The Last160ka Upper Wate Structure And Properties Of The Eastern Timor Sea And Paleoceanography Implication

The tropical processes play a major role in affecting global climate change. The Timor Sea islocated in the Indo-Pacific Warm Pool and is the main path of outflow of Indonesian throughflow. Theproperties of the upper water mass of the Timor Sea are affected by the monsoon, IndonesianThroughflow and El Nino Southern Oscillation.The sediments of core MD98-2172which located in the eastern Timor Sea within the main path ofoutflow of ITF was studied. Sea surface temperature (SST), sea surface salinity (SSS) and thermoclinewater temperature (TWT) were reconstructed through the last160ka by testing Mg/Ca and δ18O inshells of Globigerinoides ruber and Mg/Ca in shells of Pulleniatina obliquiloculata. We explored theimpact of ITF, monsoon and ENSO on the character of upper water of the Timor Sea. Compared withthe proxy of insolation, climate change of the north and south pole, Asian monsoon variability andother regional sea surface temperature, combined with spectral and cross spectral analysis, wediscussed the response and role with the global climate change.Results show that the SST records exhibit substantial glacial-interglacial cycle, with4.2℃warming during the last deglaciation and TWT have a4℃warming through the last glacial maximumto the early Holocene. Two cold events occurred during deglaciation in SST, which are correspondingwith Younger Drays (YD) and Heinrich event1(H1) respectively. The SST records vary in the samephase with climate change which recorded in the Antarctic ice core and suggests that there is a closelylink between tropical sea and climate change of high latitudes. A strongly declined (3℃) was seen inTWT records. The difference between SST and TWT had been increasing through the Holocene,indicating the shoaling of thermocline depth. We speculate that the sea level rise, monsoon activity andthe condition of ENSO played an important role in influencing thermocline depth of the ITF outflow.The trend of sea surface temperature variability of MD98-2172is consistent with the temperaturerecords in the Antarctic region. Although different region has a different background of atmosphericcirculation and hydrology, all the SST data from different region have similar glacial-interglacialvariability in Milankovitch time scale. We argue that the main cause of controlling the SST variabilityis the insolation.I explored the difference between SST of MD98-2172and MD06-3067and ODP-806B which islocated in the center of Western Pacific Warm Pool. The result shows that the SSTs are the same in twoplaces during MIS1and MIS5, while there is a significant difference of SST in these two regionsduring relative colder MIS2, MIS3, MIS4and MIS6. We proposed that the WPWP was smaller andweaker during cold periods.The result of spectral analysis shows that the δ18Osw which has been corrected by sea levelchange has a very strong10ka and23ka cycle. We also find the same cycle in δ18Osw of MD06-3067and the eastern Asian monsoon index. This demonstrated that the sea surface salinity in the Timor Searegion is strongly affected by the regional monsoon variability in the precession cycle bands.The index of ΔT is compared to the proxy of depth of thermocline which is calculated by thetransfer function with the planktonic foraminiferal census data. They almost have the identicalvariability. This demonstrated that the ΔT can be treated as a proxy of the variability of the thermoclinedepth in the Timor Sea region. The cross spectral analysis shows that the thermocline watertemperature leads other climate proxy of MD98-2172in both23ka and41ka cycle bands.