Frictional Origin of Slip Events of the Whillans Ice Stream, Antarctica

• Published in: Geophysical Research Letters
• Main Authors: Guerin, Gauthier, Mordret, Aurélien, Rivet, Diane, Lipovsky, Bradley, Minchew, Brent
• Other Authors: Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD France-Sud )
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; West Antarctica; Whillans; Whillans Ice Stream; Antarc*; Antarctica; Ice Sheet
• Online Access: https://hal.science/hal-03327192; https://hal.science/hal-03327192/document; https://hal.science/hal-03327192/file/Geophysical%20Research%20Letters%20-%202021%20-%20Guerin%20-%20Frictional%20Origin%20of%20Slip%20Events%20of%20the%20Whillans%20Ice%20Stream%20Antarctica.pdf; https://doi.org/10.1029/2021GL092950

International audience Ice sheet evolution depends on subglacial conditions, with the ice-bed interface's strength exerting an outsized role on the ice dynamics. Along fast-flowing glaciers, this strength is often controlled by the deformation of subglacial till, making quantification of spatial variations of till strength essential for understanding ice-sheet contribution to sea-level. This task remains challenging due to a lack of in situ observations. We analyze continuous seismic data from the Whillans Ice Plain (WIP), West Antarctica, to uncover spatio-temporal patterns in subglacial conditions. We exploit tidally modulated stick-slip events as a natural source of sliding variability. We observe a significant reduction of the till seismic wave-speed between the WIP sticky-spots. These observations are consistent with a poroelastic model where the bed experiences relative porosity and effective pressure increases of >11% during stick-slips. We conclude that dilatant strengthening appears to be an essential mechanism in stabilizing the rapid motion of fast-flowing ice streams.