Melting Antarctic ice sheets are slowing Earth’s strongest ocean current, researchers claim (with caveats)

Southern Ocean surrounds Antarctica [image credit: theozonehole.com]

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Just as Atlantic ocean (AMOC) scares are sinking below the waves, climate modellers are using the discredited high emissions scenario (RCP5-8.5) to make assertions of possible future unwelcome happenings in the Antarctic seas that are by definition of that scenario unlikely. Their paper says: ‘Our results show that, by 2050, the strength of the ACC declines by ∼20% for a high-emissions scenario.’ A further claim is that their predictions could happen anyway under a low emissions scenario, but might take longer. Of course all this rests on how useful their models are, and how well (or poorly?) they’re able to reflect natural climate variation. Looking at the paper itself, it ends by saying: ‘Note that the simulations explored in this study have some important caveats. First, the ocean-sea ice model explored is not coupled to an atmosphere or ice sheet model. As a result, key feedbacks may be missing.’ Worth a look here to see what the other caveats are.
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Melting ice sheets are slowing the Antarctic Circumpolar Current (ACC), the world’s strongest ocean current, researchers have found.

This melting has implications for global climate indicators, including sea level rise, ocean warming and viability of marine ecosystems, says Phys.org.

Researchers from the University of Melbourne and NORCE Norway Research Center, have shown the current slowing by around 20% by 2050 in a high carbon emissions scenario. The work is published in the journal Environmental Research Letters.

This influx of fresh water into the Southern Ocean is expected to change the properties, such as density (salinity), of the ocean and its circulation patterns.

University of Melbourne researchers, fluid mechanist Associate Professor Bishakhdatta Gayen and climate scientist Dr. Taimoor Sohail, and oceanographer Dr. Andreas Klocker from the NORCE Norwegian Research Center, analyzed a high-resolution ocean and sea ice simulation of ocean currents, heat transport and other factors to diagnose the impact of changing temperature, saltiness and wind conditions.

Associate Professor Gayen said, “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.”
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More than four times stronger than the gulf stream, the ACC is a crucial part of the world’s “ocean conveyor belt,” which moves water around the globe—linking the Atlantic, Pacific and Indian Oceans—and is the main mechanism for the exchange of heat, carbon dioxide, chemicals and biology across these ocean basins.

The researchers used Australia’s fastest supercomputer and climate simulator, GADI, located at Access National Research Infrastructure in Canberra. The underlying model (ACCESS-OM2-01) has been developed over a number of years by Australian researchers from various universities.

The projections explored in this analysis were conducted by a research team based at UNSW, who found that the transport of ocean water from the surface to the deep may also slow in the future.

Dr. Sohail said it is predicted that the slow-down will be similar under the lower emissions scenario, provided ice melting accelerates as predicted in other studies.

Full article here.
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Image: Southern Ocean surrounds Antarctica [credit: theozonehole.com]
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Study: Decline of Antarctic Circumpolar Current due to polar ocean freshening (March 2025)