The Antarctic Circumpolar Current (ACC), the only ocean that circles the planet, is speeding up. Scientists are now able to tell that this is happening by taking advantage of a decades long set of observational records.
Researchers used satellite measurements of sea-surface height and data collected by the global network of ocean floats called Argo to detect a trend in Southern Ocean upper layer velocity that has been hidden to scientists until now.
Westerly winds have sped up as climate warms. Models show that the wind speedup does not alter the ocean currents much. Rather, it energizes ocean eddies, which are circular currents of water running counter to main currents.
“From both observations and models, we find that the ocean heat change is causing the significant ocean current acceleration detected during recent decades,” said Jia-Rui Shi, formerly a Ph.D. student at Scripps Oceanography.
The ACC encircles Antarctica and separates cold water in the south from warmer subtropical water to its north. When the gradient, or amount of heat difference, between cold and warm waters increases, currents between those two masses speed up.
“The ACC is mostly driven by wind, but we show that changes in its speed are surprisingly mostly due to changes in the heat gradient,” said co-author Lynne Talley.
https://phys.org/news/2021-11-climate-world-strongest-currents-faster.html