The sun plays a crucial role in the cycle of energy in an ecosystem by providing energy for winds, ocean currents, and the water cycle. Wind and water currents require energy to power their movements, and the sun provides this energy through solar radiation. Large-scale surface ocean currents are driven by global wind systems that are fueled by energy from the sun. These currents transfer heat from the tropics to other parts of the ocean, affecting climate, local ecosystems, and seafood. Wind-driven and ocean-current circulations move warm water toward the poles and colder water toward the equator, helping to distribute the sun's heat from one part of the planet to another through convection. The transfer of heat energy within the atmosphere, hydrosphere, and the surface and interior occurs as a result of radiation, convection, and conduction.