Science & Technology

Current Climate Model Simulations Significantly Overestimate Future Sea-Level Rise

Wrong Sea Level Concept

The melting charge of the Antarctic ice sheet is principally managed by the rise of ocean temperatures surrounding Antarctica. Utilizing a brand new, higher-resolution local weather mannequin simulation, scientists from Utrecht College discovered a a lot slower ocean temperature enhance in comparison with present simulations with a coarser decision. Consequently, the projected sea-level rise in 100 years is about 25% decrease than anticipated from the present simulations. These outcomes had been printed within the journal Science Advances.

Estimates for future sea-level rise are based mostly on a big ensemble of local weather mannequin simulations. The output from these simulations helps to know future local weather change and its results on the ocean stage. Climate researchers regularly intention to enhance these fashions, for instance through the use of a a lot greater spatial decision that takes extra particulars into consideration. “Excessive-resolution simulations can decide the ocean circulation way more precisely,” says Prof. Henk Dijkstra. Collectively together with his PhD candidate René van Westen, he has been finding out ocean currents in high-resolution local weather mannequin simulations over the previous few years.

The brand new high-resolution mannequin takes into consideration ocean eddy processes. An eddy is a big (10 – 200 km) swirling and turbulent characteristic within the ocean circulation, which contributes to the transport of warmth and salt. Including ocean eddies into the simulation results in a extra reasonable illustration of the ocean temperatures surrounding Antarctica, which is essential for figuring out the mass lack of the Antarctic ice sheet. “The Antarctic ice sheet is surrounded by ice cabinets which cut back the movement of land ice into the ocean,” Van Westen explains. “Increased ocean temperatures round Antarctica enhance the melting of those ice cabinets, leading to an acceleration of land ice into the ocean and consequently resulting in extra sea-level rise.”

The present local weather mannequin simulations, which don’t take ocean eddies into consideration, venture that the ocean temperatures round Antarctica are rising beneath local weather change. The brand new high-resolution simulation exhibits fairly totally different conduct and a few areas close to Antarctica even cool beneath local weather change. “These areas look like extra resilient beneath local weather change,” says Van Westen. Dijkstra provides: “One obtains a really totally different temperature response as a result of ocean-eddy results.”  

The brand new high-resolution mannequin tasks a smaller mass loss because of ice-shelf soften: just one third in comparison with present local weather fashions. This reduces the projected international sea-level rise by 25% within the upcoming 100 years, Van Westen mentions. “Though sea ranges will proceed to rise, that is excellent news for low-lying areas. In our simulation, ocean eddies play an important function in sea-level projections, exhibiting that these small-scale ocean options can have a worldwide impact.” It took the crew about one yr to finish the high-resolution mannequin simulation on the nationwide supercomputer at SURFsara in Amsterdam. Dijkstra: “These high-resolution fashions require an immense quantity of computation, however are beneficial as they reveal smaller-scale bodily processes which needs to be taken into consideration when finding out local weather change.”

Reference: “Ocean eddies strongly have an effect on international imply sea-level projections” by René M. van Westen and Henk A. Dijkstra, 9 April 2021, Science Advances.

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