Ice-ocean-subglacial hydrology interactions, and recent evolution of the Thwaites glacier

The retreat of the Antarctic Ice Sheet is conventionally attributed to ocean melting of fringing ice shelves, potentially enhanced by internal instability due to the proximity of its grounding lines to retrograde bed slopes. Ocean melting is enhanced by increased intrusion of modified Circumpolar Deep Water (mCDW) within ice shelf cavities. Several processes can enhance the ability of mCDW to melt ice shelves. Upwelling from the release of subglacial melt water at the grounding line is arguably one of the least well constrained and understood and is currently not accounted for in projections of ice sheet loss.The Thwaites glacier in the Amundsen Sea sector of the west Antarctic ice sheet has been the focus of recent investigations given its current rapid retreat, potential instability, and its impact on rates of future sea level change. In 2013, a network of subglacial lakes under the Thwaites glacier drained, the combined outflow reached a peak discharge in excess of 500 m3 s-1 and likely reached the grounding line. During this period, several other processes took place at the grounding line and under the fringing floating ice. This event offers a natural experiment to examine the impact of subglacial outflow on ocean melting of ice shelves.In this presentation we revisit the various events affecting the Thwaites system during this period and generate several new observations of lake discharge, rates of ice shelf basal melting, and grounding line thinning and retreat. We focus the discussion on the potential feedback between lake discharge, variation in ocean melting, and grounding line retreat, and on the contribution of subglacial discharge to the recent retreat of the Thwaites glacier.