Evolution Of The Yellow Sea Warm Current And The Yellow Sea Cold Water Mass Since 6.0 Ka

6 ka was an important period in the evolutionary history of the Earth’s climate and environment.After the last glacial maximum,the climate warming and the sea level rise,so far,the modern ocean circulation pattern had been formed.The evolution of the ocean current field thereafter was mainly affected by millennium and ocean scale factors.The Yellow Sea Warm Current（YSWC）and the Yellow Sea Cold Water Masses（YSCWM）are the most important ocean dynamic processes in the Yellow Sea,the formation process and mechanism of them had always been an important scientific issue that the oceanography community concerned.Reconstruction of the evolution of paleoenvironment and paleoceanography in the Yellow Sea is vital to the systematic understanding of the formation and evolution mechanism of the YSWC and the YSCWM,meanwhile,it is also of great significance to the formation of the central South Yellow Sea muddy deposit.The research is based on 37 surface samples of the Yellow Sea and the core Z1 in the central South Yellow Sea muddy area for the comprehensive study of the evolutionary history of the marine environment in the South Yellow Sea since the Mid-Holocene.The community structure and species of foraminifera from surface samples were identified and analyzed,and the foraminifera species indicator of YSCWM was confirmed,and the transfer functions of temperature,salt,and dissolved oxygen concentration of bottom water were built.Based on these,a comprehensive analysis of the chronostratigraphic and high-resolution paleoceanography environment indicators of the core Z1 was carried out.The variation of long-chain unsaturated alkenone index(U^K₃₇’)based sea surface temperature（SST）and transfer function of temperature（T_b）,salt（S_b）,and dissolved oxygen concentration（O_b）of core Z1 based on surface samples since 6.1 ka were obtained.And then the grain size was tested and the end-member analysis was performed.At last,the organic carbon（TOC）content,organic nitrogen（TN）content,and stable carbon isotopes(δ¹³Corg)values were determined,and the variations of the organic carbon content of marine and terrestrial sources based on them were calculated.Based on the work above,the evolution of the YSWC and the YSCWM since the Mid-Holocene was reconstructed,and the relationship between them was discussed.The teleconnection of SST of the South Yellow Sea and the climate and ocean of high and low latitudes had been established.Finally,based on the evolution of YSWC and YCWM,the sedimentary process and mechanism in the central South Yellow Sea muddy area were reviewed.The following knowledge was grained:1.Through the Q-factor analysis of benthic foraminifera species in the surface sediment samples,it was determined that A.ketienziensis,H.nipponica,and A.italicum was an indicative combination of the YSCWM.2.The evolution of the YSWC since ⁶.0 ka can be divided into two stages: During ⁶.0-1.8 ka,The YSWC invaded the Yellow Sea and had continued to enhance.The Kuroshio played a more important role than the East Asian Winter Monsoon in the early invasion period during 6.1-³.9 ka.During ¹.8-0.0 ka,the YSWC was relatively stable,but there were some fluctuations under the influence of high-and low-latitude forcing.3.The YSWCM already existed at ⁶.0 ka,and it was weak during ⁶.0-5.7 ka.During ⁵.7-4.1 ka,due to the absence of benthic foraminifera in the core,there was no strong evidence for its evolution.Its significant development began with ⁴.1 ka and reached modern strength at ³.7 ka.The evolution of the YSCWM was closely related to the evolution of the YSWC,due to the different influences of ENSO and the East Asian Monsoon,the subsequent evolution of them was asynchronism.During ³.7-2.0 ka,the YSCWM was affected by both the variation of the YSWC and the thermocline and reached its strongest during ³.2-2.5 ka,and then weakened gradually to its modern intensity.During ².0-0.0 ka,the YSCWM was relatively stable due to the synchronous variation of the YSWC and ENSO.4.The evolution of sea surface temperature in the central South Yellow Sea since 6.1 ka was closely related to the hydrological climate of high latitudes of the northern hemisphere and the tropical seas,mainly commonly driven by the regional climate（East Asian winter monsoon）and the Kuroshio Current.During 6.1-³.9 ka,due to the weakened YSWC,the variation of SST appeared controlled by the variation of the East Asian winter monsoon.During ³.9-0.0 ka,the variation of SST was mainly affected by the enhanced YSWC,which was driven by the East Asian Winter Monsoon and the Kuroshio Current.5.The formation of the modern marine environment in the central South Yellow Sea synchronous with the formation of the modern YSCWM,later than the intrusion of the YSWC,and earlier than the formation of the modern YSWC.Combined with the evolution of the YSWC and the YSCWM,it is verified that the formation of the central South Yellow Sea muddy deposit is mainly controlled by the weak tidal current-low energy characteristic of the modern marine environment.The fronts between the YSWC and the YSCWM play important roles in preventing the terrestrial coarse-grained materials from entering the central South Yellow Sea muddy area.The YSCWM and the YSWC play important roles in the enrichment of fine-grained materials and the transportation of terrestrial fine-grained matters respectively in the formation of the muddy deposit.