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Sample records for high antarctic plateau

  1. Snow surface microbiome on the High Antarctic Plateau (DOME C.

    Directory of Open Access Journals (Sweden)

    Luigi Michaud

    Full Text Available The cryosphere is an integral part of the global climate system and one of the major habitable ecosystems of Earth's biosphere. These permanently frozen environments harbor diverse, viable and metabolically active microbial populations that represent almost all the major phylogenetic groups. In this study, we investigated the microbial diversity in the surface snow surrounding the Concordia Research Station on the High Antarctic Plateau through a polyphasic approach, including direct prokaryotic quantification by flow cytometry and catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH, and phylogenetic identification by 16S RNA gene clone library sequencing and 454 16S amplicon pyrosequencing. Although the microbial abundance was low (<10(3 cells/ml of snowmelt, concordant results were obtained with the different techniques. The microbial community was mainly composed of members of the Alpha-proteobacteria class (e.g. Kiloniellaceae and Rhodobacteraceae, which is one of the most well-represented bacterial groups in marine habitats, Bacteroidetes (e.g. Cryomorphaceae and Flavobacteriaceae and Cyanobacteria. Based on our results, polar microorganisms could not only be considered as deposited airborne particles, but as an active component of the snowpack ecology of the High Antarctic Plateau.

  2. Optical Turbulence above the Internal Antarctic Plateau

    CERN Document Server

    Masciadri, E; Hagelin, S; Moigne, P Le; Noilhan, J

    2010-01-01

    The internal antarctic plateau revealed in the last years to be a site with interesting potentialities for the astronomical applications due to the extreme dryness and low temperatures, the typical high altitude of the plateau, the weak level of turbulence in the free atmosphere down to a just few tens of meters from the ground and the thin optical turbulence layer developed at the ground. The main goal of a site testing assessment above the internal antarctic plateau is to characterize the site (optical turbulence and classical meteorological parameters) and to quantify which is the gain we might obtain with respect to equivalent astronomical observations done above mid-latitude sites to support plans for future astronomical facilities. Our group is involved, since a few years, in studies related to the assessment of this site for astronomical applications that include the characterization of the meteorological parameters and optical turbulence provided by general circulation models as well as mesoscale atmo...

  3. Millimetric Astronomy from the High Antarctic Plateau site testing at Dome C

    CERN Document Server

    Valenziano, L

    1999-01-01

    Preliminary site testing at Dome C (Antarctica) is presented, using both Automatic Weather Station (AWS) meteorological data (1986-1993) and Precipitable Water Vapor (PWV) measurements made by the authors. A comparison with South Pole and other sites is made. The South Pole is a well established astrophysical observing site, where extremely good conditions are reported for a large fraction of time during the year. Dome C, where Italy and France are building a new scientific station, is a potential observing site in the millimetric and sub-millimetric range. AWS are operating at both sites and they have been continuously monitoring temperature, pressure, wind speed and direction for more than ten years. Site testing instruments are already operating at the South Pole (AASTO, Automated Astrophysical Site-Testing Observatory), while ''light'' experiments have been running at Dome C (APACHE, Antarctic Plateau Anisotropy CHasing Experiment) during summertime. A direct comparison between the two sites is planned in...

  4. Characterization of culturable Paenibacillus spp. from the snow surface on the high Antarctic Plateau (DOME C) and their dissemination in the Concordia research station.

    Science.gov (United States)

    Van Houdt, Rob; Deghorain, Marie; Vermeersch, Marjorie; Provoost, Ann; Lo Giudice, Angelina; Leys, Natalie; Perez-Morga, David; Van Melderen, Laurence; Michaud, Luigi

    2013-07-01

    Culturable psychrotolerant bacteria were isolated from the top snow on the high Antarctic Plateau surrounding the research station Concordia. A total of 80 isolates were recovered, by enrichment cultures, from two different isolation sites (a distant pristine site [75° S 123° E] and a site near the secondary runway of Concordia). All isolates were classified to the genus Paenibacillus by 16S rRNA gene phylogenetic analysis and belonged to two different species (based on threshold of 97 % similarity in 16S rRNA gene sequence). ERIC-PCR fingerprinting indicated that the isolates from the two different sites were not all clonal. All isolates grew well from 4 to 37 °C and were resistant to ampicillin and streptomycin. In addition, the isolates from the secondary runway were resistant to chromate and sensitive to chloramphenicol, contrary to those from the pristine site. The isolates were compared to 29 Paenibacillus isolates, which were previously recovered from inside the Concordia research station. One of these inside isolates showed ERIC- and REP-PCR fingerprinting profiles identical to those of the runway isolates and was the only inside isolate that was resistant to chromate and sensitive to chloramphenicol. The latter suggested that dissemination of culturable Paenibacillus strains between the harsh Antarctic environment and the inside of the Concordia research station occurred. In addition, inducible prophages, which are potentially involved in horizontal dissemination of genes, were detected in Paenibacillus isolates recovered from outside and inside the station. The highest lysogeny was observed in strains harvested from the hostile environment outside the station.

  5. Concordia: The New Permanent Research Support Facility on the Antarctic plateau

    Science.gov (United States)

    Godon, P.; Jugie, G.; Frénot, Y.; Cucinotta, A.

    Concordia has been the third permanent station inland the Antarctic continent since February 2005. It was built jointly by France and Italy in order to offer to the scientific community a platform for research on the antarctic plateau, high in altitude. After the very successful drilling programme EPICA at Dome C, an European project gathering 10 countries and offering the oldest accurate climate archive, many other field of science will benefit from the exceptional properties of the site, namely astronomical researches. This paper provides information on these properties and on the current facilities in terms of building and transport. In addition, it points out the environmental protection and waste management in force at Concordia, in agreement with the Antarctic Treaty and Madrid Protocol.

  6. Net deposition of mercury to the Antarctic Plateau enhanced by sea salt.

    Science.gov (United States)

    Han, Yeongcheol; Huh, Youngsook; Hur, Soon Do; Hong, Sungmin; Chung, Ji Woong; Motoyama, Hideaki

    2017-04-01

    Photochemically driven mercury (Hg) exchange between the atmosphere and the Antarctic Plateau snowpack has been observed. An imbalance in bidirectional flux causes a fraction of Hg to remain in the snowpack perennially, but the factors that control the amount of Hg sequestered on the Antarctic Plateau are not fully understood. We analyzed sub-annual variations in total Hg (HgT) deposition to Dome Fuji over the period of 1986-2010 using cold vapor inductively coupled plasma mass spectrometry and compared concentrations with those of sea salt components (Na(+) and Cl(-)). HgT ranged from 0.12 to 5.19pgg(-1) (n=78) and was relatively high when the Na(+) concentrations were high in the same or underlying snow layers. A significant correlation (r=0.7) was found between the annual deposition fluxes of HgT and Na(+). Despite different origins and behavior of Hg and sea salt, the near-synchronous increases in the concentrations and correlation between the fluxes suggest that sea salt can intervene in the air-snow Hg exchange and promote the net deposition of Hg in the Antarctic Plateau.

  7. Atmospheric moisture supersaturation in the near-surface atmosphere at Dome C, Antarctic Plateau

    Science.gov (United States)

    Genthon, Christophe; Piard, Luc; Vignon, Etienne; Madeleine, Jean-Baptiste; Casado, Mathieu; Gallée, Hubert

    2017-01-01

    Supersaturation often occurs at the top of the troposphere where cirrus clouds form, but is comparatively unusual near the surface where the air is generally warmer and laden with liquid and/or ice condensation nuclei. One exception is the surface of the high Antarctic Plateau. One year of atmospheric moisture measurement at the surface of Dome C on the East Antarctic Plateau is presented. The measurements are obtained using commercial hygrometry sensors modified to allow air sampling without affecting the moisture content, even in the case of supersaturation. Supersaturation is found to be very frequent. Common unadapted hygrometry sensors generally fail to report supersaturation, and most reports of atmospheric moisture on the Antarctic Plateau are thus likely biased low. The measurements are compared with results from two models implementing cold microphysics parameterizations: the European Center for Medium-range Weather Forecasts through its operational analyses, and the Model Atmosphérique Régional. As in the observations, supersaturation is frequent in the models but the statistical distribution differs both between models and observations and between the two models, leaving much room for model improvement. This is unlikely to strongly affect estimations of surface sublimation because supersaturation is more frequent as temperature is lower, and moisture quantities and thus water fluxes are small anyway. Ignoring supersaturation may be a more serious issue when considering water isotopes, a tracer of phase change and temperature, largely used to reconstruct past climates and environments from ice cores. Because observations are easier in the surface atmosphere, longer and more continuous in situ observation series of atmospheric supersaturation can be obtained than higher in the atmosphere to test parameterizations of cold microphysics, such as those used in the formation of high-altitude cirrus clouds in meteorological and climate models.

  8. Excellent daytime seeing at Dome Fuji on the Antarctic plateau

    CERN Document Server

    Okita, H; Ashley, M C B; Takato, N

    2013-01-01

    Context. Dome Fuji, the second highest region on the Antarctic plateau, is expected to have some of the best astronomical seeing on Earth. However, site testing at Dome Fuji is still in its very early stages. Aims. To investigate the astronomical seeing in the free atmosphere above Dome Fuji, and to determine the height of the surface boundary layer. Methods. A Differential Image Motion Monitor was used to measure the seeing in the visible (472 nm) at a height of 11 m above the snow surface at Dome Fuji during the austral summer of 2012/2013. Results. Seeing below 0.2'' has been observed. The seeing often has a local minimum of ~0.3'' near 18 h local time. Some periods of excellent seeing, 0.3'' or smaller, were also observed, sometimes extending for several hours at local midnight. The median seeing is higher, at 0.52''---this large value is believed to be caused by periods when the telescope was within the turbulent boundary layer. Conclusions. The diurnal variation of the daytime seeing at Dome Fuji is sim...

  9. Meso-Nh simulations of the atmospheric flow above the Internal Antarctic Plateau

    CERN Document Server

    Lascaux, Franck; Hagelin, Susanna; Stoesz, Jeffrey A; 10.1117/12.787571

    2010-01-01

    Mesoscale model such as Meso-Nh have proven to be highly reliable in reproducing 3D maps of optical turbulence (see Refs. 1, 2, 3, 4) above mid-latitude astronomical sites. These last years ground-based astronomy has been looking towards Antarctica. Especially its summits and the Internal Continental Plateau where the optical turbulence appears to be confined in a shallow layer close to the icy surface. Preliminary measurements have so far indicated pretty good value for the seeing above 30-35 m: 0.36" (see Ref. 5) and 0.27" (see Refs. 6, 7) at Dome C. Site testing campaigns are however extremely expensive, instruments provide only local measurements and atmospheric modelling might represent a step ahead towards the search and selection of astronomical sites thanks to the possibility to reconstruct 3D Cn2 maps over a surface of several kilometers. The Antarctic Plateau represents therefore an important benchmark test to evaluate the possibility to discriminate sites on the same plateau. Our group8 has proven ...

  10. The Concordia Station on the Antarctic Plateau: The Best Site on Earth for the 21st Century Astronomers

    Indian Academy of Sciences (India)

    Eric Fossat

    2005-06-01

    On the Antarctic plateau, a joint project of French and Italian polar programmes is nearing completion: the Concordia station will be open for winter-over operation in 2005. The high altitude and high latitude of this site, the exceptionally cold, clear and stable atmosphere, its incredible astronomical seeing, the almost indefinitely flat snow surface and the notso-difficult access make this site the most promising on Earth for future ground-based astronomical projects in various fields, including long term photometry, infrared high sensitivity imaging and high angular resolution and high contrast imaging.

  11. PLATO - the next-generation AASTINO for robotic site-testing on the Antarctic plateau

    Science.gov (United States)

    Hengst, S.; Lawrence, J.; Luong-van, D.; Everett, J.; Ashley, M. C. B.; Storey, J. W. V.; Hall, S.

    2006-08-01

    A new site-testing facility, PLATO (Plateau Observatory), is under development at UNSW for deployment to remote sites on the Antarctic Plateau including Dome A. The new facility will adopt many of the features of the AASTINO (Automated Astrophysical Site Testing InterNational Observatory) facility at Dome C. PLATO will autonomously control a flexible site testing and observing instrument suite, monitored via the Iridium satellite network. A challenging aspect of PLATO is to maximise the reliability of the power source while minimising fuel consumption. We are building a low pressure, low temperature environmental chamber to simulate operation at the highest altitudes (4,100 m at Dome A). Two types of engines will be tested: a single-cylinder diesel engine and a Stirling engine.

  12. Estimating the climate variability of the last millennium on the East Antarctic plateau

    Science.gov (United States)

    Münch, Thomas; Laepple, Thomas

    2016-04-01

    Quantitative knowledge about the climate variability on the Antarctic continent is crucial to attribute and detect the anthropogenic influence, and to understand the past and future evolution of the Antarctic ice sheet. Isotope records from firn and ice cores provide information about Holocene climate variability but strong non-climate effects hamper their quantitative interpretation, especially in low-accumulation regions. So far, the magnitude and time-scale dependency of both the climate signal and the noise is largely unknown. Here, we combine 16 annually-resolved firn cores spanning the last 200 years, three records covering the last millennium as well as surface snow data from the Amundsenisen region on the East Antarctic plateau. By means of a spectral correction technique we can separate the climate signal from noise and derive, for the first time, a time-scale dependent estimate of East-Antarctic temperature variability. Our preliminary results indicate that, unlike the raw isotope data, the obtained temperature variability for our study region shows a scaling behavior with more variability on longer time scales, similar to estimates from marine SST records. The noise levels we find are in accordance with the independent surface snow sampling results from Kohnen station. An analysis of the variability in current climate models on the other hand suggests less variability on centennial time scales. The discrepancy between the model and data-based results indicates either deficiencies in the model simulations, or further unknown processes affecting the ice-core records. Our estimate of East-Antarctic climate variability thus highlights the importance of an improved understanding of Holocene climate and ice-core derived variability.

  13. [Study of blood oxygen saturation, heart rate changes and plateau reaction of the Antarctic Kunlun station investigation team in different plateau environments].

    Science.gov (United States)

    Zhao, Shun-yun; Wu, Xin-min; Guo, Ya-min; Zhang, Shu-shun; An, Yan-ming; Li, Bing; Wang, Hao

    2013-06-11

    To explore the blood oxygen saturation and heart rate changes of the Antarctic explorers. During August 2010 to April 2011, the changes in blood oxygen saturation, heart rate and plateau reaction of 16 Antarctic expedition team in different plateau environments (Tibetan plateau versus Antarctic plateau) were monitored with the noninvasive pulse oximeter MD300-C. The extent of acute mountain sickness was determined according to the Lake Louise Consensus acute mountain reaction symptom scores and judgment method. The changes of blood oxygen saturation, heart rate at different altitudes of 110, 3650, 4300 m (96.8% ± 1.2%,89.1% ± 1.2%, 86.1% ± 2.0%, (75.0 ± 5.4) times/min, (104.0 ± 4.3) times/min, (113.0 ± 5.2) times/min,F = 214.155, 240.088,both P blood oxygen saturation, heart rate at different altitudes of 2000, 2500, 3000, 3500 and 4087 m(91.9% ± 1.3%,90.5% ± 1.3%,87.6% ± 1.4%,85.0% ± 1.8%,81.5% ± 2.2%, (85.9 ± 3.2) times/min, (90.6 ± 2.8) times/min, (97.8 ± 4.1) times/min, (102.0 ± 3.4) times/min, (106.3 ± 3.9) times/min, F = 105.418, 90.174, both P blood oxygen saturation and heart rate were both correlated with the risk of altitude sickness (r = -0.446 and 0.565, both P heart rate of the Antarctic explorers. And with the increases of altitude, the risk of altitude sickness gradually increases.

  14. Comparative study on PCDD/F pollution in soil from the Antarctic, Arctic and Tibetan Plateau.

    Science.gov (United States)

    Jia, Shenglan; Wang, Qiang; Li, Li; Fang, Xuekun; Shi, Yehong; Xu, Weiguang; Hu, Jianxin

    2014-11-01

    The concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in 35 soil samples collected from Fildes Peninsula in the Antarctic, Ny-Ålesund in the Arctic, and Zhangmu-Nyalam in the Tibetan Plateau were reported in this study. A comparison of the total concentration and TEQ of PCDD/Fs at the Three Poles was conducted. Both the total concentration and TEQ of PCDD/Fs demonstrates a decreasing trend in the order of Zhangmu-Nyalam (mean: 26.22 pg/g, 0.37 pg I-TEQ/g)>Ny-Ålesund (mean: 9.97 pg/g, 0.33 pg I-TEQ/g)>Fildes Peninsula (mean: 2.18 pg/g, 0.015 pg I-TEQ/g) (p<0.05). In all samples, the congener and homologue profiles dominated with higher (seven and eight) chlorinated PCDD/Fs (more than 85% of the total mass percentage of PCDD/Fs) at the Three Poles. Finally, a FLEXPART backward simulation was used to preliminarily identify the potential local and regional anthropogenic sources of PCDD/Fs. The results imply that the air masses passing over surrounding regions with significant PCDD/F emissions might contribute to the occurrence of PCDD/Fs in both the Arctic and Tibetan Plateau. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Satellite remote sensing of the island mass effect on the Sub-Antarctic Kerguelen Plateau, Southern Ocean

    Science.gov (United States)

    Jena, Babula

    2016-09-01

    The presence of the Kerguelen Plateau and surrounding bathymetric features has a strong influence on the persistently eastward flowing Antarctic Circumpolar Current (ACC), resulting in enhancement of surface chlorophyll-a (Chl- a) in the downstream section of the plateau along the polar front (PF). The phenomenon is reported in this paper as the island mass effect (IME). Analysis of climatological Chl- a datasets from Aqua- Moderate Resolution Imaging Spectroradiometer (Aqua- MODIS) and Sea-viewing Wide Field-of-view Sensor (SeaWiFS) shows distinct bloomy plumes (Chl- a>0.5 mg/m3) during austral spring-summer spreading as far as ~1800 km offshore up to 98°E along the downstream of the north Kerguelen Plateau (NKP). Similar IME phenomena is apparent over the south Kerguelen Plateau (SKP) with the phytoplankton bloom extending up to 96.7°E, along the southern boundary of ACC. The IME phenomena are pronounced only during austral spring-summer period with the availability of light and sedimentary source of iron from shallow plateau to sea surface that fertilizes the mixed layer. The NKP bloom peaks with a maximum areal extent of 1.315 million km2 during December, and the SKP bloom peaks during January with a time lag of one month. The blooms exist for at least 4 months of a year and are significant both as the base of regional food web and for regulating the biogeochemical cycle in the Southern Ocean. Even though the surface water above the Kerguelen Plateau is rich in Chl- a, an exception of an oligotrophic condition dominated between NKP and SKP due to apparent intrusion of iron limited low phytoplankton regime waters from the Enderby basin through the northeastward Fawn Trough Current.

  16. A one-dimensional heat transfer model of the Antarctic Ice Sheet and modeling of snow temperatures at Dome A, the summit of Antarctic Plateau

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A vertical one-dimensional numerical model for heat transferring within the near-surface snow layer of the Antarctic Ice Sheet was developed based on simplified parameterizations of associated physical processes for the atmosphere, radiation, and snow/ice systems. Using the meteorological data of an automatic weather station (AWS) at Dome A (80°22′S, 70°22′E), we applied the model to simulate the seasonal temperature variation within a depth of 20 m. Comparison of modeled results with observed snow temperatures at 4 measurement depths (0.1, 1, 3, 10 m) shows good agreement and consistent seasonal variations. The model results reveal the vertical temperature structure within the near-surface snow layer and its seasonal variance with more details than those by limited measurements. Analyses on the model outputs of the surface energy fluxes show that: 1) the surface energy balance at Dome A is characterized by the compensation between negative net radiation and the positive sensible fluxes, and 2) the sensible heat is on average transported from the atmosphere to the snow, and has an evident increase in spring. The results are considered well representative for the highest interior Antarctic Plateau.

  17. Borehole temperatures reveal details of 20th century warming at Bruce Plateau, Antarctic Peninsula

    Directory of Open Access Journals (Sweden)

    V. Zagorodnov

    2011-11-01

    Full Text Available Two ice core boreholes of 143.74 m and 447.65 m (bedrock were drilled during the 2009–2010 austral summer on the Bruce Plateau at a location named LARISSA Site Beta (66°02' S, 64°04' W, 1975.5 m a.s.l.. Both boreholes were logged with thermistors shortly after drilling. The shallow borehole was instrumented for 4 months with a series of resistance thermometers with satellite uplink. Surface temperature proxy data derived from an inversion of the borehole temperature profiles are compared to available multi-decadal records from weather stations and ice cores located along a latitudinal transect of the Antarctic Peninsula to West Antarctica. The LARISSA Site Beta profiles show temperatures decreasing from the surface downward through the upper third of the ice, and warming thereafter to the bed. The average temperature for the most recent year is −14.78 °C (measured at 15 m depth, abbreviated T15. A minimum temperature of −15.8 °C is measured at 173 m depth and basal temperature is estimated to be −10.2 °C. Current mean annual temperature and the gradient in the lower part of the measured temperature profile have a best fit with an accumulation rate of 1.9 × 103 kg m−2 a−1 and basal heat flux (q of 88 mW m−2, if steady-state conditions are assumed. However, the mid-level temperature variations show that recent temperature has varied significantly. Reconstructed surface temperatures (Ts=T15 over the last 200 yr are derived by an inversion technique. From this, we find that cold temperatures (minimum Ts=−16.2 °C prevailed from ~1920 to ~1940, followed by a gradual rise of temperature to −14.2 °C around 1995, then cooling over the following decade and warming in the last few years. The coldest period was preceded by a relatively warm 19th century at T15 ≥ −15 °C. To facilitate

  18. Borehole temperatures reveal details of 20th century warming at Bruce Plateau, Antarctic Peninsula

    Directory of Open Access Journals (Sweden)

    V. Zagorodnov

    2012-06-01

    Full Text Available Two ice core boreholes of 143.18 m and 447.73 m (bedrock were drilled during the 2009–2010 austral summer on the Bruce Plateau at a location named LARISSA Site Beta (66°02' S, 64°04' W, 1975.5 m a.s.l.. Both boreholes were logged with thermistors shortly after drilling. The shallow borehole was instrumented for 4 months with a series of resistance thermometers with satellite uplink. Surface temperature proxy data derived from an inversion of the borehole temperature profiles are compared to available multi-decadal records from weather stations and ice cores located along a latitudinal transect of the Antarctic Peninsula to West Antarctica. The LARISSA Site Beta profiles show temperatures decreasing from the surface downward through the upper third of the ice, and warming thereafter to the bed. The average temperature for the most recent year is −14.78°C (measured at 15 m depth, abbreviated T15. A minimum temperature of −15.8°C is measured at 173 m depth, and basal temperature is estimated to be −10.2°C. Current mean annual temperature and the gradient in the lower part of the measured temperature profile have a best fit with an accumulation rate of 1.9×103 kg m−2 a−1 and basal heat flux (q of 88 mW m−2, if steady-state conditions are assumed. However, the mid-level temperature variations show that recent temperature has varied significantly. Reconstructed surface temperatures (Ts=T15 over the last 200 yr are derived by an inversion technique (Tikhonov and Samarskii, 1990. From this, we find that cold temperatures (minimum Ts=−16.2°C prevailed from ~1920 to ~1940, followed by a gradual rise of temperature to −14.2°C around 1995, then cooling over the following decade and warming in the last few years. The coldest period was preceded by a relatively warm 19th century at T15≥−15

  19. Deep Radiostratigraphy of the East Antarctic Plateau: Connecting the Dome C and Vostok Ice Core Sites

    Science.gov (United States)

    Cavitte, Marie G. P.; Blankenship, Donald D.; Young, Duncan A.; Schroeder, Dustin M.; Parrenin, Frederic; Lemeur, Emmanuel; Macgregor, Joseph A.; Siegert, Martin J.

    2016-01-01

    Several airborne radar-sounding surveys are used to trace internal reflections around the European Project for Ice Coring in Antarctica Dome C and Vostok ice core sites. Thirteen reflections, spanning the last two glacial cycles, are traced within 200 km of Dome C, a promising region for million-year-old ice, using the University of Texas Institute for Geophysics High-Capacity Radar Sounder. This provides a dated stratigraphy to 2318 m depth at Dome C. Reflection age uncertainties are calculated from the radar range precision and signal-to-noise ratio of the internal reflections. The radar stratigraphy matches well with the Multichannel Coherent Radar Depth Sounder (MCoRDS) radar stratigraphy obtained independently. We show that radar sounding enables the extension of ice core ages through the ice sheet with an additional radar-related age uncertainty of approximately 1/3-1/2 that of the ice cores. Reflections are extended along the Byrd-Totten Glacier divide, using University of Texas/Technical University of Denmark and MCoRDS surveys. However, core-to-core connection is impeded by pervasive aeolian terranes, and Lake Vostok's influence on reflection geometry. Poor radar connection of the two ice cores is attributed to these effects and suboptimal survey design in affected areas. We demonstrate that, while ice sheet internal radar reflections are generally isochronal and can be mapped over large distances, careful survey planning is necessary to extend ice core chronologies to distant regions of the East Antarctic ice sheet.

  20. Uncertainty Estimates of NASA Satellite LST over the Greenland and Antarctic Plateau: 2003-2015

    Science.gov (United States)

    Knuteson, R.; Borbas, E. E.; Burgess, G.

    2015-12-01

    Jin and Dickinson (2010) identify three reasons why LST has not been adopted as a climate variable. Paraphrasing the authors, the three roadblocks for use of satellite LST products in climate studies are; 1) unknown accuracy (What are surface emissivity and atmospheric correction uncertainties?)2) spatial scale ambiguity (Are satellite footprints too large to be physically meaningful?)3) lack of consistency over decadal time scales (How far backward/forward can we go in time?). These issues apply particularly to the cryosphere where the lack of surface measurement sites make the proper use of satellite observations critical for monitoring climate change. This paper will address each of these three issues but with a focus on the high and dry Greenland and Antarctic plateaus and the contrast in trends between the two. Recent comparisons of MODIS LST products with AIRS version 6 LST products show large differences over Greenland (Lee et al. 2014). In this paper we take the logical next step of creating a bottoms up uncertainty budget for a new synergistic AIRS/MODIS LST product for ice and snow conditions. This new product will address the issue of unknown accuracy by providing a local LST uncertainty along with each estimate of surface temperature. The combination of the high spatial resolution of the MODIS and the high spectral resolution of the AIRS observations of radiance allow the combination of the two sensors to provide information with lower uncertainty than what is possible from the current separate operational products. The issue of surface emissivity and atmospheric correction uncertainties will be addressed explicitly using spectrally resolved models that cover the infrared region. The issue of spatial scale ambiguity is overcome by creating a classification of the results based on the spatial homogenity of surface temperatures. The issue of lack of consistency over long time scales is addressed by demonstrating an algorithm using collocated NASA MODIS

  1. Interpretation of Plateau in High-Harmonic Generation

    Institute of Scientific and Technical Information of China (English)

    程太旺; 李晓峰; 敖淑艳; 傅盘铭

    2003-01-01

    The plateau in high-harmonic generation is investigated in the frequency domain. Probability density of an electron in an electromagnetic field is obtained through analysing the quantized-field Volkov state. The plateau of high-harmonic generation reflects the spectral density of the electron at the location of nucleus after abovethreshold ionization.

  2. Air-snow transfer of nitrate on the East Antarctic Plateau - Part 2: An isotopic model for the interpretation of deep ice-core records

    Science.gov (United States)

    Erbland, J.; Savarino, J.; Morin, S.; France, J. L.; Frey, M. M.; King, M. D.

    2015-10-01

    Unraveling the modern budget of reactive nitrogen on the Antarctic Plateau is critical for the interpretation of ice-core records of nitrate. This requires accounting for nitrate recycling processes occurring in near-surface snow and the overlying atmospheric boundary layer. Not only concentration measurements but also isotopic ratios of nitrogen and oxygen in nitrate provide constraints on the processes at play. However, due to the large number of intertwined chemical and physical phenomena involved, numerical modeling is required to test hypotheses in a quantitative manner. Here we introduce the model TRANSITS (TRansfer of Atmospheric Nitrate Stable Isotopes To the Snow), a novel conceptual, multi-layer and one-dimensional model representing the impact of processes operating on nitrate at the air-snow interface on the East Antarctic Plateau, in terms of concentrations (mass fraction) and nitrogen (δ15N) and oxygen isotopic composition (17O excess, Δ17O) in nitrate. At the air-snow interface at Dome C (DC; 75° 06' S, 123° 19' E), the model reproduces well the values of δ15N in atmospheric and surface snow (skin layer) nitrate as well as in the δ15N profile in DC snow, including the observed extraordinary high positive values (around +300 ‰) below 2 cm. The model also captures the observed variability in nitrate mass fraction in the snow. While oxygen data are qualitatively reproduced at the air-snow interface at DC and in East Antarctica, the simulated Δ17O values underestimate the observed Δ17O values by several per mill. This is explained by the simplifications made in the description of the atmospheric cycling and oxidation of NO2 as well as by our lack of understanding of the NOx chemistry at Dome C. The model reproduces well the sensitivity of δ15N, Δ17O and the apparent fractionation constants (15ϵapp, 17Eapp) to the snow accumulation rate. Building on this development, we propose a framework for the interpretation of nitrate records

  3. Antarctic marine gravity field from high-density satellite altimetry

    Science.gov (United States)

    Sandwell, David T.

    1992-01-01

    High-density (about 2-km profile spacing) Geosat/GM altimetry profiles were obtained for Antarctic waters (6-deg S to 72 deg S) and converted to vertical gravity gradient, using Laplace's equation to directly calculate gravity gradient from vertical deflection grids and Fourier analysis to construct gravity anomalies from two vertical deflection grids. The resultant gravity grids have resolution and accuracy comparable to shipboard gravity profiles. The obtained gravity maps display many interesting and previously uncharted features, such as a propagating rift wake and a large 'leaky transform' along the Pacific-Antarctic Rise.

  4. Continuous measurements of isotopic composition of water vapour on the East Antarctic Plateau

    Science.gov (United States)

    Casado, Mathieu; Landais, Amaelle; Masson-Delmotte, Valérie; Genthon, Christophe; Kerstel, Erik; Kassi, Samir; Arnaud, Laurent; Picard, Ghislain; Prie, Frederic; Cattani, Olivier; Steen-Larsen, Hans-Christian; Vignon, Etienne; Cermak, Peter

    2016-07-01

    Water stable isotopes in central Antarctic ice cores are critical to quantify past temperature changes. Accurate temperature reconstructions require one to understand the processes controlling surface snow isotopic composition. Isotopic fractionation processes occurring in the atmosphere and controlling snowfall isotopic composition are well understood theoretically and implemented in atmospheric models. However, post-deposition processes are poorly documented and understood. To quantitatively interpret the isotopic composition of water archived in ice cores, it is thus essential to study the continuum between surface water vapour, precipitation, surface snow and buried snow. Here, we target the isotopic composition of water vapour at Concordia Station, where the oldest EPICA Dome C ice cores have been retrieved. While snowfall and surface snow sampling is routinely performed, accurate measurements of surface water vapour are challenging in such cold and dry conditions. New developments in infrared spectroscopy enable now the measurement of isotopic composition in water vapour traces. Two infrared spectrometers have been deployed at Concordia, allowing continuous, in situ measurements for 1 month in December 2014-January 2015. Comparison of the results from infrared spectroscopy with laboratory measurements of discrete samples trapped using cryogenic sampling validates the relevance of the method to measure isotopic composition in dry conditions. We observe very large diurnal cycles in isotopic composition well correlated with temperature diurnal cycles. Identification of different behaviours of isotopic composition in the water vapour associated with turbulent or stratified regime indicates a strong impact of meteorological processes in local vapour/snow interaction. Even if the vapour isotopic composition seems to be, at least part of the time, at equilibrium with the local snow, the slope of δD against δ18O prevents us from identifying a unique origin leading

  5. Joint Antarctic School Expedition - An International Collaboration for High School Students and Teachers on Antarctic Science

    Science.gov (United States)

    Botella, J.; Warburton, J.; Bartholow, S.; Reed, L. F.

    2014-12-01

    The Joint Antarctic School Expedition (JASE) is an international collaboration program between high school students and teachers from the United States and Chile aimed at providing the skills required for establishing the scientific international collaborations that our globalized world demands, and to develop a new approach for science education. The National Antarctic Programs of Chile and the United States worked together on a pilot program that brought high school students and teachers from both countries to Punta Arenas, Chile, in February 2014. The goals of this project included strengthening the partnership between the two countries, and building relationships between future generations of scientists, while developing the students' awareness of global scientific issues and expanding their knowledge and interest in Antarctica and polar science. A big component of the project involved the sharing by students of the acquired knowledge and experiences with the general public. JASE is based on the successful Chilean Antarctic Science Fair developed by Chile´s Antarctic Research Institute. For 10 years, small groups of Chilean students, each mentored by a teacher, perform experimental or bibliographical Antarctic research. Winning teams are awarded an expedition to the Chilean research station on King George Island. In 2014, the Chileans invited US participation in this program in order to strengthen science ties for upcoming generations. On King George Island, students have hands-on experiences conducting experiments and learning about field research. While the total number of students directly involved in the program is relatively small, the sharing of the experience by students with the general public is a novel approach to science education. Research experiences for students, like JASE, are important as they influence new direction for students in science learning, science interest, and help increase science knowledge. We will share experiences with the

  6. Multi-year record of atmospheric and snow surface nitrate in the central Antarctic plateau.

    Science.gov (United States)

    Traversi, R; Becagli, S; Brogioni, M; Caiazzo, L; Ciardini, V; Giardi, F; Legrand, M; Macelloni, G; Petkov, B; Preunkert, S; Scarchilli, C; Severi, M; Vitale, V; Udisti, R

    2017-04-01

    Continuous all year-round samplings of atmospheric aerosol and surface snow at high (daily to 4-day) resolution were carried out at Dome C since 2004-05 to 2013 and nitrate records are here presented. Basing on a larger statistical data set than previous studies, results confirm that nitrate seasonal pattern is characterized by maxima during austral summer for both aerosol and surface snow, occurring in-phase with solar UV irradiance. This temporal pattern is likely due to a combination of nitrate sources and post-depositional processes whose intensity usually enhances during the summer. Moreover, it should be noted that a case study of the synoptic conditions, which took place during a major nitrate event, showed the occurrence of a stratosphere-troposphere exchange. The sampling of both matrices at the same time with high resolution allowed the detection of a an about one-month long recurring lag of summer maxima in snow with respect to aerosol. This result can be explained by deposition and post-deposition processes occurring at the atmosphere-snow interface, such as a net uptake of gaseous nitric acid and a replenishment of the uppermost surface layers driven by a larger temperature gradient in summer. This hypothesis was preliminarily tested by a comparison with surface layers temperature data in the 2012-13 period. The analysis of the relationship between the nitrate concentration in the gas phase and total nitrate obtained at Dome C (2012-13) showed the major role of gaseous HNO3 to the total nitrate budget suggesting the need to further investigate the gas-to-particle conversion processes.

  7. Structure and dynamics of the summertime atmospheric boundary layer over the Antarctic plateau: 1. Measurements and model validation

    NARCIS (Netherlands)

    van As, D.; van den Broeke, M.R.; Helsen, M.M.

    2006-01-01

    Profile mast, tethersonde and radiosonde measurements are used to describe the structure and dynamics of the summertime atmospheric boundary layer over the slightly sloping snow surface at Kohnen base (75°00'S, 0°04'E, 2892 m above sea level), located on the interior plateau of East Antarctica.

  8. Antarctic clouds

    OpenAIRE

    Lachlan-Cope, Tom

    2010-01-01

    Sensitivity studies with global climate models show that, by their influence on the radiation balance, Antarctic clouds play a major role in the climate system, both directly at high southern latitudes and indirectly globally, as the local circulation changes lead to global teleconnections. Unfortunately, observations of cloud distribution in the Antarctic are limited and often of low quality because of the practical difficulty in observing clouds in the harsh Antarctic environment. The best ...

  9. Continental Dynamics in High Tibetan Plateau: Normal Faulting Type Earthquake Activities and Mechanisms

    Institute of Scientific and Technical Information of China (English)

    Xu Jiren; Zhao Zhixin

    2009-01-01

    Various earthquake fault types were analyzed for this study on the crust movement in the high region of the Tibetan plateau by analyzing mechanism solutions and stress fields. The results show that a lot of normal faulting type earthquakes are concentrated in the central High Tibetan plateau. Many of them are nearly perfect normal fault events. The strikes of the fault planes of normal faulting earthquakes are almost in an N-S direction based on the analyses of the Wulff stereonet diagrams of fault plane solutions. It implies that the dislocation slip vectors of the normal faulting type events have quite great components in the E-W direction. The extensions probably are an eastward extensional motion, being mainly a tectonic active regime in the plateau altitudes. The tensional stress in the E-W or NWW-SEE direction predominates earthquake occurrences in the normal event region of the central plateau. The eastward extensional motion in the high Tibetan plateau is attributable to the gravitational collapse of the high plateau and the eastward extrusion of hotter mantle materials beneath the east boundary of the plateau. Extensional motions from the relaxation of the topography and/or gravitational collapse in the high plateau hardly occurred along the N-S direction. The obstruction for the plateau to move eastward is rather weak.

  10. Pv rural electrification programme at the Bolivian high plateau

    Energy Technology Data Exchange (ETDEWEB)

    Lorenzo, E.; Aguilera, J. [Instituto de Energia Solar, ETSI Telecomunicacion, (Spain)

    1995-12-31

    Since 1988 the Institute of Solar Energy of the Universidad Politecnica de Madrid is carrying out a pv rural electrification programme at the Bolivian high plateau. This programme has been focused in three aspects: the domestic electrification, users participation and transfer technology. At present, there are about 1,500 electrified dwellings distributed in the Bolivian high plateau. We have got deep knowledge about life style and organization of the aymara Indians who are the inhabitants of the working zone. We think that this knowledge can be very useful for a large scale introduction of PV solar energy in this region. Finally, we present a new way to transfer PV technology to developing countries. Thanks to this programme a group of aymara Indians is able to manufacture charge regulators and electronic ballast to use in the PV installations of the programme. [Espanol] Desde 1988 el Instituto de Energia Solar de la Universidad Politecnica de Madrid esta llevando a cabo un programa fotovoltaico de electrificacion rural en la altiplanicie Boliviana. Este programa ha sido enfocado a tres aspectos: la electrificacion domestica, la participacion de los usuarios y la transferencia de la tecnologia. Actualmente, hay alrededor de 1500 conjuntos habitacionales electrificados distribuidos en la altiplanicie Boliviana. Hemos obtenido un profundo conocimiento del estilo de vida y de la organizacion de los indios aymara que son los habitantes de la zona de trabajo. Pensamos que este conocimiento puede ser muy util para una introduccion en gran escala de la energia solar fotovoltaica en esta region. Finalmente, presentamos una nueva forma de transferir la tecnologia fotovoltaica a paises en desarrollo. Gracias a este programa un grupo de indios aymara pueden fabricar reguladores de carga y balastros electronicos para ser usados en instalaciones fotovoltaicas del programa.

  11. Simultaneous retrieval of water vapour, temperature and cirrus clouds properties from measurements of far infrared spectral radiance over the Antarctic Plateau

    Science.gov (United States)

    Di Natale, Gianluca; Palchetti, Luca; Bianchini, Giovanni; Del Guasta, Massimo

    2017-03-01

    The possibility separating the contributions of the atmospheric state and ice clouds by using spectral infrared measurements is a fundamental step to quantifying the cloud effect in climate models. A simultaneous retrieval of cloud and atmospheric parameters from infrared wideband spectra will allow the disentanglement of the spectral interference between these variables. In this paper, we describe the development of a code for the simultaneous retrieval of atmospheric state and ice cloud parameters, and its application to the analysis of the spectral measurements acquired by the Radiation Explorer in the Far Infrared - Prototype for Applications and Development (REFIR-PAD) spectroradiometer, which has been in operation at Concordia Station on the Antarctic Plateau since 2012. The code performs the retrieval with a computational time that is comparable with the instrument acquisition time. Water vapour and temperature profiles and the cloud optical and microphysical properties, such as the generalised effective diameter and the ice water path, are retrieved by exploiting the 230-980 cm-1 spectral band. To simulate atmospheric radiative transfer, the Line-By-Line Radiative Transfer Model (LBLRTM) has been integrated with a specifically developed subroutine based on the δ-Eddington two-stream approximation, whereas the single-scattering properties of cirrus clouds have been derived from a database for hexagonal column habits. In order to detect ice clouds, a backscattering and depolarisation lidar, co-located with REFIR-PAD has been used, allowing us to infer the position and the cloud thickness to be used in the retrieval. A climatology of the vertical profiles of water vapour and temperature has been performed by using the daily radiosounding available at the station at 12:00 UTC. The climatology has been used to build an a priori profile correlation to constrain the fitting procedure. An optimal estimation method with the Levenberg-Marquardt approach has been

  12. Snow accumulation variability derived from radar and firn core data along a 600 km transect in Adelie Land, East Antarctic plateau

    Directory of Open Access Journals (Sweden)

    D. Verfaillie

    2012-11-01

    Full Text Available The mass balance of ice sheets is an intensively studied topic in the context of global change and sea-level rise. However – particularly in Antarctica – obtaining mass balance estimates remains difficult due to various logistical problems. In the framework of the TASTE-IDEA (Trans-Antarctic Scientific Traverses Expeditions – Ice Divide of East Antarctica program, an International Polar Year project, continuous ground penetrating radar (GPR measurements were carried out during a traverse in Adelie Land (East Antarctica during the 2008–2009 austral summer between the Italian–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 and compare it with historical data and modelling. The focus was on the last 300 yr, from the pre-industrial period to recent times. Beta-radioactivity counting and gamma spectrometry were applied to cores at the 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 increase in accumulation towards the coast (from ≈ 3 cm w.e. a−1 at Dome C to ≈ 17 cm w.e. a−1 at the end of the transect and previously undocumented undulating structures between 300 and 600 km from DC. Results agree fairly well with data from previous studies and modelling. Drawing final conclusions on temporal variations is difficult because of the margin of error introduced by density estimation. This study should have various applications, including model validation.

  13. High prevalence of false-positive plateau phenomena during VO2max testing in adolescents.

    Science.gov (United States)

    Beltrami, Fernando G; Wong, Del P; Noakes, Timothy D

    2014-09-01

    It is believed that a plateau in oxygen consumption (VO2) at the end of an incremental exercise test identifies the upper limits of cardiovascular capacity. We investigated how different criteria influence the frequency with which the "plateau phenomenon" is detected and the prevalence at which "false" plateau phenomena occurs during sub-maximal exercise. Cross-sectional. Six different criteria with 3 different sampling intervals each were used to identify the "plateau phenomenon" from a single data set comprising 63 incremental exercise tests along with secondary criteria based on target heart rate (HR) and respiratory exchange ratio (RER). A single criterion from the original 18 (HALF) was also used to detect the incidence of any plateau phenomena during each test. The plateau phenomenon was detected in 16-82% of the tests depending on the criteria used, mostly as a result of the different sampling intervals. HALF identified 103 "plateau phenomena" but 73 (70.9%) of these occurred during sub-maximal exercise and so were "false". "False" plateaus were verified by at least one secondary criterion in 27% of cases. Participants reached the HR and RER targets after 83.6 ± 11.7% and 81.9 ± 18.1% of total test duration, respectively. The wide range in the percentage of plateau phenomena detected by different criteria plus the high rate (71%) of "false" plateau during sub-maximal exercise could indicate that this phenomenon is a calculation artifact rather than an indicator of true physiological events. Secondary criteria can be reached early in exercise and often identify "false" plateau phenomena as "true". Copyright © 2013 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  14. Oxygen isotope dynamics of atmospheric nitrate over the Antarctic plateau: First combined measurements of ozone and nitrate 17O-excess (Δ17O)

    Science.gov (United States)

    Vicars, William; Savarino, Joël; Erbland, Joseph; Preunkert, Susanne; Jourdain, Bruno; Frey, Markus; Gil, Jaime; Legrand, Michel

    2013-04-01

    calculated solely from local measurements and invoke no assumptions regarding the Δ17O value of ozone and its transfer in the atmosphere. The predicted Δ17O signature for nitrate formed over the Antarctic plateau during OPALE is on the order of (21 ± 2) ‰ when production is assumed to occur only through the OH + NO2 pathway, which is expected to be the dominant formation channel during the continuously sunlit summer. This predicted value is much lower than the values measured for nitrate during OPALE, with observed Δ17O(NO3-) varying in the range of 27 - 31 ‰. This discrepancy between expected and observed Δ17O(NO3-) values suggests the existence of an unexpected process that contributes significantly to the atmospheric nitrate budget over Dome C. The relative merits of different potential explanations for this puzzling result will be discussed in the context of oxidation chemistry, air mass transport, and snow/atmosphere exchange.

  15. High-resolution climate modelling of Antarctica and the Antarctic Peninsula

    NARCIS (Netherlands)

    van Wessem, J.M.

    2016-01-01

    In this thesis we have used a high-resolution regional atmospheric climate model (RACMO2.3) to simulate the present-day climate (1979-2014) of Antarctica and the Antarctic Peninsula. We have evaluated the model results with several observations, such as in situ surface energy balance (SEB) observati

  16. High-resolution climate modelling of Antarctica and the Antarctic Peninsula

    NARCIS (Netherlands)

    van Wessem, J.M.

    2016-01-01

    In this thesis we have used a high-resolution regional atmospheric climate model (RACMO2.3) to simulate the present-day climate (1979-2014) of Antarctica and the Antarctic Peninsula. We have evaluated the model results with several observations, such as in situ surface energy balance (SEB)

  17. The 2014 high record of Antarctic sea ice extent

    Science.gov (United States)

    Massonnet, Francois; Guemas, Virginie; Fuckar, Neven; Doblas-Reyes, Francisco

    2016-04-01

    In September 2014, Antarctic sea ice extent exceeded the symbolic level of 20 million km²for the first time since 1978, when reliable satellite measurements became available. After the successive records of 2012 and 2013, sea ice extent in 2014 once again reinforced the positive trend observed since the late 1970s. We conduct here a dedicated study to elucidate the origins of a major, and perhaps the most intriguing, event that happened at our Poles recently. Observations, reanalyses and model results all point towards the important role of winds in modifying near-surface heat advection patterns around Antarctica. The role of pre-conditioning (summer conditions) is found to be of lesser importance. Finally, we find no evidence that anomalous freshwater forcing (from atmospheric or continental origin) could have explained the record extent of 2014.

  18. Slow steady exhumation of the high elevation Deosai Plateau (Northern Pakistan Himalaya) since 40 Ma

    Science.gov (United States)

    van Melle, J.; van der Beek, P.; Guillot, S.; Pecher, A.; Latif, M.

    2007-12-01

    Mountain ranges of the north-western Himalaya in Pakistan show strongly contrasting relief, opposing steep, deeply incised topography with extremely high peaks such as the Karakorum Range and Nanga Parbat Haramosh Massif (NPHM), to high-altitude, low-relief areas such as the Deosai Plateau located between the Karakorum and NPHM and the Tso-Morari Massif in Eastern Ladakh. In contrast, mean elevations of the different mountain ranges are comparable, the Deosai Plateau being on average even slightly higher than the adjacent NPHM. The aim of this study is to quantify the exhumation history the Deosai Plateau, in order to understand how to build such a high-altitude, low-relief plateau and how to preserve it over million-year timescales. Here, we report the first low-temperature thermochronologic data from the Deosai Plateau, to compare its exhumation history to that of the surrounding massifs. Apatite Fission Track (AFT) ages reported in the literature from the NPHM and Karakorum are extremely young (1 km/Ma. In contrast, our AFT ages from the Deosai Plateau are 15-27 Ma; an order of magnitude older than those of the surrounding massifs. Zircon and apatite (U-Th)/He ages (measured at U of Arizona, HeDWaAZ program) range from 23-45 Ma, and 12-15 Ma, respectively. Modeling the combined AFT and He ages requires continuous and very slow long term cooling rates (around 4 ° C/Ma), consistent with an exhumation rate of about 0.15 km/Ma for typical geothermal gradients. Our data thus suggest steady slow unroofing of the Deosai Plateau since at least 40 Ma. A clear link between cooling age patterns and the geomorphology is also evident, with strongly incised, high-relief massifs showing exhumation at rates an order of magnitude faster than the low-relief plateau. AFT and ZFT ages similar to our data have been reported from the Tso Morari massif further east, characterised by similar high-elevation low-relief morphology. These morphologic zones cross the Indus and Shyok Suture

  19. Antarctic strict anaerobic microbiota from Deschampsia antarctica vascular plants rhizosphere reveals high ecology and biotechnology relevance.

    Science.gov (United States)

    Peixoto, Rafael José Marques; Miranda, Karla Rodrigues; Lobo, Leandro Araujo; Granato, Alessandra; de Carvalho Maalouf, Pedro; de Jesus, Hugo Emiliano; Rachid, Caio T C C; Moraes, Saulo Roni; Dos Santos, Henrique Fragoso; Peixoto, Raquel Silva; Rosado, Alexandre Soares; Domingues, Regina Maria Cavalcanti Pilotto

    2016-11-01

    The Antarctic soil microbial community has a crucial role in the growth and stabilization of higher organisms, such as vascular plants. Analysis of the soil microbiota composition in that extreme environmental condition is crucial to understand the ecological importance and biotechnological potential. We evaluated the efficiency of isolation and abundance of strict anaerobes in the vascular plant Deschampsia antarctica rhizosphere collected in the Antarctic's Admiralty Bay and associated biodiversity to metabolic perspective and enzymatic activity. Using anaerobic cultivation methods, we identified and isolated a range of microbial taxa whose abundance was associated with Plant Growth-Promoting Bacteria (PGPB) and presences were exclusively endemic to the Antarctic continent. Firmicutes was the most abundant phylum (73 %), with the genus Clostridium found as the most isolated taxa. Here, we describe two soil treatments (oxygen gradient and heat shock) and 27 physicochemical culture conditions were able to increase the diversity of anaerobic bacteria isolates. Heat shock treatment allowed to isolate a high percentage of new species (63.63 %), as well as isolation of species with high enzymatic activity (80.77 %), which would have potential industry application. Our findings contribute to the understanding of the role of anaerobic microbes regarding ecology, evolutionary, and biotechnological features essential to the Antarctic ecosystem.

  20. Persistent organochlorines in high-Antarctic fish; Persistente chlororganische Verbindungen in hochantarktischen Fischen

    Energy Technology Data Exchange (ETDEWEB)

    Zimmermann, S.

    1997-11-01

    24 chlorinated hydrocarbons from different classes (PCB, HCH, DDT, Chlordane, Hexachlorobenzene and Octachlorostyrene) were analyzed in four species of high-Antarctic fish (Aethotaxis mitopteryx, Pleuragramma antarcticum, Trematomus lepidorhinus, and Chinodraco myersi). The concentrations were in the order of 1 {mu}g/kg wet weight or 10 {mu}g/kg lipid weight, respectively. Highest concentrations were measured for HCB in all species. The species showed different distribution patterns for the organochlorines studied. Compared with concentrations in fish from other regions the organochlorine levels measured in Antarctic fish are rather low. It is unlikely that the burden of organochlorines will cause any toxic effects in high-Antarctic fish yet. Nevertheless, with regard to the sensitive Antarctic ecosystem, even small concentrations carry a high risk of harm for Antarctic life. Environmental pollution in Antarctica should be observed with a monitoring program using standardized methods. For this purpose, the fish species studied are very useful as bioindicators for organochlorine contamination. (orig.) [Deutsch] 24 persistente Chlorkohlenwasserstoffe verschiedener Schadstoffgruppen (PCB, HCH, DDT, Chlordan, Hexachlorbenzol und Octachlorstyrol) wurden in vier hochantarktischen Fischarten (Aethotaxis mitopteryx, Pleuragramma antarcticum, Trematomus lepidorhinus und Chionodraco myersi). Die Konzentrationen der nachgewiesenen Schadstoffe im Ganzfisch liegen jeweils in der Groessenordnung von 1 {mu}g/kg Feuchtgewicht bzw. 10 {mu}g/kg Lipidgewicht mit erheblichen Schwankungen je nach Schadstoff und Art. Die Spezies zeigen artspezifische Schadstoffverteilungsmuster. Die Konzentrationen sind gegenueber denen in Fischen aus Gebieten mit staerkerem zivilisatorischem Einfluss eher niedrig. Die Fremstoffbelastungen der hochantarktischen Fische fuehren wahrscheinlich noch nicht zu messbaren toxischen Effekten bei den Fischen. Dennoch geht von den Schadstoffen in Hinblick auf das

  1. Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea-ice

    Directory of Open Access Journals (Sweden)

    R. S. Humphries

    2015-10-01

    Full Text Available The effect of aerosols on clouds and their radiative properties is one of the largest uncertainties in our understanding of radiative forcing. A recent study has concluded that better characterisation of pristine, natural aerosol processes leads to the largest reduction in these uncertainties. Antarctica, being far from anthropogenic activities, is an ideal location for the study of natural aerosol processes. Aerosol measurements in Antarctica are often limited to boundary layer air-masses at spatially sparse coastal and continental research stations, with only a handful of studies in the sea ice region. In this paper, the first observational study of sub-micron aerosols in the East Antarctic sea ice region is presented. Measurements were conducted aboard the ice-breaker Aurora Australis in spring 2012 and found that boundary layer condensation nuclei (CN3 concentrations exhibited a five-fold increase moving across the Polar Front, with mean Polar Cell concentrations of 1130 cm−3 – higher than any observed elsewhere in the Antarctic and Southern Ocean region. The absence of evidence for aerosol growth suggested that nucleation was unlikely to be local. Air parcel trajectories indicated significant influence from the free troposphere above the Antarctic continent, implicating this as the likely nucleation region for surface aerosol, a similar conclusion to previous Antarctic aerosol studies. The highest aerosol concentrations were found to correlate with low pressure systems, suggesting that the passage of cyclones provided an accelerated pathway, delivering air-masses quickly from the free-troposphere to the surface. After descent from the Antarctic free troposphere, trajectories suggest that sea ice boundary layer air-masses travelled equator-ward into the low albedo Southern Ocean region, transporting with them emissions and these aerosol nuclei where, after growth, may potentially impact on the region's radiative balance. The high aerosol

  2. Use of high frequency radiometer and altimeter on board AMSU-B, AMSR-E and Altika/SARAL for observations of the Antarctic ice sheet surface.

    Science.gov (United States)

    Adodo, Fifi; Picard, Ghislain; Remy, Frederique

    2016-04-01

    Snow surface properties quickly evolved according to local weather conditions, therefore are climate change indicator. These snow surface properties such as grain size, density, accumulation rate etc... are very important for evaluation and monitoring of the impact of global warming on the polar ice sheet. In order to retrieve these snowpack properties, we explore the high frequency microwave radiometer variable( Brightness Temperature (Tb)) on the Antarctic ice sheet on-board AMSU-B , AMSR-E in combination with the ALTIKA altimeter (37GHz) waveform parameters (Backscatter coefficient, Trailing edge Slope(TeS) and Leading edge Width(LeW)). We compare the radiometer brightness temperature to calculations with the DMRT- ML radiative transfer model which simulates brightness temperature in vertical and horizontal polarizations. With some assumptions, this combination allows a good retrieval of snowpack properties. We showed positive trend of the grains size on the Antarctic plateau especially at Dome C during the two last decades. This work will provide a higher accuracy of the estimation of snowpack surfaces properties and contribute to monitoring the ice sheet surface mass balance, well constraining of meteorological and glaciological models.

  3. Geographic names of the Antarctic

    Science.gov (United States)

    ,; ,; ,; ,; Alberts, Fred G.

    1995-01-01

    This gazetteer contains 12,710 names approved by the United States Board on Geographic Names and the Secretary of the Interior for features in Antarctica and the area extending northward to the Antarctic Convergence. Included in this geographic area, the Antarctic region, are the off-lying South Shetland Islands, the South Orkney Islands, the South Sandwich Islands, South Georgia, Bouvetøya, Heard Island, and the Balleny Islands. These names have been approved for use by U.S. Government agencies. Their use by the Antarctic specialist and the public is highly recommended for the sake of accuracy and uniformity. This publication, which supersedes previous Board gazetteers or lists for the area, contains names approved as recently as December 1994. The basic name coverage of this gazetteer corresponds to that of maps at the scale of 1:250,000 or larger for coastal Antarctica, the off-lying islands, and isolated mountains and ranges of the continent. Much of the interior of Antarctica is a featureless ice plateau. That area has been mapped at a smaller scale and is nearly devoid of toponyms. All of the names are for natural features, such as mountains, glaciers, peninsulas, capes, bays, islands, and subglacial entities. The names of scientific stations have not been listed alphabetically, but they may appear in the texts of some decisions. For the names of submarine features, reference should be made to the Gazetteer of Undersea Features, 4th edition, U.S. Board on Geographic Names, 1990.

  4. Relationship Between the Eastern Tibetan Plateau Rainfall and Subtropical High Shift in Summer

    Institute of Scientific and Technical Information of China (English)

    GONG Yuanfa; HE Jinhai; CHEN Longxun

    2006-01-01

    Based on the routine rainfall data on the Tibetan Plateau and NCEP/NCAR reanalysis data, the rela tionship between the eastern Tibetan Plateau rainfall and the southward/northward shift of West Pacific subtropical high in summer of 1993/1994 is studied. The results show that: the West Pacific subtropi cal high is abnormally located to more southern latitude and the high ridge is mainly the quasi-biweekly southward/northward oscillation in its processes of northward shift from May to August in 1993; but it is ab normally located to more northern latitude and the high ridge is obviously 30-60-day southward/northward oscillation in its processes of northward shift from May to August in 1994. At the same time, it is found that the changes of the eastern Tibetan Plateau rainfall active/break have the similar characteristics of the high ridge southward/northward oscillation. Therefore, the southward/northward shift of the West Pacific subtropical high in summer may be related to the changes of eastern Tibetan Plateau rainfall active/break.

  5. Increase of the Antarctic Sea Ice Extent is highly significant only in the Ross Sea

    Science.gov (United States)

    Yuan, Naiming; Ding, Minghu; Ludescher, Josef; Bunde, Armin

    2017-01-01

    In the context of global warming, the question of why Antarctic sea ice extent (SIE) has increased is one of the most fundamental unsolved mysteries. Although many mechanisms have been proposed, it is still unclear whether the increasing trend is anthropogenically originated or only caused by internal natural variability. In this study, we employ a new method where the underlying natural persistence in the Antarctic SIE can be correctly accounted for. We find that the Antarctic SIE is not simply short-term persistent as assumed in the standard significance analysis, but actually characterized by a combination of both short- and long-term persistence. By generating surrogate data with the same persistence properties, the SIE trends over Antarctica (as well as five sub-regions) are evaluated using Monte-Carlo simulations. It is found that the SIE trends over most sub-regions of Antarctica are not statistically significant. Only the SIE over Ross Sea has experienced a highly significant increasing trend (p = 0.008) which cannot be explained by natural variability. Influenced by the positive SIE trend over Ross Sea, the SIE over the entire Antarctica also increased over the past decades, but the trend is only at the edge of being significant (p = 0.034).

  6. Autonomous profiling float observations of the high-biomass plume downstream of the Kerguelen Plateau in the Southern Ocean

    Science.gov (United States)

    Grenier, M.; Della Penna, A.; Trull, T. W.

    2015-05-01

    Natural iron fertilisation from Southern Ocean islands results in high primary production and phytoplankton biomass accumulations readily visible in satellite ocean colour observations. These images reveal great spatial complexity with highly varying concentrations of chlorophyll, presumably reflecting both variations in iron supply and conditions favouring phytoplankton accumulation. To examine the second aspect, in particular the influences of variations in temperature and mixed layer depth, we deployed four autonomous profiling floats in the Antarctic Circumpolar Current near the Kerguelen Plateau in the Indian sector of the Southern Ocean. Each "bio-profiler" measured more than 250 profiles of temperature (T), salinity (S), dissolved oxygen, chlorophyll a (Chl a) fluorescence, and particulate backscattering (bbp) in the top 300 m of the water column, sampling up to 5 profiles per day along meandering trajectories extending up to 1000 km. Comparison of surface Chl a estimates (analogous to values from satellite images) with total water column inventories revealed largely linear relationships, suggesting that these images provide credible information on total and not just surface biomass spatial distributions. However, they also showed that physical mixed layer depths are often not a reliable guide to biomass distributions. Regions of very high Chl a accumulation (1.5-10 μg L-1) were associated predominantly with a narrow T-S class of surface waters. In contrast, waters with only moderate Chl a enrichments (0.5-1.5 μg L-1) displayed no clear correlation with specific water properties, including no dependence on mixed layer depth or the intensity of stratification. Geostrophic trajectory analysis suggests that both these observations can be explained if the main determinant of biomass in a given water parcel is the time since leaving the Kerguelen Plateau. One float became trapped in a cyclonic eddy, allowing temporal evaluation of the water column in early

  7. Prehistoric Human Dispersal to the Tibetan Plateau and Adaptation to the High Altitude Environment

    Science.gov (United States)

    Zhang, Dongju; Dong, Guanghui; Chen, Fahu

    2016-04-01

    Human history of the Tibetan Plateau and human adaptation to the high altitude environment is hotly debated in the past decade among archaeological, anthropological, genetic, and even past climate change studies. Based on previous studies on the Tibetan Plateau and our own archaeological studies in northeastern Tibetan Plateau (NETP), we propose that human migrated to the Tibetan Plateau from the last Deglacial period to late Holocene mainly from North China via Yellow River valley and its tributary valleys in NETP. This migration is constituted of four stages (Upper Paleolithic, Epi-Paleolithic, Neolithic and Bronze Age) when human adapted to the high altitude environment and climate change with different strategies and techniques. Particularly, the prevail of microlithic technology in North China provoked hunter-gatherers' first visit to the NETP in relatively ameliorated last Deglacial period, and the quick development of millet farming and subsequent mixed barley-wheat farming and sheep herding facilitated farmers and herders permanently settled in NETP, even above 3000 masl, during mid- and late Holocene.

  8. Inhibition of inducible nitric oxide synthase expression and nitric oxide production in plateau pika (Ochotona curzoniae) at high altitude on Qinghai-Tibet Plateau.

    Science.gov (United States)

    Xie, Ling; Zhang, Xuze; Qi, Delin; Guo, Xinyi; Pang, Bo; Du, Yurong; Zou, Xiaoyan; Guo, Songchang; Zhao, Xinquan

    2014-04-30

    Nitric oxide (NO), a potent vasodilator, plays an important role in preventing hypoxia induced pulmonary hypertension. Endogenous NO is synthesized by nitric oxide synthases (NOSs) from l-arginine. In mammals, three different NOSs have been identified, including neuronal NOS (nNOS), endothelial NOS (eNOS) and inducible NOS (iNOS). Plateau pika (Ochotona curzoniae) is a typical hypoxia tolerant mammal that lives at 3000-5000 m above sea level on the Qinghai-Tibet Plateau. The aim of this study was to investigate whether NOS expression and NO production are regulated by chronic hypoxia in plateau pika. Quantitative real-time PCR and western blot analyses were conducted to quantify relative abundances of iNOS and eNOS transcripts and proteins in the lung tissues of plateau pikas at different altitudes (4550, 3950 and 3200 m). Plasma NO metabolites, nitrite/nitrate (NO(x)⁻) levels were also examined by Ion chromatography to determine the correlation between NO production and altitude level. The results revealed that iNOS transcript levels were significantly lower in animals at high altitudes (decreased by 53% and 57% at altitude of 3950 and 4550 m compared with that at 3200 m). Similar trends in iNOS protein abundances were observed (26% and 41% at 3950 and 4550 m comparing with at 3200 m). There were no significant differences in eNOS mRNA and protein levels in the pika lungs among different altitudes. The plasma NO(x)⁻ levels of the plateau pikas at high altitudes significantly decreased (1.65±0.19 μg/mL at 3200 m to 0.44±0.03 μg/mL at 3950 m and 0.24±0.01 μg/mL at 4550 m). This is the first evidence describing the effects of chronic hypoxia on NOS expression and NO levels in the plateau pika in high altitude adaptation. We conclude that iNOS expression and NO production are suppressed at high altitudes, and the lower NO concentration at high altitudes may serve crucial roles for helping the plateau pika to survive at hypoxic environment.

  9. Last glacial tephra layers in the Talos Dome ice core (peripheral East Antarctic Plateau), with implications for chronostratigraphic correlations and regional volcanic history

    Science.gov (United States)

    Narcisi, Biancamaria; Petit, Jean Robert; Langone, Antonio

    2017-06-01

    Tephra isochrons offer considerable potential for correlating diverse palaeoarchives and highlighting regional climatic differences. They are especially useful when applied to polar ice records encompassing the last glacial, as these clearly portray the pronounced millennial-scale climate variability that characterised this period. Here we present the continuous record of primary fallout tephra layers in the East Antarctic Talos Dome ice core (72°49‧S, 159°11‧E), developed upon examination of the core sections spanning the glacial period 16.5 to 71 ka. A total of ca. 45 discrete tephra deposits precisely positioned stratigraphically relative to the temperature record for the core and dated using the AICC2012 timescale, were identified. Quantitative grain size, particle morphology, major and trace element composition using Coulter Counter, SEM, EPMA-WDS, and LA-ICP-MS analytical methods were studied as diagnostic features for tephra characterisation. The tephrostratigraphic framework provides a reference for future precise comparison between ice and sediment sequences across the Antarctic continent. Indeed, several potential markers characterised by distinct volcanic glass geochemistry and/or particular stratigraphic location (e.g., a 17.6-ka ash layer deposited during the well-known major acidity event) are now available for the direct linkage of palaeoclimatic archives. The Talos Dome tephra sequence, dominated by mid-distal pyroclastic products from the nearby Northern Victoria Land volcanoes, also represents the most comprehensive and best time-constrained record of regional Antarctic volcanism yet developed. It documents nearly continuous sustained explosive activity during the considered time interval and, combined with previous ice-core tephra results for the last and the current interglacial periods, suggests progressive compositional shift through time.

  10. High Voltage Plateau and Data Reliability Test for the DSNC Troubleshooting

    Energy Technology Data Exchange (ETDEWEB)

    Park, Kwang-June; Jeong, Jeong-Whan; Kang, Hee-Young; Shin, Hee-Sung; Kim, Ho-Dong [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2006-07-01

    DSNC(Dupic safeguard neutron counter) was installed in the Dupic fuel development facility (DFDF) for the nuclear material accounting in the end of 1990s and had operated normally until 2003. But there have been a problem after that time. It has an abnormal state in the function of counting the neutrons emitting from the Dupic process product as well as the spent nuclear fuel at present. In this study, high voltage plateau and data acquisition reliability test were carried out as a method of troubleshooting for DSNC. As a result of the test, it was confirmed that the high voltage plateau was not formed but data acquisition reliability was good at some high voltages and at 6V applied to the electronic circuit of the counter.

  11. Modeling the Physical Multi-Phase Interactions of HNO3 Between Snow and Air on the Antarctic Plateau (Dome C) and coast (Halley)

    Science.gov (United States)

    Chan, Hoi Ga; Frey, Markus M.; King, Martin D.

    2017-04-01

    Nitrogen oxides (NOx = NO + NO2) emissions from nitrate (NO3-) photolysis in snow affect the oxidising capacity of the lower troposphere especially in remote regions of the high latitudes with low pollution levels. The porous structure of snowpack allows the exchange of gases with the atmosphere driven by physicochemical processes, and hence, snow can act as both source and sink of atmospheric chemical trace gases. Current models are limited by poor process understanding and often require tuning parameters. Here, two multi-phase physical models were developed from first principles constrained by observed atmospheric nitrate, HNO3, to describe the air-snow interaction of nitrate. Similar to most of the previous approaches, the first model assumes that below a threshold temperature, To, the air-snow grain interface is pure ice and above To, a disordered interface (DI) emerges assumed to be covering the entire grain surface. The second model assumes that Air-Ice interactions dominate over the entire temperature range below melting and that only above the eutectic temperature, liquid is present in the form of micropockets in grooves. The models are validated with available year-round observations of nitrate in snow and air at a cold site on the Antarctica Plateau (Dome C, 75°06'S, 123°33'E, 3233 m a.s.l.) and at a relatively warm site on the Antarctica coast (Halley, 75°35'S, 26°39'E, 35 m a.s.l). The first model agrees reasonably well with observations at Dome C (Cv(RMSE) = 1.34), but performs poorly at Halley (Cv(RMSE) = 89.28) while the second model reproduces with good agreement observations at both sites without any tuning (Cv(RMSE) = 0.84 at both sites). It is therefore suggested that air-snow interactions of nitrate in the winter are determined by non-equilibrium surface adsorption and co-condensation on ice coupled with solid-state diffusion inside the grain. In summer, however, the air-snow exchange of nitrate is mainly driven by solvation into liquid

  12. Discovery of C4 species at high altitude in Qinghai-Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    WANG Luo; L(U) Houyuan; WU Naiqin; CHU Duo; HAN Jiamao; WU Yuhu; WU Haibin; GU Zhaoyan

    2004-01-01

    Plant specimens are collected from the areas between latitude 27°42'N and 40°57'N, and longitude 88°93'E and 103°24'E, with an altitudinal range from 2210 to 5050 m above the sea level in Qinghai-Tibetan Plateau. The stable carbon isotope analysis indicates that two of Chenopodiaceae and six of Poaceae in the samples are C4 plants. Four of the C4 plants are found in 11 spots with altitudes above 3800 m,and Pennisetum centrasiaticum, Arundinella yunnanensis and Orinus thoroldii are present in six spots above 4000 m, even up to 4520 m. At low CO2 partial pressure, that sufficient energy of high light improving C4 plant's tolerance of low temperature and precipitations concentrating in growing season probably are favorable for C4 plants growing at high altitude in Qinghai-Tibetan Plateau.

  13. Large Differences in Bacterial Community Composition among Three Nearby Extreme Waterbodies of the High Andean Plateau.

    Science.gov (United States)

    Aguilar, Pablo; Acosta, Eduardo; Dorador, Cristina; Sommaruga, Ruben

    2016-01-01

    The high Andean plateau or Altiplano contains different waterbodies that are subjected to extreme fluctuations in abiotic conditions on a daily and an annual scale. The bacterial diversity and community composition of those shallow waterbodies is largely unexplored, particularly, of the ponds embedded within the peatland landscape (i.e., Bofedales). Here we compare the small-scale spatial variability (Altiplano peatland ponds represent a hitherto unknown source of microbial diversity.

  14. An improved Antarctic dataset for high resolution numerical ice sheet models (ALBMAP v1

    Directory of Open Access Journals (Sweden)

    A. M. Le Brocq

    2010-10-01

    Full Text Available The dataset described in this paper (ALBMAP has been created for the purposes of high-resolution numerical ice sheet modelling of the Antarctic Ice Sheet. It brings together data on the ice sheet configuration (e.g. ice surface and ice thickness and boundary conditions, such as the surface air temperature, accumulation and geothermal heat flux. The ice thickness and basal topography is based on the BEDMAP dataset (Lythe et al., 2001, however, there are a number of inconsistencies within BEDMAP and, since its release, more data has become available. The dataset described here addresses these inconsistencies, including some novel interpolation schemes for sub ice-shelf cavities, and incorporates some major new datasets. The inclusion of new datasets is not exhaustive, this considerable task is left for the next release of BEDMAP, however, the data and procedure documented here provides another step forward and demonstrates the issues that need addressing in a continental scale dataset useful for high resolution ice sheet modelling. The dataset provides an initial condition that is as close as possible to present-day ice sheet configuration, aiding modelling of the response of the Antarctic Ice Sheet to various forcings, which are, at present, not fully understood.

  15. 南极考察队员在不同高原环境下血氧饱和度及心率与高原反应风险的关系%Study of blood oxygen saturation, heart rate changes and plateau reaction of the Antarctic Kunlun station investigation team in different plateau environments

    Institute of Scientific and Technical Information of China (English)

    赵顺云; 吴新民; 郭亚民; 张树顺; 安艳明; 李冰; 王皓

    2013-01-01

    目的 探讨南极考察队员在不同高原环境下血氧饱和度、心率变化与高原反应风险的关系.方法 2010年8月至2011年4月采用无创性氧饱和度测定仪监测(MD300-C) 16名南极考察队员在不同海拔情况以及不同高原环境(西藏高原和南极高原)下的血氧饱和度和心率变化以及高原反应情况,根据Lake Louise Consensus急性高原反应症状评分和判定方法,判定急性高原反应的程度.结果 16名考察队员在我国海拔110、3650、4300 m时血氧饱和度、心率情况差异均有统计学意义[96.8%±1.2%、89.1%±1.2%、86.1%±2.0%,(75.0±5.4)次/min、(104.0±4.3)次/min、(113.0±5.2)次/min,F=214.155、240.088,均P<0.05].南极高原环境下不同海拔(2000、2500、3000、3500、4087 m)血氧饱和度、心率差异也均有统计学意义[91.9%±1.3%、90.5%±1.3%、87.6%±1.4%、85.0%±1.8%、81.5%±2.2%,(85.9±3.2)次/min、(90.6±2.8)次/min、(97.8±4.1)次/min、(102.0±3.4)次/min、(106.3±3.9)次/min,F=105.418、90.174,均P<0.05].在南极高原环境下氧饱和度、心率与Lake Louise Consensus急性高原病症状评分相关(r=-0.446、0.565,均P<0.05).结论 南极考察队员在西藏高原和南极高原不同海拔下血氧饱和度、心率有明显的变化,且随着海拔的升高,高原反应风险逐渐增加.%Objective To explore the blood oxygen saturation and heart rate changes of the Antarctic expeditioners.Methods During August 2010 to April 2011,the changes in blood oxygen saturation,heart rate and plateau reaction of 16 Antarctic expedition team in different plateau environments (Tibetan plateau versus Antarctic plateau) were monitored with the noninvasive pulse oximeter MD300-C.The extent of acute mountain sickness was determined according to the Lake Louise Consensus acute mountain reaction symptom scores and judgment method.Results The changes of blood oxygen saturation,heart rate at different altitudes

  16. East Antarctic ice sheet stability recorded in a high-elevation ice-cored moraine

    Science.gov (United States)

    Bader, Nicole A.; Licht, Kathy J.; Kaplan, Michael R.; Kassab, Christine; Winckler, Gisela

    2017-03-01

    Till in an extensive blue ice moraine in the central Transantarctic Mountains at Mt. Achernar shows relatively continuous deposition by East Antarctic derived ice throughout the last glacial cycle. The most recently exposed material along the active margin of the Law Glacier (Zone 1) has hummocky topography that transitions into to a relatively flat region (Zone 2), followed by a series of ∼2 m high continuous, parallel/sub-parallel ridges and troughs (Zones 3-5). The entire moraine is ice-cored. Past surface changes of data, the U-Pb zircon data from till across all zones show little variability and are consistent with a Beacon Supergroup source, as samples show significant populations from the Proterozoic, ∼550-600 Ma and ∼950-1270 Ma, as well as the late Archean ∼2700-2770 Ma. The Mackellar, Fairchild, and lower Buckley Formations are interpreted as dominant sources of the detrital zircons. The zircon data lack the spatio-temporal variability indicated by the pebble fraction because the local Ferrar dolerite is not zircon bearing, highlighting the broader importance of using multiple techniques when interpreting provenance changes over time. Rather than reflecting major changes in ice flow path over time, the provenance changes are interpreted to indicate relative stability of the East Antarctic ice sheet, as the Law Glacier tapped into and eroded successively lower stratigraphic units of the Beacon Supergroup. This has important implications for interpreting offshore provenance records.

  17. Strontium isotope evidence for a highly mobile population on the Pamir Plateau 2500 years ago

    Science.gov (United States)

    Wang, Xueye; Tang, Zihua; Wu, Jing; Wu, Xinhua; Wu, Yiqun; Zhou, Xinying

    2016-10-01

    Archeological researches have proposed arguments for human mobility and long-distance trading over the Eurasia before the Silk Roads. Here we utilize biologically available strontium isotope analysis to assess the extent of pre-Silk Road population movements and cultural communications across the Asian interior. From an early Iron Age cemetery (ca. 2500 yr B.P.) on the eastern Pamir Plateau, mean 87Sr/86Sr ratios from 34 individuals display considerable isotopic variability, and 10 individuals are distinguished as migrants based on the local strontium isotope range of 0.710296–0.710572 defined by 12 ovicaprine bones. Comparison of the proportion (10/34) with the regional census data completed in 1909 A.D. (3% non-locals) suggests a highly migratory behavior on the plateau 2500 years ago. Furthermore, exotic mortuary objects, such as silk fabrics from eastern China and angular harp originated from the Near East, clearly demonstrate an interaction between different cultures on the plateau before the establishment of the Silk Road.

  18. Variation of Accumulation Rates Over the Last Eight Centuries on the East Antarctic Plateau Derived from Volcanic Signals in Ice Cores

    Science.gov (United States)

    Anschuetz, H.; Sinisalo, A.; Isaksson, E.; McConnell, J. R.; Hamran, S.-E.; Bisiaux, M. M.; Pasteris, D.; Neumann, T. A.; Winther, J.-G.

