HR: 10:35h
AN: PP52B-02 INVITED    [Abstracts]
TI: Multi-Isotope (13C, 14C, D/H) Insights into Abrupt Climate Shifts in the Tropical Atlantic Basin
AU: * Drenzek, N
EM: ndrenzek@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
AU: Hughen, K
EM: khughen@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
AU: Eglinton, T
EM: teglinton@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
AU: Bice, M
EM: mbbice@wm.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
AU: Montlucon, D
EM: dmontlucon@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
AU: Sessions, A
EM: als@gps.caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, United States
AU: Druffel, E
EM: edruffel@uci.edu
AF: Department of Earth System Science, University of Califoria Irvine, Irvine, CA 92697, United States
AU: Southon, J
EM: jsouthon@uci.edu
AF: Department of Earth System Science, University of Califoria Irvine, Irvine, CA 92697, United States
AU: dos Santos, G
EM: gdossant@uci.edu
AF: Department of Earth System Science, University of Califoria Irvine, Irvine, CA 92697, United States
AB: Organic geochemical investigations of climate evolution in the tropical Atlantic, which models suggest was sensitive to changes in both the high latitude Atlantic and low latitude Pacific sectors during the last glacial cycle, promise to clarify the origins of high frequency variability observed in many proxy records across the globe. We reconstruct precipitation changes in the western tropical Atlantic over the past 200,000 years using the stable carbon and hydrogen isotopic compositions of higher plant leaf waxes preserved in the Cariaco Basin. Results indicate that less rain fell over northern South America during stadial periods relative to interstadials. Moreover, the severity of these dry events was modulated by precessionally driven oscillations in local insolation, such that droughts concurrent with periods of increased solar heating were less severe than those associated with insolation minima, and vice versa. Detailed molecular level radiocarbon measurements in the modern environment indicate that a significant portion of these leaf wax compounds are pre-aged by several thousand ¹⁴C years within the adjacent drainage basin before ultimate incorporation in marine sediments. Climate records based on their corresponding stable isotopic signatures might therefore be offset in both timing and amplitude from the paleoenvironmental shifts they document. Nevertheless, much of the original climatic information is likely preserved by the remaining component, which is delivered to the ocean within ten to twenty years of biosynthesis. Together these findings suggest that while additional care must be taken in the interpretation of phase and amplitude relationships, reconstructions based on vascular plant biomarkers offer tremendous insight into the origins of abrupt climate change in the past.
DE: 0428 Carbon cycling (4806)
DE: 1055 Organic and biogenic geochemistry
DE: 1620 Climate dynamics (0429, 3309)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4914 Continental climate records
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting