Late Quaternary climate variability and terrestrial carbon cycling in tropical South America
Citable URI
https://hdl.handle.net/1912/7741DOI
10.1575/1912/7741Keyword
Paleoclimatology; Climatic changesAbstract
Characterizing global and regional climate variability and climate-carbon cycle
interactions in the past provides critical context for evaluating present and future climate trends.
In this thesis, I use stable isotope and radiocarbon analysis of vascular plant biomarkers in
lacustrine and marine sediment cores to explore late Quaternary climate variability and
connections between past climate change and terrestrial carbon cycling in tropical South
America. I investigate temporal and spatial trends in South American Summer Monsoon
precipitation by reconstructing hydrologic variability over the past 50,000 years at two sites:
the Lake Titicaca drainage basin in the Central Andes and the Pantanal wetlands in the interior
lowlands. Diverging hydrologic trends at these two sites during the last glacial period suggest
altered monsoon circulation patterns under glacial conditions, while changes in summer
insolation appear to be an important control of precipitation at both sites during the Holocene. I
next assess the relationship between climate change and the age structure of terrestrial
biospheric carbon exported from two tropical catchments over the past 20,000 years.
Radiocarbon dating of leaf waxes in Cariaco Basin and Lake Titicaca sediment records
indicates that waxes preserved in sediments are likely composed of a fresh component
transported to sediments within decades of production by vegetation and an old component
derived from aged soil organic matter with an average age on the order of millennia at time of
deposition. Results from both sites show that past hydrologic variability had a significant
impact on the mobilization and export of different pools of terrestrial biospheric carbon. In
particular, results from Cariaco Basin suggest that wetter conditions in the past resulted in
increased export of fresh biospheric carbon to the ocean, representing a potentially important
climate feedback mechanism on geologic timescales.
Description
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2016
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Suggested Citation
Thesis: Fornace, Kyrstin L., "Late Quaternary climate variability and terrestrial carbon cycling in tropical South America", 2016-02, DOI:10.1575/1912/7741, https://hdl.handle.net/1912/7741Related items
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