Modeling of Internal Tides in Interaction with Sub-inertial Wind-Forced Flows in the Coastal Ocean

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The proposed research focuses on modeling and dynamical analysis of shelf processes resulting from the combined action and interaction of internal tides and wind-forced ocean flows, with application to the summer upwelling regime on the Oregon shelf. The free-surface, primitive equation Regional Ocean Modeling System (ROMS) will be implemented, forced simultaneously with tides and wind stress. Model findings will be corroborated by the analysis of time-series data from coastally based high frequency radars and moorings, including the data from the NSF-funded Coastal Ocean Advances in Shelf Transport (COAST) and Global Ocean Ecosystem Dynamics (GLOBEC) programs.Intellectual merit. This study will provide new qualitative and quantitative information about both wind-driven flows and internal tides, relevant for the Oregon shelf and more generally for the coastal environment. Key issues to be explored will include (i) effects of sub-inertial wind-forced density and current variations associated with upwelling, on the generation, propagation, and dissipation of the internal tide, both semi-diurnal and diurnal (ii) quantitative understanding of internal tide intermittency and spatial variability, and (iii) importance of the tides for enhancing turbulence, mixing, drag, and affecting cross-shore transport. Model results will help identify areas of intensified internal tide along the Oregon coast, possibly guiding the design of future observational missions.Broader impacts. This project is an important step toward the development of a comprehensive coastal model that accurately represent both low frequency wind and density driven flows, and higher frequency tidal flows. Such a modeling capability will be very useful to the broad community of oceanographers, providing a tool for (a) studying physics, chemistry, and biology, and across discipline interactions in the coastal ocean, (b) driving models describing biological variability on the shelf, and (c) planning new observational programs. Discussions and collaborations between the modeling and observational oceanographic communities will be facilitated, for their mutual benefit. New modeling and assimilation technologies will be integrated into the operational observing systems along the U.S. coasts, serving broad public needs (national security, pollution transport, search and rescue, fisheries, recreation, education). The graduate student supported by this project will be trained to become an expert on coastal ocean modeling and data assimilation using state-of-the-art methods and technologies.