Influence of coastal and nearshore morphology on sedimentation and inner shelf circulation.

摘要

Understanding the development of wind-driven flows over the inner shelf where the effects of coastal morphology can complicate flow patterns are important in understanding how sediments and other materials such as pollutants, larvae, and nutrients can be exchanged between the shore and deeper regions of the continental shelf.{09}This dissertation explores several aspects of inner shelf circulation on the inner shelf at two sites in the South Atlantic Bight.; In the first part, the role of along and cross-shore currents were evaluated with respect to the sediment transport processes that contribute to the maintenance of sorted bedforms on the inner shelf of Wrightsville Beach, North Carolina. Here benthic boundary layer model results are used to show that differences in bed roughness between the coarse areas of the seabed within the coarse regions of the sorted bedforms and the finer areas of the inner shelf are more pronounced during increasingly energetic wave and current conditions.; The second chapter examines the spatial variability of near-bed flows over the inner shelf of Long Bay, South Carolina, a concave embayment stretching between Cape Fear and Cape Romain.{09}In this case it was noted that flows within 1 km of the shore opposed the wind and currents farther offshore during southwestward winds (downwelling favorable). Analysis of the depth-averaged, alongshore momentum balance illustrated that the alongshore pressure gradient approached or exceeded the magnitude of the alongshore wind stress at the same time that the nearshore alongshore current opposed the wind stress and alongshore currents farther offshore.; In the third part of this work, six months of oceanographic observations were used to examine the development of vertical density gradients and their effect on the wind-driven circulation over the inner shelf of Long Bay. Here, vertical density gradients were observed mainly during periods of northward wind (upwelling favorable). At these times a two-layered flow pattern was observed where near-surface flows were directed alongshore aligned with the wind. At the same time, near-bed flows, which were weaker, were directed onshore compensating for the offshore transport in the surface layer in a manner qualitatively consistent with Ekman circulation over the continental shelf.