| Abstract: | Understanding across-margin transport has long been recognized as crucial for wise management of our coastline and shelf waters. Issues related to sewage outfalls, nutrient and pollutant dispersal, carbon export, and shoreline sediment budgets all require an understanding of these processes. Across-margin transport of water and sediment at cuspate foreland headlands has been largely unrecognized, and the processes responsible for this export unappreciated. We examined physical process on Cape Lookout Shoal, a cape-associated shoal on the North Carolina continental shelf, through numerical modeling and field observations of near-bottom currents. The cuspate foreland setting of the northern South Atlantic Bight has been previously characterized as wave-dominated with a principal alongshore directed sediment transport and physical circulation forced by wave and wind-driven currents along the inner and mid-shelf. Our findings instead suggest that a seaward-directed, tidal-driven headland flow many play a significant role in the direction of net sediment transport on the shoal and ultimately its location and long-term maintenance. The shoal's location relative to the promontory-induced residual eddies and the region of active deposition differs from traditionally held ideas on sedimentary processes at headland-related sand banks. In addition, the headland flows may also serve as a first-order mechanism for rapidly exporting nearshore and estuarine waters to the outer-shelf. |
