The Sea Level Response of a Stratified Ocean to Barometric Pressure Forcing

Abstract

The nature of the sea surface adjustment to atmospheric loading in a stratified ocean is examined for both midlatitude and equatorial regions, using simple analytical solutions to the quasigeostrophic and equatorial ?-plane equations. While the interior response can have vertical structures ranging from oscillatory to surface trapped, depending on the temporal and spatial scales of the forcing, the sea surface reacts as an inverted barometer at most scales. The inverted barometer or isostatic approximation breaks down only for narrow ranges of frequency and horizontal wavenumber values, where the vertical dependence of solutions approaches that of the oceanic normal modes. In these regions, the sea surface adjustment can be both smaller and larger than the isostatic limit and is sensitive to frequency and wavenumber. The vertical stratification introduces a number of nonisostatic regimes (particularly in the equatorial regions) not possible in a constant density ocean, but the importance of these effects in the real ocean is likely to be small.