Widespread mesoscale dipoles in the global ocean

Mesoscale eddies are ubiquitous and energetic features in the ocean. Although eddies are known to form dipoles from time to time, it is unclear how often they do so. Using satellite altimetry data, here we show that mesoscale dipoles are surprisingly widespread in the global ocean. About 30–40% of the mesoscale eddies identified in altimeter data are paired up as dipoles, and the percentage is even higher in energetic regions such as the Gulf Stream and the Southern Ocean. Composite analysis involving Argo float data further reveals that these mesoscale dipoles have a relatively uniform three-dimensional structure. We find that the presence of mesoscale dipoles can strongly enhance wind Ekman pumping velocity and lead to deep-reaching vertical motions inside the dipoles via eddy deformation and frontogenesis. Such strong vertical exchanges promoted by mesoscale dipoles may play an important role in regulating the Earth's biogeochemical processes.