Greenlandâ€™s contribution to global sea level has soared in the past two decades. An important new study finds that the massive northeastern part of the ice sheet, previously thought to be stable, has begun shedding ice. If this trend continues â€” and researchers say â€œa self-perpetuating feedback process may have been triggeredâ€ â€” actual sea level rise this century will likely be higher than many current models had projected.
Covering 660,000 square miles â€” roughly 80 percent of the country â€” Greenlandâ€™s ice sheet is second only in size to Antarcticaâ€™s. Scientists estimate that melting from the ice sheet as a whole has accounted for about 16 percent of sea level rise every year for the last two decades.
Research had also long suggested the northeastern portion of the ice sheet was stable. As a result, it was largely left out of the models used to anticipate future sea level rise.
But the new study, â€œSustained mass loss of the northeast Greenland ice sheet triggered by regional warming,â€ published in Nature Climate Change (subs. reqâ€™d), suggests the northeastern portion began melting rapidly around 2003. And after first jumping from an ice loss rate of zero to about 10 billion metric tons per year, itâ€™s now approaching 15 or 20 billion metric tons per year and may well keep accelerating.
â€œMost projections of the future behaviour of the ice sheet have no, or little, contribution from this part of Greenland,â€ said Professor Jeremy Bamber of Bristol University, a co-author of the study. â€œBut these new results suggest that this region is sensitive to changes in climate and has the potential to contribute significantly now and in the future.â€
The team arrived at their conclusion using a combination of surface elevation data from airplanes and four different satellites, along with a GPS-linked network of 50 stations located along the coast of Greenlandâ€™s ice sheet. The overall collection of data spanned 1978 to 2012 and was used to essentially weigh the ice sheetâ€™s mass.
Specifically, the study suggests a series of particularly warm summers leading up to 2003 â€” bringing higher temperatures in both the atmosphere and the surrounding ocean â€” triggered the speed up in melting.