The monsoon and El Niño events during the last glaciation as recorded in core MD98-2182 from the western equatorial Pacific Ocean

Abstract

Based on an analysis of δ18O and δ13C, the planktonic foraminiferal assemblage, and sedimentary grain size, and the study of multiproxy data such as paleothermocline depth, paleoproductivity, and paleosalinity during the last glaciation in core MD98-2182 from the central equatorial western Pacific warm pool, together with the data from other sites in this region, we found that sedimentary rates, terrestrial sediment grain size distribution, and paleoproductivity were markedly influenced by glacial-interglacial sea level changes in the study area. In late Marine Isotope Stage 3 (MIS3), which was affected by glaciation and southeast summer monsoon action restricted by precession-modulated insolation, sedimentary rates and the coarse grain content of the terrestrial sediment in the study area were the highest in the past ∼38 ka BP, and paleoproductivity was higher during late MIS3 than the Last Glacial Maximum. A La Nina state dominated in the two intervals of late MIS3 and the early Holocene, and the thermocline deepened. Correlated with the strong East Asian winter monsoon in the glacial period, an El Nino state dominated during MIS2, the thermocline shoaled, and the sea surface salinity (SSS) trended lower from the west to the east owing to the precipitation zone as the locus of atmospheric convection shifted eastward.