    2011-01-01

    Volcanic signatures in ice-core records provide an excellent means to date the cores and obtain information about accumulation rates. From several ice cores it is thus possible to extract a spatio-temporal accumulation pattern. We show records of electrical conductivity and sulfur from firn cores from the Norwegian-USA scientific traverse during the International Polar Year 2007-2009 (IPY) through East Antarctica. Major volcanic eruptions are identified and used to assess century-scale accumulation changes. The largest changes seem to occur in the most recent decades with accumulation over the period 1963- 2007/08 being up to 25 % different from the long-term record. There is no clear overall trend, some sites show an increase in accumulation over the period 1963 to present while others show a decrease. Almost all of the sites above 3200 m above sea level (asl) suggest a decrease. These sites also show a significantly lower accumulation value than large-scale assessments both for the period 1963 to present and for the long-term mean at the respective drill sites. The spatial accumulation distribution is influenced mainly by elevation and distance to the ocean (continentality), as expected. Ground-penetrating radar data around the drill sites show a spatial variability within 10-20 % over several tens of kilometers, indicating that our drill sites are well representative for the area around them. Our results are important for large-scale assessments of Antarctic mass balance and model validation.

  19. Levoglucosan indicates high levels of biomass burning aerosols over oceans from the Arctic to Antarctic

    Science.gov (United States)

    Hu, Q.; Xie, Z.; Wang, X.; Kang, H.; Zhang, P.

    2015-12-01

    Biomass burning discharges numerous kinds of gases and aerosols, such as carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), black carbon (BC), alcohols, organic acids and persistent organic pollutants (POPs), and is known to affect air quality, global carbon cycle, and climate. However, the extent to which biomass burning gases/aerosols are present on a global scale, especially in the marine atmosphere, is poorly understood. Here we measure levoglucosan, a superior molecular tracer of biomass burning aerosols because of its single source, in marine air from the Arctic Ocean through the North and South Pacific Ocean to coastal Antarctica during burning season. Levoglucosan was found to be present in all regions at ng/m3 levels. As a whole, levoglucosan concentrations in the Southern Hemisphere were comparable to those in the Northern Hemisphere. Marine air in the mid-latitudes (30°-60° N and S) has the highest levoglucosan loading due to the emission from adjacent lands. Air over the Arctic Ocean which affected by biomass burning in the east Siberia has intermediate loading. Equatorial latitudes is the main source of biomass burning emissions, however, levoglucosan is in relatively low level. Large amount of precipitation and high hydroxyl radical concentration in this region cause more deposition and degradation of levoglucosan during transport. Previous studies were debatable on the influence of biomass burning on the Antarctic because of uncertain source of BC. Here via levoglucosan, it is proved that although far away from emission sources, the Antarctic is still affected by biomass burning aerosols which may be derived from South America. Biomass burning has a significant impact on mercury (Hg) and water-soluble organic carbon (WSOC) in marine aerosols from pole to pole, with more contribution to WSOC in the Northern Hemisphere than in the Southern Hemisphere.

  20. Characterization of Bacterial, Archaeal and Eukaryote Symbionts from Antarctic Sponges Reveals a High Diversity at a Three-Domain Level and a Particular Signature for This Ecosystem

    Science.gov (United States)

    Rodríguez-Marconi, Susana; De la Iglesia, Rodrigo; Díez, Beatriz; Fonseca, Cássio A.; Hajdu, Eduardo; Trefault, Nicole

    2015-01-01

    Sponge-associated microbial communities include members from the three domains of life. In the case of bacteria, they are diverse, host specific and different from the surrounding seawater. However, little is known about the diversity and specificity of Eukarya and Archaea living in association with marine sponges. This knowledge gap is even greater regarding sponges from regions other than temperate and tropical environments. In Antarctica, marine sponges are abundant and important members of the benthos, structuring the Antarctic marine ecosystem. In this study, we used high throughput ribosomal gene sequencing to investigate the three-domain diversity and community composition from eight different Antarctic sponges. Taxonomic identification reveals that they belong to families Acarnidae, Chalinidae, Hymedesmiidae, Hymeniacidonidae, Leucettidae, Microcionidae, and Myxillidae. Our study indicates that there are different diversity and similarity patterns between bacterial/archaeal and eukaryote microbial symbionts from these Antarctic marine sponges, indicating inherent differences in how organisms from different domains establish symbiotic relationships. In general, when considering diversity indices and number of phyla detected, sponge-associated communities are more diverse than the planktonic communities. We conclude that three-domain microbial communities from Antarctic sponges are different from surrounding planktonic communities, expanding previous observations for Bacteria and including the Antarctic environment. Furthermore, we reveal differences in the composition of the sponge associated bacterial assemblages between Antarctic and tropical-temperate environments and the presence of a highly complex microbial eukaryote community, suggesting a particular signature for Antarctic sponges, different to that reported from other ecosystems. PMID:26421612

  1. High-resolution peat records for Holocene monsoon history in the eastern Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    YU; Xuefeng; ZHOU; Weijian; Lars; G.Franzen; XIAN; Feng; CHENG; Peng; A.J.; Tim; Jull

    2006-01-01

    The variations of summer and winter monsoons during the Holocene in the eastern Tibetan Plateau are shown to follow two basic models based on the reliable dating and high-resolution monsoon proxies determinations, one being a synchronous model in that both summer and winter monsoons are strengthening or decreasing, and the other to form a complementary pattern. These two different patterns evenly interact with each other on different time scales and together compose a complicated monsoon climatic model in this region. The climatic condition integrated by winter and summer monsoons is synchronous to the global pattern, which also shows the instability of the Holocene climate on centennial-millennial timescale. The abrupt monsoon event in about 6.2 ka cal.BP is much more severe than that in ca. 8.0 ka cal. BP, which indicates the regional character of the Asian monsoon and that the Asian monsoon climate is indeed a window on the global climate system.

  2. High geothermal heat flux measured below the West Antarctic Ice Sheet.

    Science.gov (United States)

    Fisher, Andrew T; Mankoff, Kenneth D; Tulaczyk, Slawek M; Tyler, Scott W; Foley, Neil

    2015-07-01

    The geothermal heat flux is a critical thermal boundary condition that influences the melting, flow, and mass balance of ice sheets, but measurements of this parameter are difficult to make in ice-covered regions. We report the first direct measurement of geothermal heat flux into the base of the West Antarctic Ice Sheet (WAIS), below Subglacial Lake Whillans, determined from the thermal gradient and the thermal conductivity of sediment under the lake. The heat flux at this site is 285 ± 80 mW/m(2), significantly higher than the continental and regional averages estimated for this site using regional geophysical and glaciological models. Independent temperature measurements in the ice indicate an upward heat flux through the WAIS of 105 ± 13 mW/m(2). The difference between these heat flux values could contribute to basal melting and/or be advected from Subglacial Lake Whillans by flowing water. The high geothermal heat flux may help to explain why ice streams and subglacial lakes are so abundant and dynamic in this region.

  3. Determination of biotin in Antarctic krill (Euphausia superba) by high-performance TLC with different post-chromatographic derivatizations.

    Science.gov (United States)

    Teo, Peishan; Liu, Daicheng

    2013-08-01

    A new efficient method was developed to detect biotin in Antarctic krill by Vis-absorbance detection. DMF was used after chloroform pretreatment to extract biotin and two chromogenic methods were developed. The development system consisted of dichloromethane/dimethylcarbinol/methanol/glacial acetic acid (3:3:2:0.015, v/v/v/v). Samples were separated on precoated silica gel GF254 high-performance TLC plates. Densitometric analysis of biotin was carried out in the absorbance mode at 400 and 530 nm. The biotin content was determined to be 1.0948 ± 0.0097 and 1.1212 ± 0.0155 mg/g in Antarctic krill with the two chromogenic methods, which had no significant difference.

  4. Antarctic Fishes.

    Science.gov (United States)

    Eastman, Joseph T.; DeVries, Arthur L.

    1986-01-01

    Explains the adaptations to Antarctic waters that Notothenioidei, a group of advanced bony fishes, have exhibited. Discusses the fishes' mechanisms of production of antifreeze properties and their capacities for neutral buoyancy in water. (ML)

  5. Mitochondrial genome sequences of Artemia tibetiana and Artemia urmiana: assessing molecular changes for high plateau adaptation.

    Science.gov (United States)

    Zhang, Hangxiao; Luo, Qibin; Sun, Jing; Liu, Fei; Wu, Gang; Yu, Jun; Wang, Weiwei

    2013-05-01

    Brine shrimps, Artemia (Crustacea, Anostraca), inhabit hypersaline environments and have a broad geographical distribution from sea level to high plateaus. Artemia therefore possess significant genetic diversity, which gives them their outstanding adaptability. To understand this remarkable plasticity, we sequenced the mitochondrial genomes of two Artemia tibetiana isolates from the Tibetan Plateau in China and one Artemia urmiana isolate from Lake Urmia in Iran and compared them with the genome of a low-altitude Artemia, A. franciscana. We compared the ratio of the rate of nonsynonymous (Ka) and synonymous (Ks) substitutions (Ka/Ks ratio) in the mitochondrial protein-coding gene sequences and found that atp8 had the highest Ka/Ks ratios in comparisons of A. franciscana with either A. tibetiana or A. urmiana and that atp6 had the highest Ka/Ks ratio between A. tibetiana and A. urmiana. Atp6 may have experienced strong selective pressure for high-altitude adaptation because although A. tibetiana and A. urmiana are closely related they live at different altitudes. We identified two extended termination-associated sequences and three conserved sequence blocks in the D-loop region of the mitochondrial genomes. We propose that sequence variations in the D-loop region and in the subunits of the respiratory chain complexes independently or collectively contribute to the adaptation of Artemia to different altitudes.

  6. A quasi-Lagrangian coordinate system based on high resolution tracer observations: implementation for the Antarctic polar vortex

    Directory of Open Access Journals (Sweden)

    E. V. Ivanova

    2008-08-01

    Full Text Available In order to quantitatively analyse the chemical and dynamical evolution of the polar vortex it has proven extremely useful to work with coordinate systems that follow the vortex flow. We propose here a two-dimensional quasi-Lagrangian coordinate system {χi, Δχi}, based on the mixing ratio of a long-lived stratospheric trace gas i, and its systematic use with i = N2O, in order to describe the structure of a well-developed Antarctic polar vortex. In the coordinate system {χi, Δχi} the mixing ratio χi is the vertical coordinate and Δχi = χi(Θ−χivort(Θ is the meridional coordinate (χivort(Θ being a vertical reference profile in the vortex core. The quasi-Lagrangian coordinates {χi, Δχi} persist for much longer time than standard isentropic coordinates, potential temperature Θ and equivalent latitude φe, do not require explicit reference to geographic space, and can be derived directly from high-resolution in situ measurements. They are therefore well-suited for studying the evolution of the Antarctic polar vortex throughout the polar winter with respect to the relevant chemical and microphysical processes. By using the introduced coordinate system {χN2O, ΔχN2O} we analyze the well-developed Antarctic vortex investigated during the APE-GAIA (Airborne Polar Experiment – Geophysica Aircraft in Antarctica – 1999 campaign (Carli et al., 2000. A criterion, which uses the local in-situ measurements of χi=χi(Θ and attributes the inner vortex edge to a rapid change (δ-step in the

  7. A quasi-Lagrangian coordinate system based on high resolution tracer observations: implementation for the Antarctic polar vortex

    Science.gov (United States)

    Ivanova, E. V.; Volk, C. M.; Riediger, O.; Klein, H.; Sitnikov, N. M.; Ulanovskii, A. E.; Yushkov, V. A.; Ravegnani, F.; Möbius, T.; Schmidt, U.

    2008-08-01

    In order to quantitatively analyse the chemical and dynamical evolution of the polar vortex it has proven extremely useful to work with coordinate systems that follow the vortex flow. We propose here a two-dimensional quasi-Lagrangian coordinate system {χi, Δχi}, based on the mixing ratio of a long-lived stratospheric trace gas i, and its systematic use with i = N2O, in order to describe the structure of a well-developed Antarctic polar vortex. In the coordinate system {χi, Δχi} the mixing ratio χi is the vertical coordinate and Δχi = χi(Θ)-χivort(Θ) is the meridional coordinate (χivort(Θ) being a vertical reference profile in the vortex core). The quasi-Lagrangian coordinates {χi, Δχi} persist for much longer time than standard isentropic coordinates, potential temperature Θ and equivalent latitude φe, do not require explicit reference to geographic space, and can be derived directly from high-resolution in situ measurements. They are therefore well-suited for studying the evolution of the Antarctic polar vortex throughout the polar winter with respect to the relevant chemical and microphysical processes. By using the introduced coordinate system {χN2O, ΔχN2O} we analyze the well-developed Antarctic vortex investigated during the APE-GAIA (Airborne Polar Experiment - Geophysica Aircraft in Antarctica - 1999) campaign (Carli et al., 2000). A criterion, which uses the local in-situ measurements of χi=χi(Θ) and attributes the inner vortex edge to a rapid change (δ-step) in the meridional profile of the mixing ratio χi, is developed to determine the (Antarctic) inner vortex edge. In turn, we suggest that the outer vortex edge of a well-developed Antarctic vortex can be attributed to the position of a local minimum of the χH2O gradient in the polar vortex area. For a well-developed Antarctic vortex, the ΔχN2O-parametrization of tracer-tracer relationships allows to distinguish the tracer inter-relationships in the vortex core, vortex

  8. Chemical Records in Snowpits from High Altitude Glaciers in the Tibetan Plateau and Its Surroundings

    Science.gov (United States)

    Zhang, Yulan; Kang, Shichang; Zhang, Qianggong; Gao, Tanguang; Guo, Junming; Grigholm, Bjorn; Huang, Jie; Sillanpää, Mika; Li, Xiaofei; Du, Wentao; Li, Yang; Ge, Xinlei

    2016-01-01

    Glaciochemistry can provide important information about climatic change and environmental conditions, as well as for testing regional and global atmospheric trace transport models. In this study, δ18O and selected chemical constituents records in snowpits collected from eight glaciers in the Tibetan Plateau and adjacent areas have been investigated. Drawing on the integrated data, our study summarized the seasonal and spatial characteristics of snow chemistry, and their potential sources. Distinct seasonal patterns of δ18O values in snowpits indicated more negative in the south TP controlled by Indian monsoon, and less negative in the north TP and Tien Shan. Overall increasing concentrations of microparticles and crustal ions from south to north indicated a strength of dust deposition on glaciers from semi-arid and arid regions. Principal component analysis and air mass trajectories suggested that chemical constituents were mainly attributable to crustal sources as demonstrated by the high concentrations of ions occurring during the non-monsoon seasons. Nevertheless, other sources, such as anthropogenic pollution, played an important role on chemical variations of glaciers near the human activity centers. This study concluded that air mass transport from different sources played important roles on the spatial distributions and seasonality of glaciochemistry. PMID:27186638

  9. Chemical Records in Snowpits from High Altitude Glaciers in the Tibetan Plateau and Its Surroundings.

    Directory of Open Access Journals (Sweden)

    Yulan Zhang

    Full Text Available Glaciochemistry can provide important information about climatic change and environmental conditions, as well as for testing regional and global atmospheric trace transport models. In this study, δ18O and selected chemical constituents records in snowpits collected from eight glaciers in the Tibetan Plateau and adjacent areas have been investigated. Drawing on the integrated data, our study summarized the seasonal and spatial characteristics of snow chemistry, and their potential sources. Distinct seasonal patterns of δ18O values in snowpits indicated more negative in the south TP controlled by Indian monsoon, and less negative in the north TP and Tien Shan. Overall increasing concentrations of microparticles and crustal ions from south to north indicated a strength of dust deposition on glaciers from semi-arid and arid regions. Principal component analysis and air mass trajectories suggested that chemical constituents were mainly attributable to crustal sources as demonstrated by the high concentrations of ions occurring during the non-monsoon seasons. Nevertheless, other sources, such as anthropogenic pollution, played an important role on chemical variations of glaciers near the human activity centers. This study concluded that air mass transport from different sources played important roles on the spatial distributions and seasonality of glaciochemistry.

  10. The ARM West Antarctic Radiation Experiment (AWARE)

    Science.gov (United States)

    Lubin, Dan; Bromwich, David; Vogelmann, Andrew; Verlinde, Johannes; Russell, Lynn

    2016-04-01

    West Antarctica is one of the most rapidly warming regions on Earth, and its changing climate in both atmosphere and ocean is linked to loss of Antarctic ice mass and global sea level rise. The specific mechanisms for West Antarctic Ice Sheet (WAIS) warming are not fully understood, but are hypothesized to involve linkage between moisture from Southern Ocean storm tracks and the surface energy balance over the WAIS, and related teleconnections with subtropical and tropical meteorology. This present lack of understanding has motivated a climate science and cloud physics campaign jointly supported by the US National Science Foundation (NSF) and Department of Energy (DOE), called the Atmospheric Radiation Measurement Program (ARM) West Antarctic Radiation Experiment (AWARE). The DOE's second ARM Mobile Facility (AMF2) was deployed to McMurdo Station on Ross Island in November 2015 and will operate through December 2016. The AMF2 includes (1) cloud research radars, both scanning and zenith, operating in the Ka- and X-bands, (2) high spectral resolution and polarized micropulse lidars, and (3) a suite of shortwave and longwave broadband and spectral radiometers. A second suite of instruments is deployed at the WAIS Divide Ice Camp on the West Antarctic plateau during December 2015 and January 2016. The WAIS instrument suite provides (1) measurement of all surface energy balance components, (2) a polarized micropulse lidar and shortwave spectroradiometer, (3) microwave total water column measurement, and (4) four times daily rawinsonde launches which are the first from West Antarctica since 1967. There is a direct linkage between the WAIS instrument suite and the AMF2 at McMurdo, in that air masses originating in Southern Ocean storm tracks that are driven up over the WAIS often subsequently descend over the Ross Ice Shelf and arrive at Ross Island. Preliminary data are already illustrating the prevalence of mixed-phase clouds and their role in the surface energy balance

  11. Antarctic contribution to global sea level in a high CO2 world

    Science.gov (United States)

    Golledge, Nicholas R.; Levy, Richard H.; Naish, Timothy R.; McKay, Robert M.; Gasson, Edward G. W.; Kowalewski, Douglas E.; Fogwill, Christopher J.

    2016-04-01

    In 2014 atmospheric CO2 levels exceeded 400 ppm for the first time since the early Pliocene (3.5-5 Ma). Although the rise in global mean surface temperatures that will accompany continued increases in CO2 is hard to predict, proxy evidence from the early Pliocene suggest that these CO2 concentrations, together with higher-than-present summer insolation, were associated with circum-Antarctic seas 2-4° C warmer than present and air temperatures 6-10° C warmer. Large sectors of the present-day Antarctic ice sheet rest on bedrock below sea level, and as such these areas are more sensitive to environmental forcings than ice grounded above sea level because the geometry of their submarine beds allows for runaway retreat in response to relatively small initial perturbations (Thomas & Bentley, 1978; Mengel & Levermann, 2014). Here we present an ice-sheet model ensemble that explores the consequences of a range of air and ocean warming scenarios representative of a higher-than-present CO2 world. Using circum-Antarctic palaeoenvironmental proxy data to constrain the range of likely conditions adjacent to the continent we calculate probability densities of likely sea-level equivalent ice-sheet volume changes relative to present, together with their associated uncertainties, for a range of timeframes. We find that multi-metre sea-level contributions are likely within centuries, increasing to over ten metres within subsequent millennia. Our results are consistent with empirically-based sea-level reconstructions for the Pliocene, and in addition offer new insights into basin-specific responses within the Antarctic continent.

  12. High Abundance of the Epibenthic Trachymedusa Ptychogastria polaris Allman, 1878 (Hydrozoa, Trachylina) in Subpolar Fjords along the West Antarctic Peninsula

    Science.gov (United States)

    Smith, Craig R.; Lindsay, Dhugal J.; Bentlage, Bastian; Youngbluth, Marsh J.

    2017-01-01

    Medusae can be conspicuous and abundant members of seafloor communities in deep-sea benthic boundary layers. The epibenthic trachymedusa, Ptychogastria polaris Allman, 1878 (Hydrozoa: Trachylina: Ptychogastriidae) occurs in the cold, high latitude systems of both the northern and southern hemispheres, with a circumpolar distribution in Arctic and sub-Arctic areas, and disjunct reports of a few individuals from Antarctica. In January-February 2010, during benthic megafaunal photosurveys in three subpolar fjords along the West Antarctic Peninsula (Andvord, Flandres and Barilari Bays), P. polaris was recorded in Antarctic Peninsula waters. The trachymedusa, identified from megacore-collected specimens, was a common component of the epifauna in the sediment floored basins at 436–725 m depths in Andvord and Flandres Bays, reaching densities up to 13 m-2, with mean densities in individual basins ranging from 0.06 to 4.19 m-2. These densities are 2 to 400-fold higher than previously reported for P. polaris in either the Arctic or Antarctic. This trachymedusa had an aggregated distribution, occurring frequently in Andvord Bay, but was often solitary in Flandres Bay, with a distribution not significantly different from random. Epibenthic individuals were similar in size, typically measuring 15–25 mm in bell diameter. A morphologically similar trachymedusa, presumably the same species, was also observed in the water column near the bottom in all three fjords. This benthopelagic form attained abundances of up to 7 m-2 of seafloor; however, most P. polaris (~ 80%), were observed on soft sediments. Our findings indicate that fjords provide a prime habitat for the development of dense populations of P. polaris, potentially resulting from high and varied food inputs to the fjord floors. Because P. polaris resides in the water column and at the seafloor, large P. polaris populations may contribute significantly to pelagic-benthic coupling in the WAP fjord ecosystems. PMID

  13. High Abundance of the Epibenthic Trachymedusa Ptychogastria polaris Allman, 1878 (Hydrozoa, Trachylina) in Subpolar Fjords along the West Antarctic Peninsula.

    Science.gov (United States)

    Grange, Laura J; Smith, Craig R; Lindsay, Dhugal J; Bentlage, Bastian; Youngbluth, Marsh J

    2017-01-01

    Medusae can be conspicuous and abundant members of seafloor communities in deep-sea benthic boundary layers. The epibenthic trachymedusa, Ptychogastria polaris Allman, 1878 (Hydrozoa: Trachylina: Ptychogastriidae) occurs in the cold, high latitude systems of both the northern and southern hemispheres, with a circumpolar distribution in Arctic and sub-Arctic areas, and disjunct reports of a few individuals from Antarctica. In January-February 2010, during benthic megafaunal photosurveys in three subpolar fjords along the West Antarctic Peninsula (Andvord, Flandres and Barilari Bays), P. polaris was recorded in Antarctic Peninsula waters. The trachymedusa, identified from megacore-collected specimens, was a common component of the epifauna in the sediment floored basins at 436-725 m depths in Andvord and Flandres Bays, reaching densities up to 13 m-2, with mean densities in individual basins ranging from 0.06 to 4.19 m-2. These densities are 2 to 400-fold higher than previously reported for P. polaris in either the Arctic or Antarctic. This trachymedusa had an aggregated distribution, occurring frequently in Andvord Bay, but was often solitary in Flandres Bay, with a distribution not significantly different from random. Epibenthic individuals were similar in size, typically measuring 15-25 mm in bell diameter. A morphologically similar trachymedusa, presumably the same species, was also observed in the water column near the bottom in all three fjords. This benthopelagic form attained abundances of up to 7 m-2 of seafloor; however, most P. polaris (~ 80%), were observed on soft sediments. Our findings indicate that fjords provide a prime habitat for the development of dense populations of P. polaris, potentially resulting from high and varied food inputs to the fjord floors. Because P. polaris resides in the water column and at the seafloor, large P. polaris populations may contribute significantly to pelagic-benthic coupling in the WAP fjord ecosystems.

  14. Multiple-plateau structure and scaling relation in photoelectron spectra of high-order above-threshold ionization

    Institute of Scientific and Technical Information of China (English)

    Wu Yan; Ye Hui-Liang; Zhang Jing-Tao; Guo Dong-Sheng

    2012-01-01

    By developing a full quantum scattering theory of high-order above-threshold ionization,we study the energy spectra and the angular distributions of photoelectrons from atoms with intense laser fields shining on them.We find that real rescattering can occur many times,and even infinite times.The photoelectrons from the rescattering process form a broad plateau in the kinetic-energy spectrum.We further disclose a multiple-plateau structure formed by the high-energy photoelectrons,which absorb many photons during the rescattering process.Moreover,we find that both the angular distributions and the kinetic-energy spectra of photoelectrons obey the same scaling law as that for directly emitted photoelectrons.

  15. Mapping sub-antarctic cushion plants using random forests to combine very high resolution satellite imagery and terrain modelling.

    Directory of Open Access Journals (Sweden)

    Phillippa K Bricher

    Full Text Available Monitoring changes in the distribution and density of plant species often requires accurate and high-resolution baseline maps of those species. Detecting such change at the landscape scale is often problematic, particularly in remote areas. We examine a new technique to improve accuracy and objectivity in mapping vegetation, combining species distribution modelling and satellite image classification on a remote sub-Antarctic island. In this study, we combine spectral data from very high resolution WorldView-2 satellite imagery and terrain variables from a high resolution digital elevation model to improve mapping accuracy, in both pixel- and object-based classifications. Random forest classification was used to explore the effectiveness of these approaches on mapping the distribution of the critically endangered cushion plant Azorella macquariensis Orchard (Apiaceae on sub-Antarctic Macquarie Island. Both pixel- and object-based classifications of the distribution of Azorella achieved very high overall validation accuracies (91.6-96.3%, κ = 0.849-0.924. Both two-class and three-class classifications were able to accurately and consistently identify the areas where Azorella was absent, indicating that these maps provide a suitable baseline for monitoring expected change in the distribution of the cushion plants. Detecting such change is critical given the threats this species is currently facing under altering environmental conditions. The method presented here has applications to monitoring a range of species, particularly in remote and isolated environments.

  16. Norhla: Restoring the glory of khullu wool for social development and environmental protection in the High Tibetan Plateau

    OpenAIRE

    Guesné, Jean-Marc; Michaut-Denizeau, Anne; Sireyjol, Alice

    2012-01-01

    For centuries, the local communities of yaks’ transhumant cattle farmers of the Tibetan High plateau have lived on their yak breeding activity, providing them with all they need: milk, a source of butter and cheese, and hair, which they weave into the heavy black tents that characterize the nomadic population. In the last decade, however, changes occurred that have destabilized this activity. The changes are three-fold: (1) increasing economic difficulty to live from this activity (Melvyn et ...

  17. Revealing past environmental changes on the Antarctic Peninsula by analyzing high resolution sedimentary records from Lake Esmeralda, Vega Island

    Science.gov (United States)

    Píšková, Anna; Nývlt, Daniel; Roman, Matěj; Lirio, Juan Manuel; Kopalová, Kateřina

    2017-04-01

    Topographically and climatically, the environment of the Antarctic Peninsula (AP) differs significantly from Continental Antarctica. The AP forms an unbroken chain of rugged, alpine topography, which forms a climatic barrier separating the warmer Bellingshausen Sea on the western coast from the colder Weddell Sea on the east. The AP has experienced one of the highest temperature increases on Earth in the second half of the 20th century as a response to the ongoing global warming (Turner et al., 2005). However, the last decade was colder and a significant decrease in air temperature was detected especially in the north-eastern part of the AP (Turner et al., 2016; Oliva et al., 2017). The extreme sensitivity of the area to climate change represents exceptional potential for AP palaeoclimatic records either from marine, lacustrine, or ice cores. We have analysed several sedimentary cores from yet unstudied Lake Esmeralda, which was formed as a result of the last deglaciation during the Pleistocene/Holocene transition. We here focus on the longest (177 cm) core that could record environmental changes of the past millennia. In order to describe both inorganic and organic components of the sediment we used a combination of the following methods: XRF, XRD, magnetic susceptibility measurement, chemical analysis for determination of cation exchange capacity, grain size analysis, geochemical analysis (TIC, TOC, TS), high pressure liquid chromatography (HPLC) and diatom community analysis. This combination of methods gave us an insight in the past environmental changes in the lake catchment as well as in the lake body. More specifically it enabled us to define periods of enhanced weathering and to distinguish colder and warmer phases. The preliminary results will be completed with age-depth model resulting in a high resolution multi-proxy record that will contribute to a better, more detailed picture of the past climatic and environmental changes in the north-eastern AP

  18. High Prevalence of Gammaproteobacteria in the Sediments of Admiralty Bay and North Bransfield Basin, Northwestern Antarctic Peninsula

    Science.gov (United States)

    Franco, Diego C.; Signori, Camila N.; Duarte, Rubens T. D.; Nakayama, Cristina R.; Campos, Lúcia S.; Pellizari, Vivian H.

    2017-01-01

    Microorganisms dominate most Antarctic marine ecosystems, in terms of biomass and taxonomic diversity, and play crucial role in ecosystem functioning due to their high metabolic plasticity. Admiralty Bay is the largest bay on King George Island (South Shetland Islands, Antarctic Peninsula) and a combination of hydro-oceanographic characteristics (bathymetry, sea ice and glacier melting, seasonal entrance of water masses, turbidity, vertical fluxes) create conditions favoring organic carbon deposition on the seafloor and microbial activities. We sampled surface sediments from 15 sites across Admiralty Bay (100–502 m total depth) and the adjacent North Bransfield Basin (693–1147 m), and used the amplicon 454-sequencing of 16S rRNA gene tags to compare the bacterial composition, diversity, and microbial community structure across environmental parameters (sediment grain size, pigments and organic nutrients) between the two areas. Marine sediments had a high abundance of heterotrophic Gammaproteobacteria (92.4% and 83.8% inside and outside the bay, respectively), followed by Alphaproteobacteria (2.5 and 5.5%), Firmicutes (1.5 and 1.6%), Bacteroidetes (1.1 and 1.7%), Deltaproteobacteria (0.8 and 2.5%) and Actinobacteria (0.7 and 1.3%). Differences in alpha-diversity and bacterial community structure were found between the two areas, reflecting the physical and chemical differences in the sediments, and the organic matter input. PMID:28210255

  19. Genetic Convergence in the Adaptation of Dogs and Humans to the High-Altitude Environment of the Tibetan Plateau

    Science.gov (United States)

    Wang, Guo-Dong; Fan, Ruo-Xi; Zhai, Weiwei; Liu, Fei; Wang, Lu; Zhong, Li; Wu, Hong; Yang, He-Chuan; Wu, Shi-Fang; Zhu, Chun-Ling; Li, Yan; Gao, Yun; Ge, Ri-Li; Wu, Chung-I; Zhang, Ya-Ping

    2014-01-01

    The high-altitude hypoxic environment represents one of the most extreme challenges for mammals. Previous studies of humans on the Tibetan plateau and in the Andes Mountains have identified statistical signatures of selection in different sets of loci. Here, we first measured the hemoglobin levels in village dogs from Tibet and those from Chinese lowlands. We found that the hemoglobin levels are very similar between the two groups, suggesting that Tibetan dogs might share similar adaptive strategies as the Tibetan people. Through a whole-genome sequencing approach, we have identified EPAS1 and HBB as candidate genes for the hypoxic adaptation on the Tibetan plateau. The population genetic analysis shows a significant convergence between humans and dogs in Tibet. The similarities in the sets of loci that exhibit putative signatures of selection and the hemoglobin levels between humans and dogs of the same environment, but not between human populations in different regions, suggests an extraordinary landscape of convergent evolution between human beings and their best friend on the Tibetan plateau. PMID:25091388

  20. Biodiversity and biogeography of Antarctic and sub-Antarctic mollusca

    Science.gov (United States)

    Linse, Katrin; Griffiths, Huw J.; Barnes, David K. A.; Clarke, Andrew

    2006-04-01

    For many decades molluscan data have been critical to the establishment of the concept of a global-scale increase in species richness from the poles to the equator. Low polar diversity is key to this latitudinal cline in diversity. Here we investigate richness patterns in the two largest classes of molluscs at both local and regional scales throughout the Southern Ocean. We show that biodiversity is very patchy in the Southern Ocean (at the 1000-km scale) and test the validity of historical biogeographic sub-regions and provinces. We used multivariate analysis of biodiversity patterns at species, genus and family levels to define richness hotspots within the Southern Ocean and transition areas. This process identified the following distinct sub-regions in the Southern Ocean: Antarctic Peninsula, Weddell Sea, East Antarctic—Dronning Maud Land, East Antarctic—Enderby Land, East Antarctic—Wilkes Land, Ross Sea, and the independent Scotia arc and sub Antarctic islands. Patterns of endemism were very different between the bivalves and gastropods. On the basis of distributional ranges and radiation centres of evolutionarily successful families and genera we define three biogeographic provinces in the Southern Ocean: (1) the continental high Antarctic province excluding the Antarctic Peninsula, (2) the Scotia Sea province including the Antarctic Peninsula, and (3) the sub Antarctic province comprising the islands in the vicinity of the Antarctic Circumpolar Current.

  1. Adaption to High Altitude: An Evaluation of the Storage Quality of Suspended Red Blood Cells Prepared from the Whole Blood of Tibetan Plateau Migrants.

    Directory of Open Access Journals (Sweden)

    Rui Zhong

    Full Text Available Hypoxia has been reported to cause the significant enhancement of hemoglobin (Hb and hematocrit (Hct, which stabilizes at relatively high levels after an individual ascends to a high altitude. However, the quality of the suspended red blood cells (SRBCs obtained from individuals at high altitudes such as Tibetan plateau migrants after storage has not been studied. In this study, we compared the storage quality of SRBCs prepared from Tibetan plateau and Deyang lowland populations by adding a normal volume of mannitol-adenine-phosphate (MAP, which is a common additive solution used in blood storage in Asian countries. The storage cell characteristics were examined on days 1, 7, 14 and 35.We found higher Hct and Hb levels and viscosity in the high altitude samples. The metabolic rates, including those for electrolytes and lactate, were higher in plateau SRBCs than in lowland SRBCs; these findings were consistent with the higher osmotic fragility and hemolysis of plateau SRBCs throughout the entire storage period. In addition, the reduction rates of 2,3-diphosphoglycerate (2,3-DPG and oxygen tension to attain 50% oxygen saturation of Hb (P50 in plateau SRBCs were higher than those in lowland SRBCs, and the oxygen delivering capacity in plateau SRBCs was weaker than that in lowland SRBCs. We concluded that the storage quality of plateau SRBCs was inferior to that of lowland SRBCs when using the same concentration of MAP. We suggested that the optimal formula, including the MAP concentration or even a new additive solution, to store the plateau SRBCs must be assessed and regulated.

  2. Observation of high energy atmospheric neutrinos with antarctic muon and neutrino detector array

    Energy Technology Data Exchange (ETDEWEB)

    Ahrens, J.; Andres, E.; Bai, X.; Barouch, G.; Barwick, S.W.; Bay, R.C.; Becka, T.; Becker, K.-H.; Bertrand, D.; Binon, F.; Biron, A.; Booth, J.; Botner, O.; Bouchta, A.; Bouhali, O.; Boyce, M.M.; Carius, S.; Chen, A.; Chirkin, D.; Conrad, J.; Cooley, J.; Costa, C.G.S.; Cowen, D.F.; Dalberg, E.; De Clercq, C.; DeYoung, T.; Desiati, P.; Dewulf, J.-P.; Doksus, P.; Edsjo, J.; Ekstrom, P.; Feser, T.; Frere, J.-M.; Gaisser, T.K.; Gaug, M.; Goldschmidt, A.; Hallgren, A.; Halzen, F.; Hanson, K.; Hardtke, R.; Hauschildt, T.; Hellwig, M.; Heukenkamp, H.; Hill, G.C.; Hulth, P.O.; Hundertmark, S.; Jacobsen, J.; Karle, A.; Kim, J.; Koci, B.; Kopke, L.; Kowalski, M.; Lamoureux, J.I.; Leich, H.; Leuthold, M.; Lindahl, P.; Liubarsky, I.; Loaiza, P.; Lowder, D.M.; Madsen, J.; Marciniewski, P.; Matis, H.S.; McParland, C.P.; Miller, T.C.; Minaeva, Y.; Miocinovic, P.; Mock, P.C.; Morse, R.; Neunhoffer, T.; Niessen, P.; Nygren, D.R.; Ogelman, H.; Olbrechts, Ph.; Perez de los Heros, C.; Pohl, A.C.; Porrata, R.; Price, P.B.; Przybylski, G.T.; Rawlins, K.; Reed, C.; Rhode, W.; Ribordy, M.; Richter, S.; Rodriguez Martino, J.; Romenesko, P.; Ross, D.; Sander, H.-G.; Schmidt, T.; Schneider, D.; Schwarz, R.; Silvestri, A.; Solarz, M.; Spiczak, G.M.; Spiering, C.; Starinsky, N.; Steele, D.; Steffen, P.; Stokstad, R.G.; Streicher, O.; Sudhoff, P.; Sulanke, K.-H.; Taboada, I.; Thollander, L.; Thon, T.; Tilav, S.; Vander Donckt, M.; Walck, C.; Weinheimer, C.; Wiebusch, C.H.; Wiedeman, C.; Wischnewski, R.; Wissing, H.; Woschnagg, K.; Wu, W.; Yodh, G.; Young, S.

    2002-05-07

    The Antarctic Muon and Neutrino Detector Array (AMANDA) began collecting data with ten strings in 1997. Results from the first year of operation are presented. Neutrinos coming through the Earth from the Northern Hemisphere are identified by secondary muons moving upward through the array. Cosmic rays in the atmosphere generate a background of downward moving muons, which are about 10{sup 6} times more abundant than the upward moving muons. Over 130 days of exposure, we observed a total of about 300 neutrino events. In the same period, a background of 1.05 x 10{sup 9} cosmic ray muon events was recorded. The observed neutrino flux is consistent with atmospheric neutrino predictions. Monte Carlo simulations indicate that 90 percent of these events lie in the energy range 66 GeV to 3.4 TeV. The observation of atmospheric neutrinos consistent with expectations establishes AMANDA-B10 as a working neutrino telescope.

  3. Ornithological monitoring of the wind farms of the Garrigue high plateau (Aude); Suivi ornithologique des parcs eoliens du Plateau de Garrigue Haute (Aude)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-07-01

    This document presents the monitoring of the premarital migration 2001 in the wind farm of Corbieres-Maritime on the Garrigue Haute plateau. It aims to study the wind turbines impacts and risks on the migration. In spite of a weak mortality, the number of observed modifications in the birds habits at the approach of the wind turbines confirms the necessity of taking into account the migration phenomena in the wind farms projects. (A.L.B.)

  4. The ARM West Antarctic Radiation Experiment (AWARE)

    Science.gov (United States)

    Scott, R. C.; Lubin, D.; Bromwich, D. H.; Vogelmann, A. M.; Verlinde, J.; Russell, L. M.

    2016-12-01

    West Antarctica is one of the most rapidly warming regions on Earth, and its changing climate in both atmosphere and ocean is linked to loss of Antarctic ice mass and global sea level rise. The specific mechanisms for West Antarctic Ice Sheet (WAIS) warming are not fully understood, but are hypothesized to involve linkage between moisture from Southern Ocean storm tracks and the surface energy balance over the WAIS, and related teleconnections with subtropical and tropical meteorology. This present lack of understanding has motivated a climate science and cloud physics campaign jointly supported by the US National Science Foundation (NSF) and Department of Energy (DOE), called the Atmospheric Radiation Measurement Program (ARM) West Antarctic Radiation Experiment (AWARE). The DOE's second ARM Mobile Facility (AMF2) was deployed to McMurdo Station on Ross Island in November 2015 and will operate through December 2016. The AMF2 includes (1) cloud research radars, both scanning and zenith, operating in the Ka- and X-bands, (2) high spectral resolution and polarized micropulse lidars, and (3) a suite of shortwave and longwave broadband and spectral radiometers. A second suite of instruments is deployed at the WAIS Divide Ice Camp on the West Antarctic plateau during December 2015 and January 2016. The WAIS instrument suite provides (1) measurement of all surface energy balance components, (2) a polarized micropulse lidar and shortwave spectroradiometer, (3) microwave total water column measurement, and (4) four times daily rawinsonde launches which are the first from West Antarctica since 1967. There is a direct linkage between the WAIS instrument suite and the AMF2 at McMurdo, in that air masses originating in Southern Ocean storm tracks that are driven up over the WAIS often subsequently descend over the Ross Ice Shelf and arrive at Ross Island. Preliminary data are already illustrating (1) the prevalence of single- versus mixed-phase clouds and their role in the

  5. The effects of Forbush decreases on Antarctic climate variability: a re-assessment

    Directory of Open Access Journals (Sweden)

    B. A. Laken

    2009-04-01

    Full Text Available In an attempt to test the validity of a relationship between Galactic cosmic rays (GCRs and cloud cover, a range of past studies have performed composite analysis based around Forbush decrease (FD events. These studies have produced a range of conflicting results, consequently reducing confidence in the existence of a GCR-cloud link. A potential reason why past FD based studies have failed to identify a consistent relationship may be that the FD events themselves are too poorly defined, and require calibration prior to analysis. Drawing from an initial sample of 48 FD events taken from multiple studies this work attempts to isolate a GCR decrease of greater magnitude and coherence than has been demonstrated by past studies. After this calibration composite analysis revealed increases in high level (10–180 mb cloud cover (of ~20% occurred over the Antarctic plateau in conjunction with decreases in the rate of GCR flux during austral winter (these results are broadly opposite to those of past studies. The cloud changes occurred in conjunction with locally significant surface level air temperature increases over the Antarctic plateau (~4 K and temperature decreases over the Ross Ice Sheet (~8 K. These temperature variations appear to be indirectly linked to cloud via anomalous surface level winds rather than a direct radiative forcing. These results provide good evidence of a relationship between daily timescale GCR variations and Antarctic climate variability.

  6. Late Miocene-Pliocene Asian monsoon intensification linked to Antarctic ice-sheet growth

    Science.gov (United States)

    Ao, Hong; Roberts, Andrew P.; Dekkers, Mark J.; Liu, Xiaodong; Rohling, Eelco J.; Shi, Zhengguo; An, Zhisheng; Zhao, Xiang

    2016-06-01

    Environmental conditions in one of Earth's most densely populated regions, East Asia, are dominated by the monsoon. While Quaternary monsoon variability is reasonably well understood, pre-Quaternary monsoon variability and dynamics remain enigmatic. In particular, little is known about potential relationships between northern hemispheric monsoon response and major Cenozoic changes in Antarctic ice cover. Here we document long-term East Asian summer monsoon (EASM) intensification through the Late Miocene-Pliocene (∼8.2 to 2.6 Ma), and attribute this to progressive Antarctic glaciation. Our new high-resolution magnetic records of long-term EASM intensification come from the Late Miocene-Pliocene Red Clay sequence on the Chinese Loess Plateau; we identify underlying mechanisms using a numerical climate-model simulation of EASM response to an idealized stepwise increase in Antarctic ice volume. We infer that progressive Antarctic glaciation caused intensification of the cross-equatorial pressure gradient between an atmospheric high-pressure cell over Australia and a low-pressure cell over mid-latitude East Asia, as well as intensification of the cross-equatorial sea-surface temperature (SST) gradient. These combined atmospheric and oceanic adjustments led to EASM intensification. Our findings offer a new and more global perspective on the controls behind long-term Asian monsoon evolution.

  7. Late Miocene-Pliocene Asian monsoon intensification linked to Antarctic ice-sheet growth

    Science.gov (United States)

    Ao, H.; Roberts, A. P.; Dekkers, M. J.; Liu, X.; Rohling, E. J.; Shi, Z.; An, Z.; Zhao, X.

    2016-12-01

    Environmental conditions in one of Earth's most densely populated regions, East Asia, are dominated by the monsoon. While Quaternary monsoon variability is reasonably well understood, pre-Quaternary monsoon variability and dynamics remain enigmatic. In particular, little is known about potential relationships between northern hemispheric monsoon response and major Cenozoic changes in Antarctic ice cover. Here we document long-term East Asian summer monsoon (EASM) intensification through the Late Miocene-Pliocene (˜8.2 to 2.6 Ma), and attribute this to progressive Antarctic glaciation. Our new high-resolution magnetic records of long-term EASM intensification come from the Late Miocene-Pliocene Red Clay sequence on the Chinese Loess Plateau; we identify underlying mechanisms using a numerical climate-model simulation of EASM response to an idealized stepwise increase in Antarctic ice volume. We infer that progressive Antarctic glaciation caused intensification of the cross-equatorial pressure gradient between an atmospheric high-pressure cell over Australia and a low-pressure cell over mid-latitude East Asia, as well as intensification of the cross-equatorial sea-surface temperature (SST) gradient. These combined atmospheric and oceanic adjustments led to EASM intensification. Our findings offer a new and more global perspective on the controls behind long-term Asian monsoon evolution.

  8. Black Carbon Concentrations from ~1850-1980 from a High-Resolution Ice Core from Geladandong, Central Tibetan Plateau

    Science.gov (United States)

    Jenkins, M.; Kaspari, S.; Kang, S.; Grigholm, B. O.; Mayewski, P. A.

    2011-12-01

    Black carbon (BC), produced by the incomplete combustion of fossil and bio-fuels, is estimated to be the second largest contributor to global warming behind CO2; when deposited on snow and ice BC reduces albedos, potentially enhancing surface melt and glacial retreat. The study of BC's past and present variability is imperative in order to better understand and estimate its potential impact on climate and water resources. This is especially important in the Himalaya/Tibetan Plateau, a region that provides fresh water to over a billion people and where BC's climatic effects are estimated to be the largest (Flanner et al., 2007; Ramanathan and Carmichael, 2008). To more accurately constrain BC's past variability in this sensitive region, an ice core recovered in 2005 from Mt. Geladandong (5800 m a.s.l.) on the central Tibetan Plateau was analyzed for BC at high resolution using a Single Particle Soot Photometer (SP2). Results indicate that 1) average BC concentrations at this location are higher than at other locations closer to BC sources and analyzed by the same method (Mt. Everest by Kaspari et al., 2011 and Muztagh Ata by Wang et al., in prep), and 2) BC exists in peak concentrations high enough (>10 μg/L) to cause a >1% reduction in surface albedo at the sampling location (Ming et al., 2009; Hadley et al., 2010). Potential causes of the higher BC concentrations at the Geladandong site include lower annual precipitation and the mechanical trapping and concentration of BC caused by surface melt and/or sublimation (Conway et al., 1996; Huang et al., 2011). Preliminary dating (Grigholm et al., in prep) has dated the top of the core to ~1980, suggesting that annual mass loss at the site has removed the upper portion of the record. This supports the findings of Kehrwald et al. (2008) who reported that glaciers below ~6050 m a.s.l. in the Himalaya/Tibetan Plateau are losing mass annually. Presented here is the record of BC on the central Tibetan Plateau over the time

  9. Antarctic Genomics

    Directory of Open Access Journals (Sweden)

    Alex D. Rogers

    2006-03-01

    Full Text Available With the development of genomic science and its battery of technologies, polar biology stands on the threshold of a revolution, one that will enable the investigation of important questions of unprecedented scope and with extraordinary depth and precision. The exotic organisms of polar ecosystems are ideal candidates for genomic analysis. Through such analyses, it will be possible to learn not only the novel features that enable polar organisms to survive, and indeed thrive, in their extreme environments, but also fundamental biological principles that are common to most, if not all, organisms. This article aims to review recent developments in Antarctic genomics and to demonstrate the global context of such studies.

  10. Evaluation on newly developed high resolution of surface solar radiation from MTSAT observations for the Tibetan Plateau

    Science.gov (United States)

    Niu, X.; Yang, K.; Tang, W.; Qin, J.

    2015-12-01

    Neither surface measurement nor existing remote sensing products of the Surface Solar Radiation (SSR) can meet the application requirements of hydrological and land process modeling in the Tibetan Plateau (TP). High resolution (hourly; 0.1⁰) of SSR estimates have been derived recently from the geostationary satellite observations - the Multi-functional Transport Satellite (MTSAT). This SSR estimation is based on updating an existing physical model, the UMD-SRB (University of Maryland Surface Radiation Budget) which is the basis of the well-known GEWEX-SRB model. In the updated framework introduced is the high-resolution Global Land Surface Broadband Albedo Product (GLASS) with spatial continuity. The developed SSR estimates are demonstrated at different temporal resolutions over the TP and are evaluated against ground observations and other satellite products from: (1) China Meteorological Administration (CMA) radiation stations in TP; (2) three TP radiation stations contributed from the Institute of Tibetan Plateau Research; (3) and the universal used satellite products (i.e. ISCCP-FD, GEWEX-SRB) in relatively low spatial resolution (0.5º-2.5º) and temporal resolution (3-hourly, daily, or monthly).

  11. CENTRAL PLATEAU REMEDIATION

    Energy Technology Data Exchange (ETDEWEB)

    ROMINE, L.D.

    2006-02-01

    A systematic approach to closure planning is being implemented at the Hanford Site's Central Plateau to help achieve the goal of closure by the year 2035. The overall objective of Central Plateau remediation is to protect human health and the environment from the significant quantity of contaminated material that resulted from decades of plutonium production in support of the nation's defense. This goal will be achieved either by removing contaminants or placing the residual contaminated materials in a secure configuration that minimizes further migration to the groundwater and reduces the potential for inadvertent intrusion into contaminated sites. The approach to Central Plateau cleanup used three key concepts--closure zones, closure elements, and closure process steps--to create an organized picture of actions required to complete remediation. These actions were merged with logic ties, constraints, and required resources to produce an integrated time-phased schedule and cost profile for Central Plateau closure. Programmatic risks associated with implementation of Central Plateau closure were identified and analyzed. Actions to mitigate the most significant risks are underway while high priority remediation projects continue to make progress.

  12. Decapitation of high-altitude glaciers on the Tibetan Plateau revealed by ice core tritium and mercury records

    Directory of Open Access Journals (Sweden)

    S. C. Kang

    2015-01-01

    Full Text Available Two ice cores were retrieved from high elevations (~ 5800 m a.s.l. at Mt. Nyainqentanglha and Mt. Geladaindong in the southern to inland Tibetan Plateau. The combined analysis of tritium (3H, 210Pb, mercury tracers, along with other chemical records, revealed that the two coring sites had not received net ice accumulation since at least the 1950s and 1980s, respectively, implying an annual ice loss rate of more than several hundred millimeter water equivalent over these periods. Both mass balance modeling at the sites and in situ data from nearby glaciers confirmed a continuously negative mass balance (or mass loss in the region due to the dramatic warming in the last decades. Along with a recent report on Naimona'nyi Glacier in the Himalaya, the findings suggest that glacier decapitation (i.e., the loss of the accumulation zone is a wide-spread phenomenon from the southern to inland Tibetan Plateau even at the summit regions. This raises concerns over the rapid rate of glacier ice loss and associated changes in surface glacier runoff, water availability, and sea levels.

  13. Viruses in Antarctic lakes

    Science.gov (United States)

    Kepner, R. L. Jr; Wharton, R. A. Jr; Suttle, C. A.; Wharton RA, J. r. (Principal Investigator)

    1998-01-01

    Water samples collected from four perennially ice-covered Antarctic lakes during the austral summer of 1996-1997 contained high densities of extracellular viruses. Many of these viruses were found to be morphologically similar to double-stranded DNA viruses that are known to infect algae and protozoa. These constitute the first observations of viruses in perennially ice-covered polar lakes. The abundance of planktonic viruses and data suggesting substantial production potential (relative to bacteria] secondary and photosynthetic primary production) indicate that viral lysis may be a major factor in the regulation of microbial populations in these extreme environments. Furthermore, we suggest that Antarctic lakes may be a reservoir of previously undescribed viruses that possess novel biological and biochemical characteristics.

  14. The prevalence and severity of dental fluorosis in the high and low altitude parts of Central Plateau, Nigeria.

    Science.gov (United States)

    Akosu, T J; Zoakah, A I; Chirdan, O A

    2009-09-01

    To compare the prevalence and severity of dental fluorosis in the high and low altitude parts of the Central Senatorial District of Plateau State. The study was cross-sectional and descriptive. The community based study was carried out in Central Plateau Nigeria, in 2005. The study subjects were 12-15 year old life long residents selected using the multistage sampling technique. One Local Government Area each was randomly selected from the high and low altitude parts of the district and from each selected Local Government Area two health districts were randomly selected with probability proportional to size. From each of the selected health Districts two major settlements were selected again with probability proportional to size. 12-15 year old life long residents of the selected settlements were studied. Each respondent completed an interviewer administered questionnaire after which he/she was clinically examined to ascertain his/her fluorosis status. Samples of water were collected from water sources consumed by the respondents in each settlement. The main outcome measures were presence and severity of dental fluorosis as measured by the Thylstrup and Fejerskov index. (TF score). One thousand one hundred children were studied, 554 (50.4%) from the high altitude part of the district and 546 (49.6%) from the low altitude part. Fluorosis prevalence was 12.9% in the district, but significantly higher (22.2%) in the high altitude areas compared to the low altitude ones (3.5%). The severest form of fluorosis in the district was TF 6 for tooth 14 and TF 5 for tooth 11. The prevalence and severity of dental fluorosis is significantly higher in the high altitude parts of the District compared to the low altitude ones. Efforts are needed to further investigate and control the problem.

  15. Multi-year record of atmospheric mercury at Dumont d'Urville, East Antarctic coast: continental outflow and oceanic influences

    Science.gov (United States)

    Angot, Hélène; Dion, Iris; Vogel, Nicolas; Legrand, Michel; Magand, Olivier; Dommergue, Aurélien

    2016-07-01

    Under the framework of the Global Mercury Observation System (GMOS) project, a 3.5-year record of atmospheric gaseous elemental mercury (Hg(0)) has been gathered at Dumont d'Urville (DDU, 66°40' S, 140°01' E, 43 m above sea level) on the East Antarctic coast. Additionally, surface snow samples were collected in February 2009 during a traverse between Concordia Station located on the East Antarctic plateau and DDU. The record of atmospheric Hg(0) at DDU reveals particularities that are not seen at other coastal sites: a gradual decrease of concentrations over the course of winter, and a daily maximum concentration around midday in summer. Additionally, total mercury concentrations in surface snow samples were particularly elevated near DDU (up to 194.4 ng L-1) as compared to measurements at other coastal Antarctic sites. These differences can be explained by the more frequent arrival of inland air masses at DDU than at other coastal sites. This confirms the influence of processes observed on the Antarctic plateau on the cycle of atmospheric mercury at a continental scale, especially in areas subject to recurrent katabatic winds. DDU is also influenced by oceanic air masses and our data suggest that the ocean plays a dual role on Hg(0) concentrations. The open ocean may represent a source of atmospheric Hg(0) in summer whereas the sea-ice surface may provide reactive halogens in spring that can oxidize Hg(0). This paper also discusses implications for coastal Antarctic ecosystems and for the cycle of atmospheric mercury in high southern latitudes.

  16. Carbonaceous matter deposition in the high glacial regions of the Tibetan Plateau

    Science.gov (United States)

    Li, Chaoliu; Chen, Pengfei; Kang, Shichang; Yan, Fangping; Li, Xiaofei; Qu, Bin; Sillanpää, Mika

    2016-09-01

    Carbonaceous matter at glacial region plays important role in river ecosystems fed by glacier and albedo reduction of glacier surface. However, currently, limited knowledge are available on the carbonaceous matter within the glacial region of the Tibetan Plateau (TP). In this study, the data from six snowpits in the glacial region across the TP were reported. The results showed that dissolved organic carbon (DOC) concentrations of snowpit samples of the TP were comparable to those of European Alps and the Arctic. The ratio of DOC to carbonaceous matter (40.25 ± 8.98%) was lower than that of Alpine glaciers, thus indicating greater particulate carbon content in the TP glacial region. In addition, the DOC was significantly correlated with insoluble particulate carbon (IPC), indicating that IPC and DOC likely came from the same sources. Spatially, the DOC concentration decreased from the north (0.42 ± 0.29 mg-C L-1) to the south TP (0.15 ± 0.06 mg-C L-1), which was consistent with variations in the distribution of dust storm on the TP. Principal component analysis of major ions and DOC showed that mineral dust contributed the major part of DOC, followed by biogenic sources such as agriculture and livestock. Finally, based on DOC concentrations and precipitation amounts at different periods, the mean annul flux of DOC in the glacial region of the TP was calculated to be 0.11 ± 0.05 g-C m-2 yr-1.

  17. Local scaling characteristics of Antarctic surface layer turbulence

    Directory of Open Access Journals (Sweden)

    S. Basu

    2010-03-01

    Full Text Available Over the past years, several studies have validated Nieuwstadt's local scaling hypothesis by utilizing turbulence observations from the mid-latitude, nocturnal stable boundary layers. In this work, we probe into the local scaling characteristics of polar, long-lived stable boundary layers by analyzing turbulence data from the South Pole region of the Antarctic Plateau.

  18. Extraction of Terraces on the Loess Plateau from High-Resolution DEMs and Imagery Utilizing Object-Based Image Analysis

    Directory of Open Access Journals (Sweden)

    Hanqing Zhao

    2017-05-01

    Full Text Available Abstract: Terraces are typical artificial landforms on the Loess Plateau, with ecological functions in water and soil conservation, agricultural production, and biodiversity. Recording the spatial distribution of terraces is the basis of monitoring their extent and understanding their ecological effects. The current terrace extraction method mainly relies on high-resolution imagery, but its accuracy is limited due to vegetation coverage distorting the features of terraces in imagery. High-resolution topographic data reflecting the morphology of true terrace surfaces are needed. Terraces extraction on the Loess Plateau is challenging because of the complex terrain and diverse vegetation after the implementation of “vegetation recovery”. This study presents an automatic method of extracting terraces based on 1 m resolution digital elevation models (DEMs and 0.3 m resolution Worldview-3 imagery as auxiliary information used for object-based image analysis (OBIA. A multi-resolution segmentation method was used where slope, positive and negative terrain index (PN, accumulative curvature slope (AC, and slope of slope (SOS were determined as input layers for image segmentation by correlation analysis and Sheffield entropy method. The main classification features based on DEMs were chosen from the terrain features derived from terrain factors and texture features by gray-level co-occurrence matrix (GLCM analysis; subsequently, these features were determined by the importance analysis on classification and regression tree (CART analysis. Extraction rules based on DEMs were generated from the classification features with a total classification accuracy of 89.96%. The red band and near-infrared band of images were used to exclude construction land, which is easily confused with small-size terraces. As a result, the total classification accuracy was increased to 94%. The proposed method ensures comprehensive consideration of terrain, texture, shape, and

  19. Co-evolution of cyanophage and cyanobacteria in Antarctic lakes: adaptive responses to high UV flux and global warming

    Science.gov (United States)

    Storrie-Lombardi, Michael C.; Pinkart, Holly C.

    2007-09-01

    Rapid adaptation to acute environmental change demands co-evolution of indigenous viral populations and their hosts. Horizontal gene transfer (HGT) is a highly efficient adaptive mechanism, but a difficult phenomena to dectect. The mosaic nature of bacteriophage genomes resulting from HGT has generally been explored using phylogenetic analysis of coding regions. Focusing on the proteome certainly provides one window into the origin and evolution of genome information storage. However, the original fitness function for a nucleotide polymer would arise from a more primal survival imperative predating the appearance of a coding function. Multivariate analysis of a genome information storage metric (lossless compression), nucleotide distributions, and distributions of the three major physiochemical characteristics of the polymer (triple:double bonding [G+C], purine:pyrimidine [G+A], and keto:amine [G+T] fractions) produces a metric to detect and characterize mosaicism in both coding and non-coding regions of a genome. We discuss possibilities and limitations of using these techniques to investigate HGT and the origins and evolution of genome complexity. Analysis of available virus (n= 2374) and bacteriophage genomes (n=417) indicates these probes can perform whole-genome taxonomy tasks or sliding window searches for evidence of HGT in a single genome. HGT responses may serve as a canary or bell-weather for global environmental change. We discuss one area of application of considerable interest to our institute: the response of cyanophage and their cyanobacteria hosts to variations in ultraviolet solar flux in geographically isolated Antarctic lakes.

  20. SUMMER DIURNAL CYCLE AT DOME C ON THE ANTARTIC PLATEAU

    OpenAIRE

    Barral, H.; E. Vignon; Bazile, E.; Traullé, O; Gallée, H.; Genthon, C.; Brun, C.; F. Couvreux; P. Le Moigne

    2014-01-01

    International audience; The ice-sheet offers us ”laboratory cases” with endless snow covered, relatively homogeneous, flat or sloped areas with persistent and strong stable stratifications resulting in low level jets. Dome C (75°06 S,123°E) on the East Antarctic Plateau is one of them.

  1. Constructions of new plateaued functions from known ones

    Institute of Scientific and Technical Information of China (English)

    Zhang Weiguo; Ding Yong; Zhang Ning; Xiao Guozhen

    2008-01-01

    A number of methods for constructing new plateaued functions from known ones are presented. By properly combining the known plateaued functions it is possible to get highly nonlinear resilient plateaued functions. The order, resiliency and propagation characteristics of the constructed plateaued functions are discussed. We show the new functions could possess the desirable cryptographic property.

  2. Changes in Moisture Flux Over the Tibetan Plateau During 1979-2011: Insights from a High Resolution Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Yanhong; Leung, Lai-Yung R.; Zhang, Yongxin; Cuo, Lan

    2015-05-01

    Net precipitation (precipitation minus evapotranspiration, P-E) changes from a high resolution regional climate simulation and its reanalysis forcing are analyzed over the Tibet Plateau (TP) and compared to the global land data assimilation system (GLDAS) product. The mechanism behind the P-E changes is explored by decomposing the column integrated moisture flux convergence into thermodynamic, dynamic, and transient eddy components. High-resolution climate simulation improves the spatial pattern of P-E changes over the best available global reanalysis. Improvement in simulating precipitation changes at high elevations contributes dominantly to the improved P-E changes. High-resolution climate simulation also facilitates new and substantial findings regarding the role of thermodynamics and transient eddies in P-E changes reflected in observed changes in major river basins fed by runoff from the TP. The analysis revealed the contrasting convergence/divergence changes between the northwestern and southeastern TP and feedback through latent heat release as an important mechanism leading to the mean P-E changes in the TP.

  3. Changes in Moisture Flux over the Tibetan Plateau during 1979-2011: Insights from a High Resolution Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Yanhong; Leung, Lai-Yung R.; Zhang, Yongxin; Cuo, Lan

    2015-05-15

    Net precipitation (precipitation minus evapotranspiration, P-E) changes between 1979 and 2011 from a high resolution regional climate simulation and its reanalysis forcing are analyzed over the Tibet Plateau (TP) and compared to the global land data assimilation system (GLDAS) product. The high resolution simulation better resolves precipitation changes than its coarse resolution forcing, which contributes dominantly to the improved P-E change in the regional simulation compared to the global reanalysis. Hence, the former may provide better insights about the drivers of P-E changes. The mechanism behind the P-E changes is explored by decomposing the column integrated moisture flux convergence into thermodynamic, dynamic, and transient eddy components. High-resolution climate simulation improves the spatial pattern of P-E changes over the best available global reanalysis. High-resolution climate simulation also facilitates new and substantial findings regarding the role of thermodynamics and transient eddies in P-E changes reflected in observed changes in major river basins fed by runoff from the TP. The analysis revealed the contrasting convergence/divergence changes between the northwestern and southeastern TP and feedback through latent heat release as an important mechanism leading to the mean P-E changes in the TP.

  4. The determination of cadmium, lead and vanadium by high resolution ICP-MS in Antarctic snow samples

    Energy Technology Data Exchange (ETDEWEB)

    Lanza, F. [Joh. Gutenberg Univ., Mainz (Germany). Inst. fuer Anorganische und Analytische Chemie; Trincherini, P. [European Union Joint Research Centre, Ispra, VA (Italy). Inst. of Environment

    2000-02-01

    Double focusing ICP-MS was successfully used in this research for the direct determination of the cadmium, lead and vanadium content of a set of Antarctic samples collected during the 11. Italian Expedition to Antarctica. For cadmium and lead measurements the low resolution mode was chosen since it ensured the highest ion sensitivity and it allowed the highest detection limits to be attained; in the case of vanadium the high resolution mode was used to solve the isobaric interference. As far as vanadium and cadmium are concerned by GFAAS coupled with different preconcentration procedures. The vanadium, cadmium and lead content measured in a riverine water reference material (SRLS-3) was found in agreement with the certified values. [Italian] Si e' utilizzato uno spettrometro ICP-MS a doppia focalizzazione per la determinazione diretta di cadmio, piombo e vanadio in una serie di campioni di neve antartica superficiale raccolta durante l'undicesima spedizione italiana in Antartide. Per le determinazioni di cadmio e piombo si e' scelta la procedura a bassa risoluzione, che ha garantito la piu' elevata sensibilita' ed ha permesso di ottenere limiti di determinazione migliori; nel caso del vanadio si e' utilizzata la procedura ad alta risoluzione che ha permesso di risolvere problemi di interferenza isobarica. Per quanto riguarda cadmio e vanadio, i risultati delle determinazioni mediante ICP-MS sono risultati in buon accordo con quelli ottenuti mediante GFAAS accoppiata a diverse procedure di preconcentrazione. Il contenuto di cadmio, piombo e vanadio misurato con le procedure sviluppate in un campione certificato di acqua di fiume (SRLS-3) e' risultato in accordo con i valori certificati.

  5. Gene Flow Results in High Genetic Similarity Between Sibiraea (Rosaceae species in the Qinghai-Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    Peng-Cheng Fu

    2016-10-01

    Full Text Available Studying closely related species and divergent populations provides insight into the process of speciation. Previous studies showed that the Sibiraea complex's evolutionary history on the Qinghai-Tibetan Plateau (QTP was confusing and could not be distinguishable on the molecular level. In this study, the genetic structure and gene flow of S. laevigata and S. angustata on the QTP was examined across 45 populations using 8 microsatellite loci. Microsatellites revealed high genetic diversity in Sibiraea populations. Most of the variance was detected within populations (87.45% rather than between species (4.39%. We found no significant correlations between genetic and geographical distances among populations. Bayesian cluster analysis grouped all individuals in the sympatric area of Sibiraea into one cluster and other individuals of S. angustata into another. Divergence history analysis based on the approximate Bayesian computation method indicated that the populations of S. angustata at the sympatric area derived from the admixture of 2 species. The assignment test assigned all individuals to populations of their own species rather than its congeneric species. Consistently, intraspecies were detected rather than interspecies first-generation migrants. The bidirectional gene flow in long-term patterns between the 2 species was asymmetric, with more from S. angustata to S. laevigata. In conclusion, the Sibiraea complex was distinguishable on the molecular level using microsatellite loci. We found that the high genetic similarity of these 2 species resulted from huge bidirectional gene flow, especially on the sympatric area where population admixtures between the species occurred.

  6. Moisture increase in response to high-altitude warming evidenced by tree-rings on the southeastern Tibetan Plateau

    Science.gov (United States)

    Li, Jinbao; Shi, Jiangfeng; Zhang, David D.; Yang, Bao; Fang, Keyan; Yue, Pak Hong

    2017-01-01

    Rapid warming has been observed in the high-altitude areas around the globe, but the implications on moisture change are not fully understood. Here we use tree-rings to reveal common moisture change on the southeastern Tibetan Plateau (TP) during the past five centuries, and show that regional moisture change in late spring to early summer (April-June) is closely related to large-scale temperature anomaly over the TP, with increased moisture coincident with periods of high temperature. The most recent pluvial during the 1990s-2000s is likely the wettest for the past five centuries, which coincides with the warmest period on the TP during the past millennium. Dynamic analysis reveals that vertical air convection is enhanced in response to anomalous TP surface warming, leading to an increase in lower-tropospheric humidity and effective precipitation over the southeastern TP. The coherent warm-wet relationship identified in both tree-rings and dynamic analysis implies a generally wetter condition on the southeastern TP under future warming.

  7. Ocean acidification at high latitudes: potential effects on functioning of the Antarctic bivalve Laternula elliptica

    National Research Council Canada - National Science Library

    Cummings, Vonda; Hewitt, Judi; Van Rooyen, Anthony; Currie, Kim; Beard, Samuel; Thrush, Simon; Norkko, Joanna; Barr, Neill; Heath, Philip; Halliday, N Jane; Sedcole, Richard; Gomez, Antony; McGraw, Christina; Metcalf, Victoria

    2011-01-01

    Ocean acidification is a well recognised threat to marine ecosystems. High latitude regions are predicted to be particularly affected due to cold waters and naturally low carbonate saturation levels...

  8. Extent of the Antarctic Continent.

    Science.gov (United States)

    Press, F; Dewart, G

    1959-02-20

    Group velocities of eartquake-generated Love and Rayleigh waves for certain transantarctic paths are abnormally high when compared with data from other continents. For these paths, the data indicate that at most only three-fourths of the antarctic ice sheet is underlain by continent, the remaining area being oceanic in structure.

  9. Stress analysis of the tibial plateau according to the difference of blade path entry in opening wedge high tibial osteotomy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jun Woo; Xin, YuanZhu; Yang, Seok Jo [Chungnam National University, Daejeon (Korea, Republic of); Ji, Jong Hun; Panchal, Karnav; Kwon, Oh Soo [The Catholic University of Korea, Daejeon (Korea, Republic of)

    2015-03-15

    High tibial osteotomy (HTO) has been used to successfully treat patients with genu varus deformities that can improve mechanical function and condition in the knee joint. Clinical studies have reported that bow legs often occur with a concentrated load on the varus of the tibia. This study aimed to analyze and verify the clinical test data result by utilizing the three-dimensional (3D) static finite element method (FEM). The 3D model of lower extremities, which include the femur, tibia, meniscus, and knee articular cartilage, was created using the images from a computer tomography scan and magnetic resonance imaging. In this report, we compared changes in stress distribution and force reaction on the tibial plateau because of critical problems caused by unexpected changes in the tibial posterior-slope angle because of HTO. The results showed that the 5 .deg. wedge-angle virtual opening wedge HTO without and with the posterior-slope angle shows has a load concentration of approximately 60% and 45% in the medial region, respectively.

  10. Using high-resolution satellite imagery to assess populations of animals in the Antarctic

    Science.gov (United States)

    LaRue, Michelle Ann

    The Southern Ocean is one of the most rapidly-changing ecosystems on the planet due to the effects of climate change and commercial fishing for ecologically-important krill and fish. It is imperative that populations of indicator species, such as penguins and seals, be monitored at regional- to global scales to decouple the effects of climate and anthropogenic changes for appropriate ecosystem-based management of the Southern Ocean. Remotely monitoring populations through high-resolution satellite imagery is currently the only feasible way to gain information about population trends of penguins and seals in Antarctica. In my first chapter, I review the literature where high-resolution satellite imagery has been used to assess populations of animals in polar regions. Building on this literature, my second chapter focuses on estimating changes in abundance in the Weddell seal population in Erebus Bay. I found a strong correlation between ground and satellite counts, and this finding provides an alternate method for assessing populations of Weddell seals in areas where less is known about population status. My third chapter explores how size of the guano stain of Adelie penguins can be used to predict population size. Using high-resolution imagery and ground counts, I built a model to estimate the breeding population of Adelie penguins using a supervised classification to estimate guano size. These results suggest that the size of guano stain is an accurate predictor of population size, and can be applied to estimate remote Adelie penguin colonies. In my fourth chapter, I use air photos, satellite imagery, climate and mark-resight data to determine that climate change has positively impacted the population of Adelie penguins at Beaufort Island through a habitat release that ultimately affected the dynamics within the southern Ross Sea metapopulation. Finally, for my fifth chapter I combined the literature with observations from aerial surveys and satellite imagery to

  11. Higher and colder: The success and failure of boundaries in high altitude and Antarctic research stations.

    Science.gov (United States)

    Heggie, Vanessa

    2016-12-01

    This article offers a series of case studies of field stations and field laboratories based at high altitudes in the Alps, Himalayas and Antarctica, which have been used by Western scientists (largely physiologists and physicists) from circa 1820 to present. It rejects the common frame for work on such spaces that polarizes a set of generalizations about practices undertaken in 'the field' versus 'the laboratory'. Field sites are revealed as places that can be used to highlight common and crucial features of modern experimental science that are exposed by, but not uniquely the properties of, fieldwork. This includes heterogeneity of population and practice, diverse afterlives, the manner in which spaces of science construct individual and group expertise, and the extensive support and funding structures needed for modern scientific work.

  12. High-resolution multispectral satellite imagery for extracting bathymetric information of Antarctic shallow lakes

    Science.gov (United States)

    Jawak, Shridhar D.; Luis, Alvarinho J.

    2016-05-01

    High-resolution pansharpened images from WorldView-2 were used for bathymetric mapping around Larsemann Hills and Schirmacher oasis, east Antarctica. We digitized the lake features in which all the lakes from both the study areas were manually extracted. In order to extract the bathymetry values from multispectral imagery we used two different models: (a) Stumpf model and (b) Lyzenga model. Multiband image combinations were used to improve the results of bathymetric information extraction. The derived depths were validated against the in-situ measurements and root mean square error (RMSE) was computed. We also quantified the error between in-situ and satellite-estimated lake depth values. Our results indicated a high correlation (R = 0.60 0.80) between estimated depth and in-situ depth measurements, with RMSE ranging from 0.10 to 1.30 m. This study suggests that the coastal blue band in the WV-2 imagery could retrieve accurate bathymetry information compared to other bands. To test the effect of size and dimension of lake on bathymetry retrieval, we distributed all the lakes on the basis of size and depth (reference data), as some of the lakes were open, some were semi frozen and others were completely frozen. Several tests were performed on open lakes on the basis of size and depth. Based on depth, very shallow lakes provided better correlation (≈ 0.89) compared to shallow (≈ 0.67) and deep lakes (≈ 0.48). Based on size, large lakes yielded better correlation in comparison to medium and small lakes.

  13. Ocean acidification at high latitudes: potential effects on functioning of the Antarctic bivalve Laternula elliptica.

    Directory of Open Access Journals (Sweden)

    Vonda Cummings

    Full Text Available Ocean acidification is a well recognised threat to marine ecosystems. High latitude regions are predicted to be particularly affected due to cold waters and naturally low carbonate saturation levels. This is of concern for organisms utilising calcium carbonate (CaCO(3 to generate shells or skeletons. Studies of potential effects of future levels of pCO(2 on high latitude calcifiers are at present limited, and there is little understanding of their potential to acclimate to these changes. We describe a laboratory experiment to compare physiological and metabolic responses of a key benthic bivalve, Laternula elliptica, at pCO(2 levels of their natural environment (430 µatm, pH 7.99; based on field measurements with those predicted for 2100 (735 µatm, pH 7.78 and glacial levels (187 µatm, pH 8.32. Adult L. elliptica basal metabolism (oxygen consumption rates and heat shock protein HSP70 gene expression levels increased in response both to lowering and elevation of pH. Expression of chitin synthase (CHS, a key enzyme involved in synthesis of bivalve shells, was significantly up-regulated in individuals at pH 7.78, indicating L. elliptica were working harder to calcify in seawater undersaturated in aragonite (Ω(Ar = 0.71, the CaCO(3 polymorph of which their shells are comprised. The different response variables were influenced by pH in differing ways, highlighting the importance of assessing a variety of factors to determine the likely impact of pH change. In combination, the results indicate a negative effect of ocean acidification on whole-organism functioning of L. elliptica over relatively short terms (weeks-months that may be energetically difficult to maintain over longer time periods. Importantly, however, the observed changes in L. elliptica CHS gene expression provides evidence for biological control over the shell formation process, which may enable some degree of adaptation or acclimation to future ocean acidification scenarios.

  14. Posterior bicondylar tibial plateau fractures.

    Science.gov (United States)

    Carlson, DuWayne A

    2005-02-01

    To present a case series of patients with posterior bicondylar tibial plateau fractures treated by direct fracture exposure and fixation through dual incisions. Retrospective clinical study. Level 1 trauma centers. Eight patients were identified that had posterior bicondylar tibial plateau fractures. Two patients had depressed posterolateral tibial plateau fractures with contained defects and did not have direct fracture exposure. One patient died of medical problems leaving 5 patients who underwent direct fracture exposure, reduction, and fixation. Posteromedial followed by posterolateral open reduction and internal fixation of posterior bicondylar tibial plateau fractures. At 6 to 24 months follow-up (mean 13 months), all patients returned to near full activities, each with aching after prolonged standing (8-hour shift). Range of motion averaged 2 degrees to 121 degrees of flexion. Three of 5 returned to manual labor jobs; the others were not employed at the time of injury. Posterior bicondylar tibial plateau fractures have a high association with lateral meniscal pathology and can be associated with anterior cruciate ligament injury. Reduction of the posterior plateau condyles is easiest with the knee in full extension. Flexion contractures can be a problem, and patients should be encouraged to regain/maintain knee extension. The dual-incision approach to these challenging fractures can result in good to excellent knee function for these patients.

