A team of researchers at Scripps Institution of Oceanography at UC San Diego used computer simulations to show that climate change is altering the workings of surface ocean circulations, making them become faster and thinner.
These changes affect the transport of the nutrients organisms need as well as that of microorganisms themselves. Faster currents may also affect the processes by which the ocean removes carbon and heat from the atmosphere.
“We were surprised to see that surface currents speed up in more than three-fourths of the world’s oceans when we heated the ocean surface,” said lead author Qihua Peng.
Wind has been a key factor scientists have studied to describe and predict the speed of currents, but the research team used a global ocean model to simulate what happens when sea surface temperatures are also increased. They discovered that warming makes the topmost layers of water become lighter. The increased density difference of the warm surface layers from the cold water beneath limits the swift ocean currents to a thinner layer, causing the surface currents to speed up in more than three-fourths of the world’s oceans. The increased speed of rotating ocean currents called gyres was associated with a slowdown of ocean circulation underneath. The team directly linked the trend to the presence of ever-increasing levels of greenhouse gases in the atmosphere.