ATMOSPHERIC LOADING AND THE OCEANIC INVERTED BAROMETER EFFECT

The response of the ocean to fluctuating atmospheric pressure loads is reviewed in theory and in observations. Major theoretical issues lie primarily with Oceanic boundary reflectivity and with rates of dissipa tion, generally. Analytical solutions for a stratified ocean show that a static (''inverted barometer'') response is anticipated at all freq uencies and wavenumbers not coincident with certain dispersion curves. Nonstatic behavior of two types is predicted: zero motion of the sea surface and a resonant response. Two types of resonance emerge. The fi rst type corresponds to barotropic modes which are long gravity waves or Rossby waves at high and low frequencies, respectively. The second type excites internal modes, either gravity waves or Rossby waves depe nding on frequency, but modified from a conventional resonant response by the immediate juxtaposition in frequency/wavenumber space of the r igid-lid modes. The extent to which these actual resonances are genera ted is obscure owing to the same uncertainties about oceanic dissipati on and scattering which affect ail other forced oceanic motions, espec ially including the tides and other barotropic motions. Zero sea surfa ce motion is predicted at frequencies and wavenumbers corresponding to ''rigid-lid'' modes. Observations support the wide applicability of t he static response except in the tropics and in the western boundary c urrent extension regions; there, the signal-to-noise ratios may be ina dequate. The only other known clear nonstatic response occurs near 5 d ays in the pacific and South Atlantic Oceans, indicative of a low-Q re sonance in the former area and a forced nonresonant response in the la tter, but there are remaining problems with these interpretations.