EGU25-13219, updated on 15 Mar 2025
https://doi.org/10.5194/egusphere-egu25-13219
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Investigating the role of evolving basal motion in modulating global glacier change
William Armstrong1, Amaury Dehecq2, Regine Hock3, Fanny Brun2, Olivier Gagliardini2, Fabien Gillet-Chaulet2, Adrien Gilbert2, Florent Gimbert2, Romain Millan2, and Christian Vincent2
William Armstrong et al.
  • 1Appalachian State University, Department of Geological and Environmental Sciences, United States of America (armstrongwh@appstate.edu)
  • 2Université Grenoble Alpes, Institut des Géosciences de l’Environnement
  • 3University of Oslo, Department of Geosciences

Slip at the ice-bed interface (basal motion) dominates the flow of many glaciers, and it is uncertain whether this velocity component will increase or slow in a warmer world. Past results from an idealized flowline glacier model show that declining basal motion induces a two-phase response that initially accelerates glacier retreat in a warming climate on a multidecadal timescale but lessens centennial-scale retreat and mass loss. In the present work, we utilize existing field-collected and remotely-sensed constraints on ice thickness, ice surface velocity, and the change in each of these terms to constrain the current rate of basal motion and its change over the past ~40 years. We focus on the ~1500 global glaciers with higher density of field-based ice thickness measurements in the GlaThiDa dataset (>18 measurements points per glacier). Utilizing these ice thickness and surface velocity constraints, we employ a flow model to estimate the rate of basal motion as the residual between observed surface velocity and modeled ice deformation. We first estimate the contribution of varying basal motion to observed changes in surface velocity across the study glaciers.  We then estimate these glaciers’ retreat and thinning responses to changing velocity and compare these with the magnitudes expected from atmospheric warming, constrained by published point measurements, mass balance models, and snowline observations. These results will constrain the extent to which evolving ice dynamics have amplified or mitigated the response of global glaciers to climate change over past decades. Further, this knowledge will provide insight into the potential importance of varying basal motion on projections of future glacier change, with implications for global sea level rise as well as local water resource and ecosystem management.

How to cite: Armstrong, W., Dehecq, A., Hock, R., Brun, F., Gagliardini, O., Gillet-Chaulet, F., Gilbert, A., Gimbert, F., Millan, R., and Vincent, C.: Investigating the role of evolving basal motion in modulating global glacier change, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13219, https://doi.org/10.5194/egusphere-egu25-13219, 2025.