Long-term solar activity influences on South American rivers

TL;DR

This study demonstrates that solar activity significantly influences river streamflows and precipitation patterns in South America, with higher solar activity correlating with increased water levels across multiple rivers and regions.

Contribution

It provides new evidence linking solar activity to regional hydrological variability in South America, including historical context and multiple river systems.

Findings

Strong positive correlation between solar activity and river streamflows.

Historical low water levels during the Little Ice Age linked to low solar activity.

Solar activity influences precipitation in both summer and winter across the region.

Abstract

River streamflows are excellent climatic indicators since they integrate precipitation over large areas. Here we follow up on our previous study of the influence of solar activity on the flow of the Parana River, in South America. We find that the unusual minimum of solar activity in recent years have a correlation on very low levels in the Parana's flow, and we report historical evidence of low water levels during the Little Ice Age. We also study data for the streamflow of three other rivers (Colorado, San Juan and Atuel), and snow levels in the Andes. We obtained that, after eliminating the secular trends and smoothing out the solar cycle, there is a strong positive correlation between the residuals of both the Sunspot Number and the streamflows, as we obtained for the Parana. Both results put together imply that higher solar activity corresponds to larger precipitation, both in summer and in wintertime, not only in the large basin of the Parana, but also in the Andean region north of the limit with Patagonia.