+A 5680-year tree-ring temperature record for southern South America

It is widely documented that the Earth’s surface temperatures have increased in recent decades. However, temperature increment patterns are not uniform around the globe, showing different or even contrasting trends. Here we present a mean maximum summer temperature record, based on tree-ring widths, over the past 5682 years (3672BC e 2009AD) for southern South America (SSA), covering from mid-Holocene to the present. This is the longest such record for the Southern Hemisphere (SH), and expands available annual proxy climate records for this region in more than 2060 years. Our record explains 49% of the temperature variation, and documents two major warm periods between 3140 e2800BC and 70BC e 150AD, which coincide with the lack of evidence of glacier advances in SSA. Recent decades in the reconstruction (1959e2009) show a warming trend that is not exceptional in the context of the last five millennia. The long-term relationship between our temperature reconstruction and a reconstructed total solar irradiance record, with coinciding cycles at 293, 372, 432e434, 512 and 746 years, indicate a persistent influence of solar forcing on centennial climate variability in SSA. At interannual to interdecadal scales, reconstructed temperature is mainly related to the internal climate variability of the Pacific Ocean, including El Nino Southern Oscillation (ENSO) and longer oscillations. Our ~ study reveals the need to characterize regional-scale climate variability and its drivers, which in the context of global-scale processes such as anthropogenic warming, interact to modulate local climate affecting humans and ecosystems.Fil: Lara, Antonio. Center for Climate and Resilience Research; Chile. Universidad Austral de Chile; Chile. Fundación Centro de los Bosques Nativos; ChileFil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Urrutia Jalabert, Rocío. Center for Climate and Resilience Research; Chile. Instituto Forestal; Chile. Universidad Austral de Chile; ChileFil: González Reyes, Álvaro. Center for Climate and Resilience Research; Chile. Universidad Austral de Chile; Chile. Universidad Mayor; ChileFil: Aravena, Juan Carlos. Universidad de Magallanes; ChileFil: Luckman, Brian Henry. Western University; CanadáFil: Cuq, Emilio. Universidad Austral de Chile; ChileFil: Rodríguez, Carmen Gloria. Universidad Austral de Chile; ChileFil: Wolodarsky Franke, Alexia. Cooperativa Calahuala; Chil

Tree-ring based reconstruction of Río Bermejo streamflow in subtropical South America

Precipitation on the subtropical Andes in northwestern Argentina is the main source of freshwater to rivers, which provide water for consumption, hydroelectric generation and irrigation of agricultural fields. Regional streamflow records for the past 60years indicate a period of enhanced inter-annual and inter-decadal variability during recent decades. Here we present a long-term perspective of streamflow variations for Río Bermejo, a major river in the subtropics of Argentina-Bolivia. This streamflow reconstruction covers the period 1680-2001 and was performed using principal component regression models based on precipitation sensitive tree-ring width series. Composite tree-ring chronologies from Juglans australis, Cedrela lilloi and Schinopsis lorentzii were used as predictors to reconstruct the May-October (dry season) streamflow variations. Monthly instrumental streamflow records were used to assess the temporal relationship between climatic data and tree-ring records. The regression model explains 52% of the variance of May-October Bermejo discharge (R2 adj=0.499) over the period 1941-1992. Analyses of the frequency, intensity and duration of pluvials and droughts indicates a sustained increase in streamflow since the 1960s, which is exceptional since 1680. Pearson's correlation coefficients between Río Bermejo records against gridded interpolated precipitation and outgoing longwave radiation indicate that the South American monsoon is the main source of regional precipitation and the consequent discharge of subtropical rivers in northern Argentina. Long-term streamflow reconstructions in subtropical South America contribute to our understanding of past and present climate variations and the related large-scale atmospheric features that drive these variations.Fil: Ferrero, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: De Membiela, Mónica. Universidad Politécnica de Madrid; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Ferri Hidalgo, Lidia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Luckman, Brian Henry. University of Western Ontario. Department of Geography; Canad