Friday, 7 December 2018

Nonlinear rise in Greenland runoff in response to post-industrial Arctic warming

Source: Nature, Naturevolume 564, pages104–108 (2018), 1st December 2018, https://doi.org/10.1038/s41586-018-0752-4

Authors: 

Luke D. Trusel
Department of Geology, Rowan University, Glassboro, NJ, USA
Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA

Sarah B. Das
Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA

Matthew B. Osman
Joint Program in Oceanography, Massachusetts Institute of Technology/Woods Hole Oceanographic Institution, Woods Hole, MA, USA

Matthew J. Evans
Department of Chemistry, Wheaton College, Norton, MA, USA

Ben E. Smith
Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA, USA

Xavier Fettweis
Department of Geography, University of Liège, Liège, Belgium

Joseph R. McConnell
Division of Hydrologic Sciences, Desert Research Institute, Reno, NV, USA

Brice P. Y. Noël
Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, Netherlands

Michiel R. van den Broeke
Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, Netherlands

Abstract:

The Greenland ice sheet (GrIS) is a growing contributor to global sea-level rise1, with recent ice mass loss dominated by surface meltwater runoff. Satellite observations reveal positive trends in GrIS surface melt extent, but melt variability, intensity and runoff remain uncertain before the satellite era. Here we present the first continuous, multi-century and observationally constrained record of GrIS surface melt intensity and runoff, revealing that the magnitude of recent GrIS melting is exceptional over at least the last 350 years. We develop this record through stratigraphic analysis of central west Greenland ice cores, and demonstrate that measurements of refrozen melt layers in percolation zone ice cores can be used to quantifiably, and reproducibly, reconstruct past melt rates. We show significant (P < 0.01) and spatially extensive correlations between these ice-core-derived melt records and modelled melt rates and satellite-derived melt duration across Greenland more broadly, enabling the reconstruction of past ice-sheet-scale surface melt intensity and runoff. We find that the initiation of increases in GrIS melting closely follow the onset of industrial-era Arctic warming in the mid-1800s, but that the magnitude of GrIS melting has only recently emerged beyond the range of natural variability. Owing to a nonlinear response of surface melting to increasing summer air temperatures, continued atmospheric warming will lead to rapid increases in GrIS runoff and sea-level contributions.

Read more at: https://www.nature.com/articles/s41586-018-0752-4#article-comments