Observations of shallow-water transport and shear in western Florida Bay

Acoustic Doppler profiler (ADP) data are used to describe depth-integrated transport and vertical shear at two study sites along the open western boun dary of Florida Bay. During a 404-day study period, transport was into the bay at the northern study site, where the depth-averaged 3.2 m. Transport a t the southern study site, where the depth averaged 2.0 m, was out of the b ay during a 266-day time period. A comparison of flow in the top and bottom layers of the ADP profile at the northern study site reveals patterns that are very different from each other, and very different from the depth-inte grated transport. Nontidal Row in the surface layer is nearly consistently out of the bay and highly correlated with wind forcing. East-west near-bott om flow is inversely correlated with the rise and fall of water level in no rthwest Florida Bay. Nontidal east-west Row in the bottom layer is negligib le, suggesting a near balance between westward directed wind stress and eas tward directed barotropic pressure gradients maintained by the setdown of w ater level in the bay. At the southern study site, near-bottom flow is simi lar to near-surface Row, and both are similar to depth-integrated transport . Ar both locations, the instantaneous directional shear from near-surface to near-bottom levels is less than 1 degrees on average. Also. at both stud y sites, vertically integrated cumulative net transport can he approximated using current observations from a single level within the water column. On ly at the southern study site, however, can the cumulative net displacement at any level be approximated by extrapolating vertically from mid-depth ob servations. Roughness lengths calculated from ADP profiles are concentrated below 1 cm but highly variable, and ADP profiles are not well suited for e stimating bottom roughness.