  15. Running PILOT: operational challenges and plans for an Antarctic Observatory

    Science.gov (United States)

    McGrath, Andrew; Saunders, Will; Gillingham, Peter; Ward, David; Storey, John; Lawrence, Jon; Haynes, Roger

    2008-07-01

    We highlight the operational challenges and planned solutions faced by an optical observatory taking advantage of the superior astronomical observing potential of the Antarctic plateau. Unique operational aspects of an Antarctic optical observatory arise from its remoteness, the polar environment and the unusual observing cycle afforded by long continuous periods of darkness and daylight. PILOT is planned to be run with remote observing via satellite communications, and must overcome both limited physical access and data transfer. Commissioning and lifetime operations must deal with extended logistics chains, continual wintertime darkness, extremely low temperatures and frost accumulation amidst other challenging issues considered in the PILOT operational plan, and discussed in this presentation.

  16. High resolution bathymetric and sonar images of a ridge southeast of Terceira Island (Azores plateau)

    Science.gov (United States)

    Lourenço, N.; Miranda, J. M.; Luis, J.; Silva, I.; Goslin, J.; Ligi, M.

    2003-04-01

    The Terceira rift is a oblique ultra-slow spreading system where a transtensive regime results from differential movement between Eurasian and African plates. So far no classical ridge segmentation pattern has here been observed. The predominant morphological features are fault controlled rhombic shaped basins and volcanism related morphologies like circular seamounts and volcanic ridges. We present SIMRAD EM300 (bathymetry + backscatter) images acquired over one of these ridges located SE of Terceira Island, during the SIRENA cruise (PI J. Goslin), which complements previous TOBI mosaics performed over the same area during the AZZORRE99 cruise (PI M. Ligi). The ridge presents a NW-SE orientation, it is seismically active (a seismic crisis was documented in 1997) and corresponds to the southern branch of a V shape bathymetric feature enclosing the Terceira Island and which tip is located west of the Island near the 1998 Serreta ridge eruption site. NE of the ridge, the core of the V, corresponds to the North Hirondelle basin. All this area corresponds mainly to Brunhes magnetic epoch. The new bathymetry maps reveal a partition between tectonic processes, centred in the ridge, and volcanism present at the bottom of the North Hirondelle basin. The ridge high backscatter surface is cut by a set of sub-parallel anastomosed normal faults striking between N130º and N150º. Some faults present horse-tail terminations. Fault splays sometimes link to neighbour faults defining extensional duplexes and fault wedge basins and highs of rhombic shape. The faulting geometry suggests that a left-lateral strike slip component should be present. The top of the ridge consists on an arched demi-.horst, and it is probably a volcanic structure remnant (caldera system?), existing prior to onset of the tectonic stage in the ridge. Both ridge flanks display gullies and mass wasting fans at the base of the slope. The ridge vicinities are almost exclusively composed of a grayish homogeneous

  17. The Antarctic Geospatial Information Center: Three Years of Supporting Antarctic Science and Operations

    Science.gov (United States)

    Herried, B.; Morin, P. J.; Larue, M.; Porter, C.; Niebuhr, S.; Antarctic Geospatial Information Center

    2010-12-01

    Founded in 2007, the Antarctic Geospatial Information Center (AGIC) is dedicated to supporting and promoting the United States Antarctic Program (USAP) by providing geospatial information to Antarctic science, operations, and education communities. Since its inception, AGIC contributes to Antarctic science in four significant ways: 1) by direct geospatial support of research groups to advance science, 2) by authoring maps and creating applications to facilitate better logistical support, 3) by serving as a data repository and clearinghouse for Antarctic geospatial data, 4) by providing expertise, analysis, and education to researchers, support staff, and students. This poster will showcase several products, tools, and services developed by AGIC in the past three years, including a collection of 150 ground control points in the McMurdo Dry Valleys and Ross Island, highly accurate maps in the McMurdo Sound region using satellite imagery, and an archive of historical USGS aerial photography accessed through a web-based search application.

  18. Biomagnification of persistent organic pollutants along a high-altitude aquatic food chain in the Tibetan Plateau: Processes and mechanisms.

    Science.gov (United States)

    Ren, Jiao; Wang, Xiaoping; Wang, Chuanfei; Gong, Ping; Wang, Xiruo; Yao, Tandong

    2017-01-01

    Biomagnification of some persistent organic pollutants (POPs) has been found in marine and freshwater food chains; however, due to the relatively short food chains in high-altitude alpine lakes, whether trophic transfer would result in the biomagnification of POPs is not clear. The transfer of various POPs, including organochlorine pesticides and polychlorinated biphenyls (PCBs), along the aquatic food chain in Nam Co Lake (4700 m), in the central Tibetan Plateau, was studied. The POPs levels in the water, sediment and biota [plankton, invertebrates and fish (Gymnocypris namensis)] of Nam Co were generally low, with concentrations comparable to those reported for the remote Arctic. The composition profiles of POPs in the fish were different from that in the water, but similar to their food. DDEs, DDDs, PCB 138, 153 and 180 displayed significant positive correlations with trophic levels, with trophic magnification factors (TMFs) ranged between 1.5 and 4.2, implying these chemicals can undergo final biomagnification along food chain. A fugacity-based dynamic bioaccumulation model was applied to the fish with localized parameters, by which the simulated concentrations were comparable to the measured data. Modeling results showed that most compounds underwent net gill loss and net gut uptake; only when the net result of the combined gut and gill fluxes would be positive, bioaccumulation could eventually occur. The net accumulation flux increased with fish age, which was caused by the continuous increase of gut uptake by aged fish. Due to the oligotrophic condition, efficient food absorption is likely the key factor that influences the gut POPs uptake. Long residence times with half-lives up to two decades were found for the higher chlorinated PCBs in Gymnocypris namensis.

  19. Petrogenesis and its significance to continental dynamics of the Neogene high-potassium calc-alkaline volcanic rock association from north Qiangtang, Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    赖绍聪; 刘池阳; S.Y.O’Reilly

    2001-01-01

    Detailed studies indicate that the main rock type of the Neogene high-potassium calc-alkaline volcanic rock association from north Qiangtang is andesite, dacite and rhyolite. They belong to typical crust-generation magmatic system and originate from the special thickened crust of the Tibetan Plateau by dehydration melting. This group of rocks exhibits LREE enrichment but no remarkable Eu anomaly that shows their source region should be a thickened deep crust consisting of eclogitic mass group, implying that the crust had been thickened and an eclogitic deep crust had been formed during the Neogene period in Qiangtang area. This understanding is important and significant to making further discussion on the uplift mechanism and continental dynamics of the Tibetan Plateau.

  20. Ultra-robust high-field magnetization plateau and supersolidity in bond-frustrated MnCr2S4

    Science.gov (United States)

    Tsurkan, Vladimir; Zherlitsyn, Sergei; Prodan, Lilian; Felea, Viorel; Cong, Pham Thanh; Skourski, Yurii; Wang, Zhe; Deisenhofer, Joachim; von Nidda, Hans-Albrecht Krug; Wosnitza, Joahim; Loidl, Alois

    2017-01-01

    Frustrated magnets provide a promising avenue for realizing exotic quantum states of matter, such as spin liquids and spin ice or complex spin molecules. Under an external magnetic field, frustrated magnets can exhibit fractional magnetization plateaus related to definite spin patterns stabilized by field-induced lattice distortions. Magnetization and ultrasound experiments in MnCr2S4 up to 60 T reveal two fascinating features: (i) an extremely robust magnetization plateau with an unusual spin structure and (ii) two intermediate phases, indicating possible realizations of supersolid phases. The magnetization plateau characterizes fully polarized chromium moments, without any contributions from manganese spins. At 40 T, the middle of the plateau, a regime evolves, where sound waves propagate almost without dissipation. The external magnetic field exactly compensates the Cr–Mn exchange field and decouples Mn and Cr sublattices. In analogy to predictions of quantum lattice-gas models, the changes of the spin order of the manganese ions at the phase boundaries of the magnetization plateau are interpreted as transitions to supersolid phases. PMID:28345038

  1. Controls and variability of solute and sedimentary fluxes in Antarctic and sub-Antarctic Environments

    Science.gov (United States)

    Zwolinski, Zbigniew

    2015-04-01

    . Solute and sediment transport in the streams of analyzed environments are constrained by the relatively short water runoff season that typically lasts from a few weeks to maximum of four months during the austral summer, for Antarctic and sub-Antarctic regions respectively. Because of high intensity of mechanical and chemical weathering processes solute and sediment transport are rather high within Antarctic environments. Weathering rates on slopes and magnitude of fluvial transport in relatively short streams control the intensity of denudational processes. Both mechanical and chemical denudation varies highly through sub-Antarctic and Antarctic environments. To generate accurate predictions of fluvial and denudational processes we must fully understand the actual geoecological processes, which in some places are under rapid change, e.g., the Antarctic Peninsula and sub-Antarctic islands.

  2. High geo-stress distribution and high geo-stress concentration area models for eastern margin of Qinghai-Tibet plateau

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    High geo-stress and its engineering problems have severely affected the development of civil infrastructures in western China. The problems include high rock slope instabilities,rock burst,gas explosion and large-scale soft rock deformation in deep tunnels.This paper investigates the distribution of the high geo-stresses and the models of the stress concentration areas in the eastern margin of Qinghai-Tibet plateau so that a solid foundation can be formed to address the problems.The investigation is based on a comprehensive analysis of the previous research data of the eastern margin and uses remote sensing techniques,geophysics,geochemistry,and large scale geological surveying methods.The investigation has found that some special tectonic zones have high geo-stresses.The high geo-stresses are located at(1) the convergent boundary areas between two fault blocks with large strength differences,(2) the tectonic necks in front of active fault blocks,and(3) the intersection and/or termination areas of faults within the fault blocks.An example for(1) is the north Qilian high geo-stress area.Another example for(2) is the Minshan high geo-stress area in the northwest Sichuan.Furthermore,the investigation has summarized six basic models to characterize the high geo-stress concentration areas.The first one is the convergent stress concentration model at the boundary of two fault blocks.The other five stress concentration modes are oblique fissures or intersecting areas,areas without lower velocity layer in the crust,areas of compression induced tensile cracking,tectonic wedge areas,and tectonic neck areas,respectively.

  3. The high tide of the warm Pliocene: Implications of ~20 m Peak Eustatic Sea-Levels for Antarctic Deglaciation

    Science.gov (United States)

    Miller, K. G.; Browning, J. V.; Kulpecz, A. A.; Kominz, M. A.; Naish, T.; Rosenthal, Y.; Peltier, W. R.; Sosdian, S. M.; Wright, J. D.

    2010-12-01

    The eustatic peak of the Pliocene (ca. 3 Ma) allows evaluation of sea-level response to conditions warmer than present and with atmospheric carbon dioxide levels similar to the early 21st century. We provide new eustatic estimates for the Pliocene from backstripping shallow-marine, siliciclastic sections in Virginia, U.S.A., and New Zealand, accounting for the effects of compaction, Airy loading, and thermal subsidence. We compare our backstripped eustatic estimates with previously published estimates from a carbonate atoll (Enewetak), deep sea benthic foraminiferal oxygen isotopes, Mg-Ca, and uplifted marine terraces in the Carolinas and Alaska and conclude that the peak was 19±5 m, significantly lower than previously published estimates of 30-40 m derived from uplifted terraces. The 19-m peak implies not only the loss of the total equivalent of Greenland and West Antarctic ice sheets, but suggests volume loss of the East Antarctic Ice Sheet (EAIS) of ~4 m of sea-level equivalent. Our estimates provide helps resolve the long-standing controversy of the stability of the EAIS during the warmer-than-present Pliocene climatic optimum. The sea-level fall at MIC 100 (ca. 2.7 Ma) associated with the growth of large northern hemisphere ice sheets was remarkably large (~100 m) and may have cause a glacial isotostatic adjustment the resulted in uplift of the otherwise tectonically stable New Jersey coastal plain. Despite uncertainties in pre-ice core CO2 and global temperature measurements, the Pliocene provides a critical sea level-atmospheric CO2 calibration point for climates significantly warmer than the last major interglacial, MIC 5e.

  4. The Antarctic Impulsive Transient Antenna ultra-high energy neutrino detector: Design, performance, and sensitivity for 2006-2007 balloon flight

    Energy Technology Data Exchange (ETDEWEB)

    Gorham, P. W. [Univ. of Hawaii, Manoa, HI (United States); Allison, P. [Univ. of Hawaii, Manoa, HI (United States); Barwick, S. W. [Univ. of California, Irvine, CA (United States); Beatty, J. J. [The Ohio State Univ., Columbus, OH (United States); Besson, D. Z. [Univ. of Kansas, Lawrence, KS (United States); Binns, W. R. [Washington Univ., St. Louis, MO (United States); Chen, C. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Chen, P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); NASA Goddard Space Flight Center, Greenbelt, MD (United States); Clem, J. M. [Univ. of Delaware, Newark, DE (United States); Connolly, A. [Univ. College London, London (United Kingdom); Dowkontt, P. F. [Washington Univ., St. Louis, MO (United States); DuVernois, M. A. [Univ. of Minnesota, Minneapolis, MN (United States); Field, R. C. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Goldstein, D. [Univ. of California, Irvine, CA (United States); Goodhue, A. [Univ. of California, Los Angeles, CA (United States); Hast, C. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hebert, C. L. [Univ. of Hawaii, Manoa, HI (United States); Hoover, S. [Univ. of California, Los Angeles, CA (United States); Israel, M. H. [Washington Univ., St. Louis, MO (United States); Learned, J. G. [Univ. of Hawaii, Manoa, HI (United States). et al.

    2009-05-23

    In this article, we present a comprehensive report on the experimental details of the Antarctic Impulsive Transient Antenna (ANITA) long-duration balloon payload, including the design philosophy and realization, physics simulations, performance of the instrument during its first Antarctic flight completed in January of 2007, and expectations for the limiting neutrino detection sensitivity.

  5. Estimation of high-resolution near-surface freeze/thaw state by the integration of microwave and thermal infrared remote sensing data on the Tibetan Plateau

    Science.gov (United States)

    Zhao, Tianjie; Shi, Jiancheng; Hu, Tongxi; Zhao, Lin; Zou, Defu; Wang, Tianxing; Ji, Dabin; Li, Rui; Wang, Pingkai

    2017-08-01

    The objective of this study is to investigate how the complementarity between microwave and thermal infrared remote sensing can be exploited for a high-resolution near-surface freeze/thaw state estimation. The basic idea is to establish a feasible relationship between the microwave-derived freeze/thaw state and thermal infrared observations. A quantitative freeze/thaw index from microwave observations at 18.7 and 36.5 GHz is innovatively defined and is assumed to be linearly correlated with land surface temperature from thermal infrared observations. Thus, a linear regression method is proposed and verified to be effective over a multiscale network of Naqu of the Tibetan Plateau. In order to demonstrate the potentiality of the proposed method, it is implemented in the entire Tibetan Plateau. It is found that the linear relationship is quite reliable for most areas and can obtain a high-resolution near-surface soil freeze/thaw state with integrated information from microwave and thermal infrared remote sensing. The validation of the high-resolution freeze/thaw state against soil temperature measured at active layer monitoring sites along the Qinghai-Tibet Highway illustrates a moderate accuracy over a decade scale. This study provides new insights for high-resolution freeze/thaw mapping beyond the Soil Moisture Active Passive mission.

  6. Experimental growth pattern calibration of Antarctic bivalves shells to provide a biogenic archive of long-term high-resolution records of environmental and climatic change.

    Science.gov (United States)

    Lartaud, F.; Toulot, A.; Paulet, Y. M.

    2009-04-01

    Mollusc shells are used as an archive of climate variability in polar areas. The geochemistry (isotope and trace element) of the mineralized tissues is sensitive to the seawater physico-chemical changes (temperature, salinity, primary production …) and the accretionary growth of the shells provide intra-annual to centennial information. However, a serious age and growth profile calibration is necessary to establish a chronological time scale in the micro-sampling strategy. This kind of investigation on biogenic carbonates from Polar Regions suffers to the difficulties of a precise field-based standardization and validation. That's why ecology and shell growth history of many molluscs from those areas still remain unknown. In Boreal seas, bivalve metabolic activity is usually more reduced than in tropical or temperate domains, and the life span increase. For example, growth bands counting in the shells of the ocean Quahog (Arctica islandica) reveals that some of these shells are up to 250 years old (Wanamaker et al., 2008). Nevertheless in those environments, few species have highly defined growth increments calibration. The shell growth of the Antarctic scallop Adamussium colbecki is presently not well defined. Some authors attribute a growth rate close to the temperate equivalent species (Heilmayer et al., 2003) whereas others show a lower performance (Berkman et al., 2004). During the MACARBI program, to investigate the shell growth rate and determine a sclerochronologic profile, Adamussium colbecki and Laternula elliptica shells from Terre Adélie (Antarctic) were marked in situ with calcein during 6 hours and recapture a month later, in the austral summer 2007-2008. At the same time, a control of environmental conditions (temperature, salinity and chlorophyll) was carried out. All shells marked provide a distinct green fluorescent line, corresponding to the date of the marking. Calcein marking did not affect survivorship or growth of A. colbecki and L

  7. A diagnostic study of Antarctic fog

    Science.gov (United States)

    Lazzara, Matthew A.

    2008-10-01

    The United States Antarctic Program (USAP) is the largest scientific research program in the Antarctic and requires a considerable aviation operation. Although fog is one of the top three forecast problems related to flights aborted due to weather, it is largely unstudied. The objective of this project is to gain an understanding of fog that affects McMurdo Station, Antarctica and its nearby airfields. This understanding is gained through analyses of surface based weather observations, satellite measurements and numerical weather prediction models. Multi-channel satellite observations indicate that most austral summer fog events are "advective" in nature. This is supported by weather observations from McMurdo Station and nearby airfields where fog occurs at moderate wind speeds, and primarily from the eastward direction. Analyses using both a back trajectory model and mesoscale numerical model are consistent with this finding. The primary source region for fog is found to be from the southeast over the Ross Ice Shelf (72% of the cases studied), while only a minority of cases (23%) reveals a secondary source of fog from the north along the Scott Coast with airflow influences from the East Antarctic Plateau. McMurdo experiences two fog seasons with a primary peak in January and a secondary peak in September. Fog events are often short lived---typically 1 to 3 hours, though some can last up to 30 hours. Fog occurrences over the last 30 years appear to be decreasing. Time series analysis between the observed fog variability and large-scale circulations (e.g., El Nino, Antarctic Oscillation) yielded no correlations, while there is only a limited relationship of fog occurrence to ice concentration in nearby Lewis Bay and McMurdo Sound. Fog is more likely to take place at the nearby airfields rather than at McMurdo Station, which is consistent with the advective nature of the fog.

  8. Model calculations of the age of firn air across the Antarctic continent

    Directory of Open Access Journals (Sweden)

    K. A. Kaspers

    2004-01-01

    Full Text Available The age of firn air in Antarctica at pore close-off depth is only known for a few specific sites where firn air has been sampled for analyses. We present a model that calculates the age of firn air at pore close-off depth for the entire Antarctic continent. The model basically uses four meteorological parameters as input (surface temperature, pressure, accumulation rate and wind speed. Using parameterisations for surface snow density, pore close-off density and tortuosity, in combination with a density-depth model and data of a regional atmospheric climate model, distribution of pore close-off depth for the entire Antarctic continent is determined. The deepest pore close-off depth was found for the East Antarctic Plateau near 72° E, 82° S, at 150±15 m (2σ. A firn air diffusion model was applied to calculate the age of CO2 at pore close-off depth. The results predict that the oldest firn gas (CO2 age is located between Dome Fuji, Dome Argos and Vostok at 43° E, 78° S being 148±23 (1σ or 38 for 2σ years old. At this location an atmospheric trace gas record should be obtained. In this study we show that methyl chloride could be recorded with a predicted length of 125 years as an example for trace gas records at this location. The longest record currently available from firn air is derived at South Pole, being 80 years. Sensitivity tests reveal that the locations with old firn air (East Antarctic Plateau have an estimated uncertainty (2σ for the modelled CO2 age at pore close-off depth of 30% and of about 40% for locations with younger firn air (CO2 age typically 40 years. Comparing the modelled age of CO2 at pore close-off depth with directly determined ages at seven sites yielded a correlation coefficient of 0.90 and a slope close to 1, suggesting a high level of confidence for the modelled results in spite of considerable remaining uncertainties.

  9. The End of Zhang Zhung Kingdom in the Northwestern Area of the Qinghai-Tibet High Plateau and Its Continuation in the Southeastern Area

    Institute of Scientific and Technical Information of China (English)

    Tong Mei

    2015-01-01

    I. A review of the ideas regarding the end of the Zhang Zhung Kingdom in the north-western part of the Qinghai-Tibet high plateau The historical legend of the Zhang Zhung Kingdom dates back to the time of Shenrab Miwo, the founder of Bon religion. The end of the Zhang Zhung Kingdom can clearly be regarded as the pe-riod of Trisong Detsen. In a nutshell, the history of the Zhang Zhung Kingdom merged into the history of the remnants of Tubo btsan-po. Concerning its geographical area, it was re-garded that no matter how long the history of the Zhang Zhung Kingdom lasted,or how big the terri-tory of the Kingdom was, the center of the Zhang Zhung Kingdom historically was always in the Qinghai-Tibet plateau, and its influence histori-cally sometimes reached the wider area to the edge of the northwestern part of the Qinghai-Tibet plat-eau. Sometimes it extended to the upper-reaches of the Min river at the edge of the southeastern area of the Qinghai-Tibet high plateau. In the present area of Rgyalrong, the upper reaches of the Min River,and even in the area of the Sanxingdui and Jinsha sites in the Chengdu plain,we can still find historical traces of the ancient Zhang Zhuang King-dom. Concerning the end of the Zhang Zhung King-dom in the northwestern part of the Qinghai-Tibet plateau,I have written a detailed discussion in an-other article titled A Discussion on the Eighteen Kingdoms of Ancient Zhang Zhung and Their De-struction. In order to connect it with the following research,I would like to give a summarized expla-nation. As a place where the people believed in the sacred bird khyung ( Garuda ) , a record of the Zhang Zhung Kingdom in Tibetan sources dates back at least to literature found at Dunhuang. Through a review of representative concepts of the Zhang Zhuang Kingdom, there is a basic idea which regarded the geographical space of Zhang Zhuang as historically in the northwestern part of the Qinghai-Tibet high plateau. How can we now confirm the time coordinates

  10. Snow on Antarctic sea ice

    Science.gov (United States)

    Massom, Robert A.; Eicken, Hajo; Hass, Christian; Jeffries, Martin O.; Drinkwater, Mark R.; Sturm, Matthew; Worby, Anthony P.; Wu, Xingren; Lytle, Victoria I.; Ushio, Shuki; Morris, Kim; Reid, Phillip A.; Warren, Stephen G.; Allison, Ian

    2001-08-01

    Snow on Antarctic sea ice plays a complex and highly variable role in air-sea-ice interaction processes and the Earth's climate system. Using data collected mostly during the past 10 years, this paper reviews the following topics: snow thickness and snow type and their geographical and seasonal variations; snow grain size, density, and salinity; frequency of occurrence of slush; thermal conductivity, snow surface temperature, and temperature gradients within snow; and the effect of snow thickness on albedo. Major findings include large regional and seasonal differences in snow properties and thicknesses; the consequences of thicker snow and thinner ice in the Antarctic relative to the Arctic (e.g., the importance of flooding and snow-ice formation); the potential impact of increasing snowfall resulting from global climate change; lower observed values of snow thermal conductivity than those typically used in models; periodic large-scale melt in winter; and the contrast in summer melt processes between the Arctic and the Antarctic. Both climate modeling and remote sensing would benefit by taking account of the differences between the two polar regions.

  11. Phylogeography of the South China field mouse (Apodemus draco on the southeastern Tibetan Plateau reveals high genetic diversity and glacial refugia.

    Directory of Open Access Journals (Sweden)

    Zhenxin Fan

    Full Text Available The southeastern margin of the Tibetan Plateau (SEMTP is a particularly interesting region due to its topographic complexity and unique geologic history, but phylogeographic studies that focus on this region are rare. In this study, we investigated the phylogeography of the South China field mouse, Apodemus draco, in order to assess the role of geologic and climatic events on the Tibetan Plateau in shaping its genetic structure. We sequenced mitochondrial cytochrome b (cyt b sequences in 103 individuals from 47 sampling sites. In addition, 23 cyt b sequences were collected from GenBank for analyses. Phylogenetic, demographic and landscape genetic methods were conducted. Seventy-six cyt b haplotypes were found and the genetic diversity was extremely high (π = 0.0368; h = 0.989. Five major evolutionary clades, based on geographic locations, were identified. Demographic analyses implied subclade 1A and subclade 1B experienced population expansions at about 0.052-0.013 Mya and 0.014-0.004 Mya, respectively. The divergence time analysis showed that the split between clade 1 and clade 2 occurred 0.26 Mya, which fell into the extensive glacial period (EGP, 0.5-0.17 Mya. The divergence times of other main clades (2.20-0.55 Mya were congruent with the periods of the Qingzang Movement (3.6-1.7 Mya and the Kun-Huang Movement (1.2-0.6 Mya, which were known as the most intense uplift events in the Tibetan Plateau. Our study supported the hypothesis that the SEMTP was a large late Pleistocene refugium, and further inferred that the Gongga Mountain Region and Hongya County were glacial refugia for A. draco in clade 1. We hypothesize that the evolutionary history of A. draco in the SEMTP primarily occurred in two stages. First, an initial divergence would have been shaped by uplift events of the Tibetan Plateau. Then, major glaciations in the Pleistocene added complexity to its demographic history and genetic structure.

  12. Anomalously high arsenic concentration in a West Antarctic ice core and its relationship to copper mining in Chile

    Science.gov (United States)

    Schwanck, Franciele; Simões, Jefferson C.; Handley, Michael; Mayewski, Paul A.; Bernardo, Ronaldo T.; Aquino, Francisco E.

    2016-01-01

    Arsenic variability records are preserved in snow and ice cores and can be utilized to reconstruct air pollution history. The Mount Johns ice core (79°55‧S; 94°23‧W and 91.2 m depth) was collected from the West Antarctic Ice Sheet in the 2008/09 austral summer. Here, we report the As concentration variability as determined by 2137 samples from the upper 45 m of this core using ICP-SFMS (CCI, University of Maine, USA). The record covers approximately 125 years (1883-2008) showing a mean concentration of 4.32 pg g-1. The arsenic concentration in the core follows global copper mining evolution, particularly in Chile (the largest producer of Cu). From 1940 to 1990, copper-mining production increased along with arsenic concentrations in the MJ core, from 1.92 pg g-1 (before 1900) to 7.94 pg g-1 (1950). In the last two decades, environmental regulations for As emissions have been implemented, forcing smelters to treat their gases to conform to national and international environmental standards. In Chile, decontamination plants required by the government started operating from 1993 to 2000. Thereafter, Chilean copper production more than doubled while As emission levels declined, and the same reduction was observed in the Mount Johns ice core. After 1999, arsenic concentrations in our samples decreased to levels comparable to the period before 1900.

  13. Prehistoric human settling on the Tibetan Plateau

    Science.gov (United States)

    Chen, Fahu; Zhang, Dongju; Dong, Guanghui

    2017-04-01

    When and where did human first settle down on the Tibetan Plateau is under hot debate among archaeologist, anthropologists, geneticist and paleo-geographers. Based on systematic archaeological, chronological and archaeo-botanical studies of 53 sites in Northeastern Tibetan Plateau, we propose that agriculture facilitated human permanent settlement on the Tibetan Plateau initially since 5200 years ago below 2500 masl and since 3600 years ago up to around 4000 masl, possibly assisted by domesticated animals (Chen et al. 2015). By studying hand- and footprints in Chusang, Meyer et al. (2016) argue that hunter-gatherers permanently occupied central Tibetan Plateau in early Holocene without the help of agriculture. However, we think the limited hand- and footprints evidence found in Chusang could indicate no more than prehistoric hunter-gatherers presence on the remote central Tibetan Plateau in the early Holocene. In addition, by reviewing all the published archaeological data, we propose that human migrated to the Tibetan Plateau from the last Deglacial period to late Holocene mainly from North China via Yellow River valley and its tributary valleys in the Northeastern Tibetan Plateau (NETP). This migration is constituted of four stages (Upper Paleolithic, Epi-Paleolithic, Neolithic and Bronze Age) when human adapted to the high altitude environment and climate change with different strategies and techniques. Particularly, the prevail of microlithic technology in North China provoked hunter-gatherers' first visit to the NETP in relatively ameliorated last Deglacial period, and the the quick development of millet farming and subsequent mixed barley-wheat farming and sheep herding facilitated farmers and herders permanently settled in Tibetan Plateau, even above 3000 masl, during mid- and late Holocene. References: Chen et al., 2015. Agriculture facilitated permanent human occupation of the Tibetan Plateau after 3600 BP. Science, 347: 248-250. Meyer et al., 2016

  14. Circulation and its seasonal variability in region around the Kerguelen Plateau

    Institute of Scientific and Technical Information of China (English)

    Shi Jiuxin(史久新); Le Kentang(乐肯堂); Byung Ho Choi

    2002-01-01

    A coupled ice-ocean isopycnal numerical model of the Southern Ocean is established to study the circulation and its seasonal variability in the region around the Kerguelen Plateau. An analysis of the simulated results shows significant stripe-like structure and non-zonal feature of the Antarctic Circumpolar Current (ACC) in this region. ACC begins to bifurcate and to turn its direction before meeting the plateau. The southernmost branch of ACC is near to the Antarctic coast and displays its strong interaction with the westward Antarctic Slope Current. The northern branch of ACC has a tendency of annual variations while the southern one varies in a semiannual cycle. The variation phases of both branches are coincident with that of the wind stress in this region.

  15. Evaluation of single-band snow-patch mapping using high-resolution microwave remote sensing: an application in the maritime Antarctic

    Science.gov (United States)

    Mora, Carla; Jiménez, Juan Javier; Pina, Pedro; Catalão, João; Vieira, Gonçalo

    2017-01-01

    The mountainous and ice-free terrains of the maritime Antarctic generate complex mosaics of snow patches, ranging from tens to hundreds of metres. These can only be accurately mapped using high-resolution remote sensing. In this paper we evaluate the application of radar scenes from TerraSAR-X in High Resolution SpotLight mode for mapping snow patches at a test area on Fildes Peninsula (King George Island, South Shetlands). Snow-patch mapping and characterization of snow stratigraphy were conducted at the time of image acquisition on 12 and 13 January 2012. Snow was wet in all studied snow patches, with coarse-grain and rounded crystals showing advanced melting and with frequent ice layers in the snow pack. Two TerraSAR-X scenes in HH and VV polarization modes were analysed, with the former showing the best results when discriminating between wet snow, lake water and bare soil. However, significant overlap in the backscattering signal was found. Average wet-snow backscattering was -18.0 dB in HH mode, with water showing -21.1 dB and bare soil showing -11.9 dB. Single-band pixel-based and object-oriented image classification methods were used to assess the classification potential of TerraSAR-X SpotLight imagery. The best results were obtained with an object-oriented approach using a watershed segmentation with a support vector machine (SVM) classifier, with an overall accuracy of 92 % and Kappa of 0.88. The main limitation was the west to north-west facing snow patches, which showed significant error, an issue related to artefacts from the geometry of satellite imagery acquisition. The results show that TerraSAR-X in SpotLight mode provides high-quality imagery for mapping wet snow and snowmelt in the maritime Antarctic. The classification procedure that we propose is a simple method and a first step to an implementation in operational mode if a good digital elevation model is available.

  16. Future development of the PLATO Observatory for Antarctic science

    Science.gov (United States)

    Ashley, Michael C. B.; Bonner, Colin S.; Everett, Jon R.; Lawrence, Jon S.; Luong-Van, Daniel; McDaid, Scott; McLaren, Campbell; Storey, John W. V.

    2010-07-01

    PLATO is a self-contained robotic observatory built into two 10-foot shipping containers. It has been successfully deployed at Dome A on the Antarctic plateau since January 2008, and has accumulated over 730 days of uptime at the time of writing. PLATO provides 0.5{1kW of continuous electrical power for a year from diesel engines running on Jet-A1, supplemented during the summertime with solar panels. One of the 10-foot shipping containers houses the power system and fuel, the other provides a warm environment for instruments. Two Iridium satellite modems allow 45 MB/day of data to be transferred across the internet. Future enhancements to PLATO, currently in development, include a more modular design, using lithium iron-phosphate batteries, higher power output, and a light-weight low-power version for eld deployment from a Twin Otter aircraft. Technologies used in PLATO include a CAN (Controller Area Network) bus, high-reliability PC/104 com- puters, ultracapacitors for starting the engines, and fault-tolerant redundant design.

  17. Modelling the Antarctic Ice Sheet

    DEFF Research Database (Denmark)

    Pedersen, Jens Olaf Pepke; Holm, A.

    2015-01-01

    The Antarctic ice sheet is a major player in the Earth’s climate system and is by far the largest depository of fresh water on the planet. Ice stored in the Antarctic ice sheet (AIS) contains enough water to raise sea level by about 58 m, and ice loss from Antarctica contributed significantly...... Science) Antarctic Ice Sheet (DAIS) model (Shaffer 2014) is forced by reconstructed time series of Antarctic temperature, global sea level and ocean subsurface temperature over the last two glacial cycles. In this talk a modelling work of the Antarctic ice sheet over most of the Cenozoic era using...

  18. Free amino acids in Antarctic aerosol: potential markers for the evolution and fate of marine aerosol

    Directory of Open Access Journals (Sweden)

    E. Barbaro

    2015-01-01

    Full Text Available To investigate the impact of marine aerosols on global climate change it is important to study their chemical composition and size distribution. Amino acids are a component of the organic nitrogen in aerosols, particles containing amino acids have been found to be efficient ice nuclei. The main aim of this study was to investigate the L- and D-free amino acid composition as possible tracers of primary biological production in Antarctic aerosols from three different areas: two continental bases, Mario Zucchelli Station (MZS on the coast of the Ross Sea, Concordia Station at Dome C on the Antarctic Plateau, and the Southern Ocean near the Antarctic continent. Studying the size distribution of amino acids in aerosols allowed us to characterize this component of the water-soluble organic carbon (WSOC in marine aerosols near their source and after long-range transport. The presence of only free L-amino acids in our samples is indicative of the prevalence of phytoplanktonic material. Sampling at these three points allowed us to study the reactivity of these compounds during long-range transport. The mean total amino acid concentration detected at MZS was 11 pmol m−3, a higher percentage of amino acids were found in the fine fraction. The aerosol samples collected at Dome C had the lowest amino acid values (0.7 and 0.8 pmol m−3 and the coarse particles were found to be enriched with amino acids compared to the coastal site. The amino acid composition had also changed suggesting that physical and chemical transformations had occurred during long range transport. During the sampling cruise on the R/V talica on the Southern Ocean, high concentrations of amino acids were found in the total suspended particles, this we attribute to the presence of intact biological material in the sample.

  19. Monsoon variability for the past 4 ka derived from high-resolution analyses of sediments from lake Nam Co, central Tibetan Plateau

    Science.gov (United States)

    Kasper, T.; Haberzettl, T.; Doberschütz, S.; Daut, G.; Mäusbacher, R.; Wang, J.; Zhu, L.; Wennrich, V.

    2010-12-01

    The presented project aims to reconstruct processes within lake Nam Co (central Tibetan Plateau; 4718 m a.s.l.), its environment and climatic conditions. By using a multi-proxy approach for this study we present high resolution data covering the past 4 ka. During a field campaign in September 2008 five gravity cores (68 cm to 115 cm length) were recovered in addition to one piston core with a total length of 11 m (water depth: 93 m). This study focuses on data from sediments of two gravity cores (NC08/01 Pilot 3 & Pilot 4). A wide spectrum of sedimentological, geochemical and mineralogical investigations was carried out. Results are presented for XRD measurements, XRF-core scans, grain size analysis and SEM-image analyses. Data are completed by an age-depth model using 210Pb and 137Cs analyses as well as eleven AMS 14C-ages. In addition this model is supported by excellent agreement between secular variations detected in one of the cores to geomagnetic field models. This is a significant improvement of the chronology as the catchments of most lacustrine systems on the plateau contain carbonates resulting in a carbon reservoir effect for radiocarbon dates. By the comparison of our record with the geomagnetic field models we assure that there is no change in this effect through time. Sediments exhibit homogeneous color and only minor variations regarding grain size distribution. According to the XRD measurements the main minerogenic components of the sediment, such as quartz, calcite, feldspars (albite & orthoclase) and muscovite show only minor fluctuations. In addition the presence of monohydrocalcite (CaCO3×H2O) (MHC), was proven by both XRD-measurements and SEM imaging. The presence of this metastable phase of CaCO3 is meant to be an indicator for intervals of cold climate or for evaporative settings (Li et al. 2008). Results of the high-resolution XRF-core scan (0.2 cm interval) show clear variability. After removing elements with too low counts 8 element scans

  20. Neogene kinematic history of Nazca-Antarctic-Phoenix slab windows beneath Patagonia and the Antarctic Peninsula

    Science.gov (United States)

    Breitsprecher, Katrin; Thorkelson, Derek J.

    2009-01-01

    The Patagonian slab window is a subsurface tectonic feature resulting from subduction of the Nazca-Antarctic spreading-ridge system (Chile Rise) beneath southern South America. The geometry of the slab window had not been rigorously defined, in part because of the complex nature of the history of ridge subduction in the southeast Pacific region, which includes four interrelated spreading-ridge systems since 20 Ma: first, the Nazca-Phoenix ridge beneath South America, then simultaneous subduction of the Nazca-Antarctic and the northern Phoenix-Antarctic spreading-ridge systems beneath South America, and the southern Phoenix-Antarctic spreading-ridge system beneath Antarctica. Spreading-ridge paleo-geographies and rotation poles for all relevant plate pairs (Nazca, Phoenix, Antarctic, South America) are available from 20 Ma onward, and form the mathematical basis of our kinematic reconstruction of the geometry of the Patagonia and Antarctic slab windows through Neogene time. At approximately 18 Ma, the Nazca-Phoenix-Antarctic oceanic (ridge-ridge-ridge) triple junction enters the South American trench; we recognize this condition as an unstable quadruple junction. Heat flow at this junction and for some distance beneath the forearc would be considerably higher than is generally recognized in cases of ridge subduction. From 16 Ma onward, the geometry of the Patagonia slab window developed from the subduction of the trailing arms of the former oceanic triple junction. The majority of the slab window's areal extent and geometry is controlled by the highly oblique (near-parallel) subduction angle of the Nazca-Antarctic ridge system, and by the high contrast in relative convergence rates between these two plates relative to South America. The very slow convergence rate of the Antarctic slab is manifested by the shallow levels achieved by the slab edge (< 45 km); thus no point on the Antarctic slab is sufficiently deep to generate "normal" mantle-derived arc-type magmas

  1. Recovering greater fungal diversity from pristine and diesel fuel contaminated Sub-Antarctic soil through cultivation using a high and a novel low nutrient approach

    Directory of Open Access Journals (Sweden)

    Belinda Carlene Ferrari

    2011-11-01

    Full Text Available Novel cultivation strategies for bacteria are widespread and are well described for recovering greater diversity from the hitherto unculturable majority. While similar approaches have not been demonstrated for fungi it has been suggested that of the 1.5 million estimated species less than 5% have been recovered into pure culture. Fungi are known to be involved in many degradative processes, including the breakdown of hydrocarbons, and it has been speculated that in Polar Regions they contribute significantly to bioremediation of soils contaminated with hydrocarbons. Given the biotechnological potential of fungi there is a need to increase efforts for greater species recovery, particularly from extreme environments such as sub-Antarctic Macquarie Island. In this study, like the hitherto unculturable bacteria, high concentrations of nutrients selected for predominantly different species to that recovered using low nutrient media. By combining both approaches to cultivation from contaminated and non-contaminated soils, 99 fungal species were recovered, including 42 yet unidentified species, several of which were isolated from soils containing high concentrations of diesel fuel. These novel species will now be characterized for their potential role in hydrocarbon degradation.

  2. [Mediator effect analysis of the trait coping style on job stress and fatigue of the military personnel stationed in plateau and high cold region].

    Science.gov (United States)

    Zhang, J J; Jia, J M; Tao, N; Song, Z X; Ge, H; Jiang, Y; Tian, H; Qiu, E C; Tang, J H; Liu, J W

    2017-03-20

    Objective: To investigate the fatigue status of military personnel stationed in plateau and high cold region, and to analyze the mediator effect of trait coping style on job stress and fatigue. Methods: In October 2010, with the method of cluster random sampling survey, 531 military personnel stationed in plateau and high cold region were chosen as subject. The fatigue status were evaluated by the Chinese version multidimensional fatigue inventory (MFI-20) , job stress were evaluated by the Job Stress Survey (JSS) , and trait coping style were evaluated by the Trait Coping Style Questionnaire (TCSQ) . Results: According to the information of different population characteristics, mean rank of physical fatigue about the urban (town) group were higher than that of rural group (Z=-2.200, Pmilitary officers, sergeancy and soldier group (F=18.965, Pmilitary officers, sergeancy and soldier group (F=14.711, P<0.05) . The score of negative coping style were positively correlated with the score of physical fatigue (r(s)=0.129) , reduced activity (r(s)=0.123) , reduced motivation (r(s)=0.149) and general fatigue (r(s)=0.174) respectively, the score of organizational support lack strength were positively correlated with the score of physical fatigue (r(s)=0.090) , reduced activity (r(s)=0.098) , reduced motivation (r(s)=0.099) and general fatigue (r(s)=0.130) respectively. The mediator effect of negative coping style on the job stress and fatigue was 0.013 (P<0.01) . Conclusion: The fatigue statuses of the urban (town) group and the up or equal 20-years old age group are poor, and the negative coping style plays mediator effect on the job stress and fatigue.

  3. Vegetation and climatic changes during the Middle Miocene in the Wushan Basin, northeastern Tibetan Plateau: Evidence from a high-resolution palynological record

    Science.gov (United States)

    Hui, Zhengchuang; Li, Jijun; Song, Chunhui; Chang, Jing; Zhang, Jun; Liu, Jia; Liu, Shanpin; Peng, Tingjiang

    2017-10-01

    There remains no detailed record of the Middle Miocene vegetation and climatic changes which occurred in central Asia and their possible driving mechanisms. This is because there is still a lack of high resolution records. Here, we present a sporopollen record from the Wushan Basin on the northeastern Tibetan Plateau, central Asia, spanning the period ∼16.1-13.6 Ma. The sporopollen record shows that a dense mixed forest growing in rather warm and humid climatic conditions was affected by a general drying trend during the period ∼16.1-15 Ma. It demonstrates that although the climate was generally warm and humid during the Middle Miocene Climate Optimum (MMCO), it was also a time of climatic instability. The dense forest gave way to an open forest in response to a less humid climate between ∼15 and 14.4 Ma. Dense mixed forest made a return with an increasingly humid climate during ∼14.4-13.8 Ma. This vegetation and climatic succession could be associated with global cooling, or more particularly, a higher temperature rebound set against the background of a long-term cooling trend. A more open forest appearing in response to drier and colder climatic conditions dominated the study area during the ∼13.8-13.6 Ma period. This could be compared to the rapid global cooling event Mi-3b. This significant global cooling event exerted a major impact on terrestrial vegetation, climate and biota. Our high resolution sporopollen record demonstrates that global climate changes could have been the first order driving force for the Middle Miocene vegetation and climate changes seen in the Wushan Basin in central continental Asia, with the tectonic uplift of the Tibetan Plateau probably playing a subordinate role.

  4. Direct gravimetric measurements of the mass of the antarctic aerosol collected by high volume sampler: PM10 summer seasonal variation at Terra Nova Bay.

    Science.gov (United States)

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

    2005-01-01

    An on-site procedure was set up for direct gravimetric measurement of the mass of aerosol collected using high volume impactors (aerodynamic size cut point of 10 microm, PM10); this knowledge has hitherto been unavailable. Using a computerized microbalance in a clean chemistry laboratory, under controlled temperature (+/-0.5 degrees C) and relative humidity (+/-1%), continuous, long time filter mass measurements (hours) were carried out before and after exposure, after a 48 h minimun equilibration at the laboratory conditions. The effect of the electrostatic charge was exhausted in 30-60 min, after which stable measurements were obtained. Measurements of filters exposed for 7-11 days (1.13 m3 min(-1)) in a coastal site near Terra Nova Bay (December 2000 - February 2001), gave results for aerosol mass in the order of 10-20 mg (SD approximately 2 mg), corresponding to atmospheric concentrations of 0.52-1.27 microg m(-3). Data show a seasonal behaviour in the PM10 content with an increase during December - early January, followed by a net decrease. The above results compare well with estimates obtained from proxy data for the Antarctic Peninsula (0.30 microg m(-3)), the Ronne Ice Shelf (1.49 microg m(-3)), and the South Pole (0.18 microg m(-3), summer 1974-1975, and 0.37 microg m(-3), average summer seasons 1975-1976 and 1977-1978), and from direct gravimetric measurements recently obtained from medium volume samplers at McMurdo station (downwind 3.39 microg m(-3), upwind 4.15 microg m(-3)) and at King George Island (2.5 microg m(-3), summer, particle diameter <20 microm). This finding opens the way to the direct measurement of the chemical composition of the Antarctic aerosol and, in turn, to a better knowledge of the snow/air relationships as required for the reconstruction of the chemical composition of past atmospheres from deep ice core data.

  5. Tibial Plateau Fractures

    DEFF Research Database (Denmark)

    Elsøe, Rasmus

    This PhD thesis reported an incidence of tibial plateau fractures of 10.3/100,000/year in a complete Danish regional population. The results reported that patients treated for a lateral tibial plateau fracture with bone tamp reduction and percutaneous screw fixation achieved a satisfactory level...... with only the subgroup Sport significantly below the age matched reference population. The thesis reports a level of health related quality of life (Eq5d) and disability (KOOS) significantly below established reference populations for patients with bicondylar tibial plateau fracture treated with a ring...... fixator, both during treatment and at 19 months following injury. In general, the thesis demonstrates that the treatment of tibial plateau fractures are challenging and that some disabilities following these fractures must be expected. Moreover, the need for further research in the area, both with regard...

  6. Maintenance of high HCl/Cl{sub y} and NO{sub x}/NO{sub y} in the Antarctic vortex: A chemical signature of confinement during spring

    Energy Technology Data Exchange (ETDEWEB)

    Michelsen, H. A. [Sandia National Laboratories, Livermore, California (United States); Webster, C. R. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California (United States); Manney, G. L. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California (United States); Scott, D. C. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California (United States); Margitan, J. J. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California (United States); May, R. D. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California (United States); Irion, F. W. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California (United States); Gunson, M. R. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California (United States); Russell, J. M. III [Center for Atmospheric Sciences, Hampton University, Hampton, Virginia (United States); Spivakovsky, C. M. [Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts (United States)

    1999-11-20

    Observations made in the 1994 Antarctic vortex show that Cl{sub y} recovered completely into HCl following conversion of Cl{sub y} reservoir species to active radicals, and NO{sub x} constituted a 4-5 times higher fraction of NO{sub y} inside the vortex than outside. Measurements made in October and November from the Airborne Southern Hemisphere Ozone Expedition/Measurements of the Atmospheric Effects of Stratospheric Aircraft (ASHOE/MAESA) ER-2 aircraft mission, the third Atmospheric Laboratory for Applications and Science (ATLAS-3) space shuttle mission, and the Upper Atmosphere Research Satellite (UARS) demonstrate that this unusual partitioning of Cl{sub y} and NO{sub y} was maintained for at least 4 weeks in the springtime vortex. In response to severe ozone loss, abundances of HCl and NO{sub x} remained high despite temperatures low enough to reactivate Cl{sub y} and convert NO{sub x} to HNO{sub 3} via heterogeneous processes. Thus, under severely ozone depleted conditions, high HCl and NO{sub x} abundances in the vortex are maintained until the vortex breaks up or an influx of ozone-rich extravortex air is entrained into the vortex. These observations suggest that the flux of extravortex air entering the core of the lower stratospheric vortex was small or negligible above {approx}400 K during late spring, despite weakening of the vortex during this time period. Results of a photochemical model constrained by the measurements suggest that extravortex air entrained into the vortex during October and early November made up less than 5% of the vortex core air at 409 K. The model results also show that heterogeneous chemistry has little effect on the Cl{sub y} and NO{sub y} partitioning once high abundances of HCl have been attained under ozone depleted conditions, even when aerosol loading is high. (c) 1999 American Geophysical Union.

  7. Interpretation of ground and aeromagnetic surveys of Palmer Land, Antarctic Peninsula

    Directory of Open Access Journals (Sweden)

    V. N. Masolov

    2000-06-01

    Full Text Available Aeromagnetic data for Palmer Land provide new information on crustal structures of the Antarctic Peninsula. Features shown on the compilation of the Lassiter Coast and Orville Coast are characterized by systems of subparallel regional anomaly zones and lineaments. The magnetic data reveal the widespread presence of an orthogonal pattern of crosscutting linear discontinuities that can be interpreted as a Late Cretaceous/Early Tertiary fracture pattern. The main displacements in the anomaly pattern between the two units are recognized in Wetmore-Irvine glaciers area where the structure of the Antarctic Peninsula changes orientation from SW-NE to S-N. The NW-SE trending transitional zone is probably a transfer zone associated with north-westerly movement of the Lassiter Coast crustal segment relative to the Orville Coast segment. Within the Lassiter Coast a fragment of Pacific Margin Anomaly (PMA, Central Plateau Magnetic Anomaly and East Coast Magnetic Anomaly (ECMA are mapped. Two-dimensional modelling suggests that PMA is caused by a limited depth body (8 km consisting of numerous plutons, probably, of different ages, composition and magnetization. The Central Plateau Magnetic Anomaly and the Merrick-Sweeney-Latady zone of the Orville Coast are represented by strong positive anomaly bands that are associated with gabbro-diorite rocks and accompanying plutons intruded near by the border of Mount Poster Formation and Latady Formation. The ECMA are alignments of high-amplitude magnetic anomalies caused by gabbro-diorite bodies, which are located within the framework of the Cretaceous granite-granodiorite plutons. Granite-granodiorite plutons of Lassiter Coast Intrusive Suite are mostly reflected by positive anomalies (100-500 nT. Modelling studies and the character of distribution of the magnetic anomalies suggest that the plutons of Lassiter Coast Intrusive Suite are prominently reflected in magnetic anomalies of regional extent. The plutonic

  8. Regional genetic diversity patterns in Antarctic hairgrass (Deschampsia antartica Desv.)

    NARCIS (Netherlands)

    van de Wouw, M.J.; Van Dijk, P.J.; Huiskes, A.H.L.

    2008-01-01

    Aim To determine patterns in diversity of a major Antarctic plant species, including relationships of Antarctic populations with those outside the Antarctic zone. Location Antarctic Peninsula, Maritime Antarctica, sub-Antarctic islands, Falkland Islands and South America. Methods Amplified fragment

  9. Aerosol particles at a high-altitude site on the Southeast Tibetan Plateau, China: Implications for pollution transport from South Asia

    Science.gov (United States)

    Zhao, Zhuzi; Cao, Junji; Shen, Zhenxing; Xu, Baiqing; Zhu, Chongshu; Chen, L.-W. Antony; Su, Xiaoli; Liu, Suixin; Han, Yongming; Wang, Gehui; Ho, Kinfai

    2013-10-01

    aerosol samples were collected from 16 July 2008 to 26 July 2009 at Lulang, a high-altitude (>3300m above sea level) site on the southeast Tibetan Plateau (TP); objectives were to determine chemical characteristics of the aerosol and identify its major sources. We report aerosol (total suspended particulate, TSP) mass levels and the concentrations of selected elements, carbonaceous species, and water-soluble inorganic ions. Significant buildup of aerosol mass and chemical species (organic carbon, element carbon, nitrate, and sulfate) occurred during the premonsoon, while lower concentrations were observed during the monsoon. Seasonal variations in aerosol and chemical species were driven by precipitation scavenging and atmospheric circulation. Two kinds of high-aerosol episodes were observed: one was enriched with dust indicators (Fe and Ca2+), and the other was enhanced with organic and elemental carbon (OC and EC), SO42-, NO3-, and Fe. The TSP loadings during the latter were 3 to 6 times those on normal days. The greatest aerosol optical depths (National Centers for Environmental Protection/National Center for Atmospheric Research reanalysis) occurred upwind, in eastern India and Bangladesh, and trajectory analysis indicates that air pollutants were transported from the southwest. Northwesterly winds brought high levels of natural emissions (Fe, Ca2+) and low levels of pollutants (SO42-, NO3-, K+, and EC); this was consistent with high aerosol optical depths over the western deserts and Gobi. Our work provides evidence that both geological and pollution aerosols from surrounding regions impact the aerosol population of the TP.

  10. The Pajarito Plateau: a bibliography

    Science.gov (United States)

    Mathien, Frances Joan; Steen, Charlie R.; Allen, Craig D.

    1993-01-01

    Pajarito Plateau is described as the high tableland that lies between the Jemez Mountains on the west and the Rio Grande on the east. From north to south, it extends from the Chama Valley to La Cañada de Cochiti (Hewett 1906:14)(Figure 1). Because human activity rarely stops at such definite boundaries, major ethnographic studies of Tewa (San Ildefonso and Santa Clara) and Keres (Cochiti) linguistic groups are included. (Even though most of the historic pueblos occupied by the Tewa and Keres are not located on the Pajarito Plateau, oral traditions and archaeological data suggest that these groups once occupied sites on the plateau.) Towa studies are not included because Steen believed Towa ancestors were not involved in major cultural developments of the Pajarito Plateau. In addition, a bibliography of the Jemez area (home of Towa people) has been prepared by Michael Elliott (1982) and included with his nomination of large Pueblo sites near Jemez Springs to the National Register of Historic Places that is on file at the Museum of New Mexico, Laboratory of Anthropology, in Santa Fe. Both Steen and Mathien included references to geographically and historically related material that does not focus on the Pajarito Plateau but, nonetheless, is important to understanding the area's archaeology and physical environment, for example, lithic resources available from Cerro Pedernal or in the Sangre de Cristo Mountains.

  11. Biodiversity and adaptive evolution of Antarctic notothenioid fishes

    Directory of Open Access Journals (Sweden)

    Qianghua Xu

    2014-01-01

    Full Text Available The sea surrounding the Antarctic continent is one of the coldest regions in the world. It provides an environmentally unique and isolated “hotbed” for evolution to take place. In the past 30 million years, species of Perciform suborder Notothenioidei evolved and diversified from a benthic and temperate-water ancestor, and now dominate the fish fauna of the coldest ocean. Because of their distribution across temperature zones both inside and outside the Antarctic Polar Front, notothenioid fishes are regarded as excellent model organisms for exploring mechanisms of adaptive evolution, particularly cold adaptation. We first summarize research progress on the biodiversity of Antarctic fish and then review current findings on the peculiar biological characteristics of Antarctic notothenioids that evolved in response to a freezing environment. Research has revealed that extensive gene duplication and transcriptomic changes occurred during the adaptive radiation of notothenioid fish. Examples of highly duplicated genes in the Antarctic lineages include genes encoding hepcidin, and zona pellucida proteins, in addition to various retrotransposable elements. A few genes from Antarctic notothenioid fishes have been used as transgenes and demonstrated to be effective in making transgenic plants cold-hardy. In the coming years, the genomes of some Antarctic notothenioid species will be fully sequenced and the adaptive functions of duplicated genes will be further elucidated. Such studies will deepen our understanding of how genomes evolve in freezing environments, and provide an improved knowledge of molecular mechanisms of cold adaptation.

  12. Antarctic science preserve polluted

    Science.gov (United States)

    Simarski, Lynn Teo

    Geophysicists are alarmed at the electromagnetic pollution of a research site in the Antarctic specifically set aside to study the ionosphere and magnetosphere. A private New Zealand communications company called Telecom recently constructed a satellite ground station within the boundaries of this Site of Special Scientific Interest (SSSI), protected since the mid-1970s. The placement of a commercial facility within this site sets an ominous precedent not only for the sanctity of other SSSIs, but also for Specially Protected Areas—preserves not even open to scientific research, such as certain penguin rookeries.The roughly rectangular, one-by-one-half mile site, located at Arrival Heights not far from McMurdo Station, is one of a number of areas protected under the Antarctic treaty for designated scientific activities. Many sites are set aside for geological or biological research, but this is the only one specifically for physical science.

  13. Spectroscopic Observations of SN 2012fr: A Luminous Normal Type Ia Supernova with Early High Velocity Features and Late Velocity Plateau

    CERN Document Server

    Childress, M J; Sim, S A; Tucker, B E; Yuan, F; Schmidt, B P; Cenko, S B; Silverman, J M; Contreras, C; Hsiao, E Y; Phillips, M; Morrell, N; Jha, S W; McCully, C; Filippenko, A V; Anderson, J P; Benetti, S; Bufano, F; de Jaeger, T; Forster, F; Gal-Yam, A; Guillou, L Le; Maguire, K; Maund, J; Mazzali, P A; Pignata, G; Smartt, S; Spyromilio, J; Sullivan, M; Taddia, F; Valenti, S; Bayliss, D D R; Bessell, M; Blanc, G A; Carson, D J; Clubb, K I; de Burgh-Day, C; Desjardins, T D; Fang, J J; Fox, O D; Gates, E L; Ho, I-T; Keller, S; Kelly, P L; Lidman, C; Loaring, N S; Mould, J R; Owers, M; Ozbilgen, S; Pei, L; Pickering, T; Pracy, M B; Rich, J A; Schaefer, B E; Scott, N; Stritzinger, M; Vogt, F P A; Zhou, G

    2013-01-01

    We present 65 optical spectra of the Type Ia supernova SN 2012fr, of which 33 were obtained before maximum light. At early times SN 2012fr shows clear evidence of a high-velocity feature (HVF) in the Si II 6355 line which can be cleanly decoupled from the lower velocity "photospheric" component. This Si II 6355 HVF fades by phase -5; subsequently, the photospheric component exhibits a very narrow velocity width and remains at a nearly constant velocity of v~12,000 km/s until at least 5 weeks after maximum brightness. The Ca II infrared (IR) triplet exhibits similar evidence for both a photospheric component at v~12,000 km/s with narrow line width and long velocity plateau, as well as a high-velocity component beginning at v~31,000 km/s two weeks before maximum. SN 2012fr resides on the border between the "shallow silicon" and "core-normal" subclasses in the Branch et al. (2009) classification scheme, and on the border between normal and "high-velocity" SNe Ia in the Wang et al. (2009a) system. Though it is a ...

  14. Vegetation and Cold Trapping Modulating Elevation-dependent Distribution of Trace Metals in Soils of a High Mountain in Eastern Tibetan Plateau

    Science.gov (United States)

    Bing, Haijian; Wu, Yanhong; Zhou, Jun; Li, Rui; Luo, Ji; Yu, Dong

    2016-04-01

    Trace metals adsorbed onto fine particles can be transported long distances and ultimately deposited in Polar Regions via the cold condensation effect. This study indicated the possible sources of silver (Ag), cadmium (Cd), copper (Cu), lead (Pb), antimony (Sb) and zinc (Zn) in soils on the eastern slope of Mt. Gongga, eastern Tibetan Plateau, and deciphered the effects of vegetation and mountain cold condensation on their distributions with elevation. The metal concentrations in the soils were comparable to other mountains worldwide except the remarkably high concentrations of Cd. Trace metals with high enrichment in the soils were influenced from anthropogenic contributions. Spatially, the concentrations of Cu and Zn in the surface horizons decreased from 2000 to 3700 m a.s.l., and then increased with elevation, whereas other metals were notably enriched in the mid-elevation area (approximately 3000 m a.s.l.). After normalization for soil organic carbon, high concentrations of Cd, Pb, Sb and Zn were observed above the timberline. Our results indicated the importance of vegetation in trace metal accumulation in an alpine ecosystem and highlighted the mountain cold trapping effect on trace metal deposition sourced from long-range atmospheric transport.

  15. Adjustment of pigment composition in Desmarestia (Desmarestiaceae species along a sub-Antarctic to Antarctic latitudinal gradient

    Directory of Open Access Journals (Sweden)

    Andrés Mansilla

    2016-08-01

    Full Text Available Photosynthesis at high latitudes demands efficient strategies of light utilization to maintain algal fitness and performance. The fitness, and physiological adaptation, of a plant or algae species depends in part on the abundance and efficiency of the pigments it can produce to utilize the light resource from its environment. We quantified pigment composition and concentration in six species of the brown macroalgal genus Desmarestia, collected from sub-Antarctic sites (Strait of Magellan, Beagle Channel–Cape Horn Province and sites on the Antarctic Peninsula and adjacent islands. Sub-Antarctic Desmarestia species exhibited lower concentrations of chlorophyll a, chlorophyll c and fucoxanthin than endemic Antarctic species. Antarctic samples of D. menziesii and D. antarctica collected along a decreasing latitudinal gradient showed spatial and interspecific differences in light-harvesting pigment composition. Our results suggest distinct physiological adjustments in Desmarestia species in response to heterogeneous abiotic environmental conditions. The marine sub-Antarctic and Antarctic ecosystems are characterized by harsh environments (e.g., extreme irradiance, photoperiod, temperature, salinity to which the physiology of macroalgal species must adapt.

  16. Radiative plateau inflation

    CERN Document Server

    Ballesteros, Guillermo

    2016-01-01

    We describe how monomial chaotic inflation becomes compatible with the latest CMB data thanks to radiative corrections producing a plateau. The interactions of the inflation with other fields, required for reheating, can flatten the potential and moderate the production of primordial gravitational waves, keeping these below the current upper bound. We show that the appearance of a plateau requires that the inflaton couples to fermions and to another scalar or a gauge group. We give concrete examples of minimal particle physics models leading to plateaus for quadratic and quartic chaotic inflation. We also provide a three-parameter model-independent description of radiatively corrected inflation that is amenable to CMB analyses.

  17. Determination and Temperature Dependence of Plateau Modulus for Polymerization of Propylene to Isotactic Polypropylene with Ultra-high Molecular Weight under Catalysis of Ziegler-Natta Catalyst

    Institute of Scientific and Technical Information of China (English)

    DING Jian; DING Xue-jia; XU Ri-wei; YU Ding-sheng

    2005-01-01

    The viscoelastic behavior of isotactic polypropylene with ultra-high molecular weight (UHPPH) and broad molecular weight distribution(MWD), produced in the presence of Ziegler-Natta catalyst, was investigated by means of oscillatory rheometry at 180 and 200 ℃, whose loss modulus(G") plots at 180 and 200 ℃versus the natural logarithm of angular frequency(ω) present a pronounced maximum at 34.35 and 69.21 rad/s, respectively, and do not show a maximum peak at 0. 01-100 rad/s for Ziegler-Natta catalyzing ethylenepropylene random copolymerization (PPR) with a conventional molecular weight and broad MWD. The fact indicates that the high molecular weight is responsible for a maximum peak of G"(ω) vs. lnω curves for UHPPH. This makes it possible to determine the plateau modulus (G0N) of UHPPH from a certain experimental temperature G"(ω) curve directly. For UHPPH, the G0N determined to be 4. 28×105 and 3. 62×105 Pa at 180and 200 ℃, respectively, decreases with the increase of temperature and is independent of the molecular weight, which directly confirms reputation theoretical prediction that the G0N has no relation to the molecular weight.

  18. Research Update: Prediction of high figure of merit plateau in SnS and solid solution of (Pb,Sn)S

    Science.gov (United States)

    Hao, Shiqiang; Dravid, Vinayak P.; Kanatzidis, Mercouri G.; Wolverton, Christopher

    2016-10-01

    Direct conversion between thermal and electrical energy can be achieved by thermoelectric materials, which provide a viable route for power generation and solid state refrigeration. Here, we use a combination of energetic, electronic, and vibrational first-principles based results to predict the figure of merit performance in hole doped single crystals of SnS and (Pb,Sn)S. We find high ZT values for both materials, specifically for (Pb,Sn)S along the b-axis. Both SnS and (Pb,Sn)S have excellent power factors when doped, due to a combination of increased electrical conductivity (due to doping) and a significantly enhanced Seebeck coefficient obtained by a doping-induced multiband effect. Anharmonic phonon calculations combined with a Debye-Calloway model show that the lattice thermal conductivity of both compounds is low, due to intrinsic anharmonicity, and is lowered further by the random, solid solution nature of the cation sublattice of (Pb,Sn)S. (Pb,Sn)S exhibits a high ZT plateau ranging from 1.3 at 300 K to 1.9 at 800 K. The overall ZT of the hole doped (Pb,Sn)S crystals is predicted to outperform most of the current state-of-the-art thermoelectric sulfide materials.

  19. Antarctic, Sub-Antarctic and cold temperate echinoid database

    Directory of Open Access Journals (Sweden)

    Benjamin Pierrat

    2012-06-01

    Full Text Available This database includes spatial data of Antarctic, Sub-Antarctic and cold temperate echinoid distribution (Echinodermata: Echinoidea collected during many oceanographic campaigns led in the Southern Hemisphere from 1872 to 2010. The dataset lists occurrence data of echinoid distribution south of 35°S latitude, together with information on taxonomy (from species to genus level, sampling sources (cruise ID, sampling dates, ship names and sampling sites (geographic coordinates and depth. Echinoid occurrence data were compiled from the Antarctic Echinoid Database (David et al., 2005a, which integrates records from oceanographic cruises led in the Southern Ocean until 2003. This database has been upgraded to take into account data from oceanographic cruises led after 2003. The dataset now reaches a total of 6160 occurrence data that have been checked for systematics reliability and consistency. It constitutes today the most complete database on Antarctic and Sub-Antarctic echinoids.

  20. Identifying the source regions of persistent organic pollutants (POPs) in the southern Tibetan Plateau

    Science.gov (United States)

    Gong, P.; Wang, X.; Yao, T.

    2016-12-01

    A worldwide attention focus on the semi-volatilities and long-range atmospheric transport potential of persistent organic pollutants (POPs). Even in the remote regions with less anthropological activities (such as Arctic, Antarctic), POPs are often detected in air and finally are trapped by the surface ground, which made those regions as a "sink" of POPs. The Tibetan Plateau is also a remote region, and it is adjacent to South Asia with huge emission of POPs. The strong monsoon favors to the atmospheric transport of pollutants from South Asia to the Tibetan Plateau. Unlike Arctic and Antarctic, the Tibetan Plateau can become a "secondary source" for some POPs and make them spread globally. By now, some efforts were conducted to report that South Asia is one of the primary source region of POPs in the Tibetan Plateau. In this study, the detailed source regions were identified using 1-year observed atmospheric POPs data in three sites distributing the southern Tibetan Plateau (Lhasa, Lulang, and Lijiang). The highest concentrations of atmospheric POPs in the three sites all occurred in the Monsoon season (June-September), implying that the Indian monsoon may be the driving force of POPs transport to the southern Tibetan Plateau. The relative components of POPs in these sites are similar with those in India, which suggest that South Asia (especially India) might be the main source regions. The results of potential source contribution function (PSCF) further identified that the offshore of Bengal Bay is the most probable emission source region of the POPs invading into the Tibetan Plateau. The mega-cities, such as Kolkata, Bhubaneswar, Chennai, Dhaka, Chittagong, around the Bengal Bay supplied the major contribution of the POPs which transported to the Tibetan Plateau.

  1. Plateau Indian Ways with Words

    Science.gov (United States)

    Monroe, Barbara

    2009-01-01

    The indigenous rhetoric of the Plateau Indians continues to exert a discursive influence on student writing in reservation schools today. Plateau students score low on state-mandated tests and on college writing assignments, in large part because the pervasive personalization of Plateau rhetoric runs counter to the depersonalization of academic…

  2. Greening the Plateau

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Located on the world’s largest plateau, Tibet Autonomous Region in China’s southwest has an average elevation of 4,000 meters. Tibet’s diverse natural landscapes, including snow-capped mountains, vast pastures and virgin forests, combined with its

  3. Impact of surface sensible heating over the Tibetan Plateau on the western Pacific subtropical high: A land-air-sea interaction perspective

    Science.gov (United States)

    Duan, Anmin; Sun, Ruizao; He, Jinhai

    2017-02-01

    The impact of surface sensible heating over the Tibetan Plateau (SHTP) on the western Pacific subtropical high (WPSH) with and without air-sea interaction was investigated in this study. Data analysis indicated that SHTP acts as a relatively independent factor in modulating the WPSH anomaly compared with ENSO events. Stronger spring SHTP is usually followed by an enhanced and westward extension of the WPSH in summer, and vice versa. Numerical experiments using both an AGCM and a CGCM confirmed that SHTP influences the large-scale circulation anomaly over the Pacific, which features a barotropic anticyclonic response over the northwestern Pacific and a cyclonic response to the south. Owing to different background circulation in spring and summer, such a response facilitates a subdued WPSH in spring but an enhanced WPSH in summer. Moreover, the CGCM results showed that the equatorial low-level westerly at the south edge of the cyclonic anomaly brings about a warm SST anomaly (SSTA) in the equatorial central Pacific via surface warm advection. Subsequently, an atmospheric Rossby wave is stimulated to the northwest of the warm SSTA, which in turn enhances the atmospheric dipole anomalies over the western Pacific. Therefore, the air-sea feedbacks involved tend to reinforce the effect of SHTP on the WPSH anomaly, and the role of SHTP on general circulation needs to be considered in a land-air-sea interaction framework.

  4. GPC-HPLC法测定南极磷虾油中虾青素及校正因子计算%Determination of astaxanthin in antarctic krill oil by GPC-high performance liquid chromatography and calculation of correction factor

    Institute of Scientific and Technical Information of China (English)

    孙伟红; 冷凯良; 邢丽红; 朱敏; 翟毓秀; 苗均魁; 朱兰兰

    2013-01-01

    Taking health products, antarctic krill oil, as the object in the paper, an analytical method based on gel permeation chromatography-high performance liquid chromatography (GPC-HPLC ) has been developed for the determination of astaxanthin in antarctic krill oil. The sample was purified by gel permeation chromatography, saponified by sodium hydroxide-methanol solution, and separated by a C30 liquid chromatographic column. In this paper, we established the purification conditions of gel permeation chromatography, the collection time of astaxanthin and astaxanthin easter was 7. 48 ~ 12. 60 min. The conditions of saponification were researched by exploring the solvents, volume of sodium hydroxide-methanol solution and saponification time on saponification efficiency of astaxanthin in antarctic krill oil. The results show that methylene chloride: methanol as saponification solvent had the best effect than other solvents, the most suitable volume for 0. 2 mol/L sodium hydroxide-methanol solution was 1 mL, and the best saponification time was 12 h by comparing among 1~18h at 4℃. We also investigated the effect of pH on stability of astaxanthin in antarctic krill oil, the content of astaxanthin had less influence on neutral environment among 0 ~ 12 h, but the content in serious decline and isomerization on alkaline environment. The contents of isomers of astaxanthin in antarctic krill oil were calculated by calibration factor, the calibration factor of 13-cis-astaxanthin to trans-astaxanthin was 1.3, and 9-cis-astaxanthin to trans-astaxanthin was 1.1, so we got the quantitative method of astaxanthin in krill oil. The limits of quantification for astaxanthin in antarctic krill oil were 0. 5 mg/kg. There were good linear relationship between the chromatographic peak area and the concentration in the range of 0. 1 mg/L ~ 5 mg/L with correlation coefficient over 0.999. The average recoveries were between 96.0% and 98.5%, and the precision of the method were 3. 0% ~5. 6

  5. Antarctic microfungi as models for exobiology

    Science.gov (United States)

    Onofri, S.; Selbmann, L.; Zucconi, L.; Pagano, S.

    2004-01-01

    Microfungi living in different Antarctic environments are generally well adapted to high stress conditions such as low temperatures, wide thermal fluctuations, high UV irradiance, and low water and nutrients availability; for this reason they could be investigated in order to explore limits of microbial life. Microfungi living in simple cryptoendolithic microbial communities inside the porosity of rocks in the Antarctic Dry Valleys, the closest terrestrial analogue of Mars, are particularly suitable for exobiological studies. Until now studies on exobiology focused mainly on prokaryotes; since cryptoendolithic black meristematic fungi are able to tolerate hard desiccation, high UV exposure, extremely low temperatures and wide thermal fluctuations, they are proposed as the best eukaryotic models for the biological exploration of Mars. Indeed, their adaptive strategies could be crucial as predictive tools in investigating the limits of life.

  6. Colorado Plateau Rapid Ecoregion Assessment Change Agents - Development - Current, Near-Term, and Long-Term Potential High Landscape Development

    Data.gov (United States)

    Bureau of Land Management, Department of the Interior — This map shows areas of high current, near-term, and long-term potential landscape development, based on factors such as urban areas, agriculture, roads, and energy...

  7. Antarctic Mapping Tools for MATLAB

    Science.gov (United States)

    Greene, Chad A.; Gwyther, David E.; Blankenship, Donald D.

    2017-07-01

    We present the Antarctic Mapping Tools package, an open-source MATLAB toolbox for analysis and plotting of Antarctic geospatial datasets. This toolbox is designed to streamline scientific workflow and maximize repeatability through functions which allow fully scripted data analysis and mapping. Data access is facilitated by several dataset-specific plugins which are freely available online. An open architecture has been chosen to encourage users to develop and share plugins for future Antarctic geospatial datasets. This toolbox includes functions for coordinate transformations, flight line or ship track analysis, and data mapping in georeferenced or projected coordinates. Each function is thoroughly documented with clear descriptions of function syntax alongside examples of data analysis or display using Antarctic geospatial data. The Antarctic Mapping Tools package is designed for ease of use and allows users to perform each step of data processing including raw data import, data analysis, and creation of publication-quality maps, wholly within the numerical environment of MATLAB.

  8. NITRATE REMOVAL BY ANTARCTIC PSYCHROPHILIC YEAST CELLS UNDER HIGH SALT CONDITIONS (19th Symposium on Polar Biology)

    OpenAIRE

    カタヤマ-ヒラヤマ, ケイコ; イシカワ, サトシ; ニシカワ, ジロウ; ツジ, マサオ; コミヤマ, ヨシヒロ; ヒラヤマ, キミアキ; Keiko, KATAYAMA-HIRAYAMA; Satoshi, ISHIKAWA; Jiro, NISHIKAWA; Masao, TSUJI; Yoshihiro, KOMIYAMA; Kimiaki, HIRAYAMA

    1998-01-01

    We researched nitrate removal in water with high salt concentrations at low temperature using Candida sp. which was isolated from the upper layer of Lake Vanda in the McMurdo Dry Valleys, Antarctica. The strain was cultured in a synthetic medium that contained nitrate as the sole nitrogen source The time course for the growth, and the nitrate and the total organic carbon (TOC) removals were examined aerobically in the presence of 0-20% NaCl at 5℃. The effects of pH and the C/N ratio on the re...

  9. Colorado Plateau magmatism and uplift by warming of heterogeneous lithosphere.

    Science.gov (United States)

    Roy, Mousumi; Jordan, Thomas H; Pederson, Joel

    2009-06-18

    The forces that drove rock uplift of the low-relief, high-elevation, tectonically stable Colorado Plateau are the subject of long-standing debate. While the adjacent Basin and Range province and Rio Grande rift province underwent Cenozoic shortening followed by extension, the plateau experienced approximately 2 km of rock uplift without significant internal deformation. Here we propose that warming of the thicker, more iron-depleted Colorado Plateau lithosphere over 35-40 Myr following mid-Cenozoic removal of the Farallon plate from beneath North America is the primary mechanism driving rock uplift. In our model, conductive re-equilibration not only explains the rock uplift of the plateau, but also provides a robust geodynamic interpretation of observed contrasts between the Colorado Plateau margins and the plateau interior. In particular, the model matches the encroachment of Cenozoic magmatism from the margins towards the plateau interior at rates of 3-6 km Myr(-1) and is consistent with lower seismic velocities and more negative Bouguer gravity at the margins than in the plateau interior. We suggest that warming of heterogeneous lithosphere is a powerful mechanism for driving epeirogenic rock uplift of the Colorado Plateau and may be of general importance in plate-interior settings.

  10. Antarctic marine biodiversity and deep-sea hydrothermal vents.

    Science.gov (United States)

    Chown, Steven L

    2012-01-01

    The diversity of many marine benthic groups is unlike that of most other taxa. Rather than declining from the tropics to the poles, much of the benthos shows high diversity in the Southern Ocean. Moreover, many species are unique to the Antarctic region. Recent work has shown that this is also true of the communities of Antarctic deep-sea hydrothermal vents. Vent ecosystems have been documented from many sites across the globe, associated with the thermally and chemically variable habitats found around these, typically high temperature, streams that are rich in reduced compounds and polymetallic sulphides. The animal communities of the East Scotia Ridge vent ecosystems are very different to those elsewhere, though the microbiota, which form the basis of vent food webs, show less differentiation. Much of the biological significance of deep-sea hydrothermal vents lies in their biodiversity, the diverse biochemistry of their bacteria, the remarkable symbioses among many of the marine animals and these bacteria, and the prospects that investigations of these systems hold for understanding the conditions that may have led to the first appearance of life. The discovery of diverse and unusual Antarctic hydrothermal vent ecosystems provides opportunities for new understanding in these fields. Moreover, the Antarctic vents south of 60°S benefit from automatic conservation under the Convention on the Conservation of Antarctic Marine Living Resources and the Antarctic Treaty. Other deep-sea hydrothermal vents located in international waters are not protected and may be threatened by growing interests in deep-sea mining.

