Topographic Influences on the Path of the Gulf Stream

Abstract

Meander patterns observed in the Gulf Stream east of Cape Hatteras exhibit correlations with bottom topography. An examination of the orders of magnitude of terms in the Gulf Stream vorticity balance suggests that if the current extends to the ocean bottom, as implied by some recent deep velocity measurements, its path must indeed be controlled principally by the topography of the Continental Rise, with a generally smaller constraint imposed by the meridional variation of the Coriolis parameter. Approximate current paths calculated according to this mechanism—steady-state conservation of potential vorticity—agree sufficiently well with observed paths to confirm the topographic explanation of large-scale meanders. The observed variety in meander patterns is attributed to fluctuations in current direction and path curvature near Cape Hatteras. These conclusions make doubtful any direct relation between large-scale meanders and possible instabilities of the Gulf Stream east of Cape Hatteras, and between the distribution of wind stress and the separation of Stream from coast.