Nonlinear Radiating Instability of a Barotropic Eastern Boundary Current

• Main Authors: Wang, Jinbo (Contributor), Spall, Michael A. (Author), Flierl, Glenn Richard (Contributor), Rizzoli, Paola M. (Contributor)
• Other Authors: Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences (Contributor), Woods Hole Oceanographic Institution (Contributor)
• Format: Article
• Language: English
• Published: American Meteorological Society, 2014-02-24T17:23:50Z.
• Subjects: Article
• Online Access: Get fulltext

Linear and nonlinear radiating instabilities of an eastern boundary current are studied using a barotropic quasigeostrophic model in an idealized meridional channel. The eastern boundary current is meridionally uniform and produces unstable modes in which long waves are most able to radiate. These long radiating modes are easily suppressed by friction because of their small growth rates. However, the long radiating modes can overcome friction by nonlinear energy input transferred from the more unstable trapped mode and play an important role in the energy budget of the boundary current system. The nonlinearly powered long radiating modes take away part of the perturbation energy from the instability origin to the ocean interior. The radiated instabilities can generate zonal striations in the ocean interior that are comparable to features observed in the ocean. Subharmonic instability is identified to be responsible for the nonlinear resonance between the radiating and trapped modes, but more general nonlinear triad interactions are expected to apply in a highly nonlinear environment.
MIT-WHOI Joint Program in Physical Oceanography
MIT Y-S Fellowship
United States. National Aeronautics and Space Administration (Grant NNX12AD47G)
Grant OCE-0752346