Paleoceanographic Changes Over the Last 400000 Years In The East China Sea Linkages With East Asian Summer Monsoon And Kuroshio Current Variability

Abstract

Paleoceanography of the East China Sea (ECS) has been subjected to extensive study newlinebecause ECS is greatly influenced by the East Asian Summer Monsoon (EASM), newlineprecipitation discharge, and differential inflow of the warm and saline Kuroshio Current newline(KC). The economic and scientific significance of EASM and KC in East Asia tempts newlinethe study of the long-term variability of surface and bottom water paleoceanographic newlineconditions in the ECS. Any change in surface/bottom water conditions either due to newlinevariations in ocean currents or discharge from terrestrial rivers have pronounced effects newlineon the population abundance of foraminifera; therefore, foraminifera happens to be a newlinevaluable proxy to decipher paleoceanographic changes in the ECS. Analysis of core newlinesediments from Integrated Ocean Drilling Program (IODP) Site U1429 has enabled newlineidentifying 41 planktic foraminifera species belonging to 15 genera and 236 benthic newlineforaminifera species belonging to 96 genera over the last 400 kyr. newlinePaleoceanographic changes over the last 400 kyr are reconstructed using planktic newlineforaminiferal population abundances and Mg/Ca ratio derived Sea Surface Temperature newline(SST) from IODP site U1429 to understand the influence of KC and EASM in the ECS. newlineNine different species/species associations of planktic foraminifera are found to be newlinesignificant at this site. Q-mode factor analysis of these abundant species helped to retain newlinefour factors explaining ~91% of the data variance, suggesting four different conditions newlineprevailing at ECS over the last 400 kyr. The species association of factor 1 reflects cold newlinesurface water conditions in the ECS, factor 2 suggests the influence of the coastal water, newlinefactor 3 can be linked with the upwelling of lower thermocline water, and factor 4 is newlinestrongly associated with the strength of the KC. This study suggests that KC and EASM newlinewere stronger during the interglacial periods.