东海陆坡—冲绳海槽水体剖面地球化学特征与指示意义

Geochemistry of the water profiles at the slope of East China Sea and Okinawa Trough and its implications

通过对东海陆坡—冲绳海槽中北部两个水体剖面的碳、氯、硼同位素和离子浓度的分析,探讨了水体剖面的离子和同位素组成的控制因素、水体来源以及现代水体交换过程。结果表明,水体剖面中表层水、次表层水、中层水体的性质明显不同,ST2水体剖面K^(+)、Ca^(2+)、SO_(4)^(2−)等离子浓度整体随深度增加而升高,δ^(13)C、δ^(11)B、δ^(37)Cl垂向变化波动较大,ST19剖面离子浓度、同位素垂向变化趋势与ST2剖面相反。ST2、ST19水体剖面表层水(0~100 m)和次表层水(100~300 m)主要来源于黑潮表层水(Kuroshio Surface Water,KSW)和黑潮热带水(Kuroshio Tropical Water,KTW),同时受长江冲淡水(Changjiang Diluted Water,CDW)/陆架水影响;中层水体(300~1000 m)组成与北太平洋中层水(North Pacific Intermediate Water,NPIW)和南海中层水(South China Sea Intermediate Water,SCSIW)相似。两水体剖面水体组成存在较为明显的南北差异,可能与所处海区地理位置、CDW/陆架水传输路径、区域性地形导致局部上升流、水体剖面中NPIW与SCSIW占比不同有关。

Two water profiles are selected from the northern part of the Okinawa Trough and the elements,such as carbon,chlorine,and boron isotopes and ion concentrations analyzed for investigation of the control factors of the ion and isotope compositions,water source,and modern water exchange process of the water profiles.It is seen that the properties of surface water,subsurface water,and intermediate water in the water profiles are obviously different.The ion concentrations of K^(+),Ca^(2+),and SO_(4)^(2−)in the ST2 profile increase with water depth,and the vertical changes ofδ^(13)C,δ^(11)B,andδ^(37)Cl fluctuate substantially.The vertical changing pattern of ion concentrations,and isotopes along the profile ST19 is opposite to the profile ST2.The surface water(0~100 m)and subsurface water(100~300 m)of the profiles ST2 and ST19 are mainly coming from KSW(Kuroshio Surface Water)and KTW(Kuroshio Tropical Water),affected by CDW(Changjiang Diluted Water)/shelf water,whereas the composition of the intermediate water(300~1000 m)is similar to that of NPIW(North Pacific Intermediate Water)and SCSIW(South China Sea Intermediate Water).There are obvious north-south differences in water composition between the two profiles,owing to the differences in locality,CDW/shelf water transmission path,local upwelling caused by regional topography and the proportions of NPIW and SCSIW in the water profiles.