Active subglaical lakes beneath the stagnant trunk of Kamb Ice Stream: evidence of channelized subglacial flow

Abstract. We have identified two new subglacial lakes beneath the stagnated trunk of Kamb Ice Stream (KIS). Rapid fill-drain hydrologic events are inferred from Cryosat-2 altimetry, indicating that the lakes are connected by a drainage network. The orientation of the drainage network is inferred from the regional hydraulic potential, and clearly links the lake areas. The behavior of the subglacial lakes and strong thinning observed at the outlet near the grounding line implies that the subglacial water persistently flows from the region above the trunk to grounding line of KIS. In addition, the ice sheet in the KIS trunk estuary is thinning rapidly, and the thinning is accelerated by the activity of subglacial lake. We suggest that a transition from sheet flow of sub-glacial water to well-drained channelized flow may explain the shutdown of Kamb Ice Stream.