Huge ocean whirlpools, some hundreds of miles across, are affecting Earth's climate in ways that scientists can't yet predict.
Called mesoscale eddies, the 60- to 300-mile (100-500 kilometer) wide whirlpools move as much water as ocean currents, say researchers who reviewed satellite data from 1992 to 2010.
The eddies form as ocean currents are disrupted by ocean features like islands. As they move west due to the Earth's rotation, they can drive 30 tons of water every second to the east coast of continents.
Bo Qiu from the University of Hawaii and colleagues say the eddies may grow and become more frequent as the world warms.
"The amount of water they can carry westward was a huge surprise," Qiu told New Scientist.
Eddy-driven currents are likely making extreme weather across Japan worse, Wenju Cai from CSIRO in Melbourne, Australia, told New Scientist. The Kuroshio current's warm waters cause extreme weather, and the eddies hold more warm water.
The findings were reported in the journal Science.