Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling
28 August 2013

Negative 21st Century Mass Balance for the Greenland Ice Sheet


The surface mass balance (SMB) of a glacier or ice sheet is defined as the difference between accumulation (mainly snowfall) and ablation (mainly surface melting and runoff). As the climate warms, the SMB is expected to decrease because of increased summer melting. Two companion studies (Lipscomb et al. 2013, Vizcaíno et al. 2013) have described a new SMB scheme for ice sheets in the Community Earth System Model (CESM) and have validated the 20th century SMB simulation for Greenland.


Climate scientists in the Netherlands (Utrecht University) and the U.S. (Los Alamos National Laboratory and the National Center for Atmospheric Research) have used the Community Earth System Model (CESM) to project 21st century change in the surface mass balance (SMB) of the Greenland ice sheet.  This study presents results from CESM coupled climate simulations using the RCP8.5 high-emission forcing scenario. The SMB of the Greenland ice sheet decreases from 372 ± 100 Gt/yr in 1980-99 to -78 ± 143 Gt/yr in 2080-99. By the end of the 21st century, annual mean temperatures over the ice sheet increase by 4.7oC, compared to a global mean increase of 3.7oC. Northern Greenland warms considerably because of sea ice retreat, whereas warming is suppressed in southeast Greenland because of reduced ocean heat transport. The ablation area increases from 9% of the GIS in 1980-99 to 28% in 2080-99, and surface melt doubles, more than offsetting an 18% increase in snowfall.


CESM simulates a negative surface mass balance for the Greenland ice sheet by the end of this century. A negative SMB is significant because it implies long-term decay of the ice sheet, even in the absence of iceberg calving.

Siyu Chen

This work was supported by the Earth System Modeling program of the Office of Biological and Environmental Research within the US Department of Energy’s Office of Science.