Increased Meltwater Refreezing in Southwest Greenland Ice Sheet Firn between 1989 and 2017

Authors: Asa Rennermalm*, Rutgers, The State University of New Jersey, Regine Hock, Univ of AK-Geophysical Inst, Marco Tedesco, Lamont Doherty Earth Observatory, Columbia University, Giovanni Corti, Reed College, Federico Covi, University of Alaska Fairbanks, Clement Miege, Rutgers, The State University of New Jersey, Jonathan Kingslake, Lamont -Doherty Earth Observatory, Sasha Leidman, Rutgers, The State University of New Jersey, Xavier Fettweis, University of Liege
Topics: Cryosphere, Climatology and Meteorology, Water Resources and Hydrology
Keywords: Hydrology, Cryosphere, Climate Change, Glaciers, Ice Sheet, Greenland
Session Type: Paper
Day: 4/6/2019
Start / End Time: 9:55 AM / 11:35 AM
Room: Truman, Marriott, Mezzanine Level
Presentation File: No File Uploaded

An enormous amount of meltwater forms on the Greenland ice sheet surface each summer. Slightly more than half of that meltwater outflows into the oceans and the remaining water infiltrate into firn (snow surviving at least one melting season) where may refreeze and form ice lenses. Previous studies conducted after the huge melt year of 2012, show that when these ice lenses become meter thick, they may prevent further infiltration into firn. Instead of refreezing, meltwater forms supraglacial channels and runoff to the ocean where it may raise global sea levels. Here we examine the spatial variability of ice lens distributions in five 20-meter long cores collected in 2017 at elevations spanning from 2000 to 2400 m a.s.l. in Southwest Greenland. At two locations, we compared our 2017 firn cores with cores collected in 1989 and 1998, respectively. We also contrasted our firn core observations with model estimates of refreezing and other surface mass balance using Modèle Atmosphérique Régional (MAR). The analysis of 2017 cores reveals a sharp increase in ice lens thickness as surface elevation drops, covarying tightly with modeled annual refreezing at each site. Similarly, a considerable increase in firn ice content since 1989 and 1998 is matched by a substantial increased refreezing. While we do not find evidence of meter thick ice lenses, our findings agree with other studies that show how firn pores space is rapidly diminishing, and with that the percolation zone’s capability to absorb future increases in ice sheet surface melting.

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