Winter speed-up of quiescent surge-type glaciers in Yukon, Canada

Abstract

Abstract. Glacier surge is known to often initiate in winter, but the mechanisms remain unclear in light of the summer speed-up at normal glaciers. We examined spatial-temporal changes in the ice velocity of surge-type glaciers near the border of Alaska and Yukon, and found significant upstream accelerations from fall to winter, regardless of surging episodes. Moreover, whereas the summer speed-up was observed downstream, the winter speed-up propagated from upstream to downglacier. Given the absence of upstream surface meltwater input in winter, we speculate the presence of water storages near the base that do not directly connect to the surface but can promote basal sliding through increased water pressure as winter approaches. Our findings have implications for modeling of glacial hydrology in winter time, and its link to glacier dynamics and subglacial erosion.