Basal conditions play an essential role in the dynamics of outlet glaciers, but direct observations at the bed of glaciers are challenging to obtain. Instead, inverse methods can be used to infer basal parameters from surface observations. Here, we use a simple ice-flow model as a forward model in an inversion scheme to retrieve the spatio-temporally variable basal stress parameter for Hagen Bræ, North Greenland, from 1990 to 2020. Hagen Bræ is a surge-type glacier with up to an order of magnitude variability of winter velocities near the grounding line. We find that downstream changes in the basal stress parameter can explain most of the variation of flow velocity, and we further identify a region of high resistance ~20–40 km from the grounding line. We hypothesise that this region of high resistance plays an important role in controlling glacier discharge.
Bibliographical noteFunding Information:
Ice velocity maps were produced as part of the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) using Copernicus Sentinel-1 SAR images distributed by ESA, and were provided by the Geological Survey of Denmark and Greenland (GEUS) at http://www.promice.dk . PROMICE is funded by the Geological Survey of Denmark and Greenland (GEUS) and the Danish Ministry of Climate, Energy and Utilities under the Danish Cooperation for Environment in the Arctic (DANCEA), and is conducted in collaboration with DTU Space (Technical University of Denmark) and Asiaq, Greenland. Ice velocity maps before 2015 are provided by the ESA Greenland Ice sheet CCI project ( www.esa-icesheets-greenland-cci.org ). Model output and information on how to obtain the data shown in Figures 1b and 1c are available at GEUS Dataverse (doi: 10.22008/FK2/SVMNIK). The authors thank James Lea, University of Liverpool for helpful discussions on the availability of DEMs.
© The Author(s), 2021. Published by Cambridge University Press.
- Arctic glaciology
- glacier flow
- glacier modelling
- glacier surges
- ice velocity