Storm-Forced Baroclinic Near-Inertial Currents on the Grand Bank

Abstract

Current meter data for six mouths from the Grand Bank are analyzed to study inertial currents generated by moving storms. It is found that during periods of strong winds, but no well-defined storm system, the inertial motion exhibits no simple relationship to the local wind. During intense storms inertial currents up to 0.5 m s?1 were observed both in and below the mixed layer. Upper and lower layer currents are roughly equal in amplitude, but are 180° out of phase. To explain this observation, a two-layer, one-dimensional model is developed that successfully simulates the observed inertial currents. We show that under the conditions encountered during the storms only baroclinic inertial motion can be generated. The pressure gradient effect is not important, and the current below the mixed layer is produced by mass continuity. Wavelength computed from the continuity equation is consistent with that predicted by first-order linear theory. For inertial motion generated during periods of strong wind but no cyclone, pressure gradients and barotropic response can be important and should not be neglected.