Recent contributions of glaciers and ice caps to sea level rise

Glaciers and ice caps (GICs) are important contributors to present-day global mean sea level rise(1-4). Most previous global mass balance estimates for GICs rely on extrapolation of sparse mass balance measurements(1,2,4) representing only a small fraction of the GIC area, leaving their overall contribution to sea level rise unclear. Here we show that GICs, excluding the Greenland and Antarctic peripheral GICs, lost mass at a rate of 148 +/- 30 Gt yr(-1) from January 2003 to December 2010, contributing 0.41 +/- 0.08 mm yr(-1) to sea level rise. Our results are based on a global, simultaneous inversion of monthly GRACE-derived satellite gravity fields, from which we calculate the mass change over all ice-covered regions greater in area than 100 km(2). The GIC rate for 2003-2010 is about 30 per cent smaller than the previous mass balance estimate that most closely matches our study period(2). The high mountains of Asia, in particular, show a mass loss of only 4 +/- 20 Gt yr(-1) for 2003-2010, compared with 47-55 Gt yr(-1) in previously published estimates(2,5). For completeness, we also estimate that the Greenland and Antarctic ice sheets, including their peripheral GICs, contributed 1.06 +/- 0.19 mm yr(-1) to sea level rise over the same time period. The total contribution to sea level rise from all ice-covered regions is thus 1.48 +/- 0.26 mm yr(-1), which agrees well with independent estimates of sea level rise originating from land ice loss and other terrestrial sources(6).