THE SEA SURFACE TEMPERATURE AND OXYGEN ISOTOPE CHANGES IN THE WESTERN PACIFIC WARM POOL DURING THE MID-PLEISTOCENE TRANSITION PERIOD

The oxygen isotopic data of planktonic and benthic foraminifera, combined with the Mg/Ca ratio of planktonic foraminifera for the interval of 12.54~16.38 m of the core taken at Ocean Drilling Program (ODP) Site 807A were used to reveal the sea surface temperature (SST) and oxygen isotope change history in the western Pacific Warm Pool (WPWP) during the mid-Pleistocene transition period 800~1000 kaBP. During this period, the SST at ODP 807 changed from 25.1℃ to 30.9℃ with an average of 28.4℃ and the glacial/interglacial differences reached 1.5~5℃, similar to the difference in late Quaternary. Meanwhile, the SST and benthic oxygen isotope changed synchronously. There is no obvious leading or lagging phase relationship between them, different from the previous results in this area. In the interglacials, the pattern of high SST, deeper thermocline and lower salinity at ODP 807 were analogous to the modern La Niña in the WPWP; while in the glacials, the proxy variations in accord with the modern El Niño condition. During the mid-Pleistocene transition period, the changes in SST and depth of thermocline (DOT) at ODP 807 were forced mainly by the low latitude tropical driving, and both showed a strong precession signal (16.8 ka). However, the benthic oxygen variations are affected by high latitude.