An Overlooked Mechanism for Wind-driven Circulations in Semi-enclosed Marginal Seas

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Marginal seas occupy a large fraction of the World Ocean's margins and are key areas for human activity, yet very little attention has been paid to how the observed large-scale winds force water circulation in these areas. This is the focus of this study that uses numerical models (idealized and realistic) to gain a better understanding of how winds force circulation patterns in marginal seas and how this affects exchanges of mass, heat, and freshwater between marginal seas and the open ocean. Understanding how winds force circulations in marginal seas is important for forecasting fisheries, pollution dispersion, military activity, and shipping. There are broader impacts also related to education and student development. Results from this program will be incorporated into graduate level classes and lectures at the Woods Hole Oceanographic Institution (WHOI) Geophysical Fluid Dynamics (GFD) Summer School. Undergraduate and graduate students participating in the WHOI Summer Student Fellow Program and GFD Summer School will be engaged and trained in numerical methods, applied mathematics, and data analysis.The primary intellectual merit of the proposed work lies in the advancement of knowledge of the circulation in marginal seas. The original aspects of the proposed research are the focus on forcing by wind stress (as opposed to wind stress curl) and in the synthesis of idealized and realistic numerical models over a wide range of applications. The problem is motivated by the numerous marginal seas found along the western North Pacific, but the approach followed is designed to yield insights into the generic problem of the coupling between Ekman transports, topographic barriers, boundary layers, and interior flows, making it applicable to all marginal seas for which wind-forcing is important. To date, the exchange between marginal seas and the open ocean has been viewed as being forced by geostrophic flows impinging on the marginal sea. However, the Ekman transport under consideration here is much more effective at penetrating the topographic barriers that define the marginal sea and is an unexplored mechanism for forcing within the marginal sea and for exchange between the marginal sea and the open ocean. In this study, the emphasis is on how Ekman transports, forced by large-scale wind stress, interact with boundaries and drive both boundary layer and basin-scale flows. Idealized and realistic numerical models are applied to a wide range of physical configurations. The idealized configurations allow for inference of how the circulation depends on the physical geometry of the marginal seas and forcing, while the realistic configurations allow for this knowledge to be applied to more complete, real systems. The model results are interpreted using analyses of mass, heat, and potential vorticity budgets.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.