  11. Shackleton: His Antarctic Writings

    Science.gov (United States)

    Dalrymple, Paul C.

    Two books entitled “Shackleton” were published in the United Kingdom in recent years. The one entitled Shackleton: His Antarctic Writings, Selected and Introduced by Christopher Ralling was published by the British Broadcasting Corporation (BBC) in 1983; the other, by Roland Huntford and simply entitled Shackleton, was published by Hodder and Stoughton (London) in November 1985. The only two things that these books have in common are their title and home publication base: The BBC book is essentially excerpts from two well-known books written by Shackleton, with a strong assist from a New Zealand reporter, Edward Saunders (who served as Shackleton's amanuensis), whereas Huntford's book is an outstanding polar biography.

  12. Construction of plateaued functions satisfying multiple criteria

    Institute of Scientific and Technical Information of China (English)

    Zhang Weiguo

    2005-01-01

    A class of plateaued functions has been got by using the Maiorana-McFarland construction. A variety of desirable criteria for functions with cryptographic application could be satisfied: balancedness, high nonlinearity, correlation immunity of reasonably high order, strict avalanche criterion, non-existence of non-zero linear structures, good global avalanche characteristics, etc.

  13. Unveiling the Antarctic subglacial landscape.

    Science.gov (United States)

    Warner, Roland; Roberts, Jason

    2010-05-01

    Better knowledge of the subglacial landscape of Antarctica is vital to reducing uncertainties regarding prediction of the evolution of the ice sheet. These uncertainties are associated with bedrock geometry for ice sheet dynamics, including possible marine ice sheet instabilities and subglacial hydrological pathways (e.g. Wright et al., 2008). Major collaborative aerogeophysics surveys motivated by the International Polar Year (e.g. ICECAP and AGAP), and continuing large scale radar echo sounding campaigns (ICECAP and NASA Ice Bridge) are significantly improving the coverage. However, the vast size of Antarctica and logistic difficulties mean that data gaps persist, and ice thickness data remains spatially inhomogeneous. The physics governing large scale ice sheet flow enables ice thickness, and hence bedrock topography, to be inferred from knowledge of ice sheet surface topography and considerations of ice sheet mass balance, even in areas with sparse ice thickness measurements (Warner and Budd, 2000). We have developed a robust physically motivated interpolation scheme, based on these methods, and used it to generate a comprehensive map of Antarctic bedrock topography, using along-track ice thickness data assembled for the BEDMAP project (Lythe et al., 2001). This approach reduces ice thickness biases, compared to traditional inverse distance interpolation schemes which ignore the information available from considerations of ice sheet flow. In addition, the use of improved balance fluxes, calculated using a Lagrangian scheme, eliminates the grid orientation biases in ice fluxes associated with finite difference methods (Budd and Warner, 1996, Le Brocq et al., 2006). The present map was generated using a recent surface DEM (Bamber et al., 2009, Griggs and Bamber, 2009) and accumulation distribution (van de Berg et al., 2006). Comparing our results with recent high resolution regional surveys gives confidence that all major subglacial topographic features are

  14. Geospatial mapping of Antarctic coastal oasis using geographic object-based image analysis and high resolution satellite imagery

    Science.gov (United States)

    Jawak, Shridhar D.; Luis, Alvarinho J.

    2016-04-01

    An accurate spatial mapping and characterization of land cover features in cryospheric regions is an essential procedure for many geoscientific studies. A novel semi-automated method was devised by coupling spectral index ratios (SIRs) and geographic object-based image analysis (OBIA) to extract cryospheric geospatial information from very high resolution WorldView 2 (WV-2) satellite imagery. The present study addresses development of multiple rule sets for OBIA-based classification of WV-2 imagery to accurately extract land cover features in the Larsemann Hills, east Antarctica. Multilevel segmentation process was applied to WV-2 image to generate different sizes of geographic image objects corresponding to various land cover features with respect to scale parameter. Several SIRs were applied to geographic objects at different segmentation levels to classify land mass, man-made features, snow/ice, and water bodies. We focus on water body class to identify water areas at the image level, considering their uneven appearance on landmass and ice. The results illustrated that synergetic usage of SIRs and OBIA can provide accurate means to identify land cover classes with an overall classification accuracy of ≍97%. In conclusion, our results suggest that OBIA is a powerful tool for carrying out automatic and semiautomatic analysis for most cryospheric remote-sensing applications, and the synergetic coupling with pixel-based SIRs is found to be a superior method for mining geospatial information.

  15. Institute of Tibetan Plateau Research

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ The Tibetan Plateau (Qinghai-Xizang Plateau)is a unique geological-geographical unit on Earth, an ideal region for studies into the formation and evolution of the lithosphere and the dynamic mechanism of the earth crust. The uplifting of the Plateau exerts profound influence upon the evolution and differentiation of the natural environment of the plateau itself, its adjacent regions and the Northern Hemisphere. As a unique natural geographical unit, the Plateau holds a special status in the whole globe due to its special natural environment and ecosystems, which is also in close relation to global environmental change.The significance of the Plateau research should be recognized not only in the fundamental research fields of geo-sciences and biology, but also in its application to resource exploitation, environmental protection and sustainable development of the Plateau region.

  16. SPECTROSCOPIC OBSERVATIONS OF SN 2012fr: A LUMINOUS, NORMAL TYPE Ia SUPERNOVA WITH EARLY HIGH-VELOCITY FEATURES AND A LATE VELOCITY PLATEAU

    Energy Technology Data Exchange (ETDEWEB)

    Childress, M. J.; Scalzo, R. A.; Sim, S. A.; Tucker, B. E.; Yuan, F.; Schmidt, B. P. [Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia); Cenko, S. B.; Filippenko, A. V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Silverman, J. M. [Department of Astronomy, University of Texas, Austin, TX 78712-0259 (United States); Contreras, C.; Hsiao, E. Y.; Phillips, M.; Morrell, N. [Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena (Chile); Jha, S. W.; McCully, C. [Department of Physics and Astronomy, Rutgers, State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Anderson, J. P.; De Jaeger, T.; Forster, F. [Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago (Chile); Benetti, S. [INAF Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Bufano, F., E-mail: mjc@mso.anu.edu.au [Departamento de Ciencias Fisicas, Universidad Andres Bello, Avda. Republica 252, Santiago (Chile); and others

    2013-06-10

    We present 65 optical spectra of the Type Ia SN 2012fr, 33 of which were obtained before maximum light. At early times, SN 2012fr shows clear evidence of a high-velocity feature (HVF) in the Si II {lambda}6355 line that can be cleanly decoupled from the lower velocity ''photospheric'' component. This Si II {lambda}6355 HVF fades by phase -5; subsequently, the photospheric component exhibits a very narrow velocity width and remains at a nearly constant velocity of {approx}12,000 km s{sup -1} until at least five weeks after maximum brightness. The Ca II infrared triplet exhibits similar evidence for both a photospheric component at v Almost-Equal-To 12,000 km s{sup -1} with narrow line width and long velocity plateau, as well as an HVF beginning at v Almost-Equal-To 31,000 km s{sup -1} two weeks before maximum. SN 2012fr resides on the border between the ''shallow silicon'' and ''core-normal'' subclasses in the Branch et al. classification scheme, and on the border between normal and high-velocity Type Ia supernovae (SNe Ia) in the Wang et al. system. Though it is a clear member of the ''low velocity gradient'' group of SNe Ia and exhibits a very slow light-curve decline, it shows key dissimilarities with the overluminous SN 1991T or SN 1999aa subclasses of SNe Ia. SN 2012fr represents a well-observed SN Ia at the luminous end of the normal SN Ia distribution and a key transitional event between nominal spectroscopic subclasses of SNe Ia.

  17. Selected organochlorine pesticides and polychlorinated biphenyls in atmosphere at Ruoergai high altitude prairie in eastern edge of Qinghai-Tibet Plateau and their source identifications

    Science.gov (United States)

    Gai, Nan; Pan, Jing; Tang, Hua; Tan, Ke-Yan; Chen, Da-Zhou; Zhu, Xiao-Hua; Lu, Guo-Hui; Chen, Shu; Huang, Yi; Yang, Yong-Liang

    2014-10-01

    Compared to the low-altitude areas, high-altitude regions have low air temperature and relatively high snow precipitation. These climatological characteristics will affect the environmental behavior of persistent organic pollutants (POPs) in such a special geographical environment, leading to cold-trapping of certain POPs in these areas. Ruoergai highland prairie in the eastern edge of the Qinghai-Tibetan Plateau was selected to study the distribution characteristics of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in aerosols and gas phase samples collected in two seasons of 2011 and measured by isotope dilution-HRGC/HRMS method. OCPs and PCBs in the Ruoergai air were at low levels compared with the adjacent populated areas such as Lanzhou and Chengdu. Higher concentrations of POPs in aerosol and gas phase were observed in winter than in summer, showing the impact of monsoon on the transport of POPs to this region. Northwesterly winds in winter may transport OCPs and PCBs from industrial and agricultural areas in the northwestern China. HCB, α-HCH, and PCB 28 were the predominant compounds found in the air. Soil to air fugacity ratios show that Ruoergai soils behave as a secondary source of the relatively volatile compounds (HCHs, α-endosulfan, PCB 28 and 52) to the atmosphere during summer and behave as a sink of atmospheric DDTs due to the OC-rich soils as well as lower temperatures. Similar 206Pb/207Pb and 208Pb/207Pb ratios in Ruoergai aerosols to those of aerosols of Lanzhou and ores in Qinghai, Xinjiang, Kazakhstan, and Russia may indicate that the aerosol sources were mainly related to air mass passing over the neighboring regions and countries.

  18. Antarctic Cosmic Ray Astronomy

    Science.gov (United States)

    Duldig, Marc

    Cosmic ray observations related to Antarctica commenced in the austral summer of 1947-48 from sub-Antarctic Heard and Macquarie Islands and from the HMAS Wyatt Earp. Muon telescope observations from Mawson station Antarctica commenced in 1955. The International Geophysical Year was the impetus for the installation of a number of neutron monitors around Antarctica observing the lowest energy cosmic rays accessible by ground based instruments. In 1971 a new observatory was built at Mawson including the only underground muon telescope system at polar latitudes in either hemisphere. In the 1980s the South Pole Air Shower Experiment (SPASE) opened the highest energy cosmic ray window over Antarctica and this was followed by the in-ice neutrino experiment AMANDA. Over more than half a century cosmic ray astronomy has been undertaken from Antarctica and its surrounding regions and these observations have been critical to our growing understanding of nearby astrophysical structures. For example the Parker spiral magnetic field of the sun was confirmed through Mawson observations of a Solar flare induced Ground Level Enahncement in 1960 long before spacecraft were able to directly observe the interplanetary magnetic field. A summary of the Antarctic instrumental developments and the scientific advances that resulted will be presented.

  19. Transcriptomics and comparative analysis of three antarctic notothenioid fishes.

    Directory of Open Access Journals (Sweden)

    Seung Chul Shin

    Full Text Available For the past 10 to 13 million years, Antarctic notothenioid fish have undergone extraordinary periods of evolution and have adapted to a cold and highly oxygenated Antarctic marine environment. While these species are considered an attractive model with which to study physiology and evolutionary adaptation, they are poorly characterized at the molecular level, and sequence information is lacking. The transcriptomes of the Antarctic fishes Notothenia coriiceps, Chaenocephalus aceratus, and Pleuragramma antarcticum were obtained by 454 FLX Titanium sequencing of a normalized cDNA library. More than 1,900,000 reads were assembled in a total of 71,539 contigs. Overall, 40% of the contigs were annotated based on similarity to known protein or nucleotide sequences, and more than 50% of the predicted transcripts were validated as full-length or putative full-length cDNAs. These three Antarctic fishes shared 663 genes expressed in the brain and 1,557 genes expressed in the liver. In addition, these cold-adapted fish expressed more Ub-conjugated proteins compared to temperate fish; Ub-conjugated proteins are involved in maintaining proteins in their native state in the cold and thermally stable Antarctic environments. Our transcriptome analysis of Antarctic notothenioid fish provides an archive for future studies in molecular mechanisms of fundamental genetic questions, and can be used in evolution studies comparing other fish.

  20. Plateau-insulator transition in graphene

    Energy Technology Data Exchange (ETDEWEB)

    Amado, M; Diez, E; Caridad, J M [Laboratorio de Bajas Temperaturas, Universidad de Salamanca, E-37008 Salamanca (Spain); Lopez-Romero, D [CT-ISOM, Universidad Politecnica de Madrid, E-28040 Madrid (Spain); Rossella, F; Dionigi, F; Bellani, V [Dipartimento di Fisica ' A Volta' and CNISM, Universita degli studi di Pavia, I-27100 Pavia (Italy); Maude, D K, E-mail: marioam@fis.ucm.e [Laboratoire National des Champs Magnetiques Intenses, F-38042 Grenoble (France)

    2010-05-15

    We investigate the quantum Hall effect (QHE) in a graphene sample with Hall-bar geometry close to the Dirac point at high magnetic fields up to 28 T. We have discovered a plateau-insulator quantum phase transition passing from the last plateau for the integer QHE in graphene to an insulator regime {nu}=-2{yields}{nu}=0. The analysis of the temperature dependence of the longitudinal resistance gives a value for the critical exponent associated with the transition equal to {kappa}=0.58{+-}0.03.

  1. Southern high-latitude terrestrial climate change during the Palaeocene-Eocene derived from a marine pollen record (ODP Site 1172, East Tasman Plateau)

    Science.gov (United States)

    Contreras, L.; Pross, J.; Bijl, P. K.; O'Hara, R. B.; Raine, J. I.; Sluijs, A.; Brinkhuis, H.

    2014-07-01

    Reconstructing the early Palaeogene climate dynamics of terrestrial settings in the high southern latitudes is important to assess the role of high-latitude physical and biogeochemical processes in the global climate system. However, whereas a number of high-quality Palaeogene climate records has become available for the marine realm of the high southern latitudes over the recent past, the long-term evolution of coeval terrestrial climates and ecosystems is yet poorly known. We here explore the climate and vegetation dynamics on Tasmania from the middle Palaeocene to the early Eocene (60.7-54.2 Ma) based on a sporomorph record from Ocean Drilling Program (ODP) Site 1172 on the East Tasman Plateau. Our results show that three distinctly different vegetation types thrived on Tasmania under a high-precipitation regime during the middle Palaeocene to early Eocene, with each type representing different temperature conditions: (i) warm-temperate forests dominated by gymnosperms that were dominant during the middle and late Palaeocene (excluding the middle/late Palaeocene transition); (ii) cool-temperate forests dominated by southern beech (Nothofagus) and araucarians that transiently prevailed across the middle/late Palaeocene transition interval (~ 59.5 to ~ 59.0 Ma); and (iii) paratropical forests rich in ferns that were established during and in the wake of the Palaeocene-Eocene Thermal Maximum (PETM). The transient establishment of cool-temperate forests lacking any frost-sensitive elements (i.e. palms and cycads) across the middle/late Palaeocene transition interval indicates markedly cooler conditions, with the occurrence of frosts in winter, on Tasmania during that time. The integration of our sporomorph data with previously published TEX86-based sea-surface temperatures from ODP Site 1172 documents that the vegetation dynamics on Tasmania were closely linked with the temperature evolution in the Tasman sector of the Southwest Pacific region. Moreover, the

  2. Southern high-latitude terrestrial climate change during the Paleocene-Eocene derived from a marine pollen record (ODP Site 1172, East Tasman Plateau)

    Science.gov (United States)

    Contreras, L.; Pross, J.; Bijl, P. K.; O'Hara, R. B.; Raine, J. I.; Sluijs, A.; Brinkhuis, H.

    2014-01-01

    Reconstructing the early Paleogene climate dynamics of terrestrial settings in the high southern latitudes is important to assess the role of high-latitude physical and biogeochemical processes in the global climate system. However, whereas a number of high-quality Paleogene climate records has become available for the marine realm of the high southern latitudes over the recent past, the long-term evolution of coeval terrestrial climates and ecosystems is yet poorly known. We here explore the climate and vegetation dynamics on Tasmania from the middle Paleocene to the early Eocene (60.7-54.2 Ma) based on a sporomorph record from Ocean Drilling Program (ODP) Site 1172 on the East Tasman Plateau. Our results show that three distinctly different vegetation types thrived on Tasmania under a high-precipitation regime during the middle Paleocene to early Eocene, with each type representing different temperature conditions: (i) warm-temperate forests dominated by gymnosperms that were dominant during the middle and late Paleocene; (ii) cool-temperate forests dominated by southern beech (Nothofagus) and araucarians across the middle/late Paleocene transition interval (~59.5 to ~59.0 Ma); and (iii) paratropical forests rich in ferns that were established during and in the wake of the Paleocene-Eocene Thermal Maximum (PETM). The transient establishment of cool-temperate forests lacking any frost-sensitive elements (i.e., palms and cycads) across the middle/late Paleocene transition interval indicates markedly cooler conditions, with the occurrence of frosts in winter, on Tasmania during that time. The integration of our sporomorph data with previously published TEX86-based sea-surface temperatures from ODP Site 1172 documents that the vegetation dynamics on Tasmania were closely linked with the temperature evolution in the Tasman sector of the Southwest Pacific region. Moreover, the comparison of our season-specific climate estimates for the sporomorph assemblages from ODP

  3. Southern high-latitude terrestrial climate change during the Paleocene–Eocene derived from a marine pollen record (ODP Site 1172, East Tasman Plateau

    Directory of Open Access Journals (Sweden)

    L. Contreras

    2014-01-01

    Full Text Available Reconstructing the early Paleogene climate dynamics of terrestrial settings in the high southern latitudes is important to assess the role of high-latitude physical and biogeochemical processes in the global climate system. However, whereas a number of high-quality Paleogene climate records has become available for the marine realm of the high southern latitudes over the recent past, the long-term evolution of coeval terrestrial climates and ecosystems is yet poorly known. We here explore the climate and vegetation dynamics on Tasmania from the middle Paleocene to the early Eocene (60.7–54.2 Ma based on a sporomorph record from Ocean Drilling Program (ODP Site 1172 on the East Tasman Plateau. Our results show that three distinctly different vegetation types thrived on Tasmania under a high-precipitation regime during the middle Paleocene to early Eocene, with each type representing different temperature conditions: (i warm-temperate forests dominated by gymnosperms that were dominant during the middle and late Paleocene; (ii cool-temperate forests dominated by southern beech (Nothofagus and araucarians across the middle/late Paleocene transition interval (~59.5 to ~59.0 Ma; and (iii paratropical forests rich in ferns that were established during and in the wake of the Paleocene–Eocene Thermal Maximum (PETM. The transient establishment of cool-temperate forests lacking any frost-sensitive elements (i.e., palms and cycads across the middle/late Paleocene transition interval indicates markedly cooler conditions, with the occurrence of frosts in winter, on Tasmania during that time. The integration of our sporomorph data with previously published TEX86-based sea-surface temperatures from ODP Site 1172 documents that the vegetation dynamics on Tasmania were closely linked with the temperature evolution in the Tasman sector of the Southwest Pacific region. Moreover, the comparison of our season-specific climate estimates for the sporomorph

  4. Metazoan Parasites of Antarctic Fishes.

    Science.gov (United States)

    Oğuz, Mehmet Cemal; Tepe, Yahya; Belk, Mark C; Heckmann, Richard A; Aslan, Burçak; Gürgen, Meryem; Bray, Rodney A; Akgül, Ülker

    2015-06-01

    To date, there have been nearly 100 papers published on metazoan parasites of Antarctic fishes, but there has not yet been any compilation of a species list of fish parasites for this large geographic area. Herein, we provide a list of all documented occurrences of monogenean, cestode, digenean, acanthocephalan, nematode, and hirudinean parasites of Antarctic fishes. The list includes nearly 250 parasite species found in 142 species of host fishes. It is likely that there are more species of fish parasites, which are yet to be documented from Antarctic waters.

  5. Effect of a cold, dry air incursion on atmospheric boundary layer processes over a high-altitude lake in the Tibetan Plateau

    Science.gov (United States)

    Li, Zhaoguo; Lyu, Shihua; Wen, Lijuan; Zhao, Lin; Ao, Yinhuan; Wang, Shaoying

    2017-03-01

    High-altitude lakes are frequently exposed to extreme meteorological conditions, but the surface and atmospheric boundary layer (ABL) processes have received little attention under specific weather conditions. This study used the multi-source field data, re-analysis and remote sensing data to investigate the varying patterns and driving forces of the convective boundary layer (CBL) height over Ngoring Lake in the Tibetan Plateau (TP) before and after the cold air incursion. Daily cumulative surface heat flux and buoyancy flux over the land were markedly larger than those over the lake on a clear summer day, but an opposite pattern was observed accompanied by the cold air incursion. CBLs determined by the potential temperature thinned (depth < 100 m) over the lake in the daytime and thickened (400-600 m) at night on a clear day. Along with the arrival of the cold air, CBL rapidly thickened to 2280 m over the lake, exceeded than the maximum value at adjacent Madoi station. Cold air dramatically cooled the middle-upper atmosphere but the temperature of the lower atmosphere cooled down slowly, partly due to a sharp increase of sensible heat flux over the lake, both of which linked up to weaken the potential temperature gradient. Moreover, increasing wind speed and vertical wind shear further facilitated the buoyancy flux to exert higher heat convection efficiency. All of these factors acted together to cause the rapid growth of CBL over the lake. This investigation provided a more in-depth knowledge of boundary layer dynamics in the lake-rich region of the TP.

  6. From sea level to high elevation in 15 million years: Uplift history of the northern Tibetan Plateau margin in the Altun Shan

    NARCIS (Netherlands)

    Ritts, B.D.; Yue, Y.; Graham, S.A.; Sobel, E.R.; Abbink, O.A.; Stockli, D.

    2008-01-01

    Approximately 1300 in of Oligocene-Miocene clastic strata are exposed along the Miran River in the southeastern Tarim basin, where the adjacent Altun Shan form the topographic escarpment of the northern Tibetan Plateau. The sedimentary section is faulted against Proterozoic rocks of the Altun Shan i

  7. EVA: Evryscopes for the Arctic and Antarctic

    Science.gov (United States)

    Richichi, A.; Law, N.; Tasuya, O.; Fors, O.; Dennihy, E.; Carlberg, R.; Tuthill, P.; Ashley, M.; Soonthornthum, B.

    2017-06-01

    We are planning to build Evryscopes for the Arctic and Antarctic (EVA), which will enable the first ultra-wide-field, high-cadence sky survey to be conducted from both Poles. The system is based on the successful Evryscope concept, already installed and operating since 2015 at Cerro Tololo in Chile with the following characteristics: robotic operation, 8,000 square degrees simultaneous sky coverage, 2-minute cadence, milli-mag level photometric accuracy, pipelined data processing for real-time analysis and full data storage for off-line analysis. The initial location proposed for EVA is the PEARL station on Ellesmere island; later also an antarctic location shall be selected. The science goals enabled by this unique combination of almost full-sky coverage and high temporal cadence are numerous, and include among others ground-breaking forays in the fields of exoplanets, stellar variability, asteroseismology, supernovae and other transient events. The EVA polar locations will enable uninterrupted observations lasting in principle over weeks and months. EVA will be fully robotic. We discuss the EVA science drivers and expected results, and present the logistics and the outline of the project which is expected to have first light in the winter of 2018. The cost envelope can be kept very competitive thanks to R&D already employed for the CTIO Evryscope, to our experience with both Arctic and Antarctic locations, and to the use of off-the-shelf components.

  8. Water mass distribution in Fram Strait and over the Yermak Plateau in summer 1997

    Directory of Open Access Journals (Sweden)

    B. Rudels

    Full Text Available The water mass distribution in northern Fram Strait and over the Yermak Plateau in summer 1997 is described using CTD data from two cruises in the area. The West Spitsbergen Current was found to split, one part recirculated towards the west, while the other part, on entering the Arctic Ocean separated into two branches. The main inflow of Atlantic Water followed the Svalbard continental slope eastward, while a second, narrower, branch stayed west and north of the Yermak Plateau. The water column above the southeastern flank of the Yermak Plateau was distinctly colder and less saline than the two inflow branches. Immediately west of the outer inflow branch comparatively high temperatures in the Atlantic Layer suggested that a part of the extraordinarily warm Atlantic Water, observed in the boundary current in the Eurasian Basin in the early 1990s, was now returning, within the Eurasian Basin, toward Fram Strait. The upper layer west of the Yermak Plateau was cold, deep and comparably saline, similar to what has recently been observed in the interior Eurasian Basin. Closer to the Greenland continental slope the salinity of the upper layer became much lower, and the temperature maximum of the Atlantic Layer was occasionally below 
    0.5 °C, indicating water masses mainly derived from the Canadian Basin. This implies that the warm pulse of Atlantic Water had not yet made a complete circuit around the Arctic Ocean. The Atlantic Water of the West Spitsbergen Current recirculating within the strait did not extend as far towards Greenland as in the 1980s, leaving a broader passage for waters from the Atlantic and intermediate layers, exiting the Arctic Ocean. A possible interpretation is that the circulation pattern alternates between a strong recirculation of the West Spitsbergen Current in the strait, and a larger exchange of Atlantic Water between the Nordic Seas and the inner parts of the Arctic Ocean.

    Key words: Oceanography: general

  9. CELSS Antarctic Analog Project (CAAP): A New Paradigm for Polar Life Support and CELSS Research

    Science.gov (United States)

    Bubenheim, David L.; Straight, Christian; Flynn, Michael; Bates, Maynard; Harper, Lynn D. (Technical Monitor)

    1994-01-01

    The CELSS Antarctic Analog Project (CAAP) is a joint National Science Foundation (NSF) and National Aeronautics and Space Administration (NASA) project for the development, deployment and operation of CELSS technologies at the Amundsen-Scott South Pole Station. CAAP is implemented through the joint NSF/NASA Antarctic Space Analog Program (ASAP), initiated to support the pursuit of future NASA missions and to promote the transfer of space technologies to the NSF. Under a Memorandum of Agreement, the CAAP represents an example of a working dual agency cooperative project. NASA goals are operational testing of CELSS technologies and the conduct of scientific study to facilitate . technology selection, system design and methods development, including human dynamics as required for the operation of a CELSS. Although not fully closed, food production, water purification, and waste recycle and reduction provided by CAAP will improve the quality of life for the South Pole inhabitants, reduce logistics dependence, and minimize environmental impacts associated with human presence on the polar plateau. The CAAP facility will be highly integrated with the new South Pole Station infrastructure and will be composed of a deployed hardware facility and a research activity. This paper will include a description of CAAP and its functionality, conceptual designs, component selection and sizing for the crop growth chamber, crop production expectations, and a brief report on an initial on-site visit. This paper will also provide a discussion of issues associated with power and energy use and the applicability of CAAP to direct technology transfer to society in general and remote communities in particular.

  10. Peopling the Tibetan plateau: insights from archaeology.

    Science.gov (United States)

    Aldenderfer, Mark

    2011-01-01

    Recent studies of the genome of modern Tibetans have revealed the existence of genes thought to provide an adaptive advantage for life at high elevation. Extrapolating from this discovery, some researchers now argue that a Tibetan-Han split occurred no more than 2750 yr ago. This date is implausible, and in this paper I review the archaeological data from the Tibetan plateau as one means by which to examine the veracity of this assertion. Following a review of the general state of knowledge of Tibetan prehistory, which is unfortunately only at its beginnings, I first examine the data that speak to the initial peopling of the plateau and assess the evidence that traces of their presence can be seen in modern Tibetans today. Although the data are sparse, both archaeology and genetics suggest that the plateau was occupied in the Late Pleistocene, perhaps as early as 30,000 yr ago, and that these early peoples have left a genetic signature in modern Tibetans. I then turn to the evidence for later migrations and focus on the question of the timing of the establishment of permanent settled villages on the plateau. Three areas of the plateau-northeastern Qinghai, extreme eastern Tibet, and the Yarlung Tsangpo valley-have evidence of permanent settlements dating from ca. 6500, 5900, and 3750 yr ago, respectively. These data are not consonant with the 2750 yr ago date for the split and suggest at a minimum that the plateau has been occupied substantially longer and, further, that multiple migrations at different times and from different places have created a complex mosaic of population history. © Mary Ann Liebert, Inc.

  11. OPTIMAL SURGICAL MANAGEMENT OF HIGH VELOCITY POSTERIOR TIBIAL PLATEAU FRACTURE SUBLUXATIONS (DUPARC, REVISED CLASSIFICATION, GROUP – V: POSTERO - MEDIAL FRACTURE BY DIRECT, DORSAL APPROACH – A CHANGING TREND: A PROSPECTIVE STUDY

    Directory of Open Access Journals (Sweden)

    Pardhasaradhi

    2015-10-01

    Full Text Available INTRODUCTION : High - energy tibial plateau fractures are infrequent and technically demanding to treat especially if those are shearing type, coronal plane, displaced fractures. The most widely used the Schatzker system of classification , [1] ( B ased on the AP radiograph is more than likely to miss postero - medial and postero - lateral shear fractures, best visible on the lateral, than the AP radiograph. These fractures have recently been characterised by two studies, highlighti ng their clinical relevance [ 2,3] and showing that less invasive surgery and indirect reduction techniques are often inadequate. Hohl described unicondylar c oronal plane splitting fractures of the medial tibial plateau, noted that these injuries be considered as fracture - dislocations. Connolly and others have suggested that the mechanism involved in this fracture pattern is one of knee flexion, varus, and inter nal rotation of the medial femoral condyle . [4,5,6 ] Consistent among these and other authors is that the occurrence of this fragment is relatively unusual and that the use of a posteriorly based exposure with direct fracture visualization, anatomic reductio n and absolute stability appears to result in satisfactory outcomes. Though variations of a postero - medial approach been previously described ( by Trickey et al and also by Burks et al.,, more recently, Lobenhoffer et al described direct posterior exposure , Wang et al described postero - medial approach and Luo et al. described the approach for the management of posterior bicondylar tibial plateau fractures . [7,8] These approaches have been used in isolation or as a dual - incision approach for treating tibial plateau fractures . [9,10,11,12,13,14, 15] PURPOSE : The purpose of this study is to describe this unfamiliar direct posterior surgical (Medial Gastrocnemius approach to a general orthopod, highlighting the relevant anatomy and presenting our experience using this approach in treating a

  12. NUMERICAL STUDY ON INFLUENCE OF QINGHAI-XIZANG (TIBETAN) PLATEAU ON SEASONAL TRANSITION OF GLOBAL ATMOSPHERIC CIRCULATION

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    It is a worthwhile attempt to address the role of the Qinghai-Xizang Plateau in the seasonal transition of general circulation from a global prospective. In this paper, the CCM1 (R15L7) - LNWP spectral model is used to study the influences of the Qinghai-Xizang Plateau on the seasonal transfer of the general circulation, with the objective analysis form the State Meteorological Center for March 17, 1996 as the initial field. A mid-level heating source in regions on the same latitudes is shown to cause a warming center of 224 K to form on the level of 200 hPa that warms up the atmosphere by more than 7 K and a drop of temperature by about 6 K on most of the 200-hPa layer over the Antarctic continent, with the largest negative center being -8.28 K. It is favorable to the deepening and widening of the polar vortexes in the course of transition from summer to winter. The topographic effect of the plateau plays a vital role in forming and maintaining the mean troughs and ridges of the atmospheric circulation in Northern Hemisphere such that it strengthens (weakens) the south-north positive gradient of temperature on the northern (southern) side of the latitude zone in which the plateau sits and increases the north-south gradient of temperature near 30° N. The seasonal transition is thus favored so that the bulk travel of global westerly at the middle latitudes and the formation of Asian monsoon in early summer are made possible. In the equatorial and low-latitude areas where the geopotential is increased, the effect of the plateau terrain is also evident in that it is favorable for the northern withdrawal of the tropical high ridge in Southern Hemisphere and the northern shift of the subtropical high in Northern Hemisphere. In addition, the effect also helps increase the polar easterly over the Southern Hemisphere and weaken the low zone at 500 hPa. It acts as an increasing factor for the polar vortex around the Ross Sea and contributes to the genesis of the Somali Jet

  13. Antarctic crabs: invasion or endurance?

    Science.gov (United States)

    Griffiths, Huw J; Whittle, Rowan J; Roberts, Stephen J; Belchier, Mark; Linse, Katrin

    2013-01-01

    Recent scientific interest following the "discovery" of lithodid crabs around Antarctica has centred on a hypothesis that these crabs might be poised to invade the Antarctic shelf if the recent warming trend continues, potentially decimating its native fauna. This "invasion hypothesis" suggests that decapod crabs were driven out of Antarctica 40-15 million years ago and are only now returning as "warm" enough habitats become available. The hypothesis is based on a geographically and spatially poor fossil record of a different group of crabs (Brachyura), and examination of relatively few Recent lithodid samples from the Antarctic slope. In this paper, we examine the existing lithodid fossil record and present the distribution and biogeographic patterns derived from over 16,000 records of Recent Southern Hemisphere crabs and lobsters. Globally, the lithodid fossil record consists of only two known specimens, neither of which comes from the Antarctic. Recent records show that 22 species of crabs and lobsters have been reported from the Southern Ocean, with 12 species found south of 60 °S. All are restricted to waters warmer than 0 °C, with their Antarctic distribution limited to the areas of seafloor dominated by Circumpolar Deep Water (CDW). Currently, CDW extends further and shallower onto the West Antarctic shelf than the known distribution ranges of most lithodid species examined. Geological evidence suggests that West Antarctic shelf could have been available for colonisation during the last 9,000 years. Distribution patterns, species richness, and levels of endemism all suggest that, rather than becoming extinct and recently re-invading from outside Antarctica, the lithodid crabs have likely persisted, and even radiated, on or near to Antarctic slope. We conclude there is no evidence for a modern-day "crab invasion". We recommend a repeated targeted lithodid sampling program along the West Antarctic shelf to fully test the validity of the "invasion hypothesis".

  14. Soil formation in high elevation and permafrost areas in the Qinghai Plateau (China Edafogénesis en zonas elevadas y con permafrost en el Plateau Qunghai (China Formação do solo em áreas de elevada altitude e em ambientes"permafrost" do planalto de Qinghai Plateau (China

    Directory of Open Access Journals (Sweden)

    Joselito Arocena

    2012-07-01

    Full Text Available

    Soil systems continuously gain and lose matter and energy even in areas where climate is too harsh to support the higher plants such as in high elevations and in permafrost environments. The purpose of this paper was to elucidate soil formation at 4 700 m asl in the Kunlun Mountains of the Qinghai (Tibet Plateau, China. We collected twenty-six samples from three pedons developed on carbonate-rich slate and quartzitic-sandstone materials. The samples were analyzed for routine physical, chemical and mineralogical properties. Our results indicate that soil-forming processes are barely taking place in the study site as shown by pH > 7.0 reflecting limited decarbonation, biological activity (< 1.0% total C and < 0.05% total N, podzolization (<1 g Fep+Alp kg-1 soil and lessivage. The relative amounts of mica and kaolinite show no apparent change with depth suggesting minimal transformation and translocation of phyllosilicates. The most noticeable mineral transformation resulted in micaceous “flakes” and feldspathic “fragments” possibly due to thermal stress. Calcite is also observed coating the slate fragments. The soils are classified as Cryosols in the World Reference Base system and Gelisols in the Soil Taxonomy with ochric epipedon as the only diagnostic horizon indicating recent development of soils due to cold and arid environment. The results of this study show that soil-forming processes in harsh environments are manifested in the mechanical breakdown of minerals such as mica and feldspars.

    Los sistemas edáficos ganan y pierden continuamente materia y energía incluso en zonas donde el clima es demasiado severo como para permitir el desarrollo de plantas superiores, como son las zonas de elevada altitud o los ambientes con permafrost. El objetivo de este trabajo es analizar la formación del suelo a una altitud de 4 700 m en las Monta

  15. The circum-Antarctic sedimentary record; a dowsing rod for Antarctic ice in the Eocene

    Science.gov (United States)

    Scher, H.

    2012-12-01

    Arguments for short-lived Antarctic glacial events during the Eocene (55-34 Ma) are compelling, however the paleoceanographic proxy records upon which these arguments are based (e.g., benthic δ18O, eustatic sea level, deep sea carbonate deposition) are global signals in which the role of Antarctic ice volume variability is ambiguous. That is to say, the proxy response to ice volume may be masked other processes. As a result broad correlations between proxies for ice volume are lacking during suspected Eocene glacial events. I will present a more direct approach for detecting Antarctic ice sheets in the Eocene; utilizing provenance information derived from the radiogenic isotopic composition of the terrigenous component of marine sediments near Antarctica. The method relies on knowledge that marine sediments represent a mixture derived from different basement terrains with different isotopic fingerprints. A key issue when using sedimentary deposits to characterize continental sediment sources is to deconvolve different sources from the mixed signal of the bulk sample. The pioneering work of Roy et al. (2007) and van de Flierdt et al. (2007) represents a major advance in Antarctic provenance studies. It is now known that the isotopic composition of neodymium (Nd) and hafnium (Hf) in modern circum-Antarctic sediments are distributed in a pattern that mimics the basement age of sediment sources around Antarctica. For this study I selected two Ocean Drilling Program (ODP) sites on southern Kerguelen Plateau (ODP Sites 738 and 748) because of their proximity to Prydz Bay, where Precambrian sediment sources contribute to extremely nonradiogenic isotopic signatures in modern sediments in the Prydz Bay region. New detrital Nd isotope records from these sediment cores reveal an Nd isotope excursion at the Bartonian/Priabonian boundary (ca. 37 Ma) that coincides with a 0.5 ‰ increase in benthic foram δ18O values. Detrital sediment ɛNd values are around -12 in intervals

  16. Wet precipitation chemistry at a high-altitude site (3,326 m a.s.l.) in the southeastern Tibetan Plateau.

    Science.gov (United States)

    Liu, Bin; Kang, Shichang; Sun, Jimin; Zhang, Yulan; Xu, Ri; Wang, Yongjie; Liu, Yongwen; Cong, Zhiyuan

    2013-07-01

    This paper presents the results of wet precipitation chemistry from September 2009 to August 2010 at a high-altitude forest site in the southeastern Tibetan Plateau (TP). The alkaline wet precipitation, with pH ranging from 6.25 to 9.27, was attributed to the neutralization of dust in the atmosphere. Wet deposition levels of major ions and trace elements were generally comparable with other alpine and remote sites around the world. However, the apparently greater contents/fluxes of trace elements (V, Co, Ni, Cu, Zn, and Cd), compared to those in central and southern TP and pristine sites of the world, reflected potential anthropogenic disturbances. The almost equal mole concentrations and perfect linear relationships of Na(+) and Cl(-) suggested significant sea-salts sources, and was confirmed by calculating diverse sources. Crust mineral dust was responsible for a minor fraction of the chemical components (less than 15%) except Al and Fe, while most species (without Na(+), Cl(-), Mg(2+), Al, and Fe) arose mainly from anthropogenic activities. High values of as-K(+) (anthropogenic sources potassium), as-SO4(2-), and as-NO3(-) observed in winter and spring demonstrated the great effects of biomass burning and fossil fuel combustion in these seasons, which coincided with haze layer outburst in South Asia. Atmospheric circulation exerted significant influences on the chemical components in wet deposition. Marine air masses mainly originating from the Bay of Bengal provided a large number of sea salts to the chemical composition, while trace elements during summer monsoon seasons were greatly affected by industrial emissions from South Asia. The flux of wet deposition was 1.12 kg N ha(-1) year(-1) for NH4(+)-N and 0.29 kg N ha(-1) year(-1) for NO3(-)-N. The total atmospheric deposition of N was estimated to be 6.41 kg N ha(-1) year(-1), implying potential impacts on the alpine ecosystem in this region.

  17. Spatial Co-Registration of Ultra-High Resolution Visible, Multispectral and Thermal Images Acquired with a Micro-UAV over Antarctic Moss Beds

    Directory of Open Access Journals (Sweden)

    Darren Turner

    2014-05-01

    Full Text Available In recent times, the use of Unmanned Aerial Vehicles (UAVs as tools for environmental remote sensing has become more commonplace. Compared to traditional airborne remote sensing, UAVs can provide finer spatial resolution data (up to 1 cm/pixel and higher temporal resolution data. For the purposes of vegetation monitoring, the use of multiple sensors such as near infrared and thermal infrared cameras are of benefit. Collecting data with multiple sensors, however, requires an accurate spatial co-registration of the various UAV image datasets. In this study, we used an Oktokopter UAV to investigate the physiological state of Antarctic moss ecosystems using three sensors: (i a visible camera (1 cm/pixel, (ii a 6 band multispectral camera (3 cm/pixel, and (iii a thermal infrared camera (10 cm/pixel. Imagery from each sensor was geo-referenced and mosaicked with a combination of commercially available software and our own algorithms based on the Scale Invariant Feature Transform (SIFT. The validation of the mosaic’s spatial co-registration revealed a mean root mean squared error (RMSE of 1.78 pixels. A thematic map of moss health, derived from the multispectral mosaic using a Modified Triangular Vegetation Index (MTVI2, and an indicative map of moss surface temperature were then combined to demonstrate sufficient accuracy of our co-registration methodology for UAV-based monitoring of Antarctic moss beds.

  18. Antarctic bacterial isolates that produce cold-active extracellular proteases at low temperature but are active and stable at high temperature

    Directory of Open Access Journals (Sweden)

    Cecilia Martínez-Rosales

    2011-04-01

    Full Text Available We report the isolation and identification of bacteria that produce extracellular cold-active proteases, obtained from water samples collected near the Uruguayan Antarctic Base on King George Island, South Shetlands. The bacteria belonged to the genera Pseudomonas (growth between 4 and 30 °C and Flavobacterium (growth between 4 and 18 °C. In all cases, extracellular protease production was evident when reaching the stationary phase at 18 and 4 °C but was not detected at 30 °C. The zymogram revealed the secretion of one extracellular protease per isolate, each with different relative electrophoretic mobility. The extracellular proteases produced at 4 °C showed thermal activity and stability at 30 °C. Both activity and stability at a temperature higher that 10 °C have no physiological meaning because the isolates do not experience such temperatures in the Antarctic environment; however, the possible ecological value of cold-active and -stable extracellular proteases is discussed.

  19. Environmental contamination in Antarctic ecosystems.

    Science.gov (United States)

    Bargagli, R

    2008-08-01

    Although the remote continent of Antarctica is perceived as the symbol of the last great wilderness, the human presence in the Southern Ocean and the continent began in the early 1900s for hunting, fishing and exploration, and many invasive plant and animal species have been deliberately introduced in several sub-Antarctic islands. Over the last 50 years, the development of research and tourism have locally affected terrestrial and marine coastal ecosystems through fuel combustion (for transportation and energy production), accidental oil spills, waste incineration and sewage. Although natural "barriers" such as oceanic and atmospheric circulation protect Antarctica from lower latitude water and air masses, available data on concentrations of metals, pesticides and other persistent pollutants in air, snow, mosses, lichens and marine organisms show that most persistent contaminants in the Antarctic environment are transported from other continents in the Southern Hemisphere. At present, levels of most contaminants in Antarctic organisms are lower than those in related species from other remote regions, except for the natural accumulation of Cd and Hg in several marine organisms and especially in albatrosses and petrels. The concentrations of organic pollutants in the eggs of an opportunistic top predator such as the south polar skua are close to those that may cause adverse health effects. Population growth and industrial development in several countries of the Southern Hemisphere are changing the global pattern of persistent anthropogenic contaminants and new classes of chemicals have already been detected in the Antarctic environment. Although the Protocol on Environmental Protection to the Antarctic Treaty provides strict guidelines for the protection of the Antarctic environment and establishes obligations for all human activity in the continent and the Southern Ocean, global warming, population growth and industrial development in countries of the Southern

  20. Moessbauer study of thermal metamorphosed Antarctic meteorites

    Energy Technology Data Exchange (ETDEWEB)

    Scorzelli, R.B. (Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, RJ (Brazil)); Galvao da Silva, E. (Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, RJ (Brazil) Dept. de Fisica, Univ. Federal de Minas Gerais, Belo Horizonte (Brazil)); Souza Azevedo, I. (Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, RJ (Brazil))

    1994-02-01

    In this paper we report on variable temperature Moessbauer spectroscopy measurements on Yamato-82162 and Yamato-86720. These Antarctic carbonaceous chondrites contrast with other non-Antarctic carbonaceous chondrites in which no evidences of thermal metamorphism have been found. (orig.)

  1. Regulating Antarctic Tourism and the Precautionary Principle

    NARCIS (Netherlands)

    Bastmeijer, C.J.; Roura, R.

    2004-01-01

    On the basis of an overview of the developments in Antarctic tourism since 1956, this current development note examines the issue of international regulation of Antarctic tourism. After discussing one of the main management issues in respect of Antarctic tourism ¿ the assessment and prevention of cu

  2. Geoethical Approach to Antarctic Subglacial Lakes Exploration

    Science.gov (United States)

    Talalay, Pavel; Markov, Alexey; Sysoev, Mikhail

    2014-05-01

    Antarctic subglacial aquatic environment have become of great interest to the science community because they may provide unique information about microbial evolution, the past climate of the Earth, and the formation of the Antarctic ice sheet. Nowadays it is generally recognized that a vast network of lakes, rivers, and streams exists thousands of meters beneath Antarctic Ice Sheets. Up to date only four boreholes accessed subglacial aquatic system but three of them were filled with high-toxic drilling fluid, and the subglacial water was contaminated. Two recent exploration programs proposed by UK and USA science communities anticipated direct access down to the lakes Ellsworth and Whillans, respectively, in the 2012/2013 Antarctic season. A team of British scientists and engineers engaged in the first attempt to drill into Lake Ellsworth but failed. US research team has successfully drilled through 800 m of Antarctic ice to reach a subglacial lake Whillans and retrieve water and sediment samples. Both activities used hot-water drilling technology to access lakes. Hot water is considered by the world science community as the most clean drilling fluid medium from the present point of view but it cannot solve environmental problems in total because hot-water even when heated to 90 °C, filtered to 0.2 μm, and UV treated at the surface could pick up microorganisms from near-surface snow and circulate them in great volume through the borehole. Another negative impact of hot-water circulation medium is thermal pollution of subglacial water. The new approach to Antarctic subglacial lakes exploration is presented by sampling technology with recoverable autonomous sonde which is equipped by two hot-points with heating elements located on the bottom and top sides of the sonde. All down-hole sonde components will be sterilized by combination of chemical wash, HPV and UV sterilization prior using. At the beginning of the summer season sonde is installed on the surface of the

  3. Concentration and environmental significance of lead in surface snow of Antarctic ice sheet (III)

    Institute of Scientific and Technical Information of China (English)

    秦大河; 任贾文; 孙俊英; 陈瓞延; 文克玲; 李良权

    1995-01-01

    Lead as an ultra-trace heavy metal becomes one of popular topics in glaciochemistry of the Antarctic ice sheet, because of its very low concertration (pg·g-1) and background and its sensitivity to the quality of the environment. The lead concentration of surface snow of the Antarctic ice sheet (corresponding to modern precipitation) applying LEAF technique by Chinese scholars has systematically been studied for the first time in the world. The distribution principle of lead concentration of surface snow of the Antarctic ice sheet is "low in the west and high in the east" along the route of 1990 International Trans-Antarctic Expedition (ITAE). The concentration of lead in East Antarctica is 2 - 3 fold higher than that in Larsen ice shelf and Antarctic Peninsula, which majorly results from the activity of pre-Soviet Antarctic Expedition The concentration of lead in Larsen ice shelf and Antarctic Peninsula can be regarded as the background value of modern precipitation of the Antarctic ice sheet in the en

  4. Spatial pattern in Antarctica: what can we learn from Antarctic bacterial isolates?

    Science.gov (United States)

    Chong, Chun Wie; Goh, Yuh Shan; Convey, Peter; Pearce, David; Tan, Irene Kit Ping

    2013-09-01

    A range of small- to moderate-scale studies of patterns in bacterial biodiversity have been conducted in Antarctica over the last two decades, most suggesting strong correlations between the described bacterial communities and elements of local environmental heterogeneity. However, very few of these studies have advanced interpretations in terms of spatially associated patterns, despite increasing evidence of patterns in bacterial biogeography globally. This is likely to be a consequence of restricted sampling coverage, with most studies to date focusing only on a few localities within a specific Antarctic region. Clearly, there is now a need for synthesis over a much larger spatial to consolidate the available data. In this study, we collated Antarctic bacterial culture identities based on the 16S rRNA gene information available in the literature and the GenBank database (n > 2,000 sequences). In contrast to some recent evidence for a distinct Antarctic microbiome, our phylogenetic comparisons show that a majority (~75 %) of Antarctic bacterial isolates were highly similar (≥99 % sequence similarity) to those retrieved from tropical and temperate regions, suggesting widespread distribution of eurythermal mesophiles in Antarctic environments. However, across different Antarctic regions, the dominant bacterial genera exhibit some spatially distinct diversity patterns analogous to those recently proposed for Antarctic terrestrial macroorganisms. Taken together, our results highlight the threat of cross-regional homogenisation in Antarctic biodiversity, and the imperative to include microbiota within the framework of biosecurity measures for Antarctica.

  5. High temperature uniaxial deformation experiment of bubble-free highly crystalline magmas; a case study for the high-Mg andesite from Goshiki-dai lava plateau, southwest Japan (Invited)

    Science.gov (United States)

    Ishibashi, H.

    2013-12-01

    Rheological property of magma is a key factor for understanding various volcanic processes. Natural magmas commonly have crystals of various volume fraction and such suspended crystals strongly affect on magma rheology. For dilute to intermediately crystalline magmas, previous studies (e.g., Ishibashi, 2009JVGR; Vona et al. 2011ChemGeol) experimentally investigated the effects of suspended crystals on apparent viscosities and the model predicting the effects of crystals is proposed by Mader et al. (2013JVGR). However, for highly crystalline magmas, our knowledge on their complex rheological behaviors is still not enough even for bubble-free system whereas several experimental studies have been done (e.g., Carrichi et al., 2007EPSL; Picard et al., 2013JGR). Understanding rheological property in the crystal-melt two phase system is important for considering magma dynamics in deep magma chambers and dykes and also for investigating the property in bubble-crystal-melt three phase system. In this study, uniaxial compression deformation experiments were done for bubble-free, highly crystalline natural lava under high temperature, 1atm pressure conditions to investigate the effects of suspended crystals on rheology of bubble-free magma. The high-Mg andesite erupted at ca. 15 Ma from Goshiki-dai lava plateau, southwest Japan, was used for starting materials. The lava is aphyric, bubble-free, and composed of fine-grained elongated plagioclase, pyroxenes, and magnetite crystals and unaltered silicate glass. Crystal volume fraction is ca. 0.65. Samples were cut into rectangular with 15mm length, 15mm width, and 30 mm high from massive portion of lava without any visible fracture. The samples were deformed by using the high temperature uniaxial compression apparatus, installed at Earthquake Research Institute, the University of Tokyo, under conditions of temperature from 1292 to 1133 K, log strain rate from -5.5 to -2.5, and 1 atm pressure. Total strains of the samples are

  6. Role of Indian remote sensing imaging satellites for the Antarctic monitoring and mapping: a case study around Indian Antarctic research stations

    Science.gov (United States)

    Jayaprasad, P.; Mehra, Raghav; Chawla, Saket; Rajak, D. Ram; Oza, Sandip R.

    2016-05-01

    Antarctic research station's existence largely depend on the supply of fuel, food and other commodities through Antarctic Scientific Expedition using ship voyage. Safer Ship Navigation demands high resolution satellite monitoring of the ice conditions which varies from 30 km to 200 km from the Antarctic coast of Research stations. During the last couple of years Indian Satellites play a major role in safer ship navigation in sea ice regions of the Arctic and the Antarctic. Specifically Indian Scientific Expedition to the Antarctica (ISEA) through National Centre for Antarctic and Oceanic Research (NCAOR) is one of the beneficiaries for safer ship navigation using information derived from Indian Satellite data. Space Applications Centre, Indian Space Research Organisation (SAC-ISRO) is providing Sea Ice Advisories for the safer optimum entry and exit for the expedition ship at two of the Research stations Bharati and Maitri. Two of the Indian Satellites namely Radar Imaging Satellite-1 (RISAT-1) and ResourceSAT-2 (RS-2) are the two major workhorses of ISRO for monitoring and mapping of the Antarctic terrain. The present study demonstrate the utilisation potential of these satellite images for various Polar Science Applications. Mosaic of the Antarctic Terrain was generated from RISAT-1 CRS data. The preliminary results of the mosaic from CRS- circular polarisation data is presented. Demonstration of the study is extended for other applications such as change detection studies, safer ship navigation and extreme events of Antarctica. The use of multi resolution multi sensor data is also shown in the study.

  7. Antarctic marine biodiversity and deep-sea hydrothermal vents.

    Directory of Open Access Journals (Sweden)

    Steven L Chown

    2012-01-01

    Full Text Available The diversity of many marine benthic groups is unlike that of most other taxa. Rather than declining from the tropics to the poles, much of the benthos shows high diversity in the Southern Ocean. Moreover, many species are unique to the Antarctic region. Recent work has shown that this is also true of the communities of Antarctic deep-sea hydrothermal vents. Vent ecosystems have been documented from many sites across the globe, associated with the thermally and chemically variable habitats found around these, typically high temperature, streams that are rich in reduced compounds and polymetallic sulphides. The animal communities of the East Scotia Ridge vent ecosystems are very different to those elsewhere, though the microbiota, which form the basis of vent food webs, show less differentiation. Much of the biological significance of deep-sea hydrothermal vents lies in their biodiversity, the diverse biochemistry of their bacteria, the remarkable symbioses among many of the marine animals and these bacteria, and the prospects that investigations of these systems hold for understanding the conditions that may have led to the first appearance of life. The discovery of diverse and unusual Antarctic hydrothermal vent ecosystems provides opportunities for new understanding in these fields. Moreover, the Antarctic vents south of 60°S benefit from automatic conservation under the Convention on the Conservation of Antarctic Marine Living Resources and the Antarctic Treaty. Other deep-sea hydrothermal vents located in international waters are not protected and may be threatened by growing interests in deep-sea mining.

  8. Norhla: Restoring the glory of khullu wool for social development and environmental protection in the High Tibetan Plateau Norhla : la laine de yak (khullu) comme vecteur de développement social et de protection environnementale sur le haut plateau du Tibet Norlha, o cómo recuperar la gloria de la lana de Kullu para fomentar el desarrollo social y la protección medioambiental del altiplano tibetano

    OpenAIRE

    Jean Marc Guesné; Anne Michaut-Denizeau; Alice Sireyjol

    2012-01-01

    For centuries, the local communities of yaks’ transhumant cattle farmers of the Tibetan High plateau have lived on their yak breeding activity, providing them with all they need: milk, a source of butter and cheese, and hair, which they weave into the heavy black tents that characterize the nomadic population. In the last decade, however, changes occurred that have destabilized this activity. The changes are three-fold: (1) increasing economic difficulty to live from this activity (Melvyn et ...

  9. Principles of the Antarctic Treaty

    Science.gov (United States)

    Candidi, M.

    The operation of any base or expedition to Antarctica is regulated by the mutual agreement among nations in the “Antarctic Treaty”. This treaty deals with the major aspects of life in Antarctica and its main principles and provisions are described in what follows.

  10. Special Stamps:Antarctic Scenery

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In July 2002, the State Postal Bureau issued a set of three stamps, whose theme is Antarctic scenery.The first stamp depicts an iceberg. Antarctica is where 90 percent of the world’s ice exists. Each year countless icebergs float majestically through the sea, and are a magnificent scenic feature of Antarctica.

  11. CENTRAL PLATEAU REMEDIATION OPTIMIZATION STUDY

    Energy Technology Data Exchange (ETDEWEB)

    BERGMAN, T. B.; STEFANSKI, L. D.; SEELEY, P. N.; ZINSLI, L. C.; CUSACK, L. J.

    2012-09-19

    THE CENTRAL PLATEAU REMEDIATION OPTIMIZATION STUDY WAS CONDUCTED TO DEVELOP AN OPTIMAL SEQUENCE OF REMEDIATION ACTIVITIES IMPLEMENTING THE CERCLA DECISION ON THE CENTRAL PLATEAU. THE STUDY DEFINES A SEQUENCE OF ACTIVITIES THAT RESULT IN AN EFFECTIVE USE OF RESOURCES FROM A STRATEGIC PERSPECTIVE WHEN CONSIDERING EQUIPMENT PROCUREMENT AND STAGING, WORKFORCE MOBILIZATION/DEMOBILIZATION, WORKFORCE LEVELING, WORKFORCE SKILL-MIX, AND OTHER REMEDIATION/DISPOSITION PROJECT EXECUTION PARAMETERS.

  12. Magnetotelluric sounding results in eastern Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    马晓冰; 孔祥儒; 刘宏兵; 闫永利

    2001-01-01

    The results of Zayu-Qingshuihe MT sounding profile carried out in eastern Tibetan Plateau are presented in this paper. Using 2-D RRI method, the resistivity distribution with depth is obtained along the profile. It is featured by the resistivity zones in the horizontal direction and layers in the vertical direction. The Bangong-Nujiang suture zone and Jinshajiang suture zone are both important electrical conductivity-separating zones in the plateau, and the former is a zone with relatively low resistivity while the latter is an electrical conductivity gradient zone. The highly electrical conductive bodies in the mid and lower crust of northern Qiangtang and Bayan Har Terrain might be caused by regional melting due to shear heating during the process of subduction in tectonic evolution.

  13. Global pollution shown by lead and cadmium contents in precipitation of polar regions and Qinghai-Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The analysis of the major ions, lead and cadmium has been performed for snow-pit samples collected from the Arctic, the Qinghai-Tibetan Plateau and the Antarctic Ice Sheet. These snow pits were excavated respectively from the snowpack in Canadian Northwest Territory (NWT) and the central Arctic, three glaciers on the Qinghai-Tibetan Plateau and surface snow along the route of the International Trans-Antarctic Expedition (ITAE). The source regions for the lead pollution of central Arctic have been identified by analyzing of stable lead isotopic ratios, meteorological and atmospheric chemistry studies. It shows that the central Arctic is still under intensive lead input, despite the fact that lead content in Greenland Ice Sheet displays a rapid decreasing since the 1970s due to US and some European countries' campaigns to reduce lead-containing gasoline-additives. This is because there are multiple lead sources for the central Arctic, including the countries that have not performed gasoline-additives reducing. The backgrounds of atmospheric aerosol compositions, as well as the concentrations of lead and cadmium in precipitation of the early 1990s, are contrasted among the Arctic, Antarctica and Qinghai-Tibetan Plateau. The measured lead content in the snowfall at the typical sites of the three regions is divided into natural (background) and anthropogenic components. It is found that natural lead concentration (mainly crustal and/or sea-salt lead) is roughly equal among the three regions (50% in Antarctic precipitation, >97% in the Arctic and the Qinghai-Tibetan Plateau ) is mainly responsible for the lead input to both polar regions and to the Qinghai-Tibetan Plateau. Lead pollution may have spread into the whole troposphere and the most remote regions on earth.

  14. Recent increase in Antarctic Peninsula ice core uranium concentrations

    Science.gov (United States)

    Potocki, Mariusz; Mayewski, Paul A.; Kurbatov, Andrei V.; Simões, Jefferson C.; Dixon, Daniel A.; Goodwin, Ian; Carleton, Andrew M.; Handley, Michael J.; Jaña, Ricardo; Korotkikh, Elena V.

    2016-09-01

    Understanding the distribution of airborne uranium is important because it can result in both chemical and radiological toxicity. Ice cores offer the most robust reconstruction of past atmospheric levels of toxic substances. Here we present the first sub-annually dated, continuously sampled ice core documenting change in U levels in the Southern Hemisphere. The ice core was recovered from the Detroit Plateau, northern Antarctic Peninsula, in 2007 by a joint Brazilian-Chilean-US team. It displays a significant increase in U concentration that coincides with reported mining activities in the Southern Hemisphere, notably Australia. Raw U concentrations in the Detroit Plateau ice core increased by as much as 102 between the 1980s and 2000s accompanied by increased variability in recent years. Decadal mean U concentrations increased by a factor of ∼3 from 1980 to 2007, reaching a mean of 205 pg/L from 2000 to 2007. The fact that other terrestrial source dust elements such as Ce, La, Pr, and Ti do not show a similar increase and that the increased U concentrations are enriched above natural crustal levels, supports an anthropogenic source for the U as opposed to a change in atmospheric circulation.

  15. Oceanographic profile temperature, salinity, and other measurements collected using bottle and high resolution CTD from the SHIRASE (JSVY), SHOYO, and other platforms in the Antarctic, South Indian, and other locations from 1987 to 2000 (NODC Accession 0001363)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The data from the CD-ROM contains the BT Data observed by Japan Maritime Self-Defence Force from 1995 to 2001, Japan Antarctic Research Expedition data up to the...

  16. Halogen species record Antarctic sea ice extent over glacial–interglacial periods

    Directory of Open Access Journals (Sweden)

    A. Spolaor

    2013-07-01

    Full Text Available Sea ice is an integral part of the earth's climate system because it affects planetary albedo, sea-surface salinity, and the atmosphere–ocean exchange of reactive gases and aerosols. Bromine and iodine chemistry is active at polar sea ice margins with the occurrence of bromine explosions and the biological production of organoiodine from sea ice algae. Satellite measurements demonstrate that concentrations of bromine oxide (BrO and iodine oxide (IO decrease over sea ice toward the Antarctic interior. Here we present speciation measurements of bromine and iodine in the TALDICE (TALos Dome Ice CorE ice core (159°11' E, 72°49' S; 2315 m a.s.l. spanning the last 215 ky. The Talos Dome ice core is located 250 km inland and is sensitive to marine air masses intruding onto the Antarctic Plateau. Talos Dome bromide (Br− is positively correlated with temperature and negatively correlated with sodium (Na. Based on the Br−/Na seawater ratio, bromide is depleted in the ice during glacial periods and enriched during interglacial periods. Total iodine, consisting of iodide (I− and iodate (IO3−, peaks during glacials with lower values during interglacial periods. Although IO3− is considered the most stable iodine species in the atmosphere it was only observed in the TALDICE record during glacial maxima. Sea ice dynamics are arguably the primary driver of halogen fluxes over glacial–interglacial timescales, by altering the distance between the sea ice edge and the Antarctic plateau and by altering the surface area of sea ice available to algal colonization. Based on our results we propose the use of both halogens for examining Antarctic variability of past sea ice extent.

  17. Transpression and tectonic exhumation in the Heimefrontfjella, western orogenic front of the East African/Antarctic Orogen, revealed by quartz textures of high strain domains

    Directory of Open Access Journals (Sweden)

    Wilfried Bauer

    2016-06-01

    Full Text Available The metamorphic basement of the Heimefrontfjella in western Dronning Maud Land (Antarctica forms the western margin of the major ca. 500 million year old East African/East Antarctic Orogen that resulted from the collision of East Antarctica and greater India with the African cratons. The boundary between the tectonothermally overprinted part of the orogen and its north-western foreland is marked by the subvertical Heimefront Shear Zone. North-west of the Heimefront Shear Zone, numerous low-angle dipping ductile thrust zones cut through the Mesoproterozoic basement. Petrographic studies, optical quartz c-axis analyses and x-ray texture goniometry of quartz-rich mylonites were used to reveal the conditions that prevailed during the deformation. Mineral assemblages in thrust mylonites show that they were formed under greenschist-facies conditions. Quartz microstructures are characteristic of the subgrain rotation regime and oblique quartz lattice preferred orientations are typical of simple shear-dominated deformation. In contrast, in the Heimefront Shear Zone, quartz textures indicate mainly flattening strain with a minor dextral rotational component. These quartz microstructures and lattice preferred orientations show signs of post-tectonic annealing following the tectonic exhumation. The spatial relation between the sub-vertical Heimefront Shear Zone and the low-angle thrusts can be explained as being the result of strain partitioning during transpressive deformation. The pure-shear component with a weak dextral strike-slip was accommodated by the Heimefront Shear Zone, whereas the north–north-west directed thrusts accommodate the simple shear component with a tectonic transport towards the foreland of the orogen.

  18. Chemical studies of differentiated meteorites. I - Labile trace elements in Antarctic and non-Antarctic eucrites

    Science.gov (United States)

    Paul, Rick L.; Lipschutz, Michael E.

    1990-01-01

    Element contents of Ag, Au, Bi, Cd, Co, Cs, Ga, In, Rb, Sb, Se, Te, Tl, U, and Zn were analyzed, using RNAA, in 25 Antarctic and nine non-Antarctic eucrites to determine whether these two populations differ significantly in thermal history and derive from the same or different eucrite parent body. Data for these 15 elements indicate that basaltic Antarctic and non-Antarctic eucrite populations reflect the same genetic processes and, hence, come from the same parent asteroid.

  19. Chlorine Monoxide in the Antarctic Spring Stratosphere.

    Science.gov (United States)

    Jaramillo-Ayerbe, Mauricio

    1988-06-01

    A series of observations of stratospheric chlorine monoxide (ClO) were carried out during the austral springs of 1986 and 1987 in McMurdo Station, Antarctica, as part of two experimental campaigns sent to investigate the seasonal decrease in ozone over the antarctic continent (the ozone "hole"). Measurements of the vertical distribution of ClO were obtained by high resolution ground-based emission spectroscopy at 278 GHz, using the Stony Brook mm-wave receiver. They show the presence of an anomalous layer of lower stratospheric ClO which is not observed at other latitudes. This anomalous layer is centered at ~20 km altitude and exhibits a pronounced diurnal variation, reaching a maximum at midday and disappearing at night. During the period of Sep. 20-24, 1987, the lower-stratospheric ClO had a maximum volume mixing ratio of 1.8_sp{+0cdot5}{ -0cdot9} ppbv. A normal ClO layer centered at ~36 km was also observed, with concentrations and diurnal behavior similar to those seen in tropical latitudes. These findings are evidence of anomalous chlorine chemistry taking place in the lower stratosphere during the antarctic spring, and indicate that increasing anthropogenic chlorine is a prime causative agent in the formation of the ozone hole.

  20. Multibranch Antarctic Seismic Data Library facilitates research

    Science.gov (United States)

    Cooper, Alan K.

    In 1991, investigators from 11 nations involved in Antarctic multichannel seismic (MCS) reflection research sought a way to keep the Antarctic Treaty's promise of open access to data, and in the process to encourage Earth-science research using seismic data. The Antarctic Seismic Data Library System for Cooperative Research (SDLS) was the solution, and is now a recommendation of the Antarctic Treaty Consultative Parties (ATCP). Today—at 12 branches spanning the world—researchers can access over 68,000 km of marine MCS data to use for cooperative research.More than 150,000 km of MCS data have been accumulated since 1976 by 13 countries on nearly 70 cruises. The majority of data now in the library cover the Ross Sea, Wilkes Land, and Prydz Bay sectors of the Antarctic margin, with smaller amounts from the Weddell Sea and the Antarctic Peninsula.

  1. The Antarctic Search for Meteorites: The Future of Space, on Earth Today - EVA Knowledge Capture Outbrief

    Science.gov (United States)

    Love, Stan

    2013-01-01

    NASA astronaut Stan Love shared his experiences with the Antarctic Search for Meteorites (ANSMET), an annual expedition to the southern continent to collect valuable samples for research in planetary science. ANSMET teams operate from isolated, remote field camps on the polar plateau, where windchill factors often reach -40 F. Several astronaut participants have noted ANSMET's similarity to a space mission. Some of the operational concepts, tools, and equipment employed by ANSMET teams may offer valuable insights to designers of future planetary surface exploration hardware.

  2. Antarctic glaciation caused ocean circulation changes at the Eocene-Oligocene transition.

    Science.gov (United States)

    Goldner, A; Herold, N; Huber, M

    2014-07-31

    Two main hypotheses compete to explain global cooling and the abrupt growth of the Antarctic ice sheet across the Eocene-Oligocene transition about 34 million years ago: thermal isolation of Antarctica due to southern ocean gateway opening, and declining atmospheric CO2 (refs 5, 6). Increases in ocean thermal stratification and circulation in proxies across the Eocene-Oligocene transition have been interpreted as a unique signature of gateway opening, but at present both mechanisms remain possible. Here, using a coupled ocean-atmosphere model, we show that the rise of Antarctic glaciation, rather than altered palaeogeography, is best able to explain the observed oceanographic changes. We find that growth of the Antarctic ice sheet caused enhanced northward transport of Antarctic intermediate water and invigorated the formation of Antarctic bottom water, fundamentally reorganizing ocean circulation. Conversely, gateway openings had much less impact on ocean thermal stratification and circulation. Our results support available evidence that CO2 drawdown--not gateway opening--caused Antarctic ice sheet growth, and further show that these feedbacks in turn altered ocean circulation. The precise timing and rate of glaciation, and thus its impacts on ocean circulation, reflect the balance between potentially positive feedbacks (increases in sea ice extent and enhanced primary productivity) and negative feedbacks (stronger southward heat transport and localized high-latitude warming). The Antarctic ice sheet had a complex, dynamic role in ocean circulation and heat fluxes during its initiation, and these processes are likely to operate in the future.

  3. Eocene Tibetan Plateau remnants preserved in the Northwest Himalaya

    Science.gov (United States)

    van der Beek, P. A.; van Melle, J.; Guillot, S.; Pêcher, A.; Reiners, P. W.; Nicolescu, S.; Latif, M.

    2009-04-01

    The northwest Himalaya shows strongly contrasting relief, opposing deeply incised mountain ranges characterized by extremely rapid exhumation and some of the highest peaks in the world (i.e., the Karakorum range and Nanga Parbat massif) to high-elevation, low-relief areas such as the 4000-m high Deosai plateau in northern Pakistan and the 5000-m high Tso Morari in Indian Ladakh. The origin and evolution of such plateau regions in the syntaxis of the most active continental collision in the world remain elusive. Here, we report the first low-temperature thermochronology (apatite fission-track, apatite and zircon (U-Th)/He) data from the Deosai plateau and use thermal history modelling to show that it has undergone continuous slow (≤ 200 m/Myr) denudation and has thus remained tectonically stable for the last 35 Myr at least. The inferred history of constant slow denudation of the plateau contradicts the hypothesis that widespread low-relief surfaces in the northwest Himalaya result from efficient, km-scale glacial erosion during Quaternary times; such erosion would have been recorded as a phase of rapid recent denudation that is not observed in the data. Slow continuous denudation since Eocene times, i.e. only 15-20 Myr after the onset of India-Asia collision implies that the Deosai plateau surface developed early in the Himalayan history and limits the phase of orogenic relief growth in the Ladakh-Kohistan arc to the early Paleogene. Although thermochronology data do not directly record surface uplift, the simplest explanation for the inferred constant denudation rates is that the plateau had reached its present-day elevation already during the Eocene, as a later phase of surface uplift would have triggered an erosional response that would have been recorded by the thermochronology data. We use morphological analyses to characterise such plateaux and identify them at the scale of the entire northwest Himalaya and compare our thermochronological data with

  4. Metagenomic analysis of a Southern Maritime Antarctic soil

    Directory of Open Access Journals (Sweden)

    David Anthony Pearce

    2012-12-01

    Full Text Available Our current understanding of Antarctic soils is derived from direct culture on selective media, biodiversity studies based on clone library construction and analysis, quantitative PCR amplification of specific gene sequences and the application of generic microarrays for microbial community analysis. Here, we investigated the biodiversity and functional potential of a soil community at Mars Oasis on Alexander Island in the southern Maritime Antarctic, by applying 454 pyrosequencing technology to a metagenomic library constructed from soil genomic DNA. The results suggest that the commonly cited range of phylotypes used in clone library construction and analysis of 78-730 OTUs (de-replicated to 30-140 provides low coverage of the major groups present (~5%. The vast majority of functional genes (>77% were for structure, carbohydrate metabolism and DNA/RNA processing and modification. This study suggests that prokaryotic diversity in Antarctic terrestrial environments appears to be limited at the generic level, with Proteobacteria, Actinobacteria being common. Cyanobacteria were surprisingly under-represented at 2.6% of sequences, although ~1% of the genes identified were involved in CO2 fixation. At the sequence level there appeared to be much greater heterogeneity, and this might be due to high divergence within the relatively restricted lineages which have successfully colonized Antarctic terrestrial environments.

  5. Holocene high-resolution quantitative summer temperature reconstruction based on subfossil chironomids from the southeast margin of the Qinghai-Tibetan Plateau

    Science.gov (United States)

    Zhang, Enlou; Chang, Jie; Cao, Yanmin; Sun, Weiwei; Shulmeister, James; Tang, Hongqu; Langdon, Peter G.; Yang, Xiangdong; Shen, Ji

    2017-06-01

    This paper reports the first quantitative summer (mean July) temperature reconstruction based on subfossil chironomids from the southeast margin of the Qinghai-Tibetan Plateau (QTP) covering the end of the last deglaciation and the entire Holocene, spanning 11,800 cal yr BP to the present. The record is based on 223 chironomid samples throughout a 927 cm sediment core providing a temporal resolution of ∼50 years per sample. We validate the record by applying several statistical reconstruction diagnostics and comparing with pollen and diatom records from the same sediment core. The record suggests the summer temperature varies by ∼2.5 °C across the entire period. A generally warmer period occurred between c.8500 and c.6000 cal yr BP and a cooling trend was initiated from c.5500 cal yr BP. The overall pattern broadly matches the summer insolation at 30°N and the Asian Summer Monsoon records from the surrounding regions suggesting that summer temperatures from the southeast margin of the QTP respond to insolation forcing and monsoon driven variability on a multi-millennial time scale. Modifications of this overall trend are observed on the finer temporal resolution and we suggest that solar activity could be an important mechanism driving the centennial-scale variability. It may have a strengthened effect in the late Holocene when the monsoon influence weakened. Further detailed investigation is needed to disentangle these effects on the climate change over the highlands of southwestern China.

  6. On the origin and evolution of Antarctic Peracarida (Crustacea, Malacostraca

    Directory of Open Access Journals (Sweden)

    Angelika Brandt

    1999-12-01

    not very likely (some Isopoda, like the Sphaeromatidea, are widely distributed in the Subantarctic, but rare in the high Antarctic. However, it could also be that the species of this family and others were not able to survive when the ice reached the sublittoral shelf in the high Antarctic during glacial periods.

  7. Getting around Antarctica: new high-resolution mappings of the grounded and freely-floating boundaries of the Antarctic ice sheet created for the International Polar Year

    Directory of Open Access Journals (Sweden)

    R. Bindschadler

    2011-07-01

    Full Text Available Two ice-dynamic transitions of the Antarctic ice sheet – the boundary of grounded ice features and the freely-floating boundary – are mapped at 15-m resolution by participants of the International Polar Year project ASAID using customized software combining Landsat-7 imagery and ICESat/GLAS laser altimetry. The grounded ice boundary is 53 610 km long; 74 % abuts to floating ice shelves or outlet glaciers, 19 % is adjacent to open or sea-ice covered ocean, and 7 % of the boundary ice terminates on land. The freely-floating boundary, called here the hydrostatic line, is the most landward position on ice shelves that expresses the full amplitude of oscillating ocean tides. It extends 27 521 km and is discontinuous. Positional (one-sigma accuracies of the grounded ice boundary vary an order of magnitude ranging from ±52 m for the land and open-ocean terminating segments to ±502 m for the outlet glaciers. The hydrostatic line is less well positioned with errors over 2 km. Elevations along each line are selected from 6 candidate digital elevation models based on their agreement with ICESat elevation values and surface shape inferred from the Landsat imagery. Elevations along the hydrostatic line are converted to ice thicknesses by applying a firn-correction factor and a flotation criterion. BEDMAP-compiled data and other airborne data are compared to the ASAID elevations and ice thicknesses to arrive at quantitative (one-sigma uncertainties of surface elevations of ±3.6, ±9.6, ±11.4, ±30 and ±100 m for five ASAID-assigned confidence levels. Over one-half of the surface elevations along the grounded ice boundary and over one-third of the hydrostatic line elevations are ranked in the highest two confidence categories. A comparison between ASAID-calculated ice shelf thicknesses and BEDMAP-compiled data indicate a thin-ice bias of 41.2 ± 71.3 m for the ASAID ice thicknesses. The relationship between the seaward offset of the hydrostatic line

  8. Getting around Antarctica: New High-Resolution Mappings of the Grounded and Freely-Floating Boundaries of the Antarctic Ice Sheet Created for the International Polar Year

    Science.gov (United States)

    Bindschadler, R.; Choi, H.; Wichlacz, A.; Bingham, R.; Bohlander, J.; Brunt, K.; Corr, H.; Drews, R.; Fricker, H.; Hall, M.; Hindmarsh, R.; Kohler, J.; Padman, L.; Rack, W.; Rotschkly, G.; Urbini, S.; Vornberger, P.; Young, N.

