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

Gauthier Guerin (1) , Aurélien Mordret , Diane Rivet (1) , Bradley Lipovsky , Brent Minchew

1 GEOAZUR 7329 - Géoazur

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.

Domaines: Géophysique [physics.geo-ph]; Glaciologie

Gauthier Guerin, Aurélien Mordret, Diane Rivet, Bradley Lipovsky, Brent Minchew. Frictional Origin of Slip Events of the Whillans Ice Stream, Antarctica. Geophysical Research Letters, 2021, 48 (11), ⟨10.1029/2021GL092950⟩. ⟨hal-03327192⟩