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

Based on ground-penetrating radar profiles, we analyze area-wide spatial and temporal characteristics of accumulation rate in the vicinity of the EPICA (European Project for Ice Coring in Antarctica) deep-drilling site in Dronning Maud Land, Antarctica (EDML). An area of 1600 km(2) is covered by 500 km of radar profiles, organized in a star-like pattern with eight 20-25 km legs and a 10 km grid with 1-3 km spacing, each pattern being centred on the EDML drilling location. Distributions of density, cumulative mass, age and the electromagnetic wave speed with depth are available from physical ice-core records. Nine,internal reflection horizons are continuously tracked within the upper 110 m of ice over the whole area, yielding a spatial picture of accumulation rate history over > 1000 years. The mean accumulation rate over the last 153 years varies between 50 and 75 kg m(-2) a(-1) over 50 km perpendicular to the ice divide; the spatial average is similar to 61 kg m(-2) a(-1). This general pattern is overlain by small-scale variations of accumulation rate on the order of 10% of the mean. Maximum local gradients in accumulation rate are similar to 2-3 kg m(-2) a(-1) km-', about five times the regional accumulation rate gradient. Comparison of topography and accumulation rate along a 20 km profile in the direction of the mean winds indicates that variations in accumulation rate over short distances are linked to surface undulations. Our results show that advected spatial variations of accumulation rate are on the same order and even exceed temporal changes over the investigated periods. Ice flow and upstream effects therefore might influence accumulation rates reconstructed from the EDML ice core.