    2011-01-01

    Two ice-dynamic transitions of the Antarctic ice sheet - the boundary of grounded ice features and the freely-floating boundary - are mapped at 15-m resolution by participants of the International Polar Year project ASAID using customized software combining Landsat-7 imagery and ICESat/GLAS laser altimetry. The grounded ice boundary is 53 610 km long; 74% abuts to floating ice shelves or outlet glaciers, 19% is adjacent to open or sea-ice covered ocean, and 7% of the boundary ice terminates on land. The freely-floating boundary, called here the hydrostatic line, is the most landward position on ice shelves that expresses the full amplitude of oscillating ocean tides. It extends 27 521 km and is discontinuous. Positional (one-sigma) accuracies of the grounded ice boundary vary an order of magnitude ranging from +/- 52m for the land and open-ocean terminating segments to +/- 502m for the outlet glaciers. The hydrostatic line is less well positioned with errors over 2 km. Elevations along each line are selected from 6 candidate digital elevation models based on their agreement with ICESat elevation values and surface shape inferred from the Landsat imagery. Elevations along the hydrostatic line are converted to ice thicknesses by applying a firn-correction factor and a flotation criterion. BEDMAP-compiled data and other airborne data are compared to the ASAID elevations and ice thicknesses to arrive at quantitative (one-sigma) uncertainties of surface elevations of +/-3.6, +/-9.6, +/-11.4, +/-30 and +/-100m for five ASAID-assigned confidence levels. Over one-half of the surface elevations along the grounded ice boundary and over one-third of the hydrostatic line elevations are ranked in the highest two confidence categories. A comparison between ASAID-calculated ice shelf thicknesses and BEDMAP-compiled data indicate a thin-ice bias of 41.2+/-71.3m for the ASAID ice thicknesses. The relationship between the seaward offset of the hydrostatic line from the grounded ice

  9. Amplitude of climatic changes in Qinghai-Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    On the basis of ice core and meteorological data from the Qinghai-Tibetan (Q-T) Plateau, this article focuses on the discussion of the problems related to the sensitivity of temporal and spatial changes of the climate in high-altitude regions, particularly in the Q-T Plateau. The features of abrupt climatic changes of the past 100 ka, 2 000 a and recent years indicate that the amplitude of these changes in the Q-T Plateau was obviously larger than that in low-altitude regions. The scope of temperature change above 6 000 m in the Q-T Plateau between glacial and interglacial stages could reach over 10℃, but only about 4℃ in low-elevation regions close to sea level. During the last 2 000 a, the amplitude of temperature changes at Guliya (over 6 000 m a.s.l.) in the Q-T Plateau reached 7℃, in comparison with 2℃ in eastern China at low altitude. In the present age, apparent differences of climatic warming have been observed in the Q-T Plateau, indicating that the warming in high-elevation regions is much higher than that in low-elevation regions. The temperature in over 3 500 m regions of the Q-T Plateau have been increasing at a rate of 0.25×10-1/a in recent 30 years, but almost no change has taken place in the regions below 500 m. Thus, we concluded that high-altitude regions are more sensitive to climatic changes than the low-altitude regions.

  10. Antarctic Crustal Thickness from Gravity Inversion

    Science.gov (United States)

    Vaughan, A. P.; Kusznir, N. J.; Ferraccioli, F.; Jordan, T. A.

    2013-12-01

    Using gravity anomaly inversion, we have produced the first comprehensive regional maps of crustal thickness and oceanic lithosphere distribution for Antarctica and the Southern Ocean. We determine Moho depth, crustal basement thickness, continental lithosphere thinning (1-1/β) and ocean-continent transition location using a 3D spectral domain gravity inversion method, which incorporates a lithosphere thermal gravity anomaly correction. The continental lithosphere thinning distribution, used to define the initial thermal model temperature perturbation is derived from the gravity inversion and uses no a priori isochron information; as a consequence the gravity inversion method provides a prediction of ocean-continent transition location, which is independent of ocean isochron information. The gravity anomaly contribution from ice thickness is included in the gravity inversion, as is the contribution from sediments which assumes a compaction controlled sediment density increase with depth. Data used in the gravity inversion are elevation and bathymetry, free-air gravity anomaly, the most recent Bedmap2 ice thickness and bedrock topography compilation south of 60 degrees south (Fretwell et al., 2013) and relatively sparse constraints on sediment thickness. Our gravity inversion study predicts thick crust (> 45 km) under interior East Antarctica penetrated by narrow continental rifts that feature relatively thinner crust. The East Antarctic Rift System (EARS) is a major Permian to Cretaceous age rift system that appears to extend from the continental margin at the Lambert Rift to the South Pole region, a distance of 2500 km. This is comparable in scale to the well-studied East African rift system. Intermediate crustal thickness with an inferred linear rift fabric is predicted under Coates Land. An extensive region of either thick oceanic crust or highly thinned continental crust is predicted offshore Oates Land and north Victoria Land, and also off West Antarctica

  11. The crustal composition of the Falkland Plateau

    Science.gov (United States)

    Klemt, Claudia; Jokat, Wilfried

    2015-04-01

    The Falkland Islands are situated in the South Atlantic Ocean 500 km east of Patagonia, South America. The islands are part of the Falkland Plateau, which stretches eastward for more than 1500 km. A bathymetric high, the Maurice Ewing Bank, terminates the plateau in the east. Until Late Jurassic the Falkland Islands were part of Gondwana and were located adjacent to the east coast of South Africa. While the Falkland Islands and Maurice Ewing Bank are proved to be of continental composition, the nature and structure of the Falkland Plateau's basement in between is debatable. The first crustal model derived from sonobuoy data contradicts an only recently published 3D-gravity model. To enhance the understanding of Gondwana break-up considering timing, geometry and amount of volcanism, further knowledge about the structure and thickness of the crust is inevitable. During the ANT-XXIX/5 Polarstern cruise seismic refraction measurements were conducted using Ocean Bottom Seismometers (OBS) and Reftek land stations onshore of East Falkland. The OBS were deployed at 78 locations along an approximately 1500 km east-west stretching profile. For the western transect a P-wave velocity model is calculated using 2D-raytracing techniques. The results are presented in combination with potential field data showing the extension of the Falkland Islands basement, the continent-ocean transition zone and the crustal structure of the plateau. On the Falkland Plateau Basin sediment thickness is about 6 km with velocities ranging from 1.7 to 4.1 km/s in the upper part and about 4.7 km/s above basement. The crust is of oceanic composition with an igneous section that is considerably thicker than average oceanic crust (up to 17 km). The velocity structure in the upper crustal part is typical for layer 2 with a velocity gradient ranging from 5.4 km/s to 6.5 km/s and thicknesses between 1.5 km and 4 km. Layer 3 is about 14 km thick with a velocity gradient from 6.6 km/s to 7.6 km/s, which is

  12. 滇中盆地和金沙江谷地高产水稻的产量形成特点%Yield formation of high yield rice in the middle basin and Jinsha River valley of Yunnan plateau

    Institute of Scientific and Technical Information of China (English)

    路季梅; 杨家庆; 宋令荣; 程在全; 普双有

    2001-01-01

    研究表明,滇中盆地和金沙江谷地高产水稻(10.5~15 t*hm -2)的产量形成特点为:(1)产量结构上具有单位面积穗数多和每穗粒数多的优势,在大群体条件下仍保持高的结实率和大穗优势;(2)水稻的生育期长和高原独特的光温条件有利于植株的稳健生长和产量器官的协调发展;(3)光合速率高,干物质积累量大,库源关系协调。这些特点的形成与高原独特的气候生态条件和栽培管理密切相关。%The characteristics of yield formation of high-yield rice with yield of 10.5-15.0t*hm-2 in the middle basin and Jinsha River valley of Yunnan plateau were studied.The yield formation of high-yield rice in those areas was characterized by the following three aspects:(1)more ears per unit area and more grains per ear,higher seed setting rate and bigger ear;(2)full growth and harmonic development of yield organs due to the long growth duration and favorable photo-thermal conditions in those areas;(3)higher rate of photosynthesis,more dry matter accumulation,and harmonic relation between sink and source.The formation of these characteristics is closely related to the u nique climatic ecological environment in the plateau and the rice cultivation and management.

  13. The Manihiki Plateau, Hikurangi Plateau, Wishbone Scarp, and Osbourn Trough: A Review and Analysis

    Science.gov (United States)

    Henig, A.; Luyendyk, B. P.

    2007-12-01

    The extinct Osbourn Trough spreading system in the southwestern Pacific played a key role in separating the once joined Hikurangi and Manihiki Plateaus in Cretaceous time. Recent studies by Downey et al. [2007] and Taylor [20006] have provided new data and concepts on that history. Studies by Larson et al. [2002] describe Cretaceous histories adjacent and east of the Osbourn system and Eagles et al. [2004] describe a history for the southwest Pacific just after the Osbourn system became extinct. The lack of identifiable magnetic anomalies allows tectonic events during separation of the plateaus and spreading on the Osbourn Trough to occur between about 124.6 and 84 Ma (Chron 34). Satellite gravity maps of the region identify what are interpreted as Cretaceous fracture zone trends. Swath bathymetry data reveal at least four provinces of abyssal hill trends. What is known are the following: Minimum age of the Manihiki High Plateau at 123.4 Ma from DSDP Site 317, the age of seafloor, 115 Ma, from a dredge sample from the southern segment of the West Wishbone Scarp 300 km northeast of the Hikurangi Plateau, the east-west trend and extent of the extinct Osbourn spreading center at latitude 26° S, the trends (NNE-SSW to NE-SW) and extent of portions of the West Wishbone Scarp east of the Hikurangi Plateau, the N-S trend of the East Wishbone Scarp that appears to truncate the West Wishbone Scarp, the NNE- SSW trend and extent of the prominent Manihiki (Eastern) Scarp at the eastern boundary of the Manihiki High Plateau, the NW-SE trend and extent of the Rapuhia Scarp on the northwestern Hikurangi Plateau, and trends in abyssal hills; E-W near the Osbourn Trough and WNW-ESE closer to the plateaus. Differences in abyssal hill morphology suggest one or more changes in spreading rates. The Osbourn Trough began rifting apart a Large Igneous Province formed at 123.5 +/- 1.5 Ma, into the separate Ontong-Java, Manihiki, and Hikurangi Plateaus by 121 Ma. After an initial 6 Myr

  14. Antarctic Ice-Sheet Mass Balance from Satellite Altimetry 1992 to 2001

    Science.gov (United States)

    Zwally, H. Jay; Brenner, Anita C.; Cornejo, Helen; Giovinetto, Mario; Saba, Jack L.; Yi, Donghui

    2003-01-01

    A major uncertainty in understanding the causes of the current rate of sea level rise is the potential contributions from mass imbalances of the Greenland and Antarctic ice sheets. Estimates of the current mass balance of the Antarctic ice sheet are derived from surface- elevation changes obtained from 9 years of ERS - 1 & 2 radar altimeter data. Elevation time-series are created from altimeter crossovers among 90-day data periods on a 50 km grid to 81.5 S. The time series are fit with a multivariate linear/sinusoidal function to give the average rate of elevation change (dH/dt). On the major Rome-Filchner, Ross, and Amery ice shelves, the W d t are small or near zero. In contrast, the ice shelves of the Antarctic Peninsula and along the West Antarctic coast appear to be thinning significantly, with a 23 +/- 3 cm per year surface elevation decrease on the Larsen ice shelf and a 65 +/- 4 cm per year decrease on the Dotson ice shelf. On the grounded ice, significant elevation decreases are obtained over most of the drainage basins of the Pine Island and Thwaites glaciers in West Antarctica and inland of Law Dome in East Antarctica. Significant elevation increases are observed within about 200 km of the coast around much of the rest of the ice sheet. Farther inland, the changes are a mixed pattern of increases and decreases with increases of a few centimeters per year at the highest elevations of the East Antarctic plateau. The derived elevation changes are combined with estimates of the bedrock uplift from several models to provide maps of ice thickness change. The ice thickness changes enable estimates of the ice mass balances for the major drainage basins, the overall mass balance, and the current contribution of the ice sheet to global sea level change.

  15. Investigation of surface ozone variability over the Antractic Plateau by observations at the "Concordia" WMO/GAW contributing station

    Science.gov (United States)

    Cristofanelli, Paolo; Udisti, Roberto; Busetto, Maurizio; Calzolari, Francescopiero; Putero, Davide; Lupi, Angelo; Mazzola, Mauro; Petkov, Boyan; Bonasoni, Paolo

    2017-04-01

    Tropospheric ozone (O3), is a greenhouse gas and a driver for atmosphere oxidative capacity. It has at least doubled since pre-industrial age but a comprehensive understanding of the global distribution and trends are difficult to achieve due to its reactivity. Measurements at Antarctic locations provide the opportunity to investigate O3 variability without direct anthropogenic influence providing information on its background variability. This work will focus on the investigation of the variability of surface tropospheric O3 over the eastern Antarctic Plateau. In particular, we will analyze seven years (2006 - 2013) of continuous observations at the WMO/GAW Contributing Station Concordia (75.10°S, 123.33°E, 3233m a.s.l. m) with the purpose of shading light on specific atmospheric processes that need to be accurately taken into account for interpreting O3 variability: (i) in-situ NOx emissions and subsequent photochemical O3 production during summer, (ii) long-range transport of air-masses enriched in O3 by photochemical production over the surface of Antarctic Plateau, (iii) long-range transport of air-masses depleted in O3 from coastal regions or open oceans. Moreover, even if their influence is expected to be limited, the possible influence of STE will be specifically investigated. To this aims, in-situ O3 variability will be analyzed as a function of 3D air-mass back-trajectories calculated by the HYSPLIT and FLEXTRA models. Co-variability with meteorological parameters and other atmospheric tracers (e.g. aerosol measurement as a function of key source and transport processes) will be also studied in order to provide a preliminary assessment of their impact on O3 variability. The STEFLUX (Stratosphere-to-Troposphere Exchange Flux) tool will be used to investigate the influence of stratosphere-to-troposphere transport on ozone variability over eastern Antarctic Plateau.

  16. Evidence for widespread endemism among Antarctic micro-organisms

    Science.gov (United States)

    Vyverman, Wim; Verleyen, Elie; Wilmotte, Annick; Hodgson, Dominic A.; Willems, Anne; Peeters, Karolien; Van de Vijver, Bart; De Wever, Aaike; Leliaert, Frederik; Sabbe, Koen

    2010-08-01

    Understanding the enormous diversity of microbes, their multiple roles in the functioning of ecosystems, and their response to large-scale environmental and climatic changes, are at the forefront of the international research agenda. In Antarctica, where terrestrial and lacustrine environments are predominantly microbial realms, an active and growing community of microbial ecologists is probing this diversity and its role in ecosystem processes. In a broader context, this work has the potential to make a significant contribution to the long-standing debate as to whether microbes are fundamentally different from macroorganisms in their biogeography. According to the ubiquity hypothesis, microbial community composition is not constrained by dispersal limitation and is solely the result of species sorting along environmental gradients. However, recent work on several groups of microalgae is challenging this view. Global analyses using morphology-based diatom inventories have demonstrated that, in addition to environmental harshness, geographical isolation underlies the strong latitudinal gradients in local and regional diversity in the Southern hemisphere. Increasing evidence points to a strong regionalization of diatom floras in the Antarctic and sub-Antarctic regions, mirroring the biogeographical regions that have been recognized for macroorganisms. Likewise, the application of molecular-phylogenetic techniques to cultured and uncultured diversity revealed a high number of Antarctic endemics among cyanobacteria and green algae. Calibration of these phylogenies suggests that several clades have an ancient evolutionary history within the Antarctic continent, possibly dating back to 330 Ma. These findings are in line with the current view on the origin of Antarctic terrestrial metazoa, including springtails, chironomids and mites, with most evidence suggesting a long history of geographic isolation on a multi-million year, even pre-Gondwana break-up timescale.

  17. Genetics differentiation between Arctic and Antarctic monothalamous foraminiferans

    DEFF Research Database (Denmark)

    Pawlowski, Jan; Majewski, Wojciech; Longet, David

    2008-01-01

    Monothalamous (single-chambered) foraminifers are a major component of the benthic meiofauna in high latitude regions. Several morphologically similar species are common in the Arctic and Antarctic. However, it is uncertain whether these morphospecies are genetically identical, or whether...... from Norwegian fjords. Our study has revealed a high number of cryptic species within each of the examined genera, and demonstrates the unexplored potential of monothalamous foraminifers for use as a tool to evaluate the origin and biogeography of polar meiofauna....

  18. Carbon dioxide emissions of Antarctic tourism

    NARCIS (Netherlands)

    Farreny, R.; Oliver-Solà, J.; Lamers, M.A.J.; Amelung, B.; Gabarrell, X.; Rieradevall, J.; Boada, M.; Benayas, J.

    2011-01-01

    The increase of tourism to the Antarctic continent may entail not only local but also global environmental impacts. These latter impacts, which are mainly caused by transport, have been generally ignored. As a result, there is a lack of data on the global impacts of Antarctic tourism in terms of

  19. South African antarctic biological research programme

    CSIR Research Space (South Africa)

    SASCAR

    1981-07-01

    Full Text Available This document provides a description of the past, current and planned South African biological research activities in the sub-Antarctic and Antarctic regions. Future activities will fall under one of the five components of the research programme...

  20. JCADM, new directions in Antarctic data management

    Science.gov (United States)

    Campbell, H.; de Bruin, T. F.

    2008-12-01

    The Joint Committee on Antarctic Data Management (JCADM) was established by the Scientific Committee on Antarctic Research (SCAR) and the Council of Managers of National Antarctic Programs (COMNAP), to assist in the fulfilment of the data management obligations imposed by the Antarctic Treaty (section III.1.c): "Scientific observations and results from Antarctica shall be exchanged and made freely available." JCADM comprises representatives of the National Antarctic Data Centres or national points of contact. Currently 31 nations around the world are represented in JCADM. So far, JCADM has been focussing on the coordination of the Antarctic Master Directory (AMD), the internationally accessible, web-based, searchable record of Antarctic and Southern Ocean data set descriptions. The AMD is directly integrated into the international Global Change Master Directory (GCMD) to help further merge Antarctic science into global science. The AMD is a resource for scientists to advertise the data they have collected and to search for data they may need. Currently, JCADM is in a transition phase, moving forward to provide data access. Existing systems and web services technology will be used as much as possible, to increase efficiency and prevent 're-inventing the wheel' This poster will give an overview of this process, the current status and the expected results.

  1. Impact of climate change on Antarctic krill

    NARCIS (Netherlands)

    Florentino De Souza Silva, A.P.; Atkinson, A.; Kawaguchi, S.; Bravo Rebolledo, E.; Franeker, van J.A.

    2012-01-01

    Antarctic krill Euphausia superba (hereafter ‘krill’) occur in regions undergoing rapid environmental change, particularly loss of winter sea ice. During recent years, harvesting of krill has increased, possibly enhancing stress on krill and Antarctic ecosystems. Here we review the overall impact of

  2. Impact of climate change on Antarctic krill

    NARCIS (Netherlands)

    Florentino De Souza Silva, A.P.; Atkinson, A.; Kawaguchi, S.; Bravo Rebolledo, E.; Franeker, van J.A.

    2012-01-01

    Antarctic krill Euphausia superba (hereafter ‘krill’) occur in regions undergoing rapid environmental change, particularly loss of winter sea ice. During recent years, harvesting of krill has increased, possibly enhancing stress on krill and Antarctic ecosystems. Here we review the overall impact of

  3. Mid-Miocene thermal Impact on the Lithosphere of Asia by sub-lithospheric convective Mantle Material: Temporal Transition from high- to moderate-Mg Magmatism beneath Vitim Plateau, Southern Siberia

    Science.gov (United States)

    Chuvashova, Irina; Rasskazov, Sergei

    2015-04-01

    In Inner Asia, high-Mg lavas is characteristic of the Middle Miocene volcanism. In the Vitim plateau, we studied the high- and moderate-Mg volcanics, erupted at 16-14 and 14-13 Ma, respectively. In the former (small volume) unit, initial basaltic melts, contaminated by crustal material, were followed by uncontaminated high-Mg basanites and basalts of transitional (K-Na-K) compositions and afterwards by picrobasalts and basalts of K series. In the latter (high-volume) unit, initial basalts and basaltic andesites of transitional (Na-K-Na) compositions and basalts of Na series were overlain by basalts and trachybasalts of K-Na series. From pressure estimates after equation [Scarrow, Cox, 1995], we infer that the high-Mg melts were derived from the sub-lithospheric mantle as deep as 115-150 km, unlike the moderate-Mg ones that were produced by melting of the shallow lithospheric mantle. We suggest that the studied transition from high- and moderate-Mg magmatism reflected the mid-Miocene thermal impact on the lithosphere by a hot sub-lithospheric mantle material from the Transbaikalian low-velocity domain with potential temperature estimates up to 1510 oC. This thermal impact triggered rifting in the lithosphere of the Baikal Rift System. The study is supported by the Russian Foundation for Basic Research (Grant 14-05-31328).

  4. Genetic population structure in the Antarctic benthos: insights from the widespread amphipod, Orchomenella franklini.

    Science.gov (United States)

    Baird, Helena Phoenix; Miller, Karen Joy; Stark, Jonathan Sean

    2012-01-01

    Currently there is very limited understanding of genetic population structure in the Antarctic benthos. We conducted one of the first studies of microsatellite variation in an Antarctic benthic invertebrate, using the ubiquitous amphipod Orchomenella franklini (Walker, 1903). Seven microsatellite loci were used to assess genetic structure on three spatial scales: sites (100 s of metres), locations (1-10 kilometres) and regions (1000 s of kilometres) sampled in East Antarctica at Casey and Davis stations. Considerable genetic diversity was revealed, which varied between the two regions and also between polluted and unpolluted sites. Genetic differentiation among all populations was highly significant (F(ST) = 0.086, R(ST) = 0.139, pbenthos. These results provide insights into processes of speciation in Antarctic brooders, and will help inform the design of spatial management initiatives recently endorsed for the Antarctic benthos.

  5. Spiny Neurons of Amygdala, Striatum and Cortex Use Dendritic Plateau Potentials to Detect Network UP States

    Directory of Open Access Journals (Sweden)

    Katerina D Oikonomou

    2014-09-01

    Full Text Available Spiny neurons of amygdala, striatum, and cerebral cortex share four interesting features: [1] they are the most abundant cell type within their respective brain area, [2] covered by thousands of thorny protrusions (dendritic spines, [3] possess high levels of dendritic NMDA conductances, and [4] experience sustained somatic depolarizations in vivo and in vitro (UP states. In all spiny neurons of the forebrain, adequate glutamatergic inputs generate dendritic plateau potentials (dendritic UP states characterized by (i fast rise, (ii plateau phase lasting several hundred milliseconds and (iii abrupt decline at the end of the plateau phase. The dendritic plateau potential propagates towards the cell body decrementally to induce a long-lasting (longer than 100 ms, most often 200 – 800 ms steady depolarization (~20 mV amplitude, which resembles a neuronal UP state. Based on voltage-sensitive dye imaging, the plateau depolarization in the soma is precisely time-locked to the regenerative plateau potential taking place in the dendrite. The somatic plateau rises after the onset of the dendritic voltage transient and collapses with the breakdown of the dendritic plateau depolarization. We hypothesize that neuronal UP states in vivo reflect the occurrence of dendritic plateau potentials (dendritic UP states. We propose that the somatic voltage waveform during a neuronal UP state is determined by dendritic plateau potentials. A mammalian spiny neuron uses dendritic plateau potentials to detect and transform coherent network activity into a ubiquitous neuronal UP state. The biophysical properties of dendritic plateau potentials allow neurons to quickly attune to the ongoing network activity, as well as secure the stable amplitudes of successive UP states.

  6. Divergent trajectories of Antarctic surface melt under two twenty-first-century climate scenarios

    Science.gov (United States)

    Trusel, Luke D.; Frey, Karen E.; Das, Sarah B.; Karnauskas, Kristopher B.; Kuipers Munneke, Peter; van Meijgaard, Erik; van den Broeke, Michiel R.

    2015-12-01

    Ice shelves modulate Antarctic contributions to sea-level rise and thereby represent a critical, climate-sensitive interface between the Antarctic ice sheet and the global ocean. Following rapid atmospheric warming over the past decades, Antarctic Peninsula ice shelves have progressively retreated, at times catastrophically. This decay supports hypotheses of thermal limits of viability for ice shelves via surface melt forcing. Here we use a polar-adapted regional climate model and satellite observations to quantify the nonlinear relationship between surface melting and summer air temperature. Combining observations and multimodel simulations, we examine melt evolution and intensification before observed ice shelf collapse on the Antarctic Peninsula. We then assess the twenty-first-century evolution of surface melt across Antarctica under intermediate and high emissions climate scenarios. Our projections reveal a scenario-independent doubling of Antarctic-wide melt by 2050. Between 2050 and 2100, however, significant divergence in melt occurs between the two climate scenarios. Under the high emissions pathway by 2100, melt on several ice shelves approaches or surpasses intensities that have historically been associated with ice shelf collapse, at least on the northeast Antarctic Peninsula.

  7. Heterolobosean amoebae from Arctic and Antarctic extremes: 18 novel strains of Allovahlkampfia, Vahlkampfia and Naegleria.

    Science.gov (United States)

    Tyml, Tomáš; Skulinová, Kateřina; Kavan, Jan; Ditrich, Oleg; Kostka, Martin; Dyková, Iva

    2016-10-01

    The diversity of heterolobosean amoebae, important members of soil, marine and freshwater microeukaryote communities in the temperate zones, is greatly under-explored in high latitudes. To address this imbalance, we studied the diversity of this group of free-living amoebae in the Arctic and the Antarctic using culture dependent methods. Eighteen strain representatives of three heterolobosean genera, Allovahlkampfia Walochnik et Mulec, 2009 (1 strain), Vahlkampfia Chatton et Lalung-Bonnaier, 1912 (2) and Naegleria Alexeieff, 1912 (15) were isolated from 179 samples of wet soil and fresh water with sediments collected in 6 localities. The Allovahkampfia strain is the first representative of the genus from the Antarctic; 14 strains (7 from the Arctic, 7 from the Antarctic) of the highly represented genus Naegleria complete the 'polar' cluster of five Naegleria species previously known from the Arctic and Sub-Antarctic regions, whereas one strain enriches the 'dobsoni' cluster of Naegleria strains of diverse origin. Present isolations of Naegleria polarisDe Jonckheere, 2006 from Svalbard, in the Arctic and Vega Island, in the Antarctic and N. neopolarisDe Jonckheere, 2006 from Svalbard and Greenland in the Arctic, and James Ross Island, the Antarctic demonstrate their bipolar distribution, which in free-living amoebae has so far only been known for Vermistella Morand et Anderson, 2007.

  8. Notes on Antarctic Aviation

    Science.gov (United States)

    1993-08-01

    thickness. Theoretically the maximum allowable original brine cells become interconnected at "high" "point" load is proportional to the ice thickness...produce hydrogen by electrolysis at avoid unproductive duplication of facilities. At remote sites in the interior of Antarctica. McMurdo, for example

  9. Bellingshausen Sea ice extent recorded in an Antarctic Peninsula ice core

    Science.gov (United States)

    Porter, Stacy E.; Parkinson, Claire L.; Mosley-Thompson, Ellen

    2016-12-01

    Annual net accumulation (An) from the Bruce Plateau (BP) ice core retrieved from the Antarctic Peninsula exhibits a notable relationship with sea ice extent (SIE) in the Bellingshausen Sea. Over the satellite era, both BP An and Bellingshausen SIE are influenced by large-scale climatic factors such as the Amundsen Sea Low, Southern Annular Mode, and Southern Oscillation. In addition to the direct response of BP An to Bellingshausen SIE (e.g., more open water as a moisture source), these large-scale climate phenomena also link the BP and the Bellingshausen Sea indirectly such that they exhibit similar responses (e.g., northerly wind anomalies advect warm, moist air to the Antarctic Peninsula and neighboring Bellingshausen Sea, which reduces SIE and increases An). Comparison with a time series of fast ice at South Orkney Islands reveals a relationship between BP An and sea ice in the northern Weddell Sea that is relatively consistent over the twentieth century, except when it is modulated by atmospheric wave patterns described by the Trans-Polar Index. The trend of increasing accumulation on the Bruce Plateau since 1970 agrees with other climate records and reconstructions in the region and suggests that the current rate of sea ice loss in the Bellingshausen Sea is unrivaled in the twentieth century.

  10. Imprint of a dissolved cobalt basaltic source on the Kerguelen Plateau

    NARCIS (Netherlands)

    Bown, J.; Boye, M.; Laan, P.; Bowie, A.R.; Park, Y.H.; Jeandel, C.; Nelson, D.M.

    2012-01-01

    Processes of cobalt (Co) entrainment from shelf sediments over the Kerguelen Plateau were studied during the KEOPS (Kerguelen Ocean Plateau compared Study) in order to explain the exceptionally high dissolved cobalt concentrations that have been measured in the surface waters above the Kerguelen Pla

  11. The 1988 Antarctic ozone depletion - Comparison with previous year depletions

    Science.gov (United States)

    Schoeberl, Mark R.; Stolarski, Richard S.; Krueger, Arlin J.

    1989-01-01

    The 1988 spring Antarctic ozone depletion was observed by TOMS to be substantially smaller than in recent years. The minimum polar total ozone values declined only 15 percent during September 1988, compared to nearly 50 percent during September 1987. At southern midlatitudes, exceptionally high total ozone values were recorded beginning in July 1988. The total integrated southern hemispheric ozone increased rapidly during the Austral spring, approaching 1980 levels during October. The high midlatitude total ozone values were associated with a substantial increase in eddy activity as indicated by the standard deviation in total ozone in the zonal band 30-60 deg S. Mechanisms through which the increased midlatitude eddy activity could disrupt the formation of the Antarctic ozone hole are briefly discussed.

  12. Verçenik Plateau Alternative Tourism and Recreational Activities

    Directory of Open Access Journals (Sweden)

    İzzet İSLAMOĞLU

    2014-08-01

    Full Text Available In the last century working life become easier and result of this increased people free time, after that interest of tourism activities wide spread all over. Plateau tourism or highland places are not first choices of the tourism activities but plateau rec reation will give an application for potential activity place. Turkey have unmatched nature and rich environmental resources will able to give any kind of tourism activities. In that context city of Rize took place in Black Sea region with different capabi lities, one of the source areas that make up tourism and recreational activities. This research intended for Vercenik Plateau take place 60 km away from Camlihemsin district center and will determine potential tourism and recreational application. Research is based on field observation and studies. This information obtained as a result ofthis evaluationbeing associated toliterature data and that information determined which exercise can be done in the field. Vercenik Plateau; with pristine environment and ru ral locations, the fresh water supplies, unique flora for city of Rize has high recreational capacities.As a result of study; Vercenik Plateau has natural features with the great potential of the alternative tourism as it is suitable for areas but not asse ss enough potential tourism and recreational activities without prior review has been observed.

  13. Jang Bogo Antarctic Ionosonde

    Science.gov (United States)

    Bullett, Terry; Jee, Geonhwa; Livingston, Robert; Kim, Jeong-Han; Zabotin, Nikolay; Lee, Chang-Sup; Grubb, Richard; Mabie, Justin; Kwon, Hyuck-Jin

    2016-04-01

    The Korean Polar Research Institute has established the Jang Bogo research station in Antarctica on Terra Nova Bay (74.62°S, 164.23°E). One of the space environment sensors installed in 2014 is a world class research ionosonde facility consisting of a Vertical Incidence Pulsed Ionospheric Radar (VIPIR) with Dynasonde signal processing. The VIPIR is an MF/HF radar oeprating from 0.5 to 25 MHz. The transmit antenna is a 36x75x75m dual vertical incidence log periodic design and the receive antenna is a 70x70m array of 8 orthogonal 4m active dipoles attached to 8 coherent digital receivers. Full resolution In-Phase and Quadrature data are recorded for post analysis. The low atmospheric noise and low interference combine with the high system performance to produce ionogram data of very high quality and allow measurements with high time resolution. The 2015 data were taken using the first generation VIPIR electronics on loan from Boulder. Antenna repairs and the installation of the second generation VIPIR electronics were completed at the end of 2015. Phase based Dynasonde analysis techniques are applied to the VIPIR data to perform echo detection and to derive electron density profiles and velocity vectors.

  14. Arctic and Antarctic sea ice and climate

    Science.gov (United States)

    Barreira, S.

    2014-12-01

    Principal Components Analysis in T-Mode Varimax rotated was performed on Antarctic and Arctic monthly sea ice concentration anomalies (SICA) fields for the period 1979-2014, in order to investigate which are the main spatial characteristics of sea ice and its relationship with atmospheric circulation. This analysis provides 5 patterns of sea ice for inter-spring period and 3 patterns for summer-autumn for Antarctica (69,2% of the total variance) and 3 different patterns for summer-autumn and 3 for winter-spring season for the Arctic Ocean (67,8% of the total variance).Each of these patterns has a positive and negative phase. We used the Monthly Polar Gridded Sea Ice Concentrations database derived from satellite information generated by NASA Team algorithm. To understand the links between the SICA and climate trends, we extracted the mean pressure and, temperature field patterns for the months with high loadings (positive or negative) of the sea ice patterns that gave distinct atmospheric structures associated with each one. For Antarctica, the first SICA spatial winter-spring pattern in positive phase shows a negative SICA centre over the Drake Passage and north region of Bellingshausen and Weddell Seas together with another negative SICA centre over the East Indian Ocean. Strong positive centres over the rest of the Atlantic and Indian Oceans basins and the Amundsen Sea are also presented. A strong negative pressure anomaly covers most of the Antarctic Continent centered over the Bellingshausen Sea accompanied by three positive pressure anomalies in middle-latitudes. During recent years, the Arctic showed persistent associations of sea-ice and climate patterns principally during summer. Our strongest summer-autumn pattern in negative phase showed a marked reduction on SICA over western Arctic, primarily linked to an overall increase in Arctic atmospheric temperature most pronounced over the Beaufort, Chukchi and East Siberian Seas, and a positive anomaly of

  15. Morphogenesis of Antarctic Paleosols: Martian Analogue

    Science.gov (United States)

    Mahaney, W. C.; Dohm, J. M.; Baker, V. R.; Newsom, Horton E.; Malloch, D.; Hancock, R. G. V.; Campbell, Iain; Sheppard, D.; Milner, M. W.

    2001-11-01

    Samples of horizons in paleosols from the Quartermain Mountains of the Antarctic Dry Valleys (Aztec and New Mountain areas) were analyzed for their physical characteristics, mineralogy, chemical composition, and microbiology to determine the accumulation and movement of salts and other soluble constituents and the presence/absence of microbial populations. Salt concentrations are of special interest because they are considered to be a function of age, derived over time, in part from nearby oceanic and high-altitude atmospheric sources. The chemical composition of ancient Miocene-age paleosols in these areas is the direct result of the deposition and weathering of airborne-influxed salts and other materials, as well as the weathering of till derived principally from local dolerite and sandstone outcrops. Paleosols nearer the coast have greater contents of Cl, whereas near the inland ice sheet, nitrogen tends to increase on a relative basis. The accumulation and vertical distribution of salts and other soluble chemical elements indicate relative amounts of movement in the profile over long periods of time, in the order of several million years. Four of the six selected subsamples from paleosol horizons in two ancient soil profiles contained nil concentrations of bacteria and fungi. However, two horizons at depths of between 3 and 8 cm, in two profiles, yielded several colonies of the fungi Beauveria bassiana and Penicillium brevicompactum, indicating very minor input of organic carbon. Beauveria bassiana is often reported in association with insects and is used commercially for the biological control of some insect pests. Penicillium species are commonly isolated from Arctic, temperate, and tropical soils and are known to utilize a wide variety of organic carbon and nitrogen compounds. The cold, dry soils of the Antarctic bear a close resemblance to various present and past martian environments where similar weathering could occur and possible microbial populations

  16. Viable Bacteria in Antarctic Soils and - Two Models for Extraterrestrial Search of Life

    Science.gov (United States)

    Soina, Vera; Vorobyova, Elena; Lysak, Ludmila; Mergelov, Nikita

    Antarctic soils and permafrost are the most convenient models for search life preservation in extraterrestrial cryogenic environment. Study of life activity and preservation of prokaryotes in such extreme environment allow assuming, that those habitats must be viewed as two models for astrobiology extrapolations. Antarctic permafrost due to long term freezing can be regarded as the most stable environment for life preservation and expanding of potential physiological cell activity due to stabilization of cell structures and biomolecules. Antarctic soils seem to be not less attractive as a model for study of life on the surface of Antarctic rocks, but in contrast to permafrost are characterized by less stable external factors. Presumably, it is due to changing cycles of freezing and thawing and high doses of UV radiation, that make such biotopes more extreme for microbial survival. A combination of culture- depended and - independent techniques, including SEM and TEM methods were used to characterize bacteria community in earlier not investigated Antarctic soils in the oases of Larsemann Hills (East Antarctic Coast). Several important characteristics of Antarctic soil and permafrost bacteria as models for possible signs of life in extraterrestrial habitats are discussed (cytomorphological and physiological characteristics of bacteria both in situ, and cells isolated from permafrost and exposed to various external stress factors). Our data indicate that significant discrepancy between indexes of total and viable number of cells and irregularity of such indexes in horizons of developing soils and permafrost sediments can be explained by specification of physical and chemical processes in those habitats. Also, in Antarctic and extraterrestrial investigations is important to take into account the leading role of microbial biofilms, where microorganisms are intimately associated with each other and mineral particles through binding and inclusion within exopolymer matrix

  17. Hydrocarbon degradation by antarctic bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Cavanagh, J.A.E.; Nichols, P.D.; McMeekin, T.A.; Franzmann, P.D. [Univ. of Tasmania (Australia)] [and others

    1996-12-31

    Bacterial cultures obtained from sediment samples collected during a trial oil spill experiment conducted at Airport beach, Eastern Antarctica were selectively enriched for n-alkane-degrading and phenanthrenedegrading bacteria. Samples were collected from a control site and sites treated with different hydrocarbon mixtures - Special Antarctic blend (SAB), BP-Visco and orange roughy oils. One set of replicate sites was also treated with water from Organic Lake which had previously been shown to contain hydrocarbon-degrading bacteria. No viable bacteria were obtained from samples collected from sites treated with orange roughy oil. Extensive degradation of n-alkanes by enrichment cultures obtained from sites treated with SAB and BP-Visco occurred at both 25{degrees}C and 10{degrees}C. Extensive degradation of phenanthrene also occurred in enrichment cultures from these sites grown at 25{degrees}C. Concurrent increases of polar lipid in these cultures were also observed. The presence of 1,4-naphthaquinone and 1-naphthol during the growth of the cultures on phenanthrene is unusual and warrants further investigation of the mechanism of phenanthrene-degradation by these Antarctic bacteria.

  18. Lake overspill and onset of fluvial incision in the Iranian Plateau: Insights from the Mianeh Basin

    Science.gov (United States)

    Heidarzadeh, Ghasem; Ballato, Paolo; Hassanzadeh, Jamshid; Ghassemi, Mohammad R.; Strecker, Manfred R.

    2017-07-01

    Orogenic plateaus represent a prime example of the interplay between surface processes, climate, and tectonics. This kind of an interplay is thought to be responsible for the formation, preservation, and, ultimately, the destruction of a typical elevated, low-internal relief plateau landscape. Here, we document the timing of intermontane basin filling associated with the formation of a low-relief plateau morphology, followed by basin opening and plateau-flank incision in the northwestern Iranian Plateau of the Arabia-Eurasia collision zone. Our new U-Pb zircon ages from intercalated volcanic ashes in exposed plateau basin-fill sediments from the most external plateau basin (Mianeh Basin) document that the basin was internally drained at least between ∼7 and 4 Ma, and that from ∼5 to 4 Ma it was characterized by an ∼2-km-high and ∼0.5-km-deep lake (Mianeh paleolake), most likely as a result of wetter climatic conditions. At the same time, the eastern margin of the Mianeh Basin (and, therefore, of the Iranian Plateau) experienced limited tectonic activity, as documented by onlapping sediments and smoothed topography. The combination of high lake level and subdued topography at the plateau margin led to lake overspill, which resulted in the cutting of an ∼1-km-deep bedrock gorge (Amardos) by the Qezel-Owzan River (QOR) beginning at ∼4 Ma. This was associated with the incision of the plateau landscape and the establishment of fluvial connectivity with the Caspian Sea. Overall, our study emphasizes the interplay between surface and tectonic processes in forming, maintaining, and destroying orogenic plateau morphology, the transitional nature of orogenic plateau landscapes on timescales of 106 yr, and, finally, the role played by overspilling in integrating endorheic basins.

  19. ANALYSIS OF MESOSCALE CONVECTIVE SYSTEMS OVER TIBETAN PLATEAU IN SUMMER

    Institute of Scientific and Technical Information of China (English)

    GUO Zhong-yang; DAI Xiao-yan; WU Jian-ping; LIN Hui

    2006-01-01

    In this paper, Geostationary Meteorological Satellite (GMS) infrared black-body temperature (Tbb) data from June to August 1998 are used to automatically track the activity of Mesoscale Convective System (MCS) over the Tibetan Plateau in China. Consequently, the features of MCS, such as area, intensity, life cycle, activity region and shape, are obtained. High Resolution Limited Area Analysis and Forecasting System (HLAFS) values provided by China National Meteorological Center are used to study the relationships between the MCS trajectories and their environmental physical field values, based on the distribution and trajectories of MCSs over the Tibetan Plateau. Favorable environmental physical field charts of influencing MCS movement out of the Tibetan Plateau in different UTC (Universal Time Coordinate) are developed by using spatial data mining techniques at levels of 400hPa and 500hPa, respectively.

  20. Fukushima nuclear accident recorded in Tibetan Plateau snow pits.

    Directory of Open Access Journals (Sweden)

    Ninglian Wang

    Full Text Available The β radioactivity of snow-pit samples collected in the spring of 2011 on four Tibetan Plateau glaciers demonstrate a remarkable peak in each snow pit profile, with peaks about ten to tens of times higher than background levels. The timing of these peaks suggests that the high radioactivity resulted from the Fukushima nuclear accident that occurred on March 11, 2011 in eastern Japan. Fallout monitoring studies demonstrate that this radioactive material was transported by the westerlies across the middle latitudes of the Northern Hemisphere. The depth of the peak β radioactivity in each snow pit compared with observational precipitation records, suggests that the radioactive fallout reached the Tibetan Plateau and was deposited on glacier surfaces in late March 2011, or approximately 20 days after the nuclear accident. The radioactive fallout existed in the atmosphere over the Tibetan Plateau for about one month.

  1. Shifts in soil microorganisms in response to warming are consistent across a range of Antarctic environments.

    Science.gov (United States)

    Yergeau, Etienne; Bokhorst, Stef; Kang, Sanghoon; Zhou, Jizhong; Greer, Charles W; Aerts, Rien; Kowalchuk, George A

    2012-03-01

    Because of severe abiotic limitations, Antarctic soils represent simplified systems, where microorganisms are the principal drivers of nutrient cycling. This relative simplicity makes these ecosystems particularly vulnerable to perturbations, like global warming, and the Antarctic Peninsula is among the most rapidly warming regions on the planet. However, the consequences of the ongoing warming of Antarctica on microorganisms and the processes they mediate are unknown. Here, using 16S rRNA gene pyrosequencing and qPCR, we report highly consistent responses in microbial communities across disparate sub-Antarctic and Antarctic environments in response to 3 years of experimental field warming (+0.5 to 2 °C). Specifically, we found significant increases in the abundance of fungi and bacteria and in the Alphaproteobacteria-to-Acidobacteria ratio, which could result in an increase in soil respiration. Furthermore, shifts toward generalist bacterial communities following warming weakened the linkage between the bacterial taxonomic and functional richness. GeoChip microarray analyses also revealed significant warming effects on functional communities, specifically in the N-cycling microorganisms. Our results demonstrate that soil microorganisms across a range of sub-Antarctic and Antarctic environments can respond consistently and rapidly to increasing temperatures.

  2. Ice core and climate reanalysis analogs to predict Antarctic and Southern Hemisphere climate changes

    Science.gov (United States)

    Mayewski, P. A.; Carleton, A. M.; Birkel, S. D.; Dixon, D.; Kurbatov, A. V.; Korotkikh, E.; McConnell, J.; Curran, M.; Cole-Dai, J.; Jiang, S.; Plummer, C.; Vance, T.; Maasch, K. A.; Sneed, S. B.; Handley, M.

    2017-01-01

    A primary goal of the SCAR (Scientific Committee for Antarctic Research) initiated AntClim21 (Antarctic Climate in the 21st Century) Scientific Research Programme is to develop analogs for understanding past, present and future climates for the Antarctic and Southern Hemisphere. In this contribution to AntClim21 we provide a framework for achieving this goal that includes: a description of basic climate parameters; comparison of existing climate reanalyses; and ice core sodium records as proxies for the frequencies of marine air mass intrusion spanning the past ∼2000 years. The resulting analog examples include: natural variability, a continuation of the current trend in Antarctic and Southern Ocean climate characterized by some regions of warming and some cooling at the surface of the Southern Ocean, Antarctic ozone healing, a generally warming climate and separate increases in the meridional and zonal winds. We emphasize changes in atmospheric circulation because the atmosphere rapidly transports heat, moisture, momentum, and pollutants, throughout the middle to high latitudes. In addition, atmospheric circulation interacts with temporal variations (synoptic to monthly scales, inter-annual, decadal, etc.) of sea ice extent and concentration. We also investigate associations between Antarctic atmospheric circulation features, notably the Amundsen Sea Low (ASL), and primary climate teleconnections including the SAM (Southern Annular Mode), ENSO (El Nîno Southern Oscillation), the Pacific Decadal Oscillation (PDO), the AMO (Atlantic Multidecadal Oscillation), and solar irradiance variations.

  3. [Resistance to UV radiation of microorganisms isolated from the rock biotopes of the Antarctic region].

    Science.gov (United States)

    Romanovskaia, V A; Tashirev, A B; Shilin, S O; Chernaia, N A

    2010-01-01

    Microbiological analysis of terrestrial biotopes of the Antarctic Region has shown, that vertical rocks of the Antarctic islands open for the Sun were characterized by special microcenoses. The wide distribution of pigmented microorganisms in the rock Antarctic samples, a higher frequency of their occurrence, the total number and biologic diversity, than in other Antarctic biotopes, has been demonstrated. For the first time the presence of bacteria and yeast, resistant to high doses of UV radiation on the vertical rocks in the Antarctic Region was shown. The lethal doze of UV radiation for the Antarctic pink pigmented Methylobacterium strains exceeded 200-300 J/m2, for coal-black yeast--500-800 J/m2, for red yeast--1200-1500 J/m2. The distinctions in lethal UV effect against strains of Methylobacterium isolated from the regions with different climate have not been found. Probably, adaptation of the rock microcenosis to extreme factors of the environment proceeds by natural selection of microorganisms, which resistance to this factor is genetically determined.

  4. Unrecognized Antarctic biodiversity: a case study of the genus Odontaster (Odontasteridae; Asteroidea).

    Science.gov (United States)

    Janosik, Alexis M; Halanych, Kenneth M

    2010-12-01

    Antarctica has a complex and multifaceted geologic and oceanographic history that has influenced and shaped patterns of marine invertebrate diversity. This evolutionary history consists of major events on a wide range of time scales such as the formation of the Antarctic Polar Front (25-41 million years ago) to repeated glacial cycles during the past million years. These factors variably influenced genetic connectivity of fauna to produce a highly unique, but incredibly diverse marine community. Use of molecular phylogeographic methods is creating the need to revise our understanding of Antarctic patterns of biodiversity. In particular, almost every phylogeographic study carried out to date, suggests that the biodiversity of Antarctic marine shelf fauna is considerably underestimated. In discovering this diversity, some lineages (i.e., cryptic lineages) show no diagnostic morphological differences whereas others (i.e., unrecognized species) show differences that were unknown to science. The sea star genus Odontaster is among the best-studied of Antarctic invertebrate groups. Nonetheless, two unrecognized lineages were recently discovered along the Antarctic Peninsula, which is one of the best-studied regions in Antarctica. Herein, we elucidate the molecular and morphological uniqueness of these species and name them O. roseus and O. pearsei. The latter is in honor of John Pearse, an Antarctic biologist, as well as past President and long-time member of the Society of Integrative and Comparative Biology.

  5. The impacts of the summer plateau monsoon over the Tibetan Plateau on the rainfall in the Tarim Basin, China

    Science.gov (United States)

    Zhao, Yong; Huang, Anning; Zhou, Yang; Yang, Qing

    2016-10-01

    The impacts of the summer plateau monsoon (PM) over the Tibetan Plateau on summer rainfall over the Tarim Basin in northwest China are investigated, based on the observed rainfall data at 34 stations and the NCEP/NCAR reanalysis data during 1961 to 2007. Results showed that the PM is well correlated to the summer rainfall over the Tarim Basin. Process analysis shows that strong PM corresponds to an anomalous cyclone over the Tibetan Plateau in the middle troposphere and an anomalous anticyclone in the upper troposphere over northwest part of Tibetan Plateau. They result in cold air moving from high latitudes into Central Asia over the western part of Tibetan Plateau. The concurrences of the cooling in the middle-upper troposphere over Central Asia leads to an anomalous cyclone over Central Asia at 500 hPa and the anomalous descending motions prevailing over the cooling region. Associated with this anomaly, there are enhanced southerly winds and corresponding ascending motion over the Tarim Basin located in the east of the cooling region. These processes lead to more summer rainfall over the Tarim Basin.

  6. Atmospheric sulfur and climate changes: a modelling study at mid and high-southern latitudes; Soufre atmospherique et changements climatiques: une etude de modelisation pour les moyennes et hautes latitudes Sud

    Energy Technology Data Exchange (ETDEWEB)

    Castebrunet, H

    2007-09-15

    The mid and high-southern latitudes are still marginally affected by anthropogenic sulfur emissions. They are the only regions in the world where the natural cycle of the atmospheric sulfur may still be observed. Sulfur aerosols are well-known for their radiative impact, and thus interact with climate. Climate can in turn affect atmospheric sulfur sources, distribution and chemistry. Antarctic ice cores provide information on the evolution of climate and sulfur deposition at the surface of the ice sheet at glacial-interglacial time scales. The aim of this thesis is to develop and use modeling towards a better understanding of the atmospheric sulfur cycle in antarctic and sub-antarctic regions. Ice core data are used to validate model results under glacial climate conditions. An Atmospheric General Circulation Model (AGCM) coupled to a sulfur chemistry module is used: the LMD-ZTSulfur model, version 4. An update of both the physical and chemical parts of the model. The model was first performed. The impact of there changes on modelled sulfur cycle are evaluated for modern climate. Further, boundary conditions are adapted to simulate the atmospheric circulation and sulfur cycle at the Last Glacial Maximum, approximately 20,000 years ago. In the model, sulfur is found to be highly sensitive to antarctic sea-ice coverage, which is still poorly known during the ice age. An original dataset of ice-age sea-ice coverage was developed. Its impact on the oceanic emissions of dimethyl sulfide, main precursor of sulfur aerosols at high-southern latitudes, is discussed. Using the same oceanic sulfur reservoirs as for present day climate, the model broadly reproduces the glacial deposits of sulfur aerosols on the Antarctic plateau, suggesting little impact of climate on oceanic sulfur production in the Antarctic region. Sensitivity tests were carried out to draw an up-to-date status of major uncertainties and difficulties facing future progress in understanding atmospheric

  7. Using beryllium-10 to test the validity of past accumulation rate reconstruction from water isotope records in East Antarctic ice cores

    Directory of Open Access Journals (Sweden)

    A. Cauquoin

    2014-08-01

    Full Text Available Ice cores are exceptional archives which allow us to reconstruct a wealth of climatic parameters as well as past atmospheric composition over the last 800 ka in Antarctica. Inferring the variations of past accumulation rate in polar regions is essential both for documenting past climate and for ice core chronology. On the East Antarctic plateau, the accumulation rate is so small that annual layers cannot be identified and accumulation rate is mainly deduced from the water isotopic composition assuming constant temporal relationships between temperature, water isotopic composition and accumulation rate. Such assumption leads to large uncertainties on the reconstructed past accumulation rate. Here, we use high resolution beryllium-10 (10Be as an alternative tool for inferring past accumulation rate for the EPICA Dome C ice core, in East Antarctica. We present a high resolution 10Be record covering a full climatic cycle over the period 269 to 355 kyr BP from MIS 9 to MIS 10 (Marine Isotope Stages. After correcting 10Be for the estimated effect of the paleomagnetic field, we deduce that the classical estimation of accumulation rate variations from records of water isotopes agrees, with a possible underestimation of 16%, with the uncertainty on the temperature reconstruction from water isotopes in Antarctic ice cores. This is within their uncertainty of −10 to +30%. Finally, we show that the relationship between temperature and accumulation rate is comparable when using ice core data and results from several AGCM simulations run on glacial–interglacial conditions despite a larger spread in model outputs. These results indicate that the thermodynamic law linking moisture content in the air and temperature, as implemented in the different models, leads to realistic results even in polar regions, at the end of the water distillation trajectory.

  8. Metagenomic Analysis of Bacterial Communities of Antarctic Surface Snow.

    Science.gov (United States)

    Lopatina, Anna; Medvedeva, Sofia; Shmakov, Sergey; Logacheva, Maria D; Krylenkov, Vjacheslav; Severinov, Konstantin

    2016-01-01

    The diversity of bacteria present in surface snow around four Russian stations in Eastern Antarctica was studied by high throughput sequencing of amplified 16S rRNA gene fragments and shotgun metagenomic sequencing. Considerable class- and genus-level variation between the samples was revealed indicating a presence of inter-site diversity of bacteria in Antarctic snow. Flavobacterium was a major genus in one sampling site and was also detected in other sites. The diversity of flavobacterial type II-C CRISPR spacers in the samples was investigated by metagenome sequencing. Thousands of unique spacers were revealed with less than 35% overlap between the sampling sites, indicating an enormous natural variety of flavobacterial CRISPR spacers and, by extension, high level of adaptive activity of the corresponding CRISPR-Cas system. None of the spacers matched known spacers of flavobacterial isolates from the Northern hemisphere. Moreover, the percentage of spacers with matches with Antarctic metagenomic sequences obtained in this work was significantly higher than with sequences from much larger publically available environmental metagenomic database. The results indicate that despite the overall very high level of diversity, Antarctic Flavobacteria comprise a separate pool that experiences pressures from mobile genetic elements different from those present in other parts of the world. The results also establish analysis of metagenomic CRISPR spacer content as a powerful tool to study bacterial populations diversity.

  9. Metagenomic Analysis of Bacterial Communities of Antarctic Surface Snow

    Directory of Open Access Journals (Sweden)

    Anna eLopatina

    2016-03-01

    Full Text Available The diversity of bacteria present in surface snow around four Russian stations in Eastern Antarctica was studied by high throughput sequencing of amplified 16S rRNA gene fragments and shotgun metagenomic sequencing. Considerable class- and genus-level variation between the samples was revealed indicating a presence of inter-site diversity of bacteria in Antarctic snow. Flavobacterium was a major genus in one sampling site and was also detected in other sites. The diversity of flavobacterial type II-C CRISPR spacers in the samples was investigated by metagenome sequencing. Thousands of unique spacers were revealed with less than 35% overlap between the sampling sites, indicating an enormous natural variety of flavobacterial CRISPR spacers and, by extension, high level of adaptive activity of the corresponding CRISPR-Cas system. None of the spacers matched known spacers of flavobacterial isolates from the Northern hemisphere. Moreover, the percentage of spacers with matches with Antarctic metagenomic sequences obtained in this work was significantly higher than with sequences from much larger publically available environmental metagenomic database. The results indicate that despite the overall very high level of diversity, Antarctic Flavobacteria comprise a separate pool that experiences pressures from mobile genetic elements different from those present in other parts of the world. The results also establish analysis of metagenomic CRISPR spacer content as a powerful tool to study bacterial populations diversity.

  10. Underwater Optics in Sub-Antarctic and Antarctic Coastal Ecosystems.

    Science.gov (United States)

    Huovinen, Pirjo; Ramírez, Jaime; Gómez, Iván

    2016-01-01

    Understanding underwater optics in natural waters is essential in evaluating aquatic primary production and risk of UV exposure in aquatic habitats. Changing environmental conditions related with global climate change, which imply potential contrasting changes in underwater light climate further emphasize the need to gain insights into patterns related with underwater optics for more accurate future predictions. The present study evaluated penetration of solar radiation in six sub-Antarctic estuaries and fjords in Chilean North Patagonian region (39-44°S) and in an Antarctic bay (62°S). Based on vertical diffuse attenuation coefficients (Kd), derived from measurements with a submersible multichannel radiometer, average summer UV penetration depth (z1%) in these water bodies ranged 2-11 m for UV-B (313 nm), 4-27 m for UV-A (395 nm), and 7-30 m for PAR (euphotic zone). UV attenuation was strongest in the shallow Quempillén estuary, while Fildes Bay (Antarctica) exhibited the highest transparency. Optically non-homogeneous water layers and seasonal variation in transparency (lower in winter) characterized Comau Fjord and Puyuhuapi Channel. In general, multivariate analysis based on Kd values of UV and PAR wavelengths discriminated strongly Quempillén estuary and Puyuhuapi Channel from other study sites. Spatial (horizontal) variation within the estuary of Valdivia river reflected stronger attenuation in zones receiving river impact, while within Fildes Bay a lower spatial variation in water transparency could in general be related to closeness of glaciers, likely due to increased turbidity through ice-driven processes. Higher transparency and deeper UV-B penetration in proportion to UV-A/visible wavelengths observed in Fildes Bay suggests a higher risk for Antarctic ecosystems reflected by e.g. altered UV-B damage vs. photorepair under UV-A/PAR. Considering that damage repair processes often slow down under cool temperatures, adverse UV impact could be further

  11. Extreme late chronotypes and social jetlag challenged by Antarctic conditions in a population of university students from Uruguay.

    Science.gov (United States)

    Tassino, Bettina; Horta, Stefany; Santana, Noelia; Levandovski, Rosa; Silva, Ana

    2016-01-01

    In humans, a person's chronotype depends on environmental cues and on individual characteristics, with late chronotypes prevailing in youth. Social jetlag (SJL), the misalignment between an individual׳s biological clock and social time, is higher in late chronotypes. Strong SJL is expected in Uruguayan university students with morning class schedules and very late entertainment activities. Sleep disorders have been reported in Antarctic inhabitants, that might be a response to the extreme environment or to the strictness of Antarctic life. We evaluated, for the first time in Uruguay, the chronotypes and SJL of 17 undergraduate students of the First Uruguayan Summer School on Antarctic Research, using Munich Chronotype Questionnaire (MCTQ) and sleep logs (SL) recorded during 3 phases: pre-Antarctic, Antarctic, and post-Antarctic. The midsleep point of free days corrected for sleep debt on work days (MSFsc,) was used as proxy of individuals' chronotype, whose values (around 6 a.m.) are the latest ever reported. We found a SJL of around 2 h in average, which correlated positively with MSFsc, confirming that late chronotypes generate a higher sleep debt during weekdays. Midsleep point and sleep duration significantly decreased between pre-Antarctic and Antarctic phases, and sleep duration rebounded to significant higher values in the post-Antarctic phase. Waking time, but not sleep onset time, significantly varied among phases. This evidence suggests that sleep schedules more likely depended on the social agenda than on the environmental light-dark shifts. High motivation of students towards Antarctic activities likely induced a subjective perception of welfare non-dependent on sleep duration.

  12. Extreme late chronotypes and social jetlag challenged by Antarctic conditions in a population of university students from Uruguay

    Science.gov (United States)

    Tassino, Bettina; Horta, Stefany; Santana, Noelia; Levandovski, Rosa; Silva, Ana

    2016-01-01

    In humans, a person’s chronotype depends on environmental cues and on individual characteristics, with late chronotypes prevailing in youth. Social jetlag (SJL), the misalignment between an individual׳s biological clock and social time, is higher in late chronotypes. Strong SJL is expected in Uruguayan university students with morning class schedules and very late entertainment activities. Sleep disorders have been reported in Antarctic inhabitants, that might be a response to the extreme environment or to the strictness of Antarctic life. We evaluated, for the first time in Uruguay, the chronotypes and SJL of 17 undergraduate students of the First Uruguayan Summer School on Antarctic Research, using Munich Chronotype Questionnaire (MCTQ) and sleep logs (SL) recorded during 3 phases: pre-Antarctic, Antarctic, and post-Antarctic. The midsleep point of free days corrected for sleep debt on work days (MSFsc,) was used as proxy of individuals’ chronotype, whose values (around 6 a.m.) are the latest ever reported. We found a SJL of around 2 h in average, which correlated positively with MSFsc, confirming that late chronotypes generate a higher sleep debt during weekdays. Midsleep point and sleep duration significantly decreased between pre-Antarctic and Antarctic phases, and sleep duration rebounded to significant higher values in the post-Antarctic phase. Waking time, but not sleep onset time, significantly varied among phases. This evidence suggests that sleep schedules more likely depended on the social agenda than on the environmental light–dark shifts. High motivation of students towards Antarctic activities likely induced a subjective perception of welfare non-dependent on sleep duration. PMID:27226819

  13. Monuments of the Giza Plateau

    Science.gov (United States)

    Ruggles, Clive L. N.

    The colossal pyramids of the pharaohs Khufu (Cheops), Khafre (Chephren), and Menkaure (Mycerinus) have attracted a huge amount of astronomical interest over the years, both scholarly and popular. Less attention is usually given to the broader context of structures on the Giza Plateau. One of the most notorious ideas connecting the Giza Plateau with astronomy is that the three large pyramids are laid out on the ground so as to reflect the appearance of the three stars of Orion's Belt in the sky. This idea is unsupportable for several reasons but has succeeded in generating huge public interest. Of much greater serious interest is the fact that the three main pyramids were oriented cardinally to extraordinary precision, which raises the questions of why this was important and how it was achieved. Another idea that has attracted serious attention but also some confusion is that the orientations of some narrow shafts within Khufu's pyramid might have been deliberately aligned upon particular stars. The overall layout of monuments on the plateau may certainly have been designed so as to emphasize certain solar phenomena, for symbolic and ideological reasons relating to a dominant sun cult. It is also possible that it formed part of a wider cosmological "master plan" extending to other pyramids and temples up to 20 km distant.

  14. Windblown Pliocene diatoms and East Antarctic Ice Sheet retreat.

    Science.gov (United States)

    Scherer, Reed P; DeConto, Robert M; Pollard, David; Alley, Richard B

    2016-09-20

    Marine diatoms in tillites along the Transantarctic Mountains (TAMs) have been used to suggest a diminished East Antarctic Ice Sheet (EAIS) during Pliocene warm periods. Updated ice-sheet modelling shows significant Pliocene EAIS retreat, creating marine embayments into the Wilkes and Aurora basins that were conducive to high diatom productivity and rapid accumulation of diatomaceous sediments. Here we show that subsequent isostatic uplift exposed accumulated unconsolidated marine deposits to wind erosion. We report new atmospheric modelling utilizing Pliocene climate and derived Antarctic landscapes indicating that prevailing mid-altitude winds transported diatoms towards the TAMs, dominantly from extensive emerged coastal deposits of the Aurora Basin. This result unifies leading ideas from competing sides of a contentious debate about the origin of the diatoms in the TAMs and their link to EAIS history, supporting the view that parts of the EAIS are vulnerable to relatively modest warming, with possible implications for future sea-level rise.

  15. Ecosystem function decays by fungal outbreaks in Antarctic microbial mats.

    Science.gov (United States)

    Velázquez, David; López-Bueno, Alberto; Aguirre de Cárcer, Daniel; de los Ríos, Asunción; Alcamí, Antonio; Quesada, Antonio

    2016-03-14

    Antarctica harbours a remarkably diverse range of freshwater bodies and terrestrial ecosystems, where microbial mats are considered the most important systems in terms of biomass and metabolic capabilities. We describe the presence of lysis plaque-like macroscopic blighted patches within the predominant microbial mats on Livingston Island (Antarctic Peninsula). Those blighting circles are associated with decay in physiological traits as well as nitrogen depletion and changes in the spatial microstructure; these alterations were likely related to disruption of the biogeochemical gradients within the microbial ecosystem caused by an unusually high fungal abundance and consequent physical alterations. This phenomenon has been evidenced at a time of unprecedented rates of local warming in the Antarctic Peninsula area, and decay of these ecosystems is potentially stimulated by warmer temperatures.

  16. The effect of low temperature on Antarctic endolithic green algae

    Science.gov (United States)

    Meyer, M. A.; Morris, G. J.; Friedmann, E. I.

    1988-01-01

    Laboratory experiments show that undercooling to about -5 degrees C occurs in colonized Beacon sandstones of the Ross Desert, Antarctica. High-frequency temperature oscillations between 5 degrees C and -5 degrees C or -10 degrees C (which occur in nature on the rock surface) did not damage Hemichloris antarctica. In a cryomicroscope, H. antarctica appeared to be undamaged after slow or rapid cooling to -50 degrees C. 14CO2 incorporation after freezing to -20 degrees C was unaffected in H. antarctica or in Trebouxia sp. but slightly depressed in Stichococcus sp. (isolated from a less extreme Antarctic habitat). These results suggest that the freezing regime in the Antarctic desert is not injurious to endolithic algae. It is likely that the freezing-point depression inside the rock makes available liquid water for metabolic activity at subzero temperatures. Freezing may occur more frequently on the rock surface and contribute to the abiotic nature of the surface.

  17. Definition of Arctic and Antarctic Sea Ice Variation Index

    Institute of Scientific and Technical Information of China (English)

    Chen Hongxia; Liu Na; Pan Zengdi; Zhang Qinghua

    2004-01-01

    It is well known that varying of the sea ice not only in the Antarctic but also in the Arctic has an active influence on the globe atmosphere and ocean. In order to understand the sea ice variation in detail, for the first time, an objective index of the Arctic and Antarctic sea ice variation is defined by projecting the monthly sea ice concentration anomalies poleward of 20°N or 20°S onto the EOF (empirical orthogonal function)-1 spatial pattern. Comparing with some work in former studies of polar sea ice, the index has the potential for clarifying the variability of sea ice in northern and southern high latitudes.

  18. Cenozoic exhumation of the internal Zagros : First constraints from low-temperature thermochronology and implications for the build-up of the Iranian plateau

    NARCIS (Netherlands)

    François, T.; Agard, P.; Bernet, M.; Meyer, B.; Chung, S.-L.; Zarrinkoub, M. H.; Burov, E.; Monié, P.

    2014-01-01

    The Iranian plateau is a flat ~. 1.5-2. km high plateau thought to result from the collision between the Arabian and Eurasian plates since ~. 30 ± 5. Ma, and may represent a young analogue to the so far better studied Tibetan plateau. In order to constrain the exhumation history of the internal Zagr

  19. Southern high-latitude terrestrial climate change during the Palaeocene–Eocene derived from a marine pollen record (ODP Site 1172, East Tasman Plateau)

    NARCIS (Netherlands)

    Contreras, L.; Pross, J.; Bijl, P.K.; O'Hara, R.B.; Raine, J.I.; Sluijs, A.; Brinkhuis, H.

    2014-01-01

    Reconstructing the early Palaeogene climate dynamicsof terrestrial settings in the high southern latitudes isimportant to assess the role of high-latitude physical and biogeochemicalprocesses in the global climate system. However,whereas a number of high-quality Palaeogene climaterecords has become

  20. The diverse crustal structure and magmatic evolution of the Manihiki Plateau, central Pacific

    Directory of Open Access Journals (Sweden)

    K. Hochmuth

    2014-07-01

    Full Text Available The Manihiki Plateau is a Large Igneous Province (LIP in the central Pacific. It was emplaced as part of the "Super-LIP" Ontong Java Nui and experienced fragmentation into three sub-plateaus, possibly during the break-up of Ontong Java Nui. The Manihiki Plateau is presumably the centerpiece of this "Super-LIP" and its investigation can therefore decipher the break-up mechanisms as well as the evolution of the plateau after its initial emplacement. By analyzing two seismic refraction/wide-angle reflection profiles crossing the two largest sub-plateaus of the Manihiki Plateau, the High Plateau and the Western Plateaus, we give new insights into their crustal structure and magmatic evolution. The High Plateau shows a crustal structure of 20 km thickness and a seismic P wave velocity distribution, which is comparable to other LIPs. The High Plateau experienced a strong secondary volcanism, which can be seen in relicts of seamount chain volcanism. The Western Plateaus on the other hand show no extensive secondary volcanism and are mainly structured by fault systems and sedimentary basins. A constant decrease in Moho depth (9–17 km is a further indicator of crustal stretching on the Western Plateaus. Those findings lead to the conclusion, that the two sub-plateaus of the Manihiki Plateau experienced a different magmatic and tectonic history. Whereas the High Plateau experienced a secondary volcanism, the Western Plateaus underwent crustal stretching during and after the break-up of Ontong Java Nui. This indicates, that the sub-plateaus of the Manihiki Plateau play an individual part in the break-up history of Ontong Java Nui.

  1. Obliquity-paced Pliocene West Antarctic ice sheet oscillations

    Science.gov (United States)

    Naish, T.; Powell, R.; Levy, R.; Wilson, G.; Scherer, R.; Talarico, F.; Krissek, L.; Niessen, F.; Pompilio, M.; Wilson, T.; Carter, L.; DeConto, R.; Huybers, P.; McKay, R.; Pollard, D.; Ross, J.; Winter, D.; Barrett, P.; Browne, G.; Cody, R.; Cowan, E.; Crampton, J.; Dunbar, G.; Dunbar, N.; Florindo, F.; Gebhardt, C.; Graham, I.; Hannah, M.; Hansaraj, D.; Harwood, D.; Helling, D.; Henrys, S.; Hinnov, L.; Kuhn, G.; Kyle, P.; Laufer, A.; Maffioli, P.; Magens, D.; Mandernack, K.; McIntosh, W.; Millan, C.; Morin, R.; Ohneiser, C.; Paulsen, T.; Persico, D.; Raine, I.; Reed, J.; Riesselman, C.; Sagnotti, L.; Schmitt, D.; Sjunneskog, C.; Strong, P.; Taviani, M.; Vogel, S.; Wilch, T.; Williams, T.

    2009-01-01

    Thirty years after oxygen isotope records from microfossils deposited in ocean sediments confirmed the hypothesis that variations in the Earth's orbital geometry control the ice ages, fundamental questions remain over the response of the Antarctic ice sheets to orbital cycles. Furthermore, an understanding of the behaviour of the marine-based West Antarctic ice sheet (WAIS) during the 'warmer-than-present' early-Pliocene epoch (???5-3 Myr ago) is needed to better constrain the possible range of ice-sheet behaviour in the context of future global warming. Here we present a marine glacial record from the upper 600 m of the AND-1B sediment core recovered from beneath the northwest part of the Ross ice shelf by the ANDRILL programme and demonstrate well-dated, ???40-kyr cyclic variations in ice-sheet extent linked to cycles in insolation influenced by changes in the Earth's axial tilt (obliquity) during the Pliocene. Our data provide direct evidence for orbitally induced oscillations in the WAIS, which periodically collapsed, resulting in a switch from grounded ice, or ice shelves, to open waters in the Ross embayment when planetary temperatures were up to ???3??C warmer than today and atmospheric CO 2 concentration was as high as ???400 p.p.m.v. (refs 5, 6). The evidence is consistent with a new ice-sheet/ice-shelf model that simulates fluctuations in Antarctic ice volume of up to +7 m in equivalent sea level associated with the loss of the WAIS and up to +3 m in equivalent sea level from the East Antarctic ice sheet, in response to ocean-induced melting paced by obliquity. During interglacial times, diatomaceous sediments indicate high surface-water productivity, minimal summer sea ice and air temperatures above freezing, suggesting an additional influence of surface melt under conditions of elevated CO2. ??2009 Macmillan Publishers Limited. All rights reserved.

  2. Stable isotopes and Antarctic moss banks: Plants and soil microbes respond to recent warming on the Antarctic Peninsula

    Science.gov (United States)

    Royles, Jessica; Amesbury, Matthew; Ogée, Jérôme; Wingate, Lisa; Convey, Peter; Hodgson, Dominic; Griffiths, Howard; Leng, Melanie; Charman, Dan

    2014-05-01

    The Antarctic Peninsula is one of the most rapidly warming regions on Earth, with air temperature increases of as much as 3°C recorded since the 1950s. However, the longer-term context of this change is limited and existing records, largely relying on ice core data, are not suitably located to be able to trace the spatial signature of change over time. We are working on a project exploiting stable isotope records preserved in moss peat banks spanning 10 degrees of latitude along the Antarctic Peninsula as an archive of late Holocene climate variability. Here we present a unique time series of past moss growth and soil microbial activity that has been produced from a 150 year old moss bank at Lazarev Bay, Alexander Island (69°S), a site at the southern limit of significant plant growth in the Antarctic Peninsula region. These moss banks are ideal archives for palaeoclimate research as they are well-preserved by freezing, generally monospecific, easily dated by radiocarbon techniques, and have sufficiently high accumulation rates to permit decadal resolution. We use accumulation rates, cellulose δ13C and fossil testate amoebae to show that growth rates, assimilation and microbial productivity rose rapidly in the 1960s, consistent with temperature change, although recently may have stalled, concurrent with other evidence. The increase in biological activity is unprecedented in the last 150 years. Along with work completed on Signy Island (60°S), in the South Orkney Islands, in which we used carbon isotope evidence to show recent climate-related enhancement of CO2 assimilation and peat accumulation rates in Antarctica, the observed relationships between moss growth, microbial activity and climate suggests that moss bank records have the potential to test the regional expression of temperature variability shown by instrumental data on the Antarctic Peninsula over centennial to millennial timescales, by providing long-term records of summer growth conditions

  3. 高强度南极磷虾蛋白/海藻复合纤维的制备与表征%Preparation and characterization of high strength Antarctic krill protein/alginate composite fiber

    Institute of Scientific and Technical Information of China (English)

    杨利军; 郭静; 李圣林; 牟思阳; 齐善威

    2016-01-01

    Act glutaraldehyde as enhance modifier to prepare primitive Antarctic krill protein/sodium alginate (AKP/SA)primary fibers using wet spinning process,and the high strength Antarctic krill protein/algae (HAKP/SA)composite fibers were fabricated via online thermal crosslinking technology realizing thermal crosslinking reac-tion through primary fiber spinning line.Thermal crosslinking temperature was defined by Rotational viscometer. The effects of crosslinking degree on microstructure and moisture absorption performance of composite fiber were studied,and the variations of mechanical properties and crystallization properties of composite fiber after reinforce-ment were tested.The results show that glutaraldehyde can perform effective thermal crosslinking reaction when temperature is 80 ℃.AKP/SA composite fiber has good moisture absorption performance,moisture absorption rate of 7.3%,the moisture absorption performance of composite fiber decreases and moisture balance time shortens with the increase of crosslinking degree.HAKP/SA composite fiber still exists in amorphous form.Surface of composite fiber shows uniform groove microstructure.Mechanics performance test shows that the fiber breaking strength after reinforcement increases by 1 3%.%以戊二醛为增强改性剂,利用湿法纺丝制备含有预埋增强剂的南极磷虾蛋白/海藻(AKP/SA)初生纤维,通过初生纤维纺丝线在线热交联技术实现热交联反应从而制得高强度南极磷虾蛋白/海藻(HAKP/SA)复合纤维。利用旋转黏度计确定了增强交联反应的热交联温度,研究了交联度对复合纤维微观结构以及吸湿性能的影响,测试了增强后复合纤维力学性能和结晶性能的变化。结果表明:80℃时戊二醛能有效发生热交联反应;AKP/SA复合纤维具有较好的吸湿性能,吸湿率为7.3%,随着交联度的提高,复合纤维的吸湿性能降低,吸湿平衡时间缩短;HAKP/SA复合纤维仍以非

  4. Comparing past accumulation rate reconstructions in East Antarctic ice cores using 10Be, water isotopes and CMIP5-PMIP3 models

    Directory of Open Access Journals (Sweden)

    A. Cauquoin

    2015-03-01

    Full Text Available Ice cores are exceptional archives which allow us to reconstruct a wealth of climatic parameters as well as past atmospheric composition over the last 800 kyr in Antarctica. Inferring the variations in past accumulation rate in polar regions is essential both for documenting past climate and for ice core chronology. On the East Antarctic Plateau, the accumulation rate is so small that annual layers cannot be identified and accumulation rate is mainly deduced from the water isotopic composition assuming constant temporal relationships between temperature, water isotopic composition and accumulation rate. Such an assumption leads to large uncertainties on the reconstructed past accumulation rate. Here, we use high-resolution beryllium-10 (10Be as an alternative tool for inferring past accumulation rate for the EPICA Dome C ice core, in East Antarctica. We present a high-resolution 10Be record covering a full climatic cycle over the period 269 to 355 ka from Marine Isotope Stage (MIS 9 to 10, including a period warmer than pre-industrial (MIS 9.3 optimum. After correcting 10Be for the estimated effect of the palaeomagnetic field, we deduce that the 10Be reconstruction is in reasonably good agreement with EDC3 values for the full cycle except for the period warmer than present. For the latter, the accumulation is up to 13% larger (4.46 cm ie yr−1 instead of 3.95. This result is in agreement with the studies suggesting an underestimation of the deuterium-based accumulation for the optimum of the Holocene (Parrenin et al. 2007a. Using the relationship between accumulation rate and surface temperature from the saturation vapour relationship, the 10Be-based accumulation rate reconstruction suggests that the temperature increase between the MIS 9.3 optimum and present day may be 2.4 K warmer than estimated by the water isotopes reconstruction. We compare these reconstructions to the available model results from CMIP5-PMIP3 for a glacial and an

  5. Biodiversity and conservation in the Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The Tibetan Plateau (Qinghai-Xizang Plateau) is a unique biogeographic region in the world, where various landscapes, altitudinal belts, alpine ecosystems, and endangered and endemic species have been developed. A total of 26 altitudinal belts, 28 spectra of altitudinal belts, 12,000 species of vascular plant, 5,000 species of epiphytes, 210 species of mammals, and 532 species of birds have been recorded. The plateau is also one of the centers of species formation and differentiation in the world. To protect the biodiversity of the plateau, about 80 nature reserves have been designated, of which 45 are national or provincial, covering about 22% of the plateau area. Most of the nature reserves are distributed in the southeastern plateau. Recently, the Chinese government has initiated the "Natural Forests Protection Project of China,' mainly in the upper reaches of the Yangtze and Yellow rivers. "No logging" policies have been made and implemented for these areas.

