Variación estacional del balance geostrófico en la región ecuatorial

Abstract

Using hydrographic data gathered during the "NORPAX Hawaii-Tahiti Shuttle" (Feb. 1979- Jun. 1980) the seasonal variability of the geostrophic current field in a region of the central Pacific Ocean is studied. The study area includes the equator and its neighborhood, where the validity of the geostrophic balance is still a matter of controversy. With poten tia! energy as a metric, the isopycnal vertical displacement field is decomposed into empirical ortogonal functions. Most of the energy (92°/o) is found to be contained in the first three modes. The structure of the first mode (85°/0 of the energy) corresponds to that of the temporal average, whereas the second and third modes clearly show the existence of an annual signa! which contains 48°tb of the variability, that is, of the remaining 15otb. Position, magnitud and direction of the currents obtained using only these three modes, as well as their seasonal variations, agree very well with the results of other studies. The differences between the geostrophic currents and those directly measured are not found to be significant for both the mean and the anual fluctuations.