Oxygen-isotope record of sea level and climate variations in the Sulu Sea over the past 150,000 years

THE Sulu Sea is located in the 'warm pool' of the western Pacific Ocean, where mean annual temperatures are the highest of anywhere on Earth. Because this large heat source supplies the atmosphere with a significant portion of its water vapour and latent heat, understanding the climate history of the region is important for reconstructing global palaeoclimate and for predicting future climate change. Changes in the oxygen isotope composition of planktonic foraminifera from Sulu Sea sediments have previously been shown to reflect changes in the planetary ice volume at glacial-interglacial and millenial timescales, and such records have been obtained for the late Pleistocene epoch and the last deglaciation(1-3). Here I present results that extend the millenial time resolution record back to 150,000 years before present. On timescales of around 10,000 years, the Sulu Sea oxygen-isotope record matches changes in sea level deduced from coral terraces on the Huon peninsula(4). This is particularly the case during isotope stage 3 (an interglacial period 23,000 to 58,000 years ago) where the Sulu Sea oxygen-isotope record deviates from the SPECMAP deep-ocean oxygen-isotope record(5). Thus these results support the ideal(4,6) that there were higher sea levels and less continental ice during stage 3 than the SPECMAP record implies and that sea level during this interglacial was just 40-50 metres below present levels, The subsequent rate of increase in continental ice volume during the return to full glacial conditions was correspondingly faster than previously thought.