Vertical velocities and dynamical balances in Gulf Stream meanders

Abstract

A triangular array of current meter moorings was deployed within the cyclonic flank of the Gulf Stream in the South Atlantic Bight from September 1981 to April 1982. Using velocity and temperature data and the nondiffusive heat equation, a time series of vertical velocity was derived. A mean vertical velocity of −0.013 cm s−1 and standard deviation of 0.078 cm s−1 were obtained. To better understand the subsurface structure of Gulf Stream meanders, the time series of horizontal and vertical velocities and temperature were examined at times when events were passing through the array. The flow along the trailing edge of a Gulf Stream meander and within the leading portion of a cold core frontal eddy was found to have an upward component (positive w), while that within the trailing portion of the frontal eddy and along the leading edge of a meander had a downward component (negative w). Using the horizontal and vertical velocity time series, cross‐stream and along stream momentum balances were calculated. The downstream flow was found to be in geostrophic balance. In contrast, the Coriolis and nonlinear terms were found to contribute equally to the determination of the cross‐stream flow.