Assessment of sea surface temperature variations in the central North Atlantic using the alkenone unsaturation index (U₃₇(k'))

A high resolution record of U₃₇(k')-derived SST estimations has been obtained in a core from the central North Atlantic Ocean (SU90/08, 43°30'N, 30°24'W) spanning a time period of 280 ky. The general trend of the U₃₇(k') profile parallels closely the δ¹⁸O signal and represent an independent confirmation that the SST variations in the glacial-interglacial time scales are correlated with the northern ice sheets evolution. In contrast to the CLIMAP (1984) conclusions based on the foraminiferal transfer function technique, the SST during the last interglacial period (LIP, isotopic stage 5.5) are 2-3°C warmer than during the Holocene. This result is in good agreement with many studies based in coastal and continental records that strongly suggest warmer climatic conditions over North America and Europe. Finally, the SST estimates during the last glacial maximum (LGM, 18 kyBP) where 4.5°C cooler than during the previous glacial period (PGP, stage 6). We argue that this difference is caused by a northward position of the polar front during the PGP in the Central North Atlantic.