Irreversible loss of ice sheets imminent past 1.8°C warming

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, compared to preindustrial levels. That finding was published in Nature Communications by an international team of scientists, including Fabian Schloesser, researcher at the University of Hawaiʻi at Mānoa School of Ocean and Earth Science and Technology.

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.

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.

"The model used in our study captures for the first time the coupling between ice sheets, icebergs, ocean and atmosphere, which is important for improving future sea-level projections and understanding of the underlying processes," said Schloesser.

 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 sixth assessment report of the Intergovernmental Panel on Climate Change do not agree on how quickly the major ice sheets will respond to global warming.

"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," said Jun Young Park, doctoral student at the IBS Center for Climate Physics and Pusan National University, Busan, South Korea and first author of the study.

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.

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," said Timmermann.

https://www.hawaii.edu/news/2023/02/14/irreversible-loss-of-ice-sheets/