Scientists have warned that the deep ocean circulation around Antarctica could be at risk of collapse, severely impacting climate and marine ecosystems for centuries. The overturning circulation carries heat, carbon, oxygen, and nutrients around the globe, affecting climate, sea level, and the productivity of marine ecosystems. The circulation has remained relatively stable for thousands of years, but global carbon emissions are predicted to slow down significantly in the next few decades.

According to a new study coordinated by the ARC Centre for Excellence in Antarctic Science at UNSW Sydney and published in Nature, the Antarctic overturning will slow by over 40% in the next 30 years and is headed towards collapse if global carbon emissions continue at the current rate. The study modeled the amount of Antarctic deep water produced under the IPCC ‘high emissions scenario’ until 2050 and included the ocean processes that previous models had not been able to.

The collapse of the deep ocean circulation would stagnate the oceans below 4,000 meters, reducing the nutrients available to support marine life near the ocean surface. The model simulations also show that the slowing of the overturning leads to rapid warming of the deep ocean, which is already underway. The melt of the Antarctic and Greenland ice sheets is expected to continue accelerating as the planet warms, impacting the overturning circulation that regulates Earth’s climate.

The study’s authors warn of the profound effects the ocean’s overturning of heat, freshwater, oxygen, carbon, and nutrients will have on the oceans for centuries. “We are talking about the possible long-term extinction of an iconic water mass,” says Professor Matthew England, Deputy Director of the ARC Centre for Excellence in Antarctic Science.

References

• Li, Q., England, M. H., Hogg, A. McC., Rintoul, S. R., & Morrison, A. K. (2023). Abyssal ocean overturning slowdown and warming driven by Antarctic meltwater. Nature, 615(7954), 841–847. https://doi.org/10.1038/s41586-023-05762-w
• Lyne, M. (2023, March 30). Deep ocean currents around Antarctica headed for collapse, study finds [Text]. UNSW Newsroom; University of New South Wales Sydney. https://newsroom.unsw.edu.au/news/science-tech/deep-ocean-currents-around-antarctica-headed-collapse-study-finds