HR: 1340h
AN: PP33B-0948    [Abstracts]
TI: Intensified North Atlantic Deep Water During Middle Pliocene Warm Period?
AU: * Dwyer, G S
EM: gsd3@duke.edu
AF: Division of Earth and Ocean Sciences, Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708 United States
AU: Cronin, T M
EM: tcronin@usgs.gov
AF: U.S. Geological Survey, MS 955, Reston, VA 20192 United States
AU: Dowsett, H J
EM: hdowsett@usgs.gov
AF: U.S. Geological Survey, MS 955, Reston, VA 20192 United States
AU: Chandler, M
EM: mac59@columbia.edu
AF: Goddard Institute for Space Studies, Columbia University, 2880 Broadway, New York, NY 10025 United States
AB: We examined the hypothesis of intensified thermohaline circulation/North Atlantic Deep Water (NADW) production during the Middle Pliocene warm period (3 - 3.3 Ma) by reconstructing deep ocean temperature from four sites (3.0 - 4.4 km water depth) in the western equatorial Atlantic using ostracode Mg/Ca ratios. Results indicate an overall steeper thermal gradient compared to modern conditions along the depth transect. Much of the shift is due to warmer water temperatures at the shallower sites, a pattern of warming similar to that observed in the deep North Atlantic during the warm early Holocene. Such a pattern is consistent with an intensification of NADW production relative to modern conditions. In addition to the shift in mean temperatures, the results suggest orbital-scale variability in deep Atlantic temperature during the middle Pliocene, especially at the shallower sites. This in turn suggests further intensification, as well as intermittent weakening, of NADW during the middle Pliocene warm period.
DE: 1600 GLOBAL CHANGE (New category)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting