Is SST the link between solar activity and Parana river discharge?

R. COMPAGNUCCI; G. SILVESTRI; V. VELASCO

Foz do Iguazu

Congreso; AGU2010 - The meeting of the Americas; 2010

American Geophysical Union

One of the most important rivers of South America is the Paraná River extending over southern Brazil, Paraguay and eastern Argentina. The Paraná river (RIVER) discharge is related to sea surface temperature (SST) in the equatorial Pacific and the precipitation over the basin is associated to SST variability in the tropical Atlantic. Moreover, wavelet analysis revealed significant connections of solar activity with Pacific Decadal Oscillation and Southern Oscillation Index as well as with RIVER. In other words, there are evidences about the influence of Pacific and Atlantic oceans over the hydrologic variables of southern South America and new studies suggest a possible link between these variables and solar activity. Is SST the link between solar activity and Parana River discharge? This point is very important because it can help to understand the physical mechanisms connecting the solar activity and the river discharge. A hypothesis is that cosmic ray flux, modulated by solar activity, may modify cloud cover and thus surface temperature by increasing the number of ions in the atmosphere, leading to enhanced condensation of water vapor and cloud droplet formation. This mechanism could modify the rain over the Paraná basin and the river discharge. But another possible connection between the sun and river is via SST: solar activity can influences the SST and the modified SST variability could modulate the river discharge. This last option is analyzed here. A wavelet analysis was performed in order to find regions in time frequency space where the time series of SST, solar activity and river discharge co-vary. Results: 1) Strong RIVER-SST connections are observed in decadal and multidecadal temporal scales but there is also significant co-variability in shorter bands. 2) RIVER-SUN and RIVER-SST relationships have a common feature: strong co-variability around oscillations of 30 yrs which is a typical band of solar variability. This is a very important result because the tropical Pacific and the Atlantic regions have significant connection with solar activity in this band of variability. Conclusion: Connections RIVER-SUN could be possible via SST: solar activity influences the SST of Pacific and Atlantic oceans and the modified SST variability can modulate the river discharge.