Mar 31, 2017

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

by
B. Noël, W. J van de Berg, S. Lhermitte, B. Wouters, H. Machguth, I. Howat, M. Citterio, G. Moholdt, J. T. M. Lenaerts, M. R. van den Broeke
,
Nature Communications
  • 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