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.
Intellectual merits. We have developed a high-resolution computer model of ocean circulation off the Oregon coast. This model has been used along with available oceanic data to understand the role of high-frequency motions (tides) and more slowly varying wind-driven currents in the coastal environment. Our particular findings concern with the mechanism of internal tide motion generation on the continental slope and its intermittency given ever-changing background conditions. We also discovered unusually intensive diurnal tidal motions around major capes off Oregon, which must contribute to separation of coastal currents in the interior ocean, carrying momentum, heat, and material from the shelf far away. The Columbia River fresh water discharge has been included in the latest version of the model. The study has been focused on the anomalous conditions of 2011, featuring record-high discharge. The effect of the river plume on the internal tide climate is investigated. Broader impacts. Knowledge of the intensity and spatial and temporal variability of the tidal and wind-driven motions on the continental shelves is important for understanding of near-surface and subsurface transports of heat and material. These can be important for prediction of the fate of hazard material spills, fishery management, navigation, search and rescue, and recreation.
