Collaborative Research: The Role of Coastal Fronts in Mixing and Ventilating Coastal Waters

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Coastal fronts are regions of the upper ocean with sharp boundaries that separate distinct water masses. Fronts are associated with conditions of enhanced turbulence and vertical velocities. Interactions between strong stratification, flow convergence, and enhanced vertical fluxes near fronts have important and immediate implications for gas and energy exchange within the world’s oceans. Detailed observations using state-of-the-art methods that include an instrumented autonomous underwater vehicle (AUV) and drifting platforms would be used to resolve fine scale dynamics that lead to the enhancement of mixing and vertical exchange in the vicinity of a coastal front. The data collected and subsequent analysis would improve estimates of exchange rates that determine a system’s susceptibility to acidification and hypoxia, primary production, and transport of material. This study will improve our ability to predict and manage coastal ocean acidification and hypoxia, as well as enable new lines of inquiry into upper ocean exchange processes. The project will also contribute to the development of the career of a young scientist. Outreach efforts include participation in the annual University of Washington Discovery Days event, which draws over 10,000 students from regional K-12 schools to visit the campus and learn about current research. Student participation at multiple levels would be fostered by pursuing undergraduate research opportunities through the NSF REU program as well as promote involvement of graduate and undergraduate students within the Department of Civil and Environmental Engineering at the University of Washington and UC Santa Barbara. The interaction between surface wave breaking, bubble-entrainment, and downwelling convergence in the vicinity of coastal fronts are the focus of the study, with the primary goal being to investigate the specific nature and transiency of turbulent exchange at these locations. The proposed work builds on recent results using SWIFT drifters as well as a REMUS 600 autonomous underwater vehicle to measure upper ocean turbulent dissipation rates. Detailed measurements of turbulent energetics and Reynolds stresses will provide a transformative view of exchange processes at episodic and transient frontal features. This would be linked to dynamics driving frontogenesis through control volume analyses and estimates of topographic form drag. Through the collection of comprehensive in-situ measurements proposed here, the role(s) of surface fronts in ventilating and mixing coastal and estuarine waters would be quantitatively characterized.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.