Study identifies main causes of change in ocean circulation

PICTURE: The variability of ocean currents is influenced by multiple factors. view After

Credit: Prof Helen Johnson

Researchers have identified key factors influencing a vital model of ocean currents.

The southern Atlantic overturning circulation (AMOC) carries warm water from the tropics to the north.

Many scientists believe that this heat transport makes regions like northwestern Europe and the UK warmer than they would otherwise be.

Climate models suggest that AMOC is likely to weaken over the next several decades, with broad implications for regional and global climate.

The new study – led by the universities of Exeter and Oxford, and published in Geoscience of nature – identify the causes of monthly and annual variations in AMOC and find a different picture in two key places.

Observational data came from extensive networks of surveillance equipment – off the coasts of Florida and Africa, and in the North Atlantic between Greenland and Scotland – managed by the international RAPID and OSNAP projects.

“Understanding the variability of AMOC is difficult because circulation is influenced by multiple factors which all vary and whose overlapping effects persist for years,” said lead author Dr Yavor Kostov of the Department of Geography. from the University of Exeter.

“Our results reveal the vital role of winds in driving changes in this ocean circulation.

“Winds were a key factor in both the subtropics and subpolar regions that we examined.

“As the climate continues to change, more effort should be focused on monitoring these winds – particularly in key regions on the continental borders and on the east coast of Greenland – and understanding what is causing them. leads.

While AMOC variability off the southern United States is dominated by the impact of winds, variability in the North Atlantic is generated by the combined effects of winds, heat, and water anomalies. sweet. “Our reconstruction suggests that, compared to subtropics, the reversal of circulation in the subpolar North Atlantic is more sensitive to changes in the ocean bottom state such as shifts in sites of deep convection,” Dr Kostov said.

“This implies that future climate change could alter the annual variability of AMOC in this region. It highlights the need to continuously observe the subpolar North Atlantic Ocean.”

The study also finds that changes in surface temperature and salinity near Canada and Greenland can trigger a delayed, remote impact on the Atlantic circulation as far south as Florida.

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Funding for this study came from the UK Natural Environment Research Council, the National Science Foundation, the National Oceanic and Atmospheric Administration, NASA and the Simons Foundation in the United States.

The paper, published in the journal Geoscience of nature, is titled: “Distinct sources of interannual subtropical and subpolar variability of the stunning Atlantic”.

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