HR: 11:35h
AN: OS32A-06    [Abstracts]
TI: Climate and Hydrologic Conditions Over Northernmost South America as Recorded in Cariaco Basin Sediments
AU: * Peterson, L C
EM: lpeterson@rsmas.miami.edu
AF: RSMAS-MGG, University of Miami, Miami, FL 33149 United States
AU: Haug, G H
EM: haug@gfz-potsdam.de
AF: GeoForschungsZentrum-Potsdam, Telegrafenberg C324, Potsdam, D-14473 Germany
AU: Murray, R W
EM: rick@bu.edu
AF: Earth Sciences, Boston University, Boston, MA 02215 United States
AU: Lea, D W
EM: lea@geol.ucsb.edu
AF: Geological Sciences, UC Santa Barbara, Santa Barbara, CA 93106 United States
AU: Hughen, K A
EM: khughen@whoi.edu
AF: Marine Chemistry/Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543 United States
AB: The Cariaco Basin has proven its worth as a remarkable repository of paleoenvironmental information in the tropical Atlantic Ocean. Laminated sediments that have accumulated rapidly in the deep basin under largely anoxic conditions preserve an "ice core-like" record of marine and terrestrial variability that can be linked to widely-distributed sites showing evidence for abrupt climate change. In Cariaco Basin, a strong modern seasonality exists because of the annual migration of the Intertropical Convergence Zone (ITCZ). On time-scales ranging from interdecadal to millennial back through marine isotope stage (MIS) 4, a coherent climatologic response is observed in sedimentary parameters that can be attributed to a pattern of ITCZ migration that mimics the seasonal cycle. During periods of cool North Atlantic sea surface temperature (SST), decreased terrigenous delivery from local rivers provides evidence of a southward shift in the mean latitudinal position of the ITCZ and its belt of convective rainfall, while a northward shift in ITCZ position can be inferred for periods of warm North Atlantic SST from increased terrigenous input to the basin. Data from MIS 5, however, at Ocean Drilling Program Site 1002 suggest an opposite pattern, with increased terrigenous delivery having occurred during the cooler portions of the last interglacial, including MIS 5b, 5d and during a clear "Younger Dryas-like" event that characterizes Termination II. To the extent that mean ITCZ position is sensitive to orbitally-induced changes in tropical insolation, we speculate that the higher amplitude of the precessionally-forced insolation signal during MIS 5 may have led to periodic migration of the Atlantic ITCZ to a position well north of Cariaco Basin. This would have left the basin more sensitive to southward excursions of the ITCZ, as opposed to today where it sits near the northern limit of the range of ITCZ motion. If true, this highlights the important role that orbital precession plays in the tropics, especially in driving the hydrological cycle.
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 1600 GLOBAL CHANGE (New category)
DE: 1620 Climate dynamics (3309)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting