Temperature and productivity changes off the western Iberian margin during the last 150 ky

• Published in: Quaternary science reviews 2010-03, Vol.29 (5), p.680-695
• Main Authors: Salgueiro, E., Voelker, A.H.L., de Abreu, L., Abrantes, F., Meggers, H., Wefer, G.
• Format: Article
• Language: English
• ISSN: 0277-3791; 1873-457X
• DOI: 10.1016/j.quascirev.2009.11.013

Present day hydrographic conditions along the western Iberian margin are characterized by seasonal upwelling with filaments that can penetrate more than 200 km into the open ocean and constitute areas of cold and highly productive waters. In order to investigate spatial and temporal gradients in temperature and productivity conditions during the last 150 ky, high-resolution proxy records were generated in 3 cores (SU92-03, MD95-2040, MD95-2042), located along the Iberian coast between 43°12′N and 37°48′N and forming a N–S profile. In all cores, planktonic foraminifera census counts are used to reconstruct summer sea surface temperature (SST su) and export productivity (Pexp su) using the modern analog technique SIMMAX 28. SST su and Pexp su values similar to the present are observed throughout the Holocene and MIS 5e periods for each site, respectively, indicating fairly stable conditions equivalent to the modern ones. On glacial/interglacial timescales, SST su increases by 2–3 °C from the northern to southernmost site. Pexp su, on the other hand, shows a decrease of 30–40 gC/m 2/yr from North to South at present time and during interglacial periods, and no significant variation (90–100 gC/m 2/yr) during glacial periods. The northernmost core SU92-03 reveals the coldest conditions with records more similar to MD95-2040 than to MD95-2042, the later of which is, as at present, more affected by subtropical waters. Core SU92-03 shows higher interglacial productivity similar to open ocean mid- to high latitude sites, while the other two cores monitor higher glacial productivity conform with other upwelling sites off NW Africa. A boundary between differences in glacial/interglacial productivity appears to be present in our study between 43°12′N and 40°35′N. Especially north of 40°N, coldest SST su and lowest Pexp su are found during Heinrich events (H)1–H8 and H10–H11. In contrast, lowest Pexp su do not coincide with these events at site MD95-2042, but appear to be related to the presence of relatively warm and nutrient-poor subtropical Eastern North Atlantic Central Water advected with the Azores Current.