVL) of adult males was 74.58 (n=89) and that of females was 69.31 (n=37) mm. Females exhibited a long vitellogenic period from November to February, with parturition occurring from March to October. The onset of vitellogenesis did not correlate with the mass of the female fat bodies. Females produced two to five eggs per clutch, and clutch size was not correlated with SVL. Two clutches were recorded during a single year in some individuals. Clutch size in J. swinhonis was compared with that in other Japalura species. Clutch sizes of Japalura species are larger in mainland China than on insular Taiwan. Clutch size is also mainly affected by environmental constraints, and smaller clutch sizes are probably affected by predators on Orchid Island.

  6. Provenance, environmental and paleogeographic controls on sandstone composition in an incised-valley system: the Eocene La Meseta Formation, Seymour Island, Antarctica

    Science.gov (United States)

    Marenssi, Sergio A.; Net, Laura I.; Santillana, Sergio N.

    2002-07-01

    The Eocene La Meseta Formation is the youngest exposed unit of the back-arc James Ross Basin, Antarctic Peninsula, cropping out in Seymour (Marambio) Island. The formation comprises 720 m of clastic sedimentary rocks of deltaic, estuarine and shallow marine origin. It was subdivided into six unconformity-based units (Valle de Las Focas, Acantilados, Campamento, Cucullaea I, Cucullaea II and Submeseta Allomembers) grouped into three main facies associations. Facies association I represents valley-confined deposition in a progradational/aggradational tide-dominated and wave-influenced delta front/delta plain environment. Facies association II includes tidal channels, mixed tidal flats, tidal inlets and deltas, washover and beach environments. Facies association III represents nonconfined tide- and storm-influenced nearshore environments. La Meseta Formation sandstones are quartzofeldspathic with some hybrid arenites (glauconite and carbonate bioclasts-rich). Sandstone detrital modes are subdivided into two distinctive petrofacies: the low quartz petrofacies (petrofacies I, Q12%), interpreted to retain the original provenance signal, and the high quartz petrofacies (petrofacies II, Q>55% and L1.4) is clearly dominated by volcanic-derived clasts; it developed at times of high sea level and/or during later stages of the valley fill, when an "energy fence" at the shoreline prevented delivery of sediment from the Antarctic Peninsula, thus enhancing the relative participation of local volcanic sources.

  7. Potential methane reservoirs beneath Antarctica.

    Science.gov (United States)

    Wadham, J L; Arndt, S; 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

    2012-08-30

    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 evaluated. Large sedimentary basins containing marine sequences up to 14 kilometres thick and an estimated 21,000 petagrams (1 Pg equals 10(15) g) of organic carbon are buried beneath the Antarctic Ice Sheet. No data exist for rates of methanogenesis in sub-Antarctic marine sediments. Here we present experimental data from other subglacial environments that demonstrate the potential for overridden organic matter beneath glacial systems to produce methane. We also numerically simulate the accumulation of methane in Antarctic sedimentary basins using an established one-dimensional hydrate model and show that pressure/temperature conditions favour methane hydrate formation down to sediment depths of about 300 metres in West Antarctica and 700 metres in East Antarctica. Our results demonstrate the potential for methane hydrate accumulation in Antarctic sedimentary basins, where the total inventory depends on rates of organic carbon degradation and conditions at the ice-sheet bed. We calculate that the sub-Antarctic hydrate inventory could be of the same order of magnitude as that of recent estimates made for Arctic permafrost. Our findings suggest that the Antarctic Ice Sheet may be a neglected but important component of the global methane budget, with the potential to act as a positive feedback on climate warming during ice-sheet wastage.

  8. 东南极洲Lambert冰川流域半个多世纪以来气候变化特征%The Features of the Climate Change in the Pa st 50 Years in the Lambert Glacier Basin, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    张明军; 李忠勤; 秦大河; 效存德; 杨惠安; 康建成; 李军

    2001-01-01

    The upper 13 meters of t he 50-meter firn core drilled along theroute of the 1996/1997 Chinese First An tarctic Inland Expedition in the eastern part of the Lambert Glacier Basin, East Antarctica, has been measured for δ18O and the rate of accumula tion. The features of the climate change in the past 50 years in the studied reg ion have been shown for the first time. In the past 50 years, the whole climate trends in the region were the warming temperature and the increasing precipitati on. On the contrary, the temperature trend of the western part of the Lambert Gl acier Basin was not so clear in the same period. The precipitation trend of the region was clearly decreasing, which indicates the climate changes of the whole Lambert Glacier Basin were different in the different regions. At the same time, the study of the correlation between stable isotope ratios and temperature show s that the δ-temperature gradients were different between the eastern part and the western part of the Lambert Glacier Basin.%通过对1996/1997年中国首次南极内陆冰盖考察获得的东南极洲Lambert冰川流域东侧50m雪芯,顶部13m的δ18O资料的分析和积累率的恢复,首次揭示了Lambert冰川流域东侧半个多世纪以来的气候变化特征,即半个多世纪以来气候变化的总趋势为气温升高、降水增加.而Lambert冰川流域西侧雪芯资料表明,本地区半个多世纪以来气温变化趋势不明显,降水明显减少,说明整个Lambert冰川流域20世纪40年代以来气候变化有明显的区域差异性.同时研究了Lambert冰川流域东西两侧稳定同位素比率和温度的关系.

  9. Benthic Habitats of Puerto Rico and the U.S. Virgin Islands; Photomosaic of Puerto Rico (East Culebra), 1999

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Habitat maps of Puerto Rico and the U.S. Virgin Islands were created by visual interpretation of aerial photographs using the Habitat Digitizer Extension. Aerial...

  10. A Carbon Cycle Model for the Social-Ecological Process in Coastal Wetland: A Case Study on Gouqi Island, East China.

    Science.gov (United States)

    Li, Yanxia; Xiong, Lihu; Zhu, Wenjia

    2017-01-01

    Coastal wetlands offer many important ecosystem services both in natural and in social systems. How to simultaneously decrease the destructive effects flowing from human activities and maintaining the sustainability of regional wetland ecosystems are an important issue for coastal wetlands zones. We use carbon credits as the basis for regional sustainable developing policy-making. With the case of Gouqi Island, a typical coastal wetlands zone that locates in the East China Sea, a carbon cycle model was developed to illustrate the complex social-ecological processes. Carbon-related processes in natural ecosystem, primary industry, secondary industry, tertiary industry, and residents on the island were identified in the model. The model showed that 36780 tons of carbon is released to atmosphere with the form of CO2, and 51240 tons of carbon is captured by the ecosystem in 2014 and the three major resources of carbon emission are transportation and tourism