Alkenone sea surface temperature in the Southern Ocean for the last two deglaciations

A piston core taken from the Tasman Plateau in the Southern Ocean has been studied for organic compounds to reconstruct the late Pleistocene marine environments. Here we report paleo sea surface temperature (SST) for the last two deglaciations using the unsaturation degree of alkenones (U-37(k)') preserved in the marine sediments. The U-37(k)' record indicates that the SST was at least 4 degrees C lower than the present SST at the last glacial maximum (LGM), and the amplitude of paleo-SST is at most 5.2 degrees C from the penultimate glacial (MIS-6) to the last interglacial warm period (the Eemian). Our results also demonstrate that the Eemian warm period in the Southern Ocean lasted only 3,000 years followed by a sharp cooling at around 120 kyr BP. The sharp cooling in the Southern Ocean seemed to occur a few millennia (2-3 kyrs) before the beginning of continental ice-sheet growth.