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South America--Bolivia

Paleohydrology of the Subtropical Andes from Lake Records

Collaborative Effort with:

    Geoffrey Seltzer, Department of Earth Science, Syracuse University (deceased)

    Alexander Wolfe, Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton (awolfe@alberta.ca)

Images from Bolivia

Project Summary

The primary objective of this project is to produce new multi-proxy Holocene paleoclimate records from the subtropical Andes.  Previous work suggests a prolonged period of aridity during the mid-Holocene, however, more work to produce diatom and isotope records is necessary to confirm this hypothesis and determine the extent of this dry phase.  Specifically, our focus is to define the timing of changes in the precipitation-evaporation balance of the Andean Altiplano on an decadal to century timescale for the Holocene.  These records are needed to understand the long-term atmospheric dynamics of the subtropics and to assess the importance of decadal to millennial-scale shifts in the strength of summer convection.  We propose to reconstruct the Holocene climate history of the region with a series of studies analyzing the sediment, geochemical, magnetic, isotopic, and diatom content of lake cores dated at high-resolution by 210Pb and AMS 14C measurements.  A transect of sites ranging from approximately 15 to 20S in the eastern cordillera of Bolivia will be investigated. 

This research will expand the scope of our previous work in the eastern cordillera of Bolivia through additional analytical work and more extensive geographical coverage.  The resulting time-series of climatic-shifts from the new study areas will yield the necessary spatial coverage to identify patterns of regional climate change.  We hypothesize that the Andean Altiplano was significantly drier during the mid-Holocene resulting in the complete melting of cirque glaciers from watersheds with headwalls <5500 m a.s.l.  This can be tested with isotope and diatom studies to determine if the preliminary interpretation that alpine lakes were seasonally desiccated during the mid-Holocene is correct.  We also hypothesize that the cause of the drier conditions was due to the weakening of the heat-induced low-pressure cell centered over the Bolivian highlands during the wet season of the Austral summer.  We can gain insight into the cause of shifts in the precipitation-evaporation balance of the southern subtropics by examining a series of sites along a north to south transect to determine if the mid-Holocene dry phase is present and if the timing of the major shifts are synchronous within the region.  Such a record of changing effective moisture will provide insight into the long-term climate variability of subtropical South America.  Changes in water resources may have also significantly impacted prehistoric people living on the Altiplano and may again be an important environmental factor for future populations in the region.
 

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