Variation in temperature

The temperature of the ocean, especially the surface, varies from place to place and from season to season. Ocean temperature depends on the amount of solar energy absorbed. Tropical oceans receive a lot of direct overhead sunlight for much of the year, so the water is warm.

Summer is the only time polar regions receive sunlight, and even then, it is never directly overhead, so water in these places tends to be cold. The amount of sunlight that hits the temperate regions (between the tropics and the poles) varies between summer and winter. The variation in solar energy absorbed means that the ocean surface can vary in temperature from a warm 30°C in the tropics to a very cold -2°C near the poles.