Abstract. This paper presents the seawater surface elevation in Gulf of Manado with numerical approach. The RANS shallow water flow equation is used to obtain a numerical equation of seawater surface elevation with a semi-implicit approximation approach in which the pressure distribution in the vertical layer of seawater is assumed hydrostatic. The results found that the high seawater level is not more than 1.81 m upper seawater level and 1.30 m under seawater level respectively. The results can be used as a recommendation to predict the condition of sea waves in the Gulf of Manado.
IntroductionThe horizontal and vertical motion of seawater occurs caused by the wind stress at the sea surface. If surface seawater is a divergence, water at the bottom will rise to surface and this situation will be happened upwelling; conversely, where it is a convergence and will happened downwelling. For condition where a system of cyclonic wind on surface seawaters where the average movement of the wind-driven layer is to the right of the wind which causing divergence of surface water and upwelling, and the sea-surface is lowered and the thermocline is raised, it is called Ekman pumping. In condition inverse correspond in anticyclone wind is convergence and sinking (downwelling), it causes the seasurface to slope upwards the middle of the gyre [1]. It will produce a sea wave called seawater surface elevation. Transport at the position of Gulf of Manado is convergence.A numerical modeling can predict seawater surface elevation. It conducted by [2][3][4][5] in the Straits of Bunaken and Bangka, North Sulawesi, Indonesia. The simulation seawater surface elevation from shallow water flows with a free surface correction method [6]. The distribution of seawater surface elevation with respect to a reference level (m) by study on modeling shallow water wakes using a hybrid turbulence model [7]. Calculating of seawater surface elevation by using the semi-lagrangian method and they compute the non-linear response of the full model due to a shear stress that comes from the action of the wind at the ocean surface [8]. Simulated seawater surface elevation in the variations of typical seasonal corresponding to the period 1956-1960 from the surface wind stress in the Aral Sea [9]. Also, Implemented fully-implicit time integration schemes in a version of parallel ocean program for calculation of seawater surface elevation by its simulation in the North Atlantic [10].The objective of this study was to get distribution of seawater surface elevation by using numerical modeling in the Gulf of Manado, North Sulawesi, Indonesia.