中文摘要：

基于东海PN断面近50年的历史水文数据，本文中作者应用一种斜压流函数空间投影的方法分析冲绳海槽北部黑潮水团的季节性和年代际变异。诊断生成的地转经验模态（GEM）显示黑潮中层水的盐度在夏季相对较低，春季达到最高。通过比较1987年之后CTD数据生成的GEM场与1987年之前Bottle数据生成的GEM场，得以证实黑潮的年代际变化特征，即黑潮表层水近20年来温度升高而盐度减小，同时发现黑潮热带水具有盐度增加而中层水具有盐度减小的趋势。

英文摘要：

Based on the historical hydrographic data at the PN line in the East China Sea, we applied a baroclinic streamfunction projection method to analyze the seasonal and interdecadal variations of Kuroshio water mass in the northern part of Okinawa Trough. The seasonal GEM fields show that the Kuroshio Intermediate Water reaches salinity minimum in summer and maximum in spring. By comparing the GEM fields based on the CTD data and the bottle data, we confirm the Kuroshio interdecadal variability, that is, the Kuroshio Surface Water and Intermediate Water warm and freshen after 1987 while the Kuroshio Tropical Water becomes more saline.