加里曼丹岛西北侧低盐水季节变化及机理分析

Analysis of the seasonal variations and their mechanism of the low-salinity water to the northwest side of Kalimantan Island

利用LEVITUS温盐资料、HOAPS降水及蒸发资料以及OFES模式资料等分析加里曼丹岛西北侧表层低盐水的季节变化规律,并使用盐度平衡模式诊断了海面淡水通量、径流、卷挟作用以及平流作用对低盐水变化的贡献。分析表明:加里曼丹西北侧全年均存在1个低盐水团,其季节变化具有"双峰"特征,3月至4月以及10月至11月会发生2次低盐过程,低盐水的中心位置与加里曼丹岛西北侧拉让河河口位置吻合;3月至4月的低盐水形成主要受平流作用控制,而10月至11月的低盐水主要受淡水通量增大的影响。进一步分析表明,风场可以通过改变流场,进而对盐度变化产生重要的影响,是该区域盐度季节变化的主要驱动力之一。

Using LEVITUS temperature and salinity data, HOAPS precipitation and evaporation data and OFES model data, the seasonal variation characteristics of the low-salinity water to the northwest side of Kalimantan Island are analyzed, and the change mechanism is discussed. A salinity balance model is used for diagnosing the contribution of sea surface freshwater flux, runoff, and entrainment and advection actions to the variations. The results show that there is a low-salinity water mass all the year round and its seasonal variation has ＂double apices＂ feature. The minimum values appear from March to April and from October to November, and the center of the low-salinity water is located near the Rajang river estuary at the northwest of the island. However, the sea surface freshwater flux does not show ＂double apices＂ pattern, which indicates that the seasonal changes of the low-salinity water are not controlled by the sea water flux solely. Meanwhile, after adding the runoff of land, it is found that the runoff would increase obviously in winter, this fits the forming conditions of the winter low-salinity water, but this does not happen from March to April, which provides evidence to the statement that the low-salinity water is not controlled by the fresh water flux, but by advection in this period. The increase of freshwater flux is the main effect for the formation of the low-salinity water from October to December. Analysis also shows that the wind field can change the flow field and further result in great impacts on the variation of salinity, which is the main driving force for the seasonal variation of salinity in this area.