title: Collapse of the West Antarctic Ice Sheet after local destabilization of the Amundsen Basin.
abstract: The future evolution of the Antarctic Ice Sheet represents the largest uncertainty in sea-level projections of this and upcoming centuries. Recently, satellite observations and high-resolution simulations have suggested the initiation of an ice-sheet instability in the Amundsen Sea sector of West Antarctica, caused by the last decades' enhanced basal ice-shelf melting. Whether this localized destabilization will yield a full discharge of marine ice from West Antarctica, associated with a global sea-level rise of more than 3 m, or whether the ice loss is limited by ice dynamics and topographic features, is unclear. Here we show that in the Parallel Ice Sheet Model, a local destabilization causes a complete disintegration of the marine ice in West Antarctica. In our simulations, at 5-km horizontal resolution, the region disequilibrates after 60 y of currently observed melt rates. Thereafter, the marine ice-sheet instability fully unfolds and is not halted by topographic features. In fact, the ice loss in Amundsen Sea sector shifts the catchment's ice divide toward the Filchner-Ronne and Ross ice shelves, which initiates grounding-line retreat there. Our simulations suggest that if a destabilization of Amundsen Sea sector has indeed been initiated, Antarctica will irrevocably contribute at least 3 m to global sea-level rise during the coming centuries to millennia.
authors.affiliation: Potsdam Institute for Climate Impact Research, 14473 Potsdam, Germany; Institute of Physics, Potsdam University, 14476 Potsdam, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Feldmann
authors.affiliation: Potsdam Institute for Climate Impact Research, 14473 Potsdam, Germany; Institute of Physics, Potsdam University, 14476 Potsdam, Germany anders.levermann@pik-potsdam.de.
authors.forename: Anders
authors.initials: A
authors.lastname: Levermann
keywords: West Antarctic Ice Sheet; instability; marine ice-sheet instability; sea-level rise; tipping point