Timing of the intensification of Australian Monsoon during the last two terminations recorded in the deep sea sediment core from Timor Sea.

Timing of the past variations of the monsoon is a key to understand low to mid latitude climate in the past. We therefore examined a sediment core MD05-2970 obtained from Timor Sea to understand the evolution of the Australian monsoon since previous works proposed much lesser Australian monsoon during the ice ages. Radiocarbon dates as well as oxygen isotope of the planktonic foraminifers indicates that the core covers last 220 kyr which enables us to compare the last two glacial-to-interglacial climatic terminations. Our planktonic foraminiferal oxygen isotopic compositions range from -1.0 permil for the last glacial maximum to -2.8 permil for the Holocene which is consistent with the record previously reported from nearby locations.(Spooner et al., 2005). The present study showed the similar structures of oxygen isotopes between the penultimate glacial maximum and the last interglacial. However the oxygen isotope record obtained from the Makasser Strait indicated - 1.0permil and -4.0 permil respectively for the last two glacial maxima and the interglacials (Visser et al., 2003). No differences in the SST between the two core sites are recognized and hence any discrepancies in the oxygen isotopes are attributable to changes in the oxygen isotopes of seawater due to the hydrological differences. Modern satellites based observations show that the sea surface salinity in Makasser Strait is reduced as much as 4 psu during the Austral summer due to the transportation of the fresher water from the Banda Sea by Austral summer monsoon(Gordon et al., 2003). This creates the salinity difference between the Makasser Strait and the Timor Sea. On the other hand no salinity differences between the two sites were observed during the Austral winter. Therefore Austral summer monsoon was not as strong as today to create salinity differences between the two during the glacial times. Time series analyses of the two oxygen isotope curves would tell us the inception of the intensified Austral monsoon and we will discuss the timing of the intensification of the Austral monsoon during the last deglaciation as well as penultimate deglaciation.