Energetics of Eddy-Mean Flow Interactions in the Gulf Stream Region

The Gulf Stream and associated eddies play an important role in mixing the ocean energy, momentum, and biogeochemical properties in the Northwest Atlantic. The Gulf Stream mean flow and eddies can interact to each other through barotropic and baroclinic instability processes. We perform a detailed energetics analysis of their interaction using a high-resolution multidecadal regional ocean model simulation. The energy equations for the time-mean and time-varying flows are derived as a theoretical framework for the analysis. The eddy-mean flow energy components and their interactions show complex spatial distribution in the Gulf Stream region. The cross-stream and cross-bump variations are seen in the along-coast region, whereas a mixed mean-to-eddy and eddy-to-mean interaction pattern is observed in the off-coast region. When considering the domain-averaged energetics, the eddy-mean flow interaction shows significant along-stream variability. In the along-coast and upon-separation regions, the energy is mainly transferred from the mean flow to the eddy field through flow instabilities. In the off-coast region, an inverse conversion from the eddy field to the mean flow dominates the power transfer, indicating that eddies act to drive the mean circulation.