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利用中国科学院南海海洋研究所历史温盐剖面观测资料和WOD09(World Ocean Database2009)中的CTD、OSD、PFL温盐剖面资料,分析了1965-2012年间南海18°N跨海盆断面中层水的变化特征。研究结果表明:中层水平均盐度呈现显著的年代际变化,20世纪60年代中期至70年代末,中层水平均盐度约为34.432,80年代盐度增加至34.440,90年代之后至今盐度明显降低;在年代际尺度变异调制下,不同年代中层水盐度变化有不同的变化趋势,1967-1977年呈现显著的下降趋势,1990-1997年中层水盐度从34.450迅速降为34.414,而在1997年之后表现出明显上升趋势,与此同时,中层水温度有着相似的变化特征,与90年代之前相比,21世纪以来温度与盐度同步下降,并且变化幅度变小。与大洋的中层水团年代际变异相比,南海18°N断面中层水呈现出与大洋不同的特征。另外,中层水盐度有着十分显著的年际变化,其振幅远大于年代际尺度变异,并且与ENSO密切相关,在厄尔尼诺年达到极小值。
Based on the historical data of the temperature and salinity profiles of the South China Sea Institute of Oceanology and the data of the CTD, OSD and PFL temperature and salinity profiles in WOD09 (World Ocean Database 2009), the changes of the water in the 18 ° N cross-ocean basin section of the South China Sea from 1965 to 2012 were analyzed feature. The results showed that the salinity of the middle level showed significant interdecadal variation. From the mid-1960s to the late 1970s, the salinity of the middle level was about 34.442 and the salinity increased to 34.440 in the 1980s, The change of middle-level water salinity has a different trend in different years, showing a significant downward trend from 1967 to 1977, and from 1990 to 1997, the salinity of middle-level water rapidly dropped from 34.450 to 34.414. After 1997, there was a clear upward trend. At the same time, the water temperature of middle layer has a similar variation. Compared with that before the 1990s, the temperature and salinity have been decreasing in a synchronous manner since the 21st century, and the change range has been smaller. Compared with the interdecadal variation of the middle water layer in the ocean, the 18 ° N section of the South China Sea has different characteristics from the ocean in the middle layer. In addition, the mid-level water salinity has a very significant interannual variation with an amplitude far greater than the decadal-scale variation and is closely related to ENSO and reaches a minimum in El Niño.