HR: 08:30h
AN: PP31B-03 INVITED     [Abstracts]
TI: A High Resolution Record of Ocean Circulation since the last Interglacial from Nd isotopes
AU: * Goldstein, S L
EM: steveg@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 64 Rt. 9W, Palisades, NY 10964 United States
AU: Piotrowski, A M
EM: arcturus@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 64 Rt. 9W, Palisades, NY 10964 United States
AU: Hemming, S R
EM: sidney@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 64 Rt. 9W, Palisades, NY 10964 United States
AU: Fairbanks, R G
EM: fairbank@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 64 Rt. 9W, Palisades, NY 10964 United States
AU: Zylberberg, D R
EM: David.R.Zylberberg.04@alum.dartmouth.org
AF: Lamont-Doherty Earth Observatory, 64 Rt. 9W, Palisades, NY 10964 United States
AB: The variability of the global conveyor through ice ages has been a matter of dispute due to different indications from different paleocirculation proxies. Nd isotopes in marine precipitates conservatively reflect water mass mixing along their transport paths, and are changed only by addition of a new component of Nd. We present the first high resolution Nd isotope record of paleocirculation between MIS 1 and 5c from Cape Basin cores RC11-83 and TNO57-21. The record indicates a strong conveyer during warm northern hemisphere interglacial and interstadial intervals, and a weaker one during glacials and stadial intervals. The pattern of changes varies with Greenland paleotemperature. A first quantification attempt indicates that NADW export during the LGM was half the magnitude of the early Holocene. The strengthening through Termination 1 covaries with Greenland temperature and North Atlantic sea ice coverage. It markedly weakens between the Bolling and Younger Dryas. The weakening during the MIS 5a/4 transition is sharp, occurring within 1 ka. Throughout MIS 3 short-term maxima are associated with prominent interstadials in Greenland ice records (8, 12, 14, 17). Local minima at ~40 and ~62 ka may be associated with Heinrich events 4 and 6. During the ice age initiation and termination, global carbon budget shifts preceded circulation changes, and these were preceded by ice sheet growth during the initiation. There is no apparent lead-lag during interstadial warmings. The observations allow for ocean circulation to be a trigger of major climate change during abrupt events that are not driven by orbital forcing. At major glacial-interglacial boundaries, the global carbon budget and thermohaline ocean circulation both respond to the climate changes that forced the growth and decline of continental ice sheets. Overall the data show that Nd isotope ratios can be a powerful tool to trace paleocirculation history.
DE: 4267 Paleoceanography
DE: 4283 Water masses
DE: 1030 Geochemical cycles (0330)
DE: 1040 Isotopic composition/chemistry
DE: 1000 GEOCHEMISTRY (New field, replaces Rock Chemistry)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting