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. (2016). Acquisition of isotopic composition for surface snow in East Antarctica and the links to climatic parameters (Vol. 10).
Abstract: Abstract. The isotopic compositions of oxygen and hydrogen in ice cores are invaluable tools for the reconstruction of past climate variations. Used alone, they give insights into the variations of the local temperature, whereas taken together they can provide information on the climatic conditions at the point of origin of the moisture. However, recent analyses of snow from shallow pits indicate that the climatic signal can become erased in very low accumulation regions, due to local processes of snow reworking. The signal-to-noise ratio decreases and the climatic signal can then only be retrieved using stacks of several snow pits. Obviously, the signal is not completely lost at this stage, otherwise it would be impossible to extract valuable climate information from ice cores as has been done, for instance, for the last glaciation. To better understand how the climatic signal is passed from the precipitation to the snow, we present here results from varied snow samples from East Antarctica. First, we look at the relationship between isotopes and temperature from a geographical point of view, using results from three traverses across Antarctica, to see how the relationship is built up through the distillation process. We also take advantage of these measures to see how second-order parameters (d-excess and 17O-excess) are related to ?18O and how they are controlled. d-excess increases in the interior of the continent (i.e., when ?18O decreases), due to the distillation process, whereas 17O-excess decreases in remote areas, due to kinetic fractionation at low temperature. In both cases, these changes are associated with the loss of original information regarding the source. Then, we look at the same relationships in precipitation samples collected over 1 year at Dome C and Vostok, as well as in surface snow at Dome C. We note that the slope of the ?18O vs. temperature (T) relationship decreases in these samples compared to those from the traverses, and thus caution is advocated when using spatial slopes for past climate reconstruction. The second-order parameters behave in the same way in the precipitation as in the surface snow from traverses, indicating that similar processes are active and that their interpretation in terms of source climatic parameters is strongly complicated by local temperature effects in East Antarctica. Finally we check if the same relationships between ?18O and second-order parameters are also found in the snow from four snow pits. While the d-excess remains opposed to ?18O in most snow pits, the 17O-excess is no longer positively correlated to ?18O and even shows anti-correlation to ?18O at Vostok. This may be due to a stratospheric influence at this site and/or to post-deposition processes.
Programme: 1177
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. (2018). Seasonal variations of the backscattering coefficient measured by radar altimeters over the Antarctic Ice Sheet (Vol. 12).
Abstract: Abstract. Spaceborne radar altimeters are a valuable tool for observing the Antarctic Ice Sheet. The radar wave interaction with the snow provides information on both the surface and the subsurface of the snowpack due to its dependence on the snow properties. However, the penetration of the radar wave within the snowpack also induces a negative bias on the estimated surface elevation. Empirical corrections of this space- and time-varying bias are usually based on the backscattering coefficient variability. We investigate the spatial and seasonal variations of the backscattering coefficient at the S (3.2GHz?9.4cm), Ku (13.6GHz?2.3cm) and Ka (37GHz?0.8cm) bands. We identified that the backscattering coefficient at Ku band reaches a maximum in winter in part of the continent (Region 1) and in the summer in the remaining (Region 2), while the evolution at other frequencies is relatively uniform over the whole continent. To explain this contrasting behavior between frequencies and between regions, we studied the sensitivity of the backscattering coefficient at three frequencies to several parameters (surface snow density, snow temperature and snow grain size) using an electromagnetic model. The results show that the seasonal cycle of the backscattering coefficient at Ka frequency is dominated by the volume echo and is mainly driven by snow temperature evolution everywhere. In contrast, at S band, the cycle is dominated by the surface echo. At Ku band, the seasonal cycle is dominated by the volume echo in Region 1 and by the surface echo in Region 2. This investigation provides new information on the seasonal dynamics of the Antarctic Ice Sheet surface and provides new clues to build more accurate corrections of the radar altimeter surface elevation signal in the future.
Programme: 1110
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. (2018). Archival processes of the water stable isotope signal in East Antarctic ice cores (Vol. 12).
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Emmanuel Le Meur, Olivier Magand, Laurent Arnaud, Michel Fily, Massimo Frezzotti, Marie Cavitte, Robert Mulvaney, Stefano Urbini. (2018). Spatial and temporal distributions of surface mass balance between Concordia and Vostok stations, Antarctica, from combined radar and ice core data: first results and detailed error analysis (Vol. 12). Bachelor's thesis, , .
Abstract: Abstract. Results from ground-penetrating radar (GPR) measurements and shallow ice cores carried out during a scientific traverse between Dome Concordia (DC) and Vostok stations are presented in order to infer both spatial and temporal characteristics of snow accumulation over the East Antarctic Plateau. Spatially continuous accumulation rates along the traverse are computed from the identification of three equally spaced radar reflections spanning about the last
Programme: 1028,1053,1110
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. (2018). On the similarity and apparent cycles of isotopic variations in East Antarctic snow pits (Vol. 12).
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. (2018). Sensitivity of the current Antarctic surface mass balance to sea surface conditions using MAR (Vol. 12).
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. (2019). (Vol. 13). Bachelor's thesis, , .
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. (2017). (Vol. 11).
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. (2019). Marked decrease in the near-surface snow density retrieved by AMSR-E satellite at Dome C, Antarctica, between 2002 and 2011 (Vol. 13).
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Ghislain Picard, Laurent Arnaud, Romain Caneill, Eric Lefebvre, Maxim Lamare. (2019). Observation of the process of snow accumulation on the Antarctic Plateau by time lapse laser scanning (Vol. 13).
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