Island in the Stream: Oceanography and Fisheries of the Charleston Bump

Gulf Stream Physical Oceanography at the Charleston Bump: Deflection, Bimodality, Meanders, and Up welling

John M. Bane, Jr., Larry P. Atkinson, and David A. Brooks


Abstract.—The recurring seaward deflection of the Gulf Stream near 32°N latitude had been noticed by a number of investigators before the mid-1970s when Richard Legeckis first attributed the phenomenon to a topographic feature on the upper continental slope now known as the Charleston Bump. Since then, extensive studies have delineated many properties of the deflection and its effects on the Gulf Stream and surrounding waters including: the apparently bimodal nature of the deflection (resulting in the “strongly deflected” and “weakly deflected” states of the Gulf Stream’s path near the Bump); the set up of the Charleston Gyre during strongly deflected conditions; the amplification of downstream-propagating Gulf Stream meanders in the Bump region; the meander-induced upwelling that accompanies meander propagation; and the cross-isobath exchange of shelf and Gulf Stream waters driven by the Charleston Gyre and Gulf Stream meanders. Of particular interest is the fact that there is still no unambiguous cause identified for inducing the Gulf Stream to shift from a weakly deflected path to a strongly deflected path, although several candidate mechanisms exist.