THE EVOLUTION OF BOUNDARY PRESSURE IN OCEAN BASINS

The boundary pressure adjustment process on an ocean basin scale is el ucidated in two sets of numerical experiments. First, an initial-value problem is posed in a primitive equation shallow-water model that lea ds to significant changes in the pressure averaged along the boundary in a closed rectangular ocean basin. These results are compared with t he analogous problem in a shallow-water quasigeostrophic model where t he boundary pressure adjustment is parameterized by a consistency cons traint that closes the mass, circulation, and energy balances in quasi geostrophy. There is very good agreement in the evolution of the bound ary-average pressure and qualitative agreement in the evolution of the balanced motions in the interior. Second. idealized Kelvin wave exper iments are posed in the primitive equation system on an f plane, a bet a plane, and a beta plane in a domain of doubled dimensions. For beta not-equal 0, a scattering process is evident as the initial Kelvin wav e transits the first meridional boundary it encounters. Two distinct s cattering products are observed. In one there is a mass flux out of th e coastal waveguide into the balanced interior motions that occurs on a time scale comparable to the basin circuit time for the initial Kelv in wave. The second scattering product occurs in the wake of the Kelvi n wave within the waveguide, forming a basin-scale coastal current. Th e relevant time scale for the waveguide scattering product is comparab le to the time required to equilibrate the mass anomaly imposed in the waveguide by the Kelvin wave initial condition. The experiments demon strate a coupling between short time scale motions of the coastal wave guide and longer time scale motions on the ocean interior. Implication s of these processes are assessed for both these model problems and mo re general problems of transient ocean dynamics.