  6. Abundance, viability and culturability of Antarctic bacteria

    Digital Repository Service at National Institute of Oceanography (India)

    LokaBharathi, P.A.; DeSouza, M.J.B.D.; Nair, S.; Chandramohan, D.

    The viability of total number of bacteria decide the mineralisation rate in any ecosystem and ultimately the fertility of the region. This study aims at establishing the extent of viability in the standing stock of the Antarctic bacterial population...

  7. South African Antarctic earth science research programme

    CSIR Research Space (South Africa)

    SASCAR

    1984-02-01

    Full Text Available This document describes the past, current and planned future South African earth science research programme in the Antarctic, Southern Ocean and subantarctic regions. The scientific programme comprises five components into which present and future...

  8. Observations on phytoplankton pigments, zooplankton and physico-chemical parameters in surface waters from southern Indian Ocean and Antarctic region

    Digital Repository Service at National Institute of Oceanography (India)

    JiyalalRam, M.; Goswami, S.C.

    Observations on distribution of chlorophyll a, phaeopigments, zooplankton and physico-chemical parameters in the Southern Ocean were carried out during 9th Indian Antarctic-Expedition (1989-1990). The results indicated high phytoplankton biomass...

  9. Sandy Desertification Status and its Driving Mechanism in North Tibet Plateau

    Institute of Scientific and Technical Information of China (English)

    DONG Yuxiang

    2004-01-01

    As the main body of Qinghai-Tibetan Plateau, North Tibet Plateau is one of three major sandy desertification regions in China and also a representative sandy desertification zone of Qinghai-Tibet Plateau. Accordingly, it is an important region for the study of recent sandy desertification processes and formation mechanism. From such aspects as desertified land types, areas and distributions etc., this paper analyses in detail the sandy desertification status on North Tibet Plateau,and qualitatively and quantitatively deals with the main factors that affect recent sandy desertification processes and the driving mechanism. Research results show that North Tibet Plateau is an important sandy desertification region in China characterized with large desertified land areas, diversified types,high severity, extensive distributions and serious damages. Sandy desertification occurrence and development resulted from combined effects of natural factors, anthropogenic factors, natural processes and man-made processes, of which climatic change is the main driving force.

  10. COMMENT ON AEROSOL EFFECT ON ANTARCTIC OZONE

    OpenAIRE

    イワサカ, ヤスノブ; Yasunobu, IWASAKA; Guang-Yu, SHI

    1987-01-01

    The structure of the aerosol layer disturbed by a cold air was suggested from the lidar measurements at Syowa Station (69°00′S, 39°35′E). The particle layer containing sublayers of spherical or nonspherical aerosols was frequently observed in Antarctic spring. It is a point one sholud not ignore when he discusses aerosol effects on "Antarctic ozone depletion" through radiative processes and heterogeneous chemical reactions.

  11. Ross Ice Shelf, Antarctic Ice and Clouds

    Science.gov (United States)

    1991-01-01

    In this view of Antarctic ice and clouds, (56.5S, 152.0W), the Ross Ice Shelf of Antarctica is almost totally clear, showing stress cracks in the ice surface caused by wind and tidal drift. Clouds on the eastern edge of the picture are associated with an Antarctic cyclone. Winds stirred up these storms have been known to reach hurricane force.

  12. Characterization of natural co-cultures of Piromyces with Methanobrevibacter ruminantium from yaks grazing on the Qinghai-Tibetan Plateau: a microbial consortium with high potential in plant biomass degradation.

    Science.gov (United States)

    Wei, Ya-Qin; Yang, Hong-Jian; Long, Rui-Jun; Wang, Zhi-Ye; Cao, Bin-Bin; Ren, Qin-Chang; Wu, Tian-Tian

    2017-12-01

    Anaerobic fungi reside in the gut of herbivore and synergize with associated methanogenic archaea to decompose ingested plant biomass. Despite their potential for use in bioconversion industry, only a few natural fungus-methanogen co-cultures have been isolated and characterized. In this study we identified three co-cultures of Piromyces with Methanobrevibacter ruminantium from the rumen of yaks grazing on the Qinghai Tibetan Plateau. The representative co-culture, namely (Piromyces + M. ruminantium) Yak-G18, showed remarkable polysaccharide hydrolase production, especially xylanase. Consequently, it was able to degrade various lignocellulose substrates with a biodegrading capability superior to most previously identified fungus or fungus-methanogen co-culture isolates. End-product profiling analysis validated the beneficial metabolic impact of associated methanogen on fungus as revealed by high-yield production of methane and acetate and sustained growth on lignocellulose. Together, our data demonstrated a great potential of (Piromyces + M. ruminantium) Yak-G18 co-culture for use in industrial bioconversion of lignocellulosic biomass.

  13. Antarctic krill 454 pyrosequencing reveals chaperone and stress transcriptome.

    Directory of Open Access Journals (Sweden)

    Melody S Clark

    Full Text Available BACKGROUND: The Antarctic krill Euphausia superba is a keystone species in the Antarctic food chain. Not only is it a significant grazer of phytoplankton, but it is also a major food item for charismatic megafauna such as whales and seals and an important Southern Ocean fisheries crop. Ecological data suggest that this species is being affected by climate change and this will have considerable consequences for the balance of the Southern Ocean ecosystem. Hence, understanding how this organism functions is a priority area and will provide fundamental data for life history studies, energy budget calculations and food web models. METHODOLOGY/PRINCIPAL FINDINGS: The assembly of the 454 transcriptome of E. superba resulted in 22,177 contigs with an average size of 492bp (ranging between 137 and 8515bp. In depth analysis of the data revealed an extensive catalogue of the cellular chaperone systems and the major antioxidant proteins. Full length sequences were characterised for the chaperones HSP70, HSP90 and the super-oxide dismutase antioxidants, with the discovery of potentially novel duplications of these genes. The sequence data contained 41,470 microsatellites and 17,776 Single Nucleotide Polymorphisms (SNPs/INDELS, providing a resource for population and also gene function studies. CONCLUSIONS: This paper details the first 454 generated data for a pelagic Antarctic species or any pelagic crustacean globally. The classical "stress proteins", such as HSP70, HSP90, ferritin and GST were all highly expressed. These genes were shown to be over expressed in the transcriptomes of Antarctic notothenioid fish and hypothesized as adaptations to living in the cold, with the associated problems of decreased protein folding efficiency and increased vulnerability to damage by reactive oxygen species. Hence, these data will provide a major resource for future physiological work on krill, but in particular a suite of "stress" genes for studies understanding

  14. Widespread movement of meltwater onto and across Antarctic ice shelves

    Science.gov (United States)

    Kingslake, Jonathan; Ely, Jeremy C.; Das, Indrani; Bell, Robin E.

    2017-04-01

    Surface meltwater drains across ice sheets, forming melt ponds that can trigger ice-shelf collapse, acceleration of grounded ice flow and increased sea-level rise. Numerical models of the Antarctic Ice Sheet that incorporate meltwater’s impact on ice shelves, but ignore the movement of water across the ice surface, predict a metre of global sea-level rise this century in response to atmospheric warming. To understand the impact of water moving across the ice surface a broad quantification of surface meltwater and its drainage is needed. Yet, despite extensive research in Greenland and observations of individual drainage systems in Antarctica, we have little understanding of Antarctic-wide surface hydrology or how it will evolve. Here we show widespread drainage of meltwater across the surface of the ice sheet through surface streams and ponds (hereafter ‘surface drainage’) as far south as 85° S and as high as 1,300 metres above sea level. Our findings are based on satellite imagery from 1973 onwards and aerial photography from 1947 onwards. Surface drainage has persisted for decades, transporting water up to 120 kilometres from grounded ice onto and across ice shelves, feeding vast melt ponds up to 80 kilometres long. Large-scale surface drainage could deliver water to areas of ice shelves vulnerable to collapse, as melt rates increase this century. While Antarctic surface melt ponds are relatively well documented on some ice shelves, we have discovered that ponds often form part of widespread, large-scale surface drainage systems. In a warming climate, enhanced surface drainage could accelerate future ice-mass loss from Antarctic, potentially via positive feedbacks between the extent of exposed rock, melting and thinning of the ice sheet.

  15. Temperature-oxygen interactions in Antarctic nudibranch egg masses.

    Science.gov (United States)

    Woods, H Arthur; Moran, Amy L

    2008-03-01

    The Southern Ocean is one of the coldest, most stable marine environments on Earth and represents a unique environment for investigating metabolic consequences of low temperature. Here we test predictions of a new diffusion-reaction model of O(2) distributions in egg masses, using egg masses of the Antarctic nudibranch mollusk, Tritonia challengeriana. When warmed from -1.5 degrees to +1.5 degrees C, embryos of T. challengeriana showed large increases in O(2) consumption (Q(10) values of 9.6-30.0). Oxygen electrode measurements in intact masses showed, however, that O(2) levels were high throughout and virtually unaffected by temperature. The model suggested that both effects stemmed from very low metabolic densities in egg masses. Detailed morphological measurements of egg masses of T. challengeriana and a temperate congener, T. diomedea, revealed large differences in structure that may be related to O(2) availability. Egg masses of T. challengeriana were approximately twice as thick. However, the most dramatic effects were observed in embryos: embryos of T. challengeriana were >32 times larger (by volume) than embryos of T. diomedea. Antarctic embryos also were contained singly in large egg capsules ( approximately 500 mum diameter). Consequently, Antarctic embryos occurred at much lower densities, with very low metabolic densities.

  16. High prevalence of Leucocytozoon spp. in the endangered yellow-eyed penguin (Megadyptes antipodes) in the sub-Antarctic regions of New Zealand.

    Science.gov (United States)

    Argilla, L S; Howe, L; Gartrell, B D; Alley, M R

    2013-04-01

    Yellow-eyed penguins (YEPs) have suffered major population declines over the past 30 years, with no single cause established. Leucocytozoon was first identified in yellow-eyed penguins in 2005. During the 2008/09 breeding season, a high mortality was seen in both mainland yellow-eyed penguins as well as those on Enderby Island of the Auckland Islands archipelago. A high overall prevalence of Leucocytozoon spp. in association with a high incidence of chick mortality was observed during this period on Enderby Island. One chick had histological evidence of leucocytozoonosis with megaloschizonts in multiple organs throughout its body. In addition, a high prevalence (73·7%) of Leucocytozoon was observed by PCR in the blood of adult Enderby yellow-eyed penguins taken during the 2006/07 season. These findings were different from the low prevalence detected by PCR on the coast of the South Island (11%) during the 2008/2009 breeding session and earlier on Campbell Island (21%) during the 2006/2007 breeding session. The Leucocytozoon spp. sequences detected lead us to conclude that the Leucocytozoon parasite is common in yellow-eyed penguins and has a higher prevalence in penguins from Enderby Island than those from Campbell Island and the mainland of New Zealand. The Enderby Island yellow-eyed penguins are infected with a Leucocytozoon spp. that is genetically distinct from that found in other yellow-eyed penguin populations. The role of Leucocytozoon in the high levels of chick mortality in the yellow-eyed penguins remains unclear.

  17. Colorado Plateau Rapid Ecoregion Assessment Management Question H1: Where are high-use recreation sites, developments, roads, infrastructure or areas of intensive recreation use located (including boating)?

    Data.gov (United States)

    Bureau of Land Management, Department of the Interior — This map shows areas of high-use recreation, including recreation sites compiled from USFS and BLM, recreation areas (including OHV areas), water-based recreation...

  18. Antarctic polar plateau vertical electric field variations across heliocentric current sheet crossings

    Science.gov (United States)

    Burns, G. B.; Tinsley, B. A.; Klekociuk, A. R.; Troshichev, O. A.; Frank-Kamenetsky, A. V.; Duldig, M. L.; Bering, E. A.; Clem, J. M.

    2006-03-01

    A superposed epoch analysis of variations of the vertical electric field measured at Vostok (78.5°S, 107°E; magnetic latitude 83.6°S) during 1998 2002 heliocentric current sheet (HCS) crossings yields no significant variation other than an association imposed by polar-cap potential differences above the site. This result contradicts published reports of a reduction ˜15% in electric field 1 3 days after HCS crossings, an observation initially made ˜30 years ago. If such a reduction had been caused by reductions in stratospheric ionising radiation, the presence of polar stratospheric clouds (PSC) would seem necessary for the occurrence of this effect. PSCs would increase the resistance of the stratosphere thus making ionisation in that region significant in the context of the ionosphere ground current flow, in a manner analogous to the role of volcanic aerosols in the stratosphere in the explanation of the weakening of northern hemisphere winter cyclones associated with HCS crossings, the so-called ‘Wilcox effect’. However, separating the present data to correspond to the likely presence of PSC above Vostok also does not yield the reported reduction. Significant increases or decreases of the vertical electric field emerge from the observations when the HCS crossings are separated into sets depending on whether the solar wind magnetic field changes from ‘toward-to-away’ (increase of ˜11%) and ‘away-to-toward’ (decrease of ˜8%). Polar-cap potential changes above the site, inferred from solar wind parameters using the Weimer model, also show such step functions that reverse with the sign of HCS transition and are broadly consistent with the measured electric field increases or decreases. Remaining differences between the measurements and the model are consistent with a somewhat stronger solar wind speed and/or magnetic activity influence on polar-cap convection above Vostok than is predicted by the model. Variations in ground-level neutron counts, a measure of cosmic ray influence on the atmospheric conductivity, demonstrate average variations of less than 1% around HCS crossings and at this level would not contribute significantly to the electric field variations. Magnetic activity (measured using the Kp index) and solar wind speed decrease around HCS crossings independent of whether the crossings are ‘toward-to-away’ or ‘away-to-toward’. These decreases are broadly similar in shape to the previously reported Vostok electric field responses. However, their effects on ionospheric potential are included in the Weimer model, and are small. In contrast to sub-auroral latitudes, where the precipitation of MeV electrons from the radiation belts has a characteristic decrease for both types of HCS crossing, there are no known sources of stratospheric ionising radiation in the polar caps that could explain the previously reported effect. Thus, observation and theory are now in agreement for the absence of this effect.

  19. Have Periprosthetic Hip Infection Rates Plateaued?

    Science.gov (United States)

    Perfetti, Dean C; Boylan, Matthew R; Naziri, Qais; Paulino, Carl B; Kurtz, Steven M; Mont, Michael A

    2017-07-01

    Periprosthetic joint infection (PJI) is a serious complication of total hip arthroplasty (THA). Although the number of revision cases is increasing, the prevalence of PJI as an indication for revision surgery, and the variability of this indication among surgeons and hospitals, is unclear. The New York Statewide Planning and Research Cooperative System was used to identify 33,582 patients undergoing revision THA between 2000 and 2013. PJI was identified using International Classification of Diseases, Ninth Revision diagnosis codes. Volume was defined using mean number of revision THAs performed annually by each hospital and surgeon. PJI was the indication for 13.0% of all revision THAs. The percentage of revision THAs for PJI increased between years 2000 and 2007 (odds ratio [OR] = 1.05, P < .001), but decreased between years 2008 and 2013 (OR = 0.96, P = .001). Compared to medium-volume hospitals, the PJI burden at high-volume hospitals decreased during years 2000-2007 (OR = 0.58, P < .001) and 2008-2013 (OR = 0.57, P < .001). Compared to medium-volume surgeons, the PJI burden for high-volume surgeons increased during years 2000-2007 (OR = 1.39, P < .001), but did not differ during years 2008-2013 (P = .618). The burden of PJI as an indication for revision THA may be plateauing. High-volume institutions have seen decreases in the percentage of revisions performed for PJI over the complete study duration. Specific surgeon may be associated with the plateauing in PJI rates as high-volume surgeons in 2008-2013 were no longer found to be at increased risk of PJI as an indication for revision THA. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Advances through collaboration: sharing seismic reflection data via the Antarctic Seismic Data Library System for Cooperative Research (SDLS)

    Science.gov (United States)

    Wardell, N.; Childs, J. R.; Cooper, A. K.

    2007-01-01

    The Antarctic Seismic Data Library System for Cooperative Research (SDLS) has served for the past 16 years under the auspices of the Antarctic Treaty (ATCM Recommendation XVI-12) as a role model for collaboration and equitable sharing of Antarctic multichannel seismic reflection (MCS) data for geoscience studies. During this period, collaboration in MCS studies has advanced deciphering the seismic stratigraphy and structure of Antarctica’s continental margin more rapidly than previously. MCS data compilations provided the geologic framework for scientific drilling at several Antarctic locations and for high-resolution seismic and sampling studies to decipher Cenozoic depositional paleoenvironments. The SDLS successes come from cooperation of National Antarctic Programs and individual investigators in “on-time” submissions of their MCS data. Most do, but some do not. The SDLS community has an International Polar Year (IPY) goal of all overdue MCS data being sent to the SDLS by end of IPY. The community science objective is to compile all Antarctic MCS data to derive a unified seismic stratigraphy for the continental margin – a stratigraphy to be used with drilling data to derive Cenozoic circum-Antarctic paleobathymetry maps and local-to-regional scale paleoenvironmental histories.

  1. Spatial Distribution of Soil Erosion Sensitivity on the Tibet Plateau

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-Dan; ZHONG Xiang-Hao; FAN Jian-Rong

    2005-01-01

    The Tibet Plateau, occupying the main part of Qinghai-Tibet Plateau and having an average altitude of 4 500 m, has geomorphological features that are unique in the world, with soil erosion being one of the main ecological problems. Thus the main objectives of the present research were to set up an efficient and simple way of evaluating spatial distribution of soil erosion sensitivity in the Tibet Plateau as well as the responses of soil erosion to changes of natural environmental conditions, and to indicate key regions where soil erosion should be preferentially controlled. Based on the Universal Soil Loss Equation (USLE), the study applied geographic information system (GIS) technology to develop a methodological reference framework, from which soil erosion sensitivity could be evaluated. The impact of precipitation, soil, topography and vegetation on soil erosion was divided into classes of extreme sensitivity, high sensitivity, medium sensitivity, low sensitivity and no sensitivity. With the aid of GIS, the resultant map from overlaying various factors showed that soil erosion sensitivity had great discrepancy in different parts of the region. In the southeastern part of the Tibet Plateau there were mainly three classes of sensitivity, namely, extreme, high and medium sensitivity. However, the other two classes, low and no sensitivity, were dominant in the northwestern part.

  2. MID-MIOCENE SEQUENCES OF HIGH- AND MODERATE-MG VOLCANIC ROCKS IN VITIM PLATEAU, SOUTHERN SIBERIA: IMPACT OF A SUB-LITHOSPHERIC CONVECTIVE MATERIAL ON THE LITHOSPHERE

    Directory of Open Access Journals (Sweden)

    I. S. Chuvashova

    2015-09-01

    Full Text Available A comparative study of major elements, trace elements, and isotopes in high- and moderate-Mg volcanic sequences of 16–14 and 14–13 Ma, respectively, has been performed in the Bereya volcanic center. In the former (small volume sequence, contaminated by crustal material basalts and trachybasalts of K–Na series were followed by uncontaminated basanites and basalts of transitional (K–Na–K compositions and afterwards by picrobasalts and ba­salts of K series. From pressure estimates using equation [Scarrow, Cox, 1995], high-Mg magma originated at the deep range of 115–150 km. In the latter (high-volume sequence, basalts and basaltic andesites of transitional (Na–K–Na compositions and basalts of Na series were overlain by basalts and trachybasalts of K–Na series. First, there was a strong melting of its shallow garnet-free part with coeval weak melting of more deep garnet-bearing portion, then only a deep garnet-bearing portion of the lithospheric mantle melted. It is suggested that the sequential formation of high- and moderate-Mg melts reflected the mid-Miocene thermal impact of the lithosphere by hot material from the Transbaikalian low-velocity domain, which had the potential temperature Tp as high as 1510 °С. This thermal impact triggered the rifting in the lithosphere of the Baikal Rift System.

  3. The SCAR Standing Committee on Antarctic Data Management - new directions in access to Antarctic research data

    Science.gov (United States)

    de Bruin, T.

    2009-04-01

    The SCAR Standing Committee on Antarctic Data Management (SC-ADM) was established by the Scientific Committee on Antarctic Research (SCAR) and the Council of Managers of National Antarctic Programs (COMNAP), to assist in the fulfillment of the data management obligations imposed by the Antarctic Treaty (section III.1.c): "Scientific observations and results from Antarctica shall be exchanged and made freely available." SC-ADM comprises representatives of the National Antarctic Data Centres or national points of contact. Currently 31 nations around the world are represented in SC-ADM. So far, SC-ADM has been focussing on the coordination of the Antarctic Master Directory (AMD), the internationally accessible, web-based, searchable record of Antarctic and Southern Ocean data set descriptions. The AMD is directly integrated into the international Global Change Master Directory (GCMD) to help further merge Antarctic science into global science. The AMD is a resource for scientists to advertise the data they have collected and to search for data they may need. Currently, SC-ADM is in a transition phase, moving forward to provide data access. Existing systems and web services technology will be used as much as possible, to increase efficiency and prevent 're-inventing the wheel' This poster will give an overview of this process, the current status and the expected results.

  4. The role of the Hikurangi Plateau in the dynamics of the Hikurangi Subduction Margin

    Science.gov (United States)

    Willis, David; Moresi, Louis; Betts, Peter; Ailleres, Laurent

    2015-04-01

    The collision of the Hikurangi Plateau with the Hikurangi Subduction Zone coincides with a change from extension to shortening in the overriding Australian Plate. The 15km thick oceanic Hikurangi Plateau is juxtaposed with Chatham Rise at the southern edge of the subduction margin, possibly extending an unknown distance beneath the Chatham Rise. We explore the influence of the Hikurangi Plateau and its size on subduction dynamics using a series of 3D visco-elastic Underworld models with free slip boundary conditions. The models rely on negative slab buoyancy to drive subduction, with the buoyant oceanic plateau altering the dynamics. The models are benchmarked against New Zealand GPS velocities, paleomagnetic rotations, and fault zones. Both the overriding and subducting plates have undergone significant rotation since 23Ma with ~90° clockwise rotation of the overriding plate relative to the subducting plate. Distinctive fault zones have also been created with the Marlborough Fault Zone facilitating escape tectonics around the Chatham Rise; the North Island Dextral Fault Belt allowing lateral movement between the fore and back-arcs; extension in Taupo Volcanic Zone assisting back-arc extension; and active N-S extension in the Chatham Rise adjacent to the Hikurangi Plateau. In a model without an oceanic plateau, the subduction zone undergoes roll-back along its entire margin. Extension occurs along the overriding plate adjacent to subduction, with shortening limited to the collision of the Chatham Rise. Rotation rates adjacent to the Chatham Rise are extremely high, and decrease rapidly northward and there is no rotation of the subducting plate. When an oceanic plateau is included in the model, shortening occurs at the southern margin of the subduction zone as subduction shallows with the entry of the bouyant plateau. Rotation starts in the subducting plate as the plateau enters the subduction zone. This rotation is attributed to a decrease in slab pull southward

  5. Into Tibet: An Early Pliocene Dispersal of Fossil Zokor (Rodentia: Spalacidae) from Mongolian Plateau to the Hinterland of Tibetan Plateau.

    Science.gov (United States)

    Li, Qiang; Wang, Xiaoming

    2015-01-01

    This paper reports the fossil zokors (Myospalacinae) collected from the lower Pliocene (~4.4 Ma) of Zanda Basin, southwestern Tibet, which is the first record in the hinterland of Tibetan Plateau within the Himalayan Range. Materials include 29 isolated molars belonging to Prosiphneus eriksoni (Schlosser, 1924) by having characters including large size, highly fused roots, upper molars of orthomegodont type, m1 anterior cap small and centrally located, and first pair of m1 reentrants on opposing sides, high crowns, and high value of dentine tract parameters. Based on the cladistics analysis, all seven species of Prosiphneus and P. eriksoni of Zanda form a monophyletic clade. P. eriksoni from Zanda, on the other hand, is nearly the terminal taxon of this clade. The appearance of P. eriksoni in Zanda represents a significant dispersal in the early Pliocene from its center of origin in north China and Mongolian Plateau, possibly via the Hol Xil-Qiangtang hinterland in northern Tibet. The fast evolving zokors are highly adapted to open terrains at a time when regional climates had become increasingly drier in the desert zones north of Tibetan Plateau during the late Miocene to Pliocene. The occurrence of this zokor in Tibet thus suggests a rather open steppe environment. Based on fossils of large mammals, we have formulated an "out of Tibet" hypothesis that suggests earlier and more primitive large mammals from the Pliocene of Tibet giving rise to the Ice Age megafauna. However, fossil records for large mammals are still too poor to evaluate whether they have evolved from lineages endemic to the Tibetan Plateau or were immigrants from outside. The superior record of small mammals is in a better position to address this question. With relatively dense age intervals and numerous localities in much of northern Asia, fossil zokors provide the first example of an "into Tibet" scenario--earlier and more primitive taxa originated from outside of the Tibetan Plateau and the

  6. Evolution of the Antarctic Peninsula lithosphere: Evidence from Mesozoic mafic rocks

    Science.gov (United States)

    Riley, T. R.; Curtis, M. L.; Flowerdew, M. J.; Whitehouse, M. J.

    2016-02-01

    New geochronology from a thick (> 800 m) basaltic succession along the eastern margin of the Antarctic Peninsula confirm a Middle Jurassic age (178 ± 1 Ma). This marginally postdates the adjacent Ferrar large igneous province of the Transantarctic Mountains and predates the extensive silicic volcanism of the Mapple Formation (~ 170 Ma) of the Antarctic Peninsula. The geochemistry of other rare, but broadly contemporaneous, basaltic successions of the Antarctic Peninsula, along with Cretaceous-age mafic dykes, are used to interpret the influences of lithospheric and asthenospheric mantle sources during the Mesozoic. Two significant high magmatic addition rate events occurred along the Antarctic Peninsula continental margin at 170 and 110 Ma and can be correlated to events along the South American Cordillera. These 'flare-up' events are characterised by extensive silicic (mostly ignimbrite) volcanism of the Chon Aike Province (V2 event: 170 Ma) and significant granitoid batholith emplacement of the Lassiter Coast intrusive suite (110 Ma). The 170 Ma event is exposed across large parts of the northern Antarctic Peninsula, whilst the 110 Ma event is more widespread across the southern Antarctic Peninsula. The basaltic volcanism described here precedes the 'flare-up' event at 170 Ma and has geochemical characteristics that indicate a thickened lithosphere prevailed. A major dyke swarm that followed the 170 Ma event indicates that extensive lithospheric thinning had occurred, which allowed the ascent of depleted mafic melts. The thinning was the direct result of widespread lower crustal/upper lithospheric melting associated with the silicic volcanism. In the southern Antarctic Peninsula, the lithosphere remained over thickened until the emplacement of the major batholiths of the Lassiter Coast intrusive suite at 110 Ma and was then immediately followed by the emplacement of more asthenosphere-like melts indicating extensive lithospheric thinning.

  7. Modelling the effects of environmental conditions on the acoustic occurrence and behaviour of Antarctic blue whales.

    Science.gov (United States)

    Shabangu, Fannie W; Yemane, Dawit; Stafford, Kathleen M; Ensor, Paul; Findlay, Ken P

    2017-01-01

    Harvested to perilously low numbers by commercial whaling during the past century, the large scale response of Antarctic blue whales Balaenoptera musculus intermedia to environmental variability is poorly understood. This study uses acoustic data collected from 586 sonobuoys deployed in the austral summers of 1997 through 2009, south of 38°S, coupled with visual observations of blue whales during the IWC SOWER line-transect surveys. The characteristic Z-call and D-call of Antarctic blue whales were detected using an automated detection template and visual verification method. Using a random forest model, we showed the environmental preferences pattern, spatial occurrence and acoustic behaviour of Antarctic blue whales. Distance to the southern boundary of the Antarctic Circumpolar Current (SBACC), latitude and distance from the nearest Antarctic shores were the main geographic predictors of blue whale call occurrence. Satellite-derived sea surface height, sea surface temperature, and productivity (chlorophyll-a) were the most important environmental predictors of blue whale call occurrence. Call rates of D-calls were strongly predicted by the location of the SBACC, latitude and visually detected number of whales in an area while call rates of Z-call were predicted by the SBACC, latitude and longitude. Satellite-derived sea surface height, wind stress, wind direction, water depth, sea surface temperatures, chlorophyll-a and wind speed were important environmental predictors of blue whale call rates in the Southern Ocean. Blue whale call occurrence and call rates varied significantly in response to inter-annual and long term variability of those environmental predictors. Our results identify the response of Antarctic blue whales to inter-annual variability in environmental conditions and highlighted potential suitable habitats for this population. Such emerging knowledge about the acoustic behaviour, environmental and habitat preferences of Antarctic blue whales is

  8. Modelling the effects of environmental conditions on the acoustic occurrence and behaviour of Antarctic blue whales

    Science.gov (United States)

    Shabangu, Fannie W.; Yemane, Dawit; Stafford, Kathleen M.; Ensor, Paul; Findlay, Ken P.

    2017-01-01

    Harvested to perilously low numbers by commercial whaling during the past century, the large scale response of Antarctic blue whales Balaenoptera musculus intermedia to environmental variability is poorly understood. This study uses acoustic data collected from 586 sonobuoys deployed in the austral summers of 1997 through 2009, south of 38°S, coupled with visual observations of blue whales during the IWC SOWER line-transect surveys. The characteristic Z-call and D-call of Antarctic blue whales were detected using an automated detection template and visual verification method. Using a random forest model, we showed the environmental preferences pattern, spatial occurrence and acoustic behaviour of Antarctic blue whales. Distance to the southern boundary of the Antarctic Circumpolar Current (SBACC), latitude and distance from the nearest Antarctic shores were the main geographic predictors of blue whale call occurrence. Satellite-derived sea surface height, sea surface temperature, and productivity (chlorophyll-a) were the most important environmental predictors of blue whale call occurrence. Call rates of D-calls were strongly predicted by the location of the SBACC, latitude and visually detected number of whales in an area while call rates of Z-call were predicted by the SBACC, latitude and longitude. Satellite-derived sea surface height, wind stress, wind direction, water depth, sea surface temperatures, chlorophyll-a and wind speed were important environmental predictors of blue whale call rates in the Southern Ocean. Blue whale call occurrence and call rates varied significantly in response to inter-annual and long term variability of those environmental predictors. Our results identify the response of Antarctic blue whales to inter-annual variability in environmental conditions and highlighted potential suitable habitats for this population. Such emerging knowledge about the acoustic behaviour, environmental and habitat preferences of Antarctic blue whales is

  9. The Effects of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in an AOGCM

    Science.gov (United States)

    Li, Feng; Newman, Paul; Pawson, Steven; Waugh, Darryn

    2014-01-01

    Stratospheric ozone depletion has played a dominant role in driving Antarctic climate change in the last decades. In order to capture the stratospheric ozone forcing, many coupled atmosphere-ocean general circulation models (AOGCMs) prescribe the Antarctic ozone hole using monthly and zonally averaged ozone field. However, the prescribed ozone hole has a high ozone bias and lacks zonal asymmetry. The impacts of these biases on model simulations, particularly on Southern Ocean and the Antarctic sea ice, are not well understood. The purpose of this study is to determine the effects of using interactive stratospheric chemistry instead of prescribed ozone on Antarctic and Southern Ocean climate change in an AOGCM. We compare two sets of ensemble simulations for the 1960-2010 period using different versions of the Goddard Earth Observing System 5 - AOGCM: one with interactive stratospheric chemistry, and the other with prescribed monthly and zonally averaged ozone and 6 other stratospheric radiative species calculated from the interactive chemistry simulations. Consistent with previous studies using prescribed sea surface temperatures and sea ice concentrations, the interactive chemistry runs simulate a deeper Antarctic ozone hole and consistently larger changes in surface pressure and winds than the prescribed ozone runs. The use of a coupled atmosphere-ocean model in this study enables us to determine the impact of these surface changes on Southern Ocean circulation and Antarctic sea ice. The larger surface wind trends in the interactive chemistry case lead to larger Southern Ocean circulation trends with stronger changes in northerly and westerly surface flow near the Antarctica continent and stronger upwelling near 60S. Using interactive chemistry also simulates a larger decrease of sea ice concentrations. Our results highlight the importance of using interactive chemistry in order to correctly capture the influences of stratospheric ozone depletion on climate

  10. Ionospheric irregularities at Antarctic using GPS measurements

    Indian Academy of Sciences (India)

    Sunita Tiwari; Amit Jain; Shivalika Sarkar; Sudhir Jain; A K Gwal

    2012-04-01

    The purpose of this work is to study the behaviour of the ionospheric scintillation at high latitude during geomagnetically quiet and disturbed conditions which is one of the most relevant themes in the space weather studies. Scintillation is a major problem in navigation application using GPS and in satellite communication at high latitudes. Severe amplitude fading and strong scintillation affect the reliability of GPS navigational system and satellite communication. To study the effects of the ionospheric scintillations, GPS receiver installed at Antarctic station Maitri (Geog. 70.76°S; 11.74°E) was used. The data is collected by using GISTM 4004A, NOVATEL’S GPS receiver during March 2008. Studies show that percentage occurrence of phase scintillation is well correlated with geomagnetic activity during the observation period. The result also shows that very intense scintillations can degrade GPS based location determination due to loss of lock of satellites. These findings indicate that the dependence of scintillations and irregularity occurrence on geomagnetic activity is associated with the magnetic local time (MLT). Large number of patches are reported and their activity depends on the magnetic activity index.

  11. Environmental extremes versus ecological extremes: impact of a massive iceberg on the population dynamics of a high-level Antarctic marine predator†

    Science.gov (United States)

    Chambert, Thierry; Rotella, Jay J.; Garrott, Robert A.

    2012-01-01

    Extreme events have been suggested to play a disproportionate role in shaping ecological processes, but our understanding of the types of environmental conditions that elicit extreme consequences in natural ecosystems is limited. Here, we investigated the impact of a massive iceberg on the dynamics of a population of Weddell seals. Reproductive rates of females were reduced, but survival appeared unaffected. We also found suggestive evidence for a prolonged shift towards higher variability in reproductive rates. The annual number of females attending colonies showed unusual swings during the iceberg period, a pattern that was apparently the consequence of changes in sea-ice conditions. In contrast to the dramatic effects that were recorded in nearby populations of emperor penguins, our results suggest that this unusual environmental event did not have an extreme impact on the population of seals in the short-term, as they managed to avoid survival costs and were able to rapidly re-achieve high levels of reproduction by the end of the perturbation. Nevertheless, population projections suggest that even this modest impact on reproductive rates could negatively affect the population in the long run if such events were to occur more frequently, as is predicted by models of climate change. PMID:23015628

  12. Antarctic-Wide Array of High-Resolution Ice Core Records Reveals Pervasive Lead Pollution Began in 1889 and Persists Today

    Science.gov (United States)

    McConnell, J. R.; Maselli, O. J.; Sigl, M.; Vallelonga, P.; Neumann, Thomas Allen; Anschutz, H.; Bales, R. C.; Curran, M. A. J.; Das, S. B.; Edwards, R.; Kipfstuhl, S.; Layman, L.; Thomas, E. R.

    2014-01-01

    Interior Antarctica is among the most remote places on Earth and was thought to be beyond the reach of human impacts when Amundsen and Scott raced to the South Pole in 1911. Here we show detailed measurements from an extensive array of 16 ice cores quantifying substantial toxic heavy metal lead pollution at South Pole and throughout Antarctica by 1889 - beating polar explorers by more than 22 years. Unlike the Arctic where lead pollution peaked in the 1970s, lead pollution in Antarctica was as high in the early 20th century as at any time since industrialization. The similar timing and magnitude of changes in lead deposition across Antarctica, as well as the characteristic isotopic signature of Broken Hill lead found throughout the continent, suggest that this single emission source in southern Australia was responsible for the introduction of lead pollution into Antarctica at the end of the 19th century and remains a significant source today. An estimated 660 t of industrial lead have been deposited over Antarctica during the past 130 years as a result of mid-latitude industrial emissions, with regional-to-global scale circulation likely modulating aerosol concentrations. Despite abatement efforts, significant lead pollution in Antarctica persists into the 21st century.

  13. Exploration in Newnes Plateau, NSW

    Energy Technology Data Exchange (ETDEWEB)

    Reynolds, P.; McQuade, C. [Pasminco Port Pirie Smelter, NSW (Australia)

    1999-06-01

    Underground coal mining operations in the Western Coalfields of NSW extend into the Newnes Plateau area. The Newnes Plateau area is known for its floral diversity and distinctive topography. A quantitative flora assessment concerning rehabilitation performance of exploration sites was undertaken to refine the environmental component of the exploration process and identify practices that may assist in an improved rate of regeneration within disturbed areas. This article briefly summarises the method and key outcomes of the study, undertaken as part of an Honours Degree program. Surveys of sites showed that plant height was reduced due to vehicle traffic compacting soil, and this also led to a reduced number of plant species and a reduced number of seedlings germinating. Percentage litter cover was found to be positively correlated with the number of species on the sites and the percent plant cover of the regenerating vegetation, shallow surface ripping is recommended to relieve soil compaction. Seeds should be collected from exploration sites prior to disturbance, particularly of species like Banksia and Haken that retain their seed on the plant. Seed should then be dispersed after work has finished. 1 fig., 2 photos.

  14. The Dynamic Plateau Monsoon Index and Its Association with General Circulation Anomalies

    Institute of Scientific and Technical Information of China (English)

    XUN Xueyi; HU Zeyong; MA Yaoming

    2012-01-01

    Based on monthly ECMWF reanalysis-Interim (ERA-Interim) reanalysis data,along with monthly precipitation and temperature data,the Dynamic Plateau Monsoon Index (DPMI) is defined.The results of a contrast analysis of the DPMI versus the Traditional Plateau Monsoon Index (TPMI) are described.The response of general circulation to northern Qinghai-Xizang Plateau summer monsoon anomalies and the correlation of the DPMI with general circulation anomalies are investigated.The results show that,the DPMI reflected meteorological elements better and depicted climate variation more accurately than the TPMI.In years when the plateau summer monsoon is strong,the low over the plateau and the trough near the eastern coast of Asia are deeper and higher than normal over South China.This correlation corresponds to two anomalous cyclones over the plateau and the eastern coast of Asia and an anomalous anticyclone in South China.The plateau and its adjacent regions are affected by anomalous southwesterly winds that transport more moisture to South China and cause more precipitation.The lower reaches of the Yangtze River appear to receive more precipitation by means of the strong westerly water vapor flow transported from the "large triangle affecting the region".In years when the plateau summer monsoon is weak,these are opposite.The plateau monsoon is closely related to the intensity and position of the South Asian high,and the existence of a teleconnection pattern in the mid-upper levels suggests a possible linl~ge of the East Asian monsoon and the Indian monsoon to the plateau summer monsoon.

  15. Centennial-scale Holocene climate variations amplified by Antarctic Ice Sheet discharge

    Science.gov (United States)

    Bakker, Pepijn; Clark, Peter U.; Golledge, Nicholas R.; Schmittner, Andreas; Weber, Michael E.

    2016-12-01

    Proxy-based indicators of past climate change show that current global climate models systematically underestimate Holocene-epoch climate variability on centennial to multi-millennial timescales, with the mismatch increasing for longer periods. Proposed explanations for the discrepancy include ocean-atmosphere coupling that is too weak in models, insufficient energy cascades from smaller to larger spatial and temporal scales, or that global climate models do not consider slow climate feedbacks related to the carbon cycle or interactions between ice sheets and climate. Such interactions, however, are known to have strongly affected centennial- to orbital-scale climate variability during past glaciations, and are likely to be important in future climate change. Here we show that fluctuations in Antarctic Ice Sheet discharge caused by relatively small changes in subsurface ocean temperature can amplify multi-centennial climate variability regionally and globally, suggesting that a dynamic Antarctic Ice Sheet may have driven climate fluctuations during the Holocene. We analysed high-temporal-resolution records of iceberg-rafted debris derived from the Antarctic Ice Sheet, and performed both high-spatial-resolution ice-sheet modelling of the Antarctic Ice Sheet and multi-millennial global climate model simulations. Ice-sheet responses to decadal-scale ocean forcing appear to be less important, possibly indicating that the future response of the Antarctic Ice Sheet will be governed more by long-term anthropogenic warming combined with multi-centennial natural variability than by annual or decadal climate oscillations.

  16. MID-MIOCENE SEQUENCES OF HIGH- AND MODERATE-MG VOLCANIC ROCKS IN VITIM PLATEAU, SOUTHERN SIBERIA: IMPACT OF A SUB-LITHOSPHERIC CONVECTIVE MATERIAL ON THE LITHOSPHERE

    OpenAIRE

    2015-01-01

    A comparative study of major elements, trace elements, and isotopes in high- and moderate-Mg volcanic sequences of 16–14 and 14–13 Ma, respectively, has been performed in the Bereya volcanic center. In the former (small volume) sequence, contaminated by crustal material basalts and trachybasalts of K–Na series were followed by uncontaminated basanites and basalts of transitional (K–Na–K) compositions and afterwards by picrobasalts and ba­salts of K series. From pressure estimates using equati...

  17. A glimpse into the deep of the Antarctic Polar Front - Diversity and abundance of abyssal molluscs

    Science.gov (United States)

    Jörger, K. M.; Schrödl, M.; Schwabe, E.; Würzberg, L.

    2014-10-01

    Our knowledge of the biodiversity and distribution patterns of benthic deep-sea faunas is still limited, with large parts of the world's abyss unexplored, lacking α-taxonomic data across oceans basins and especially of biogeographic transition zones between oceans. The Antarctic Polar Frontal Zone has been discussed as major biogeographic barrier hindering faunal exchange between Subantarctic and Antarctic provinces and conserving high rates of endemism in the Southern Ocean benthos. In the present study we report first, exploratory α-taxonomy on the malacofauna sampled by means of an epibenthic sledge from four bathyal respectively abyssal stations (2732-4327 m depth) in the vicinity of the Antarctic Polar Front during the SYSTCO II expedition (SYSTem COupling in the Southern Ocean, RV Polarstern cruise ANT XXVIII/3). We identified 58 distinct molluscan taxa based on external morphology ('morphospecies'); of the 33 taxa successfully assigned to described species 94% were previously reported from the Southern Ocean, but 24% exhibit distribution ranges crossing the Polar Front. One North Atlantic scaphopod is reported for the first time in Antarctic waters. Our study supports that the Antarctic Polar Front does not serve as effective barrier preventing gene flow in deep-sea molluscs. The present dataset shows the general characteristics of deep-sea sampling: patchiness in distribution and a high degree of singletons. Overall molluscan abundances were generally low ranging between 3.60 and 24.65 ind./1000 m², but in comparison with equatorial and subtropic abyssal basins, gastropod species richness and abundance were reaching high values similar to high Antarctic stations. Comparison between high productivity and low productivity zones along the Polar Front suggests increased abundances and species richness in high productivity zones. Intensified sampling is needed, however, to outweigh stochastic errors and to evaluate the influence of carbon flux as driving

  18. The Colorado Plateau IV: shaping conservation through science and management

    Science.gov (United States)

    Wakeling, Brian F.; Sisk, Thomas D.; van Riper, Charles

    2010-01-01

    Roughly centered on the Four Corners region of the southwestern United States, the Colorado Plateau covers some 130,000 square miles of sparsely vegetated plateaus, mesas, canyons, arches, and cliffs in Arizona, Utah, Colorado, and New Mexico. With elevations ranging from 3,000 to 14,000 feet, the natural systems found within the plateau are dramatically varied, from desert to alpine conditions. This book focuses on the integration of science and resource management issues in this unique and highly varied environment. Broken into three subsections, this volume addresses conservation biology, biophysical resources, and inventory and monitoring concerns. The chapters range in content, addressing conservation issues–past, present, and future–on the Colorado Plateau, measurement of human impacts on resources, grazing and wildland-urban interfaces, and tools and methods for monitoring habitats and species. An informative read for people interested in the conservation and natural history of the region, the book will also serve as a valuable reference for those people engaged in the management of cultural and biological resources of the Colorado Plateau, as well as scientists interested in methods and tools for land and resource management throughout the West.

  19. Mapping risk of plague in Qinghai-Tibetan Plateau, China.

    Science.gov (United States)

    Qian, Quan; Zhao, Jian; Fang, Liqun; Zhou, Hang; Zhang, Wenyi; Wei, Lan; Yang, Hong; Yin, Wenwu; Cao, Wuchun; Li, Qun

    2014-07-10

    Qinghai-Tibetan Plateau of China is known to be the plague endemic region where marmot (Marmota himalayana) is the primary host. Human plague cases are relatively low incidence but high mortality, which presents unique surveillance and public health challenges, because early detection through surveillance may not always be feasible and infrequent clinical cases may be misdiagnosed. Based on plague surveillance data and environmental variables, Maxent was applied to model the presence probability of plague host. 75% occurrence points were randomly selected for training model, and the rest 25% points were used for model test and validation. Maxent model performance was measured as test gain and test AUC. The optimal probability cut-off value was chosen by maximizing training sensitivity and specificity simultaneously. We used field surveillance data in an ecological niche modeling (ENM) framework to depict spatial distribution of natural foci of plague in Qinghai-Tibetan Plateau. Most human-inhabited areas at risk of exposure to enzootic plague are distributed in the east and south of the Plateau. Elevation, temperature of land surface and normalized difference vegetation index play a large part in determining the distribution of the enzootic plague. This study provided a more detailed view of spatial pattern of enzootic plague and human-inhabited areas at risk of plague. The maps could help public health authorities decide where to perform plague surveillance and take preventive measures in Qinghai-Tibetan Plateau.

  20. Health aspects of Antarctic tourism.

    Science.gov (United States)

    Prociv, P

    1998-12-01

    Increasing numbers of seaborne tourists are visiting Antarctica, with most coming from the United States (3503 in 1996-97), Germany (777), and Australia (680; cf. 356 in 1994-95 and 410 in 1995-96). The impression among travel medicine clinicians is that, each year, more prospective travelers seek advice about the health demands of this type of adventure, mostly relating to fitness for travel, exposure to extreme cold, hazards in ice and snow, and other potential health risks. This is a recent phenomenon. While a regular shipping service had been established between the Falklands and the subantarctic islands of South Georgia and the South Shetlands by 1924, the first documented tourists accompanied an Argentine expedition to the South Orkneys in 1933.1 Commercial airline flights over these islands and the Antarctic Peninsula began in 1956, from Chile, and recreational cruises to the Peninsula began in 1958. Tourist numbers subsequently grew slowly, for what was clearly an exclusive and very expensive undertaking, with few ships available for these hazardous voyages. From 1957 to 1993, 37,000 tourists visited by sea, most seeing only the Peninsula.2 The dramatic recent growth in numbers is a consequence of the collapse of the Soviet Union. The small fleet of ice-strengthened research vessels and working icebreakers, which was made redundant by withdrawal of central government support from isolated communities and military activities along the northern coast of Siberia (and from Antarctic research bases), now accounts for the bulk of charter-cruise tourism to Antarctica, at competitive prices. According to the International Association of Antarctica Tour Operators,3 7322 people traveled to Antarctica on commercially organized voyages in the 1996-97 season, and a record 10,000 shipborne visitors were expected for the 1997-98 season (November-March), traveling mainly from South America to the Peninsula on 15 ice-reinforced vessels, each carrying between 36 and 180

  1. Albicampo, variedad de frijol de temporal para Valles Altos de la Mesa Central Albicampo, rainfed bean variety for the High Valleys of the Central Mexican Plateau

    Directory of Open Access Journals (Sweden)

    Dagoberto Garza-García

    2010-12-01

    Full Text Available Albicampo (Phaseolus vulgaris L. es una variedad de grano negro opaco pequeño, tipo Jamapa, liberada en 2010 por el programa de frijol del Campo Experimental Valle de México (CEVAMEX del Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP. Se obtuvo mediante una cruza simple, utilizando selección masal hasta la generación F4. En la F5 se realizó selección individual para resistencia a enfermedades, calidad de grano y características agronómicas. Esta variedad se distingue de otras del mismo tipo comercial, por su alto rendimiento, excelente calidad culinaria y alto contenido de proteína, así plasticidad fenológica que le permite adaptarse a zonas, tanto de crítico como de buen temporal de lluvia. Es resistente a antracnosis (Colletotrichum lindemuthianum Sacc & Magn. Briosi & Cav., tizón común (Xanthomonas campestris pv phaseoli (Smith Dye y pudrición de raíz (Pythium y Rhizoctonia, y tolerante a roya (Uromyces appendiculatus (Pers.:Pers. Unger. Es de ciclo intermedio (105 a 115 días a madurez, su hábito de crecimiento es tipo III (indeterminado, con guía corta y flores moradas. Albicampo expresa su máximo potencial en áreas desde 2000 hasta 2400 msnm, suelo profundo y un mínimo de 350 mm de precipitación pluvial.Albicampo (Phaseolus vulgaris L., a small opaque dry bean seed variety from the Jamapa class, was released in 2010 by the bean program of the INIFAP's Campo Experimental Valle de Mexico. It was obtained through a simple cross, using bulk selection to the F4 followed by individual selection in F5 for disease, quality and agronomic traits. It distinguishes from other varieties of the same commercial class because of its high yield (>2 t ha-1, excellent cooking quality and high protein content, as well as phenological plasticity which enables it to adapt itself from critical to good rain season. It is resistant to anthracnose (Colletotrichum lindemuthianum Sacc & Magn. Briosi & Cav

  2. Reconciling projections of the Antarctic contribution to sea level rise

    Science.gov (United States)

    Edwards, Tamsin; Holden, Philip; Edwards, Neil; Wernecke, Andreas

    2017-04-01

    Two recent studies of the Antarctic contribution to sea level rise this century had best estimates that differed by an order of magnitude (around 10 cm and 1 m by 2100). The first, Ritz et al. (2015), used a model calibrated with satellite data, giving a 5% probability of exceeding 30cm by 2100 for sea level rise due to Antarctic instability. The second, DeConto and Pollard (2016), used a model evaluated with reconstructions of palaeo-sea level. They did not estimate probabilities, but using a simple assumption here about the distribution shape gives up to a 5% chance of Antarctic contribution exceeding 2.3 m this century with total sea level rise approaching 3 m. If robust, this would have very substantial implications for global adaptation to climate change. How are we to make sense of this apparent inconsistency? How much is down to the data - does the past tell us we will face widespread and rapid Antarctic ice losses in the future? How much is due to the mechanism of rapid ice loss ('cliff failure') proposed in the latter paper, or other parameterisation choices in these low resolution models (GRISLI and PISM, respectively)? How much is due to choices made in the ensemble design and calibration? How do these projections compare with high resolution, grounding line resolving models such as BISICLES? Could we reduce the huge uncertainties in the palaeo-study? Emulation provides a powerful tool for understanding these questions and reconciling the projections. By describing the three numerical ice sheet models with statistical models, we can re-analyse the ensembles and re-do the calibrations under a common statistical framework. This reduces uncertainty in the PISM study because it allows massive sampling of the parameter space, which reduces the sensitivity to reconstructed palaeo-sea level values and also narrows the probability intervals because the simple assumption about distribution shape above is no longer needed. We present reconciled probabilistic

  3. Latest tendency in the Antarctic ozone longitudinal distribution

    Science.gov (United States)

    Milinevsky, Gennadi; Grytsai, Asen; Klekociuk, Andrew; Evtushevsky, Olexander

    2014-05-01

    Significant ozone depletion was observed within the southern polar vortex during spring in the 1980s - early 1990s. Later, a stabilization in total ozone levels and ozone hole area has been observed. Atmosphere models predict a consequent recovery of the Antarctic ozone. Nevertheless, identification of the long-term processes is complicated by high interannual variability hiding their general regularities. In particular, a large stratosphere warming in 2002 resulted in significant increase in total ozone levels. The Antarctic ozone hole is formed inside polar stratospheric vortex, which is under influence of large-scale planetary waves. The components of the quasi-stationary wave (QSW) in the spring Southern Hemisphere (SH) stratosphere is mainly contributed by zonal wave number 1 which in turn determines the location of the total ozone extremes in spring: QSW minimum (maximum) is located in the South Atlantic (Australian) sector. In our work the satellite data of TOMS/Nimbus-7, TOMS/Earth Probe and OMI/Aura (http://ozoneaq.gsfc.nasa.gov/) have been used to investigate longitudinal distribution of the total ozone in Antarctic region. The gap in these satellite observations (1993-1995) was filled by the Multi-Sensor Reanalysis data (http://www.temis.nl/). Ozone distribution in the SH high and mid latitudes 80-50S were analyzed for southern spring season including months from September to November. The zonal distribution is considered along seven latitude circles from 80S to 50S with step of five degrees. To distinguish long-term processes and to obtain a quasi-stationary pattern, daily September - November ozone was averaged. Our previous study demonstrated a systematic eastward shift of the QSW minimum region. In this study, we extended the analysis to 2013 and obtained new results that exhibited a probable cessation in that eastward shift. Polynomial fit for all chosen latitudes is even evidence of a change in the tendency to opposite. It more time needs to

  4. Tibetan plateau river incision inhibited by glacial stabilization of the Tsangpo gorge.

    Science.gov (United States)

    Korup, Oliver; Montgomery, David R

    2008-10-09

    A considerable amount of research has focused on how and when the Tibetan plateau formed in the wake of tectonic convergence between India and Asia. Although far less enquiry has addressed the controls on river incision into the plateau itself, widely accepted theory predicts that steep fluvial knick points (river reaches with very steep gradients) in the eastern Himalayan syntaxis at the southeastern plateau margin should erode rapidly, driving a wave of incision back into the plateau. Preservation of the plateau edge thus presents something of a conundrum that may be resolved by invoking either differential rock uplift matching erosional decay, or other mechanisms for retarding bedrock river incision in this region where high stream power excludes the potential for aridity as a simple limit to dissection of the plateau. Here we report morphologic evidence showing that Quaternary depression of the regional equilibrium line altitude, where long-term glacier mass gain equals mass loss, was sufficient to repeatedly form moraine dams on major rivers: such damming substantially impeded river incision into the southeastern edge of the Tibetan plateau through the coupled effects of upstream impoundment and interglacial aggradation. Such glacial stabilization of the resulting highly focused river incision centred on the Tsangpo gorge could further contribute to initiating and accentuating a locus of rapid exhumation, known as tectonic anaeurysm.

  5. Numerical simulation of GPS observed clockwise rotation around the eastern Himalayan syntax in the Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    CAO dianLing; SHI YaoLin; ZHANG Huai; WANG Hui

    2009-01-01

    From Global Position System (GPS) measurements,there is a clockwise rotation around the eastern Himalayan syntax in the Tibetan Plateau.This phenomenon is difficult to be interpreted by simple two-dimensional modeling from a geodynamic point of view.Because of the extremely thick crust and the lower crust with relatively high temperature in the Tibetan Plateau,the lithospheric rheology in Tibet and surrounding areas present a complex structure,in general,the tectonic structure of the Tibetan Plateau consists of brittle upper crust,ductile lower crust,high viscosity lithospheric upper mantle,and low viscosity asthenosphere,the same as the case in many other continental regions.However,the lower crust in the Tibetan Plateau is much more ductile with a lower viscosity than those of its sur-roundings at the same depth,and the effective viscosity is low along the collision fault zone.In this study,we construct a three-dimensional Maxwell visco-elastic model in spherical coordinate system,and simulate the deformation process of the Tibetan Plateau driven by a continuous push from the Indian plate.The results show that the existence of the soft lower crust under the plateau makes the entire plateau uplift as a whole,and the Himalayas and the eastern Himalayan syntax uplift faster.Since the lower crust of surrounding blocks is harder except in the southeastern corner where the high-temperature material is much softer and forms an exit channel for material transfer,after the whole plateau reaches a certain height,the lower crustal and upper mantle material begins to move eastward or southeastward and drag the upper crust to behave same way.Thus,from the macroscopic point of view,a relative rigid motion of the plateau with a clockwise rotation around the eastern Himalayan syntax is developed.

  6. Antarctic Yeasts: Biodiversity and Potential Applications

    Science.gov (United States)

    Shivaji, S.; Prasad, G. S.

    This review is an attempt in cataloguing the diversity of yeasts in Antarctica, highlight their biotechnological potential and understand the basis of adaptation to low temperature. As of now several psychrophilic and psychrotolerant yeasts from Antarctic soils and marine waters have been characterized with respect to their growth characteristics, ecological distribution and taxonomic significance. Interestingly most of these species belonged to basidiomycetous yeasts which as a group are known for their ability to circumvent and survive under stress conditions. Simultaneously their possible role as work horses in the biotechnological industry was recognized due to their ability to produce novel enzymes and biomolecules such as agents for the breakdown of xenobiotics, and novel pharmaceutical chemi cals. The high activity of psychrophilic enzymes at low and moderate temperatures offers potential economic benefits. As of now lipases from Pseudozyma antarctica have been extensively studied to understand their unique thermal stability at 90°C and also because of its use in the pharmaceutical, agriculture, food, cosmetics and chemical industry. A few of the other enzymes which have been studied include extracellular alpha-amylase and glucoamylase from the yeast Pseudozyma antarctica (Candida antarctica), an extra-cellular protease from Cryptococcus humicola, an aspartyl proteinase from Cryptococcus humicola, a novel extracellular subtilase from Leucosporidium antarcticum, and a xylanase from Cryptococcus adeliensis

  7. Uranium-series dating of antarctic ice

    Energy Technology Data Exchange (ETDEWEB)

    Fireman, E.L.

    1986-01-01

    It is very interesting to date polar ice radiometrically. Bands of dust imbedded in ice are frequently observed in antarctic ice fields. This work focuses on dating ice samples with high dust contents by the uranium-series method. The author obtained uranium-series ages of 325 thousand (+/- 75) and 100 thousand (+/- 20) years for dusty ice samples from two sites in the main Allan Hills ice field. The dust-banded ice was collected from 50- to 100-centimeter depth at two sites, called Cul de Sac 100 and Cul de Sac 150. The particles in these samples were examined with an optical microscope and found to consist essentially (more than 95% of the particulates) of fine volcanic glass shards full of vesicles and microvesicles. Evidently the fine volcanic glass shards were deposited on snow, became incorporated in the ice, and moved with the ice to the Allan Hills sites. Ice samples with other types of particulates, such as terrestrial morraine, may also be amenable to uranium-series dating; however, it is difficult to date ice with less than 0.03 gram of fine particulates per kilogram of ice with their present technique. The uranium-series method can cover the age range from 10,000 to 600,000 years.

  8. Antarctic teleost immunoglobulins: more extreme, more interesting.

    Science.gov (United States)

    Coscia, Maria Rosaria; Varriale, Sonia; Giacomelli, Stefano; Oreste, Umberto

    2011-11-01

    We have investigated the immunoglobulin molecule and the genes encoding it in teleosts living in the Antarctic seas at the constant temperature of -1.86 °C. The majority of Antarctic teleosts belong to the suborder Notothenioidei (Perciformes), which includes only a few non-Antarctic species. Twenty-one Antarctic and two non-Antarctic Notothenioid species were included in our studies. We sequenced immunoglobulin light chains in two species and μ heavy chains, partially or totally, in twenty species. In the case of heavy chain, genomic DNA and the cDNA encoding the secreted and the membrane form were analyzed. From one species, Trematomus bernacchii, a spleen cDNA library was constructed to evaluate the diversity of VH gene segments. T. bernacchii IgM, purified from the serum and bile, was characterized. Homology Modelling and Molecular Dynamics were used to determine the molecular structure of T. bernacchii and Chionodraco hamatus immunoglobulin domains. This paper sums up the previous results and broadens them with the addition of unpublished data.

  9. Vegetation Changes in the Permafrost Regions of the Qinghai-Tibetan Plateau from 1982-2012: Different Responses Related to Geographical Locations and Vegetation Types in High-Altitude Areas.

    Science.gov (United States)

    Wang, Zhiwei; Wang, Qian; Wu, Xiaodong; Zhao, Lin; Yue, Guangyang; Nan, Zhuotong; Wang, Puchang; Yi, Shuhua; Zou, Defu; Qin, Yu; Wu, Tonghua; Shi, Jianzong

    2017-01-01

    The Qinghai-Tibetan Plateau (QTP) contains the largest permafrost area in a high-altitude region in the world, and the unique hydrothermal environments of the active layers in this region have an important impact on vegetation growth. Geographical locations present different climatic conditions, and in combination with the permafrost environments, these conditions comprehensively affect the local vegetation activity. Therefore, the responses of vegetation to climate change in the permafrost region of the QTP may be varied differently by geographical location and vegetation condition. In this study, using the latest Global Inventory Modeling and Mapping Studies (GIMMS) Normalized Difference Vegetation Index (NDVI) product based on turning points (TPs), which were calculated using a piecewise linear model, 9 areas within the permafrost region of the QTP were selected to investigate the effect of geographical location and vegetation type on vegetation growth from 1982 to 2012. The following 4 vegetation types were observed in the 9 selected study areas: alpine swamp meadow, alpine meadow, alpine steppe and alpine desert. The research results show that, in these study areas, TPs mainly appeared in 2000 and 2001, and almost 55.1% and 35.0% of the TPs were located in 2000 and 2001. The global standardized precipitation evapotranspiration index (SPEI) and 7 meteorological variables were selected to analyze their correlations with NDVI. We found that the main correlative variables to vegetation productivity in study areas from 1982 to 2012 were precipitation, surface downward long-wave radiation and temperature. Furthermore, NDVI changes exhibited by different vegetation types within the same study area followed similar trends. The results show that regional effects rather than vegetation type had a larger impact on changes in vegetation growth in the permafrost regions of the QTP, indicating that climatic factors had a larger impact in the permafrost regions than the

  10. Petrogenesis and tectonic implications of the high-K Alamas calc-alkaline granitoids at the northwestern margin of the Tibetan Plateau: Geochemical and Sr-Nd-Hf-O isotope constraints

    Science.gov (United States)

    Zhang, Qichao; Liu, Yan; Huang, He; Wu, Zhenhan; Zhou, Qing

    2016-09-01

    The Alamas granitoid pluton in the eastern part of the Western Kunlun Orogen, the northwestern margin of the Tibetan Plateau, is composed of quartz diorite. Zircon separates from the pluton has SIMS U-Pb age of ∼446 Ma. Rocks from the pluton have a narrow range of SiO2 (56.84-62.57 wt%), MgO (1.76-2.94 wt%), and total alkalis (Na2O + K2O = 5.14-9.59 wt%), and are metaluminous and high-K calc-alkaline to shoshonitic in composition. They are enriched in light rare earth elements (LREEs), with (La/Yb)N = 14-25, and show weakly negative Eu anomalies. These rocks are relatively enriched in Sr (472-676 ppm) and Ba (435-2388 ppm), and depleted in Nb, Ta, Th, and Ti. Their εNd(t) values range from -6.4 to -8.4, and (87Sr/86Sr)i = 0.7184-0.7200. Zircons from the pluton show εHf(t) values of -1.4 to -8.8, and δ18O = 6.4-9.0‰. Geochemical data indicate that the granitoids were likely derived from the reworking of an ancient, deep crustal source, influenced by a minor mantle-derived component. Magmatic differentiation was dominated by the fractional crystallization of hornblende, biotite, and accessory minerals such as apatite, allanite, and Fe-Ti oxides. In summary, the Late Ordovician Alamas pluton is an I-type granitoid that was emplaced in a post-collisional environment, suggesting that this tectonic stage had already initiated prior to ∼445 Ma.

  11. Antarctic Ice Sheet Slope and Aspect Based on Icesat's Repeat Orbit Measurement

    Science.gov (United States)

    Yuan, L.; Li, F.; Zhang, S.; Xie, S.; Xiao, F.; Zhu, T.; Zhang, Y.

    2017-09-01

    Accurate information of ice sheet surface slope is essential for estimating elevation change by satellite altimetry measurement. A study is carried out to recover surface slope of Antarctic ice sheet from Ice, Cloud and land Elevation Satellite (ICESat) elevation measurements based on repeat orbits. ICESat provides repeat ground tracks within 200 meters in cross-track direction and 170 meters in along-track direction for most areas of Antarctic ice sheet. Both cross-track and along-track surface slopes could be obtained by adjacent repeat ground tracks. Combining those measurements yields a surface slope model with resolution of approximately 200 meters. An algorithm considering elevation change is developed to estimate the surface slope of Antarctic ice sheet. Three Antarctic Digital Elevation Models (DEMs) were used to calculate surface slopes. The surface slopes from DEMs are compared with estimates by using in situ GPS data in Dome A, the summit of Antarctic ice sheet. Our results reveal an average surface slope difference of 0.02 degree in Dome A. High resolution remote sensing images are also used in comparing the results derived from other DEMs and this paper. The comparison implies that our results have a slightly better coherence with GPS observation than results from DEMs, but our results provide more details and perform higher accuracy in coastal areas because of the higher resolution for ICESat measurements. Ice divides are estimated based on the aspect, and are weakly consistent with ice divides from other method in coastal regions.

  12. Concentration of trace elements in feathers of three Antarctic penguins: Geographical and interspecific differences

    Energy Technology Data Exchange (ETDEWEB)

    Jerez, Silvia [Area de Toxicologia, Facultad de Veterinaria, Universidad de Murcia, Campus de Espinardo, 30100 Murcia (Spain); Motas, Miguel, E-mail: motas@um.es [Area de Toxicologia, Facultad de Veterinaria, Universidad de Murcia, Campus de Espinardo, 30100 Murcia (Spain); Palacios, Maria Jose; Valera, Francisco [Departamento de Ecologia Funcional y Evolutiva, Estacion Experimental de Zonas Aridas, CSIC, Carretera de Sacramento s/n, 04120 La Canada de San Urbano, Almeria (Spain); Cuervo, Jose Javier; Barbosa, Andres [Departamento de Ecologia Funcional y Evolutiva, Estacion Experimental de Zonas Aridas, CSIC, Carretera de Sacramento s/n, 04120 La Canada de San Urbano, Almeria (Spain); Departamento de Ecologia Evolutiva, Museo Nacional de Ciencias Naturales, CSIC, C/Jose Gutierrez Abascal 2, 28006 Madrid (Spain)

    2011-10-15

    Antarctica is often considered as one of the last pristine regions, but it could be affected by pollution at global and local scale. Concentrations of Al, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Cd and Pb were determinated by ICP-MS in feathers (n = 207 individuals) of gentoo, chinstrap and Adelie penguin collected in 8 locations throughout the Antarctic Peninsula (2006-2007). The highest levels of several elements were found in samples from King George Island (8.08, 20.29 and 1.76 {mu}g g{sup -1} dw for Cr, Cu and Pb, respectively) and Deception Island (203.13, 3.26 and 164.26 {mu}g g{sup -1} dw for Al, Mn and Fe, respectively), where probably human activities and large-scale transport of pollutants contribute to increase metal levels. Concentrations of Cr, Mn, Cu, Se or Pb, which are similar to others found in different regions of the world, show that some areas in Antarctica are not utterly pristine. - Highlights: > We study levels of trace elements in feathers of Antarctic penguins. > Eight different rookeries throughout the Antarctic Peninsula were sampled. > Interspecific (gentoo, chinstrap, Adelie) and geographical differences were tested. > Relatively high metal levels were found in areas with major human presence. > Penguin feather can be useful for metals monitoring in the Antarctic environment. - Trace element levels in feathers of three penguin species from the Antarctic Peninsula indicate the presence of pollution in certain locations.

  13. Diversity of the aerobic anoxygenic phototrophy genepufM in Arctic and Antarctic coastal seawaters

    Institute of Scientific and Technical Information of China (English)

    ZENG Yinxin; DONG Peiyan; QIAO Zongyun; ZHENG Tianling

    2016-01-01

    Aerobic anoxygenic phototrophic (AAP) bacteria serve important functions in marine carbon and energy cycling because of their capability to utilize dissolved organic substrates and harvest light energy. AAP bacteria are widely distributed in marine environments, and their diversity has been examined in marine habitats. However, information about AAP bacteria at high latitudes remains insufficient to date. Therefore, this study determined the summer AAP bacterial diversity in Arctic Kongsfjorden and in the Antarctic coastal seawater of King George Island on the basis ofpufM, a gene that encodes a pigment-binding protein subunit of the reaction center complex. FourpufM clone libraries were constructed, and 674 positive clones were obtained from four investigated stations (two in Kongsfjorden and two in the Antarctic Maxwell Bay). Arctic clones were clustered within theAlphaproteobacteria, whereas Antarctic clones were classified into theAlphaproteobacteria and Betaproteobacteria classes.Rhodobacteraceae-likepufM genes dominated in all samples. In addition, sequences closely related topufM encoded on a plasmid inSulfitobacter guttiformis were predominant in both Arctic and Antarctic samples. This result indicates the transpolar or even global distribution ofpufM genes in marine environments. Meanwhile, differences between the Arctic and Antarctic sequences may prove polar endemism. These results indicate the important role ofRhodobacteraceae as AAP bacteria in bipolar coastal waters.

  14. Lethal and behavioural impacts of diesel and fuel oil on the Antarctic amphipod Paramoera walkeri.

    Science.gov (United States)

    Brown, Kathryn E; King, Catherine K; Harrison, Peter L

    2017-03-03

    Toxicity testing with Antarctic species is required for risk assessment of fuel spills in Antarctic coastal waters. The lethal and sub-lethal (movement behaviour) sensitivity of adults and juveniles of the Antarctic amphipod Paramoera walkeri to the water accommodated fractions (WAF) of three fuels were estimated in extended duration tests at -1°C to 21 d. Response of P. walkeri for lethal hydrocarbon concentrations was slow, with LC50s first able to be estimated at 7 d for adults exposed to Special Antarctic Blend diesel (SAB), which had the highest hydrocarbon concentrations of the three fuel WAFs. Juveniles showed greater response to marine gas oil (MGO) and intermediate residual fuel oil (IFO 180) at longer exposure durations and were most sensitive at 21 d to IFO 180 (LC50 = 12 µg/L). Adults were initially more sensitive than juveniles; however, at 21 d juveniles were more than twice as sensitive as adults to SAB (LC50 = 153 µg/L and 377 µg/L respectively). Significant effects on movement behaviour were evident at earlier time points and lower concentrations than was mortality in all three fuel WAFs, and juveniles were highly sensitive to sub-lethal effects of MGO. These first estimates of Antarctic amphipod sensitivity to diesel and fuel oils in seawater contribute to development of ecologically relevant water quality guidelines for management of hydrocarbon contamination in the region. This article is protected by copyright. All rights reserved.

  15. Rapid coupling of Antarctic temperature and atmospheric CO2 during deglaciation

    Directory of Open Access Journals (Sweden)

    T. D. van Ommen

    2012-02-01

    Full Text Available Antarctic ice cores provide clear evidence of a close coupling between variations in Antarctic temperature and the atmospheric concentration of CO2 during the glacial/interglacial cycles of the past 800 thousand years. Precise information on the relative timing of the temperature and CO2 changes can assist in refining our understanding of the physical processes involved in this coupling. Here, we focus on the last deglaciation, 19 000 to 11 000 years before present, during which CO2 concentrations increased by ~80 parts per million by volume and Antarctic temperature increased by ~10 °C. Utilising a recently developed proxy for regional Antarctic temperature, derived from five near-coastal ice cores, and two ice core CO2 records with high dating precision, we show that the increase in CO2 lagged the increase in regional Antarctic temperature by only 0–400 years. This new value for the lag, consistent for both CO2 records, implies a faster feedback between temperature and CO2 than the centennial to millennial-scale lags suggested by previous studies.

  16. Molecular clock evidence for survival of Antarctic cyanobacteria (Oscillatoriales, Phormidium autumnale) from Paleozoic times.

    Science.gov (United States)

    Strunecký, Otakar; Elster, Josef; Komárek, Jiří

    2012-11-01

    Cyanobacteria are well adapted to freezing and desiccation; they have been proposed as possible survivors of comprehensive Antarctic glaciations. Filamentous types from the order Oscillatoriales, especially the species Phormidium autumnale Kützing ex Gomont 1892, have widely diverse morphotypes that dominate in Antarctic aquatic microbial mats, seepages, and wet soils. Currently little is known about the dispersion of cyanobacteria in Antarctica and of their population history. We tested the hypothesis that cyanobacteria survived Antarctic glaciations directly on site after the Gondwana breakup by using the relaxed and strict molecular clock in the analysis of the 16S rRNA gene. We estimated that the biogeographic history of Antarctic cyanobacteria belonging to P. autumnale lineages has ancient origins. The oldest go further back in time than the breakup of Gondwana and originated somewhere on the supercontinent between 442 and 297 Ma. Enhanced speciation rate was found around the time of the opening of the Drake Passage (c. 31-45 Ma) with beginning of glaciations (c. 43 Ma). Our results, based primarily on the strains collected in maritime Antarctica, mostly around James Ross Island, support the hypothesis that long-term survival took place in glacial refuges. The high morphological diversification of P. autumnale suggested the coevolution of lineages and formation of complex associations with different morphologies, resulting in a specific endemic Antarctic cyanobacterial flora.

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

    Science.gov (United States)

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

    2017-01-01

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

  18. Twentieth century bipolar seesaw of the Arctic and Antarctic surface air temperatures

    Science.gov (United States)

    Chylek, Petr; Folland, Chris K.; Lesins, Glen; Dubey, Manvendra K.

    2010-04-01

    Understanding the phase relationship between climate changes in the Arctic and Antarctic regions is essential for our understanding of the dynamics of the Earth's climate system. In this paper we show that the 20th century de-trended Arctic and Antarctic temperatures vary in anti-phase seesaw pattern - when the Arctic warms the Antarctica cools and visa versa. This is the first time that a bi-polar seesaw pattern has been identified in the 20th century Arctic and Antarctic temperature records. The Arctic (Antarctic) de-trended temperatures are highly correlated (anti-correlated) with the Atlantic Multi-decadal Oscillation (AMO) index suggesting the Atlantic Ocean as a possible link between the climate variability of the Arctic and Antarctic regions. Recent accelerated warming of the Arctic results from a positive reinforcement of the linear warming trend (due to an increasing concentration of greenhouse gases and other possible forcings) by the warming phase of the multidecadal climate variability (due to fluctuations of the Atlantic Ocean circulation).

  19. Genetic population structure in the Antarctic benthos: insights from the widespread amphipod, Orchomenella franklini.

    Directory of Open Access Journals (Sweden)

    Helena Phoenix Baird

    Full Text Available Currently there is very limited understanding of genetic population structure in the Antarctic benthos. We conducted one of the first studies of microsatellite variation in an Antarctic benthic invertebrate, using the ubiquitous amphipod Orchomenella franklini (Walker, 1903. Seven microsatellite loci were used to assess genetic structure on three spatial scales: sites (100 s of metres, locations (1-10 kilometres and regions (1000 s of kilometres sampled in East Antarctica at Casey and Davis stations. Considerable genetic diversity was revealed, which varied between the two regions and also between polluted and unpolluted sites. Genetic differentiation among all populations was highly significant (F(ST = 0.086, R(ST = 0.139, p<0.001 consistent with the brooding mode of development in O. franklini. Hierarchical AMOVA revealed that the majority of the genetic subdivision occurred across the largest geographical scale, with N(em≈1 suggesting insufficient gene flow to prevent independent evolution of the two regions, i.e., Casey and Davis are effectively isolated. Isolation by distance was detected at smaller scales and indicates that gene flow in O. franklini occurs primarily through stepping-stone dispersal. Three of the microsatellite loci showed signs of selection, providing evidence that localised adaptation may occur within the Antarctic benthos. These results provide insights into processes of speciation in Antarctic brooders, and will help inform the design of spatial management initiatives recently endorsed for the Antarctic benthos.

