Increasing Freshwater Fluxes from the Greenland Ice Sheet Observed from Space

With a potential sea level contribution of 7.4 m (Morlighem et al., 2017), the Greenland Ice Sheet is by far the largest freshwater reservoir in the Northern Hemisphere. In addition to precipitation that nourishes the ice sheet throughout the year, summer above-freezing temperatures cause surface melt. Part of the meltwater refreezes in the snowpack, but a considerable part runs off to the ocean. The difference between precipitation and runoff is referred to as the surface mass balance (SMB). Typically, when averaged over a year, snowfall exceeds runoff, resulting in accumulation of mass on the ice sheet. This mass gain is counteracted by the slow but steady flow of glacier that transports ice toward the margins of the ice sheet and eventually to the ocean, where it either melts or calves as icebergs.