Near-inertial waves on the nontraditional'' β plane -: art. no. C01003

Propagation of linear near-inertial waves on the beta plane is considered, taking into account the horizontal component of the Earth's rotation, (f) over tilde. ( Terms, effects etc., due to this component will be referred to as nontraditional, for brevity.) It is shown that the combined effect of beta and (f) over tilde changes the dynamics in a fundamental way. For a vertically unbounded domain, an exact solution shows that near-inertial waves can pass through the inertial latitude, unlike under the traditional approximation. For parameter values typical of the ocean, the subinertial domain extends several hundreds of kilometers poleward of the inertial latitude. The solution undergoes a profound change if a vertically bounded, instead of unbounded, domain is considered. Part of the wave energy then accumulates at the poleward end of the subinertial domain, which involves an evolution toward infinitesimal horizontal and vertical scales. For vertically nonuniform stratification, examined here using the Garrett-Munk exponential profile, one finds a wedge-like waveguide, which becomes increasingly narrow in the poleward direction, and drives subinertial waves into the region of the weakest stratification, i.e., the abyss. For typical parameters, the relative amount of poleward traveling energy that gets trapped is estimated to lie between 10 and 30%; its dependence on latitude and stratification is also outlined. The observational evidence and possible implications for abyssal mixing are discussed.