Multi-century tree-ring based reconstruction of the Neuquén River streamflow, northern Patagonia, Argentina

Abstract. In most cases, gauged river flow records in southern South America exist for only a few decades, hampering the detection of long-term, decadal to centennial-scale cycles and trends. Long streamflow series can be reconstructed from tree-ring records, offering the opportunity of extending the limited hydrological instrumental data for several centuries or millennia. In northern Patagonia, Argentina, the Neuquén River has great importance for local and national socio-economic activities such as hydroelectric power generation, agriculture and tourism. In this study, new and updated tree-ring chronologies from Araucaria araucana and Austrocedrus chilensis are used to reconstruct the October–June mean streamflow for the Neuquén River and place the period of gauged flows, 1903–2009, in a long-term, multi-century context. The reconstruction covers the period 1346–2000 AD and was developed through a nested principal components regression approach using a network of 43 tree-ring chronologies grouped in composite series. Analyses of the frequency, intensity, and duration of droughts and pluvial events indicate that the 20th century contains some of the driest and wettest annual to decadal-scale events in the past millennium, but longer and more severe events can also be observed in previous centuries. Blackman-Tukey and Singular Spectral Analyses identified various multi-decadal quasiperiodic oscillations with a dominant 6.8-year cycle explaining ca. 23.6% of the total variance in the Neuquén River streamflow reconstruction. We also found that the Neuquén River discharges are related to variations in the Southern Annular Mode (SAM), a measure of air mass exchanges between middle and high latitudes in the Southern Hemisphere. This association is consistent with previous studies which indicate a strong connection between rainfall patterns in northern Patagonia and SAM activity.