Overview Of The Frontal Eddy Dynamics Study (FRED*) Off North Carolina

During May to November, 1987, oceanographic measurements were made off North Carolina to examine the effects of Gulf Stream frontal eddies on the circulation over the continental shelf. Satellite images were collected daily and currents were measured at eight moorings containing 21 current meters. During two weeks in May three eddies were intensively examined using satellite imagery, drifting buoys, aircraft and vessel launched temperature probes, and an underway Acoustic Doppler Current Profiler. The Gulf Stream appears to behave in two distinct modes: 1 ) small meander mode, the Gulf Stream Front lies at the shelf break and meanders of the Front have smaller amplitudes. Frontal eddies and associated warm water filaments are smaller and farther from shore during this mode; 2 ) large meander mode, the Front is displaced offshore of the shelf break and the meanders have large amplitudes. filaments are larger and closer to shore during this mode. Frontal eddies and warm Eddies regularly pass by locations off the North Carolina coast approximately once every five days. After an eddy passes, parts of the filament may stagnate on the shelf for approximately a week before dissipating and moving offshore into the North Atlantic Ocean. The results suggest that small changes in the Gulf Stream path can lead to large changes in the propagation of frontal eddies passing Cape Hatteras.