Study predicts climate change will accelerate ocean currents


Ocean currents off the west coasts of North and Central America. Photo credit: NASA

An international team led by researchers from the Scripps Institution of Oceanography at UC San Diego, using computer model simulations, found that climate change is altering the mechanisms of surface ocean circulation, making it faster and thinner.

These changes can spread through the ocean and affect the transport of the nutrients that organisms need, as well as that of the microorganisms themselves. Faster currents can also affect the processes by which the ocean removes carbon and heat from the atmosphere, protecting the planet from excessive atmospheric warming.

“We were surprised to see that surface currents in more than three-quarters of the world’s oceans accelerate as we heat the sea surface,” said the study’s lead author Qihua Peng, who recently joined Scripps Oceanography as a postdoctoral researcher.

The study published April 20 in the journal scientific advances, sheds light on an underestimated force behind the speed of global ocean currents. It’s helping resolve a debate about whether currents are accelerating as a result of global warming.

Wind has been the main factor scientists have studied to describe and predict the speed of currents, but the research team used a global ocean model to simulate what will happen if sea surface temperatures also rise. They found that warming makes the top layers of water lighter. The increased density difference between these warm surface layers and the cold water below confines fast ocean currents to a thinner layer, causing surface currents to speed up in more than three-quarters of the world’s oceans. The increased speed of rotating ocean currents, known as gyres, has been associated with a slowing of the underlying ocean circulation. The team directly correlated the trend to the presence of ever-increasing concentrations of greenhouse gases in the atmosphere.

“Our study provides a way forward to study ocean circulation change and assess uncertainty,” said Shang-Ping Xie, climate modeller at Scripps Oceanography.

Currents are organized into eddies in most oceans bounded by continents. An exception is the Southern Ocean, which surrounds Antarctica. There, howling westerly winds make the Antarctic Circumpolar Current the largest transport volume in the world. Last year, ocean and space observations by Scripps scientists found that the Antarctic Circumpolar Current is speeding up.

“The accelerating Antarctic Circumpolar Current is exactly what our model predicts as global warming,” Xie said.

The study’s co-authors include Dongxiao Wang of Sun Yat-Sen University in China, scientists from the Chinese Academy of Sciences, the Woods Hole Oceanographic Institution in Massachusetts and UC Riverside.

Climate change is making one of the world’s strongest currents flow faster

More information:
Global acceleration of upper ocean currents caused by surface warming, scientific advances (2022).

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University of California – San Diego

Study predicts climate change will accelerate ocean currents (2022, April 20)
accessed April 20, 2022

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