HR: 0800h
AN: PP51D-0638    [Abstracts]
TI: Paleotemperature and Paleoproductivity Conditions off the West Iberian Margin During the Last 150 ky
AU: * Salgueiro, E
EM: emilia.salgueiro@ineti.pt
AF: Instituto Nacional de Engenharia, Tecnologia e Inovacao I.P., Dept. Geologia Marinha, Estrada da Portela, Apartado 7586, Alfragide, 2721-866 Portugal
AU: * Salgueiro, E
EM: emilia.salgueiro@ineti.pt
AF: University of Bremen, FB Geowissenschaften, Postfach 330440, Bremen, D-28359 Germany
AU: Voelker, A
EM: antje.voelker@ineti.pt
AF: Instituto Nacional de Engenharia, Tecnologia e Inovacao I.P., Dept. Geologia Marinha, Estrada da Portela, Apartado 7586, Alfragide, 2721-866 Portugal
AU: de Abreu, L
EM: luciaabreu@yahoo.com
AF: Instituto Nacional de Engenharia, Tecnologia e Inovacao I.P., Dept. Geologia Marinha, Estrada da Portela, Apartado 7586, Alfragide, 2721-866 Portugal
AU: de Abreu, L
EM: luciaabreu@yahoo.com
AF: University of Cambridge, Godwin Laboratory, Pembroke Street - New Museums Site, Cambridge, CB2 3SA United Kingdom
AU: Abrantes, F
EM: fatima.abrantes@ineti.pt
AF: Instituto Nacional de Engenharia, Tecnologia e Inovacao I.P., Dept. Geologia Marinha, Estrada da Portela, Apartado 7586, Alfragide, 2721-866 Portugal
AU: Meggers, H
EM: meggers@uni-bremen.de
AF: University of Bremen, FB Geowissenschaften, Postfach 330440, Bremen, D-28359 Germany
AB: Paleoceanographic conditions off the West Iberian margin were reconstructed in 3 cores located along a N-S profile to investigate spatial and temporal changes during the last 150 ky. The cores are SU92-03 off Cape Finisterra, MD95-2040 from the southeastern flank of the Oporto Seamount, and MD95-2042 off Cape Sines. Present day hydrographic conditions at the study area are characterized by seasonal (May to September) intense and persistent upwelling of cold and nutrient-rich North Atlantic Central Waters (NACW). Filaments of upwelled waters (mainly in proximity to the capes) penetrate more than 200 km into the open ocean. For core SU92-03, multi-proxy data were generated: planktonic and benthic foraminifera stable isotopes, carbonate content, planktonic foraminiferal assemblages and detrital grain counts. In all cores planktonic foraminifera census counts are used to reconstruct Sea Surface Temperature (SST) and Export Productivity (Pexp) with the modern analog technique SIMMAX 28, using as reference the Portuguese margin database (Salgueiro et al., submitted QSR) added to the North Atlantic surface samples used by the MARGO project. In core SU92-03, changes in oxygen isotopic values of planktonic and benthic foraminifera allowed the identification of the last two glacial - interglacial cycles back to Marine Isotope Stage (MIS) 6. High relative abundances of Neogloboquadrina pachyderma (sinistral) (>80%), the presence of small amounts of lithic grains (>150 μm) - interpreted as Ice Rafted Debris (IRD), low annual mean SST (< 5°C), and low mean May to Sept. Pexp (< 80 gC/m²/y) are associated with Heinrich events (H)1 - H6, H8, H11, and probably H7. These events are also marked by heavy planktonic and benthic δ¹⁸O values. Neogloboquadrina pachyderma (dextral) and Globigerina bulloides are the most abundant species in the SU92-03 record and show high relative abundances within the warmer MIS 5.5, 5.3, 5.1, and 1. The CaCO₃ and the mean May to Sept. Pexp follow the same trends. In all cores, coldest summer SSTs and lowest Pexps are found during the Heinrich events, only in core off Sines lowest Pexp did not coincide well with these events. Similar values to the modern summer SST and Pexp are observed during the Holocene and Eemian periods for the three sites and reveal a North - South increase of SST (2-3°C) and a decrease of Pexp (30-40 gC/m²/y), indicating that interglacial conditions were fairly stable and equal to modern conditions. During the glacial periods a North - South summer SST increase (5°C) is also seen, but no variation in summer Pexp. The northernmost core SU92-03 shows the highest SST amplitude over time, in agreement with the strongest influence of glacial polar front movements. Core MD95-2042 shows the highest Pexp amplitude indicating that the Sines upwelling filament was present during most of the studied interval, but that its intensity was affected by the southward penetration of subpolar to polar water masses.
DE: 3030 Micropaleontology (0459, 4944)
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4279 Upwelling and convergences (4964)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005