Sea ice collapse at both poles ‘is coming sooner than expected’
Ice sheets at both poles could be about to melt, triggering a rapid sea level rise, if global temperatures cannot be stabilised at 1.8C above pre-industrial levels.
A new study has shown that an irreversible loss of the West Antarctic and Greenland ice sheets could be imminent.
Professor Axel Timmermann, co-author of the study and director of the IBS Center for Climate Physics said: "If we miss this emission goal, the ice sheets will disintegrate and melt at an accelerated pace, according to our calculations.
“If we don't take any action, retreating ice sheets would continue to increase sea level by at least 100 cm within the next 130 years. This would be on top of other contributions, such as the thermal expansion of ocean water.”
Such a loss could lead sea levels to rise by several feet and displace up to one in the world’s population, experts have previously warned.
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The researchers used a new computer model, which captures for the first time the coupling between ice sheets, icebergs, ocean and atmosphere.
The climate researchers found that an ice sheet/sea level run-away effect can be prevented only if the world reaches net zero carbon emissions before 2060.
Coastal populations worldwide are already bracing for rising seas.
Planning for counter-measures to prevent inundation and other damages has been extremely difficult since the latest climate model projections presented in the 6th assessment report of the Intergovernmental Panel on Climate Change (IPCC) do not agree on how quickly the major ice sheets will respond to global warming.
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Melting ice sheets are potentially the largest contributor to sea level change, and historically the hardest to predict because the physics governing their behaviour is notoriously complex.
Lead author Jun Young Park, PhD student at the IBS Center for Climate Physics and Pusan National University, Busan, South Korea and first author of the study, said: "Moreover, computer models that simulate the dynamics of the ice sheets in Greenland and Antarctica often do not account for the fact that ice sheet melting will affect ocean processes, which, in turn, can feed back onto the ice sheet and the atmosphere," says.
Ice sheets respond to atmospheric and oceanic warming in delayed and often unpredictable ways.
Scientists have highlighted the importance of subsurface ocean melting as a key process, which can trigger runaway effects in the major marine based ice sheets in Antarctica.
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Professor June Yi Lee, from the IBS Center for Climate Physics and Pusan National University and co-author of the study, said: "According to our supercomputer simulations, the effectiveness of these processes may have been overestimated in recent studies.
"We see that sea ice and atmospheric circulation changes around Antarctica also play a crucial role in controlling the amount of ice sheet melting with repercussions for global sea level projections.”
The study highlights the need to develop more complex earth system models, which capture different climate components, as well as their interactions.
Furthermore, new observational programs are needed to constrain the representation of physical processes in earth system models, in particular from highly active regions, such as Pine Island glacier in Antarctica.
Prof Timmermann said, "One of the key challenges in simulating ice sheets is that even small-scale processes can play a crucial role in the large-scale response of an ice sheet and for the corresponding sea-level projections.
“Not only do we have to include the coupling of all components, as we did in our current study, but we also need to simulate the dynamics at the highest possible spatial resolution using some of the fastest supercomputers.”
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