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Area-wide temporal characteristics of accumulation in the vicinity of the EPICA deep drilling site in Dronning Maud Land, Antarctica.

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Eisen, O. , Nixdorf, U. and Wilhelms, F. (2004): Area-wide temporal characteristics of accumulation in the vicinity of the EPICA deep drilling site in Dronning Maud Land, Antarctica. , SCAR Open Science Conference, 25-31 July 2004, Bremen, Germany. .
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Abstract:

Based on area-wide patterns of ice-penetratingradar profiles, we analyse the spatial andtemporal characteristics of accumulation in thevicinity of the EPICA deep-drilling site inDronning Maud Land, Antarctica (EDML).An area of 1600 km2 is covered by 500 km ofprofiles, organized in a star-like pattern withnine 25 km-legs and a 10 km-grid with 1 km spacing.Distributions of density, cumulative mass, ageand the electromagnetic wave speed are availablefrom physical measurements along the EDML ice core,on which the radar-profile patterns are centered.Nine internal reflection horizons are continuouslytracked within the upper 110 m of ice over thewhole area, yielding a four-dimensional picture ofaccumulation history of more than 1000 a.The mean accumulation over the last 160 a variesbetween 45 and 75 kg m-2 a-1over 50 km, perpendicular to the ice divide, the spatialaverage is around 63 kg m-2 a-1.This general pattern is overlain by small-scalevariations of accumulation on the order of 5%,which are linked to surface undulations.Maximum local gradients are around3 kg m-2 a-1 km-1,about ten times the regional accumulation gradient.The accumulation pattern has been stationaryover the last millenium. It scales, however,with temporal variations of the mean precipitationon the order of 5 to 10% over several centuries.The EDML drilling site is located in an area ofstrong accumulation gradients, with a south-boundtoung of higher accumulation, about 5 km wide,upstream towards the east. As spatial variationsof accumulation exceed temporal changes over theinvestigated period, the reconstruction ofaccumulation rates from ice cores has to takeinto account advection and upstream effectsin this region.

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