North Atlantic sea-surface temperature changes and the climate of western Iberia during the last deglaciation; a marine palynological approach

Sea-surface temperature (SST) variations based on δ18O and dinoflagellate cyst records in core SO75-6KL indicate that shifts in the position of the North Atlantic polar front during the last deglaciation led to sudden changes of the SST in the offshore area of Portugal. Our data show that the onset of the two major cooling events, attributed to Heinrich event 1 (H1) and the Younger Dryas (YD), occurred within 600 and 400 years, respectively. The first-order land–sea correlation, provided by the pollen record of SO75-6KL, enables a detailed evaluation of the response of the vegetation on land to altered heat and moisture transport from the North Atlantic Ocean toward SW Europe. The expansion of aridity-tolerant vegetation, as reflected in the pollen record of steppe taxa, occurred within 350 and 180 years from the onset of the cooling events connected to H1 and the YD, respectively. The inception of the warmer interval assigned to the Bølling-Allerød Interstadial shows a less sudden response, probably due to competition or to the lower migration rates for deciduous trees such as Quercus compared to most steppe taxa.