The melting of the Antarctic ice sheet is weakening the ACC ocean current, which is an important ocean current that regulates global climate and ocean circulation. Scientists predict that ocean currents will slow down by 20% by 2050, which will exacerbate climate extremes, damage marine ecosystems, and reduce the ocean's ability to absorb carbon. Weakened ocean currents could also allow invasive species to reach Antarctica, changing its food web.
New research finds that melting ice sheets are causing the world's most powerful ocean current, the Antarctic Circumpolar Current (ACC), to slow down.
This slowdown could have profound consequences for global climate, affecting sea level rise, ocean temperatures and marine ecosystems.
Scientists from the University of Melbourne and Norway's NORCE research center estimate that the ACC could weaken by about 20% by 2050 under high carbon emissions scenarios.
Freshwater inflows from melting ice and snow are expected to change the ocean's salinity and density, disrupting circulation patterns in the Southern Ocean.
To understand these changes, the researchers, including Associate Professor Bishakhdatta Gayen, Dr Taimoor Sohail and Dr Andreas Klocker, used high-resolution ocean and sea ice simulations. Their analysis looked at how changes in temperature, salinity and wind conditions affect ocean currents and heat transport.
Associate Professor Guyon said: "The ocean is extremely complex and delicately balanced. If this current 'engine' fails, it could have serious consequences, including a more variable climate, more severe extreme weather in some areas, and accelerated global warming due to a reduced ability of the ocean to act as a carbon sink."
The ACC is a barrier that prevents invasive species (such as southern bull kelp rafts riding ocean currents) or marine animals (such as shrimp or molluscs) from entering Antarctica from other continents.
As the ACC slows and weakens, these species are more likely to move into the fragile Antarctic continent, causing potentially severe impacts on the food web, potentially altering what Antarctic penguins eat, for example.
The ACC is an important part of the world's "ocean conveyor belt", which is more than four times stronger than the Gulf Stream. It transports seawater around the world, connecting the Atlantic, Pacific and Indian oceans, and is the main mechanism for the exchange of heat, carbon dioxide, chemicals and organisms between these ocean basins.
The researchers used Australia's fastest supercomputer and climate simulator, GADI, located at the Access National Research Infrastructure in Canberra. The base model (ACCESS-OM2-01) was developed over several years by researchers from several Australian universities.
A team of researchers from the University of New South Wales, who examined the predictions in this analysis, found that the transport of seawater from the surface to the deeper layers may also slow down in the future.
Dr Suhail said it was predicted that if ice melt were to accelerate as predicted by other studies, then the slowdown would be similar under lower emissions scenarios.
"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 the 1.5 degree target and are likely to get hotter, with knock-on effects on Antarctic ice melt," Dr Sohail said. "A concerted effort to limit global warming (by reducing carbon emissions) will limit Antarctic ice melt and avoid the projected climate slowdown in the Arctic Circle."
The study, published today (March 3) in Environmental Research Letters, reveals that the impact of melting ice and warming oceans on the terrestrial climate committee (ACC) is much more complex than previously thought.
"Melting ice sheets pump huge amounts of fresh water into the Aral Sea." Associate Professor Guyon said: "Such a sudden change in the ocean's 'salinity' would have a number of consequences - including a weakening of the sinking of surface water into the deep ocean (known as Antarctic bottom water) and, according to this study, a weakening of the powerful ocean jets that surround Antarctica."
He said the new research contrasts with previous research, which suggested that ACC may be accelerating as climate change increases temperature differences at different latitudes in the ocean.
"Ocean models have historically failed to adequately resolve the small-scale processes that control ocean current strength. This model resolves these processes and shows the mechanisms that predict actual slowdowns in the ACC in the future. However, further observational and modeling studies in this less-observed region are necessary to clarify the response of water flows to climate change."
Compiled from /ScitechDaily