Illustration depicting air-sea daily rhythm

At the ocean surface, heat and energy is exchanged between the air above and the water below. Every day, the sun rises and warms a thin layer of surface water. At night, without heat from the sun, the warm surface water cools down, becomes heavier, sinks, and mixes deeper into the ocean creating a blank slate on the ocean surface for the process to start all over again. (Illustration by Eric S. Taylor, © Woods Hole Oceanographic Institution)