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“Freshwater release in this region not only directly inhibits deep-water formation — essential for maintaining the strength of the AMOC — but also alters atmospheric circulation patterns,” Ma said. A reduction in the amount of water sinking in the Irminger Sea likely has greater impacts on the global climate than reductions of the same kind in other northern seas, Ma said.
The Irminger Sea has a disproportionate influence on the strength of the AMOC because it regulates the amount of water sinking to form deep currents in nearby seas through atmospheric processes, Ma said. Freshwater input into the Irminger Sea enhances freshwater flow into the Labrador Sea between southwestern Greenland and the coast of Canada, for example, so a reduction in deep-current formation in the Irminger Sea has knock-on effects for deep-current formation across the entire North Atlantic.
Ma and his colleagues examined the impact of meltwater on the AMOC using a climate model that simulated an increase in freshwater input in four regions — the Irminger Sea, the Labrador Sea, the Nordic Seas and the Northeast Atlantic. The researchers were able to tease out the sensitivity of the AMOC to meltwater in each region, then identified specific changes in the global climate linked to each scenario. The team published its findings Wednesday (Nov. 20) in the journal Science Advances.
Animation showing the path of ocean currents forming the AMOC and deep-water formation in the North Atlantic. (Image credit: NASA/Goddard Space Flight Center Scientific Visualization Studio)
The role of the Irminger Sea for the AMOC outweighed that of the three other regions in the model and triggered stronger climate responses. Reduced deep-water formation led to widespread cooling in the Northern Hemisphere, as well as Arctic sea ice expansion, because warm water wasn’t being brought up from the south.
The simulation also showed slight warming in the Southern Hemisphere and bolstered previous findings that a weaker AMOC would throw tropical monsoon systems into chaos.
The model confirmed findings from previous research, but it also held surprises, Ma said. Hidden within hemisphere-scale climate shifts, the researchers discovered climate extremes at much more localized scales. These included seasonal extremes in precipitation across North America and the Amazon Basin that varied depending on which region of the North Atlantic meltwater was added into.
“While the general climate impacts … were broadly anticipated, the behavior of climate extremes was not,” Ma said. Incorporating these extremes into climate models and recognizing that the location of meltwater input matters could help scientists better predict the impacts of a weakened AMOC, he said.
Forecasting AMOC behavior is becoming increasingly urgent as scientists warn we are nearing a tipping point. “These insights are critical for informing policy makers and climate experts in developing targeted strategies to mitigate and adapt to climate impacts,” Ma said.
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Publish date : 2024-11-29 02:00:00
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