LATE WEICHSELIAN ICE-SHEET SENSITIVITY OVER FRANZ-JOSEF-LAND, RUSSIAN HIGH ARCTIC, FROM NUMERICAL MODELING EXPERIMENTS

A numerical ice-sheet model was run in order to produce reconstructions of the Late Weichselian ice coverage of Franz Josef Land, Russian High Arctic. The model grid covers the archipelago and surrounding shelf, but does not include the whole Barents-Kara region or the extensive ice cover that may have built up there. One experiment, where rates of iceberg calving at the grounded margin were curtailed because of the assumed presence of permanent thick sea ice, yielded a single 1.8 km-thick ice dome which covered the entire archipelago and surrounding sea. If, however, iceberg calving were included in the model's environmental input, the extent of the ice sheet would be limited to the periphery of the archipelago. If a large ice sheet existed over Franz Josef Land, the deglaciation of the islands may have been linked to the decay of the adjacent Barents-Kara Sea Ice Sheet, permitting iceberg calving (enhanced by relative sea-level rise) to occur. The introduction of a water-depth-related iceberg calving function at 15 000 yr ago forced an initial rapid rate of ice-sheet decay of 30 000 km(3) 1000 yr(-1). However, as the ice sheet thinned, and isostatic rebound began, the calculated rate of iceberg calving was reduced such that ice remained over the archipelago at 8000 yr ago. The model's failure to simulate complete ice-sheet decay by 8000 yr ago is at variance with radiocarbon-dated raised terraces on Franz Josef Land, which indicates the complete deglaciation of the islands at this time.