Spatial and temporal variability of snow chemical composition and accumulation rate at Talos Dome site (East Antarctica)

摘要

Five snow pits and five firn cores were sampled during the 2003-2004 Italian Antarctic Campaign at Talos Dome (East Antarctica), where a deep ice core (TALDICE, TALos Dome Ice CorE, 1650 m depth) was drilled in 2005-2008 and analyzed for ionic content Particular attention is spent in applying decontamination procedures to the firn cores, as core sections were stored for approximately 10 years before analysis. By considering the snow pit samples to be unperturbed, the comparison with firn core samples from the same location shows that ammonium, nitrate and MSA are affected by storage post-depositional losses. All the other measured ions are confirmed to be irreversibly deposited in the snow layer. The removal of the most external layers (few centimeters) from the firn core sections is proved to be an effective decontamination procedure. High-resolution profiles of seasonal markers (nitrate, sulfate and MSA) allow a reliable stratigraphic dating and a seasonal characterization of the samples. The calculated mean accumulation-rate values range from 70 to 85 mm w.e. year~(-1) in the period 2003-1973 with small differences between two sectors: 70-74 mm w.e. year~(-1) in the NNE sector (spanning 2003-1996 years) and 81-92 mm w.e. year~(-1) in the SSW sector (spanning 2003-1980 years). This evidence is interpreted as a coupled effect of wind-driven redistribution processes in accumulation/ablation areas. Statistical treatment applied to the concentration values of the snow pits and firn cores samples collected in different points reveals a larger temporal variability than spatial one both in terms of concentration of chemical markers and annual accumulation. The low spatial variability of the accumulation rate and chemical composition measured in the five sites demonstrates that the TALDICE ice core paleo-environmental and paleo-climatic stratigraphies can be considered as reliably representative for the Talos Dome area.