Tipping point reached in melting of Greenland’s peripheral glaciers

Greenland’s peripheral glaciers and ice caps (GICs) represent 12% of the world’s glacierized area outside of the Antarctic and Greenland ice sheets. Greenland’s GICs account for 14-20% of total current Greenland glacial mass loss. In a recent study a novel analytic procedure was used to quantify Greenland’s GICs mass loss. The data set includes precipitation, sublimation, melt, refreezing and runoff for all GICs on a daily time scale from 1958–2015 and uses the Greenland Ice Mapping Project (GIMP) Digital Elevation Model (DEM) for ice surface topography.  The analysis reveals unambiguously that the decreasing trend in the GIC ice balance is almost exclusively driven by increased runoff while precipitation remains constant. A similar pattern is seen for the Greenland Ice Sheet where the downward trend in ice volume is dominated by an increase in runoff. But the analysis reveals a striking difference in the response of the Greenland Ice Sheet and Greenland’s GICs to atmospheric warming. On the Greenland Ice Sheet over 20% of the meltwater produced since 1997 has been retained as a result of increased refreezing. In contrast on Greenland’s GICs refreezing decreased. The mass balance of Greenland’s GICs crossed a tipping point in 1997, after which a rapid deterioration in the capacity of the GICs to refreeze meltwater resulted in runoff increasing 65% faster than meltwater production accelerating ice loss. A tipping point in refreezing accelerates mass loss of Greenland’s glaciers and ice caps, B. Noël et al., Nature Communications 8, 14730 (2017), doi:10.1038/ncomms14730, Published online:31 March 2017