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Climate of the Past An interactive open-access journal of the European Geosciences Union
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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 15 Feb 2019

Submitted as: research article | 15 Feb 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Climate of the Past (CP).

Centennial-scale precipitation anomalies in the southern Altiplano (18° S) suggest an extra-tropical driver for the South American Summer Monsoon during the late Holocene

Ignacio A. Jara1, Antonio Maldonado1,2,3, Leticia González4, Armand Hernández4, Alberto Sáez5, Santiago Giralt5, Roberto Bao6, and Blas Valero-Garcés7,8 Ignacio A. Jara et al.
  • 1Centro de Estudios Avanzados en Zonas Áridas (CEAZA), Colina del Pino, La Serena, Chile
  • 2Instituto de Investigación Multidisciplinario en Ciencia y Tecnología, Universidad de La Serena, La Serena, Chile
  • 3Departamento de Biología Marina, Universidad Católica del Norte, Larrondo 1281, Coquimbo, Chile
  • 4Instituto Ciencias de la Tierra Jaume Almera-CSIC, Barcelona, Spain
  • 5Departament de Dinàmica de la Terra i de l’Oceà. Universitat de Barcelona, Spain
  • 6Centro de Investigacións Científicas Avanzadas (CICA), Facultade de Ciencias, Universidade da Coruña, A Coruña, Spain
  • 7Instituto Pirenaico de Ecología – CSIC, Zaragoza, Spain
  • 8Laboratorio Internacional de Cambio Global, CSIC-PUC-UFRJ, Zaragoza, Spain

Abstract. Modern precipitation anomalies in the Altiplano region of South America are closely linked to the strength of the South American Summer Monsoon (SASM) which is influenced by large-scales climate components sourced in the tropics such as latitudinal shifts of the Intertropical Convergence Zone (ITCZ) and El Niño-Southern Oscillation (ENSO). However, the timing, direction and spatial extent of precipitation changes prior to the instrumental period are still largely unknown, preventing a better understanding of the long-term drivers of the SASM and their effects over the Altiplano. Here we present a detailed pollen reconstruction from a sedimentary sequence covering the period between 4500–1000 cal yr BP in Lago Chungará (18° S; 4570 masl), a high elevation lake in the southwestern margin of the Altiplano where precipitation is delivered almost exclusively during the mature phase of the SASM in the austral summer. We distinguish three well-defined centennial-scale anomalies, with dry conditions between 4100–3300 and 1600–1000 cal yr BP, and a conspicuous humid interval between 2400–1600 cal yr BP; which resulted from weakening and strengthening of the SASM respectively. Comparisons with other climate reconstructions from the Altiplano, the Atacama Desert, the Tropical Andes and the southwestern Atlantic coast reveal that – unlike the modern climatological controls – past precipitation anomalies at Lago Chungará were largely decoupled from north-south shifts in the ITCZ and ENSO. A regionally coherent pattern of centennial-scale SASM variations and a significant latitudinal gradient in precipitation responses suggest the contribution of an extra-tropical moisture source for the SASM, with significant effects over precipitation variability in the Southern Altiplano.

Ignacio A. Jara et al.
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Ignacio A. Jara et al.
Ignacio A. Jara et al.
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Short summary
The South American Summer Monsoon (SASM) is the most significant climate feature of South America. However, little is known about SASM variability in the past. Here we present a new SASM reconstruction from Lago Chungará in the southern Altiplano (18° S). We show important changes in SASM strength at centennial timescales. Our results suggest that SASM variability in the southern Altiplano was not only controlled by tropical features, but also influenced by an extra-tropical precipitation.
The South American Summer Monsoon (SASM) is the most significant climate feature of South...