Archival of the water stable isotope signal in East Antarctic ice cores
Mathieu Casado1,2, Amaelle Landais1, Ghislain Picard3, Thomas Münch4,5, Thomas Laepple4, Barbara Stenni6, Giuliano Dreossi6, Alexey Ekaykin7, Laurent Arnaud3, Christophe Genthon3, Alexandra Touzeau1, Valérie Masson-Delmotte1, and Jean Jouzel11Laboratoire des Sciences du Climat et de l'Environnement – IPSL, UMR8212, CEA-CNRS-UVSQ, Gif sur Yvette, France 2Université Grenoble Alpes/CNRS, LIPHY, F-38000 Grenoble, France 3Université Grenoble Alpes/CNRS, LGGE, 38400 Grenoble, France 4Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Telegrafenberg A43, 14473 Potsdam, Germany 5Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany 6DAIS, Ca'Foscari University of Venice, Venice, Italy 7Arctic and Antarctic Research Institute, St. Petersburg, Russia
Received: 11 Nov 2016 – Accepted for review: 17 Nov 2016 – Discussion started: 17 Nov 2016
Abstract. The oldest ice core records are obtained from the East Antarctic plateau. Water stable isotopes records are key for reconstructions of past climatic conditions both over the ice sheet and at the evaporation source. The accuracy of such climate reconstructions crucially depends on the knowledge of all the processes affecting the water vapour, precipitation and snow isotopic composition. Atmospheric fractionation processes are well understood and can be integrated in Rayleigh distillation and complex isotope enabled climate models. However, a comprehensive quantitative understanding of processes potentially altering the snow isotopic composition after the deposition is still missing, especially for exchanges between vapour and snow. In low accumulation sites such as found on the East Antarctic Plateau, these poorly constrained processes are especially likely to play a significant role. This limits the interpretation of isotopic composition from ice core records, specifically at short time scales.
Here, we combine observations of isotopic composition in the vapour, the precipitation, the surface snow and the buried snow from various sites of the East Antarctic Plateau. At the seasonal scale, we highlight a significant impact of metamorphism on surface snow isotopic signal compared to the initial precipitation isotopic signal. In particular, in summer, exchanges of water molecules between vapour and snow are driven by the sublimation/condensation cycles at the diurnal scale. Using highly resolved isotopic composition profiles from pits in five East Antarctic sites, we identify a common 20 cm cycle which cannot be attributed to the seasonal variability of precipitation. Altogether, the smaller range of isotopic compositions observed in the buried and in the surface snow compared to the precipitation, and also the reduced slope between surface snow isotopic composition and temperature compared to precipitation, constitute evidences of post-deposition processes affecting the variability of the isotopic composition in the snow pack. To reproduce these processes in snow-models is crucial to understand the link between snow isotopic composition and climatic conditions and to improve the interpretation of isotopic composition as a paleoclimate proxy.
Casado, M., Landais, A., Picard, G., Münch, T., Laepple, T., Stenni, B., Dreossi, G., Ekaykin, A., Arnaud, L., Genthon, C., Touzeau, A., Masson-Delmotte, V., and Jouzel, J.: Archival of the water stable isotope signal in East Antarctic ice cores, The Cryosphere Discuss., doi:10.5194/tc-2016-263, in review, 2016.