Climate change and forest fires synergistically drive widespread melt events of the Greenland Ice Sheet

Tuesday, 16 December 2014: 4:00 PM
Kaitlin M Keegan, Niels Bohr Institute - University of Copenhagen, Copenhagen, Denmark, Mary R Albert, Dartmouth College, Thayer School of Engineering, Hanover, NH, United States, Joe McConnell, Desert Research Institute Reno, Reno, NV, United States and Ian Baker, Dartmouth College, Hanover, NH, United States
The Greenland ice sheet experiences melting at low elevations near the coastline annually. However, surface melt is rare over the dry snow region in its center. In July 2012, over 97% of the Greenland ice sheet experienced surface melt, the first widespread melt during the era of satellite remote sensing. It had been previously unknown when the ice sheet had experienced melt events of this magnitude, or what caused them. Here we show that the most recent previous widespread melt occurred in 1889, and demonstrate that warm temperatures combined with black carbon sediments from Northern Hemisphere forest fires reduced albedo below a critical threshold, permitting the melt events in both 1889 and 2012. Furthermore, we use these data to project the frequency of widespread melt into the year 2100. Since arctic temperatures and the frequency of forest fires are both expected to rise with climate change, our results suggest that widespread melt events on the ice sheet may begin to occur almost annually by the end of century.