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Age and origin of the ice in the EPICA DML ice core derived from a nested Antarctic ice sheet model

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Citation:
Huybrechts, P. , Rybak, O. , Pattyn, F. and Steinhage, D. (2004): Age and origin of the ice in the EPICA DML ice core derived from a nested Antarctic ice sheet model , European Geosciences Union First General Assembly, Nice (F)April 2004. .
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Abstract:

For a correct dating and interpretation of the EPICA DML ice core one needs to takeinto account the effects of horizontal advection. That is because the ice core is beingdrilled on a flank position, implying that the ice was not deposited locally. Thedeeper in the ice core, from the further and higher inland the climatic informationwas transported with the ice flow. A potentially complicating factor is that individualice particles may have encountered different strain and thermal regimes alongtheir respective trajectories as the ice sheet geometry changed during the total periodcovered by the ice core. We have addressed these issues with a comprehensive threedimensionalthermomechanical ice-sheet model of the Antarctic ice sheet nested witha detailed higher-order ice-flow model for the area around the drill site. The largescalemodel is based on the shallow ice approximation, considers coupling with an iceshelf and a variable grounding-line, and is implemented on a 20 km grid. The localmodel includes all stress gradients in the force balance and makes use of the mostrecent ice-thickness and accumulation data provided on a 2.5 km grid. The EDML icecore is dated by Lagrangian backtracing carried out by consecutive cubic spline interpolationof a particles location using the reversed 3D velocity field obtained fromforward experiments. This procedure fully accounts for time-dependent changes in icethickness, flow direction, flow velocity, accumulation rate, basal conditions, etc... Animportant output is the palaeo-location of the origin of individual particle paths. Thisinformation is needed to assess the temperature bias introduced by flow effects, whichneeds to be separated from the ice core record to extract the climatic information.

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