Numerical age computation of the Antarctic ice sheet for dating deep ice coresB. MÜGGE, A. A. SAVVIN, R. CALOV and R. GREVE AbstractThe application of two different methods for the computation of the age of ice is discussed within the frame of numerical ice sheet modelling. The first method solves the purely advective equation for the age field in the Eulerian frame, which requires the addition of a numerical diffusion term to stabilize the solution and therefore produces arbitrary results in a near-basal boundary layer. The second method makes more efficient use of the simplicity of the equation in the Lagrangian frame by tracing particle paths in the flowing ice body, and it does without artificial diffusion. We compute the age field for the Antarctic ice sheet with both methods for a time-dependent simulation driven by a 242200 year surface temperature history derived from stable isotope data of the Vostok deep ice core, and discuss the differences of the age computation schemes. Emphasis is put on two regions: (i) western Dronning Maud Land (DML), where reconnaissance for a deep ice core within the European Project for Ice Coring in Antarctica (EPICA) is currently carried out, and (ii) the eastern part of central East Antarctica with the deep-ice-core locations Vostok and Dome C (the former completed, the latter currently drilled within EPICA). The Eulerian scheme provides good results except for the lower parts of the ice sheet where the numerical diffusion falsifies the computed ages. The particle-tracing scheme does not show this shortcoming; however, it yields ages generally somewhat too small because it does not yet account for the time-dependence of the ice flow. Advances in Cold-Region Thermal Engineering and Sciences (eds. K. Hutter, Y. Wang and H. Beer), pp. 307-318 (1999). Springer, Berlin, Germany etc. |
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