  20. Antarctic station life: The first 15 years of mixed expeditions to the Antarctic

    Science.gov (United States)

    Sarris, Aspa

    2017-02-01

    This study examined the experiences of women who lived and worked on remote and isolated Antarctic stations for up to 15 months at a time. The study employed purposeful sampling and a longitudinal - processual approach to study women's experiences over the first 15 years of mixed gender Antarctic expeditions. The retrospective analysis was based on a semi-structured interview administered to 14 women upon their return to Australia. The results showed that women referred to the natural physical Antarctic environment as one of the best aspects of their experience and the reason they would recommend the Antarctic to their friends as a good place to work. In describing the worst aspect of their experience, women referred to aspects of Antarctic station life, including: (i) the male dominated nature of station culture; (ii) the impact of interpersonal conflict, including gender based conflict and friction between scientists and trades workers; and (iii) the lack of anonymity associated with living and working with the same group of individuals, mainly men, for up to 12 months or more. The results are discussed within the context of the evolution of Antarctic station culture and recommendations are made in terms of the demography of expeditions, expeditioner selection and recruitment and the ongoing monitoring of Antarctic station culture. The study presents a framework that can be applied to groups and teams living and working in analogous isolated, confined and extreme work environments, including outer space missions.

  1. 76 FR 9849 - Comprehensive Environmental Evaluations for Antarctic Activities

    Science.gov (United States)

    2011-02-22

    .... SUPPLEMENTARY INFORMATION: Article 3 of Annex I to the Protocol on Environmental Protection to the Antarctic Treaty requires the preparation of a CEE for any proposed Antarctic activity likely to have more than a... Comprehensive Environmental Evaluations for Antarctic Activities SUMMARY: The Department of State gives...

  2. Major and trace element partitioning between dissolved and particulate phases in Antarctic surface snow.

    Science.gov (United States)

    Grotti, M; Soggia, F; Ardini, F; Magi, E

    2011-09-01

    In order to provide a new insight into the Antarctic snow chemistry, partitioning of major and trace elements between dissolved and particulate (i.e. insoluble particles, >0.45 μm) phases have been investigated in a number of coastal and inland snow samples, along with their total and acid-dissolvable (0.5% nitric acid) concentrations. Alkaline and alkaline-earth elements (Na, K, Ca, Mg, Sr) were mainly present in the dissolved phase, while Fe and Al were predominantly associated with the particulate matter, without any significant difference between inland and coastal samples. On the other hand, partitioning of trace elements depended on the sampling site position, showing a general decrease of the particulate fraction by moving from the coast to the plateau. Cd, Cu, Pb and Zn were for the most part in the dissolved phase, while Cr was mainly associated with the particulate fraction. Co, Mn and V were equally distributed between dissolved and particulate phases in the samples collected from the plateau and preferentially associated with the particulate in the coastal samples. The correlation between the elements and the inter-sample variability of their concentration significantly decreased for the plateau samples compared to the coastal ones, according to a change in the relative contribution of the metal sources and in good agreement with the estimated marine and crustal enrichment factors. In addition, samples from the plateau were characterised by higher enrichment factors of anthropogenic elements (Cd, Cr, Cu, Pb and Zn), compared to the coastal area. Finally, it was observed that the acid-dissolvable metal concentrations were generally lower than the total concentration values, showing that the acid treatment can dissolve only a given fraction of the metal associated with the particulate (<20% for iron and aluminium).

  3. Extensional Seismogenic Stress and Tectonic Movement on the Central Region of the Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    Jiren Xu

    2009-01-01

    Full Text Available Various earthquake fault types, mechanism solutions and stress fields, as well as GPS and geothermal data are analyzed for the study of the crustal movements on the Tibetan plateau and their tectonic implications. The results show that a lot of the normal faulting type-event concentrated at altitudes greater than 4000 m on the central Tibetan plateau. The altitudes concentrating normal faulting type-events can be zoned two parts: the western part, the Lhasa block, and the eastern part, the Qiangtang-Changdu region. The azimuths of T-axes are in a general E-W direction in the Lhasa block and NW-SE or NNW-SSE in the Qiangtang-Changdu region at the altitudes of the Tibetan plateau. The tensional stresses in E-W direction and NW-SE direction predominate normal faulting earthquake occurrence in the Lhasa block and the Qiangtang-Changdu region, respectively. The slipping displacements of the normal-faulting-type events have great components in near E-W direction and NW-SE direction in the Lhasa block and the Qiangtang-Changdu region, respectively. The extensions are probably an eastward or southeastward extensional motion, being mainly tectonic activity phenomena in the plateau altitudes. The extensional motions due to normal-fault earthquakes are important tectonic activity regimes on the high altitudes of the plateau. The easterly crustal extensions on the plateau are attributable to the gravitational collapse of the high plateau and eastward extrusion of hotter mantle materials beneath the eastern boundary of the plateau. Numbers of thrust-fault and strike-slip-fault earthquakes with strong compressive stress in a general NNE-SSW direction occur on the edges of the plateau.

  4. Comprehensive analysis of an Antarctic bacterial community with the adaptability of growth at higher temperatures than those in Antarctica.

    Science.gov (United States)

    Hosoi-Tanabe, Shoko; Zhang, Hongyan; Zhu, Daochen; Nagata, Shinichi; Ban, Syuhei; Imura, Satoshi

    2010-06-01

    To investigate the adaptability to higher temperatures of Antarctic microorganisms persisting in low temperature conditions for a long time, Antarctic lake samples were incubated in several selection media at 25 degrees C and 30 degrees C. The microorganisms did not grow at 30 degrees C; however, some of them grew at 25 degrees C, indicating that the bacteria in Antarctic have the ability to grow at a wide range of temperatures. Total DNA was extracted from these microorganisms and amplified using the bacteria-universal primers. The amplified fragments were cloned, and randomly selected 48 clones were sequenced. The sequenced clones showed high similarity to the alpha-subdivision of the Proteobacteria with specific affinity to the genus Agrobacterium, Caulobacter and Brevundimonas, the ss-subdivision of Proteobacteria with specific affinity to the genus Cupriavidus, and Bacillus of the phylum Firmicutes. These results showed the presence of universal genera, suggesting that the bacteria in the Antarctic lake were not specific to this environment.

  5. Antarctic “quiet” site stirs debate

    Science.gov (United States)

    Simarski, Lynn Teo

    Geophysicists from the United States and New Zealand plan to meet in the coming months to assess the electromagnetic pollution of an Antarctic site especially designated for research. U.S. scientists charge that a satellite Earth station erected apparently inside the preserve by New Zealand's Telecom company could interfere with experiments on the ionosphere and magnetosphere (Eos, April 28, 1992). The Site of Special Scientific Interest at Arrival Heights, the only Antarctic preserve specifically for physical science, is located near the U.S. McMurdo and New Zealand Scott bases.Debate over the Telecom facility inter-twines diplomatic and scientific issues. One question is whether the station violates the Antarctic treaty. Secondly, does it actually impair research at the site—or could it harm future experiments? To deepen the imbroglio, those involved from both nations say that transmissions from sources off-site also interfere with research—raising doubts about how pristine the site really is.

  6. NSF's role in Antarctic environment scrutinized

    Science.gov (United States)

    Bush, Susan

    In the last few years, the National Science Foundation has come under criticism by environmental groups for inadequate stewardship in the U.S. Antarctic Program's environmental issues. Since 1978, NSF was given full responsibility, by Executive Order, for budgeting and managing the entire U.S. national program in Antarctica, including logistics support. NSF has also been responsible for the compliance of the U.S. Antarctic Program with environmental protection measures agreed to by the Antarctic Treaty nations. Specifically under fire by environmentalists have been NSF's maintenance of a land-fill, open-air burning of solid waste, and the removal of toxic substances. According to Peter E. Wilkniss, director of the Division of Polar Programs at NSF, open burning is no longer taking place and will not be allowed in the future.

  7. Open-ocean barriers to dispersal: a test case with the Antarctic Polar Front and the ribbon worm Parborlasia corrugatus (Nemertea: Lineidae).

    Science.gov (United States)

    Thornhill, Daniel J; Mahon, Andrew R; Norenburg, Jon L; Halanych, Kenneth M

    2008-12-01

    Open-ocean environments provide few obvious barriers to the dispersal of marine organisms. Major currents and/or environmental gradients potentially impede gene flow. One system hypothesized to form an open-ocean dispersal barrier is the Antarctic Polar Front, an area characterized by marked temperature change, deep water, and the high-flow Antarctic Circumpolar current. Despite these potential isolating factors, several invertebrate species occur in both regions, including the broadcast-spawning nemertean worm Parborlasia corrugatus. To empirically test for the presence of an open-ocean dispersal barrier, we sampled P. corrugatus and other nemerteans from southern South America, Antarctica, and the sub-Antarctic islands. Diversity was assessed by analyzing mitochondrial 16S rRNA and cytochrome c oxidase subunit I sequence data with Bayesian inference and tcs haplotype network analysis. Appropriate neutrality tests were also employed. Although our results indicate a single well-mixed lineage in Antarctica and the sub-Antarctic, no evidence for recent gene flow was detected between this population and South American P. corrugatus. Thus, even though P. corrugatus can disperse over large geographical distances, physical oceanographic barriers (i.e. Antarctic Polar Front and Antarctic Circumpolar Current) between continents have likely restricted dispersal over evolutionary time. Genetic distances and haplotype network analysis between South American and Antarctic/sub-Antarctic P. corrugatus suggest that these two populations are possibly two cryptic species.

  8. Compressive Tectonics around Tibetan Plateau Edges

    Institute of Scientific and Technical Information of China (English)

    Zhao Zhixin; Xu Jiren

    2009-01-01

    Various earthquake fault types, mechanism solutions, stress field, and other geophysical data were analyzed for study on the crust movement in the Tibetan plateau and its tectonic implications. The results show that numbers of thrust fault and strike-slip fault type earthquakes with strong compressive stress near NNE-SSW direction occurred in the edges around the plateau except the eastern boundary. Some normal faulting type earthquakes concentrate in the Central Tibetan plateau. The strikes of fault planes of thrust and strike-slip faulting earthquakes are almost in the E-W direction based on the analyses of the Wulff stereonet diagrams of fault plane solutions. This implies that the dislocation slip vectors of the thrust and strike-slip faulting type events have quite great components in the N-S direction. The compression motion mainly probably plays the tectonic active regime around the plateau edges. The compressive stress in N-S or NE-SW directions predominates earthquake occurrence in the thrust and strike-slip faulting event region around the plateau. The compressive motion around the Tibetan plateau edge is attributable to the northward motion of the Indian subcontinent plate. The northward motion of the Tibetan plateau shortened in the N-S direction encounters probably strong obstructions at the western and northern margins.

  9. Overview of mercury measurements in the Antarctic troposphere

    Directory of Open Access Journals (Sweden)

    A. Dommergue

    2009-12-01

    contribution of this unique reactivity occurring in polar atmospheres to the global budget of atmospheric Hg and the role played by snow and ice surfaces of these regions are important issues. This paper presents a review of atmospheric mercury studies conducted in the Antarctic troposphere, both at coastal locations and on the Antarctic Plateau since 1985. Our current understanding of atmospheric reactivity in this region is also presented.

  10. Overview of mercury measurements in the Antarctic troposphere

    Directory of Open Access Journals (Sweden)

    A. Dommergue

    2010-04-01

    may be recycled. Therefore, the contribution of this unique reactivity occurring in polar atmospheres to the global budget of atmospheric mercury, and the role played by snow and ice surfaces of these regions, are important issues. This paper presents a review of atmospheric mercury studies conducted in the Antarctic troposphere, both at coastal locations and on the Antarctic Plateau since 1985. Our current understanding of atmospheric reactivity in this region is also presented.

  11. The hemoglobins of the cold-adapted Antarctic teleost Cygnodraco mawsoni.

    Science.gov (United States)

    Caruso, C; Rutigliano, B; Romano, M; di Prisco, G

    1991-06-24

    The blood of the teleost Cygnodraco mawsoni, of the endemic Antarctic family Bathydraconidae, contains a major hemoglobin (Hb 1), accompanied by a minor component (Hb 2, about 5% of total). The two hemoglobins have identical alpha chains and differ by the beta chain. The complete amino acid sequence of the three chains has been elucidated, thus establishing the primary structure of both hemoglobins. The sequences show a 53-65% identity with non-Antarctic poikilotherm fish species; on the other hand, a very high degree of similarity (83-88%) has been found between Hb 1 and the major component of another Antarctic species of a different family. The hemoglobin functional properties relative to oxygen binding have been investigated in intact erythrocytes, 'stripped' hemolysate and purified components of C. mawsoni. The hemoglobins display the Bohr and Root effects, indicating fine regulation of oxygen binding by pH and by the physiological effectors organic phosphates.

  12. The impact of tourists on Antarctic tardigrades: an ordination-based model

    Directory of Open Access Journals (Sweden)

    Sandra J. McInnes

    2013-05-01

    Full Text Available Tardigrades are important members of the Antarctic biota yet little is known about their role in the soil fauna or whether they are affected by anthropogenic factors. The German Federal Environment Agency commissioned research to assess the impact of human activities on soil meiofauna at 14 localities along the Antarctic peninsula during the 2009/2010 and 2010/2011 austral summers. We used ordination techniques to re-assess the block-sampling design used to compare areas of high and low human impact, to identify which of the sampled variables were biologically relevant and/or demonstrated an anthropogenic significance. We found the most significant differences between locations, reflecting local habitat and vegetation factor, rather than within-location anthropogenic impact. We noted no evidence of exotic imports but report on new maritime Antarctic sample sites and habitats.

  13. Mysterious iodine-overabundance in Antarctic meteorites

    Science.gov (United States)

    Dreibus, G.; Waenke, H.; Schultz, L.

    1986-01-01

    Halogen as well as other trace element concentrations in meteorite finds can be influenced by alteration processes on the Earth's surface. The discovery of Antarctic meteorites offered the opportunity to study meteorites which were kept in one of the most sterile environment of the Earth. Halogen determination in Antartic meteorites was compared with non-Antarctic meteorites. No correlation was found between iodine concentration and the weathering index, or terrestrial age. The halogen measurements indicate a contaminating phase rich in iodine and also containing chlorine. Possible sources for this contamination are discussed.

  14. OSIRIS observations of a tongue of NOx in the lower stratosphere at the Antarctic vortex edge: comparison with a high-resolution simulation from the Global Environmental Multiscale (GEM) model

    Energy Technology Data Exchange (ETDEWEB)

    Sioris, C.E.; McLinden, C.A.; Rochon, Y.J.; McElroy, C.T. [Environment Canada, Toronto, ON (Canada). Atmospheric Science and Technology Directorate; Chabrillat, S. [Belgian Inst. for Space Aeronomy, Brussels (Belgium); Haley, C.S. [York Univ., Toronto, ON (Canada); Menard, R.; Charron, M. [Environment Canada, Dorval, ON (Canada). Atmospheric Science and Technology Directorate

    2007-11-15

    An optical spectrograph and infrared imager system (OSIRIS) aboard the Odin satellite measures limb-scattered sunlight in the 280 to 810 nm range. This paper addressed the challenge of interpreting nitrogen dioxide (NO{sub 2}) profile observations in the polar lower stratosphere. Interpretations of these profile observations can be facilitated by first converting the measurements to NO{sub x} using a photochemical model in order to compare directly with simulated NO{sub x} from a 3-dimensional chemical transport model such as the Global Environmental Multiscale (GEM) model. In this study, GEM was used to simulate a tongue of NO{sub x} observed by OSIRIS as it circulated inside the Antarctic vortex edge. The objective was to clarify one of several OSIRIS observations of enhanced lower stratospheric NO{sub 2} in the Antarctic in early austral spring. Another objective was to demonstrate the variability in lower stratospheric NO{sub x} at polar latitudes due to dynamical processes. Selected NOx profiles of the Antarctic lower stratosphere inferred from OSIRIS NO{sub 2} observations were presented from the austral spring of 2003. A tongue of NOx at 100 hPa was observed, with a concentration typical of the middle stratosphere. GEM simulations revealed that this small-scale tongue of NOx-rich air descended into the lower stratosphere. The tongue was formed as a result of a Rossby wave breaking, transporting NOx from the pole, where larger concentrations had recently appeared, to the edge of the vortex. A detailed illustration of the 3-dimensional structure of the breaking wave was also presented. 17 refs., 1 tab., 10 figs.

  15. Antarctic volcanoes: A remote but significant hazard

    Science.gov (United States)

    Geyer, Adelina; Martí, Alex; Folch, Arnau; Giralt, Santiago

    2017-04-01

    Ash emitted during explosive volcanic eruptions can be dispersed over massive areas of the globe, posing a threat to both human health and infrastructures, such as the air traffic. Some of the last eruptions occurred during this decade (e.g. 14/04/2010 - Eyjafjallajökull, Iceland; 24/05/2011-Grímsvötn, Iceland; 05/06/2011-Puyehue-Cordón Caulle, Chile) have strongly affected the air traffic in different areas of the world, leading to economic losses of billions of euros. From the tens of volcanoes located in Antarctica, at least nine are known to be active and five of them have reported volcanic activity in historical times. However, until now, no attention has been paid to the possible social, economical and environmental consequences of an eruption that would occur on high southern latitudes, perhaps because it is considered that its impacts would be minor or local, and mainly restricted to the practically inhabited Antarctic continent. We show here, as a case study and using climate models, how volcanic ash emitted during a regular eruption of one of the most active volcanoes in Antarctica, Deception Island (South Shetland Islands), could reach the African continent as well as Australia and South America. The volcanic cloud could strongly affect the air traffic not only in the region and at high southern latitudes, but also the flights connecting Africa, South America and Oceania. Results obtained are crucial to understand the patterns of volcanic ash distribution at high southern latitudes with obvious implications for tephrostratigraphical and chronological studies that provide valuable isochrones with which to synchronize palaeoclimate records. This research was partially funded by the MINECO grants VOLCLIMA (CGL2015-72629-EXP)and POSVOLDEC(CTM2016-79617-P)(AEI/FEDER, UE), the Ramón y Cajal research program (RYC-2012-11024) and the NEMOH European project (REA grant 34 agreement n° 289976).

  16. Development of a new generation gravity map of Antarctica: ADGRAV Antarctic Digital Gravity Synthesis

    Directory of Open Access Journals (Sweden)

    R. A. Arko

    1999-06-01

    Full Text Available The U.S. National Science Foundation (NSF has agreed to support the development of a new generation gravity map of Antarctica (ADGRAV - Antarctic Digital Gravity Synthesis, funding the development of a web based access tool. The goal of this project is the creation of an on-line Antarctic gravity database which will facilitate access to improved high resolution satellite gravity models, in conjunction with shipboard, airborne, and land based gravity measurements for the continental regions. This database will complement parallel projects underway to develop new continental bedrock (BEDMAP and magnetic (ADMAP maps of Antarctica.

  17. Development of a new generation gravity map of Antarctica. ADGRAV Antarctic Digital Gravity Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Bell, R.E.; Small, C.; Arko, R.A. [Columbia Univ., Palisades, NY (United States). Lamont-Doherty Earth Observatory

    1999-04-01

    The United States National Science Foundation (NSF) has agreed to support the development of a new generation gravity map of Antarctica (ADGRAW-Antarctic Digital Gravity Synthesis), funding the development of a web based access tool. The goal of this project is the creation of an on-line Antarctic gravity database which will facilitate access to improved high resolution satellite gravity models, in conjunction with shipboard, airborne, and land based gravity measurements for the continental regions. This database will complement parallel projects underway to develop new continental bedrock (BEDMAP) and magnetic (ADMAP) maps of Antarctica.

  18. Genetic evidence of paleolithic colonization and neolithic expansion of modern humans on the tibetan plateau.

    Science.gov (United States)

    Qi, Xuebin; Cui, Chaoying; Peng, Yi; Zhang, Xiaoming; Yang, Zhaohui; Zhong, Hua; Zhang, Hui; Xiang, Kun; Cao, Xiangyu; Wang, Yi; Ouzhuluobu; Basang; Ciwangsangbu; Bianba; Gonggalanzi; Wu, Tianyi; Chen, Hua; Shi, Hong; Su, Bing

    2013-08-01

    Tibetans live on the highest plateau in the world, their current population size is approximately 5 million, and most of them live at an altitude exceeding 3,500 m. Therefore, the Tibetan Plateau is a remarkable area for cultural and biological studies of human population history. However, the chronological profile of the Tibetan Plateau's colonization remains an unsolved question of human prehistory. To reconstruct the prehistoric colonization and demographic history of modern humans on the Tibetan Plateau, we systematically sampled 6,109 Tibetan individuals from 41 geographic populations across the entire region of the Tibetan Plateau and analyzed the phylogeographic patterns of both paternal (n = 2,354) and maternal (n = 6,109) lineages as well as genome-wide single nucleotide polymorphism markers (n = 50) in Tibetan populations. We found that there have been two distinct, major prehistoric migrations of modern humans into the Tibetan Plateau. The first migration was marked by ancient Tibetan genetic signatures dated to approximately 30,000 years ago, indicating that the initial peopling of the Tibetan Plateau by modern humans occurred during the Upper Paleolithic rather than Neolithic. We also found evidences for relatively young (only 7-10 thousand years old) shared Y chromosome and mitochondrial DNA haplotypes between Tibetans and Han Chinese, suggesting a second wave of migration during the early Neolithic. Collectively, the genetic data indicate that Tibetans have been adapted to a high altitude environment since initial colonization of the Tibetan Plateau in the early Upper Paleolithic, before the last glacial maximum, followed by a rapid population expansion that coincided with the establishment of farming and yak pastoralism on the Plateau in the early Neolithic.

  19. Analysis of Mechanism of Tibetan Plateau Vortex Frequency Differences between Strong and Weak MJO Periods

    Science.gov (United States)

    Li, Guoping; Zhao, Fuhu

    2017-04-01

    There are many unique weather systems over the Tibetan Plateau (TP). Among them, the TP vortex (TPV for short) is representative of the low air pressure weather systems. The generation, development and eastward propagation of the TPV is usually accompanied by precipitation, strong winds, thunderstorms and other weather processes, resulting in a series of extreme weather events over the TP and the Sichuan-Chongqing basin where is the downstream of the plateau. Some TPVs, which move from the plateau to the east and develop strongly, even affect a wide range of China's eastern region. NCEP/DOE reanalysis data, OLR data from NOAA, the Australian Meteorological Bureau Real-time Multivariate MJO index, and Tibetan Plateau vortex (TPV) statistical data from the Institute of Plateau Meteorology, are used to discuss the modulation of the TPV by the MJO. Wavelet analysis and composite analysis are the methods used. The results show that: (1) The MJO plays an important role in modulating the TPV, for the number of TPVs generated in strong MJO periods is three times more than in weak periods. (2) During strong (weak) MJO periods, the Tibetan Plateau is in control of a low-frequency, low-pressure cyclone (high-pressure anticyclone) system, and thus the atmospheric circulation conditions over the plateau are conducive (not conducive) to the generation of TPVs. (3) During strong (weak) MJO periods, southerly (northerly) winds prevail in the east of the plateau, but northerly (southerly) winds in the west. Over the northern part of the plateau, easterly (westerly) flow is predominant, while westerly (easterly) flow prevails over the south, thus conducive (not conducive) to the formation of cyclonic circulation (i.e., TPVs) at low altitude over the plateau. (4) In strong MJO periods, water vapor is relatively less abundant over most of the plateau, which is not conducive to the generation of TPVs; however, moisture transported by the south branch trough and the low-frequency, high

  20. Iron biogeochemistry in Antarctic pack ice during SIPEX-2

    Science.gov (United States)

    Lannuzel, Delphine; Chever, Fanny; van der Merwe, Pier C.; Janssens, Julie; Roukaerts, Arnout; Cavagna, Anne-Julie; Townsend, Ashley T.; Bowie, Andrew R.; Meiners, Klaus M.

    2016-09-01

    Our study quantified the spatial and temporal distribution of Fe and ancillary biogeochemical parameters at six stations visited during an interdisciplinary Australian Antarctic marine science voyage (SIPEX-2) within the East Antarctic first-year pack ice zone during September-October 2012. Unlike previous studies in the area, the sea ice Chlorophyll a, Particulate Organic Carbon and Nitrogen (POC and PON) maxima did not occur at the ice/water interface because of the snow loading and dynamic processes under which the sea ice formed. Iron in sea ice ranged from 0.9 to 17.4 nM for the dissolved (0.2 μm) fraction. Our results highlight that the concentration of particulate Fe in sea ice was highest when approaching the continent. The high POC concentration and high particulate iron to aluminium ratio in sea ice samples demonstrate that 71% of the particulate Fe was biogenic in composition. Our estimated Fe flux from melting pack ice to East Antarctic surface waters over a 30 day melting period was 0.2 μmol/m2/d of DFe, 2.7 μmol/m2/d of biogenic PFe and 1.3 μmol/m2/d of lithogenic PFe. These estimates suggest that the fertilization potential of the particulate fraction of Fe may have been previously underestimated due to the assumption that it is primarily lithogenic in composition. Our new measurements and calculated fluxes indicate that a large fraction of the total Fe pool within sea ice may be bioavailable and therefore, effective in promoting primary productivity in the marginal ice zone.

  1. Spatially Extensive Standardized Surveys Reveal Widespread, Multi-Decadal Increase in East Antarctic Adélie Penguin Populations

    National Research Council Canada - National Science Library

    Southwell, Colin; Emmerson, Louise; McKinlay, John; Newbery, Kym; Takahashi, Akinori; Kato, Akiko; Barbraud, Christophe; DeLord, Karine; Weimerskirch, Henri

    2015-01-01

    .... Recent studies of penguin populations, the most commonly abundant Antarctic seabirds in the west Antarctic Peninsula and western Ross Sea, have demonstrated that physical changes in Antarctic marine...

  2. ARM West Antarctic Radiation Experiment (AWARE) Science Plan

    Energy Technology Data Exchange (ETDEWEB)

    Lubin, D [National Science Foundation; Bromwich, DH [Ohio State University; Russell, LM [Scripps Institution of Oceanography; Verlinde, J [The Pennsylvania State University; Vogelmann, AM [Brookhaven National Laboratory

    2015-10-01

    West Antarctica is one of the most rapidly warming regions on Earth, and this warming is closely connected with global sea level rise. The discovery of rapid climate change on the West Antarctic Ice Sheet (WAIS) has challenged previous explanations of Antarctic climate change that focused on strengthening of circumpolar westerlies in response to the positive polarity trend in the Southern Annular Mode. West Antarctic warming does not yet have a comprehensive explanation: dynamical mechanisms may vary from one season to the next, and these mechanisms very likely involve complex teleconnections with subtropical and tropical latitudes. The prime motivation for this proposal is that there has been no substantial atmospheric science or climatological field work on West Antarctica since the 1957 International Geophysical Year and that research continued for only a few years. Direct meteorological information on the WAIS has been limited to a few automatic weather stations for several decades, yet satellite imagery and meteorological reanalyses indicate that West Antarctica is highly susceptible to advection of warm and moist maritime air with related cloud cover, depending on the location and strength of low pressure cells in the Amundsen, Ross, and Bellingshausen Seas. There is a need to quantify the role of these changing air masses on the surface energy balance, including all surface energy components and cloud-radiative forcing. More generally, global climate model simulations are known to perform poorly over the Antarctic and Southern Oceans, and the marked scarcity of cloud information at southern high latitudes has so far inhibited significant progress. Fortunately, McMurdo Station, where the Atmospheric Radiation Measurement Facility’s (ARM’s) most advanced cloud and aerosol instrumentation is situated, has a meteorological relationship with the WAIS via circulation patterns in the Ross and Amundsen Seas. We can therefore gather sophisticated data with cloud

  3. Frequency of human toxocariasis in Jos, Plateau State, Nigeria

    Directory of Open Access Journals (Sweden)

    OO Ajayi

    2000-04-01

    Full Text Available The enzyme-linked immunosorbent assay (Elisa was used to examine sera of 104 children and adults in Jos, Plateau State, Nigeria for anti-toxocaral antibodies, out of which 31 (29.8% were reactive. The seropositive rates were 30.4% for adults, 29.6% for children, 34% for females and 25.9% for males. However, the differences were not significant by age and sex. A highly significant association (p 0.05.

  4. The Quaternary Pan-lake (Overflow) Period and Paleoclimate on the Qinghai-Tibet Plateau

    Institute of Scientific and Technical Information of China (English)

    ZHENG Mianping; YUAN Heran; ZHAO Xitao; LIU Xifang

    2005-01-01

    Lake geomorphology and high-level lacustrine deposits since the mid-late Pleistocene are well preserved in lakes of the Qinghai-Tibet Plateau. According to geological surveys of 17 lake districts in different locations of the plateau,combined with interpretations of satellite images and topographic maps, the authors studied the timing of formation and scopes of the pan-lake areas of the plateau and their paleoclimate. The latest two high lake levels (overflow surfaces) on the Qinghai-Tibet Plateau in the Quaternary occurred at ~40 to 30/35 ka and ~65 to 53 ka respectively. In these time intervals, the plateau was covered by huge interconnected pan-lake systems with a total area of ~36 km2 and a total volume of lake water of >530 million km2, which are about 38 times and 659 times larger than those of the modem lakes respectively. Before this pan-lake period in the late Pleistocene, there had been three high lake levels that occurred at ~132-112 ka, 110-95 ka and 91-72/~83-75 ka respectively, suggesting that the late Quaternary climate on the plateau was unstable and changed rapidly. The ~40-30 ka high lake level also appeared in the Tengger desert north of the plateau,suggesting that there existed very strong summer monsoons from South Asia then; the variation in solar radiation with a 20,000 precessional period has special importance for the high-altitude Qinghai-Tibet Plateau in the low-latitude zone of the Earth. Around 30 ka, the pan-lakes at the peripheries of the Qinghai-Tibet Plateau drained out suddenly with rapid uplift of the plateau and cooling. In a short time the huge amount of cold lake water emptied into the Indian Ocean and Western Pacific. The draining event of the pan-lakes brought about the environmental changes of rivers and lakes at peripheries of the plateau.

  5. Degenerate Rayleigh-Plateau instability in a magnetically annealed colloidal dispersion

    CERN Document Server

    Swan, James W; First, Eric M

    2013-01-01

    This fluid dynamics video depicts the evolution of a suspension of paramagnetic colloids un- der the influence of a uniform, pulsed magnetic field. At low pulse frequencies, the suspension condenses into columns which decompose via a Rayleigh-Plateau instability. At high pulse fre- quencies, the suspension forms a kinetically arrested, system spanning network. We demonstrate the degeneration of the Rayleigh-Plateau instability with increasing pulse frequency.

  6. Modeling and Mapping Soil Moisture of Plateau Pasture Using RADARSAT-2 Imagery

    OpenAIRE

    Xun Chai; Tingting Zhang; Yun Shao; Huaze Gong; Long Liu; Kaixin Xie

    2015-01-01

    Accurate soil moisture retrieval of a large area in high resolution is significant for plateau pasture. The object of this paper is to investigate the estimation of volumetric soil moisture in vegetated areas of plateau pasture using fully polarimetric C-band RADARSAT-2 SAR (Synthetic Aperture Radar) images. Based on the water cloud model, Chen model, and Dubois model, we proposed two developed algorithms for soil moisture retrieval and validated their performance using experimental data. We ...

  7. 陇东旱塬区玉米高产集成技术与示范%Research and Demonstration of Integrated High Yield Corn Cultivation Technology on the Loess Plateau Region of East Gansu

    Institute of Scientific and Technical Information of China (English)

    史聚宝

    2012-01-01

    陇东旱塬区玉米(Zea mays L.)高产集成技术是以全膜覆盖、双垄沟播技术为核心,集成组装测土配方施肥+良种应用+适期早播、宽窄行密植+病虫害监测防控等技术,推出“全膜覆盖玉米(留膜免耕)-冬油菜(留膜免耕)-大豆(高塬夏菜)”两年三熟制种植模式.该技术在甘肃省泾川县经5年推广试验示范,玉米平均增产3 247.5 kg/hm2,增加产值7 306.9元/hm2,较对照(常规种植)增加生产成本1 357.5元/hm2,新增总产值19 641.5万元,新增总纯收益15 941.7万元,产投比5.3∶1,科技投资收益率431%,推广投资收益率4 460%,取得了极显著的社会效益和经济效益.%The core of integrated high yield corn (Zea mays L.) cultivation technology on the Loess plateau region of east Gansu was double ridges with whole plastic film cover. By integrating fertilization according to soil testing, elite seed application, suitable early sowing, reasonable planting dense and pest monitor-control technology, the "mulching corn (film remaining and no-tillage)-winter rape (film remaining and no-tillage)-soybean (high tableland summer vegetable)" with three mature in two years planting model was put forward. Through experiment and demonstration plant for 5 years in Jingchuan of Gansu, the average yield of corn was increased by 3 247.5 kg/hm2, with the output value increasing by 7 306.9 Yuan/hm2 compared with control. The cost of production was increased by 1 357.5 Yuan/hm2; while the total output value was increased by 19 641.5 million yuan, thus the total net income was increased by 15 941.7 million Yuan with the output to input ratio 5.3:1. The return of science and technology investment was 431%; of promotion investment was 4 460%, with remarkable social and economic benefits.

  8. Air-surface exchange of gaseous mercury over permafrost soil: an investigation at a high-altitude (4700 m a.s.l.) and remote site in the central Qinghai-Tibet Plateau

    Science.gov (United States)

    Ci, Zhijia; Peng, Fei; Xue, Xian; Zhang, Xiaoshan

    2016-11-01

    The pattern of air-surface gaseous mercury (mainly Hg(0)) exchange in the Qinghai-Tibet Plateau (QTP) may be unique because this region is characterized by low temperature, great temperature variation, intensive solar radiation, and pronounced freeze-thaw process of permafrost soils. However, the air-surface Hg(0) flux in the QTP is poorly investigated. In this study, we performed field measurements and controlled field experiments with dynamic flux chambers technique to examine the flux, temporal variation and influencing factors of air-surface Hg(0) exchange at a high-altitude (4700 m a.s.l.) and remote site in the central QTP. The results of field measurements showed that surface soils were the net emission source of Hg(0) in the entire study (2.86 ng m-2 h-1 or 25.05 µg m-2 yr-1). Hg(0) flux showed remarkable seasonality with net high emission in the warm campaigns (June 2014: 4.95 ng m-2 h-1; September 2014: 5.16 ng m-2 h-1; and May-June 2015: 1.95 ng m-2 h-1) and net low deposition in the winter campaign (December 2014: -0.62 ng m-2 h-1) and also showed a diurnal pattern with emission in the daytime and deposition in nighttime, especially on days without precipitation. Rainfall events on the dry soils induced a large and immediate increase in Hg(0) emission. Snowfall events did not induce the pulse of Hg(0) emission, but snowmelt resulted in the immediate increase in Hg(0) emission. Daily Hg(0) fluxes on rainy or snowy days were higher than those of days without precipitation. Controlled field experiments suggested that water addition to dry soils significantly increased Hg(0) emission both on short (minutes) and relatively long (hours) timescales, and they also showed that UV radiation was primarily attributed to Hg(0) emission in the daytime. Our findings imply that a warm climate and environmental change could facilitate Hg release from the permafrost terrestrial ecosystem in the QTP.

  9. 青海高海拔藏区老年结核性脑膜炎临床特点分析%Clinical Characteristics of Elderly Tuberculous Meningitis in the High-altitude Area on the Qinghai-Tibet Plateau

    Institute of Scientific and Technical Information of China (English)

    张润

    2013-01-01

    - altitude area on the Qinghai -Tibet Plateau. Methods Twenty - eight patients of elderly tuberculous meningitis from the high - altitude area on the Qinghai - Tibet Plateau who were treated in our hospital between January 2006 and December 2010 were included in the study group, and 30 adolescent and young patients with tuberculous meningitis who were treated in our hospital during the same period were randomly selected as the control group. The disease onset, major clinical symptoms and signs, laboratory results ( cerebrospinal fluid routine examination, biochemical test, purified protein derivative intradermal test, Brain CT and/or MRI examination ), treatment, and prognosis were compared between the two groups. Results The number of cases of subacute or chronic disease onset was 22 and 20 in the study group and the control group, respectively. The study group had lower incidence of fever than the control group ( P 0. 05 ). The proportion of cases with CSF pressure > 200 mm H2O ( 1 mm H2O =0. 0098 kPa ) was lower in the study group than in the control group ( P 0. 05 ). The study group included 12 cases of intracephalic malacia, 8 cases of cerebral infarction, 5 cases of ischemic change, 3 cases of brain tuberculoma, among which 18 cases were combined with severe/moderate hydrocephalus. The control group included 14 cases of intracranial hematogenous miliary tubercle, 10 cases of multiple intracephalic ring enhanced lesions, 6 cases of brain tuberculoma, among which 4 cases were combined with severe/moderate hydrocephalus. The incidence rate of hydrocephalus, malnutrition, diabetes, and drug hepatitis was higher in the study group than in the control group ( P < 0. 05 ). The 4HRZE ( S ) IV6HRZ/12HR was routinely used as the main therapy, and glucoeorticoid, dehydration, and liver protection were used as adjuvant therapies. High intracra-nial pressure and hydroeephalus were given caution and treated in a timely manner. In the study group, 11 cases improved and 17 cases

  10. Identifying the AD 1257 Salamas volcanic event from micron-size tephra composition in two East Antarctic ice cores

    Science.gov (United States)

    Petit, Jean Robert; Narcisi, Biancamaria; Batanova, Valentina G.; Joël, Savarino; Komorowski, Jean Christophe; Michel, Agnes; Metrich, Nicole; Besson, Pascale; Vidal, Celine; Sobolev, Alexander V.

    2016-04-01

    A wealth of valuable data about the history of explosive volcanic history can be extracted from polar ice successions. Both the volatile by-products and the solid silicate (tephra) components of volcanic plumes can be incorporated into snow layers, providing tools for chronostratigraphic correlations and for interpretation of climate-volcanism interactions. Volcanic events from low-latitude regions are of particular interest as the related sulphate aerosol travelling through the stratosphere can reach the polar sheets forming inter-hemispheric (Greenland and Antarctica) signals preserved in the ice. Within the glaciological record of globally significant volcanic markers, the AD1259 signal represents one of most prominent events over the last thousands years. Its source has been long debated. On the basis of recent field investigations (Lavigne et al., 2013; Vidal et al., 2015), it has been proposed that Mount Samalas on Lombok Island (Indonesia) represents the source responsible for the polar event. With the goal of bringing distal tephrochronological evidence to source identification, we have attempted to identify volcanic ash associated to the AD 1259 sulphate pulse. To this purpose we used firn and ice-core samples from two East Antarctic Plateau sites: Concordia-Dome C (75°06' S, 123°20' E, 3233 m) and Talos Dome (72°49'S, 159°11'E, 2315 m). Our high-resolution studies included sample processing in a Class 100 clean room using established ultra-clean procedures for insoluble microparticle analyses, Coulter counter grain size measurements, scanning electron microscope observations and the geochemical (major elements) composition from the recently set ISTERRE Jeol JXA 8230 Superprobe and calibrated for small particles analysis. Despite the difficulty of studying such minute fragments, within both cores we located and characterised multiple tiny (micron-size) glass shards concomitant with the volcanic peak. We present preliminary results alongside comparison

  11. Argalis on the Qinghai-Tibet Plateau

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The argali are listed by the State as animals subject tosecond-class protection,and no killing is allowed. The international communitylists argali on the Qinghai-Tibet Plateau as animals that must not be hunted.

  12. Colorado Plateau Rapid Ecoregion Assessment Data Catalog

    Data.gov (United States)

    Bureau of Land Management, Department of the Interior — Datasets used in the analysis of the Colorado Plateau (COP) Rapid Ecoregion Assessment (REA).They can be downloaded via a layer package (lpk, similar to a zip file...

  13. Antarctic Data Management as Part of the IPY Legacy

    Science.gov (United States)

    de Bruin, T.

    2006-12-01

    The Antarctic Treaty states that "scientific observations and results from Antarctica shall be exchanged and made freely available". Antarctica includes the Southern Ocean. In support of this, National Antarctic Data Centres (NADC) are being established to catalogue data sets and to provide information on data sets to scientists and others with interest in Antarctic science. The Joint Committee on Antarctic Data Management (JCADM) was established by the Scientific Committee on Antarctic Research (SCAR) and the Council of Managers of National Antarctic Programs (COMNAP). JCADM comprises representatives of the National Antarctic Data Centres. Currently 30 nations around the world are represented in JCADM. JCADM is responsible for the Antarctic Master Directory (AMD), the internationally accessible, web-based, searchable record of Antarctic and Southern Ocean data set descriptions. The AMD is directly integrated into the international Global Change Master Directory (GCMD) to help further merge Antarctic science into global science. The AMD is a resource for scientists to advertise the data they have collected and to search for data they may need. JCADM is the Antarctic component of the IPY Data Infrastructure, which is presently being developed. This presentation will give an overview of the organization of Antarctic and Southern Ocean data management with sections on the organizational structure of JCADM, contents of the Antarctic Master Directory, relationships to the SCAR Scientific Research Programmes (SRP) and IPY, international embedding and connections with discipline-based peer organizations like the International Oceanographic Data and Information Exchange Committee (IODE). It will focus primarily on the role that an existing infrastructure as JCADM, may play in the development of the IPY Data Infrastructure and will provide considerations for IPY data management, based on the experiences in Antarctic and oceanographic data management.

  14. Pyramid Schemes on the Tibetan Plateau

    OpenAIRE

    Devin Gonier; Rgyal yum sgrol ma

    2012-01-01

    The unique features of pyramid schemes and certain underlying causes for their development on the Tibetan Plateau are analyzed. Research was conducted by analyzing 521 surveys, allowing estimation of pyramid scheme activity on the Plateau and an identification of related cultural and social specificities. Firsthand accounts were collected revealing details of personal involvement. Survey data and similarities in the accounts were studied to suggest how involvement in pyramid schemes might be ...

  15. Factors that affect the nearshore aggregations of Antarctic krill in a biological hotspot

    Science.gov (United States)

    Bernard, Kim S.; Cimino, Megan; Fraser, William; Kohut, Josh; Oliver, Matthew J.; Patterson-Fraser, Donna; Schofield, Oscar M. E.; Statscewich, Hank; Steinberg, Deborah K.; Winsor, Peter

    2017-08-01

    Antarctic krill, Euphausia superba, is a highly abundant and ecologically important zooplankton species in the Southern Ocean. Regions of elevated Antarctic krill biomass exist around Antarctica, often as a result of the concentrating effect of bathymetry and ocean currents. Such areas are considered biological hotspots and are key foraging grounds for numerous top predators in the region. A hotspot of Antarctic krill biomass exists off the southern extent of Anvers Island, Western Antarctic Peninsula, and supports a population of Adélie penguins that feed almost exclusively on it, as well as numerous other top predators. We investigated the spatio-temporal variability in Antarctic krill biomass and aggregation structure over four consecutive summer seasons, identifying environmental factors that were responsible. We identified three distinct krill aggregation types (Large-dense, Small-close and Small-sparse), and found that the relative proportion of each type to total aggregation numbers varied significantly between survey days. Large-dense aggregations occurred more frequently when westerly winds predominated and when the local mixed tide was in the diurnal regime. Small-close aggregations were also more frequent during diurnal tides and were negatively correlated with phytoplankton biomass. Small-sparse aggregations, on the other hand, were more prevalent when the mixed tide was in the semi-diurnal phase. We suggest that, under certain conditions (i.e. diurnal tides and westerly winds), the biological hotspot in the nearshore waters off Palmer Station, Anvers Island, functions as a zone of accumulation, concentrating krill biomass. Our findings provide important information on the dynamics of Antarctic krill at the local scale.

  16. Regional Changes in the Sea Ice Cover and Ice Production in the Antarctic

    Science.gov (United States)

    Comiso, Josefino C.

    2011-01-01

    Coastal polynyas around the Antarctic continent have been regarded as sea ice factories because of high ice production rates in these regions. The observation of a positive trend in the extent of Antarctic sea ice during the satellite era has been intriguing in light of the observed rapid decline of the ice extent in the Arctic. The results of analysis of the time series of passive microwave data indicate large regional variability with the trends being strongly positive in the Ross Sea, strongly negative in the Bellingshausen/Amundsen Seas and close to zero in the other regions. The atmospheric circulation in the Antarctic is controlled mainly by the Southern Annular Mode (SAM) and the marginal ice zone around the continent shows an alternating pattern of advance and retreat suggesting the presence of a propagating wave (called Antarctic Circumpolar Wave) around the circumpolar region. The results of analysis of the passive microwave data suggest that the positive trend in the Antarctic sea ice cover could be caused primarily by enhanced ice production in the Ross Sea that may be associated with more persistent and larger coastal polynyas in the region. Over the Ross Sea shelf, analysis of sea ice drift data from 1992 to 2008 yields a positive rate-of-increase in the net ice export of about 30,000 km2 per year. For a characteristic ice thickness of 0.6 m, this yields a volume transport of about 20 km3/year, which is almost identical, within error bars, to our estimate of the trend in ice production. In addition to the possibility of changes in SAM, modeling studies have also indicated that the ozone hole may have a role in that it causes the deepening of the lows in the western Antarctic region thereby causing strong winds to occur offthe Ross-ice shelf.

  17. Oxygen Isotope Mass-Balance Constraints on Pliocene Sea Level and East Antarctic Ice Sheet Stability

    Science.gov (United States)

    Winnick, M. J.; Caves, J. K.

    2015-12-01

    The mid-Pliocene Warm Period (MPWP, 3.3-2.9 Ma), with reconstructed atmospheric pCO2 of 350-450 ppm, represents a potential analogue for climate change in the near future. Current highly cited estimates place MPWP maximum global mean sea level (GMSL) at 21 ± 10 m above modern, requiring total loss of the Greenland (GIS) and marine West Antarctic Ice Sheets (WAIS) and a substantial loss of the East Antarctic Ice Sheet (EAIS), with only a concurrent 2-3 ºC rise in global temperature. Many estimates of Pliocene GMSL are based on the partitioning of oxygen isotope records from benthic foraminifera (δ18Ob) into changes in deep-sea temperatures and terrestrial ice sheets. These isotopic budgets are underpinned by the assumption that the δ18O of Antarctic ice (δ18Oi) was the same in the Pliocene as it is today, and while the sensitivity of δ18Ob to changing meltwater δ18O has been previously considered, these analyses neglect conservation of 18O/16O in the ocean-ice system. Using well-calibrated δ18O-temperature relationships for Antarctic precipitation along with estimates of Pliocene Antarctic surface temperatures, we argue that the δ18Oi of the Pliocene Antarctic ice sheet was at minimum 1‰-4‰ higher than present. Assuming conservation of 18O/16O in the ocean-ice system, this requires lower Pliocene seawater δ18O (δ18Osw) without a corresponding change in ice sheet mass. This effect alone accounts for 5%-20% of the δ18Ob difference between the MPWP interglacials and the modern. With this amended isotope budget, we suggest that Pliocene GMSL was likely 9-13.5 m and very likely 5-17 m above modern, which suggests the EAIS is less sensitive to radiative forcing than previously inferred from the geologic record.

  18. Antarctic Pliocene Biotic and Environmental Change in a Global Context Changes

    Science.gov (United States)

    Quilty, P. G.; Whitehead, J.

    2005-12-01

    The Pliocene was globally an interval of dramatic climate change and often compared with the environment evolving through human-induced global change. Antarctic history needs to be integrated into global patterns. The Prydz Bay-Prince Charles Mountains region of East Antarctica is a major source of data on Late Paleozoic-Recent changes in Antarctic biota and environment. This paper reviews what is known of 13 marine transgressions in the Late Neogene of the region and attempts to compare the Antarctic pattern with global patterns, such as those identified through global sequence stratigraphic analysis. Although temporal resolution in Antarctic sections is not always as good as for sections elsewhere, enough data exist to indicate that many events can be construed as part of global changes. It is expected that further correlation will be effected. During much of the Pliocene, there was less continental ice, reduced sea-ice cover, probably higher sea-level, penetration of marine conditions deep into the hinterland, and independent evidence to indicate that this was due to warmth. The Antarctic Polar Frontal Zone probably was much farther south than currently. There have been major changes in the marine fauna, and distribution of surviving species since the mid-Pliocene. Antarctic fish faunas underwent major changes during this interval with evolution of a major new Subfamily and diversification in at least two subfamilies. No palynological evidence of terrestrial vegetation has been recovered from the Prydz Bay - Prince Charles Mountain region. Analysis of origin and extinction data for two global planktonic foraminiferal biostratigraphic zonations shows that the interval Late Miocene-Pliocene was an interval of enhanced extinction and evolution, consistent with an interval of more rapid and high amplitude fluctuating environments.

  19. East Antarctic rifting triggers uplift of the Gamburtsev Mountains.

    Science.gov (United States)

    Ferraccioli, Fausto; Finn, Carol A; Jordan, Tom A; Bell, Robin E; Anderson, Lester M; Damaske, Detlef

    2011-11-16

    The Gamburtsev Subglacial Mountains are the least understood tectonic feature on Earth, because they are completely hidden beneath the East Antarctic Ice Sheet. Their high elevation and youthful Alpine topography, combined with their location on the East Antarctic craton, creates a paradox that has puzzled researchers since the mountains were discovered in 1958. The preservation of Alpine topography in the Gamburtsevs may reflect extremely low long-term erosion rates beneath the ice sheet, but the mountains' origin remains problematic. Here we present the first comprehensive view of the crustal architecture and uplift mechanisms for the Gamburtsevs, derived from radar, gravity and magnetic data. The geophysical data define a 2,500-km-long rift system in East Antarctica surrounding the Gamburtsevs, and a thick crustal root beneath the range. We propose that the root formed during the Proterozoic assembly of interior East Antarctica (possibly about 1 Gyr ago), was preserved as in some old orogens and was rejuvenated during much later Permian (roughly 250 Myr ago) and Cretaceous (roughly 100 Myr ago) rifting. Much like East Africa, the interior of East Antarctica is a mosaic of Precambrian provinces affected by rifting processes. Our models show that the combination of rift-flank uplift, root buoyancy and the isostatic response to fluvial and glacial erosion explains the high elevation and relief of the Gamburtsevs. The evolution of the Gamburtsevs demonstrates that rifting and preserved orogenic roots can produce broad regions of high topography in continental interiors without significantly modifying the underlying Precambrian lithosphere.

  20. Contrasts between Antarctic and Arctic ozone depletion.

    Science.gov (United States)

    Solomon, Susan; Portmann, Robert W; Thompson, David W J

    2007-01-09

    This work surveys the depth and character of ozone depletion in the Antarctic and Arctic using available long balloon-borne and ground-based records that cover multiple decades from ground-based sites. Such data reveal changes in the range of ozone values including the extremes observed as polar air passes over the stations. Antarctic ozone observations reveal widespread and massive local depletion in the heart of the ozone "hole" region near 18 km, frequently exceeding 90%. Although some ozone losses are apparent in the Arctic during particular years, the depth of the ozone losses in the Arctic are considerably smaller, and their occurrence is far less frequent. Many Antarctic total integrated column ozone observations in spring since approximately the 1980s show values considerably below those ever observed in earlier decades. For the Arctic, there is evidence of some spring season depletion of total ozone at particular stations, but the changes are much less pronounced compared with the range of past data. Thus, the observations demonstrate that the widespread and deep ozone depletion that characterizes the Antarctic ozone hole is a unique feature on the planet.

  1. Global dynamics of the Antarctic ice sheet

    NARCIS (Netherlands)

    Oerlemans, J.

    2002-01-01

    The total mass budget of the Antarctic ice sheet is studied with a simple axi-symmetrical model. The ice-sheet has a parabolic profile resting on a bed that slopes linearly downwards from the centre of the ice sheet into the ocean. The mean ice velocity at the grounding line is assumed to be proport

  2. An Eocene-Miocene continuous high resolution rock magnetic record from the sediments in the Xining Basin, NW China: indication for Cenozoic persistent drying driven by global cooling and Tibetan Plateau uplift

    Science.gov (United States)

    Zan, J.; Fang, X.; Appel, E.; Yan, M.; Song, C.

    2013-12-01

    Tibetan Plateau uplift and global cooling have generally been thought to have caused the drying of the Asian inland. But how and when these factors drove the aridification is unknown. The Xining Basin at the NE Tibetan Plateau received continuous Eocene-Miocene fine-grained sediments, providing an excellent opportunity to assess this question. We carried out firstly detailed rock magnetic measurements and diffuse reflectance spectroscopy (DRS) analyses for a well-dated Cenozoic sedimentary record from the Xiejia section in the basin. Magnetic susceptibility (χ) in this section shows a long-term decreasing trend from ~52 Ma to ~25 Ma, well coinciding with global cooling and drying in the region, and an increasing trend since ~25 Ma, which is in contrast to the further progressing aridification of the basin. Thermomagnetic results and DRS-determined hematite contents suggest that the relative content of magnetite and hematite is the main control on the χ values. We argue that the long-term Eocene-Oligocene global cooling increased the drying of the Asian inland, lowering the lake level and exposing a larger area to low temperature oxidation for longer times, thus producing more hematite and leading to the decreasing trend of χ from ~52 Ma to ~25 Ma. An intensive uplift of the NE Tibetan Plateau since ~25 Ma, associated with a change in the sedimentary source, might be responsible for the increase of χ after 25 Ma.

  3. Personality Testing in Antarctic Expeditioners: Cross Cultural Comparisons and Evidence for Generalizability

    Science.gov (United States)

    Musson, D. M.; Sandal, G. M.; Harper, M. L.; Helmreich, R. L.

    scores on any of the nine separate traits assessed by the PCI for which clear comparisons could be made - these included: Instrumentality, Expressivity, Negative Instrumentality, Verbal Aggressiveness, Negative Communion, Mastery, Work Orientation and Competitiveness. For the two scales for which comparisons were less reliable, Impatience &Irritability as well as Achievement Striving, some differences between national groups were suggested. Testing response patterns showed some national variation in that the Australian subjects answered the Likert-style survey questions by choosing more extreme values when compared to Norwegian and British participants. In comparison to the U.S. student population, Antarctic personnel from all three nations scored lower on Negative Instrumentality, Verbal Aggressiveness, and Competitiveness. Greater variability between all 4 groups was seen with the traits of Impatience &Irritability and Achievement strivings, but again, comparisons on these two dimensions were less reliable due to differences in the testing battery. CONCLUSIONS These results suggest that there is a high degree of similarity among Antarctic personnel from the three nations included in these analyses. They also support generalizing psychological research findings between different national programs of Antarctic research. Differences suggested in ratings of Impatience and Irritability as well as Achievement Striving warrant attention in future studies. In comparison with a normative US student population, significant differences were found on a number of measures. It is not clear at this time whether these differences are due to cultural differences or due to the existence of a characteristic Antarctic expeditioner personality profile. Recommendations for future research include the need to standardize psychological instruments used in different programs of space analogue research and the inclusion of methodologies to address confounds inherent in cross cultural research

  4. Variability in solar irradiance observed at two contrasting Antarctic sites

    Science.gov (United States)

    Petkov, Boyan H.; Láska, Kamil; Vitale, Vito; Lanconelli, Christian; Lupi, Angelo; Mazzola, Mauro; Budíková, Marie

    2016-05-01

    The features of erythemally weighted (EW) and short-wave downwelling (SWD) solar irradiances, observed during the spring-summer months of 2007-2011 at Johann Gregor Mendel (63°48‧S, 57°53‧W, 7 m a.s.l.) and Dome Concordia (75°06‧S, 123°21‧E, 3233 m a.s.l.) stations, placed at the Antarctic coastal region and on the interior plateau respectively, have been analysed and compared to each other. The EW and SWD spectral components have been presented by the corresponding daily integrated values and were examined taking into account the different geographic positions and different environmental conditions at both sites. The results indicate that at Mendel station the surface solar irradiance is strongly affected by the changes in the cloud cover, aerosols and albedo that cause a decrease in EW between 20% and 35%, and from 0% to 50% in SWD component, which contributions are slightly lower than the seasonal SWD variations evaluated to be about 71%. On the contrary, the changes in the cloud cover features at Concordia station produce only a 5% reduction of the solar irradiance, whilst the seasonal oscillations of 94% turn out to be the predominant mode. The present analysis leads to the conclusion that the variations in the ozone column cause an average decrease of about 46% in EW irradiance with respect to the value found in the case of minimum ozone content at each of the stations. In addition, the ratio between EW and SWD spectral components can be used to achieve a realistic assessment of the radiation amplification factor that quantifies the relationship between the atmospheric ozone and the surface UV irradiance.

  5. The active southwest margin of the Colorado Plateau: uplift of mantle origin

    Science.gov (United States)

    Parsons, T.; McCarthy, J.

    1995-01-01

    During Cenozoic time, the Colorado Plateau was raised about 2km above sea level. The most-recent and best-documented uplift of the plateau (~1km) has been concentrated at its southwest margin between 6 and 1 Ma, whereas the eastern Colorado Plateau may have been at high elevations since Eocene time. To better understand the recent tectonic activity at the southwest margin of the Colorado Plateau, we compile detailed crustal thickness and density information from seismic and gravity data for a region that includes northwest Arizona and the southern tip of Nevada. This information is used to isolate the mantle contribution to uplift. We speculate that uplift may result from subduction-related thinning of the continental lithosphere. -from Authors

  6. A numerical modelling study on the processes of uplift and planation of the Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    董文杰; 汤懋苍

    1997-01-01

    The Tibetan Plateau has experienced a number of processes of uplift and planation alternately since about 45 Ma B. P. when it began to raise. A differential equation model for describing the Plateau altitude variation with time is formulated on the basis of previous field studies and a theoretical hypothesis: if palaeomagnetic polarity is positive, the convective activity in the earth is strong; orogenic movement is violent; and the raising velocity of the Plateau is high and vice versa . The analytical solution of the equation is obtained. The altitude variation from the beginning of the Plateau uplift to present is computed through using the geomagnetic polarity reversals timing series and interstellar atomic hydrogen concentration data. A comparison between the model results and the field studies indicates that the former is quite similar to the latter. The model results are able to basically reproduce the alternating processes of uplift and planation of the plate geological history. In the present m

  7. Differences between 1999 and 2010 across the Falkland Plateau: fronts and water masses

    Science.gov (United States)

    Pérez-Hernández, M. Dolores; Hernández-Guerra, Alonso; Comas-Rodríguez, Isis; Benítez-Barrios, Verónica M.; Fraile-Nuez, Eugenio; Pelegrí, Josep L.; Naveira Garabato, Alberto C.

    2017-07-01

    Decadal differences in the Falkland Plateau are studied from the two full-depth hydrographic data collected during the ALBATROSS (April 1999) and MOC-Austral (February 2010) cruises. Differences in the upper 100 dbar are due to changes in the seasonal thermocline, as the ALBATROSS cruise took place in the austral fall and the MOC-Austral cruise in summer. The intermediate water masses seem to be very sensitive to the wind conditions existing in their formation area, showing cooling and freshening for the decade as a consequence of a higher Antarctic Intermediate Water (AAIW) contribution and of a decrease in the Subantarctic Mode Water (SAMW) stratum. The deeper layers do not exhibit any significant change in the water mass properties. The Subantarctic Front (SAF) in 1999 is observed at 52.2-54.8° W with a relative mass transport of 32.6 Sv. In contrast, the SAF gets wider in 2010, stretching from 51.1 to 57.2° W (the Falkland Islands), and weakening to 17.9 Sv. Changes in the SAF can be linked with the westerly winds and mainly affect the northward flow of Subantarctic Surface Water (SASW), SAMW and AAIW/Antarctic Surface Water (AASW). The Polar Front (PF) carries 24.9 Sv in 1999 (49.8-44.4° W), while in 2010 (49.9-49.2° W) it narrows and strengthens to 37.3 Sv.

  8. DECADAL VARIABILITY OF THE ANTARCTIC OSCILLATION

    Institute of Scientific and Technical Information of China (English)

    龚道溢; 王绍武

    2001-01-01

    This paper summarizes the long-term and decadal time-scale fluctuations of atmospheric circulation in the Southern (Hemisphere) middle and high latitudes. The long time series of Antarctic Oscillation Indices (AOIs) were established for January, April, July and October based on the historical sea level pressure maps and NCEP/NCAR reanalysis surface pressure data set. It was found that the AOI of January had upward trend at a rate of 1.17 hPa/100 a, and July had downward trend at a rate of -1.49 hPa/100 a since 1871. The method of wavelet analysis was applied to detect the low frequency characteristics of AOIs, and it is clear that there are decadal variations in the time scale of about 20-30 years in all 4 indices. Since the averaged value of 4 months could explain most variance of annual AOI thus it is reasonable using the mean AOI of January, April, July and October to represent the annual AOI. The value of annual AOI was much lower in periods of about 1894-1901. 1910-1935, and was much higher in periods of about 1880 -1893, 1936-1945. The positive anomalies were remarkable since 1980s. Power spectra of modeled AOIs from Hadley Center Control Integration (HCCI) were compared with the observations, it is found that the interannual time scale frequencies were more significant than decadal frequencies. But, there also had the possibility for generating weak decadal fluctuations in some special months and years by Hasselmann mechanism.

  9. Microbiology and Geochemistry of Antarctic Paleosols

    Science.gov (United States)

    Mahaney, W. C.; Malloch, D.; Hancock, R. G. V.; Campbell, I. B.; Sheppard, D.

    2000-08-01

    Samples of ancient soils from horizons in paleosols from the Quartermain Mountains (Aztec and New Mountain areas of the Antarctic Dry Valleys) were analyzed for their chemical composition and microbiology to determine the accumulation and movement of salts and other soluble constituents. The salt concentrations are of special interest because they are considered to be a function of age, derived in part from nearby oceanic and high altitude atmospheric sources. The geochemistry of ancient Miocene-age paleosols in these areas is the direct result of the deposition and weathering of till, derived principally from dolerite and sandstone source rock, in association with airborne-influxed salts. Paleosols nearer the coast have greater contents of chlorine, and farther inland near the Inland Ice Sheet, nitrogen tends to increase on a relative basis. The accumulation and vertical distribution of salts and other soluble chemical elements indicate relative amounts of movement in the profile over long periods of time, to the order of several million years. Iron, both in total concentration and in the form of various extracts, indicates it can be used as a geochronometer to assess the buildup of goethite plus hematite over time in the paleosols. Trends for ferrihydrite, a partially soluble Fe-hydroxide, shows limited profile translocation that might be related to the movement of salt. Six of the eight selected subsamples from paleosol horizons in three soil profiles contained nil concentrations of bacteria and fungi. However, two horizons at depths of between three to eight centimeters yielded several colonies of the fungi Beauveria bassiana and Penicillium spp., indicating some input of organic carbon. Beauveria bassiana is often reported in association with insects and is used commercially for the biological control of some insect pests. Penicillium species are commonly isolated from Arctic, temperate and tropical soils and are known to utilize a wide variety of organic

  10. Stability of alpine meadow ecosystem on the Qinghai- Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    ZHOU Huakun; ZHOU Li; ZHAO Xinquan; LIU Wei; LI Yingnian; GU Song; ZHOU Xinmin

    2006-01-01

    The meadow ecosystem on the Qinghai-Tibetan Plateau is considered to be sensitive to climate change. An understanding of the alpine meadow ecosystem is therefore important for predicting the response of ecosystems to climate change. In this study, we use the coefficients of variation (Cv) and stability (E) obtained from the Haibei Alpine Meadow Ecosystem Research Station to characterize the ecosystem stability. The results suggest that the net primary production of the alpine meadow ecosystem was more stable (Cv = 13.18%) than annual precipitation (Cv = 16.55%) and annual mean air temperature (Cv = 28.82%). The net primary production was insensitive to either the precipitation (E = 0.0782) or air temperature (E = 0.1113). In summary, the alpine meadow ecosystem on the Qinghai- Tibetan Plateau is much stable. Comparison of alpine meadow ecosystem stability with other five natural grassland ecosystems in Israel and southern African indicates that the alpine meadow ecosystem on the Qinghai-Tibetan Plateau is the most stable ecosystem. The alpine meadow ecosystem with relatively simple structure has high stability, which indicates that community stability is not only correlated with biodiversity and community complicity but also with environmental stability. An average oscillation cycles of 3―4 years existed in annual precipitation, annual mean air temperature, net primary production and the population size of consumers at the Haibei natural ecosystem. The high stability of the alpine meadow ecosystem may be resulting also from the adaptation of the ecosystem to the alpine environment.

  11. Dendroclimatic reconstructions for the southern Colorado plateau

    Energy Technology Data Exchange (ETDEWEB)

    Dean, J.S.; Funkhouser, G.S. [Univ. of Arizona, Tucson, AZ (United States)

    1995-09-01

    A geographical network of climate sensitive tree-ring chronologies consisting of 25 archaeological sequences and two bristlecone pine series provides the basis for high resolution reconstructions of low and high frequency climatic variability on the southern Colorado Plateau over the last 1,500 years. Qualitative and quantitative dendroclimatic analyses of these data produce annual retrodictions of yearly and seasonal precipitation and summer Palmer Drought Severity Indices for each station and reconstructions of regional scale patterns in climatic variability. These reconstructions provide detailed information on climatic fluctuations that affected biotic and human populations as well as long-term baseline data for evaluating present-day climate and estimating future climatic trends. When integrated with other measures of past environmental variability, these reconstructions specify periods of favorable and unfavorable environmental conditions that would have affected past human populations of the region. The severest degradation, which occurred between A.D. 1250 and 1450, probably was causally related to numerous cultural changes that occurred at the end of the l3th century including the Anasazi abandonment of the Four Comers area. Projecting environmental patterns that characterized the last two millennia into the future indicates potential hazards to long term uranium mill waste disposal and containment and the potential and limitations of environmental restoration.

  12. Pliocene retreat of Greenland and Antarctic Ice Sheet margins (Invited)

    Science.gov (United States)

    Deconto, R. M.; Pollard, D.

    2013-12-01

    The middle Pliocene epoch (~3 million years ago) is often considered an analogue for future global climatic conditions, because global mean temperatures were comparable to projections of future climate at the end of this century. Importantly, some estimates of mid-Pliocene sea level are >20 m higher than today, implying the potential for significant retreat of the East Antarctic Ice Sheet (EAIS), in addition to the loss of the Greenland and West Antarctic Ice Sheets (WAIS). Here, we use a hybrid ice sheet-shelf model with freely migrating grounding lines coupled to a high-resolution regional climate model to test the potential for both West and East Antarctic Ice Sheet retreat during the warm Pliocene and in long-term future scenarios with elevated CO2. In these simulations we apply new treatments of i) ice shelf calving (accounting for the effects of divergent ice flow and surface melt water on crevassing), ii) ice-cliff mechanics at the grounding line, iii) improved sub-glacial bathymetry using BEDMAP2, and iv) a range of plausible ocean warming scenarios based on offline ocean modeling. In warm Pliocene simulations, the combination of improved bathymetric detail and more physically based model treatments of floating and grounded calving fronts substantially increases the rates and magnitudes of ice sheet retreat into over-deepened subglacial basins in both in West and East Antarctica. These new results imply the EAIS margin did indeed contribute to elevated (and orbitally paced) Pliocene sea levels, with Antarctica contributing up to ~20m equivalent sea level during the warmest intervals. In long-term (10^3-4-yr) future simulations using the same model physics, we find these new mechanisms produce a much more sensitive and vulnerable ice sheet than previously considered, with the potential for substantial future retreat of both WAIS and parts of the East Antarctic margin in response to the combined effects of increased surface melt on ice shelf surfaces and

  13. Program of the Antarctic Syowa MST/IS radar (PANSY)

    Science.gov (United States)

    Sato, Kaoru; Tsutsumi, Masaki; Sato, Toru; Nakamura, Takuji; Saito, Akinori; Tomikawa, Yoshihiro; Nishimura, Koji; Kohma, Masashi; Yamagishi, Hisao; Yamanouchi, Takashi

    2014-10-01

    The PANSY radar is the first Mesosphere-Stratosphere-Troposphere/Incoherent Scatter (MST/IS) radar in the Antarctic region. It is a large VHF monostatic pulse Doppler radar operating at 47 MHz, consisting of an active phased array of 1045 Yagi antennas and an equivalent number of transmit-receive (TR) modules with a total peak output power of 500 kW. The first stage of the radar was installed at Syowa Station (69°00‧S, 39°35‧E) in early 2011, and is currently operating with 228 antennas and modules. This paper reports the project's scientific objectives, technical descriptions, and the preliminary results of observations made to date. The radar is designed to clarify the role of atmospheric gravity waves at high latitudes in the momentum budget of the global circulation in the troposphere, stratosphere and mesosphere, and to explore the dynamical aspects of unique polar phenomena such as polar mesospheric clouds (PMC) and polar stratospheric clouds (PSC). The katabatic winds as a branch of Antarctic tropospheric circulation and as an important source of gravity waves are also of special interest. Moreover, strong and sporadic energy inputs from the magnetosphere by energetic particles and field-aligned currents can be quantitatively assessed by the broad height coverage of the radar which extends from the lower troposphere to the upper ionosphere. From engineering points of view, the radar had to overcome restrictions related to the severe environments of Antarctic research, such as very strong winds, limited power availability, short construction periods, and limited manpower availability. We resolved these problems through the adoption of specially designed class-E amplifiers, light weight and tough antenna elements, and versatile antenna arrangements. Although the radar is currently operating with only about a quarter of its full designed system components, we have already obtained interesting results on the Antarctic troposphere, stratosphere and

  14. Towards Resolving the Paradox of Antarctic Sea Ice: A New Integrated Framework for Observing the Antarctic Marginal Ice Zone

    Science.gov (United States)

    Williams, G. D.

    2014-12-01

    Antarctic sea ice distribution, a canary in the coal mine for climate change in the Southern Hemisphere, is controlled by the marginal ice zone (MIZ). The MIZ is the dynamic outer part of the sea-ice zone, where it interacts with the high-energy open ocean and is strongly affected by waves and storms. As an interface between ocean and atmosphere with extreme vertical and horizontal temperature gradients and large variations in mechanical properties, the MIZ is a complex system that evolves with, and impacts upon, the advancing/receding ice edge. More than a zone, it is a migratory transition in 'phase space' that biannually passes across the entire Antarctic SIZ. During the advance phase of sea-ice seasonality, and under freezing conditions, wave-induced pancake-ice formation can lead to rapid ice-edge advance. During the retreat phase, the dynamic break-up and modification of sea ice by passing storms, winds and waves greatly modifies the floe-size distribution within the MIZ, to create smaller floes that melt more rapidly and accelerate sea-ice retreat as spring progresses. Inspired by the current Arctic MIZ efforts, new fieldwork is proposed to resolve the key characteristics of the Antarctic MIZ and the processes controlling its extent. Combining new autonomous observation technology with ship-based techniques, integrated experiments are being designed to advance our understanding of the MIZ and its role in driving seasonal sea ice advance and retreat around Antarctica. The proposed project provides a unique opportunity to develop an observational, analytical, and science-policy framework for coordinated monitoring of sea ice in both the northern and southern hemispheres, with implications for forecasting, monitoring, and prediction that are essential with increasingly dynamic and variable polar climate systems.

  15. Imported anthropogenic bacteria may survive the Antarctic winter and introduce new genes into local bacterial communities

    Directory of Open Access Journals (Sweden)

    Brat Kristian

    2016-03-01

    Full Text Available We studied dynamic changes in anthropogenic bacterial communities at a summer-operated Czech research base (the Mendel Research Station in the Antarctic during 2012 and 2013. We observed an increase in total numbers of detected bacteria between the beginning and the end of each stay in the Antarctic. In the first series of samples, bacteria of Bacillus sp. predominated. Surprisingly, high numbers of Gram-positive cocci and coliforms were found (including opportunistic human pathogens, although the conditions for bacterial life were unfavourable (Antarctic winter. In the second series of samples, coliforms and Gram-positive cocci predominated. Dangerous human pathogens were also detected. Yersinia enterocolitica was identified as serotype O:9. Antibiotic susceptibility testing showed medium-to-high resistance rates to ampicillin, cefalotin, cefuroxime, amoxicillin-clavulanate and gentamicin in Enterobacteriaceae. 16S rRNA sequencing showed high rates of accordance between nucleotide sequences among the tested strains. Three conclusions were drawn: (1 Number of anthropogenic bacteria were able to survive the harsh conditions of the Antarctic winter (inside and outside the polar station. Under certain circumstances (e.g. impaired immunity, the surviving bacteria might pose a health risk to the participants of future expeditions or to other visitors to the base. (2 The bacteria released into the outer environment might have impacts on local ecosystems. (3 New characteristics (e.g. resistance to antibiotics may be introduced into local bacterial communities.

  16. Antarctic and Southern Ocean influences on Late Pliocene global cooling.

    Science.gov (United States)

    McKay, Robert; Naish, Tim; Carter, Lionel; Riesselman, Christina; Dunbar, Robert; Sjunneskog, Charlotte; Winter, Diane; Sangiorgi, Francesca; Warren, Courtney; Pagani, Mark; Schouten, Stefan; Willmott, Veronica; Levy, Richard; DeConto, Robert; Powell, Ross D

    2012-04-24

    The influence of Antarctica and the Southern Ocean on Late Pliocene global climate reconstructions has remained ambiguous due to a lack of well-dated Antarctic-proximal, paleoenvironmental records. Here we present ice sheet, sea-surface temperature, and sea ice reconstructions from the ANDRILL AND-1B sediment core recovered from beneath the Ross Ice Shelf. We provide evidence for a major expansion of an ice sheet in the Ross Sea that began at ∼3.3 Ma, followed by a coastal sea surface temperature cooling of ∼2.5 °C, a stepwise expansion of sea ice, and polynya-style deep mixing in the Ross Sea between 3.3 and 2.5 Ma. The intensification of Antarctic cooling resulted in strengthened westerly winds and invigorated ocean circulation. The associated northward migration of Southern Ocean fronts has been linked with reduced Atlantic Meridional Overturning Circulation by restricting surface water connectivity between the ocean basins, with implications for heat transport to the high latitudes of the North Atlantic. While our results do not exclude low-latitude mechanisms as drivers for Pliocene cooling, they indicate an additional role played by southern high-latitude cooling during development of the bipolar world.

  17. Relationships between high altitude de-adaptation syndrome and training burnout of plateau soldiers after returning to the plain%高原驻训士兵返回平原后高原脱适应症与训练倦怠的关系研究

    Institute of Scientific and Technical Information of China (English)

    丁魁; 李权超; 王燕; 孟新珍; 秦天

    2016-01-01

    目的:探讨高原驻训士兵返回平原后高原脱适应症发生率及与训练倦怠之间的关系。方法抽取驻疆某部高原驻训返回平原1周后140名士兵作为调查对象,采用自编士兵训练倦怠问卷方式进行测评,分有、无高原脱适应症状两组,比较两组训练倦怠间的差异性,同时分析高原脱适应症与训练倦怠的相关性。结果①高原驻训士兵返回平原后脱适应症发生率为80.00%,与高原维稳部队返回平原后脱适应症状发生率78.36%(χ2=0.188,P=0.664)、高原移居者返回平原后脱适应症发生率75.10%(χ2=1.279, P=0.258)均无显著性差异。疲倦(12.86%)、头晕(11.43%)、乏力(10.00%)位居高原脱适应症状前3位。②有高原脱适应症状士兵训练倦怠总分及身心耗竭、训练疏离得分显著高于无高原脱适应症状士兵( P<0.01)。体质量超重士兵高原脱适应症发生率显著高于体质量正常士兵(P<0.05)。③进入高原驻训士兵返回平原后,高原脱适应症与训练倦怠的回归方程(P<0.01)为:训练倦怠=0.498×高原脱适应症-0.126×年龄+0.038×军龄+0.069×文化程度+0.029×体质指数。结论高原驻训士兵返回平原后高原脱适应症与训练倦怠存在一定程度的关联性,减少高原脱适应症的发生,有助于降低训练倦怠程度。%Objective To explore the relationship between high altitude de-adaptation syndrome and training burnout of plateau-garrisoned soldiers after returning to the plain.Methods A total of 140 plateau-garrisoned soldiers who had returned to the plain were chosen by random cluster sampling and measured with the Training Burnout Test.They were divided into two groups according to the occurrence of acute mountain sickness.We compared the differences in training burnout between the two groups and analyzed the

  18. Several characteristics of contemporary climate change in the Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    朱文琴; 陈隆勋; 周自江

    2001-01-01

    Characteristics of contemporary climate change in the Tibetan Plateau have been investigated based on the observational data of monthly mean air temperature, monthly mean maximum and minimum air temperatures, and precipitation amount at 217 stations in the Plateau and its adjacent areas in 1951-1998, in which the temperature data at Lhasa, Lanzhou, Kunming and Chengdu were extended to a period of 1935-1950. The following conclusions can be drawn. (1) The air temperature in the Tibetan Plateau decreased from the 1950s to the 1960s, afterwards it began warming up to the 1990s. The data at the Lhasa Station beginning from 1935 have indicated that the air temperature at the station was the highest in the 1940s, then it became cooling until the 1960s. After the 1960s, it began warming until the 1990s. However, the air temperature at Lhasa in the 1990s still did not reach as high as in the 1940s. (2) Since the 1960s, there has existed a cooling belt below 3000 m altitude above sea level, which is located in ea

  19. Soil Erosion Study on the Chinese Loess Plateau

    Science.gov (United States)

    Hu, Yaxian; Guo, Shengli; Kuhn, Nikolaus

    2017-04-01

    The Chinese Loess Plateau, because of its highly erodible loess soils and hilly topography, has been extensively studied by soil scientists and geomorphologists. As a research hotspot, there are five national-level field stations across the Loess Plateau, with hundreds of erosion plots set up with various sizes, lengths, slope angles and vegetation covers. In addition, huge indoor rain simulation facilities exist in in different institutes which can provide rainfall simulations under a wide range of controlled conditions. Consequently, national-level restoration projects have achieved tremendous improvements in curbing soil erosion and improving regional agro-ecosystem, mostly by afforestation and soil rehabilitation. However, when implementing the advanced techniques and models that have been widely applied in the rest of the world, there are often regional considerations, which demand new approaches to overcome. One example are the unintentional impacts of restoration efforts, such as the establishment of apple orchards. Over 20 years, they have caused an increase in soil erodibility and lowered local ground water levels. Neither before the introduction of this landscape rehabilitation technique, nor now, has the impact of intensive fruit production been systematically studied, despite lending itself to systematic experiments. The lack of research is attributed to the general idea that trees protect soils and improve environmental services. This presentation identifies several such specific regional environmental issues associated with soil erosion on the Loess Plateau and discusses strategies to avoid missing important research questions.

