九龙江口-厦门港河口盐度锋面的特征

Characteristics of salinity front in Jiulongjiang Estuary-Xiamen Harbour

本文着重研究九龙江口 厦门港冬季小潮实测的各潮时盐度锋面 ,发现其具有锋面宽度窄、盐度梯度很大 ,平面上等盐线大致成西北 东南走向、横断面上则较多呈向南向下倾斜的特征 ,其锋面盐度在 1 5～ 2 7之间 ,锋面宽度约在 2 .6～4.3km之间 ,盐度梯度在 2 .1～ 2 .6km-1之间 ;但盐度锋面区的位置、宽度和盐度梯度随潮位、水深的变化而变化。落急时各层盐度锋面都在象鼻嘴与屿仔尾连线以西 ,并随水深的增加不断向西推移 ,退潮时九龙江冲淡水与西港海水的交汇处存在“退潮流锋面” ,其上辐聚作用强烈 ,使海表漂浮物聚集在等盐线约为 2 5 .5之处形成“流隔线”现象 ;在两个横断面上 ,盐度由南向北、由上至下逐渐升高 ,锋面由断面的中部表层向南部底层倾斜 ,表明低盐的九龙江冲淡水主要沿南岸上层向外港运移。在涨急时 ,除表层盐度分布较为特殊外 ,中、底层的盐度分布与落急时相应层次的相似 ,表明本河口区普通存在“盐楔”现象。

This article studies the characteristics of salinity front in different tide periods at Jiulongjiang Estuary Xiamen Harbour. It shows narrow front ,large salinity gradient ,the run of salinity contour on horizon is northwest to southeast, while it tends to slope southwards and downwards on cross section ,the front salinity is between 15～27 and its width is about 2.6～4.3 km ,the salinity gradient ranges 2.1～2.6 km -1 ,the location ,width and salinity gradient of front area vary with the change of tidal level and water depth. During ebb fast tide ,the layers of salinity fronts are located to the west of join line between Xiangbi and Yuziwei and keep on moving westwards with water deepening. There exists a 'ebbing current front'at the convergence of diluted water from Jiulongjiang and seawater in west harbor when ebbing This front has strong radiation and gathering ,which assembles the surface floating materials at around 25.5 of salinity contour and thus forms the 'current partition line' phenomenon. On the two cross sections ,the salinity increases from southwards to north and upwards surface to bottom while the front slants from the mid section surface to south bottom ,which indicates that the diluted water of low salinity from Jiulongjiang River mainly drifts from the upper layer along the southern coast to Xiamen Harbour. During flood fast tide ,the salinity distribution on the surface is comparatively special while in the mid layer and bottom ,its quite similar to those in the same two layers during ebb fast tide. This indicates there's a common salt water wedge phenomenon in this estuary