The interpretation of climatic records from deep ice cores requires detailed modelingof the ice-dynamical history around the drill site. This is necessary to determine theorigin and age of the ice and to be able to correctly assess risk factors for stratigraphicdistortions. Of particular importance are the stability of the flow and deformationalpatterns as can be obtained from time-dependent reconstructions of the strain andthermal history along individual particle paths ending up at the drill site. A highresolutionreconstruction of the ice flow is however known to be restricted within thetraditional shallow-ice approximation by the ratio between ice thickness and modelresolution and because certain assumptions break down near to such key regions asice divides. We focus on a 600 x 400 km area around the EPICA drill site and havetherefore nested a higher-order ice-flow model within a large-scale three-dimensionaltime-dependent ice sheet model of the Antarctic ice sheet. The local model includesall stress gradients in the force balance and makes use of the most recent ice-thicknessand accumulation data on a 2.5 km grid. All prognostic calculations take place withinthe large-scale model, which is implemented on a 20 km grid. The fine-scale modelreceives boundary conditions from the large-scale model at lateral boundaries througha transition zone to eliminate the effects of different spatial resolution, but the localmodel does not couple back to the 3-D model. The nested model is run through the last4 glacial cycles. The presentation will focus on the methodology of the model nestingand discuss various results relevant for the interpretation of the EDML ice-core record.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL1-Processes and interactions in the polar climate system
Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL6-Earth climate variability since the Pliocene