EGU22-10188
https://doi.org/10.5194/egusphere-egu22-10188
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

What is driving the isotopic composition of surface snow in East Antarctica? - Insights from a multi-year time series of surface snow at Dome C

Alexandra Zuhr1,2,3, Amaëlle Landais1, Mathieu Casado1,2,4, Bénédicte Minster1, Frederic Prié1, Romilly Harris-Stuart1, Ghislain Picard5, Laurent Arnaud5, Marie Dumont6, Inès Ollivier5,7, and Thomas Laepple2,8
Alexandra Zuhr et al.
  • 1Laboratoire des Sciences du Climat et de l'Environnement, IPSL-CEA-CNRS-UVSQ- Paris Saclay, Gif sur Yvette, France
  • 2Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Forschungsstelle Potsdam, Germany (alexandra.zuhr@awi.de)
  • 3Institute for Geoscience, University of Potsdam, Potsdam, Germany
  • 4Geo- und Umweltforschungszentrum, Universität Tübingen, Tübingen, Germany
  • 5Institut des Geosciences de l’Environnement, Université Grenoble Alpes-CNRS, Grenoble, France
  • 6Université Grenoble Alpes, Université de Toulouse, Météo-France, Grenoble, France, CNRS, CNRM, Centre d’Etudes de la Neige, Grenoble, France
  • 7University of Bergen, Geophysical Institute and Bjerknes Centre for Climate Research, Bergen, Norway
  • 8University of Bremen, MARUM – Centre for Marine Environmental Sciences and Faculty of Geosciences, Bremen, Germany

The isotopic composition (d18O, dD) of surface snow on an ice sheet is primarily seen as a recorder of the air temperature and is used to reconstruct past climatic conditions from ice cores. The second order parameters d-excess and 17O-excess can preserve climatic signals from the moisture origin and are indicative for kinetic fractionation processes in the water cycle between the source and the deposition site. Fractionation is especially important for the surface snow which can exposed to the atmosphere for a long time during periods without snowfall. The resulting effect of this process on the isotopic composition and the second order parameters in the interior of Antarctica is, however, unclear. In order to better understand the contribution of secondary processes on the isotopic signature and to disentangle the climate characteristics at the moisture source region and at the ice core site, we study both the isotopic composition and the second order parameters of surface and subsurface snow at Dome C on the East Antarctic Plateau. For this, we make use of an extensive data set of isotopic data (d18O, dD, dexcess and 17O-excess) from surface (0 - 1.5 cm) and subsurface snow (1.5 - 4.5 cm) covering continuously the period from 2016 to 2020. This data set is complemented with previously published isotopic data of surface snow and precipitation data back to 2011. For additional comparisons and analyses, we use data from a nearby weather station, the ERA5 reanalysis data set, a satellite-derived grain index estimate and simulations from the detailed snowpack model CROCUS.

We observe a good (weak) correlation between the ambient temperature and the surface (subsurface) layer. Most years are characterised by a strong increase in the isotopic composition towards the summer and a gentle decrease towards winter while d-excess shows a contrary behaviour. We suggest that the strength of the summer increase is related to the amount of precipitation and the magnitude of metamorphism at the surface. The degree of metamorphism can (to some degree) be approximated from observational data (e.g. the grain index) or from model output (e.g. latent heat flux from CROCUS). In addition to presenting possible mechanisms leading to strong or weak increases in the isotopic composition in summer, we developed a simple model using temperature and snowfall data from ERA5 to analyse the contribution of temperature and other parameters to the observed isotopic signals.

How to cite: Zuhr, A., Landais, A., Casado, M., Minster, B., Prié, F., Harris-Stuart, R., Picard, G., Arnaud, L., Dumont, M., Ollivier, I., and Laepple, T.: What is driving the isotopic composition of surface snow in East Antarctica? - Insights from a multi-year time series of surface snow at Dome C, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10188, https://doi.org/10.5194/egusphere-egu22-10188, 2022.