1.5Ma以来南海南北上部水体温度变化对比

COMPARISON OF VARIATIONS IN UPPER WATER TEMPERATURES BETWEEN THE NORTHERN AND SOUTHERN SOUTH CHINA SEA SINCE 1.5 MaBP

浮游有孔虫表层海水古温度转换函数、表层暖水种属种含量比值,以及次表层暖水种含量的变化,表明南海北部1 5Ma以来表层、次表层海水温度逐渐降低,其主要变化阶段为0 86～0 94Ma和0 64～0 68Ma。与南海南部西太平洋暖池区的17957站研究结果对比,发现南海南部1 5Ma以来表层、次表层海水温度逐渐增加,发生的主要时间为1 23～1 3Ma和0 64～0 68Ma。南海北部的上部海水结构变化主要受东亚冬季风影响,而南海南部则主要受西太平洋暖池影响,因此,南海南、北上部海水温度的变化说明0 9Ma后尤其是0 68Ma以来东亚冬季风强化,西太平洋暖池加强。

Planktonic foraminifer records from 228 samples from ODP Site 1146, located at the northern continental slope of the South China Sea, were used to study the variations in upper water temperatures, including sea surface temperature (SST) and subsurface temperature (SSBT). The planktonic foraminiferal transfer function (FP-12E) and sum of abundance of G. menarddi and P. obliquiloculata were regarded as proxies of sea surface and subsurface temperature, respectively. Results showed that SST and SSBT decreased gradually since 1.5 MaBP, and its distinct changes took place during 0.86~0.94 Ma and 0.64~0.68 Ma at ODP Site 1146. Different from the results of Site 1146, Core 17957 colleted by Sonne 95 cruise at the southern South China Sea in 1994,found SST and SSBT increase gradually since 1.5 Ma, and its significant changes took place during 1.23~1.3 Ma and 0.64~0.68 Ma. Locations of Cores 1146 and 17957 were mainly controlled by East Asian winter monsoon and West Pacific Warm Pool, respectively. Therefore, variations of upper water temperatures in the two cores indicated that East Asian winter monsoon and West Pacific Warm Pool were strengthened since 1.5 Ma, especially after 0.68 Ma.