HR: 10:30h
AN: PP22A-01    [Abstracts]
TI: Northern vs Southern Hemispheric Controls on Ocean Circulation from Authigenic Nd isotopes in Atlantic Sediments
AU: Piotrowski, A
EM: apio04@esc.cam.ac.uk
AF: Dept. of Earth Sciences, Downing Street, Cambridge, United Kingdom
AU: * Hemming, S R
EM: sidney@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Rt. 9W, Palisades, NY 10964 United States
AU: Goldstein, S L
EM: steveg@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Rt. 9W, Palisades, NY 10964 United States
AB: The first high resolution Nd isotope record of paleocirculation between MIS 1 and 5c from Cape Basin (South Atlantic) cores RC11-83 and TNO57-21 indicates a strong conveyer during warm intervals MIS 1 and 5 and a weaker one during MIS 4 and 2. During MIS 3 the Nd isotope pattern is variable, mimics Greenland paleotemperature variability, and thus reflects NADW intensity. The Cape Basin record shows short-term conveyor strengthening coincident with the most prominent interstadial Dansgaard-Oeschger Events (8, 12, 14, 17) in the Greenland ice record. Local minima at ~40 and ~62 ka may be associated with Heinrich events 4 and 6. During Termination 1 the pattern is unambiguously linked to Northern Hemisphere climate. For example, Piotrowski et al. (2004, 2005) show that the deglacial pattern follows Greenland temperatures and North Atlantic sea-ice cover (e.g. a stronger conveyor with higher Greenland temperatures and an ice free North Atlantic), and is independent of the Antarctic Cold Reversal. Thus the evidence strongly favors a linkage to Northern Hemisphere climate changes. The observed signal in the Cape Basin of conveyor changes can be extrapolated throughout the Atlantic. A survey of cores from 10N to 40S and a range of water depths shows that the Nd isotopes ratios of the authigenic fractions of core top samples are consistent with modern water values. Additionally, there is a consistent trend toward lesser contributions of NADW in the LGM compared to the Holocene throughout. Evidence from multiple proxies consistently indicates a shallower North Atlantic water mass, and mass balance strongly indicates a smaller total production.
DE: 0330 Geochemical cycles
DE: 1045 Low-temperature geochemistry
DE: 4267 Paleoceanography
DE: 4808 Chemical tracers
DE: 9325 Atlantic Ocean
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2005 Joint Assembly