HR: 10:20h
AN: PP41D-01    [PDF]
TI: Radiocarbon Record of Rapid Deep Water Production Changes During the Last Deglaciation
AU: * Cao, L
EM: lcao@ldeo.columbia.edu
AF: Li Cao, Lamont Doherty Earth Observatory, Columbia University, Rt.9W, Palisades, NY 10964 United States
AU: Fairbanks, R G
EM: fairbanks@ldeo.columbia.edu
AF: Li Cao, Lamont Doherty Earth Observatory, Columbia University, Rt.9W, Palisades, NY 10964 United States
AU: Mortlock, R
EM: mortlock@ldeo.columbia.edu
AF: Li Cao, Lamont Doherty Earth Observatory, Columbia University, Rt.9W, Palisades, NY 10964 United States
AU: Guilderson, T P
EM: tguilderson@llnl.gov
AF: Thomas P. Guilderson, Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94551 United States
AB: Several dramatic excursions in the oxygen isotope values of Greenland ice cores and corresponding increases in polar sea ice extent occur during the last deglacial interval. The fate of North Atlantic Deep Water (NADW) during these brief excursions is of great interest but is poorly documented due to a lack of high-resolution proxies of NADW. We have generated two high-resolution marine $\Delta$$^{14}$C records spanning 10,500 to 15,000 years BP based on paired thorium/uranium and radiocarbon age determinations on corals collected offshore Barbados (13$^{o}$13'N, 59$^{o}$32'W) in the western tropical Atlantic and Kiritimati Atoll (1$^{o}$99'N, 157$^{o}$78'W) in the central equatorial Pacific. Our marine records both show a series of $\Delta$$^{14}$C fluctuations averaging 35$\pm$10 per mil in amplitude. Intervals of increasing $\Delta$$^{14}$C values correspond to the extreme low oxygen isotope intervals, indicating reduced deep-water production during cold events in the North Atlantic region. The concordance between our tropical Atlantic and Pacific $\Delta$$^{14}$C records (reservoir corrected) and their overlap with the floating tree ring $\Delta$$^{14}$C chronology of Freidrich et al., (1999) between 13,200 and 14,200 years before present, strongly indicates that the ocean is the source of these $\Delta$$^{14}$C fluctuations. Our coral $\Delta$$^{14}$C records compare well with the $\Delta$$^{14}$C record from the varved sediments of the Cariaco Basin (Hughen et al., 2000) from 10,500 to 12,900 years BP,but are markedly different from the Cariaco record from 12,900 to 14,700 years BP. A simple box diffusion carbon cycle model (Oeschger et al., 1975) reproduces the oceanic and atmospheric $\Delta$$^{14}$C fluctuations using a fifty percent reduction in the deep water production diffusion term. Our thorium/uranium age determinations provide precise and accurate dates on the initial increases and decreases of deep-water production and the exact duration of the fluctuations.
DE: 1620 Climate dynamics (3309)
DE: 3322 Land/atmosphere interactions
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 3344 Paleoclimatology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting