Are southern South American Rivers linked to the solar variability?

Abstract

This article explores the Sun's influence on the hydrological cycle in southern South America (SSA) at the range of interannual‐to‐multidecadal scales from the early 1900s to 2011. The solar variability is described by the sunspot number (SSN) index. The hydrological cycle is examined by using annual mean discharges of the Paraná River (PAR) and the Atuel River (ATU) that represents the behaviour of the subtropical Argentinean Andean hydrological system. Wavelet‐based methods are used in order to describe relationships in the entire time‐frequency domain. The SSN–PAR connection is statistically weak in oscillations with period about 11 years (the Schwabe's solar cycle). Therefore, the solar forcing at this scale must be considered with great caution. The periodicity about 30 years is highly significant throughout the analysed period. Two potential physical mechanisms affecting the Paraná discharge could be involved: one is the solar irradiance influence on the Inter Tropical Convergence Zone (ITCZ), and the other is the solar influence on the Pacific long‐term variability. The SSN–ATU connection shows by far the most striking, robust and convincing result for the Schwabe cycle. A large amplitude and statistically significant cycle with a period about 11 years is observed not only in the Morlet‐based global and local wavelet spectra of the Atuel discharges and SSN but also in the global and local spectra of Cross and Coherent wavelets in most of the analysed period. High (low) discharges occur following maxima (minima) of the Schwabe cycles with time lags of up to ∼2 years. Previous studies have shown a close relationship between the subtropical Argentinean Andean Rivers and the El Niño/Southern Oscillation (ENSO), as well as a solar influence on the ENSO variability. We suggest that El Niño events occurring a few years after solar maxima could explain the connection. Periodicities longer than 30 years are suggested.

Assessing the solar variability signature in climate variables by information theory and wavelet coherence

“…Peaks of some river discharge power spectra associated with solar variability were found in the investigations 65 – 68 . Although our results are obtained from relatively short time series, they are consistent with the results found by Peña et al (2015) 69 .…”

River‐discharge dynamics in the Southern Central Andes and the 1976–77 global climate shift

“…Trend values for the complete time series (green circles) and the periods before (1952-1966; red stars), across (1967-1981; purple squares), and after (1982-1996; yellow Geophysical Research Letters 10.1002/2016GL070868 scale modes of variability, often linking discharge in tropical as well as subtropical South American rivers to El Niño-Southern Oscillation cycles [Marengo, 1995;Robertson and Mechoso, 1998;Compagnucci et al, 2000;Pasquini and Depetris, 2007;Bookhagen and Strecker, 2011]. Additional factors include solar activity [Compagnucci et al, 2014;Antico and Torres, 2015] and Pacific Decadal Oscillation phase transitions [Marengo, 2004;Jacques-Coper and Garreaud, 2015], which is also interpreted as a possible controlling factor of the climate shift in extratropical South America [Jacques-Coper and Garreaud, 2015].…”

Evolución temporal de las sequías hidrológicas en Argentina y su relación con indicadores macroclimáticos

“…Esto no sólo confirma los resultados de trabajos anteriores (Compagnucci et al, 2014;Mauas, Buccino y Flamenco, 2011;Dölling, 2014;Vargas et al, 2002), además aporta nueva información con respecto a vínculos con indicadores del océano Atlántico para las distintas cuencas. Estos resultados son importantes para el entendimiento de la dinámica macroclimática de Argentina y de su pronóstico en el espacio y en el tiempo.…”