Bridging Observations and Models: Isolating Frictional and Frontal Controls on Glacier Dynamics in Northwestern and Central-West Greenland

The Greenland Ice Sheet is a major contributor to present-day sea-level rise, with ice dynamics playing a central role in its mass loss. Previous studies suggest that Greenland’s glaciers can be broadly classified into three distinct types based on seasonal velocity patterns near the ice front. The differences between patterns are primarily attributed to interactions of two critical processes: basal motion at the ice-bed interface and frontal ablation at the ice-ocean interface. Many glaciers exhibit behaviour that deviates from the idealised classifications, and even within the same glacier, the patterns may vary significantly from upstream to downstream. These observations underscore the complexity of the processes that drive ice motion.

In this study, we aim to separate the influences of basal motion and frontal ablation on the seasonal flow variations of 33 marine-terminating outlet glaciers in Northwestern and Central-West Greenland. Using surface velocity observations derived from the ITS_LIVE offset-tracking dataset, we compare these with modelled results from the Ice-sheet and Sea-level System Model, which incorporates monthly ice-front positions and surface mass balance inputs but neglects explicit subglacial hydrology. By incorporating modelled velocities, we move from correlation to causation, quantifying the contributions of frontal dynamics and basal conditions to the seasonal flow signal. This allows us to explore the extent to which each driver affects specific locations in a crucial step toward a greater understanding of the spatial and temporal variability in glacier behaviour.