deep ocean currents around Antarctica that are vital to marine life have dropped by 30% since the 1990s and could soon stop entirely, according to a new study.
These currents, known as Antarctic bottom waters, are driven by cold, dense water from the Antarctic continental shelf which sinks to depths below 10,000 feet (3,000 meters). The water then spreads north into the eastern Pacific and Indian oceans, feeding a network of currents called the global meridional overturning circulation and supplying fresh nutrients and oxygen to 40% of the world’s deep oceans.
But rising global temperatures are unlocking large volumes of less-dense freshwater from the Antarctic ice shelves, slowing this circulation.
“If the oceans had lungs, this would be one of them” matthew englandprofessor of ocean and climate dynamics at the University of New South Wales in Sydney, Australia, who contributed to the research, said in a statement. Researchers from the UK and Australia collaborated on a study published in March in the journal Nature which predicted a 40% reduction in the strength of the Antarctic bottom waters by 2050.
He also warned that the currents could eventually stop completely. “We’re talking about the possible long-term extinction of an iconic body of water,” England said.
In a new study published Thursday (May 25) in the journal Nature Climate ChangeEngland and his colleagues say they have confirmed these predictions with real-life observations in the Australian Antarctic Basin, which spans the polar waters between Australia and Antarctica.
Related: How an ocean hidden under the Antarctic ice circulates
The researchers examined changes in the amount of bottom water entering the basin between 1994 and 2017 and recorded a 30% reduction in velocity, suggesting that these deep or abyssal ocean currents are beginning to stagnate.
Decreased circulation around Antarctica could slow down the global network of deep-sea currents and trap nutrients and oxygen in the deep ocean, with knock-on effects for marine life and productivity.
“The thing about the oceans is that all the marine life that we have on the surface, when it dies, sinks to the bottom of the ocean, so there’s a lot of nutrient-rich water in the ocean abyss,” England. he said in a video Produced by the Australian Academy of Sciences. “If we slow down the overturning circulation that brings bottom water to the surface, we cut off the way nutrients return to the surface to regenerate marine life.”
About 276 trillion tons (250 trillion metric tons) of cold, salty, oxygen-rich water sinks around Antarctica each year, according to the new study. In a warmer climate, fresh meltwater reduces the density of this sinking mass, meaning more of it remains in the upper layers of the ocean. “These regions supply the deep waters of the entire Pacific and eastern Indian basins, so it is likely that the changes quantified here affect a large fraction of the global deep ocean,” the researchers wrote.
The scientists warned that freshwater entering Antarctic waters is likely to continue and accelerate in the coming decades, meaning these vital currents could soon collapse. “Such profound changes in ocean heat, fresh water, oxygen, carbon and nutrients will have significant impacts on the oceans for centuries to come,” England said.
The new findings reinforce dramatic estimates the researchers made earlier this year, they said. ariane purichresearcher at Monash University’s School of Earth, Atmosphere and Environment in Australia who was not involved in the research.
“This new study is important because, together with a recent historical modeling study, it provides further support, including observational evidence, that the melting Antarctic ice sheet and shelves will impact global ocean circulation, with major impacts.” in the absorption of heat and carbon by the oceans”. Purich told Australia Science Media Exchange.
