Discharge variability within the Amazon basin
Résumé
The discharge data of 80 stations (1981-2002) located in the Amazon basin are analysed in relation to the SST in the tropical Pacific and Atlantic oceans, using composite analysis. A wavelet analysis is performed on the 100-year discharge series at Obidos (downstream Amazon). Discharge is lower than normal during El Niño except in the western rivers (Solimões, upper Negro, and Japura) and in the southernmost regions (upper Madeira, Tapajós and Xingu basins). During La Niña, discharge is higher than normal in the northeastern basin and, in contrast, lower than normal in the Madeira basin. However, the ENSO signal is not stationary at Obidos during the 20th century, when considering high flow and mean discharge. High discharges in a vast central region of the Amazon basin are associated with cold SST over the Northern Tropical Atlantic (NATL) during the low-flow season. Furthermore, a common, though not permanent, near-decadal signal is observed in Obidos low flow and NATL SST. The discharge of the southernmost Amazonian rivers is related to the south Atlantic SST; however, these signals are space and time dependent.
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