13 Apr 2022
13 Apr 2022
Status: this preprint is open for discussion.

In situ measurements of meltwater flow through snow and firn in the accumulation zone of the SW Greenland Ice Sheet

Nicole Clerx1, Horst Machguth1, Andrew Tedstone1, Nicolas Jullien1, Nander Wever2, Rolf Weingartner3, and Ole Roessler3,a Nicole Clerx et al.
  • 1Department of Geosciences, University of Fribourg, Fribourg, Switzerland
  • 2Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, CO, USA
  • 3Institute of Geography and Oescher Centre for Climate Change Research, University of Bern, Bern, Switzerland
  • anow at: German Federal Institute of Hydrology (BfG), Koblenz, Germany

Abstract. The Greenland Ice Sheet is losing mass, part of which is caused by increasing runoff. The location of the runoff limit, the highest elevation from which meltwater finds its way off the ice sheet, plays an important role in the surface mass balance of the ice sheet. The recently observed rise in runoff area might be related to an increasing amount of refreezing: ice layer development in the firn hinders vertical percolation and promotes lateral runoff. To investigate meltwater flow near the runoff limit in the accumulation zone on the southwest Greenland Ice Sheet, we carried out in situ measurements of hydrological processes and properties of firn and snow. The hydraulic conductivity of icy firn in pre-melt conditions measured using a portable lysimeter ranges from 0.17 to 12.8 m hr-1, with flow predominantly occurring through preferential flow fingers. Lateral flow velocities of meltwater on top of the near-surface ice slab at the peak of the melt season measured by salt dilution- and tracer experiments range from 1.3 to 15.1 m hr-1. With these lateral flow velocities the distance between the slush limit, the highest elevation where liquid water is visible on the ice sheet surface, and the runoff limit could be up to 4 km in regions where near-surface ice slabs are present. These measurements are a first step towards an integrated set of hydrological properties of firn on the SW Greenland Ice Sheet, and show evidence that meltwater runoff might occur from elevations above the visible runoff area.

Nicole Clerx et al.

Status: open (until 08 Jun 2022)

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Nicole Clerx et al.

Nicole Clerx et al.


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Short summary
Meltwater runoff is one of the main contributors to mass loss on the Greenland Ice Sheet that influences global sea level rise. However, it remains unclear where meltwater runs off and what processes cause this. We measured the velocity of meltwater flow through snow on the ice sheet, which ranged from 0.17 to 12.8 m hr-1 for vertical percolation and from 1.3 to 15.1 m hr-1 for lateral flow. This is an important step towards understanding where, when and why meltwater runoff occurs on the ice sheet.