SEASONAL-VARIATION OF ICE ABLATION AT THE MARGIN OF THE GREENLAND ICE-SHEET AND ITS SENSITIVITY TO CLIMATE-CHANGE, QAMANARSSUP-SERMIA, WEST GREENLAND

Monthly ice ablation was measured at the margin of the Greenland ice sheet for June, July and August over 7 years (1980-86). The total winter ablation (September-May) has also been measured, and a simple ablation-temperature model used to assign ablation values to individual months. Under the present climate, the most ablation occurred in June-August (on average 81% of annual ablation), moderate ablation took place in May and September (17%) and very little ablation occurred in October-April (2%). The effect of climate change on ice ablation is simulated using the ablation model to recalculate ablation for higher temperatures. Summer ice ablation increases with temperature in the model, but there is proportionally greater increase for May and September, whereas the period from October to April is presently so cold that even a temperature rise of +5-degrees-C will hardly increase ablation. The difference in annual ice ablation caused by future climate change will therefore depend upon the seasonal distribution of the temperature change. Changes in precipitation and accumulation will further modify the seasonal variation of ablation.