Regional observation of glacier surges from space: monthly time series and application to physical theories.

Glacier surges are spectacular events that lead to surface elevation changes of tens of meters in a period of a few months to a few years, with different patterns of mass transport. They can result in surface elevation changes of more than 100 m in a few months. Recent developments in remote sensing have enabled the estimation of glacier elevation change and surface velocity at monthly resolution. These two variables are crucial to constrain the physical mechanisms responsible for glacier surges.

In this work, we exploit a large archive of Digital Elevation Models (DEMs) over 2000-2019 from the ASTER optical satellite sensor. The time series is filtered and homogenized to monthly elevations, in order to study surging glaciers in the Karakoram (Beraud et al., under review). This workflow implements a LOWESS method – locally weighted polynomial regression for filtering and a B-spline method ALPS-REML as elevation temporal interpolation. Additionally, we use ITS_LIVE glacier surface velocities, regularized to monthly dates using the temporal closure of the displacement measurement network (Charrier et al., 2022).

On the modelling side, Thogersen et al. (2019; 2024) theorised a surge propagation mechanism based on the rate and state approach of basal friction. They found that, first, a surge is triggered when a shear stress is reached over a sufficiently large area and, second, it exists relationship between the velocity of the surge front propagation and the sliding velocity. We then explore over about five glaciers the ability of the two datasets to test Thogersen's theory of surge initiation and propagation.

 

References:

Beraud, L., Brun, F., Dehecq, A., Hugonnet, R., and Shekhar, P.: Glacier surge monitoring from temporally dense elevation time series: application to an ASTER dataset over the Karakoram region, https://doi.org/10.5194/egusphere-2024-3480, In review.

Charrier, L., Yan, Y., Koeniguer, E. C., Leinss, S., and Trouve, E.: Extraction of Velocity Time Series With an Optimal Temporal Sampling From Displacement Observation Networks, IEEE Transactions on Geoscience and Remote Sensing, 60, 1–10, https://doi.org/10.1109/TGRS.2021.3128289, 2022

Thøgersen, K., Gilbert, A., Schuler, T. V., and Malthe-Sørenssen, A.: Rate-and-state friction explains glacier surge propagation, Nature Communications, 10, 2823, https://doi.org/10.1038/s41467-019-10506-4, 2019.

Thøgersen, K., Gilbert, A., Bouchayer, C., and Schuler, T. V.: Glacier Surges Controlled by the Close Interplay Between Subglacial Friction and Drainage, Journal of Geophysical Research: Earth Surface, 129, e2023JF007 441, https://doi.org/10.1029/2023JF007441, 2024.