Impacts of mesoscale eddies on the Gulf Stream (GS) mean flow and its adjacent shelf ecosystem variability off the coast of the southeastern United States are studied using hydrographic measurements, satellite observed ocean height and temperature data, as well as model simulations. Observations have shown that the seaward deflection of the GS by the Charleston Bump has a bimodal (either weakly or strongly deflected) character and that the GS meander field downstream of the bump differs significantly between the two states. In a strongly deflected state, the GS tums sharply eastward at the bump and flows seaward far enough to have its surface temperature front offshore of the 600-m isobaths, and can remain so along the continental slope downstream of the bump for several months. Our analyses reveal that topographically induced instability and reduced upstream transport trigger such a strong deflection. Open-ocean cyclonic eddies act in concert to help maintain this state by a vorticity injection mechanism. In the meantime, the compensating flows at the bottom transport nutrient rich deep-water onshore, supporting larger than usual primary productivity on the shelf.