HR: 08:15h
AN: PP11C-02 INVITED    [Abstracts]
TI: Antarctic Intermediate Water: Passive Responder or Climate Trigger?
AU: * Oppo, D W
EM: doppo@whoi.edu
AF: Woods Hole Oceanographic Inst., Dept. of Geology and Geophysics, Woods Hole, MA 02540,
AU: Came, R E
EM: rcame@gps.caltech.edu
AF: Now at California Institute of Technology, Division of Geological and Planetary Sciences, 100-23, Pasadena, CA 91125,
AU: Curry, W B
EM: wcurry@whoi.edu
AF: Woods Hole Oceanographic Inst., Dept. of Geology and Geophysics, Woods Hole, MA 02540,
AU: Makou, M
EM: makou.1@osu.edu
AF: Now at Byrd Polar Research Center, 108 Scott Hall, 1090 Carmack Road, Columbus, OH 43210,
AB: The Atlantic meridional overturning circulation (MOC), the system of warm-to-cold water transformation that results in North Atlantic Deep Water (NADW) production and its southward flow at depth, is a major component of the climate system and a significant source of heat to the circum-North Atlantic region. Northward flowing Antarctic Intermediate Water (AAIW) is an important constituent of the water that renews NADW formation. Early during the last deglaciation, a massive North Atlantic iceberg discharge event (Heinrich Event 1; H1) disrupted the MOC, cooling the North Atlantic and warming the southern hemisphere. It has been proposed that this warming caused melting of Antarctic ice sheet ~14,600 years ago (Meltwater Pulse 1A; MWP-1A), reducing the density of AAIW, and triggering the resumption of NADW and the abrupt warming into the Bølling period. Here, we provide evidence that enhanced penetration of AAIW into the North Atlantic began more than 1000 years before the Bølling warming, synchronously with the end of H1. The contribution of NADW to the deep North Atlantic also increased at this time, suggesting that the enhanced northward penetration of AAIW was linked to its role as a supplier of NADW, as it is in the modern ocean. We propose that the MOC recovered at this time because surface stratification decreased with the disappearance of the fresh surface waters associated with H1. The early NADW/AAIW increase and accompanying heat release caused modest warming over Greenland, suggesting that the changes in the Atlantic water masses we document were linked to changes in the MOC.
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4924 Geochemical tracers
DE: 4962 Thermohaline
DE: 9325 Atlantic Ocean
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting