Basal traction mainly dictated by hard-bed physics over grounded regions of Greenland

• Main Authors: Maier, Nathan, Gimbert, Florent, Gillet-Chaulet, Fabien, Gilbert, Adrien
• Format: Text
• Language: English
• Published: 2020
• Subjects: Greenland; Weertman; Ice Sheet
• Online Access: https://doi.org/10.5194/tc-2020-185; https://tc.copernicus.org/preprints/tc-2020-185/

On glaciers and ice sheets, identifying the relationship between velocity and traction is critical to constrain the bed physics that control ice flow. Yet in Greenland, these relationships remain unquantified. We determine the spatial relationship between velocity and traction in all eight drainage catchments of Greenland. The basal traction is estimated using three different methods over large grid cells to minimize interpretation biases associated with unconstrained rheologic parameters used in numerical inversions. We find the relationships are consistent with our current understanding of basal physics in each catchment. We identify catchments that predominantly show Mohr-Coulomb-like behavior typical of deforming beds or significant cavitation, as well as catchments that predominantly show rate-strengthening behavior typical of Weertman-type hard-bed physics. Overall, the traction relationships suggest that the flow field and surface geometry over the grounded regions of the Greenland ice sheet is mainly dictated by Weertman-type hard-bed physics. Given the complex basal boundary across Greenland, the relationships are captured surprisingly well by simple traction laws over the entire velocity range, including regions with velocities over 1000 m/yr, which provide a parameterization that can be used to model ice dynamics at large scales. The results and analysis serve as a fundamental constraint on the physics of basal motion in Greenland and provide unique insight into future dynamics and vulnerabilities in a warming climate.