Late Pliocene surface ocean conditions at the SW Iberian margin

Sensitive areas, like those of the upwelling systems, which are responsible for high ecological diversity, fisheries resources and air-sea CO₂ exchanges are threatened by climate warming, and therefore, it is crucial to understand how they behaved in past warm climates. The Iberian margin upwelling system corresponds to the northern branch of the Canary Eastern Boundary Upwelling System. At the present, seasonal upwelling of cold and nutrient-rich waters makes the margin highly productive, being responsible for the high ecological biodiversity richness in the area. Despite of its enormous ecological and social importance, the knowledge on how the upwelling system worked in the past is still limited, particularly for periods older than 900 ka. 

In this work, we focused on the reconstruction of surface water conditions during the Late Pliocene, a period characterized by warm temperatures and high atmospheric CO₂ concentration and considered as a unique analogue for future climate conditions. We studied sediments from IODP Site U1391 (37°21.5′N; 9°24.6′W, 1085 m water depth), recovered at the Southwest Iberian margin during Expedition 339, which provided for the first time, an almost continuous marine record of the SW Iberian margin dating back to the Pliocene. Surface water conditions have been reconstructed using planktonic foraminifer faunas and lipid biomarker concentrations across Marine Isotope Stages (MIS) G12 to G3 (2.84 to 2.66 Ma). The planktonic foraminifer results are being compared to the alkenone derived sea-surface temperature (SST), and the total alkenone concentration (reflecting coccolithophore productivity) records of Site U1391 in order to get a comprehensive interpretation of changes in sea surface productivity, seasonality and ecological diversity.