Influence of dominant wind patterns in a distal region of the NW Iberian Margin during the last glaciation

Abstract

This work combines planktonic foraminiferal assemblages, stable isotope, transfer function estimated sea surface paleotemperatures (SST) and export productivity (Pexp) with sedimentological records from the PC7 core to document paleoclimatic and paleoceanographic changes on a distal region of the NW Iberian Margin since the last glaciation (<≈68 ka). Neodymium and strontium isotope data are also used to identify the provenance of ice rafted debris (IRD) during Heinrich event 5 (H5). Our results are compared and combined with previously published records and evidence that melt water and icebergs from the Canada, Greenland, Iceland and Europe ice sheets arrived to the NW Iberian Margin causing a significant decrease of SST during the last six Heinrich Stadials (HS) and some Dansgaard–Oeschger (D-O) stadial events. εNd and 87Sr/86Sr indicate that the studied locality mostly received sediments from European Ice Sheets (EIS) during H5. During the HS and D–O stadial events, SSTs were in general higher than in other cores collected in inner areas of the NW Iberian Margin. The presence and intensification of Portugal Current probably induced heat transfer to this distal region of the Iberian Margin. Our results also suggest the occurrence of high variability in the intensity and wind patterns during the last glaciation. In some periods, the intensity of northerly winds could have been very strong and contributed to a significant stimulation of ocean productivity in this distal area through the intensification of upwelling. In general, oceanic productivity decreased during the HS and D–O as the presence of cold and less saline water prevented nutrient rich waters from deep levels reaching the surface. The high productivity events were bracketed by periods characterized by the highest influence of the Azores Current eastern branch during which northerly winds and the oceanic productivity should have been weakened.