A study published in Nature Communications by an international team of scientists shows that
an irreversible loss of the West Antarctic and Greenland ice sheets, and a corresponding rapid acceleration
of sea level rise, may be imminent if global temperature change cannot be stabilized below 1.8°C, relative
to the preindustrial levels.
Coastal populations worldwide are already bracing for rising seas. However, 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.
Melting ice sheets are potentially the largest contributor to sea level change, and historically the hardest
to predict because the physics governing their behavior is notoriously complex. “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 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.
Using a new computer model, which captures for the first time the coupling between ice sheets, icebergs,
ocean and atmosphere, the team of 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.
“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” says Prof. Axel Timmermann, co-author of the study and Director of the IBS
Center for Climate Physics.
Ice sheets respond to atmospheric and oceanic warming in delayed and often unpredictable ways. Previously,
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. “However, according to our supercomputer
simulations, the effectiveness of these processes may have been overestimated in recent studies,” says Prof.
June Yi Lee from the IBS Center for Climate Physics and Pusan National University and co-author of the
study. “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,” she
adds.
The study highlights the need to develop more complex earth system models, which capture the 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.
“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,”
summarizes Axel Timmermann.
[Figure 1] Sea level rise contributions from the Antarctic and Greenland
ice sheets, and maps of projected 2150 CE Antarctic ice sheet surface elevation following different
greenhouse gas emission scenarios (SSP1-1.9, strong emission cuts; SSP2-4.5, medium emission cuts;
SSP5-8.5, weak emission cuts). / Figure credit by Jun-Young Park
Notes for editors
- Reference
Jun-Young Park, Fabian Schloesser, Axel Timmermann, Dipayan Choudhury, June-Yi Lee, and Arjun Babu
Nellikkattil, Future sea-level projections with a coupled atmosphere-ocean-ice-sheet model, Nature
Communications. doi: 10.1038/s41467-023-36051-9
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The IBS Center for Climate Physics (ICCP) at Pusan Nationalk University seeks to expand the frontiers of earth system science by conducting cutting-edge research into climate dynamics and utilizing high-performance computer simulations, with the goal of improving decadal Earth system forecasts and long-term projections. See more on http://ibsclimate.org