Generation of Oceanic Internal Waves by a Cyclonic Surface Stress Disturbance

G.S. Voelker, P.G. Myers, M. Walter and B.R. Sutherland

Atmospheric cyclones with strong winds signicantly impact the ocean circulation, regional sea surface temperature and deep water formation in the North Atlantic. Thus they are expected to play a key role in a variety of energy transport mechanisms. The present study investigates the generation of internal gravity waves during a geostrophic adjustment process in a Boussinesq model with axisymmetric geometry. The atmospheric disturbance is set by an idealized pulse of cyclonic wind stress with a Rankine vortex structure. Strength, radius and duration of the forcing are varied. The eect upon wave generation of stratication with variable mixed layer depth is also examined. Results indicate that internal gravity waves are generated after approximately one inertial period. The outward radial energy flux is dominated by waves having structure close to vertical mode-1 and with frequency close to the inertial frequency. Less energetic higher mode waves are observed to be generated close to the sea floor underneath the storm. The total radiated energy corresponds to approximately 0.02% of the wind input. Deeper mixed layer conditions as well as weaker stratication reduce this fraction.