Seminar by: Adrien Gilbert, CNRS, Université Grenoble Alpes:
Predicting seasonal and long-term glacier dynamics
Abstract: Short- and long-term glacier dynamics are critically dependent on how basal sliding responds to changes in basal stress and subglacial water pressure. However, the mechanisms governing these variations are still being debated, and evaluating water pressure fluctuations in the short and long term remains challenging.
Using multidecadal to century-scale surface velocity observations from eight Alpine glaciers, we show that changes in basal friction can be described within a single framework of stress-bounded friction law in which the average basal effective pressure is constant over time but varies from site to site. We suggest that constant effective pressure may occur as a result of channel-like conduits controlling winter drainage through establishing connections across basal cavities in the absence of surface melt input. This hypothesis is supported by our observation that average basal effective pressure depends on surface slope, which is consistent with steady channel theory, in which pressure is a function of hydraulic potential gradients.
In order to confirm the critical role of surface slope in regulating water pressure, we also analyzed seven years of satellite observations across the Mont Blanc massif at a high temporal resolution. Our results confirm that seasonal glacier flow regimes (phase and amplitude) are also primarily controlled by surface slope rather than by variations in subglacial discharge, as was previously thought. This dependence on surface slope of both long-term and short-term glacier dynamics led us to a reconceptualization of the distributed drainage system, in which cavity clusters and conduits, connected in series, alternately control water pressure throughout the seasonal cycle. Remarkably, this framework provides a link between short- and long-term dynamics, revealing that seasonal glacier dynamics can provide a diagnostic of the long-term basal friction evolution.
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About the seminar series
The talks in GeoHyd Lunch Seminar Series are offered by the Section for Geography and Hydrology (GeoHyd), Dept. of Geosciences, University of Oslo. The seminars are announced as lunch seminars so bring your lunch if you want to.
The seminars are open for everyone interested, and especially students are welcome!
The GeoHyd Lunch Seminar Team
– Regine, Andi and Anita