The Evolution Of The Yellow Sea Warm Current Under The Background Of East Asian Monsoon Since Mid Holoence

The South Yellow Sea(YS) is an important marginal sea in the northwestern Pacific. Its environment and ecology have changed significantly during the Holocene. The changes in this area are influenced by the interactions of the Yellow Sea Warm Current(YSWC) and the East Asian Monsoon(EAM), which develops a typical circulation system at the center and forms a unique sediment body of fine particles, thereby concealing rich information on Paleoclimate and palaeoceanographic change, high-resolution records of the central mud in SYS are necessary. In this study, high-resolution multi-proxies records from a South Yellow Sea gravity core Z1 were achieved by analysis of AMS14 C dating, grain size, Uk’37-sea surface temperature(SST), TOC/TN and δ13Corg. Our results revealed the evolution history of the paleoenvironment in the South Yellow Sea muddy deposit as well as the variation of the Yellow Sea Warm Current since the mid Holocene.EAWM broadly follows the orbital-derived insolation with a similar long-term step-decreased trend as the EASM since 6094 a B.P., which together results a decreased mass supply and material transportation into the SYS mud deposit. There were two high-sedimentation rate events: the intensified EAWM leads the increasing of terrigenous materials supply during 6.1~5.7 ka B.P. and 2.6~2.3 ka B.P., which was related to the strengthen of YSWC, the stabilizing of cyclone cold water mass of Yellow Sea might increase the deposition process.The variation of grain size in core Z1 was closely related to resuspension and coastal currents due to the East Asian Winter Monsoon(EAWM) activity. Combined with grain size parameters, the organic geochemistry proxies TOC, TN, C/N ratio and δ13Corg value could be used to indicate the input of terrigenous materials and/or the intensity of ocean primary productivity. Our result revealed the continuous history of EAWM over the past 6094 years could generally be divided into four periods: strong and stable during 6.1~5.4 ka B.P.; strong and highly fluctuation during 5.4~3.9 ka B.P.; weak and stable during 3.9~2.0 ka B.P.; and the transfer period during 2.0~0 ka B.P., when the intense of EAWM is increased and a little more fluctuation than during 3.9~2.0 ka B.P.. Correlation between regional records and global climate variations reveals that, the grain size was coarser at about 6.0 ka B.P., 5.3 ka B.P., 4.7 ka B.P., 3.9 ka B.P. and 3.4 ka B.P. corresponded well in time to strengthened EAWM.The SST records could generally be divided into three stages: A low and highly fluctuation SST phase at 6.1~3.9 ka B.P.; A increasing and intensely fluctuating SST phase at 3.9~2.0 ka B.P.; and A high and lighter fluctuation SST phase since 2.0 ka B.P.. Variation of SST record corresponds well in time to nine global cold climate events. The former five cold events were the same with the strengthened EAWM events. The others occurred at 3100~2550 a B.P., 2450~2100 a B.P., 1500~750 a B.P. and 750~250 a B.P.. However, the amplitude of the SST response to cooling events was significantly different in different phases. The SST response to global cooling event was strong during 6.1~3.9 ka B.P. and the SST response was weak during 2.0~0 ka B.P.. The SST response to global cooling event was strongest during 3100~2550 a B.P., cause of little stronger EAWM and weak YSWC during the time. The difference in amplitude of the SST response is possibly caused by the modulation effect of the Yellow Sea Warm Current which acts as a compensating current induced by the East Asia winter monsoon. The warm waters brought by the Yellow Sea Warm Current cushion the SST decrease induced by climate cooling, and both the EAWM and YSWC play important roles in the variation of SST.Periodicity analysis shows the SYS give a good record of global high-frequency cycles including the millennial and centennial scale cycle reveals quite sensitive corresponds to the global and regional high-frequency climate events. Periods of record picked up from different proxies show similar periods, which reveal these paleo-environmental proxies have the same controlling factors. Centennial periodicities show that the solar activity has basic influences on SYS while the millennial periodicities show that the thermohaline circulation in the high latitude controls the paleoclimate change of the EAM.