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Meteorological regime of central Antarctica and its role in the formation of isotope composition of snow thickness

Abstract : The main goals of the present study are, first, determination of the relationship between local air temperature and snow isotope composition at Vostok Station (East Antarctica) and, second, reconstruction of climatic variability in this area over the past 200 years. Experimental basis of the study includes data on isotope composition and accumulation rate of snow from 6 shallow and 2 deep snow pits dug in the Vostok's vicinities during summer seasons 1998/99, 1999/2000 and 2001/02. Meteorological regime is documented by the results of instrumental meteorological and balloon-sounding observations being carried out at Vostok since December 1957 and archived in Arctic and Antarctic Research Institute (St. Petersburg, Russia). We also used the data on snow accumulation at the stake network constructed near the station in 1970, documented spatial distribution of surface snow isotope composition and studied variations of isotope composition in precipitating and blowing snow collected from December 1999 to December 2000. By comparing meteorological and snow accumulation data, it has been established that most of precipitation in central Antarctica form under clear-sky conditions (diamond dust). Balloon-sounding data suggests that overall condensation temperature at Vostok does not significantly differ from the temperature at the top of the inversion layer. Temporal variability of isotope composition in a single point is dominated by influence of snow relief (micro-relief, "meso-dunes" and possibly mega-dunes), which substantially diminishes the signalto-noise ratio. Seasonal variations of isotope composition of the precipitation closely follow those of the local temperature, though the influence of moisture source is also evident from the intra-annual changes of deuterium excess content. Significant linear relationship is observed for the last 40 years between stacked series of snow isotope composition from pits and surface air temperature for the multi-decadal time-scale, while shorter (10-year) isotope variability is likely dominated by source conditions. During the past two centuries both snow accumulation and isotope composition of snow display oscillations with an apparent period of about 50 years. Relationship between these variations and the Pacific Decadal Oscillation index is suggested. If true, this would imply a climatic teleconnection of central East Antarctica with tropical Pacific. Finally, deuterium excess data suggest a sharp change in atmospheric circulation supplying Vostok area with moisture around 1963.
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Alexey Ekaykin. Meteorological regime of central Antarctica and its role in the formation of isotope composition of snow thickness. Glaciology. Faculté de géographie de Saint Pétersbourg, 2003. English. ⟨tel-00701466⟩

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