Back to the future: Greenland's contribution to sea-level change

Abstract

The Greenland Ice Sheet is presently making a signifi cant contribution to global sea-level rise. Predictions for the future suggest that this will continue and likely accelerate during the remainder of this century. However, a comprehensive understanding of ongoing mass balance fl ux has only become possible in the last decade or so, following the development of satellite and other new observational technologies. As a result, it is not clear whether the patterns observed today are typical of the past or not. In this paper, I review predictions for Greenland’s contribution to future sea-level rise and then place these estimates in the context of the evidence for change during the twentieth century, the last few millennia, and the Eemian interglacial. There is evidence that the ice sheet responds sensitively to changes in conditions in the adjacent North Atlantic, leading to a hypothesis that annual and decadal fl uctuations in Atlantic air and sea surface temperatures shape the ice sheet’s contribution to global sea-level change. The recent loss of ice needs also to be seen in the context of an overall increase in ice sheet size and the related advance of the ice sheet margin by tens of kilometers during the past few millennia. I conclude by arguing that in order to better constrain the role of the Greenland Ice Sheet in future sea level, improvements in our understanding of present-day change in the ice sheet must be matched by equal strides in understanding how the ice sheet evolved in the past.