A previously stable region of the Greenland ice sheet is found to be undergoing dynamic thinning - mass loss caused by meltwater runoff - due to regional warming, as reported in an article published online in Nature Climate Change. These findings suggest that Greenland’s contribution to sea-level rise was previously underestimated and needs to be accounted for in future projections.
The Greenland ice sheet, and particularly glaciers in the southeast and northwest, has been a significant contributor to global sea-level rise over the past 20 years. However, the northeast ice stream, which drains 16% of the ice sheet, was not thought to contribute.
Shfaqat Khan and colleagues use surface elevation measurements of the entire Greenland ice sheet over the period 1978-2012 to estimate changes in ice thickness near the coast. They find that the northeast ice stream was stable until around 2003, when increased air temperatures caused dynamic thinning to commence. Reduced sea ice at the outlet where the glacier meets the ocean, due to warm summers during 2002-2004, allowed icebergs to break off causing the ice stream to accelerate towards the sea. The team found that the northeast Greenland ice stream basin has been losing more than 10 gigatonnes of ice mass per year since 2006, and this is expected to continue in the near future due to the steady increase in glacier speed and ice loss.