Impacts of Oceanic Eddy Resolution on the Wind-Driven and Nonlinear Spectral Sources of Kinetic Energy at Low Frequencies

Low-frequency variability within the ocean surface can be excited by both external forcing, such as wind stress, as well as internal nonlinearities. Recent studies have shown that nonlinear interactions at short timescales within the ocean surface can excite variability on longer timescales, indicating a transfer of kinetic energy from high to low frequencies analogous to the inverse cascade in wavenumber space. This transfer of energy is driven by eddy-eddy interactions within the advective term of the equations of motion and may then be sensitive to model resolution and eddy parameterization. Here we utilize GFDL’s CM2.X hierarchy of fully coupled ocean-atmosphere models to address how low frequency variability within the ocean surface is generated. We will compare the magnitude of external sources of energy at low frequencies, such as that of direct forcing from from wind stress, to internal sources of energy due to the local, geostrophic nonlinear transfer of energy to long time scales. Diagnostics of energy flux and transfer within the frequency domain will be compared between three models at 1, 1/4th, and 1/10th degree ocean resolution across eddying and non-eddying regions of the midlatitude oceans to address the importance of eddy resolution in the driving of energy to low frequencies within the spectral domain.