The effect of ice-sheet thickness change on the accumulation history inferred from GISP2 layer thicknesses

Accumulation-rate histories inferred from GISP2 layer-thickness data using both a constant- and a variable-thickness model are compared. The variable-thickness model predicts accumulation rates about 25% lower than the constant-thickness model. Results also indicate that high-frequency changes in accumulation rates are consistent with earlier analyses. However, sensitivity tests indicate that the accumulation-rate history cannot be precisely determined. This analysis defines an envelope of likely accumulation histories bounded above by the accumulation history inferred by the constant-thickness model. Predictions become increasingly uncertain for old ice because of 1) intrinsic difficulties associated with this inverse problem, and 2) decreased accuracy of the data. -from Authors