Archival processes of the water stable isotope signal in East Antarctic ice cores
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Published:2018-05-24
Issue:5
Volume:12
Page:1745-1766
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ISSN:1994-0424
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Container-title:The Cryosphere
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language:en
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Short-container-title:The Cryosphere
Author:
Casado MathieuORCID, Landais Amaelle, Picard GhislainORCID, Münch ThomasORCID, Laepple ThomasORCID, Stenni BarbaraORCID, Dreossi Giuliano, Ekaykin AlexeyORCID, Arnaud Laurent, Genthon ChristopheORCID, Touzeau AlexandraORCID, Masson-Delmotte ValerieORCID, Jouzel Jean
Abstract
Abstract. The oldest ice core records are obtained from the East Antarctic
Plateau. Water isotopes are key proxies to reconstructing past climatic
conditions over the ice sheet and at the evaporation source. The accuracy of
climate reconstructions depends on knowledge of all processes affecting water
vapour, precipitation and snow isotopic compositions. Fractionation processes
are well understood and can be integrated in trajectory-based Rayleigh
distillation and isotope-enabled climate models. However, a quantitative
understanding of processes potentially altering snow isotopic composition
after deposition is still missing. In low-accumulation sites, such as those
found in East Antarctica, these poorly constrained processes are likely to
play a significant role and limit the interpretability of an ice core's
isotopic composition. By combining observations of isotopic composition in vapour, precipitation,
surface snow and buried snow from Dome C, a deep ice core site on the East
Antarctic Plateau, we found indications of a seasonal impact of
metamorphism on the surface snow isotopic signal when compared to the initial
precipitation. Particularly in summer, exchanges of water molecules between
vapour and snow are driven by the diurnal sublimation–condensation cycles.
Overall, we observe in between precipitation events modification of the
surface snow isotopic composition. Using high-resolution water isotopic
composition profiles from snow pits at five Antarctic sites with different
accumulation rates, we identified common patterns which cannot be attributed
to the seasonal variability of precipitation. These differences in the
precipitation, surface snow and buried snow isotopic composition provide
evidence of post-deposition processes affecting ice core records in low-accumulation areas.
Funder
European Research Council
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Water Science and Technology
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