The tipping points and early warning indicators for Pine Island Glacier, West Antarctica
Summary
Abstract. Mass loss from the Antarctic Ice Sheet is the main sourceof uncertainty in projections of future sea-level rise, with importantimplications for coastal regions worldwide. Central to ongoing and futurechanges is the marine ice sheet instability: once a critical threshold, ortipping point, is crossed, ice internal dynamics can drive a self-sustainingretreat committing a glacier to irreversible, rapid and substantial iceloss. This process might have already been triggered in the Amundsen Searegion, where Pine Island and Thwaites glaciers dominate the current massloss from Antarctica, but modelling and observational techniques have notbeen able to establish this rigorously, leading to divergent views on thefuture mass loss of the West Antarctic Ice Sheet. Here, we aim at closingthis knowledge gap by conducting a systematic investigation of the stabilityregime of Pine Island Glacier. To this end we show that early warningindicators in model simulations robustly detect the onset of the marine icesheet instability. We are thereby able to identify three distinct tippingpoints in response to increases in ocean-induced melt. The third and finalevent, triggered by an ocean warming of approximately 1.2 ∘C fromthe steady-state model configuration, leads to a retreat of the entireglacier that could initiate a collapse of the West Antarctic Ice Sheet.
