HR: 1340h
AN: PP13A-0589    [Abstracts]
TI: PAST RADIOCARBON PROFILES FROM DEEP-SEA CORALS IN THE NORTH ATLANTIC
AU: * Robinson, L F
EM: laurar@gps.caltech.edu
AF: California Institute of Technology, 120E California Boulevard, Pasadena, CA 91125 United States
AU: Adkins, J F
EM: jess@gps.caltech.edu
AF: California Institute of Technology, 120E California Boulevard, Pasadena, CA 91125 United States
AU: Fernandez, D P
EM: diego@gps.caltech.edu
AF: California Institute of Technology, 120E California Boulevard, Pasadena, CA 91125 United States
AU: Wang, S L
EM: jslw@gps.caltech.edu
AF: California Institute of Technology, 120E California Boulevard, Pasadena, CA 91125 United States
AB: Deep-sea corals are an excellent archive of ocean history since their aragonitic, uranium-rich skeletons are well suited to U-Th dating. This independent dating technique means that 14C is no longer needed for chronometry and can be used to reconstruct radiocarbon profiles of the water column. We have many thousands of coral individuals ranging in depth from 1000 - 2500 m and the first 100 U-Th dates show a bias towards ages of the last glacial and deglaciation. These samples are ideally suited to monitoring the variable depth of the contact between Northern and Southern sourced waters. Initial radiocarbon data exhibit D14C gradients with depth that are large compared to the smooth profile observed in the modern ocean. Samples from one depth (~1750m) but with ages spanning Heinrich 1 through to the Younger Dryas not only reflect the events seen in global records, but also demonstrate transient deep-sea circulation changes. These transient D14C excursions are observed to occur abruptly, even within the lifetime of one coral (~100 years). In addition, these samples allow us to investigate the controls on the atmospheric 14C/12C record, namely the interplay between the production rate of 14C and its removal by ocean circulation. Combining this radiocarbon data with passive tracers of the mixing ratio of Northern to Southern sourced water would allow us to calculate ventilation rates for the deep ocean. Ultimately, we aim to reconstruct ventilation rates for the NW Atlantic through the last glacial and deglaciation.
DE: 4267 Paleoceanography
DE: 4271 Physical and chemical properties of seawater
DE: 1045 Low-temperature geochemistry
DE: 1050 Marine geochemistry (4835, 4850)
DE: 1000 GEOCHEMISTRY (New field, replaces Rock Chemistry)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting