Alkenone sea surface temperatures in the Southern Ocean

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^k_) preserved in the marine sediments. The U^k_ record indicates that the SST was at least 4℃ lower than the present SST at the last glacial maximum (LGM), and the amplitude of paleo-SST is at most 5.2℃ from the penultimate glacial (MIS-6) to the last interglacial warm period (the Eemian). These results indicate that the amplitude of Southern Ocean SST fluctuation was twice greater than that reported by the CLIMAP projects. This larger amplitude of glacial/interglacial SST change agrees with the SST changes reconstructed from diatom assemblages in the sediments from the Indian sector Southern Ocean, which showed 5-6℃ difference for the glacial/integlacial periods [Pichon et al., 1992]. The SST decrease in the glacial Southern Ocean may be caused by northward shift of the Antarctic Polar Front (APF) at that time. 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 120kyrBP. The sharp cooling in the Southern Ocean seemed to occur a few millennia (2-3kyrs) before the beginning of continental ice-sheet growth
タンデトロン加速器質量分析計業績報告 Summaries of Researches Using AMS 1996 (平成8)年度