Atmospheric signals and characteristics of accumulation in Dronning Maud Land, Antarctica

Abstract

With the planned European Programme for Ice Coring in Antarctica in Dronning Maud Land it is important to understand the processes leading to accumulation for successful interpretation of core data. Because it is impractical to obtain precipitation observations with a large spatial coverage and on a daily timescale in Antarctica, model-generated precipitation must be considered for a comprehensive study of the region. However, without observational data it is difficult to check the veracity of the model data. Precipitation data from the European Centre for Medium-Range Weather Forecasts reanalysis project shows that 89% of days have low (under 0.2 mm) precipitation resulting in 31% of the annual total. At the other extreme, less than 1% of days have high (over 1 mm) precipitation, which results in 20% of the annual total. It is reasoned that the changes in the frequency of extreme precipitation events could alter the trace record in ice cores and lead to a bias in reconstructed paleotemperatures. Case studies reveal that high-precipitation days have amplified upper level planetary waves directing warm moist air to the region. Associated with this is the presence of a cyclone in or at the northeast extreme of the Weddell Sea. Commonly, the longwaves provide a blocked anticyclone in the South Atlantic to form a dipolar channeling of the air mass. The accumulation variability is linked to the variability in the intensity of these storms and their tracks. It is seen that this is related to the El Niño-Southern Oscillation and a semiannual cycle. Copyright 1999 by the American Geophysical Union.