Past Changes in Precipitation Rate and Ice Thickness as Derived from Age — Depth Profiles in Ice-Sheets; Application to Greenland and Canadian Arctic Ice Core Records

Abstract

A simple non-steady-state ice dynamic model is presented that allows accumulation rate and ice thickness histories to be calculated from age — depth profiles in ice-sheets. Past accumulation rate and ice thickness histories of the Greenland ice-sheet and Devon Island ice-cap, Arctic Canada as derived by means of this model are discussed. The model calculations indicate substantially reduced ice thicknesses for Devon Island ice-cap in the Holocene climatic optimum. For the Greenland ice-sheet, calculations based on the time scales proposed by Dansgaard et al. (1982) for the Camp Century and Dye3 deep ice cores indicate, that accumulation rates may have been as low as a fourth to a fifth of the present values during the coldest periods of the last glacial. These values are significantly lower than estimates based on Camp Century deep ice core 10Be concentrations which suggest a reduction of the late glacial acccumulation rate only by a factor of about three as compared to the present value. The explanation of this discrepancy could be that, either 10Be is not as reliable an indicator of glacial/interglacial accumulation rate changes in Greenland as it seems to be in Antarctica, or the deeper section of the Camp Century ice-age record is younger than indicated by the time scale proposed by Dansgaard et al. (1982). Furthermore, the model calculations indicate that the ice-covers in Northwest and South Greenland were thin, or possibly absent, during a period in the last interglacial. This suggests that the mass wastage from the Greenland ice-sheet might have been substantial in this period, and that melting of the Greenland ice-sheet could account for a significant part, if not all, of the 6 m higher than present sea level in the Eemian interglacial.