Connection between internal wave activity and outer shelf and slope circulation during winter 2012 off Long Bay (SE US)

Abstract

A cross-shelf moored array, shipboard current profiler observations and glider observations were collected over the first few months of 2012 as part of a study of wintertime phytoplankton blooms off the coast of northern South Carolina, United States. The combined dataset is examined to document the internal wave field in the region inshore of the offshore deflection of the Gulf Stream. Moderate amplitude isopycnal displacements of 10-20 meters are common in glider observations over the slope; much larger displacements were observed when the glider was drawn offshore by the Gulf Stream. Meanders of the Gulf Stream indirectly forced the outer shelf flow through formation of filaments off the meander crests that moved along the upper slope. Several filaments exhibited unusually strong flow and moved equatorward, displacing ambient waters. Moored current meters indicate intermittent internal tides on the upper slope and shelf and a correlation with the external tide. The intermittency of the internal tide may be related to the varying alongshelf flow and varying mass field over the shelf.