Winds are picking up worldwide, and that is making the surface waters of the oceans swirl a bit faster, researchers report. A new analysis of the ocean’s kinetic energy, measured by thousands of floats around the world, suggests that surface ocean circulation has been accelerating since the early 1990s.
Some of that sped-up circulation may be due to naturally recurring ocean-atmosphere patterns, such as the Pacific Decadal Oscillation, researchers report February 5 in Science Advances. But the acceleration is greater than can be attributed to natural variability alone — suggesting that global warming may also be playing a role, says a team led by oceanographer Shijian Hu of the Chinese Academy of Sciences in Qingdao.
The connected system of massive currents that swirl between the world’s oceans, sometimes called the Great Ocean Conveyor Belt, redistributes heat and nutrients around the globe and has a powerful effect on climate. Winds dominate mixing in the surface ocean: Prevailing winds in the tropics, for example, can push water masses aside, allowing deeper, nutrient-rich waters to surge upward.
In the deeper ocean, differences in water density due to salt and heat content keep the currents flowing (SN: 1/4/17). For example, in the North Atlantic Ocean, surface currents carry heat north from the tropics, helping to keep northwestern Europe warm. As the waters arrive at the Labrador Sea, they cool, sink and then flow southward, keeping the conveyor belt humming along.