The Upper Water Temperature And Structure Evolution In The Center West Pacific Warm Paol During The Last360

The Core KX97322-4was taken from the Ontong Java Plateau, westernequatorial Pacific. Paleotemperature obtained from quantitative and Mg/Ca analysisof planktonic foraminifera, combined with oxygen isotope data and spectral analysesof each index, revealed the glacial-interglacial variations of the oxygen isotope ofplanktonic foraminifera and the temperature and vertical structure of the upper waterin the central of the Western Pacific Warm Pool (WPWP) during the last360kyr. Ourresults indicate that, since MIS10, the oxygen isotopes and Mg/Ca of both the surfacedwelling species G.ruber and subsurface dwelling specie N.dutertrei’s showedobvious glacial-interglacial cycles. As a whole they had the same variation trendsexcept in MIS6when it inversed. The surface and subsurface waters have beeninfluenced by the volume change of high latitude ice sheets in a large scale generally,and the subsurface water is even sensitive.The Sea Surface Temperature(SST) obtained from G.ruber’s Mg/Ca the was2.9±0.7℃lower than present in the Last Glacial Maxium(LGM). The subsurfacetemperature was lower than SST but more intensive. The difference between themwas greater during the glacial earlier stage than the later stage and the subsurfacetemperature appeared fast cooling in the middle of the glacial period. It suggested thatthe subsurface water would motivate the SST variation in the glacial-interglacialcycles. The phenomenon of subsurface temperature continually higher than SST in theMIS8and MIS9/10probably due to the influence of the subsurface currents and water salinity variation, monsoons translation and weakened dissolve effect directed byglacial cooling. From the comparison of the phase of SST and δ18O we can find thatthe changes of SST is earlier than the northern hemisphere ice volume showed byδ18O’s. It can be drew that the subsurface temperature is a more important role in theglobal change from that it has a promotion to the SST’s change. It may be related tothe El Ni o-Southern Oscillation(ENSO)-like process. Estimated the SST by differentmethods can know that the planktonic foraminifera transfer function(FP-12E) andmodern analog technique(MAT) is not suitable for the center of WPWP.The variation in upper water structure also imitates the glacial-interglacial cycle.The depth of thermocline (DOT) was deeper during MIS10to MIS8, but abruptlybecame shallower in MIS7/8, then deepened to stable fluctuation after MIS7up to thelast glacial stage. The spectral analyses indicate that the joint effect of high latitudeforcing and tropic driving caused the variation of the upper water character. Of course,ocean circulation has also impact on the variation of the upper water structures.