Spatial gradients in snow layering and 10 m temperatures at two EPICA-Dronning Maud Land (Antarctica) pre-site-survey drill sites

Abstract

During the 1997/98 field season, Sweden, Norway and The Netherlands performed a pre-site survey for EPICA in Dronning Maud Land, Antarctica. This paper summarizes the results and pays special attention to the high spatial gradients found in snow layering and temperatures. The sites were 'Camp Victoria' (CV) on Amundsenisen (76°S, 8°W; 2400 m a.s.l.), approximately 550 km from the coast, and 'Camp Maudheimvidda' (CM) on Maudheimvidda (74°S, 13°W; 362 m a.s.l.), some 140 km from the coast. The drilling programme included both medium-long firn/ice cores and shallow firm cores. These were analysed by means of δ18 O, DEP, ECM, β activity, density, and ion content. The combined results suggests a mean annual accumulation rate of 60 mm.w.e. for CV and 220 mm.w.e. for CM. Variability measurements of spatial snow layering were performed at two scales; over tens of kilometres by radar and over a few metres by pits and high-resolution radar soundings. Results, as measured by relative standard deviation, were typically 10% on the polar plateau and as high as 50% near the coast. The 10 m temperature measurements were-38.5°C (std dev. = 0.5°) for CV and -17.6°C (std dev. = 0.15°) for CM. Snow chemistry was sampled at each medium-long-core drill site. Comparison of δ18 O profiles from snow pits and the uppermost part of the CV medium-long core showed large variations. Mean δ18 O values over 2 m profiles varied between 41.6‰ and 39.7‰ within a horizontal distance of 50 m.