2025 CSDMS meeting-141
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Basal motion modulates glacier change in a warming climate
William Armstrong,
(he/him),Appalachian State University Boone North Carolina, United States. armstrongwh@appstate.edu
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 response to climate warming 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 our analysis on glaciers with well-constrained ice thickness, mass balance, and velocity records. Utilizing these constraints, we employ a simple flowline model to 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.
