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Spatial and temporal variability of accumulation at the EDML deep drilling site over the last millenium, derived from ice-penetrating radar

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Eisen, O. , Nixdorf, U. and Wilhelms, F. (2004): Spatial and temporal variability of accumulation at the EDML deep drilling site over the last millenium, derived from ice-penetrating radar , 1st EGU General Assembly, 26 - 30 April, Nice, France,. .
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Abstract:

The spatial and temporal variation of accumulation in the vicinity of the EPICA deep drilling site in Dronning Maud Land, Antarctica, (EDML) is investigated by analysis of shallow ice-penetrating radar data. Based on 500 km of radar profiles, forming a 10 km grid with 1 km spacing and a star-like pattern consisting of nine legs up to 25 km long, nine internal reflection horizons are continuously tracked. Depth distributions of electromagnetic wave speed, mass, and age are derived from dielectric-profilingdata of the EDML core. The horizons cover the upper 110 m of ice and yield the regional age-depth distribution, corresponding to around 1040 a of deposition history.The spatial pattern of accumulation shows a strong decreasing trend from north tosouth during all time intervals, roughly perpendicular to the ice divide. The accumulation, averaged over the last 140 a, decreases from 71 to 54 kg m-2 a−1 over a distance of 40 km, about 25% of the accumulation at EDML. The general pattern is overlain by small-scale variations of accumulation on the order of 510%, which are linked to surfaceundulations. Temporal variations of accumulation amount to ±10% over ~250a intervals, with the average accumulation being close to the present value. Despite temporal variations, the spatial distribution of dimensionless accumulation is found to be similar at all times. The data let us conclude that the general pattern has been stable over the last millenium and that spatial variations of accumulation caused bylocal effects might be larger than climate-induced temporal changes of precipitation.

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