Nanna B Karlsson, Anne M. Solgaard, Kenneth D. Mankoff, Jason E Box, Michele Citterio, William T. Colgan, Signe H. Larsen, Kristian Kjellerup Kjeldsen, Niels J. Korsgaard, Douglas I. Benn

The Greenland ice sheet is one of the largest sources of sea-level rise since the early 2000s. Basal melt has not been included explicitly in assessments of ice-sheet mass loss so far. Here, we present the first full-coverage estimate of the ice-sheet wide basal melt in Greenland and its recent change through time. We find that presently basal melting contributes at least 22.3 +5/-3 Gt per year to the total mass loss, and we estimate that basal melting has increased by at least 2.3 +/-0.8 Gt (or 12%) since 2000. The basal melt discharge from Sermeq Kujalleq (Jakobshavn Isbræ) has increased by 24 % in the same period. As the Arctic warms, basal melt will likely continue to increase thus aggravating current mass loss trends, enhancing solid ice discharge and modifying fjord circulation.