Atlantic sea surface temperatures estimated from planktonic foraminifera off the Iberian Margin over the last 40 Ka BP

Abstract

Sea surface temperatures (SSTs)were reconstructed fromplanktonic foraminiferal assemblages in two sediment cores off the NWIberian Continental Margin for the last 40 kyr. Results of this work were compared with published SSTs estimated in six cores from the Iberian Margin and the δ18O data from NGRIP ice core of Greenland. Longitudinal and latitudinal SST changes were identified in several intervals related to alterations in the hydrographic conditions off the Iberian Peninsula, namely the influence of the upwelling system, the intensity of Paleo-Portugal and Paleo-Azores Currents, and the positions of the Polar and Arctic Fronts. During the Holocene, the SSTswere quite stable along thewest IberianMarginwhen comparedwith the last glaciation. However, during the Last Glacial Maximum(LGM) SSTswere notmuch lower than during the Holocene. The Portugal Current, as an eastward descending branch of the North Atlantic Drift, should have been quite vigorous in transporting warm water to the west Iberian Margin, which could have moderated the SSTs during the LGM. However, our results suggest a much higher instability during the LGMthan previously reported and much lower SSTs at 42°N. The lowest SSTs during the last 40 ka were recorded during the Heinrich Stadials (HS) and the Younger Dryas (YD). During the HS, SSTs at the northwest Iberian Margin were lower than today by about 10 to 16 °C as a result of the invasion of cool and low-salinity water masses and the increased transport of icebergs from the northern seas. The Polar Front was persistently situated at 42°N for ~3 ka during the HS1, and a comparable present-day Arctic Front should have been present up to the latitude of 40°Nduring the HS2, HS3, andHS4 off thewest Iberian Peninsula. The HS were recorded all along the west Iberian Margin. However, an overall trend of increasing of mean SSTs from north to south of ~8 °C during the HS1, of ~10 °C during the HS2b and HS3, of ~11 °C during the HS2a, and of ~4 °C during the HS4 was recorded. These gradients also were present during the YD of ~9 °C and the LGM of ~4 °C and may be related to the strong influence of the Paleo-Azores Current in southern areas.