Topographic controls on the distribution of dark ice on the surface of the Greenland Ice Sheet

Abstract

The Greenland Ice Sheet (GrIS) is the largest single cyospheric contributor to global sea level rise. The surface ice albedo modulates the absorption of solar radiation and the current darkening of the GrIS enhances the surface meltwater production. However, the dark ice is unevenly distributed on the GrIS. Remote sensing observations found that dark ice is limited to the margin in the southeast region, while the spatial extent of dark ice stretches further inland in the southwest GrIS. This band of dark ice, with an albedo that is significantly lower than the surrounding ice in the melt season, is known as the Dark Zone. One hypothesis is that the spatial distribution of dark ice is influenced by topography, and surface slope in particular. This study attempts to verify this hypothesis and presents the first medium resolution (30 m) analysis of the topographic controls on the distribution of dark ice on the surface of the GrIS. The association between albedo and topographic factors, such as elevation, slope and aspect, and the distance from the ice margin, and the duration of bare ice exposure, are investigated using the ArcticDEM and a satellite albedo product derived from a harmonized Landsat and Sentinel 2 dataset. The results may allow certain controls on glacier ice algal growth, a key contributor to the progressive darkening of the ice surface, to be surmised.