The tipping points and early warning indicators for Pine Island Glacier, West Antarctica

Sebastian H R Rosier,Jan De Rydt,Ricarda Winkelmann,G Hilmar Gudmundsson,Jonathan F Donges,Ronja Reese

doi:10.5194/tc-15-1501-2021

Abstract

Abstract. Mass loss from the Antarctic Ice Sheet is the main source of uncertainty in projections of future sea-level rise, with important implications for coastal regions worldwide. Central to ongoing and future changes is the marine ice sheet instability: once a critical threshold, or tipping point, is crossed, ice internal dynamics can drive a self-sustaining retreat committing a glacier to irreversible, rapid and substantial ice loss. This process might have already been triggered in the Amundsen Sea region, where Pine Island and Thwaites glaciers dominate the current mass loss from Antarctica, but modelling and observational techniques have not been able to establish this rigorously, leading to divergent views on the future mass loss of the West Antarctic Ice Sheet. Here, we aim at closing this knowledge gap by conducting a systematic investigation of the stability regime of Pine Island Glacier. To this end we show that early warning indicators in model simulations robustly detect the onset of the marine ice sheet instability. We are thereby able to identify three distinct tipping points in response to increases in ocean-induced melt. The third and final event, triggered by an ocean warming of approximately 1.2 ∘C from the steady-state model configuration, leads to a retreat of the entire glacier that could initiate a collapse of the West Antarctic Ice Sheet.

Highlights

The West Antarctic Ice Sheet (WAIS) is regarded as a tipping element in the Earth’s climate system, defined as a major component of the Earth system susceptible to tippingpoint behaviour (Lenton et al, 2008)
To this end we show that early warning indicators in model simulations robustly detect the onset of the marine ice sheet instability
We present our results in terms of both aforementioned criteria: whether an early warning indicators (EWIs) reaches a critical value preceding the tipping point and whether the EWI is consistently increasing for a period of time before the tipping point

Summary

Introduction

The West Antarctic Ice Sheet (WAIS) is regarded as a tipping element in the Earth’s climate system, defined as a major component of the Earth system susceptible to tippingpoint behaviour (Lenton et al, 2008). Grounding-line advance leading to an increase in accumulation greater than the change in flux will lead to a continued advance. In this regime, a small perturbation in the system can result in the system crossing a tipping point, beyond which a positive feedback propels the system to a contrasting state (Fig. 1c). A complex range of factors can either cause or suppress MISI (Haseloff and Sergienko, 2018; Pegler, 2018; O’Leary et al, 2013; Gomez et al, 2010; Robel et al, 2016), and the difficulties in predicting this behaviour are a major source of uncertainty for future sea-level-rise projections (Church et al, 2013; Bamber et al, 2019; Oppenheimer et al, 2019; Robel et al, 2019)

Methods

Results

Discussion

Conclusion