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Observations On The Distribution Of Meroplankton During A Downwelling Event And Associated Intrusion Of The Chesapeake Bay Estuarine Plume, Al Shanks, J Largier, L Brink, J Brubaker, R Hooff
Observations On The Distribution Of Meroplankton During A Downwelling Event And Associated Intrusion Of The Chesapeake Bay Estuarine Plume, Al Shanks, J Largier, L Brink, J Brubaker, R Hooff
VIMS Articles
We investigated the dispersal of larvae of benthic invertebrates and tested the hypothesis that larvae behaved as if they were passive particles. Observations were made off Duck, North Carolina, USA diving a period of wind driven downwelling at the coast and an intrusion of estuarine water from the Chesapeake Bay. The plume of estuarine water (salinity < 30 psu) was strongest at the shoreward stations in the more northern transects. Wind driven shoreward surface flow, converged at the seaward edge of the plume and downwelled. Offshore flow was present below the thermocline and caused the thermocline to bend downward and contact the bottom at between 5 and 10 km offshore. In the zooplankton samples, we enumerated 33 taxa of larvae (17 taxa of bivalve veligers, 10 taxa of gastropod veligers, and 6 taxa of polychaete larvae). Using cluster analysis, larvae were separated into groups with similar patterns of distribution. If larvae were acting as passive particles then we hypothesized that: 1) Their distribution should remain tied to a water mass and 2) around a convergence or divergence, there should be no change in larval concentration. The distributions of larvae in Clusters 1, 4, 5, and 6 were consistent with the hypothesis that thy were acting as passive particles. Larvae in Clusters 2 and 3, however, did not appear to be acting as passive particles. Larvae in Cluster 2 did not remain tied to a water mass. They entered the study area in the estuarine plume waters, but within 20 km they were nearly absent from the plume water and were found seaward of the plume and at greater depth. Larvae in Cluster 3 were most abundant in areas of converging currents where the shoreward flowing surface waters downwelled at the plume front or against the shore. We hypothesized that larvae of organisms which as adults live in the intertidal or shallow, subtidal zones would have more nearshore distributions than the larvae of adults that are broadly distributed across the shelf. We compared the depth of the habitat of the adult bivalves from which the bivalve larvae in the different clusters were derived. The results were consistent with the hypothesis; larvae with distributions closer to shore tended to come from adults found at shallower depths or in the intertidal zone.
Assimilating High-Resolution Salinity Data Into A Model Of A Partially Mixed Estuary, Jiangtao Xu, Shenn-Yu Chao, Raleigh R. Hood, Harry V. Wang
Assimilating High-Resolution Salinity Data Into A Model Of A Partially Mixed Estuary, Jiangtao Xu, Shenn-Yu Chao, Raleigh R. Hood, Harry V. Wang
VIMS Articles
[1] A three-dimensional circulation model of the Chesapeake Bay is used to validate a simple data assimilation scheme, using high-resolution salinity data acquired from a ship-towed undulating vehicle (a Scanfish). The simulation period spans the entire year of 1995 during which the high-resolution Scanfish data were available in July and October, lasting a few days each. Since Scanfish data were irregularly distributed in time and space, only salinity fields are nudged in the model for simplicity. Model improvements through data assimilation are evaluated from a pair of experiments: one with data assimilation and one without. Data from scattered Chesapeake Bay …
Examination Of Diffusion Versus Advection Dominated Sediment Suspension On The Inner Shelf Under Storm And Swell Conditions, Duck, North Carolina, Guan-Hong Lee, Carl T. Friedrichs, Chris E. Vincent
Examination Of Diffusion Versus Advection Dominated Sediment Suspension On The Inner Shelf Under Storm And Swell Conditions, Duck, North Carolina, Guan-Hong Lee, Carl T. Friedrichs, Chris E. Vincent
VIMS Articles
[1] A benthic boundary layer tripod supporting six current meters and three profiling acoustic backscatter sensors (ABS) documented storm and swell conditions during the fall of 1996 at a depth of 13 m on the inner shelf off Duck, North Carolina. Sediment concentration was higher in the wave boundary layer (WBL) during storm conditions but higher similar to40 cm above the bed (cm ab) during swell conditions. To test the applicability of a diffusive balance during storm versus swell, ABS data were used to invert the vertical diffusion equation and solve for eddy diffusivity from 1 to 50 cm ab. …
Across-Shelf Sediment Transport: Interactions Between Suspended Sediment And Bed Sediment, Courtney K. Harris, Patricia Wiberg
Across-Shelf Sediment Transport: Interactions Between Suspended Sediment And Bed Sediment, Courtney K. Harris, Patricia Wiberg
VIMS Articles
[1] We use a two-dimensional, time-dependent sediment-transport model to quantify across-shelf transport, deposition, and sorting during wave-driven resuspension events characteristic of those that dominate sediment transport on many continental shelves. Decreases in wave-orbital velocities as water depth increases, and the resulting cross-shelf gradient in bed shear stress favor a net offshore transport of sediment. On wide, flat shelves (slopes similar to0.1%), these gradients are low, and the depth to which the seabed is reworked depends mainly on bottom shear stress and local sediment availability. On narrow, steep shelves (slopes similar to0.5%), however, the gradient in bottom stress generates significant cross-shelf …