Robertson Andrew W. author Columbia University. International Research Institute for Climate and Society Mechoso Carlos R. author Columbia University. International Research Institute for Climate and Society originator text Articles 1998 English The time series of annual streamflow of four rivers in southeastern and south-central South America (the Negro, Paraguay, Paraná, and Uruguay Rivers) for the period 1911–93 are analyzed. Application of the multitaper method shows that the following features are significant at the 95% level: 1) a nonlinear trend, 2) a near-decadal component, and 3) interannual peaks with ENSO timescales. The trend and near-decadal components are most marked in the two more central rivers, the Paraguay and Paraná, with ENSO timescale variability most pronounced in the Negro and Uruguay rivers in the southeast. Composites of SST are made for each of the statistically significant oscillatory components of river flow, by reconstructing each component using singular spectrum analysis. These composites confirm the influence of ENSO on the streamflow variability of the Negro and Uruguay Rivers, with El Niño associated with enhanced streamflow. On the decadal timescale, high river runoff is associated with anomalously cool SSTs over the tropical North Atlantic. A very similar near-decadal oscillation in SST over this region is identified separately from a rotated empirical orthogonal function analysis of gridded annual mean SSTs. The near-decadal component of the Paraguay and Paraná Rivers is strongest in the austral summer. Atmospheric sciences Climate change 11 10 2570 2581 1998-10 http://dx.doi.org/10.1175/1520-0442(1998)011<2570:IADCIR>2.0.CO;2 http://hdl.handle.net/10022/AC:P:14378 NNC NNC 2012-08-14 14:31:13 -0400 2012-08-14 14:35:01 -0400 8398 eng