  20. Cost of protein synthesis and energy allocation during development of antarctic sea urchin embryos and larvae.

    Science.gov (United States)

    Pace, Douglas A; Manahan, Donal T

    2007-04-01

    Cold environments represent a substantial volume of the biosphere. To study developmental physiology in subzero seawater temperatures typically found in the Southern Ocean, rates and costs of protein synthesis were measured in embryos and larvae of Sterechinus neumayeri, the Antarctic sea urchin. Our analysis of the "cost of living" in extreme cold for this species shows (1) that cost of protein synthesis is strikingly low during development, at 0.41 +/- 0.05 J (mg protein synthesized)(-1) (n = 16); (2) that synthesis cost is fixed and independent of synthesis rate; and (3) that a low synthesis cost permits high rates of protein turnover at -1 degrees C, at rates comparable to those of temperate species of sea urchin embryos developing at 15 degrees C. With a low synthesis cost, even at the highest synthesis rates measured (gastrulae), the proportion of total metabolism accounted for by protein synthesis in the Antarctic sea urchin was 54%-a value similar to that of temperate sea urchin embryos. In the Antarctic sea urchin, up to 87% of metabolic rate can be accounted for by the combined energy costs of protein synthesis and the sodium pump. We conclude that, in Antarctic sea urchin embryos, high rates of protein synthesis can be supported in extreme-cold environments while still maintaining low rates of respiration.

  1. Ciliate biogeography in Antarctic and Arctic freshwater ecosystems: endemism or global distribution of species?

    Science.gov (United States)

    Petz, Wolfgang; Valbonesi, Alessandro; Schiftner, Uwe; Quesada, Antonio; Cynan Ellis-Evans, J

    2007-02-01

    Ciliate diversity was investigated in situ in freshwater ecosystems of the maritime (South Shetland Islands, mainly Livingston Island, 63 degrees S) and continental Antarctic (Victoria Land, 75 degrees S), and the High Arctic (Svalbard, 79 degrees N). In total, 334 species from 117 genera were identified in both polar regions, i.e. 210 spp. (98 genera) in the Arctic, 120 spp. (73 genera) in the maritime and 59 spp. (41 genera) in the continental Antarctic. Forty-four species (13% of all species) were common to both Arctic and Antarctic freshwater bodies and 19 spp. to both Antarctic areas (12% of all species). Many taxa are cosmopolitans but some, e.g. Stentor and Metopus spp., are not, and over 20% of the taxa found in any one of the three areas are new to science. Cluster analysis revealed that species similarity between different biotopes (soil, moss) within a study area was higher than between similar biotopes in different regions. Distinct differences in the species composition of freshwater and terrestrial communities indicate that most limnetic ciliates are not ubiquitously distributed. These observations and the low congruence in species composition between both polar areas, within Antarctica and between high- and temperate-latitude water bodies, respectively, suggest that long-distance dispersal of limnetic ciliates is restricted and that some species have a limited geographical distribution.

  2. The Response of Snow on Tibetan Plateau in Winter to Indian Ocean Sea Surface Temperature Anomaly

    Science.gov (United States)

    Jia, Lha; Xiao, Tiangui; Wang, Chao; Du, Jun; Zhou, Xiaoli

    2017-04-01

    By using the daily snow depth and snow cover days data at 100 meteorological stations in Tibetan Plateau during 1979-2013, the methods of EOF, REOF and SVD were used to analyze the distribution characteristic and time series variation of snow in Tibetan Plateau. The coupling relationship between snow in Tibetan Plateau in winter and Indian Ocean sea surface temperature in winter, and the lag response of the snow in Tibetan Plateau in winter to Indian Ocean sea surface temperature were also studied. Main conclusions are as follows: 1.Snow depth and snow cover reaches the maximum value in January and reaches the minimum value in July; accumulated snow depth and snow cover days shows an increasing tendency during 1980s to 1990s and has a decreasing tendency since then. The accumulated snow depth and snow cover days decrease in summer and increase in autumn. 2. There were 4 high-frequency centers of snow cover days and accumulated snow depth: the southern Himalayas area, the area between the Tanggula Mountains and the Nyainqentanglha Mountains, the area around Bayankela Mountains and the area around Qilian Mountains. 3. The first pattern of SVD between snow in Tibetan Plateau in winter and Indian Ocean sea surface temperature in winter has the feature that Indian Ocean sea surface temperature increase in the whole area and snow has an opposite trend in the western and southeastern Plateau and the northern and southern Plateau. The second pattern shows that Indian Ocean sea surface temperature has an opposite trend in the western ocean and the eastern ocean and snow has an opposite trend in the western Plateau and the southeastern Plateau. There is a significant negative correlation between Indian Ocean sea surface temperature in June and July and snow in Tibetan Plateau in winter. Key words: Tibetan Plateau; snow; Indian Ocean; SVD Acknowledgements This study was supported by National Natural Science Foundation of China Fund Project (91337215, 41575066),National Key

  3. Triple plating of tibia in a complex bicondylar tibial plateau fracture

    Institute of Scientific and Technical Information of China (English)

    Atin Jaiswal; Naiman Deepak Kachchhap; Yashwant S Tanwar; Birendra Kumar; Sachin K Yadav

    2014-01-01

    High-energy tibial plateau fracture poses a significant challenge and difficulty for orthopaedic surgeons.Fracture of tibial plateau involves major weight bearing joint and may alter knee kinematics.Anatomic reconstruction of the proximal tibial articular surfaces,restoration of the limb axis (limb alignment) and stable fixation permitting early joint motion are the goals of the treatment.In cases of complex bicondylar tibial plateau fractures,isolated lateral plating is frequently associated with varus malalignment and better results have been obtained with bilateral plating through dual incisions.However sometimes a complex type of bicondylar tibial plateau fractures is encountered in which medial plateau has a biplaner fracture in posterior coronal plane as well as sagittal plane.In such fractures it is imperative to fix the medial plateau with buttressing in both planes.One such fracture pattern of the proximal tibia managed by triple plating through dual posteromedial and anterolateral incisions is discussed in this case report with emphasis on mechanisms of this type of injury,surgical approach and management.

  4. Gait characteristics and quality of life perception of patients following tibial plateau fracture.

    Science.gov (United States)

    Warschawski, Yaniv; Elbaz, Avi; Segal, Ganit; Norman, Doron; Haim, Amir; Jacov, Elis; Grundshtein, Alon; Steinberg, Ely

    2015-11-01

    The purpose of the current study was to evaluate the long-term functional outcome as measured by gait patterns and quality of life assessment of patients with high-energy tibial plateau fracture compared to matched controls. Thirty-eight patients were evaluated in a case-controlled comparison. Twenty-two patients with tibial plateau fracture were evaluated after 3.1 (1.63) years (sd) from injury. Patients underwent a computerized spatiotemporal gait test and completed the SF-12 health survey. 16 healthy subjects, matched for age and gender served as a control group. The main outcome measures for this study were spatiotemporal gait characteristics, physical quality of life and mental quality of life. Significant differences were found in all gait parameters between patients with tibial plateau fracture and healthy controls. Patients with tibial plateau fracture walked slower by 18% compared to the control group (p life exist in patients following tibial plateau fracture. Patients following tibial plateau fracture present altered spatiotemporal gait patterns compared to healthy controls, as well as self-reported quality of life.

  5. Ice core precipitation record in central Tibetan plateau since AD 1600

    Directory of Open Access Journals (Sweden)

    T. Yao

    2008-02-01

    Full Text Available Lack of reliable long-term precipitation record from northern Tibetan Plateau has constrained the understanding of precipitation variation in this region. An ice core drilled from the Puruogangri Ice Field on central Tibetan Plateau in the year 2000 helped reveal the precipitation variations since AD 1600. Analysis of the annual accumulation data presented precipitation changes from AD 1600, indicative of wet and dry periods in the past 400 year in the central Tibetan Plateau. Accordingly, the 18th and 20th centuries experienced high precipitation period, whilst the 19th century experienced low precipitation period. Such a feature was consistent with precipitation recorded in ice cores from Dunde and Guliya Glaciers, northern Tibetan Plateau. Besides, the results also pointed to consistency in precipitation-temperature correlation on the northern Tibetan Plateau, in a way that temperature and precipitation were positively correlated. But this feature was contrary to the relationship revealed from Dasuopu ice cores, southern Tibetan Plateau, where temperature and precipitation were negatively correlated. The north-south contrast in precipitation amount and its relationship with temperature may shed light on the reconstruction of Asian monsoon since AD 1600.

  6. Imprint of a dissolved cobalt basaltic source on the Kerguelen Plateau

    Directory of Open Access Journals (Sweden)

    J. Bown

    2012-06-01

    Full Text Available Processes of cobalt (Co entrainment from shelf sediments over the Kerguelen Plateau were studied during the KEOPS (Kerguelen Ocean Plateau compared Study in order to explain the exceptionally high dissolved cobalt concentrations that have been measured in the surface waters above the Kerguelen Plateau, and in intermediate and deep waters above its eastern slope. Lateral advection and dissolution of Co contained in basalt sediments around Heard Island, a main source of lithogenic Co in the study area, were shown to imprint the process of surface enrichment over the plateau. Dissolved Co enrichment was strongest at the intercept of the eastern slope with intermediate and deep waters, probably due to more efficient mobilisation of the sediments in the slope current, in addition to advection of Co-enriched and low oxygenated ocean water-masses.

    In surface waters, strong sedimentary Co inputs were estimated to be much higher than biological Co uptake in phytoplankton blooms, underlining the potential role of cobalt as lithogenic tracer. Based on a simple, steady state balance equation of the external input of dissolved iron over the plateau, the fertilization of iron inferred by using Co as a tracer of basalt sources is estimated to be 28 × 102 ± 21 × 102 ton yr−1 in surface waters of the Kerguelen Plateau. This estimate is consistent with preceding ones and the required iron supply matching the phytoplankton demand.

  7. Magnetostratigraphy of Late Cenozoic fossil mammals in the northeastern margin of the Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A number of fossil mammals have been found in the very thick Cenozoic stratigraphy of the Guide Basin in the northeastern margin of the Tibetan Plateau. Some of these are of great significance in mammal evolution and stratigraphic correlation on and around the Tibetan Plateau and North China. However, the chronology of these mammals is poorly constrained. Dating of the mammals will not only place precise age constraints on the mammals, but also provide much information on the related stratigraphy that records the uplift process of the Tibetan Plateau. Detailed paleomagnetism of the upper part of the Cenozoic stratigraphy at He'erjia and Lajigai north of Guide County has revealed magnetic chrons that can be correlated to Gauss and 3An chrons, determining the section spanning about 3.1-6.5 Ma and the first, second and third layers of fossil mammals at about 5.25, 5.1 and 4.4 Ma, respectively. Ages of the significant genus Gazella kueitensis and the Chinese elephant Anancus sinensis are firstly constrained at about 5.25 MaBP and 4.4 Ma, respectively. The mammalian evolution and the associated increase in coarse sediments and sedimentation rate may suggest that the northeastern Tibetan Plateau was uplifted rapidly at that time, and the eastern Tibetan Plateau with its neighboring regions was not high enough to stop mammal exchange between the northern and southern sides of the Tibetan Plateau.

  8. Psychrotrophic metal tolerant bacteria for mobilisation of metals in Antarctic waters

    Digital Repository Service at National Institute of Oceanography (India)

    Gonsalves, M.J.B.D.

    Cold tolerant psychrotrophic bacteria abound in the Antarctic waters. While Antarctic krills are known to concentrate heavy metals at ppm levels, psychrotrophic bacteria from Antarctic fresh and marine waters have been reported to tolerate them...

  9. Reversible Photoinhibition in Antarctic Moss during Freezing and Thawing.

    Science.gov (United States)

    Lovelock, C. E.; Jackson, A. E.; Melick, D. R.; Seppelt, R. D.

    1995-01-01

    Tolerance of antarctic moss to freezing and thawing stress was investigated using chlorophyll a fluorescence. Freezing in darkness caused reductions in Fv/Fm (ratio of variable to maximum fluorescence) and Fo (initial fluorescence) that were reversible upon thawing. Reductions in Fv/Fm and Fo during freezing in darkness indicate a reduction in the potential efficiency of photosystem II that may be due to conformational changes in pigment-protein complexes due to desiccation associated with freezing. The absorption of light during freezing further reduced Fv/Fm and Fo but was also reversible. Using dithiothreitol (DTT), which inhibits the formation of the carotenoid zeaxanthin, we found reduced flurorescence quenching during freezing and reduced concentrations of zeaxanthin and antheraxanthin after freezing in DTT-treated moss. Reduced concentrations of zeaxanthin and antheraxanthin in DTT-treated moss were partially associated with reductions in nonphotochemical fluorescence quenching. The reversible photoinhibition observed in antarctic moss during freezing indicates the existence of processes that protect from photoinhibitory damage in environments where freezing temperatures occur in conjunction with high solar radiation levels. These processes may limit the need for repair cycles that require temperatures favorable for enzyme activity. PMID:12228644

  10. A Palaeohydrological Shift during Neogene East Antarctic Ice Sheet Retreat

    Science.gov (United States)

    Rees-Owen, R. L.; Newton, R.; Ivanovic, R. F.; Francis, J.; Tindall, J. C.; Riding, J. B.

    2015-12-01

    The East Antarctic Ice Sheet is an important driver of global climate, playing a particular role in governing albedo and atmospheric circulation (eg. Singh et al., 2013). Recent evidence from marine sediment and terrestrial glaciovolcanic sequences suggests that the EAIS underwent periodic retreat and collapse in response to warmer climates during the late Neogene (14 to 3 million years ago). Mummified prostrate trees recovered from palaeosols at Oliver Bluffs in the Beardmore Glacier region, Transantarctic Mountains (85° S), represent a rare insight into the terrestrial palaeoclimate during one of these periods of retreat. Prostrate trees are an understudied but useful tool for interrogating endmember (e.g. periglacial) environments at high altitudes and latitudes. We present exciting new palaeoclimate data from the sequence at Oliver Bluffs. δ18O analysis of tree ring cellulose suggests that Antarctic summer palaeoprecipitation was enriched relative to today (-25 to -5‰ for ancient, -35 to -20‰ for modern); consistent with our isotope-enabled general circulation model simulations. The MBT/CBT palaeothermometer gives a summer temperature of 3-6ºC, consistent with other palaeobotanical climate indices. These geological and model data have wide-ranging implications for our understanding of the hydrological cycle during this time period. We present data suggesting that changes in moisture recycling and source region indicate a markedly different hydrological cycle.

  11. Characteristics of land-atmosphere energy and turbulentfluxes over the plateau steppe in central Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2016-01-01

    The land-atmosphere energy and turbulence exchange is key to understanding land surface processes on the TibetanPlateau (TP). Using observed data for Aug. 4 to Dec. 3, 2012 from the Bujiao observation point (BJ) of the Nagqu PlateauClimate and Environment Station (NPCE-BJ), different characteristics of the energy flux during the Asian summermonsoon (ASM) season and post-monsoon period were analyzed. This study outlines the impact of the ASM on energyfluxes in the central TP. It also demonstrates that the surface energy closure rate during the ASM season is higher than thatof the post-monsoon period. Footprint modeling shows the distribution of data quality assessments (QA) and qualitycontrols (QC) surrounding the observation point. The measured turbulent flux data at the NPCE-BJ site were highly representativeof the target land-use type. The target surface contributed more to the fluxes under unstable conditions thanunder stable conditions. The main wind directions (180° and 210°) with the highest data density showed flux contributionsreaching 100%, even under stable conditions. The lowest flux contributions were found in sectors with low data density,e.g., 90.4% in the 360° sector under stable conditions during the ASM season. Lastly, a surface energy water balance(SEWAB) model was used to gap-fill any absent or corrected turbulence data. The potential simulation error was alsoexplored in this study. The Nash-Sutcliffe model efficiency coefficients (NSEs) of the observed fluxes with the SEWABmodel runs were 0.78 for sensible heat flux and 0.63 for latent heat flux during the ASM season, but unrealistic values of?0.9 for latent heat flux during the post-monsoon period.

  12. Encouraging Advances Made by Chinese Scientists in Antarctic Research

    Institute of Scientific and Technical Information of China (English)

    Zhang Qingsong

    2003-01-01

    @@ Chinese scientists began involving in the Antarctic research in 1980. As the first step, some 40 Chinese scientists were sent to Antarctic stations of Australia and other countries during the period from 1980 to 1984. Then,China established two Antarctic stations of its own, and purchased an icebreaker, enabling China to carry on its own independent research program both on land and at sea.

  13. Early Human Occupation on the Northeast Tibetan Plateau

    Science.gov (United States)

    Rhode, D.; Madsen, D.; Brantingham, P.; Perrault, C.

    2010-12-01

    The Tibetan Plateau presents great challenges for human occupation: low oxygen, high ultraviolet radiation, harsh seasonal climate, low overall biological productivity. How and when early humans were able to cope physiologically, genetically, and behaviorally with these extremes is important for understanding the history of human adaptive flexibility. Our investigations of prehistoric human settlement on the northeast Tibetan Plateau focus on (a) establishing well-dated evidence for occupation of altitudes >3000 m, (b) the environmental context of high altitude adaptation, and (c) relations of hunting and pastoralism to lower-altitude agrarian systems. We observe two major prehistoric settlement patterns in the Qinghai Lake area. The earliest, ~15,000-7500 yr old, consists of small isolated firehearths with sparse associated stone tools and wild mammal remains (1). Numerous hearths often occur in the same localities, indicating repeated short-duration occupations by small hunting parties. A second pattern, ~9000-4000 yr old, was established during the Holocene climatic optimum. These sites represent prolonged seasonal residential occupation, containing dark anthropogenic midden, hearth and pit constructions, abundant stone tools, occasional ceramics, and abundant diverse faunal remains (including medium-large mammals but lacking domestic sheep/yak)(2). These Plateau-margin base camps allowed greater intensity of use of the high Plateau. Residential occupation was strongly influenced by nearby lower-altitude farming communities; development of the socioeconomic landscape along the Yellow River likely played at least as great a role in Plateau occupation patterns as did Holocene environmental changes. Holocene vegetation changes in the NE Tibetan Plateau have been attributed to climate (3) or anthropogenic modification (4). Our results document changes in shrub/tree presence from ~12,000-4000 BP, similar to pollen records, that likely reflect climate rather than

  14. Laboratory study of nitrate photolysis in Antarctic snow. II. Isotopic effects and wavelength dependence.

    Science.gov (United States)

    Berhanu, Tesfaye A; Meusinger, Carl; Erbland, Joseph; Jost, Rémy; Bhattacharya, S K; Johnson, Matthew S; Savarino, Joël

    2014-06-28

    Atmospheric nitrate is preserved in Antarctic snow firn and ice. However, at low snow accumulation sites, post-depositional processes induced by sunlight obscure its interpretation. The goal of these studies (see also Paper I by Meusinger et al. ["Laboratory study of nitrate photolysis in Antarctic snow. I. Observed quantum yield, domain of photolysis, and secondary chemistry," J. Chem. Phys. 140, 244305 (2014)]) is to characterize nitrate photochemistry and improve the interpretation of the nitrate ice core record. Naturally occurring stable isotopes in nitrate ((15)N, (17)O, and (18)O) provide additional information concerning post-depositional processes. Here, we present results from studies of the wavelength-dependent isotope effects from photolysis of nitrate in a matrix of natural snow. Snow from Dome C, Antarctica was irradiated in selected wavelength regions using a Xe UV lamp and filters. The irradiated snow was sampled and analyzed for nitrate concentration and isotopic composition (δ(15)N, δ(18)O, and Δ(17)O). From these measurements an average photolytic isotopic fractionation of (15)ɛ = (-15 ± 1.2)‰ was found for broadband Xe lamp photolysis. These results are due in part to excitation of the intense absorption band of nitrate around 200 nm in addition to the weaker band centered at 305 nm followed by photodissociation. An experiment with a filter blocking wavelengths shorter than 320 nm, approximating the actinic flux spectrum at Dome C, yielded a photolytic isotopic fractionation of (15)ɛ = (-47.9 ± 6.8)‰, in good agreement with fractionations determined by previous studies for the East Antarctic Plateau which range from -40 to -74.3‰. We describe a new semi-empirical zero point energy shift model used to derive the absorption cross sections of (14)NO3 (-) and (15)NO3 (-) in snow at a chosen temperature. The nitrogen isotopic fractionations obtained by applying this model under the experimental temperature as well as considering the

  15. Laboratory study of nitrate photolysis in Antarctic snow. II. Isotopic effects and wavelength dependence

    Science.gov (United States)

    Berhanu, Tesfaye A.; Meusinger, Carl; Erbland, Joseph; Jost, Rémy; Bhattacharya, S. K.; Johnson, Matthew S.; Savarino, Joël

    2014-06-01

    Atmospheric nitrate is preserved in Antarctic snow firn and ice. However, at low snow accumulation sites, post-depositional processes induced by sunlight obscure its interpretation. The goal of these studies (see also Paper I by Meusinger et al. ["Laboratory study of nitrate photolysis in Antarctic snow. I. Observed quantum yield, domain of photolysis, and secondary chemistry," J. Chem. Phys. 140, 244305 (2014)]) is to characterize nitrate photochemistry and improve the interpretation of the nitrate ice core record. Naturally occurring stable isotopes in nitrate (15N, 17O, and 18O) provide additional information concerning post-depositional processes. Here, we present results from studies of the wavelength-dependent isotope effects from photolysis of nitrate in a matrix of natural snow. Snow from Dome C, Antarctica was irradiated in selected wavelength regions using a Xe UV lamp and filters. The irradiated snow was sampled and analyzed for nitrate concentration and isotopic composition (δ15N, δ18O, and Δ17O). From these measurements an average photolytic isotopic fractionation of 15ɛ = (-15 ± 1.2)‰ was found for broadband Xe lamp photolysis. These results are due in part to excitation of the intense absorption band of nitrate around 200 nm in addition to the weaker band centered at 305 nm followed by photodissociation. An experiment with a filter blocking wavelengths shorter than 320 nm, approximating the actinic flux spectrum at Dome C, yielded a photolytic isotopic fractionation of 15ɛ = (-47.9 ± 6.8)‰, in good agreement with fractionations determined by previous studies for the East Antarctic Plateau which range from -40 to -74.3‰. We describe a new semi-empirical zero point energy shift model used to derive the absorption cross sections of 14NO3- and 15NO3- in snow at a chosen temperature. The nitrogen isotopic fractionations obtained by applying this model under the experimental temperature as well as considering the shift in width and center well

  16. Laboratory study of nitrate photolysis in Antarctic snow. II. Isotopic effects and wavelength dependence

    Energy Technology Data Exchange (ETDEWEB)

    Berhanu, Tesfaye A.; Erbland, Joseph; Savarino, Joël [Laboratoire de Glaciologie et Géophysique de l’Environnement, CNRS, F-38041 Grenoble (France); Univ. Grenoble Alpes, LGGE, F-38041 Grenoble (France); Meusinger, Carl; Johnson, Matthew S. [Copenhagen Center for Atmospheric Research (CCAR), Department of Chemistry, University of Copenhagen, Copenhagen (Denmark); Jost, Rémy [Laboratoire de Interdisciplinaire de Physique (LIPHY) Univ. de Grenoble, Grenoble (France); Bhattacharya, S. K. [Research Center for Environmental Changes, Academia Sinica, Nangang, Taipei 115, Taiwan (China)

    2014-06-28

    Atmospheric nitrate is preserved in Antarctic snow firn and ice. However, at low snow accumulation sites, post-depositional processes induced by sunlight obscure its interpretation. The goal of these studies (see also Paper I by Meusinger et al. [“Laboratory study of nitrate photolysis in Antarctic snow. I. Observed quantum yield, domain of photolysis, and secondary chemistry,” J. Chem. Phys. 140, 244305 (2014)]) is to characterize nitrate photochemistry and improve the interpretation of the nitrate ice core record. Naturally occurring stable isotopes in nitrate ({sup 15}N, {sup 17}O, and {sup 18}O) provide additional information concerning post-depositional processes. Here, we present results from studies of the wavelength-dependent isotope effects from photolysis of nitrate in a matrix of natural snow. Snow from Dome C, Antarctica was irradiated in selected wavelength regions using a Xe UV lamp and filters. The irradiated snow was sampled and analyzed for nitrate concentration and isotopic composition (δ{sup 15}N, δ{sup 18}O, and Δ{sup 17}O). From these measurements an average photolytic isotopic fractionation of {sup 15}ε = (−15 ± 1.2)‰ was found for broadband Xe lamp photolysis. These results are due in part to excitation of the intense absorption band of nitrate around 200 nm in addition to the weaker band centered at 305 nm followed by photodissociation. An experiment with a filter blocking wavelengths shorter than 320 nm, approximating the actinic flux spectrum at Dome C, yielded a photolytic isotopic fractionation of {sup 15}ε = (−47.9 ± 6.8)‰, in good agreement with fractionations determined by previous studies for the East Antarctic Plateau which range from −40 to −74.3‰. We describe a new semi-empirical zero point energy shift model used to derive the absorption cross sections of {sup 14}NO{sub 3}{sup −} and {sup 15}NO{sub 3}{sup −} in snow at a chosen temperature. The nitrogen isotopic fractionations obtained by applying

  17. Miocene climate as recorded on slope carbonates : examples from Malta (Central Mediterranean) and Northeastern Australia (Marion Plateau, ODP LEG 194)

    Science.gov (United States)

    John, Cédric Michaël

    2003-08-01

    carbonate content and organic matter geochemical analysis furthermore suggest that the clay-rich intervals are similar to sapropelic deposits. On the Marion Plateau, trends in oxygen and carbon isotopes were obtained by measuring Cibicidoides spp foraminifers. Moreover, carbonate content was reconstructed using a chemical method (coulometer). Results show that the mid Miocene cooling step profoundly affected this system: a major drop in accumulation rates of carbonates occurs precisely at 13.8 Ma, around the time of the East Antarctic ice sheet formation. Moreover, sedimentation changes occurred at that time, carbonate fragments coming from neritic environments becoming less abundant, planktonic foraminifer content increasing and quartz and reworked glauconite being deposited. Conversely, a surprising result is that the major N12-N14 sea-level fall occurring around 11.5 Ma did not impact the accumulation of carbonates on the slope. This was unexpected since carbonate platform are very sensitive to sea-level changes. The model developed to explain that mass accumulation rates of carbonates diminished around 13.6 Ma (Mi3 Event) instead of 11.5 Ma (N12-N14 event), suggests that oceanic currents were controlling slope carbonate deposition on the Marion Plateau prior to the mid-Miocene, and that the mid Miocene event considerably increase their strength, hence reducing the amount of carbonate being deposited on slope sites. Moreover, by combining results from deep-sea oxygen isotopes with sea-level estimates based on coastal onlaps made during Leg 194, we constrain the amplitude of the N12-N14 sea-level fall to 90 meters. When integrating isotopic results from this study, this amplitude is lowered to 70 meters. A general conclusion of this work is that the mid Miocene climatic shift did impact carbonate systems, at least at the two locations studied. However, the nature of this response was highly dependant on the regional settings, in particular the presence of land mass (Malta

  18. Terrestrial and submarine evidence for the extent and timing of the Last Glacial Maximum and the onset of deglaciation on the maritime-Antarctic and sub-Antarctic islands

    Science.gov (United States)

    Hodgson, Dominic A.; Graham, Alastair G. C.; Roberts, Stephen J.; Bentley, Michael J.; Cofaigh, Colm Ó.; Verleyen, Elie; Vyverman, Wim; Jomelli, Vincent; Favier, Vincent; Brunstein, Daniel; Verfaillie, Deborah; Colhoun, Eric A.; Saunders, Krystyna M.; Selkirk, Patricia M.; Mackintosh, Andrew; Hedding, David W.; Nel, Werner; Hall, Kevin; McGlone, Matt S.; Van der Putten, Nathalie; Dickens, William A.; Smith, James A.

    2014-09-01

    This paper is the maritime and sub-Antarctic contribution to the Scientific Committee for Antarctic Research (SCAR) Past Antarctic Ice Sheet Dynamics (PAIS) community Antarctic Ice Sheet reconstruction. The overarching aim for all sectors of Antarctica was to reconstruct the Last Glacial Maximum (LGM) ice sheet extent and thickness, and map the subsequent deglaciation in a series of 5000 year time slices. However, our review of the literature found surprisingly few high quality chronological constraints on changing glacier extents on these timescales in the maritime and sub-Antarctic sector. Therefore, in this paper we focus on an assessment of the terrestrial and offshore evidence for the LGM ice extent, establishing minimum ages for the onset of deglaciation, and separating evidence of deglaciation from LGM limits from those associated with later Holocene glacier fluctuations. Evidence included geomorphological descriptions of glacial landscapes, radiocarbon dated basal peat and lake sediment deposits, cosmogenic isotope ages of glacial features and molecular biological data. We propose a classification of the glacial history of the maritime and sub-Antarctic islands based on this assembled evidence. These include: (Type I) islands which accumulated little or no LGM ice; (Type II) islands with a limited LGM ice extent but evidence of extensive earlier continental shelf glaciations; (Type III) seamounts and volcanoes unlikely to have accumulated significant LGM ice cover; (Type IV) islands on shallow shelves with both terrestrial and submarine evidence of LGM (and/or earlier) ice expansion; (Type V) Islands north of the Antarctic Polar Front with terrestrial evidence of LGM ice expansion; and (Type VI) islands with no data. Finally, we review the climatological and geomorphological settings that separate the glaciological history of the islands within this classification scheme.

  19. A simulated Antarctic fast ice ecosystem

    Science.gov (United States)

    Arrigo, Kevin R.; Kremer, James N.; Sullivan, Cornelius W.

    1993-01-01

    A 2D numerical ecosystem model of Antarctic land fast ice is developed to elucidate the primary production with the Antarctic sea ice zone. The physical component employs atmospheric data to simulate congelation ice growth, initial brine entrapment, desalination, and nutrient flux. The biological component is based on the concept of a maximum temperature-dependent algal growth rate which is reduced by limitations imposed from insufficient light or nutrients, as well as suboptimal salinity. Preliminary simulations indicate that, during a bloom, microalgae are able to maintain their vertical position relative to the lower congelation ice margin and are not incorporated into the crystal matrix as the ice sheet thickens. It is inferred that land fast sea ice contains numerous microhabitats that are functionally distinct based upon the unique set of processes that control microalgal growth and accumulation within each.

  20. The signs of Antarctic ozone hole recovery.

    Science.gov (United States)

    Kuttippurath, Jayanarayanan; Nair, Prijitha J

    2017-04-03

    Absorption of solar radiation by stratospheric ozone affects atmospheric dynamics and chemistry, and sustains life on Earth by preventing harmful radiation from reaching the surface. Significant ozone losses due to increases in the abundances of ozone depleting substances (ODSs) were first observed in Antarctica in the 1980s. Losses deepened in following years but became nearly flat by around 2000, reflecting changes in global ODS emissions. Here we show robust evidence that Antarctic ozone has started to recover in both spring and summer, with a recovery signal identified in springtime ozone profile and total column measurements at 99% confidence for the first time. Continuing recovery is expected to impact the future climate of that region. Our results demonstrate that the Montreal Protocol has indeed begun to save the Antarctic ozone layer.

  1. Redox conditions in sediments and during sedimentation in the Ontong Java Plateau, west equatorial Pacific

    Institute of Scientific and Technical Information of China (English)

    LU Bo; LI Tiegang; YU Xinke; CHANG Fengming; NAN Qingyun

    2011-01-01

    Redox-sensitive elements in sediments,such as manganese (Mn),vanadium (V),molybdenum (Mo),and uranium (U),are promising indicators of past redox conditions during sedimentation and early diagenesis.However,in the Ontong Java Plateau,west equatorial Pacific,there are sparse datasets of redox-sensitive elements in sediment cores.Here,we present a 250 ka record of redox sensitive elements from a 460 em gravity core at site WP7 (3°56'S,156°E,water depth 1 800 m),which was recovered from the southwest Ontong Java Plateau during the 1993 cruise of R/V Science Ⅰ of the Institute of Oceanology,Chinese Academy of Sciences (IOCAS).Relative to the Post-Archean Australian Shale (PAAS),authigenic Mn,cobalt (Co),nickel (Ni),Mo,V,U,and cadmium (Cd) were found at constantly low levels except when peaks occurred at several depth intervals.Manganese,Co,Ni,and Mo concentrations were elevated at 25-35 cm due to Mn redox cycling.The core was divided into three distinct sections,the top 0-25 cm being oxic,a suboxic section at 25-35 cm and from 35- 460 cm which was anoxic.Differential authigenic enrichments of Co,Ni,Mo,V,U,and Cd at the same depth intervals were observed indicating that the enrichments happened during sedimentation or diagenesis and suffered no post settlement redox changes.Therefore,no significant changes in redox conditions during sedimentation must have happened.The water at depth on the Ontong Java Plateau during past 250 ka must have been well oxygenated,possibly resulted from the more or less continuous presence of oxygen-rich deep water like the modem Antarctic Intermediate Water (AAIW) and Antarctic Circumpolar Water (ACW); while it's slightly less oxygenated in glacial intervals,possibly due to ventilation weakening and/or the surface productivity increase.

  2. An Interdisciplinary Method for the Visualization of Novel High-Resolution Precision Photography and Micro-XCT Data Sets of NASA's Apollo Lunar Samples and Antarctic Meteorite Samples to Create Combined Research-Grade 3D Virtual Samples for the Benefit of Astromaterials Collections Conservation, Curation, Scientific Research and Education

    Science.gov (United States)

    Blumenfeld, E. H.; Evans, C. A.; Zeigler, R. A.; Righter, K.; Beaulieu, K. R.; Oshel, E. R.; Liddle, D. A.; Hanna, R.; Ketcham, R. A.; Todd, N. S.

    2016-12-01

    New technologies make possible the advancement of documentation and visualization practices that can enhance conservation and curation protocols for NASA's Astromaterials Collections. With increasing demands for accessibility to updated comprehensive data, and with new sample return missions on the horizon, it is of primary importance to develop new standards for contemporary documentation and visualization methodologies. Our interdisciplinary team has expertise in the fields of heritage conservation practices, professional photography, photogrammetry, imaging science, application engineering, data curation, geoscience, and astromaterials curation. Our objective is to create virtual 3D reconstructions of Apollo Lunar and Antarctic Meteorite samples that are a fusion of two state-of-the-art data sets: the interior view of the sample by collecting Micro-XCT data and the exterior view of the sample by collecting high-resolution precision photography data. These new data provide researchers an information-rich visualization of both compositional and textural information prior to any physical sub-sampling. Since January 2013 we have developed a process that resulted in the successful creation of the first image-based 3D reconstruction of an Apollo Lunar Sample correlated to a 3D reconstruction of the same sample's Micro-XCT data, illustrating that this technique is both operationally possible and functionally beneficial. In May of 2016 we began a 3-year research period during which we aim to produce Virtual Astromaterials Samples for 60 high-priority Apollo Lunar and Antarctic Meteorite samples and serve them on NASA's Astromaterials Acquisition and Curation website. Our research demonstrates that research-grade Virtual Astromaterials Samples are beneficial in preserving for posterity a precise 3D reconstruction of the sample prior to sub-sampling, which greatly improves documentation practices, provides unique and novel visualization of the sample's interior and

  3. An Interdisciplinary Method for the Visualization of Novel High-Resolution Precision Photography and Micro-XCT Data Sets of NASA's Apollo Lunar Samples and Antarctic Meteorite Samples to Create Combined Research-Grade 3D Virtual Samples for the Benefit of Astromaterials Collections Conservation, Curation, Scientific Research and Education

    Science.gov (United States)

    Blumenfeld, E. H.; Evans, C. A.; Oshel, E. R.; Liddle, D. A.; Beaulieu, K.; Zeigler, R. A.; Hanna, R. D.; Ketcham, R. A.

    2016-01-01

    New technologies make possible the advancement of documentation and visualization practices that can enhance conservation and curation protocols for NASA's Astromaterials Collections. With increasing demands for accessibility to updated comprehensive data, and with new sample return missions on the horizon, it is of primary importance to develop new standards for contemporary documentation and visualization methodologies. Our interdisciplinary team has expertise in the fields of heritage conservation practices, professional photography, photogrammetry, imaging science, application engineering, data curation, geoscience, and astromaterials curation. Our objective is to create virtual 3D reconstructions of Apollo Lunar and Antarctic Meteorite samples that are a fusion of two state-of-the-art data sets: the interior view of the sample by collecting Micro-XCT data and the exterior view of the sample by collecting high-resolution precision photography data. These new data provide researchers an information-rich visualization of both compositional and textural information prior to any physical sub-sampling. Since January 2013 we have developed a process that resulted in the successful creation of the first image-based 3D reconstruction of an Apollo Lunar Sample correlated to a 3D reconstruction of the same sample's Micro- XCT data, illustrating that this technique is both operationally possible and functionally beneficial. In May of 2016 we began a 3-year research period during which we aim to produce Virtual Astromaterials Samples for 60 high-priority Apollo Lunar and Antarctic Meteorite samples and serve them on NASA's Astromaterials Acquisition and Curation website. Our research demonstrates that research-grade Virtual Astromaterials Samples are beneficial in preserving for posterity a precise 3D reconstruction of the sample prior to sub-sampling, which greatly improves documentation practices, provides unique and novel visualization of the sample's interior and

  4. Records of anthropogenic antimony in the glacial snow from the southeastern Tibetan Plateau

    Science.gov (United States)

    Zhang, Yulan; Kang, Shichang; Chen, Pengfei; Li, Xiaofei; Liu, Yajun; Gao, Tanguang; Guo, Junming; Sillanpää, Mika

    2016-12-01

    Antimony (Sb) is a ubiquitous element in the environment that is potentially toxic at very low concentrations. In this study, surface snow/ice and snowpit samples were collected from four glaciers in the southeastern Tibetan Plateau in June 2015. The concentrations of Sb and other elements were measured in these samples. The results showed that the average concentration of Sb was approximately 2.58 pg g-1 with a range of 1.64-9.20 pg g-1. The average Sb concentration in the study area was comparable to that recorded in a Mt. Everest ice core and higher than that in Arctic and Antarctic snow/ice but much lower than that in Tien Shan and Alps ice cores. Sb presented different variations with other toxic elements (Pb and Cr) and a crustal element (Al) in the three snowpits, which indicated the impact of a different source or post-deposition processes. The enrichment factor of Sb was larger than 10, suggesting that anthropogenic sources provided important contributions to Sb deposition in the glaciers. The Sb in the glacial snow was mainly loaded in the fourth component in principal component analysis, exhibiting discrepancies with crustal elements (Fe and Ca) and other toxic metals (Pb). Backward trajectories revealed that the air mass arriving at the southeastern Tibetan Plateau mostly originated from the Bay of Bengal and the South Asia in June. Thus, pollutants from the South Asia could play an important role in Sb deposition in the studied region. The released Sb from glacier meltwater in the Tibetan Plateau and surrounding areas might pose a risk to the livelihoods and well-being of those in downstream regions.

  5. EBSD in Antarctic and Greenland Ice

    Science.gov (United States)

    Weikusat, Ilka; Kuiper, Ernst-Jan; Pennock, Gill; Sepp, Kipfstuhl; Drury, Martyn

    2017-04-01

    Ice, particularly the extensive amounts found in the polar ice sheets, impacts directly on the global climate by changing the albedo and indirectly by supplying an enormous water reservoir that affects sea level change. The discharge of material into the oceans is partly controlled by the melt excess over snow accumulation, partly by the dynamic flow of ice. In addition to sliding over bedrock, an ice body deforms gravitationally under its own weight. In order to improve our description of this flow, ice microstructure studies are needed that elucidate the dominant deformation and recrystallization mechanisms involved. Deformation of hexagonal ice is highly anisotropic: ice is easily sheared in the basal plane and is about two orders of magnitude harder parallel to the c-axis. As dislocation creep is the dominant deformation mechanism in polar ice this strong anisotropy needs to be understood in terms of dislocation activity. The high anisotropy of the ice crystal is usually ascribed to a particular behaviour of dislocations in ice, namely the extension of dislocations into partials on the basal plane. Analysis of EBSD data can help our understanding of dislocation activity by characterizing subgrain boundary types thus providing a tool for comprehensive dislocation characterization in polar ice. Cryo-EBSD microstructure in combination with light microscopy measurements from ice core material from Antarctica (EPICA-DML deep ice core) and Greenland (NEEM deep ice core) are presented and interpreted regarding substructure identification and characterization. We examined one depth for each ice core (EDML: 656 m, NEEM: 719 m) to obtain the first comparison of slip system activity from the two ice sheets. The subgrain boundary to grain boundary threshold misorientation was taken to be 3-5° (Weikusat et al. 2011). EBSD analyses suggest that a large portion of edge dislocations with slip systems basal gliding on the basal plane were indeed involved in forming subgrain

  6. Magnetic anisotropy and porosity of Antarctic chondrites

    OpenAIRE

    Hamano,Yozo/Yomogida,Kiyoshi

    1982-01-01

    Magnetic susceptibility anisotropy and porosity were measured in eleven Antarctic meteorites. These meteorites are ordinary chondrites (H and L type) in various metamorphic stages. Large magnetic anisotropy has been observed in most of the chondrites. The foliation type of the anisotropy, inferred from the shape of the susceptibility ellipsoid indicates that a uniaxial compressional type deformation is responsible for the anisotropy. The degree of the anisotropy and the porosity do not correl...

  7. Structural Uncertainty in Antarctic sea ice simulations

    Science.gov (United States)

    Schneider, D. P.

    2016-12-01

    The inability of the vast majority of historical climate model simulations to reproduce the observed increase in Antarctic sea ice has motivated many studies about the quality of the observational record, the role of natural variability versus forced changes, and the possibility of missing or inadequate forcings in the models (such as freshwater discharge from thinning ice shelves or an inadequate magnitude of stratospheric ozone depletion). In this presentation I will highlight another source of uncertainty that has received comparatively little attention: Structural uncertainty, that is, the systematic uncertainty in simulated sea ice trends that arises from model physics and mean-state biases. Using two large ensembles of experiments from the Community Earth System Model (CESM), I will show that the model is predisposed towards producing negative Antarctic sea ice trends during 1979-present, and that this outcome is not simply because the model's decadal variability is out-of-synch with that in nature. In the "Tropical Pacific Pacemaker" ensemble, in which observed tropical Pacific SST anomalies are prescribed, the model produces very realistic atmospheric circulation trends over the Southern Ocean, yet the sea ice trend is negative in every ensemble member. However, if the ensemble-mean trend (commonly interpreted as the forced response) is removed, some ensemble members show a sea ice increase that is very similar to the observed. While this results does confirm the important role of natural variability, it also suggests a strong bias in the forced response. I will discuss the reasons for this systematic bias and explore possible remedies. This an important problem to solve because projections of 21st -Century changes in the Antarctic climate system (including ice sheet surface mass balance changes and related changes in the sea level budget) have a strong dependence on the mean state of and changes in the Antarctic sea ice cover. This problem is not unique to

  8. Antarctic ice sheet discharge driven by atmosphere-ocean feedbacks at the Last Glacial Termination

    Science.gov (United States)

    Fogwill, C. J.; Turney, C. S. M.; Golledge, N. R.; Etheridge, D. M.; Rubino, M.; Thornton, D. P.; Baker, A.; Woodward, J.; Winter, K.; van Ommen, T. D.; Moy, A. D.; Curran, M. A. J.; Davies, S. M.; Weber, M. E.; Bird, M. I.; Munksgaard, N. C.; Menviel, L.; Rootes, C. M.; Ellis, B.; Millman, H.; Vohra, J.; Rivera, A.; Cooper, A.

    2017-01-01

    Reconstructing the dynamic response of the Antarctic ice sheets to warming during the Last Glacial Termination (LGT; 18,000–11,650 yrs ago) allows us to disentangle ice-climate feedbacks that are key to improving future projections. Whilst the sequence of events during this period is reasonably well-known, relatively poor chronological control has precluded precise alignment of ice, atmospheric and marine records, making it difficult to assess relationships between Antarctic ice-sheet (AIS) dynamics, climate change and sea level. Here we present results from a highly-resolved ‘horizontal ice core’ from the Weddell Sea Embayment, which records millennial-scale AIS dynamics across this extensive region. Counterintuitively, we find AIS mass-loss across the full duration of the Antarctic Cold Reversal (ACR; 14,600–12,700 yrs ago), with stabilisation during the subsequent millennia of atmospheric warming. Earth-system and ice-sheet modelling suggests these contrasting trends were likely Antarctic-wide, sustained by feedbacks amplified by the delivery of Circumpolar Deep Water onto the continental shelf. Given the anti-phase relationship between inter-hemispheric climate trends across the LGT our findings demonstrate that Southern Ocean-AIS feedbacks were controlled by global atmospheric teleconnections. With increasing stratification of the Southern Ocean and intensification of mid-latitude westerly winds today, such teleconnections could amplify AIS mass loss and accelerate global sea-level rise.

  9. Screening and molecular classification of low-temperature protease from Antarctic microorganism and its characterization

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    107 strains producing protease were screened from 260 strains of Antarctic psychrophilic bacteria, among which proteolytic activity of five strains was more than 45 U ml-1. The 16S rRNA gene sequences homology and phylogenetic analysis of five Antarctic psychrophilic bacteria showed that NJ276、 NJ5-9、NJ16-70、NJ345 belonged to the described genus Pseudoalteromonas and NJ341belonged to the genus Colwellia. The growth and the protease characteristic of four Antarctic psychrophilic bacteria had been studied, and the result showed that the optimal temperature for growth and protease-producing of four strains was about 10 ℃. Their growth and protease-producing were still high during incubating 2-5 days. The maximum proteolytic activity occurred at pH 9 for four Antarctic psychrophilic bacteria. The optimal temperature of protease action of both strains NJ276 and NJ5-9 was about 50 ℃, however, the optimal temperature of protease action of both strains NJ341 and NJ345 was about 40 ℃, and their proteolytic activity under 0 ℃ exhibited nearly 30% of the maximum activity,but their thermal stabilities were weaker. These results indicated that proteases from NJ341 and NJ345 were low-temperature proteases.

  10. The Hikurangi Plateau: Tectonic Ricochet and Accretion

    Science.gov (United States)

    Willis, David; Moresi, Louis; Betts, Peter; Whittaker, Joanne

    2015-04-01

    80 million years between interactions with different subduction systems provided time for the Hikurangi Plateau and Pacific Ocean lithosphere to cool, densify and strengthen. Neogene subduction of the Hikurangi Plateau occurring orthogonal to its Cretaceous predecessor, provides a unique opportunity to explore how changes to the physical properties of oceanic lithosphere affect subduction dynamics. We used Underworld to build mechanically consistent collision models to understand the dynamics of the two Hikurangi collisions. The Hikurangi Plateau is a ~112 Ma, 15km thick oceanic plateau that has been entrained by subduction zones immediately preceding the final break-up of Eastern Gondwana and currently within the active Hikurangi Margin. We explore why attempted subduction of the plateau has resulted in vastly different dynamics on two separate occasions. Slab break-off occured during the collision with Gondwana, currently there is apparent subduction of the plateau underneath New Zealand. At ~100Ma the young, hot Hikurangi Plateau, positively buoyant with respect to the underlying mantle, impacted a Gondwana Margin under rapid extension after the subduction of an mid-ocean ridge 10-15Ma earlier. Modelling of plateaus within young oceanic crust indicates that subduction of the thickened crust was unlikely to occur. Frontal accretion of the plateau and accompanying slab break-off is expected to have occured rapidly after its arrival. The weak, young slab was susceptible to lateral propagation of the ~1500 km window opened by the collision, and break-off would have progressed along the subduction zone inhibiting the "step-back" of the trench seen in older plates. Slab break-off coincided with a world-wide reorganisation of plate velocites, and orogenic collapse along the Gondwana margin characterised by rapid extension and thinning of the over-riding continental plate from ~60 to 30km. Following extension, Zealandia migrated to the NW until the Miocene allowing the

  11. Antarctic Meteorite Classification and Petrographic Database Enhancements

    Science.gov (United States)

    Todd, N. S.; Satterwhite, C. E.; Righter, K.

    2012-01-01

    The Antarctic Meteorite collection, which is comprised of over 18,700 meteorites, is one of the largest collections of meteorites in the world. These meteorites have been collected since the late 1970 s as part of a three-agency agreement between NASA, the National Science Foundation, and the Smithsonian Institution [1]. Samples collected each season are analyzed at NASA s Meteorite Lab and the Smithsonian Institution and results are published twice a year in the Antarctic Meteorite Newsletter, which has been in publication since 1978. Each newsletter lists the samples collected and processed and provides more in-depth details on selected samples of importance to the scientific community. Data about these meteorites is also published on the NASA Curation website [2] and made available through the Meteorite Classification Database allowing scientists to search by a variety of parameters. This paper describes enhancements that have been made to the database and to the data and photo acquisition process to provide the meteorite community with faster access to meteorite data concurrent with the publication of the Antarctic Meteorite Newsletter twice a year.

  12. Antarctic isolation: immune and viral studies

    Science.gov (United States)

    Tingate, T. R.; Lugg, D. J.; Muller, H. K.; Stowe, R. P.; Pierson, D. L.

    1997-01-01

    Stressful environmental conditions are a major determinant of immune reactivity. This effect is pronounced in Australian National Antarctic Research Expedition populations exposed to prolonged periods of isolation in the Antarctic. Alterations of T cell function, including depression of cutaneous delayed-type hypersensitivity responses and a peak 48.9% reduction of T cell proliferation to the mitogen phytohaemagglutinin, were documented during a 9-month period of isolation. T cell dysfunction was mediated by changes within the peripheral blood mononuclear cell compartment, including a paradoxical atypical monocytosis associated with altered production of inflammatory cytokines. There was a striking reduction in the production by peripheral blood mononuclear cells of the predominant pro-inflammatory monokine TNF-alpha and changes were also detected in the production of IL-1, IL-2, IL-6, IL-1ra and IL-10. Prolonged Antarctic isolation is also associated with altered latent herpesvirus homeostasis, including increased herpesvirus shedding and expansion of the polyclonal latent Epstein-Barr virus-infected B cell population. These findings have important long-term health implications.

  13. Antarctic Treaty Summit: Washington, DC (2009)

    Science.gov (United States)

    Berkman, P. A.; Young, O. R.

    2005-12-01

    Advancement in Earth system science and international cooperation have been intertwined with the International Polar Years since 1882. In particular, the 3rd International Polar Year (which was convened as the International Geophysical Year from 1 July 1957 through 31 December 1958) specifically demonstrates the role of science in international policy: Acknowledging the substantial contributions to scientific knowledge resulting from international cooperation in scientific investigation in Antarctica; Convinced that the establishment of a firm foundation for the continuation and development of such cooperation on the basis of freedom of scientific investigation in Antarctica as applied during the International Geophysical Year accords with the interests of science and the progress of all mankind; Preamble, 1959 Antarctic Treaty To commemorate the 50th anniversary of the 1959 Antarctic Treaty and to explore the complexities of the science-policy relationship through the lens of a well-constrained case study, an international and interdisciplinary Antarctic Treaty Summit is being planned for 2009 in Washington, DC in conjunction with the International Polar Year 2007-08 (http://www.ipy.org).

  14. Mirror seeing of the Antarctic survey telescope

    Institute of Scientific and Technical Information of China (English)

    ZHANG Kaiyuan; LI Zhengyang; YUAN Xiangyan; PEI Chong

    2014-01-01

    Site testing results indicate that Antarctic Dome A is an excellent ground-based astronomical site suitable for observations ranging from visible to infrared wavelengths. However, the harsh environment in Antarctica, especially the very low temperature and atmospheric pressure, always produces frost on the telescopes’ mirrors, which are exposed to the air. Since the Dome A site is still unattended, the Antarctic telescope tubes are always designed to be filled with dry nitrogen, and the outer surfaces of the optical system are heated by an indium-tin oxide thin film. These precautions can prevent the optical surfaces from frosting over, but they degrade the image quality by introducing additional mirror seeing. Based on testing observations of the second Antarctic Survey Telescope (AST3-2) in the Mohe site in China, mirror seeing resulting from the heated aspheric plate has been measured using micro-thermal sensors. Results comparing the real-time atmospheric seeing monitored by the Differential Image Motion Monitor and real-time examinations of image quality agree well.

  15. A paleomagnetic study of the Antarctic Peninsula

    Science.gov (United States)

    Poblete, F.; Arriagada, C.; Roperch, P.

    2009-05-01

    In the Paleozoic, South America, South Africa and Antarctica were part of Gondwana. The Weddell Sea began to form at about 146 Ma, after rifting between the Antarctic Peninsula and southernmost South America. Much uncertainty still exists about the geometrical fit and subsequent drift history between Patagonia and Antarctica. Geophysical and geological data which describe the tectonic history are sparsely distributed and often of poor quality. During the last two years we have collected more than 1000 paleomagnetic samples from 70 sites at several localities (King George Island, Robert Island, Yankee Bay, Half Moon Island, Byers Peninsula and Snow Island) from the South Shetland Islands and Anderson Island in the northern tip of Antarctic Peninsula. Our main objective was to provide first-order constraints on latitudinal displacements and the amount of tectonic rotations as an essential test of published tectonic models. Paleomagnetic results were obtained from 50 sites. All samples from sites in volcanic and intrusive rocks have well-defined univectorial magnetizations. Unfortunately, all sites in late Paleozoic sediments have been remagnetized and the magnetizations are often unstable upon thermal demagnetization. Cretaceous and Cenozoic units display very little apparent polar wander. Results from intrusive rocks of expected Jurassic age do not confirm the expected relative rotation betwen the Antarctic Peninsula and East Antarctica. Further radiometric dating are needed to confirm the age of these units.

  16. Update on terrestrial ages of Antarctic meteorites

    Energy Technology Data Exchange (ETDEWEB)

    Welten, K C; Nishiizumi, K; Caffee, M W

    2000-01-14

    Terrestrial ages of Antarctic meteorites are one of the few parameters that will help us to understand the meteorite concentration mechanism on blue-ice fields. Traditionally, terrestrial ages were determined on the basis of {sup 36}Cl in the metal phase, which has an uncertainty of about 70 ky. For young meteorites (< 40 ky), the terrestrial age is usually and most accurately determined using {sup 14}C in the stone phase. In recent years two methods have been developed which are independent of shielding effects, the {sup 10}Be-{sup 36}Cl/{sup 10}Be method and the {sup 41}Ca/{sup 36}Cl method. These methods have reduced the typical uncertainties in terrestrial ages by a factor of 2, to about 30 ky. The {sup 10}Be-{sup 36}Cl/{sup 10}Be method is quite dependent on the exposure age, which is unknown for most Antarctic meteorites. The authors therefore also attempt to use the relation between {sup 26}Al and {sup 36}Cl/{sup 26}Al to derive a terrestrial age less dependent on the exposure age. The authors have measured the concentrations of cosmogenic {sup 10}Be, {sup 26}Al and {sup 36}Cl in the metal phase of {approximately} 70 Antarctic meteorites, from more than 10 different ice-fields, including many new ones. They then discuss the trends in terrestrial ages of meteorites from different ice-fields.

  17. The association of Antarctic krill Euphausia superba with the under-ice habitat.

    Directory of Open Access Journals (Sweden)

    Hauke Flores

    Full Text Available The association of Antarctic krill Euphausia superba with the under-ice habitat was investigated in the Lazarev Sea (Southern Ocean during austral summer, autumn and winter. Data were obtained using novel Surface and Under Ice Trawls (SUIT, which sampled the 0-2 m surface layer both under sea ice and in open water. Average surface layer densities ranged between 0.8 individuals m(-2 in summer and autumn, and 2.7 individuals m(-2 in winter. In summer, under-ice densities of Antarctic krill were significantly higher than in open waters. In autumn, the opposite pattern was observed. Under winter sea ice, densities were often low, but repeatedly far exceeded summer and autumn maxima. Statistical models showed that during summer high densities of Antarctic krill in the 0-2 m layer were associated with high ice coverage and shallow mixed layer depths, among other factors. In autumn and winter, density was related to hydrographical parameters. Average under-ice densities from the 0-2 m layer were higher than corresponding values from the 0-200 m layer collected with Rectangular Midwater Trawls (RMT in summer. In winter, under-ice densities far surpassed maximum 0-200 m densities on several occasions. This indicates that the importance of the ice-water interface layer may be under-estimated by the pelagic nets and sonars commonly used to estimate the population size of Antarctic krill for management purposes, due to their limited ability to sample this habitat. Our results provide evidence for an almost year-round association of Antarctic krill with the under-ice habitat, hundreds of kilometres into the ice-covered area of the Lazarev Sea. Local concentrations of postlarval Antarctic krill under winter sea ice suggest that sea ice biota are important for their winter survival. These findings emphasise the susceptibility of an ecological key species to changing sea ice habitats, suggesting potential ramifications on Antarctic ecosystems induced by climate

  18. Tectonomagmatic Associations on the Central Andean Plateau

    Science.gov (United States)

    de Silva, S. L.; Viramonte, J. G.

    2012-12-01

    The Neogene evolution of the Central Andes is characterized by a strong association between plate convergence, mountain building and plateau formation, and magmatism. Plateau uplift by crustal shortening and thickening in the lower crust is broadly coincident with large scale silicic magmatism defined by the Neogene Central Andean ignimbrite province. Of particular interest here are the spatiotemporal correlations between silicic magmatism and tectonic evolution of the Altiplano-Puna plateau. Although magmatism is driven by the subduction-related flux from mantle to crust, the shift to "crustal" magmatism as indicated by elevated crustal isotopic indices after ~10Ma suggests a link between crustal thickening, plateau formation and silicic magmatism. In particular, elevated geotherms associated with crustal thickening and enhanced mantle flux associated with lithospheric delamination may have played a role in thermally preparing the Central Andean crust for enhanced silicic magma production during the extensive Neogene ignimbrite flare-up. Emplacement of these magmas in the upper crust throughout the Neogene may have fuelled a period of significant interaction between magmatism and tectonism on the plateau. With particular reference to the 21° to 24°S segment of the Central Andes, spatial and structural coincidence of calderas of the Altiplano Puna Volcanic Complex with the NW-SE striking Calama-Olacapata-El Toro fault zone suggests significant tectonomagmatic interaction. Location of calderas suggest that these regional faults focused magma intrusion and storage, while spatially and temporally correlated eruption pulses connote a tectonic control. Indeed, current thermomechanical models of magma chamber development and eruption triggering promote a role for external triggering of "perched" upper crustal magma chambers. This might have been achieved by melt-enhanced deformation, or alternatively, significant uplift (~1km) associated with the development of large

  19. Diversity and distribution patterns in high southern latitude sponges.

    Directory of Open Access Journals (Sweden)

    Rachel V Downey

    Full Text Available Sponges play a key role in Antarctic marine benthic community structure and dynamics and are often a dominant component of many Southern Ocean benthic communities. Understanding the drivers of sponge distribution in Antarctica enables us to understand many of general benthic biodiversity patterns in the region. The sponges of the Antarctic and neighbouring oceanographic regions were assessed for species richness and biogeographic patterns using over 8,800 distribution records. Species-rich regions include the Antarctic Peninsula, South Shetland Islands, South Georgia, Eastern Weddell Sea, Kerguelen Plateau, Falkland Islands and north New Zealand. Sampling intensity varied greatly within the study area, with sampling hotspots found at the Antarctic Peninsula, South Georgia, north New Zealand and Tierra del Fuego, with limited sampling in the Bellingshausen and Amundsen seas in the Southern Ocean. In contrast to previous studies we found that eurybathy and circumpolar distributions are important but not dominant characteristics in Antarctic sponges. Overall Antarctic sponge species endemism is ∼43%, with a higher level for the class Hexactinellida (68%. Endemism levels are lower than previous estimates, but still indicate the importance of the Polar Front in isolating the Southern Ocean fauna. Nineteen distinct sponge distribution patterns were found, ranging from regional endemics to cosmopolitan species. A single, distinct Antarctic demosponge fauna is found to encompass all areas within the Polar Front, and the sub-Antarctic regions of the Kerguelen Plateau and Macquarie Island. Biogeographical analyses indicate stronger faunal links between Antarctica and South America, with little evidence of links between Antarctica and South Africa, Southern Australia or New Zealand. We conclude that the biogeographic and species distribution patterns observed are largely driven by the Antarctic Circumpolar Current and the timing of past continent

  20. The surface layer observed by a high-resolution sodar at DOME C, Antarctica

    Directory of Open Access Journals (Sweden)

    Stefania Argentini

    2014-01-01

    Full Text Available One year field experiment has started on December 2011 at the French - Italian station of Concordia at Dome C, East Antarctic Plateau. The objective of the experiment is the study of the surface layer turbulent processes under stable/very stable stratifications, and the mechanisms leading to the formation of the warming events. A sodar was improved to achieve the vertical/time resolution needed to study these processes. The system, named Surface Layer sodar (SL-sodar, may operate both in high vertical resolution (low range and low vertical resolution (high range modes. In situ turbulence and radiation measurements were also provided in the framework of this experiment. A few preliminary results, concerning the standard summer diurnal cycle, a summer warming event, and unusually high frequency boundary layer atmospheric gravity waves are presented.

  1. Analysis of the structure of different Tibetan Plateau vortex types

    Science.gov (United States)

    Feng, Xinyuan; Liu, Changhai; Fan, Guangzhou; Zhang, Jie

    2017-06-01

    Knowledge of the structure of the Tibetan Plateau vortex (TPV) is of considerable importance for understanding the generation and development mechanisms of this mesoscale system. However, our understanding of vortex structures and our ability to classify them on a physical basis is limited due to insufficient observations. The highresolution new-generation NCEP-CFSR (Climate Forecast System Reanalysis) dataset is used in the present paper to investigate the general structural features of various types of mature TPV through classification and composite structure analysis. Results indicate that the dynamic and thermodynamic structures show regional and seasonal dependency, as well as being influenced by attributes of translation, associated precipitation, and the South Asian high (SAH). The common precipitating TPV (type I), frequently occurring in the west-east-oriented zonal region between 33° and 36°N, is a notably low-level baroclinic and asymmetric system. It resides within a large-scale confluent zone and preferentially travels eastward, potentially moving out of the plateau. The heavy rain vortex (type II) corresponds to a deep vortex circulation occurring in midsummer. The low-level baroclinic sub-category (type IIa) is associated with a low-level jet and mainly originates in the area 32°-35°N, 86°-94°E, preferentially moving east of 90°E and even away from the plateau; meanwhile, the nearly upright sub-category (type IIb), which has a cold center at low levels and a warm center at mid-upper levels, is a quasi-stationary and quasi-symmetric system favorably occurring west of 92°E. A western-pattern SAH exists in the upper troposphere for these two sub-categories. The springtime dry vortex in the western plateau (type III) is warm and shallow (approximately 100 hPa deep), and zonal circulation dominates the large-scale environmental flows in the middle and upper troposphere. The precipitating vortex in the southern plateau occurring during July

  2. Present-day and future Antarctic ice sheet climate and surface mass balance in the Community Earth System Model

    Science.gov (United States)

    Lenaerts, Jan T. M.; Vizcaino, Miren; Fyke, Jeremy; van Kampenhout, Leo; van den Broeke, Michiel R.

    2016-09-01

    We present climate and surface mass balance (SMB) of the Antarctic ice sheet (AIS) as simulated by the global, coupled ocean-atmosphere-land Community Earth System Model (CESM) with a horizontal resolution of {˜ }1° in the past, present and future (1850-2100). CESM correctly simulates present-day Antarctic sea ice extent, large-scale atmospheric circulation and near-surface climate, but fails to simulate the recent expansion of Antarctic sea ice. The present-day Antarctic ice sheet SMB equals 2280 ± 131 {Gt year^{-1}}, which concurs with existing independent estimates of AIS SMB. When forced by two CMIP5 climate change scenarios (high mitigation scenario RCP2.6 and high-emission scenario RCP8.5), CESM projects an increase of Antarctic ice sheet SMB of about 70 {Gt year^{-1}} per degree warming. This increase is driven by enhanced snowfall, which is partially counteracted by more surface melt and runoff along the ice sheet's edges. This intensifying hydrological cycle is predominantly driven by atmospheric warming, which increases (1) the moisture-carrying capacity of the atmosphere, (2) oceanic source region evaporation, and (3) summer AIS cloud liquid water content.

  3. Continuing Colorado plateau uplift by delamination-style convective lithospheric downwelling.

    Science.gov (United States)

    Levander, A; Schmandt, B; Miller, M S; Liu, K; Karlstrom, K E; Crow, R S; Lee, C-T A; Humphreys, E D

    2011-04-28

    The Colorado plateau is a large, tectonically intact, physiographic province in the southwestern North American Cordillera that stands at ∼1,800-2,000 m elevation and has long been thought to be in isostatic equilibrium. The origin of these high elevations is unclear because unlike the surrounding provinces, which have undergone significant Cretaceous-Palaeogene compressional deformation followed by Neogene extensional deformation, the Colorado plateau is largely internally undeformed. Here we combine new seismic tomography and receiver function images to resolve a vertical high-seismic-velocity anomaly beneath the west-central plateau that extends more than 200 km in depth. The upper surface of this anomaly is seismically defined by a dipping interface extending from the lower crust to depths of 70-90 km. The base of the continental crust above the anomaly has a similar shape, with an elevated Moho. We interpret these seismic structures as a continuing regional, delamination-style foundering of lower crust and continental lithosphere. This implies that Pliocene (2.6-5.3 Myr ago) uplift of the plateau and the magmatism on its margins are intimately tied to continuing deep lithospheric processes. Petrologic and geochemical observations indicate that late Cretaceous-Palaeogene (∼90-40 Myr ago) low-angle subduction hydrated and probably weakened much of the Proterozoic tectospheric mantle beneath the Colorado plateau. We suggest that mid-Cenozoic (∼35-25 Myr ago) to Recent magmatic infiltration subsequently imparted negative compositional buoyancy to the base and sides of the Colorado plateau upper mantle, triggering downwelling. The patterns of magmatic activity suggest that previous such events have progressively removed the Colorado plateau lithosphere inward from its margins, and have driven uplift. Using Grand Canyon incision rates and Pliocene basaltic volcanism patterns, we suggest that this particular event has been active over the past ∼6 Myr.

  4. Sino-Japanese Teamwork Probes Environment Changes on Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    @@ With the support of a CAS project on Holocene environmental changes and their influences on the ecosystem of the Tibetan Plateau, a research group headed by Prof. Zhu Liping from the CAS Institute of Tibetan Plateau Research and their Japanese collaborators carried out a field survey in Puma Yumco area on the Tibetan Plateau from September 8 to 20.

  5. Potential genesis and implications of calcium nitrate in Antarctic snow

    Science.gov (United States)

    Mahalinganathan, Kanthanathan; Thamban, Meloth

    2016-04-01

    Among the large variety of particulates in the atmosphere, calcic mineral dust particles have highly reactive surfaces that undergo heterogeneous reactions with atmospheric acids contiguously. The association between nssCa2+, an important proxy indicator of mineral dust, and NO3-, a dominant anion in the Antarctic snowpack, was analysed. A total of 41 snow cores ( ˜ 1 m each) that represent snow deposited during 2008-2009 were studied along coastal-inland transects from two different regions in East Antarctica - the Princess Elizabeth Land (PEL) and central Dronning Maud Land (cDML). Correlation statistics showed a strong association (at 99 % significance level) between NO3- and nssCa2+ at the near-coastal sections of both PEL (r = 0.74) and cDML (r = 0.82) transects. Similarly, a strong association between these ions was also observed in snow deposits at the inland sections of PEL (r = 0.73) and cDML (r = 0.84). Such systematic associations between nssCa2+ and NO3- are attributed to the interaction between calcic mineral dust and nitric acid in the atmosphere, leading to the formation of calcium nitrate (Ca(NO3)2) aerosol. Principal component analysis revealed common transport and depositional processes for nssCa2+ and NO3- both in PEL and cDML. Forward- and back-trajectory analyses using HYSPLIT model v. 4 revealed that southern South America (SSA) was an important dust-emitting source to the study region, aided by the westerlies. Particle size distribution showed that over 90 % of the dust was in the range dust particles reached the Antarctic region via long-range transport from the SSA region. We propose that the association between nssCa2+ and NO3- occurs during the long-range transport due to the formation of Ca(NO3)2 rather than to local neutralisation processes. However, the influence of local dust sources from the nunataks in cDML and the contribution of high sea salt in coastal PEL evidently mask such association in the mountainous and coastal regions

  6. The Hubble Flow of Plateau Inflation

    NARCIS (Netherlands)

    Coone, Dries; Roest, Diederik; Vennin, Vincent

    2015-01-01

    In the absence of CMB precision measurements, a Taylor expansion has often been invoked to parametrize the Hubble flow function during inflation. The standard "horizon flow" procedure implicitly relies on this assumption. However, the recent Planck results indicate a strong preference for plateau

  7. The Hubble Flow of Plateau Inflation

    NARCIS (Netherlands)

    Coone, Dries; Roest, Diederik; Vennin, Vincent

    2015-01-01

    In the absence of CMB precision measurements, a Taylor expansion has often been invoked to parametrize the Hubble flow function during inflation. The standard "horizon flow" procedure implicitly relies on this assumption. However, the recent Planck results indicate a strong preference for plateau in

  8. Ozone Minihole Found over Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Through a comprehensive analysis, researchers from the CAS Institute of Atmospheric Physics (IAP) discovered an ozone minihole, a large area with the lowest total ozone column (TOC, see figure), over the Qinghai-Tibet Plateau from Dec. 14 to 17, 2003.

  9. Planation Surfaces on the Tibet Plateau, China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A planation hypothesis is proposed to explain landform evolution of the Tibet Plateau. A denudation threshold (T), the maximum potential denudation rate for a certain type of rock, is introduced to explain the combined effects of lithology and tectonics on landform evolution. If the tectonic uplifting rate (U) is equal to or less than the threshold rate (U ≤ T), the tectonic uplifting and terrain denudation are in dynamic equilibrium, and landforms are in a steady state. The end product should be planation surfaces whether the original landforms are fiat plains or deeply dissected mountains. If U > T, uplift and denudation are not able to reach a dynamic equilibrium state. The plateau surface is mostly underlain by soft rocks, such as the Mesozoic epimetamorphic argillites and Tertiary sedimentary rocks, while the mountain ranges comprise hard rocks, such as granite, gneiss and limestone. In soft rock regions, hills are low with a relative relief of mostly less than 100m and the slopes are gentle at a gradient of <200. In contrast, hills can maintain steep slopes in hard rock regions. The Tibet Plateau has been under an equilibrium condition between tectonic uplifting and denudation except for the mountain ranges. The plateau might have reached the present altitudes before the Quaternary.

  10. Bacterial diversity of autotrophic enriched cultures from remote, glacial Antarctic, Alpine and Andean aerosol, snow and soil samples

    Science.gov (United States)

    González-Toril, E.; Amils, R.; Delmas, R. J.; Petit, J.-R.; Komárek, J.; Elster, J.

    2009-01-01

    Four different communities and one culture of autotrophic microbial assemblages were obtained by incubation of samples collected from high elevation snow in the Alps (Mt. Blanc area) and the Andes (Nevado Illimani summit, Bolivia), from Antarctic aerosol (French station Dumont d'Urville) and a maritime Antarctic soil (King George Island, South Shetlands, Uruguay Station Artigas), in a minimal mineral (oligotrophic) media. Molecular analysis of more than 200 16S rRNA gene sequences showed that all cultured cells belong to the Bacteria domain. Phylogenetic comparison with the currently available rDNA database allowed sequences belonging to Proteobacteria Alpha-, Beta- and Gamma-proteobacteria), Actinobacteria and Bacteroidetes phyla to be identified. The Andes snow culture was the richest in bacterial diversity (eight microorganisms identified) and the marine Antarctic soil the poorest (only one). Snow samples from Col du Midi (Alps) and the Andes shared the highest number of identified microorganisms (Agrobacterium, Limnobacter, Aquiflexus and two uncultured Alphaproteobacteria clones). These two sampling sites also shared four sequences with the Antarctic aerosol sample (Limnobacter, Pseudonocardia and an uncultured Alphaproteobacteriaclone). The only microorganism identified in the Antarctica soil (Brevundimonas sp.) was also detected in the Antarctic aerosol. Most of the identified microorganisms had been detected previously in cold environments, marine sediments soils and rocks. Air current dispersal is the best model to explain the presence of very specific microorganisms, like those identified in this work, in environments very distant and very different from each other.

  11. UV radiation and primary production in the Antarctic waters

    Digital Repository Service at National Institute of Oceanography (India)

    LokaBharathi, P.A.; Krishnakumari, L.; Bhattathiri, P.M.A.; Chandramohan, D.

    obtained between pp and the above parameters in the Antarctic sub-surface waters determined at discrete depths of 10, 20, 30 and 40 m. However, when the primary productivity values were normalised for PAR, a more negative effect was noticed at the Antarctic...

  12. Ice core reconstruction of Antarctic climate change and implications

    OpenAIRE

    Mayewski,Paul Andrew

    2012-01-01

    Antarctica is the Earth’s largest environmental library for ice cores. Examples of the scientific fin-dings of the 21-nation consortium called the International Trans Antarctic Scientific Expedition (ITASE) under the auspices of the Scientific Committee for Antarctic Research (SCAR) are presented with special emphasis on the value of these records in reconstructing atmospheric circulation over Antarctica and the Southern Ocean.

  13. The distribution of Fe in the Antarctic Circumpolar Current

    NARCIS (Netherlands)

    Löscher, B.M.; Baar, H.J.W. de; Jong, J.T.M. de; Veth, C.; Dehairs, F.

    1997-01-01

    The large-scale distributions of dissolved and total Fe in surface and deep waters of the Antarctic Circumpolar Current exhibit strong relationships with hydrography and biological processes. The mean dissolved Fe concentrations are low in surface waters of the Antarctic Circumpolar Current

  14. Challenges to the Future - Conservation of the Antarctic

    NARCIS (Netherlands)

    Chown, S.L.; Lee, J.E.; Hughes, K.A.; Barnes, J.; Bergstrom, D.M.; Convey, P.; Cowan, D.A.; Crosbie, K.; Dyer, G.; Frenot, Y.; Grant, S.M.; Herr, D.; Kennicutt, M.C.; Lamers, M.A.J.; Murray, A.; Possingham, H.P.; Reid, K.; Riddle, M.J.; Ryan, P.G.; Sanson, L.; Shaw, J.D.; Sparrow, M.D.; Summerhayes, C.; Terauds, A.; Wall, D.H.

    2012-01-01

    The Antarctic Treaty System, acknowledged as a successful model of cooperative regulation of one of the globe's largest commons (1), is under substantial pressure. Concerns have been raised about increased stress on Antarctic systems from global environmental change and growing interest in the regio

  15. The distribution of Fe in the Antarctic Circumpolar Current

    NARCIS (Netherlands)

    Löscher, B.M.; Baar, H.J.W. de; Jong, J.T.M. de; Veth, C.; Dehairs, F.

    1997-01-01

    The large-scale distributions of dissolved and total Fe in surface and deep waters of the Antarctic Circumpolar Current exhibit strong relationships with hydrography and biological processes. The mean dissolved Fe concentrations are low in surface waters of the Antarctic Circumpolar Current (0.31–0.

  16. Antarctic bacteria inhibit growth of foodborne microorganisms at low temperatures.

    NARCIS (Netherlands)

    A.C. O'Brien; R. Sharp; N.J. Russell; S. Roller

    2004-01-01

    The aim of this study was to identify Antarctic microorganisms with the ability to produce cold-active antimicrobial compounds with potential for use in chilled food preservation. Colonies (4496) were isolated from 12 Antarctic soil samples and tested against Listeria innocua, Pseudomonas fragi and

  17. Reaching for the Horizon: Enabling 21st Century Antarctic Science

    Science.gov (United States)

    Rogan-Finnemore, M.; Kennicutt, M. C., II; Kim, Y.

    2015-12-01

    The Council of Managers of National Antarctic Programs' (COMNAP) Antarctic Roadmap Challenges(ARC) project translated the 80 highest priority Antarctic and Southern Ocean scientific questionsidentified by the community via the SCAR Antarctic Science Horizon Scan into the highest prioritytechnological, access, infrastructure and logistics needs to enable the necessary research to answer thequestions. A workshop assembled expert and experienced An