南黄海、东海陆架及冲绳海槽北部 沉积物的10 Be和9 Be记录*

文章讨论了南黄海泥质区、东海陆架及冲绳海槽北部表层沉积物和柱状岩芯中¹⁰ Be及⁹ Be含量的水平和垂直分布,并与重金属Pb的分布进行了比较。表层沉积物中的¹⁰ Be,⁹ Be和Pb三者表现出完全不同的分布特征。¹⁰ Be的分布主要受黑潮及其支流黄海暖流所支配; ⁹ Be的分布受黄河陆源物质输入的影响,主要集中在南黄海泥质区; Pb则主要分布在长江口和琉球群岛附近,反映了人类活动的影响。冲绳海槽北部末次冰期和全新世时¹⁰ Be的沉积通量变化在整体上反映了¹⁰ Be大气生产率的变化,即地球磁场屏蔽效应的影响。03孔全新世时¹⁰ Be的沉积通量 (1.12×10⁹atoms/cm²ka)基本上等于¹⁰ Be的现代大气平均生产率,而在末次冰期时平均为4.06×10⁹atoms/cm²ka, 高于¹⁰ Be 的现代大气平均生产率3倍以上。在冲绳海槽由于黑潮的缘故,¹⁰ Be对气候的变化响应要比极地冰芯的¹⁰ Be变化响应灵敏的多,对气候变化信号起了放大的作用。冰期时冲绳海槽北部¹⁰ Be的沉积通量远远高于太平洋大洋海区,充分反映了黑潮的传送带作用和边缘海的聚焦沉积作用,并表明末次冰期时在千年尺度上黑潮仍流经冲绳海槽,且强度并未减弱。 ¹⁰ Be的通量在新仙女木时降到整个岩芯所跨时期的最低点,甚至低于¹⁰ Be的现代大气平均生产率,因此推测在新仙女木事件时,黑潮的变动特别大,有可能改向或断流。

Be ISOTOPES IN SURFACE SEDIMENTS FROM THE SOUTHERN YELLOW SEA, THE EAST CHINA SEA CONTINENTAL SHELF AND IN A SEDIMENT CORE FROM THE NORTHERN OKINAWA TROUGH

Concentrations of beryllium isotopes in surface sediments from the Southern Yellow Sea and the East China Sea continental shelf and a sediment core DGKS9603 from the Okinawa Trough have been determined. ¹⁰ Be records in the Okinawa Trough sediment during the last glacial, the Younger Dryas cold period, and the Holocene show that the main part of the fluctuations in ¹⁰ Be content in the sediment can be attributed to variations in the ¹⁰ Be production rate. The average ¹⁰ Be flux in the Holocene was 1.12×10⁹atoms/cm²ka, nearly the same as the present atmospheric ¹⁰ Be production rate, whereas the average ¹⁰ Be flux during the last glacial period was 4.06×10⁹atoms/cm²ka, more than three times higher than at present and also higher than the ¹⁰ Be accumulation fluxes in the Pacific open ocean during the glacial period, indicating the conveyor rule of the Kuroshio Current and a boundary scavenging effect for ¹⁰ Be. The high ¹⁰ Be content and flux in the Okinawa Trough during the glacial period proved that on millennium scale the Kuroshio Current still flowed in the Okinawa Trough area with significantly high intensity. However, this does not disprove that short changes in intensity or direction of the Kuroshio ever occurred at certain short cooling events. The ¹⁰ Be minimum during the Younger Dryas event may indicate that the Kuroshio had been once greatly weakened or even terminated in the Okinawa Trough area which could be related to the response of the Pacific Ocean to the Younger Dryas. The ¹⁰ Be and ⁹ Be in surface sediment show totally different distribution patterns. The ¹⁰ Be distribution is dominated by the input from Kuroshio and its branch, the Yellow Sea Current, whereas ⁹ Be is mainly influenced by terrestrial input of suspended materials from the Yellow River discharge and deposited in the fine-grain size sediment zone southwest of the island of Jeju. Both ¹⁰ Be and ⁹ Be distribution patterns are different from anthropogenic pollutants such as heavy metal Pb which is dominantly distributed closely to the coastal areas.