Evolution of Submesoscale Ageostrophic Motions through the Life Cycle of Oceanic Mesoscale eddies
2020-05-0792次
Title: Evolution of Submesoscale Ageostrophic Motions through the Life Cycle of Oceanic Mesoscale eddies.
Journal: Geophysical Research Letters, 45, doi: 10.1029/2018GL080399.
Authors: ZHANG Z. -G., and B. Qiu*
Abstract: The global ocean circulation is forced by large-scale fluxes at the surface and dissipated at small scales by diffusion. To achieve a long-term equilibrium requires a dynamical route that transfers energy from large to dissipative scales. The submesoscale ageostrophic motions (1–50 km) have been hypothesized recently to play a critical role in this route by extracting energy from mesoscale eddies (50–500 km) that contain the majority of oceanic kinetic energy. By combining global surface velocity measurements by drifters and satellite altimeter-tracked eddy data set, we show that the submesoscale ageostrophic kinetic energy exhibits unexpected global mean features through the life cycle of mesoscale eddies. The ageostrophic energy is relatively small in eddy’s mature phase but is large both in formation/decaying phases. Furthermore, the energy level of ageostrophic motions depends positively on the local geostrophic strain rate, suggesting that the geostrophic deformation field may dictate the energy transfer from mesoscale eddies to submesoscale motions.