The wind power input to the ocean general circulation is usually calculated from the time-averaged wind products. Here, this wind power input is reexamined using available observations, focusing on the role of the synoptically varying wind. Power input to the ocean general circulation is found to increase by over 70% when 6-hourly winds are used instead of monthly winds. Much of the increase occurs in the storm-track regions of the Southern Ocean, Gulf Stream, and Kuroshio Extension. This result holds irrespective of whether the ocean surface velocity is accounted for in the wind stress calculation. Depending on the fate of the high-frequency wind power input, the power input to the ocean general circulation relevant to deep-ocean mixing may be less than previously thought. This study emphasizes the difficulty of choosing appropriate forcing for ocean-only models.

Submesoscale eddies are often seen in high‐resolution satellite‐derived ocean color images. To efficiently identify these eddies from surface chlorophyll data, here, we develop an automatic submesoscale eddy detection method and apply it to the South China Sea. The detected submesoscale eddies are found to have a radius of 13 ± 5 km and an aspect ratio of 0.5 ± 0.2, with a notable predominance of cyclones. Further investigation reveals that the surface structure of these eddies displays a unique “cat's‐eye” pattern, and the eddies become more circular with increasing eddy radius. Submesoscale eddies can strongly regulate surface chlorophyll via horizontal advection while they have less coherent signatures in sea surface temperature. These findings may help to improve submesoscale parameterizations in Earth system models.

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.

In this study we track and analyze eddy movement in the global ocean using 20 years of altimeter data and show that, in addition to the well-known westward propagation and slight polarity-based meridional deflections, mesoscale eddies also move randomly in all directions at all latitudes as a result of eddy–eddy interaction. The speed of this random eddy movement decreases with latitude and equals the baroclinic Rossby wave speed at about 25° of latitude. The tracked eddies are on average isotropic at mid- and high latitudes, but become noticeably more elongated in the zonal direction at low latitudes. Our analyses suggest a critical latitude of approximately 25° that separates the global ocean into a low-latitude anisotropic wavelike regime and a high-latitude isotropic turbulence regime. One important consequence of random eddy movement is that it results in lateral diffusion of eddy energy. The associated eddy energy diffusivity, estimated using two different methods, is found to be a function of latitude. The zonal-mean eddy energy diffusivity varies from over 1500 m² s⁻¹ at low latitudes to around 500 m² s⁻¹ at high latitudes, but significantly larger values are found in the eddy energy hotspots at all latitudes, in excess of 5000 m² s⁻¹. Results from this study have important implications for recently developed energetically consistent mesoscale eddy parameterization schemes which require solving the eddy energy budget.

Eddy energy generation and energy fluxes are examined in a realistic eddy-resolving model of the North Atlantic. Over 80% of the wind energy input is found to be released by the generation of eddies through baroclinic instability. The eddy energy generation is located near the surface in the subtropical gyre but deeper down in the subpolar gyre. To reconcile the mismatch between the depth of eddy energy production and the vertical structure of the horizontal dispersion of eddy energy, the vertical eddy energy flux is downward in the subtropical gyre and upward in the subpolar gyre.