How Is Climate Affected by Ocean Currents?

Earth's ocean currents have a major impact on climate.

The earth is warmer at the equator than at the poles. This differential heating of the ocean's surface creates a pressure gradient system that sets the ocean in motion. Major ocean currents move in separate gyres around the world's ocean basins. As they do so, ocean currents impact the daily weather and overall climate of the coastal locations that they directly affect.

How Ocean Currents Function

Two different types of ocean currents are surface currents and deep-water currents. Deep-water currents travel around the globe, but they do so deep under the surface of the ocean. Surface currents travel in circular patterns around earth's ocean basins along the surface of the oceans. As they do so, they bring masses of air with them. These masses of air affect the climates of coastal locations in important ways.

Temperature

The masses of air that travel with ocean currents are often of different temperature than the locations they travel to. Ocean currents can significantly alter the average temperatures of an area. The Gulf Stream, a warm ocean current, brings warm air to most of the eastern coast of the United States, giving these coastal areas a warmer climate than they would otherwise have. In contrast, the state of Maine is affected by the Labrador current. This cold ocean current creates colder average temperatures than Maine would experience based on latitudinal position alone.

Precipitation

Ocean currents also affect the precipitation rates of coastal areas. According to Professor Michael E. Ritter, cold ocean currents prevent clouds from forming and in general decrease the average rates of precipitation of areas that they affect. Conversely, the air masses associated with warm ocean currents create clouds and increase the average amount of precipitation in an area. Ocean currents make coastal locations wetter or drier than they would otherwise be.

Temperature Range

Water heats up and cools down more slowly than land. This means that the temperature range between the daytime highs and nighttime lows is usually narrower for air over water than for air over land. Areas that are far away from the ocean are said to have "continental climates" and have relatively large temperature fluctuations. Coastal locations are said to have "maritime climates" and typically experience narrow temperature ranges.

Climate on a Global Scale

Just as specific warm or cold surface currents affect particular locations, the entire global system of surface and deep water currents affects the general climate of earth. Ocean currents bring warm air from the equator to the North and South poles, making the poles warmer. Ocean currents also bring cold water and air from the poles, making the tropics cooler. Just as maritime climates experience narrower temperature ranges, the entire earth experiences less extreme temperatures because of ocean currents. Without ocean currents, much of the earth would be completely uninhabitable.

References

• University of South Carolina: Ocean Currents and Climate
• National Weather Service: Ocean Currents
• "The Physical Environment: An Introduction to Physical Geography"; Michael E. Ritter; 2006.