May 27, 2024

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Scientists have warned that crucial Antarctic ocean circulation is poised to collapse if pollution from a warming planet remains high.

Scientists have warned that crucial Antarctic ocean circulation is poised to collapse if pollution from a warming planet remains high.

Brisbane, Australia (CNN) The melting of Antarctic ice is not fair Raising sea levels A new study warns of slowing circulation of deep ocean waters with huge implications for global climate and marine life.

Led by scientists from the University of New South Wales and published on Wednesday in the peer-reviewed journal Nature Stady Modeling the effect of melting Antarctic ice on deep ocean currents that operate the flow of nutrients from the sea floor to fish near the surface.

Three years of computer modeling found that the Antarctic circulation – also known as the abyssal ocean overturn – is on track to slow 42% by 2050 if the world continues to burn fossil fuels and produce high levels of planet heat pollution.

The slowdown is expected to accelerate the melting of ice and potentially end the ocean system that has helped sustain life for thousands of years.

“The projections we’ve made look like the Antarctic coup will collapse this century,” said Matthew England, deputy director of the Australian Research Council’s Center of Excellence in Antarctic Sciences, which coordinated the study.

“In the past, these fluctuations have changed over a thousand years or so, and we’re talking about changes in a few decades. So it’s very dramatic,” he said.

Most of the previous studies focused on Atlantic meridian overturning (AMOC) rotation, A system of currents that carry warm water from the tropics to the North Atlantic Ocean. Then the cold, salty water sinks and flows south.

Its counterpart in the Southern Ocean has been less studied but does an important job of transporting nutrient-dense water north from Antarctica, past New Zealand to the North Pacific, North Atlantic and Indian Oceans, the report’s authors said in a press briefing.

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Circulation of deep ocean water is vital to the health of the sea – and plays an important role in sequestering the water Carbon is absorbed from the atmosphere.

According to the report, while a slowing AMOC will mean that the depths of the Atlantic Ocean will become cooler, the slower circulation of dense Antarctic waters will mean that the deepest waters of the Southern Ocean will warm.

“One of the concerns about this slowdown is that there could be feedbacks of increased ocean warming at the base of the ice shelves around Antarctica. This would lead to more ice melting, reinforcing or amplifying the original change,” England said.

How it works

The surface of the ocean around Antarctica freezes in the winter and melts again in the summer.

Scientists said that as global temperatures rise, Antarctic ice is expected to melt faster, but that doesn’t mean deep water circulation will increase – quite the opposite is true.

In a healthy system, the consistency of cold and salty — or dense — allows melting Antarctic ice to sink into the deepest layer of the ocean. From there it sweeps north, bringing carbon and higher levels of oxygen than would be present in the water 4,000 meters below.

Scientists said that as the current moves north, it stirs up deep layers of debris on the ocean floor — the decaying remains of nutrient-dense marine life — that feed the bottom of the food chain.

England said that in certain areas, mostly southern Australia in the Southern Ocean and in the tropics, this cold, nutrient-rich water moves toward the surface in a process called uplift, distributing the nutrients to the upper layers of the ocean.

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However, a study on Wednesday found that as global temperatures rise, melting sea ice “refreshes” the waters around Antarctica, softening the water’s salinity and raising its temperature, which means it’s less dense and doesn’t sink to the bottom as efficiently as it once did.

The co-author of the report, Steve Rintoul of the Australian Commonwealth Scientific and Industrial Research Organization and the Australian Antarctic Program Partnership, said marine life in waters around the world depends on nutrients returning to the surface, and that the Antarctic upturn is a key component of this. nutrient flow.

“We know that nutrients exported from the Southern Ocean in other current systems support about three-quarters of global phytoplankton production – the base of the food chain,” he said.

“We have shown that the sinking of dense waters near Antarctica will decrease by 40% by 2050. Sometime between 2050 and 2100 we will start to see the effects of this on surface productivity.”

England added, “People born today will be around then. So, these things are certainly going to challenge societies in the future.”

Climate change warning

Fishing boats at a floating fish farm off Rongcheng, China.

The report’s authors say the slowing of the Antarctic Ocean’s overturning has other indirect effects on the planet – for example, it could alter rain ranges in the tropics by up to 1,000 km (621 miles).

“Shut it off completely and you get this decrease in precipitation in one range south of the equator and an increase in range to the north. So we can see effects on precipitation in the tropics,” England said.

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earlier this month, Intergovernmental Panel on Climate Change In its latest report, the Intergovernmental Panel on Climate Change warned that the effects of rising global temperatures are more severe than expected. She added that without immediate and profound changes, the world is heading towards dangerous and irreversible consequences of climate change.

The IPCC report finds that the goal of limiting global warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels remains achievable, but becomes more difficult to achieve the more the world fails to cut carbon pollution.

England points out that the IPCC’s forecasts do not include melting ice from Antarctic ice sheets and shelves.

“This is a very important component of the change already under way around Antarctica, with more to come in the next few decades,” England said.

Rintoul said the study was yet another urgent warning on top of all that preceded it.

“While a direct impact on fisheries through reduced nutrient supply may take decades to materialize, we will commit ourselves to that future through the choices we make over the next decade.”