Articles | Volume 11, issue 5
The Cryosphere, 11, 2345–2361, 2017
The Cryosphere, 11, 2345–2361, 2017

Research article 20 Oct 2017

Research article | 20 Oct 2017

The influence of the synoptic regime on stable water isotopes in precipitation at Dome C, East Antarctica

Elisabeth Schlosser1,2, Anna Dittmann1, Barbara Stenni3, Jordan G. Powers4, Kevin W. Manning4, Valérie Masson-Delmotte5, Mauro Valt6, Anselmo Cagnati6, Paolo Grigioni7, and Claudio Scarchilli7 Elisabeth Schlosser et al.
  • 1Inst. of Atmospheric and Cryospheric Sciences, University of Innsbruck, Innsbruck, Austria
  • 2Austrian Polar Research Institute, Vienna, Austria
  • 3Department of Environmental Sciences, Informatics and Statistics, Ca 'Foscari University of Venice, Venice, Italy
  • 4National Center for Atmospheric Research, Boulder, CO, USA
  • 5Laboratoire des Sciences du Climate et de l'Environnement, Gif-sur-Yvette, France
  • 6ARPA Center of Avalanches, Arabba, Italy
  • 7Laboratory for Observations and Analyses of the Earth and Climate, ENEA, Rome, Italy

Abstract. The correct derivation of paleotemperatures from ice cores requires exact knowledge of all processes involved before and after the deposition of snow and the subsequent formation of ice. At the Antarctic deep ice core drilling site Dome C, a unique data set of daily precipitation amount, type, and stable water isotope ratios is available that enables us to study in detail atmospheric processes that influence the stable water isotope ratio of precipitation. Meteorological data from both automatic weather station and a mesoscale atmospheric model were used to investigate how different atmospheric flow patterns determine the precipitation parameters. A classification of synoptic situations that cause precipitation at Dome C was established and, together with back-trajectory calculations, was utilized to estimate moisture source areas. With the resulting source area conditions (wind speed, sea surface temperature, and relative humidity) as input, the precipitation stable isotopic composition was modeled using the so-called Mixed Cloud Isotope Model (MCIM). The model generally underestimates the depletion of 18O in precipitation, which was not improved by using condensation temperature rather than inversion temperature. Contrary to the assumption widely used in ice core studies, a more northern moisture source does not necessarily mean stronger isotopic fractionation. This is due to the fact that snowfall events at Dome C are often associated with warm air advection due to amplification of planetary waves, which considerably increases the site temperature and thus reduces the temperature difference between source area and deposition site. In addition, no correlation was found between relative humidity at the moisture source and the deuterium excess in precipitation. The significant difference in the isotopic signal of hoarfrost and diamond dust was shown to disappear after removal of seasonality. This study confirms the results of an earlier study carried out at Dome Fuji with a shorter data set using the same methods.

Short summary
To derive paleotemperatures from ice cores we must know all processes involved in ice formation. At the Antarctic base Dome C, a unique precipitation data set plus stable water isotope data enabled us to study atmospheric processes influencing isotope ratios of precipitation in detail. Meteorological data from both automatic weather station and an atmospheric model were used to investigate how different atmospheric flow patterns determine the precipitation parameters used in paleoclimatology.