热带西太平洋18°20′N断面上部的水团特征及其对埃尔尼诺和反埃尔尼诺的响应

WATER MASS FEATURES OF UPPER PART ALONG 13°E SECTION IN WESTERN TROPICAL PACIFIC AND RESPONESE TO EL-NI■O AND LA-NINA

笔者根据1986～1989年间中-美联合TOGA调查的CTD资料,应用模糊聚类法划分热带西太平洋中近黑潮源地(18°20′N断面)上部水域的水团,并描述它们的分布和主要特征以及其对1986～1989年发生的埃尔尼诺和反埃尔尼诺事件的响应。结果表明,该海域的1 000m以浅分布着三个水团:北太平洋热带表层水(包括黑潮表层水)、北太平洋次表层水(包括黑潮次表层水)和北太平洋中层水(包括黑潮中层水)(分别简称为NPTSW、NPSW和NPIW);它们的交界分别位于100和350m左右。在1986/1987的埃尔尼诺年,海区的温跃层明显上移,暖水量明显减少;NPTSW的垂直厚度大约减少了20m,上均匀层中的盐度略有增加,而温度则没有多大的差别。在1988/1989年发生的反埃尔尼诺事件的后期,温跃层上部的强度变弱,上均匀层则变薄,海区中的暖水量也明显减少;近海表面的盐度异常低,而温度略有降低。由此可见,不管是在1986/1987的埃尔尼诺年还是在1988/1989的反埃尔尼诺年,研究海区的暖水都减弱,也即都反映为“冷水年”。

The data used in this paper was from the Sino -American Joint TOGA Program from 1986 to 1990. The water masses in the upper part of the North Equatorial Current and adjacent area of 130°E section in the western tropical Pacific Ocan were classified by using clustering method. The variation in the features of water masses and responses to the El - Nino and La - Nina Events,which occurred between 1986 to 1989,were described. It was indicated that there were four water masses within 1000 m depth in the studied area:western Pacific tropical surface water,north Pacific subsurface water,north Pacific intermediate water and Antarctic intermediate water. In 1986 - 87 El - Nino years, the thermocline obviously moved up by about 45 meters and the range of Warming Pool(T>28℃)dwindled in the area. In 1988 - 89 La -Nina years,the range of the pool grew much larger and the salinity in the well - mixed surface layer decreased by about 0. 30 and the temperature near sea surface increased by about 0. 24℃.