Holocene tropical South American hydroclimate revealed from a decadally resolved lake sediment δ18O record

Broxton W. Bird, Mark B. Abbott, Donald T. Rodbell, Mathias Vuille

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94 Scopus citations


Oxygen isotope ratios of authigenic calcite (δ18Ocal) measured at annual to decadal resolution from Laguna Pumacocha document Andean precipitation variability during the last 11,200years. Modern limnological data show that Pumacocha δ18Ocal reflects the average annual isotopic composition of the lake's surface waters (δ18Olw), and that δ18Olw tracks the isotopic composition of precipitation (δ18Oprecip), which is largely controlled by the intensity of the South American summer monsoon (SASM). Based on these relationships we use down-core δ18Ocal measurements as a proxy for δ18Oprecip that varies with the intensity of SASM precipitation. Pumacocha δ18Ocal increased rapidly between 11,200 and 10,300yrB.P. from -14.5% to -10.5%, reaching a maximum of -10.3% by 9800yrB.P. After 9800yrB.P., δ18Ocal underwent a long-term decrease that tracked increasing Southern Hemisphere summer insolation, suggesting that enhanced SASM precipitation was linked to precessional forcing. Higher-frequency trends did not follow insolation and therefore represent other variability in the climate system. Millennial-scale trends from Pumacocha strongly resemble those from lower-resolution tropical Andean ice and lake core isotopic records, particularly the Huascaran ice core, and low elevation speleothems. These relationships suggest that tropical Andean isotopic records reflect variations in precipitation intensity related to precessional forcing rather than tropical temperatures. They also demonstrate a coherent pattern of SASM variability, although with differences between low elevation and Andean records during the late Glacial to Holocene transition and the late Holocene. Centennial and decadal SASM precipitation variability is also apparent. Reduced SASM rainfall occurred from 10,000-9200, 7000-5000, 1500-900yrB.P. and during the last 100years. Intensifications of the SASM occurred at 5000, 2200-1500, and 550-130yrB.P. with the amplitude of variability increasing after 2200yrB.P. These periods may represent SASM responses to ocean-atmosphere variability related to orbital and radiative forcing (e.g., El Niño-Southern Oscillation and the Intertropical Convergence Zone).

Original languageEnglish (US)
Pages (from-to)192-202
Number of pages11
JournalEarth and Planetary Science Letters
Issue number3-4
StatePublished - Oct 15 2011

Bibliographical note

Funding Information:
Funding for this project was provided by the Earth System History program at the National Science Foundation . We thank Nathan Stansell, Colin Cooke, Jaime Escobar, Eden Diaz, Alijandro Chu, Michael Rosenmeier, James B. Richardson III, Matt Cavallari, and Jeffery Evens for their contributions to this research. The authors further acknowledge the University of Minnesota Limnological Research Center and the facilities, scientific and technical assistance of the Materials Micro-Characterization Laboratory of the Department of Mechanical Engineering and Materials Science, Swanson School of Engineering, University of Pittsburgh. Lastly, we thank Vera Markgraf and one anonymous reviewer for their contribution to the paper.

Copyright 2011 Elsevier B.V., All rights reserved.


  • Abrupt climate change
  • Lake sediments
  • Oxygen isotopes
  • Precessional forcing
  • South American summer monsoon

Continental Scientific Drilling Facility tags

  • SAM


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