Non-equilibrium Characteristics of the Long-Period Ocean Tides from Dynamics and Energetics

Abstract

Dynamics and energetics of the long-period ocean tides are investigated using a global barotropic ocean model. Estimated oceanic Qs of the long-period tides are about 3, which show that the ocean is heavily damped system. Some far-reaching tidal energy fluxes, however, exist. Equatorial eastward flux from the coast of South Africa to the Pacific especially stands out. LFrom the point of view of wave dynam ics, contrary to the tidal energy flux in the tropics, wave's energy propagates in the westward direction. With the relation between the energy flux of wave and group ve locity, the westward direction shows that the energy flux corresponds to long Rossby wave. Moreover, this relation clearly shows existence of short Rossby waves in the mid latitudes. LFrom the point of view of planetary scale dynamics, zonally averages of dy namic tide and tidal currents show existence of global non-equilibrium response, which is similar to a particular solution of constant depth ocean. The global response may corresponds to the deviation from the equilibrium tide in zonally averaged admittance, which is found in the analysis of altimeter data.