The Relation of Near-Inertial Motions Observed in the Mixed layer During the JASIN (1978) Experiment to the Local Wind Stress and to the Quasi-Geostrophic Flow Field

Abstract

Abstract Oscillations with near-inertial frequencies were an energetic component of the upper ocean velocity field observed at each of two moorings separated by 44 km during the Joint Air Sea INteraction (JASIN) experiment during the late summer of 1978. At each mooring the amplitude of the inertial motion was highest in the mixed layer, where it was nearly depth-independent. Previous work (Pollard and Millard, 1970; Pollard, 1980) had found that the amplitude and phase of inertial motion in the mixed layer was related to the local wind stress. In this case, the loacal winds, measured at each mooring, were coherent; but the time series of mixed-layer, near-inertial motion at one mooring bore little resemblance to that at the other mooring. During JASIN 1978 the differences in the inertial response at the two moorings coincided with differences in the quasi-geostrophic flow field in the vicinity of the two moorings. Inclusion of the horizontal gradients of the quasi-geostrophic flow in model equations prov...