Baroclinic and barotropic tides in the Weddell Sea

Abstract

Barotropic and baroclinic tides were simulated for the Weddell Sea using ROMS. The model estimates for both tidal elevations and velocities showed good agreement with existing observations. The rms differences were 9 cm for elevations and 1.2–1.7 cm s⁻¹ for the major axes of the tidal ellipses for the semidiurnal constituents and 6–8 cm and 4.5 cm s⁻¹ for the diurnal constituents, respectively. Most of the discrepancies occurred deep under the ice shelf for the semidiurnal tides and along the continental slope for the diurnal tides. Along the continental slope, the model overestimated the generation of diurnal continental shelf waves. The diurnal tides were barotropic throughout the basin. However, internal tides were generated at semidiurnal frequencies over rough topography. Over the continental slope, semidiurnal baroclinic tidal generation was enhanced by the existence of continental shelf waves, through their harmonics. Baroclinic tides generated over rough topography in the northern Weddell Sea incited inertial oscillations as they propagated south. These inertial oscillations varied with depth since they were incited at different depths at different times as the internal tide progressed. Both the baroclinic tides and inertial oscillations induced vertical shear in the water column and increased the divergence of the horizontal surface velocities.