The contribution of the Greenland and West Antarctic ice sheets to sea level has increased in recent decades, largely owing to the thinning and retreat of outlet glaciers and ice streams. This dynamic loss is a serious concern, with some modelling studies suggesting that the collapse of a major ice sheet could be imminent or potentially underway in West Antarctica, but others predicting a more limited response.
Researchers say that the Greenland ice sheet is quickly losing the ability to hinder sea level rise despite being known as a sponge for glacier meltwater.
The Greenland Ice Sheet has lost about 9,013 gigatonnes of water ice from 1900 to 2010 – and it’s dropping mass today at an increasing rate, an international team of scientists say.
The response of the Greenland Ice Sheet (GIS) to changes in temperature during the twentieth century remains contentious1, largely owing to difficulties in estimating the spatial and temporal distribution of ice mass changes before 1992, when Greenland-wide observations first became available2. The only previous estimates of change during the twentieth century are based on empirical modelling3, 4, 5 and energy balance modelling6, 7.
Greenland's glaciers are retreating quickly, and a new study shows in historical terms just how quickly: over the past century, at least twice as fast as any other time in the past 9,500 years.
Small glaciers and ice caps respond rapidly to climate variations, and records of their past extent provide information on the natural envelope of past climate variability. Millennial-scale trends in Holocene glacier size are well documented and correspond with changes in Northern Hemisphere summer insolation.
Whether or not an increase in meltwater will make ice sheets move more quickly has been contentious, because water lubricates the ice–rock interface and speeds up the ice, but also stimulates the development of efficient drainage; now, a long-term and large-area study of a land-terminating margin of the Greenland Ice Sheet finds that more meltwater does not equal higher velocity.
