Item Information
- Author, Tom Houston
- Rolle, from BBC News in Sydney
2 hours ago
Rapid melting of ice in Antarctica is causing deepsea currents to slow drastically and could have catastrophic effects on climate, warns a new report compiled by a team of Australian scientists.
The deep water currents that drive ocean currents could decline by 40% by 2050, according to the study.
These flows carry vital heat, oxygen, carbon, and nutrients around the globe.
Previous research suggests that slowing North Atlantic currents could cause Europe to get colder.
The new study, published in the journal Nature, also warns that the slowdown could reduce the ocean’s ability to absorb carbon dioxide from the atmosphere.
The report describes how the Earth’s network of ocean currents is driven in part by the downward movement of cold, dense salt water toward the seafloor near Antarctica.
But as freshwater from the ice cap melts, seawater becomes less salty and less dense, and the downward movement slows.
These deepsea currents, or upheavals, have remained relatively stable in the northern and southern hemispheres for thousands of years, scientists say, but are now being affected by global warming.
“Our model shows that if global carbon emissions remain at current levels and on a trajectory that is expected to collapse, Antarctica’s overturning will decline by more than 40% over the next 30 years,” said Matthew England, an oceanographer from the University of New South Wales in Sydney, who led the study.
“If the oceans had lungs, this would be one of them,” he added.
Adele Morrison, who contributed to the report, explained that as ocean circulation slowed, surface water quickly reached its capacity for carbon storage and was not replaced by carbonunsaturated water from greater depths.
The 2018 Atlas study showed that the Atlantic Ocean’s circulatory system was weaker than it had been in over 1,000 years and had changed significantly over the past 150 years.
The paper suggested that changes in the Atlantic Meridional Overturning Circulation (Amoc) could cool the ocean and northwestern Europe and affect deepsea ecosystems.
A fictionalized account of the AMOC failure was featured in the climate disaster film The Day After Tomorrow (2004).
But according to Morrison, a slowdown in the overturning in the south would have greater impacts on marine ecosystems and Antarctica itself.
“The overturning brings nutrients up, which go down as organisms die…to replenish the global ecosystem and fisheries with nutrients,” she tells the BBC.
“The other big impact it could have is feedback on how much Antarctica will melt in the future. That paves the way for warmer water, which could lead to an increase in melting, which would be an additional feedback, bringing more meltwater into the ocean and decreasing the orbital velocity even more,” he adds.
The scientists spent 35 million computational hours over two years to create their models, which suggest that deepwater circulation in Antarctica could be reduced to twice the rate of decline in the North Atlantic.
“[É] impressive that this is happening so quickly,” said climatologist Alan Mix of Oregon State University in the US, coauthor of the most recent assessment by the Intergovernmental Panel on Climate Change (IPCC).
“Looks like it’s starting now. These are headlines,” he told Portal.
The effects of Antarctic meltwater on ocean currents are not yet included in the IPCC climate change models, but will be “significant,” according to Matthew England, author of the study.