HR: 09:30h
AN: PP11C-07    [Abstracts]
TI: North Atlantic Abyssal Circulation During Heinrich Event 1
AU: Burke, A
EM: aburke@whoi.edu
AF: Woods Hole Oceanographic Institution, Department of Geology and Geophysics, Woods Hole, MA 02543, United States
AU: * Marchal, O
EM: omarchal@whoi.edu
AF: Woods Hole Oceanographic Institution, Department of Geology and Geophysics, Woods Hole, MA 02543, United States
AU: Francois, R
EM: rfrancois@eos.ubc.ca
AF: The University of British Columbia, Earth and Ocean Sciences Bios 1452, Vancouver, BC V6T 1Z4, Canada
AB: Pa-231/Th-230 ratios in three sediment cores from the North Atlantic have been used to infer changes in the meridional overturning circulation (MOC) over the past 20 kyr. The large Pa-231/Th-230 ratios (approaching the production ratio of the two radionuclides in the water column) during Heinrich Event 1 (H1) in core OCE326-GGC5 off of the Bermuda rise have been interpreted in terms of a reduced export of Pa-231 to the Southern Ocean owing to a slow-down of the MOC (McManus et al., Nature, 2004). Similar observations have been found in core SU81-18 from the Iberian continental margin (Gherardi et al., EPSL, 2005). The Pa-231/Th-230 record for core DAPC2 from the Norwegian Sea also has elevated values during H1, although variations in the flux of biogenic opal might be an important factor in controlling Pa-231/Th-230 ratios in the sediment (Hall et al., GRL, 2006). Here we will use an inverse method to combine Pa-231/Th-230 observations for H1 in these three cores with a model of the abyssal circulation in the North Atlantic basin. Two null hypotheses will be tested. The first null hypothesis is that the Pa-231/Th-230 data are consistent with the modern circulation. The second is that these data are consistent with a state of no flow in the abyssal region. In testing each hypothesis, due regard will be given to the uncertainties in both the Pa-231/Th-230 data and the model equations. By comparing the adjustments in the Pa-231/Th-230 values that are necessary to bring them into consistency with the modern circulation (hypothesis 1) and the state of rest (hypothesis 2), insight into the dynamical information contained in these data will be gained.
DE: 4924 Geochemical tracers
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting