Hydrographic conditions along the western Iberian margin during marine isotope stage 2

Type Article
Date 2009-12-01
Language English
Author(s) Voelker A. H. L.1, 2, de Abreu L.1, 2, Schoenfeld J.3, Erlenkeuser H.3, 4, Abrantes F.1
Affiliation(s) 1 : Lab Nacl Energia & Geol, Unidade Geol Marinha, P-2721866 Amadora, Portugal.
2 : CIMAR Associate Lab, P-4050123 Oporto, Portugal.
3 : Univ Kiel, Leibniz Inst Marine Sci, IFM GEOMAR, D-24148 Kiel, Germany.
4 : Univ Kiel, Leibniz Labor Altersbestimmung & Isotopenforsch, D-24118 Kiel, Germany.
Source Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2009-12-01 , Vol. 10 , N. 12 , P. 1-30
DOI 10.1029/2009GC002605
WOS© Times Cited 51
Keyword(s) Iberian margin, Last Glacial Maximum, Heinrich events, planktonic foraminifer, stable isotopes, productivity
Abstract The surface water hydrography along the western Iberian margin, as part of the North Atlantic's eastern boundary upwelling system, consists of a complex, seasonally variable system of equatorward and poleward surface and subsurface currents and seasonal upwelling. Not much information exists to ascertain if the modern current and productivity patterns subsisted under glacial climate conditions, such as during marine isotope stage (MIS) 2, and how North Atlantic meltwater events, especially Heinrich events, affected them. To help answer these questions we are combining stable isotope records of surface to subsurface dwelling planktonic foraminifer species with sea surface temperature and export productivity data for four cores distributed along the western and southwestern Iberian margin (MD95-2040, MD95-2041, MD99-2336, and MD99-2339). The records reveals that with the exception of the Heinrich events and Greenland Stadial (GS) 4 hydrographic conditions along the western Iberian margin were not much different from the present. During the Last Glacial Maximum (LGM), subtropical surface and subsurface waters penetrated poleward to at least 40.6 degrees N (site MD95-2040). Export productivity was, in general, high on the western margin during the LGM and low in the central Gulf of Cadiz, in agreement with the modern situation. During the Heinrich events and GS 4, on the other hand, productivity was high in the Gulf of Cadiz and suppressed in the upwelling regions along the western margin where a strong halocline inhibited upwelling. Heinrich event 1 had the strongest impact on the hydrography and productivity off Iberia and was the only period when subarctic surface waters were recorded in the central Gulf of Cadiz. South of Lisbon (39 degrees N), the impact of the other Heinrich events was diminished, and not all of them led to a significant cooling in the surface waters. Thus, climatic impacts of Heinrich events highly varied with latitude and the prevailing hydrographic conditions in this region.
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