HR: 1340h
AN: PP53B-1389    [Abstracts]
TI: Consistent, but Regional, Patterns of Organic Carbon and Thorium Normalized Calcite Paleo-fluxes for the late Pleistocene in the Eastern Equatorial Pacific
AU: * Loubere, P
EM: paul@geol.niu.edu
AB: Biogenic production, and fluxes of labile organic carbon and calcite from the surface ocean to the deep sea, respond to both equatorial and extra-tropical forcing in the eastern Equatorial Pacific (EEP). This is an issue important to global climate change since the EEP is a major center for the transfer of carbon (as CO2) from the ocean to the atmosphere, and from the shallow ocean to the deep sea. The production and the fluxes depend on rates of coastal and equatorial divergence upwelling as well as the sources and chemistries of upwelled water. Additionally, the micronutrients Fe and Si currently limit production and the supply of these depends on both tropical and extra-tropical source areas. It has been proposed that glacial-interglacial changes in Si supply to the equatorial ocean, caused by Fe fertilization of the Southern Ocean, could have enhanced cold phase diatom production in the tropics and played a role in the Ice Age reductions of atmospheric CO2 content. If so, this effect should have been most important in the EEP region fed by upwelling off the coast of Peru (in the area of the South Equatorial Current). The Peru upwelling is fed by deep Equatorial Undercurrent water having the subantarctic of the SW Pacific as a source. We use a benthic foraminiferal transfer function for labile org. C. flux, calcite fluxes reconstructed using Thorium-normalization and correction for seabed dissolution, and Th-normalized opal accumulation rates to examine flux and diatom community response in the EEP over glacial-interglacial time. Using a suite of cores in the EEP we find that flux response is regional, but consistent for org C and calcite. Both of these show lower values along the equator and in the region affected by Peru upwelling during glacials. Both show somewhat higher values for glacials in off equatorial regions. While this might be caused by glacial shifts of the ITCZ towards the equator (away from its current position in the northern hemisphere), this will not account for opal accumulation rate data which show increases during glacials in the EEP influenced by Peru upwelling. A pattern not seen in other regions to the west and south. Our data are most consistent with biogeochemical shifts in the EEP that favor diatom production during glacials with increased HNLP conditions during interglacials. Regional production patterns and the timing of shifts indicate that the forcing came from the southern hemisphere.
DE: 4845 Nutrients and nutrient cycling
DE: 4267 Paleoceanography
DE: 3030 Micropaleontology
DE: 1615 Biogeochemical processes (4805)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting