Uncovering Basal Friction in Northwest Greenland Using an Ice Flow Model and Observations of the Past Decade

Abstract

AbstractGlaciers move under the pull of gravity due to a combination of internal deformation (creep) and basal sliding. Basal sliding dominates ice motion in fast flowing areas, and an accurate description of sliding in ice flow models is therefore critical to adequately capture ice dynamics and its temporal evolution. However, there is currently no consensus on the exact form of basal friction law, as direct observations of basal properties remain limited. Using an ice flow model and observations of the past decade, we evaluate a variety of friction laws and determine their ability to reproduce the observed acceleration and mass loss of marine‐terminating glaciers in northwest Greenland. We find that friction laws that include an explicit dependence on the effective pressure better reproduce the observed acceleration and mass loss overall, with semi‐plastic basal laws describing some glaciers well. Our glacier‐scale model evaluation suggests heterogeneous bed conditions under northwest Greenland, which cannot be detected from the results of regional changes. Accounting for heterogeneous bed conditions, this region might contribute 15 mm to sea level rise by 2100, twice as much as predicted from models based on commonly used uniform bed conditions.