New insights into the glacial latitudinal temperature gradients in the North Atlantic. Results from U₃₇^K′ sea surface temperatures and terrigenous inputs

Sea surface temperatures (SST) and input of continental materials have been reconstructed from the study of the long-chain alkenones and n-alkanes, respectively, in a core located in the western side of the Mid-Atlantic Ridge (MD952037, 37°05′N 32°02′W, 2630 m depth). Both the long- and short-term variability recorded by the temperatures and the planktonic δ¹8O are basically the same over the last 280 kyr, showing a clear glacial/interglacial evolution. Comparison with core SU90/08, located only 6° north and directly influenced by the cold polar waters associated with the polar front during glacial times, revealed different climatic conditions during glacial periods at both locations. Whereas core MD952037 recorded similar SST values during the last two glacial periods (ca. 14-15°C), the northern core displayed colder conditions during isotopic stage 2 (8-10°C) than in stage 6 (13-15°C). These results indicate the existence of a well-developed steep north-south gradient between 37 and 43°N during the last glacial period but not during stage 6, which suggests a southern expansion of the polar front during the last glacial maximum.