Why does the sea water flow?

The prevailing wind blows the sea surface, pushing the seawater to drift with the wind, and making the upper seawater drive the lower seawater to flow, forming a large-scale ocean current, which is called wind ocean current. From the origin, most of the ocean systems on the surface of the world's oceans belong to airflow. Ocean current flows to density current, which is caused by density difference. The difference of seawater temperature and salinity in different sea areas will lead to the difference of seawater density and thus the difference of seawater level. The inclination of the sea surface between two sea areas with different seawater densities will cause the flow of seawater, and the ocean current thus formed is called density current. The compensation current is caused by seawater extrusion or dispersion. When the seawater in a certain sea area decreases, the seawater in the adjacent sea area will be replenished, and the ocean current thus formed is called compensation current. The compensation current can flow horizontally or vertically, and the vertical compensation current can be divided into upward flow and downward flow. For example, the Peru cold current belongs to the rising compensation current.