Detachment of Low‐Salinity Water From the Yellow River Plume in Summer

Abstract

AbstractHistorical hydrographic data reveal that low‐salinity water can detach from the Yellow River plume in summer. In this study, the mechanism of this detachment is examined using a three‐dimensional numerical model that reproduced the observed detachment, including the position and size of the detached low‐salinity water patch. Sensitivity experiments showed that tide‐induced residual currents and tidal mixing around the Yellow River mouth played key roles in the detachment during spring tide. During the transition from neap tide to spring tide, the intensification of the northward tide‐induced residual current and the weakening of the southward density‐driven current lead to a net northward residual current (0.03 m/s), transporting high‐salinity water to the southern area of low‐salinity water. Meanwhile, the gradually strengthened tidal mixing also increased surface salinity, which was apparent in the central area of low‐salinity water. With the combination of these two effects, the low‐salinity water was separated into two parts during spring tide; that is, detachment of low‐salinity water occurred. The above scenario works with a condition of no wind. With the prevailing southeasterly winds during summer, the northeastward wind‐induced surface current promoted detachment by moving the detached low‐salinity water northeastward and enlarging its size. In contrast, the northerly wind that prevails in the other seasons drove low‐salinity water southward, which then flowed along the coast and hindered detachment. Consequently, the detachment of low‐salinity water from the Yellow River plume occurs only in summer.