东中国海1976—1996年上层海洋盐度变化趋势及机制初步探讨

A Preliminary Study on the Trends and Mechanism of the Upper Ocean Salinity in the East China Seas During 1976—1996

本文采用客观分析资料Ishii,分析东中国海1976—1996年上层海洋不同深度盐度变化的空间分布结构;并结合OAflux客观分析蒸发资料和GPCP实测降水资料以及大通站长江径流量资料,分析蒸发、降水、淡水通量(蒸发与降水之差)、长江冲淡水等表面强迫对东中国海盐度变化的影响。研究表明:东中国海盐度变化趋势有明显的区域差异性:渤海和北黄海区域表层盐度呈上升趋势,主要受黄河径流量持续减少的影响;长江口附近区域的表层盐度主要受长江径流量变化的影响,夏季盐度升高趋势明显且影响范围至对马海峡附近,冬季趋势不明显;东海黑潮区域(长江口附近区域除外)表层盐度与淡水通量(蒸发与降水之差)变化一致呈上升趋势。另外,除渤海和北黄海以外的沿岸浅水区表层盐度呈降低趋势,主要受陆地降水增加的影响。表层以下盐度的变化与表层不同,上升趋势大致与主要暖流路径一致,可能是水平平流作用占主导地位。

The spatial distribution of salinity trends in different depths of the upper ocean in the East China Sea from 1976 to 1996 is analyzed based on objective analysis data from Ishii.Then the effects of evaporation,precipitation,freshwater flux(difference between evaporation and precipitation)and the Yangtze River diluted water on salinity change are studied by utilizing objective analysis of data OAflux,precipitation data GPCP and Datong station Yangtze River discharge data.The results show that the salinity trends of the East China Sea are obvious regional different:the sea surface salinity(SSS)of the Bohai Sea and the North Yellow Sea is rising,which is mainly affected by the continuous decrease of the Yellow River discharge.The SSS near the Yangtze River Estuary is mainly affected by the discharge of the Yangtze River.The salinity trend in summer is significant and extends to the Tsushima Strait,while the trend in winter is weak.The trends in the East Sea Kuroshio areas(except the Yangtze River Estuary)is rising according with the freshwater flux(the difference between evaporation and precipitation).In addition,the coastal shallow water areas(except the Bohai Sea and the North Yellow Sea)present a decreasing SSS trend,induced by the increase of land precipitation.The salinity trends below the surface are different from the SSS,and the increasing trend is mainly along the warm current in the ECS,suggesting that the horizontal advection may play a dominant role.