Development and Application of Lacustrine Alkenone Paleothermometry in Southwestern Greenland

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Title
Development and Application of Lacustrine Alkenone Paleothermometry in Southwestern Greenland
Contributors
D'Andrea, William J (creator)
Huang, Yongsong (Director)
Herbert, Timothy (Reader)
Russell, Jim (Reader)
Saal, Alberto (Reader)
Oppo, Delia (Reader)
Brown University. Geological Sciences (sponsor)
Doi
10.7301/Z0765CJX
Copyright Date
2009
Abstract
Alkenones are lipids produced by certain haptophyte algae and are excellent sensors of temperature change. This dissertation investigates the stable isotopic and organic geochemical aspects of alkenones from brackish Greenlandic lakes and develops their use as a paleothermometer. Alkenones are reported from brackish lakes near Kangerlussuaq, Greenland and their distribution and δ13C values are examined. Results indicate that 1) the Greenland alkenones are most similar to those from lakes in Germany and Austria, suggesting a common producer organism and 2) alkenone producers must either fractionate CO2 to a greater extent than other algae or access a 13C-depleted carbon source. Haptophyte-specific ribosomal DNA (rDNA) sequences from Greenlandic lake sediment and water samples are compared with rDNA of known haptophytes, and demonstrate that the Greenlandic alkenone producers represent a new taxon of haptophyte algae, and that all Greenlandic lakes of the study contain the same haptophytes. A new liquid chromatographic procedure is reported for separating alkenones having the same carbon number but different degrees of unsaturation for the purpose of compound-specific hydrogen isotopic analysis. δD measurements on individual alkenones indicate that hydrogen isotopic composition differs according to the degree of alkenone unsaturation. This suggests it is preferable to make δD measurements on individual alkenones, due to possible temperature-related effects on "pooled" δD values and because measurements on individual alkenones provide improved precision and accuracy. Temperature variability for the past 6,000 years in Kangerlussuaq, Greenland is reconstructed by applying alkenone paleotherrmometry to sediment cores from two lakes in the region. Temperature in the Kangerlussuaq region appears to have been controlled by changes in Meridional Overturning Circulation and the extent of the North Polar Vortex on millennial timescales, while being driven by variability in the North Atlantic Oscillation over centennial timescales. The timing of major changes in Paleo-Eskimo, Norse and Inuit occupation of Southwestern Greenland coincide with episodes of abrupt temperature change revealed by the alkenone record, indicating that climatic and environmental changes played a fundamental role in the patterns of human migration in Greenland over the past 4,500 years.
Keywords
alkenone
biomarker
climate
holocene
paleoclimate
Biochemical markers
Isotopes
Climatology
Holocene Geologic Period
Limnology
Paleoclimatology
Notes
Thesis (Ph.D. -- Brown University (2009)
Extent
xix, 208 p.

Citation

D'Andrea, William J., "Development and Application of Lacustrine Alkenone Paleothermometry in Southwestern Greenland" (2009). Earth, Environmental and Planetary Sciences Theses and Dissertations. Brown Digital Repository. Brown University Library. https://doi.org/10.7301/Z0765CJX

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