Geometry and thermal regime of the southern outlet glaciers of Qaanaaq Ice Cap, NW Greenland

Abstract

Glaciers and ice caps surrounding the Greenland Ice Sheet are found to be sensitive to warming climate thus the knowledge of their thickness and internal structure is substantial to determine their future impact on sea level and local environment. Still, in situ glaciological measurements of such glaciers are very scarce. Here, we present the results of ground penetrating radar (GPR) and uncrewed aerial vehicle surveys conducted on the two southern outlet glaciers of Qaanaaq Ice Cap in NW Greenland. GPR measurements reveal up to 170 m thick ice and the lack of englacial hyperbolae indicating no developed en/subglacial drainage system. The glaciers consist mainly of radar transparent facies characteristic for cold ice, while limited scattering facies appear closer to the glacier's terminus beneath the thinnest ice and are attributed to debris inside the ice. Results show that the glaciers flow into narrow V-shaped valleys suggesting spatio-temporally limited subglacial erosion and restricted possible distribution of temperate ice in the past. The comparison of the ice thickness measurement data with global ice thickness model estimates shows considerable discrepancies emphasising the need of modelling improvements in the case of narrow valley and outlet glaciers.