Charateristic Of The Upper Sea Water In Ninetyeast Ridge And Paleoclimatic Implication In The Late Pleistocene

Indonesian Throughflow(ITF) is an important part of the thermohaline circulation.The equatorial Pacific warm water enter the Indian Ocean by transporting of ITF,thus it plays an important role in the heat and salt exchange between Pacific and Indian Ocean.The sediments of core MD77-151 which located in Ninetyeast Ridge(NER) on the path of thermohaline circulation,it can be a good corresponding to the ITF in the Indian Ocean.By testing Mg/Ca and δ18O in shells of Globigerinoides ruber and Mg/Ca in shells of Pulleniatina obliquiloculata,sea surface temperature (SST),thermocline water temperature (TWT) and sea surface salinity (SSS) through the last 150ka were reconstructed in northeast of Indian Ocean.Compared with SST records in different ocean, we discuss the climate change in study area response to the globe change in history.In addition, we test the state of ITF in Indian Ocean.Results show that SST in NER warming 2.83 ℃ in Termination II (T2),timing of rapid heat is consistent with climate record in other oceans and polar regions,which reflects earth orbit parameters have a strong control to the globe climate change.Previous studies have demonstrated upper structure of ITF in Indonesian archipelago have changed a lot between glacial and inglacial stages,but what happened in Indian Ocean is still uncertain.The variability of vertical temperature gradient(ΔT,ΔT=SST-TWT)in the NER can reflect the fluctuation of the depth of thermocline(DOT).A comparison between the ΔT from core MD77-151,MD98-2172 and MD01-2378 suggests shallower DOT in interglacial period and deeper DOT in glacial period.The same trend testify the condition of ITF have no changed when flowing through Indian ocean.Compareing with the core ODP806B,for the strengthen of the surface ITF, the temperature difference decease while the Indian Pacific Warm Pool(IPWP) enlarging in interglacial period.The temperature difference increase corresponding to the strengthen of the cold subsurface ITF during the IPWP shrinking in glacial.This can be an evidence to prove the ITF plays an important role in the heat-transfer process between Indian and Pacific ocean.