Variabilidade sazonal e ciclos da temperatura e clorofila-a superficiais na costa sudoeste do Oceano Atlântico Sul, através de imagens do sensor MODIS-Aqua

Abstract

The Southwestern Atlantic Ocean is a region of high dynamism and several works have delimited patterns and cycles of physical, chemical and biological process. In this work, satellite-derived temperature and chlorophyll-a field were used to investigate temporal and spatial variability over the continental shelf zone close to the La Plata River estuary. A non linear model was used to fit the annual cycle of the logarithm chlorophyll concentration and sea surface temperature in the region. Spectral analysis were performed in certain areas to find other cycles, besides the annual. It was clearly verified the existence of an annual cycle of temperature, except in the Brazil-Malvinas confluence zone, due to the dynamic of the frontal zone and existing eddies. Close to the Uruguayan and Brazilian coasts, the variability of chlorophyll-a is highly controlled by the plume extension of La Plata river, that flows northward in the winter and restricts to the estuary mouth in other seasons because of the wind pattern. The annual cycle dominates over a large area, specially north of 35ºS. The coast of Rio Grande state, presented a strong annual cycle, mostly due to the arrival of La Plata plume during the winter. In the Brazil-Malvinas Confluence, an annual and semi-annual cycles persist, but other higher frequency cycles associated to mesoscale features are also present in this complex region