THE EVOLUTION OF UPPER WATER IN THE CENTER OF WEST PACIFIC WARM POOL DURING THE LAST 360KYR

Abstract

The Core KX97322-4 was taken from the Ontong Java Plateau,western equatorial Pacific.Quantitative analysis of planktonic foraminifera,combined with oxygen isotope data and spectral analyses of each index,revealed the glacial-interglacial variations of the oxygen isotope of planktonic foraminifera and the vertical structure of the upper water in the center of the West Pacific Warm Pool(WPWP) during the last 360kyr.Our results indicate that,since MIS10,the oxygen isotopes of both the surface dwelling species G.ruber and subsurface dwelling species N.dutertrei's showed obvious glacial-interglacial cycles.The surface and subsurface waters were influenced by the volume change of high latitude ice sheets in a large scale generally,and the subsurface water is even more sensitive.The variation in upper water structure also imitates the glacial-interglacial cycle.The thermocline(DOT) was getting deeper during MIS10 to MIS8,but abruptly became shallower in MIS8-MIS7/8,then deepened again after MIS7/8 and turned to stable fluctuation when entered the last glacial stage.The spectral analyses indicate that the joint effect of high latitude forcing and tropic-driving caused the variation in the upper water characters.Of course,ocean circulation has also impact on the variation in the upper water structures.