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Scientists Link Southern Ocean's Rapid Warming to Human Activity

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In the past few decades, the Southern Ocean surrounding Antarctica has gotten less salty and has warmed at roughly twice the rate of global oceans overall.

Now, in a new study, scientists found convincing evidence that these trends are the result of two human influences: climate change from greenhouse gas emissions and the depletion of the ozone layer.


The research, published this week in the journal Nature Geoscience, was authored by scientists from Environment and Climate Change Canada and the Scripps Institution of Oceanography in California.

Using climate models, data from the Argo global network of floating ocean sensors and past records, the researchers determined that Antarctica's warming and freshening waters are directly linked to ozone depletion and greenhouse gas emissions, as opposed to natural variabilities.

This is the first time such a connection has been found specifically for the Southern Ocean, lead author Neil Swart of Environment and Climate Change Canada told Canada's National Observer.

"While the influence of ozone depletion and greenhouse gas increases on the Southern Ocean have been suggested for some time, our research provides the evidence that links the observed changes to these mechanisms, and defines their relative importance," Swart said in a press release for the study.

The 1987 Montreal Protocol, an international effort to ban chlorofluorocarbons, has led to significant recovery of the Antarctic ozone hole. On the other hand, global greenhouse gas emissions from fossil fuels and other industries have risen dramatically since the industrial revolution.

"Moving forward, the ozone layer is recovering while greenhouse gases are continuing to increase, leading to opposing trends," Swart added. "Our work suggests that greenhouse gases are more important than ozone in determining Southern Ocean trends."

As so-called "carbon sinks," our oceans are key to mitigating the effects of climate change. The Southern Ocean is one of the most prolific carbon sinks, taking in nearly half the total amount of anthropogenic CO2 absorbed by the world's oceans.

But as the ocean's ability to absorb CO2 decreases, global temperatures could increase and lead to greater weather extremes such as heat waves and stronger precipitation events, Swart explained to the National Observer.

"It is vital to understand changes in the Southern Ocean because it is a key region of global heat and carbon uptake, and it underlies ice sheets with many meters of sea-level rise potential," Swart said in the press release.

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