The wave-driven ocean circulation

Oceanic surface gravity waves have a mean Lagrangian motion, the Stokes dri ft. The dynamics of wind-driven, basin-scale oceanic currents in the presen ce of Stokes drift are modified by the addition of so-called vortex forces and wave-induced material advection, as well by wave-averaged effects in th e surface boundary conditions for the dynamic pressure, sea level, and vert ical velocity. Some theoretical analyses previously have been made for the gravity wave influences on boundary-layer motions, including the Ekman curr ents. The present paper extends this theory to the basin-scale, depth-integ rated circulation in a bounded domain. It is shown that the Sverdrup circul ation relation, with the meridional transport proportional to the curl of t he surface wind stress, applies to Lagrangian transport, while the associat ed Eulerian transport is shown to have a component opposite to the Stokes-d rift transport. A wave-induced correction to the relation between sea level and surface dynamic pressure is also derived. Preliminary assessments are made of the relative importance of these influences using a global wind cli matology and an empirical relationship between the wind and wave fields. Re commendations are made for further development and testing of this theory a nd for its inclusion in general circulation models.