Spatio-temporal variations in hydroclimate across the Mediterranean Andes (30°-37°S) since the early 20th century

Abstract

n the Mediterranean Andes (MA; 30°S?37°S), the main rivers are largely fed by melting snowpack and provide fresh water to around 10 million people on both sides of the Cordillera. Water resources in the MA are under pressure due to the extensive development of industrial agriculture and mining activities. This pressure is increasing as the region faces one of its worst recorded droughts. Previous studies have pointed to the El Niño Southern Oscillation (ENSO) as the main climatic force impacting the MA. However, the role of decadal and multidecadal climate variability, their spatial patterns and the recurrence of long-term droughts, remains poorly studied. In this contribution to a better understanding of these factors, spatial and temporal patterns of hydroclimatic variability are analyzed using an extensive database of streamflow, precipitation, and snowpack covering the period between 1910 ? 2011. These analyses are based on the combination of correlation, principal components and kernel-estimation techniques. Despite a general common pattern across the MA region, our results identify two hydroclimatic sub-regions, located north and south of 34°S. While the interannual variability associated with ENSO is slightly stronger north of 34°S, the variability associated with the Pacific Decadal Oscillation (PDO) and/or the Inter-decadal Pacific Oscillation index (IPO) shows similar patterns in both regions. However, variations produced by the IPO forcing seem to be greater in the southern sub-region since 1975. Our estimations on drought recurrence reveal a generalized increase in dry extremes since the 1950?s. These findings suggest that the northern MA are more vulnerable to changes in hydrology and climate than the southern MA.