Abstract Warm saline water masses emanating from the Persian Gulf (PG) and the Red Sea (RS) spread across a large area of the northern Indian Ocean upper layers, affecting the thermocline stratification, the circulation, and the air-sea exchanges over the Arabian Sea (AS) and Bay of Bengal (BoB). To explore the significance of these waters, we use numerical simulations to investigate the impact of isolating (closing) the RS and PG. The results show that the differences between the model runs, with and without the RS and PG, have marked effects on the AS and BoB seasonal variability. As expected, the major differences are concentrated in the surface mixed layer and thermocline of the AS. However, differences are also found further east in the BoB, mainly during the boreal summer. Significant differences are present in the air-sea freshwater and heat fluxes calculated by the model. In addition to the seasonality, there are significant interannual variability, with possible correlation with the El Nino-Southern Oscillation. Results of the experiments suggest that the upwelling in the Sri Lanka Dome, in the southwestern Bay of Bengal, would have responded differently to the 2009-2010 El Niño-La Niña in the absence of PG and RS input.

Neste artigo, treze anos de imagens semanais da temperatura da superfície do mar (TSM) obtidas através do sensor infravermelho Advanced Very High Resolution Radiometer a bordo dos satélites NOAA, de janeiro de 1982 a dezembro de 1994, são utlilizadas para investigar as variabilidades espacial e temporal do cicIo sazonal de TSM no Oceano Atlântico Sudoeste. Este trabalho objetiva as variações de larga escala sobre a plataforma continental e o talude leste da América do Sul limitados ao largo pela isóbata de 1000 metros, entre 42°5 e 22°S. As séries temporais de TSM são ajustadas aos .harmônicos anual e sem i-anual para descrever a variação anual das temperaturas da superfície do mar. O harmônico anual explica a maior parte da variabilidade da TSM. O coeficiente de determinação é alto (> 90%) sobre a plataforma continental, decrescendo em direção ao largo. A amplitude estimada do cicIo sazonal varia entre 4° e l30e na região de estudo, atingindo mínimas temperaturas em agosto-setembro e máximas em fevereiro-março. Após identificação e remoção das componentes dominantes da variabilidade da TSM, modelos como o apresentado aqui são uma ferramenta atrativa para o estudo da variabilidade inter-anual da TSM.

In this article, thirteen years of weekly sea surface temperature (SST) fields derived from NOAA Advanced Very High Resolution Radiometer global area coverage infrared satellite data, from January 1982 to December 1994, are used to investigate spatial and temporal variabilities of SST seasonal cycle in the Southwest Atlantic Oceano This work addresses large scale variations over the eastem South American continental shelf and slope regions limited offshore by the 1000-m isobath, between 42° and 22°S. SST time series are fit with annual and semi-annual harmonics to describe the annual variation of sea surface temperatures. The annual harmonic explains a large proportion of the SST variability. The coefficient of determination is highest (> 90%) on the continental shelf, decreasing offshore. The estimated amplitude of the seasonal cycle ranges between 4° and 13°e throughout the study area, with minima in AugustSeptember and maxima in February-March. After the identification and removal of the dominant annual components ofSST variability, models such as the one presented here are an attractive tool to study interannual SST variability.