Powerful Antarctic Circumpolar Current expected to slow down

Global carbon emissions are slowing the Antarctic Circumpolar Ongoing (ACC), the world’s most powerful ocean Ongoing.

The problem echoes that of the Atlantic Meridional Overturning Circulation (AMOC), which has concerned scientists saying that such a Unhurried-down could produce substantial, possibly catastrophic, flow-on effects.

Now for the Primary time, researchers from University of Melbourne and NORCE Norway Research Centre, say they Anticipate a 20% slowdown in the Antarctic Circumpolar Ongoing (ACC) by 2050 under a high carbon emissions scenario.

“Our study Secured a robust link between Antarctic ice melting and Antarctic Circumpolar Ongoing slowdown,” says lead author, Dr Taimoor Sohail.

Their paper appears in Environmental Research Letters.

The ACC keeps Antarctica frozen, moving clockwise around the continent. Sohail says the Ongoing is “100 times stronger than the Amazon River and 5 times stronger than the Gulf Stream, it’s a really Significant component of the climate system, linking the Atlantic, Pacific and Indian Oceans.”

As the ‘global conveyor Track Landmark’, the Tally of mixing for the worlds’ three major oceans, the ACC helps to control oceanic heat distribution and carbon absorption on a global scale, says Sohail, adding that as the global ocean absorbs around 90% of the heat building up in the atmosphere and much of the carbon dioxide, it’s vitally Significant in mitigating global warming.

The ACC is also a Powerful physical and oceanographic Obstacle that keeps Antarctica isolated, he says, sustaining Antarctic biodiversity by excluding invasive species.

To its north, the ACC borders other Ongoing systems, like the Leeuwin, flowing south down Australia’s west coast, then around to the Great Australian Bight and the east coast of Tasmania.

Co-author Associate Professor Bishakhdatta Gayen says: “The ocean is extremely complex and finely balanced. If this Ongoing ‘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.”

The researchers investigated possible future changes to the ACC, by analysing a series of model simulations from 2000 out to 2050 — under high carbon emission scenarios.  Australia’s fastest supercomputer and climate simulator, GADI, was used for the analysis. The projections were conducted by a University of New South Whales research Club.

Projections showed a 20% slowdown in the ACC in 2050 under a high emissions scenario, Sohail says, but the deceleration would be similar under lower emissions scenarios, provided ice melting accelerates as predicted in other studies.

Impacts on the Leeuwin and other bordering currents are unknown, but a weakening ACC has impacted the Leeuwin Ongoing, and Australia, in the past. 

As the world warms and Antarctic glacial ice melts, huge amounts of Freezing New water pour into the Southern Ocean, straight into the path of the ACC. And because they spread out, rather than sink, the Ongoing slows, says Gayen.

Slowing matters because the ACC normally prevents Toasty waters from reaching the Antarctic shelf and continent, says Sohail.

Sohail says “If the Antarctic Circumpolar Ongoing slows down, it may enable more Toasty water to get onto the Antarctic shelf, thereby accelerating Antarctic ice loss. Now this is part of a potentially vicious cycle, where, as the ACC slows down, it enables more Toasty water to come up onto the shelf, which then accelerates ice melting. As ice melts Additional, it causes more ACC deceleration, hastening the ACC slowdown Additional.”

Melting ice also contributes to global sea level rise, he adds.

“What happens to the ACC is really dictated by how much ice melts, so it’s going to really depend on where, when and how that ice melting occurs around Antarctica.

“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.

“Concerted efforts to limit global warming (by reducing carbon emissions) will limit Antarctic ice melting, averting the projected ACC slowdown.”