Understanding Nonlinear Interactions between Barotropic and Baroclinic Processes in a Global Tide and Storm Surge Model

With climate change continuing to affect the ocean system, it is critical to accurately predict both changes in tides and inundation due to storm-driven surge to protect the approximately 40% of the world that lives in coastal regions. Advances in numerical modeling and computational efficiency have enabled total water level hindcasting and forecasting models to better resolve coastal regions while simultaneously expanding from regional to global domains. With these advanced new models, a deeper understanding of how oceanic processes such as boundary layer dissipation, internal wave generation due to barotropic to baroclinic conversion, and density driven effects interact with each other and affect total water levels is possible. The research described herein uses numerical models to examine and quantify the interactions between these nonlinear processes and how to accurately capture them to achieve highly-accurate tidal and nontidal water levels in a hydrodynamic model. First, a depth-averaged global tidal model is used to explore the mechanisms and geographic distribution of tidal dissipation as well as how changes in these mechanisms affect global tides. The knowledge gained through this study is used to optimize the tidal model and greatly improve tidal results. Second, baroclinicity is incorporated into a depth-averaged model through one-way coupling to an ocean global circulation model. Improvements to frictional parameterizations required to maintain satisfactory tidal and nontidal results in this coupled model are explored and the implications of why these modifications are required reveal valuable information about the physical processes that they emulate. The accuracy of the resulting coupled total water level model is examined and discussed.