Ocean currents affect climate in several different ways: they regulate temperature, help to stabilize atmospheric conditions in land regions and bring nutrients to marine environments. Ocean currents form in large and small oceans and seas around the world. They range in size from small currents to large currents spanning vast distances, and run in horizontal and vertical directions.
The size, depth and location plays a key role in determining the effect of currents. Shorter horizontal currents, or riptides, exchange cooler, deeper ocean water with warmer water on the surface. This exchange modifies the ocean water temperature. It also influences surrounding air temperature through the processes of downwelling and upwelling. Downwelling occurs when currents bring large volumes of cold water to the surface. This water combines with strong northern and western winds, cooling the air. Similarly, currents bringing primarily warm water to the surface, called upwelling, elevate surrounding air temperatures.
Shorter surface currents primarily affect local atmospheric conditions and influence short-term weather patterns. Fluctuating temperatures control the amount of water in the atmosphere, which in turn creates dry conditions or storms.
Larger ocean currents bring warmer water towards the poles and colder waters towards the equator, modifying temperatures across the planet. They move heat energy across the world's oceans, influencing seasonal temperatures.
The movement and exchange of water in all currents influences ocean and air temperature and cycles nutrients through the ocean system.