Overshooting the critical threshold for the Greenland ice sheet

• Published in: Nature
• Main Authors: Bochow, N., Poltronieri, A., Robinson, A., Montoya, Marisa
• Other Authors: Research Council of Norway, European Commission
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Springer Nature 2023
• Subjects: Arctic; Greenland; Norway; Global warming; Ice Sheet; Arctic University of Norway; UiT The Arctic University of Norway
• Online Access: http://hdl.handle.net/10261/359219; https://doi.org/10.1038/s41586-023-06503-9

Melting of the Greenland ice sheet (GrIS) in response to anthropogenic global warming poses a severe threat in terms of global sea-level rise (SLR). Modelling and palaeoclimate evidence suggest that rapidly increasing temperatures in the Arctic can trigger positive feedback mechanisms for the GrIS, leading to self-sustained melting, and the GrIS has been shown to permit several stable states. Critical transitions are expected when the global mean temperature (GMT) crosses specific thresholds, with substantial hysteresis between the stable states. Here we use two independent ice-sheet models to investigate the impact of different overshoot scenarios with varying peak and convergence temperatures for a broad range of warming and subsequent cooling rates. Our results show that the maximum GMT and the time span of overshooting given GMT targets are critical in determining GrIS stability. We find a threshold GMT between 1.7 °C and 2.3 °C above preindustrial levels for an abrupt ice-sheet loss. GrIS loss can be substantially mitigated, even for maximum GMTs of 6 °C or more above preindustrial levels, if the GMT is subsequently reduced to less than 1.5 °C above preindustrial levels within a few centuries. However, our results also show that even temporarily overshooting the temperature threshold, without a transition to a new ice-sheet state, still leads to a peak in SLR of up to several metres. This is TiPES contribution #209; the TiPES (‘Tipping Points in the Earth System’) project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 820970. This work was supported by the UiT Aurora Centre Program, UiT The Arctic University of Norway (2020) and the Research Council of Norway (project number 314570). The simulations with PISM-dEBM were performed on the Fram supercomputer provided by Sigma2 - the National Infrastructure for High Performance Computing and Data Storage in Norway under the projects NN8008K and NN9348K. N.Boe. acknowledges further funding ...