Inland thinning of West Antarctic Ice Sheet steered along subglacial rifts

Current ice loss from the West Antarctic Ice Sheet (WAIS) accounts for about ten per cent of observed global sea-level rise1. Losses are dominated by dynamic thinning, in which forcings by oceanic or atmospheric perturbations to the ice margin lead to an accelerated thinning of ice along the coastline2, 3, 4, 5. Although central to improving projections of future ice-sheet contributions to global sea-level rise, the incorporation of dynamic thinning into models has been restricted by lack of knowledge of basal topography and subglacial geology so that the rate and ultimate extent of potential WAIS retreat remains difficult to quantify. Here we report the discovery of a subglacial basin under Ferrigno Ice Stream up to 1.5 kilometres deep that connects the ice-sheet interior to the Bellingshausen Sea margin, and whose existence profoundly affects ice loss. We use a suite of ice-penetrating radar, magnetic and gravity measurements to propose a rift origin for the basin in association with the wider development of the West Antarctic rift system. The Ferrigno rift, overdeepened by glacial erosion, is a conduit which fed a major palaeo-ice stream on the adjacent continental shelf during glacial maxima6. The palaeo-ice stream, in turn, eroded the ‘Belgica’ trough, which today routes warm open-ocean water back to the ice front7 to reinforce dynamic thinning. We show that dynamic thinning from both the Bellingshausen and Amundsen Sea region is being steered back to the ice-sheet interior along rift basins. We conclude that rift basins that cut across the WAIS margin can rapidly transmit coastally perturbed change inland, thereby promoting ice-sheet instability

Sediment Budgets in High-Mountain Areas: Review and Challenges

The changes in the sediment transport regimes of high-mountain areas as a consequence of global warming have received growing attention by geomorphologists, not only because these changes can imply a heightened threat to human infrastructure. While many studies dealing with high-mountain sediment transport processes (e.g., rock fall, debris flows, avalanches, stream transport) have focused on one process only, few studies have tried to establish a holistic view of the sediment transport in high-mountain catchments. This review chapter identifies the need for research in high-mountain sediment budgets, aims at providing an overview of studies that have contributed to this goal, and discusses the methodological state of the art in the different steps necessary for sediment budget construction. In addition, relevant research gaps will be identified, thereby showing potential for future research