A climatology of the annual cycle of river discharges into the Brazilian continental shelves: from seasonal to interannual variability

Abstract River runoff into the continental shelf affects the coastal environment in many ways: from sediment input and marine sediments resuspension to meso-scale eddies formation in case of higher river discharges. Therefore, for ocean modeling is crucial to understand the seasonal and interannual river runoff variability. Brazil stands out when it comes to riverine discharge, since 6 out of the 50 largest rivers flows within the country limits. Here, a compilation of all river discharge data provided by the Brazilian National Water Agency resulted in the identification of 97 exorheic rivers (with time series longer than 15 years), including 10 unmonitored ones which had climatologies estimated by the proposed methodology. This compilation took a considerable effort, as streamflow stations were often far from the discharge location. It was also necessary to overcome the challenge associated with the Brazilian climate heterogeneity in order to apply the regionalization method. The riverine input into the ocean was estimated at the mouth of the rivers, with the overall discharge analysis taking into consideration a division of the Brazilian Continental Shelf in five sectors. These results analyzed here are also made available for public use. Overall, the Brazilian northern continental shelf receives about 95% of the total annual river runoff (212,148 m3 s−1), followed by the northeastern continental shelf with 1.5% (3345 m3 s−1), the eastern continental shelf with 1.4% (3097 m3 s−1) and the southern continental shelf with about 1.3% (2997 m3 s−1). The southeastern continental shelf receives only 0.8% of the total discharge (1909 m3 s−1). Throughout the year, the major river discharges were observed from summer to winter months, following the different climate and precipitation patterns along the country. The interannual variability of the discharges was assessed, also looking at similarities regarding both El Niño Southern Oscillation and Pacific Decadal Oscillation.

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Recommended citation: Carvalho Oliveira, J., Aguiar, W., Cirano, M. et al. A climatology of the annual cycle of river discharges into the Brazilian continental shelves: from seasonal to interannual variability. Environ Earth Sci 77, 192 (2018). https://doi.org/10.1007/s12665-018-7349-y