Study of Dome C site (East Antarctica) variability from the comparison of chemical stratigraphies.

This paper compares chemical stratigraphies from snowpits collected at Dome C (East Antarctica) in order to assess site variability in terms of spatial distribution of chemical markers, annual accumulation rate and chemical species persistence in the snow layers. Since Dome C was chosen for deep drilling down to the bedrock in the framework of EPICA (European Project for Ice Coring in Antarctica), to provide 800 kyr of climatic and environmental records, evaluating site variability is fundamental for a reliable interpretation of the deep ice core stratigraphies. For this purpose, 4 snowpits were dug at Dome C (1997/98. 1998/99, 2000/01 and 2005/06 Antarctic Campaigns) and analysed for cations, inorganic anions and methane sulphonate by ion chromatography. Unlike the first three snowpits, the most recent one was analysed directly in situ, allowing to observe that no chemical contamination or loss due to sample storage and transport to Europe occurs for such a sampling. Accumulation rate variability was revealed to be around 4% in a common time range (1992-1964) for all snowpits. Intra-snowpit chemical variability was definitely higher than inter-snowpit variability, indicating that the variations observed in the chemical stratigraphies from Dome C can be reliably related to effective changes in source and transport mechanisms of the investigated markers more than to site variability. Post-depositional phenomena affecting chloride, nitrate and methane sulphonate were studied, revealing a logarithmic decay as a function of depth for Cl(-) and MSA and an exponential one for NO(3)(-). The relative losses were quantified in the 75-80% range for Cl(-), 66-83% for MSA and 89-94% for NO(3)(-) and were found to stop around 320, 320 and 60-80 cm depth, respectively. (C) 2008 Elsevier B.V. All rights reserved.