Science Source

A tipping point in refreezing accelerates mass loss of Greenland’s glaciers and ice caps

States that melting of the Greenland ice sheet (GrIS) and its peripheral glaciers and ice caps (GICs) contributes about 43% to contemporary sea level rise
States that, while patterns of GrIS mass loss are well studied, the spatial and temporal evolution of GICs mass loss and the acting processes have remained unclear
Examines data set including individual surface mass balance components (precipitation, sublimation, melt, refreezing and runoff) for all GICs on a daily time scale (1958–2015)
Identifies 1997 (±5 years) as a tipping point for the rates of gain and loss of ice from GICs
Finds that that year marks the onset of a rapid deterioration in the capacity of the GICs firn (granular snow that has not yet been compressed into ice) to refreeze meltwater, causing long-term mass loss
Finds that consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 mass loss
Concludes that, in contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now
Results underline the very different responses of the GICs and GrIS to atmospheric warming