World's strongest ocean current becoming weaker due to melting Antarctic ice: Study
Recent studies show the melting ice sheets surrounding Antarctica are having repercussions on the Antarctic Circumpolar Current (ACC), the world's strongest ocean current. This change could perturb integrated climate systems on a global scale, altering sea levels, ocean temperatures, or even marine ecosystems.
According to a study conducted by the University of Melbourne and NORCE Norway Research Centre, if carbon emissions are not controlled, the ACC may decelerate by up to 20% by 2050. Increases in freshwater due to melting ice are changing patterns of saltiness and circulation in the ocean, and this is affecting the balance that allows currents to circulate around the globe.
'The ocean is extremely complex and finely balanced. If this current 'engine' breaks down, there could be severe consequences, including more climate variability, with greater extremes in certain regions, and accelerated global warming due to a reduction in the ocean's capacity to act as a carbon sink,' said Bishakhdatta Gayen, one of the study authors.
The ACC is a major player in the world's ocean movement, acting as a key component of the "ocean conveyor belt," responsible for maintaining the movement of water between the Atlantic, Pacific, and Indian Oceans. Furthermore, it assists in climate control, including the distribution of heat, carbon dioxide, and nutrients to different ocean basins.
The ACC is over four times as powerful as the Gulf Stream. As a result, the ACC significantly controls the migration of a number of species across the ocean. With the current weakening, there is a potential risk of certain species, such as bull kelp, shrimps, and mollusks, invading the Antarctic waters and putting the fragile ecosystems and food chains in grave danger.
The possible shifts in available prey could affect the population of penguins, thereby affecting the biodiversity of the entire region.
Researchers analyzed these microdetails through Australia's fastest supercomputer, GADI, using which they simulated the ocean currents and climatic changes. The model incorporated the change in monsoon patterns, intake of saline water, and other free atmospheric wind conditions to determine the ice melt effect on oceanic circulation.
These findings contradict earlier research that said that the ACC had been accelerating owing to the growing range in temperature across oceanic latitudinal regions. The study's major finding, instead, was that large quantities of freshwater from melting ice sheets reduce the ocean's salinity, which weakens the process that drives cold, dense water to sink and circulate—a key mechanism behind ACC strength.
The research reveals it isn't just the high emissions scare – even in a scenario predicated on weaker emissions where the ice continues to melt. The severity of change is still imminent.
'The 2015 Paris Agreement aimed to limit global warming to 1.5 degrees Celsius above pre-industrial levels. Many scientists agree that we have already reached this 1.5-degree target, and it is likely to get hotter, with flow-on impacts on Antarctic ice melting,' said Taimoor Sohail, one of the study authors.
The scientists believe that there is more work required, such as climatograph modeling and animation simulations, to consider the complete ACC slowdown effects caused by climate change.
'Ocean models have historically been unable to adequately resolve the small-scale processes that control current strength. This model resolves such processes, and shows a mechanism through which the ACC is projected to actually slow down in the future. However, further observational and modelling studies of this poorly-observed region are necessary to definitively discern the current's response to climate change,' concluded Gayen.
The study has been published in Environmental Research Letters.
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