What is the significance of heating and cooling of surface waters for the nature of the Earth?

Water temperature is one of the most important properties of the World Ocean. The water heats up slowly, but also cools slowly. Therefore, a huge amount of heat accumulates in the surface layer of ocean waters in summer. In winter, the waters are cooled and give off heat to the air. Thus, the World Ocean regulates the temperature on the earth’s surface. However, the thickness of the heated layer of water is no more than 200 m. Deeper, the temperature rapidly decreases and remains always constant -2-3 ° C.
The temperature of surface waters depends on the amount of incoming solar heat, so it decreases from the equator to the poles. The water temperature also changes according to the seasons of the year. In the Northern Hemisphere, it is greatest in August, and the smallest in February, in the Southern Hemisphere, on the contrary.