Characteristics of accumulation in the vicinity of the EPICA deep-drilling site in Dronning Maud Land, Antarctica

摘要

Spatial-temporal characteristics of accumulation in the vicinity of the EPICA deep-drilling site in Dronning Maud Land, AntarcticaOlaf Eisen, Wolfgang Rack, Uwe Nixdorf, Frank WilhelmsBased on area-wide patterns of ice-penetrating radar profiles, we analyse the spatial and temporal characteristics of accumulation in the vicinity of the EPICA deep-drilling site in Dronning Maud Land, Antarctica (EDML).An area of 1600 km^2 is covered by 500 km of profiles, organized in a star-like pattern with nine 25 km legs and a 10 km grid with 1 km spacing.Distributions of density, cumulative mass, age and the electromagnetic wave speed are available from physical measurements along the EDML ice core, on which the radar-profile patterns are centered.Nine internal reflection horizons are continuously tracked within the upper 110 m of ice over the whole area, yielding a spatial picture of accumulation history of more than 1000 a.The mean accumulation over the last 160 a varies between 50 and 75 kg/m^2/a^1 over 50 km perpendicular to the ice divide, the spatial average is around 61 kg/m^2/a^1.This general pattern is overlain by small-scale variations of accumulation on the order of 10% of the mean.Maximum local gradients in accumulation are around 2-3 kg/m^2/a^-1 per km, about five times the regional accumulation gradient.Comparison of topography and accumulation along a 20 km profile parallel to the mean wind direction indicates that variations in accumulation are linked to surface undulations.The accumulation pattern has been stationary over the last millenium.It scales, however, with temporal variations of the mean precipitation on the order of 5 to 10% over several centuries.The EDML drilling site is located in an area of strong accumulation gradients, with a south-bound toung of higher accumulation, about 4 km wide, upstream towards the east.As spatial variations of accumulation exceed temporal changes over the investigated periods, the reconstruction of accumulation rates from the EDML ice core has to take into account advection and upstream effects in this region.