BAROCLINIC INSTABILITIES AND FORCED OSCILLATIONS IN THE BRAZIL-MALVINAS CONFLUENCE ZONE

GARZOLI, S.; SIMIONATO, C. G.

DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY

Pergamon Press, Elsevier Science

Lugar: Amsterdam, The Netherlands; Año: 1990 vol. 37 p. 1056 - 1074

0967-0645

Observations collected at the confluence between the Brazil and Malvinas Currents are analyzed to study the high-frequency oscillations in the range of periods from 55 to 2 days. The variability in time and space of the thermohaline front originates at the confluence. The meandering of the Brazil Current after the encounter and the presence of an abrupt shelf-break, create the conditions for the generation of baroclinic and internal waves. Analysis of time series of dynamic height, wind magnitude and position of the front indicates the following: in the band from 20 to 55 days periods, two waves propagate with similar characteristics but in the opposite direction; neither of these waves appears to be forced by the wind. The westward propagating wave (T=37.4 days) is related to the position of the front and is assumed to be forced by its north-south displacement. The eastwards propagating wave (T=29.1 days) has the characteristics of a topographic Rossby wave. At shorter periods, in the band from 2 to 10 days, the spectrum of the atmosphere is very energetic. The passage of cyclones can be detected by the seasonal variability of the energy spectra. The ocean is forced by the wind at periods of 5 and 2.6 days. In addition to these wind-forced oscillations, the presence of the front originates baroclinic instabilities in the same band.