Reconstruction of the 1979-2006 Greenland ice sheet surface mass balance using the regional climate model MAR

Results from a 28-year simulation (1979 2006) over the Greenland ice sheet (GrIS) reveal an increase of solid precipitation (+ 0.4 +/- 2.5 km(3) yr(-2)) and runoff (+ 7.9 +/- 3.3 km(3) yr(-2)) of surface meltwater. The net effect of these competing factors is a significant Surface Mass Balance (SMB) loss of -7.2 +/- 5.1 km(3) yr(-2). The contribution of changes in the net water vapour flux (+ 0.02 +/- 0.09 km(3) yr(-2)) and rainfall (+ 0.2 +/- 0.2 km(3) yr(-2)) to the SMB variability is negligible. The meltwater supply has increased because the GrIS surface has been warming up + 2.4 degrees C since 1979. Sensible heat flux, latent heat flux and net solar radiation have not varied significantly over the last three decades. However, the simulated downward infrared flux has increased by 9.3 Wm(-2) since 1979. The natural climate variability (e. g. the North Atlantic Oscillation) does not explain these changes. The recent global warming, due to the greenhouse gas concentration increase induced by human activities, could be a cause of these changes. The doubling of surface meltwater flux into the ocean over the period 1979-2006 suggests that the overall ice sheet mass balance has been increasingly negative, given the likely meltwater-induced acceleration of outlet glaciers. This study suggests that increased melting overshadows over an increased accumulation in a warming scenario and that the GrIS is likely to keep losing mass in the future. An enduring GrIS melting will probably affect in the future an certain effect on the stability of the thermohaline circulation and the global sea level rise.