Multistability and critical thresholds of the Greenland ice sheet

Author:  ["Alexander Robinson","Reinhard Calov","Andrey Ganopolski"]

Publication:  Nature Climate Change

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Tags:     Climate environment

Abstract

A comprehensive stability analysis shows that the critical global temperature rise that leads to collapse of the Greenland ice sheet is only 1–2 °C above the pre-industrial climate state, which is significantly lower than previously believed. Recent studies have focused on the short-term contribution of the Greenland ice sheet to sea-level rise, yet little is known about its long-term stability. The present best estimate of the threshold in global temperature rise leading to complete melting of the ice sheet is 3.1 °C (1.9–5.1 °C, 95% confidence interval) above the preindustrial climate1, determined as the temperature for which the modelled surface mass balance of the present-day ice sheet turns negative. Here, using a fully coupled model, we show that this criterion systematically overestimates the temperature threshold and that the Greenland ice sheet is more sensitive to long-term climate change than previously thought. We estimate that the warming threshold leading to a monostable, essentially ice-free state is in the range of 0.8–3.2 °C, with a best estimate of 1.6 °C. By testing the ice sheet’s ability to regrow after partial mass loss, we find that at least one intermediate equilibrium state is possible, though for sufficiently high initial temperature anomalies, total loss of the ice sheet becomes irreversible. Crossing the threshold alone does not imply rapid melting (for temperatures near the threshold, complete melting takes tens of millennia). However, the timescale of melt depends strongly on the magnitude and duration of the temperature overshoot above this critical threshold.

Cite this article

Robinson, A., Calov, R. & Ganopolski, A. Multistability and critical thresholds of the Greenland ice sheet. Nature Clim Change 2, 429–432 (2012). https://doi.org/10.1038/nclimate1449

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