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

Alexandra Touzeau (1, 2) , Amaëlle Landais (1, 2) , Barbara Stenni (3) , Ryu Uemura (4) , Kotaro Fukui (5) , Shuji Fujita (6, 7) , Sarah Guilbaud (8) , Alexey Ekaykin (9, 10) , Mathieu Casado (1) , Eugeni Barkan (11) , Boaz Luz (11) , Olivier Magand (12) , Grégory Teste (12) , Emmanuel Le Meur (12) , Mélanie Baroni (13) , Joël Savarino (12) , Ilann Bourgeois (12, 13) , Camille Risi (14)

1 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
2 GLACCIOS - Glaces et Continents, Climats et Isotopes Stables
3 DAIS - Departemanto di Scienze Ambientali Informatica e Statistica
4 University of the Ryukyus [Okinawa]
5 Tateyama Caldera Sabo Museum
6 SOKENDAI - Graduate University for Advanced Studies [Hayama]
7 NiPR - National Institute of Polar Research [Tokyo]
8 LPCA - Laboratoire de Physico-Chimie de l'Atmosphère
9 Saint Petersburg State Technical University
10 AARI - Arctic and Antarctic Research Institute
11 The Institute of Earth Sciences
12 LGGE - Laboratoire de glaciologie et géophysique de l'environnement
13 LECA - Laboratoire d'Ecologie Alpine
14 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)

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 17 O-excess) are related to δ 18 O and how they are controlled. d-excess increases in the interior of the continent (i.e., when δ 18 O decreases), due to the distillation process, whereas 17 O-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 Vos-tok, as well as in surface snow at Dome C. We note that the slope of the δ 18 O 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 Published by Copernicus Publications on behalf of the European Geosciences Union. 838 A. Touzeau et al.: Acquisition of isotopic composition for surface snow in East Antarctica 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 δ 18 O and second-order parameters are also found in the snow from four snow pits. While the d-excess remains opposed to δ 18 O in most snow pits, the 17 O-excess is no longer positively correlated to δ 18 O and even shows anti-correlation to δ 18 O at Vostok. This may be due to a strato-spheric influence at this site and/or to post-deposition processes .

Domaines: Glaciologie; Climatologie

Alexandra Touzeau, Amaëlle Landais, Barbara Stenni, Ryu Uemura, Kotaro Fukui, et al.. Acquisition of isotopic composition for surface snow in East Antarctica and the links to climatic parameters. The Cryosphere, 2016, 10 (2), pp.837-852. ⟨10.5194/tc-10-837-2016⟩. ⟨insu-01388903⟩