How are the temperatures of tropical seawater and polar seawater different?

Explanation:

o At the polar latitudes the surface temperature remains near the freezing point of sea water about -1.9°C. Pure water freezes at 0°C and boils at 100°C under normal pressure conditions. When salt is added the freezing point is lowered and the boiling point is raised

o The water temperature of tropical oceans thus typically exceeds 20°C and stays relatively constant troughout the year. Particularly intense radiation directly over the equator evaporates seawater and forms a mass of very warm, humid tropical air that subsequently rises and cools as it flows north and south