A 400-year tree-ring record of the Puelo River summer–fall streamflow in the Valdivian Rainforest eco-region, Chile

Abstract

The Puelo River is a watershed shared between Chile and Argentina with a mean annual streamflow of 644 m 3 s −1 . It has a high ecologic and economic importance, including introduced farmed salmon, tourism, sports fishing and projected hydroelectricity. Using Austrocedrus chilensis and Pilgerodendron uviferum tree-ring records we reconstructed summer-fall (December-May) Puelo River streamflow, which is the first of such reconstructions developed in the Pacific domain of South America. The reconstruction goes back to 1599 and has an adjusted r 2 of 0.42. Spectral analysis of the reconstructed streamflow shows a dominant 84-year cycle which explains 25.1% of the total temporal variability. The Puelo River summer-fall streamflow shows a significant correlation (P>0.95, 1943-2002) with hydrological records throughout a vast geographic range within the Valdivian eco-region (35 to 46°S). Seasonal Puelo River interannual streamflow variability is related to large-scale oceanic and atmospheric circulation features. Summer-fall streamflows showed a significant negative correlation with the Antarctic Oscillation (AAO), whereas winter-spring anomalies appear to be positively connected with sea surface temperature variations in the tropical Pacific. In general, above-and below-average discharges in winterspring are related to El Niño and La Niña events, respectively. The temporal patterns of the observed and reconstructed records of the Puelo River streamflow show a general decreasing trend in the 1943-1999 period. Projected circulation changes for the next decades in the Southern Hemisphere would decrease summer-fall Puelo River streamflows with significant impacts on salmon production, tourism and hydropower generation.

Spatio‐temporal rainfall patterns in Southern South America

“…However, this correlation is dominated by the low-frequency trend in both series and is not significant when the two series are transformed by AR modelling. Lara et al (2008) have recently shown that stream flow in the Rio Puelo in Northern Patagonia is significantly correlated with the AAO over 1948-2000 confirming the precipitation linkage. Murúa et al (2003) also found that the AAO correlates with fluctuations in the population density of a native mouse in south-central Chile, suggesting that the available food supply for these grain-eating rodents is controlled by precipitation.…”

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“…The next step for this group is to consolidate the team, followed by a review of the available data and gaps in knowledge. Lara et al, 2008). It correlates significantly with the instrumental Rio Puelo stream flow recorded at Carrera Basilio, Chile (green line) for the period 1943-1999, at 99% confidence level (r = 0.65 (Glaciar Frías;AD 1660AD -2007 was normalized to -1.0 and the frontal variations of the other glaciers were adjusted to this range of variation.…”

Towards a global synthesis of the climate of the last two millennia

“…The next step for this group is to consolidate the team, followed by a review of the available data and gaps in knowledge. Lara et al, 2008). It correlates significantly with the instrumental Rio Puelo stream flow recorded at Carrera Basilio, Chile (green line) for the period 1943-1999, at 99% confidence level (r = 0.65 Villalba et al, (1990), Bown and Rivera (2007), and Masiokas et al (2008;2009 2) Regional Climate Dynamics; 3) Global Earth System Dynamics; and 4) HumanClimate-Ecosystem Interactions.…”

“…Research on the last 1-2 ka has resulted in several multi-proxy reconstructions of global and hemispheric temperature, and other climatic parameters (e.g., Rutherford et al, 2005;Mann et al, 2006;2008;Luterbacher et al, 2004). Despite this, we still do not sufficiently understand the precise sequence of changes related to regional climate forcings, internal variability, system feedbacks, and the responses of surface climate, land-cover, biosphere and hydrosphere.…”