Ocean Currents
Windblown surface currents help distribute heat around the globe by moving warm water away from the equator and cool water away from the north and south poles.
A change in even one of the Earth’s surface currents can result in huge changes in weather patterns. Most years, winds blow westward across the tropical Pacific Ocean. Every three – seven years, however, these winds do not blow as strongly as usual. Without the winds, the movement of currents in the Pacific is disrupted. These changes in air and water movements cause a global weather event called El Nino, which may last for 12 to 18 months.
During El Nino years, weather patterns change around the planet. Some places get more or less rain or snow than usual. Temperatures may be warmer or cooler in other years.
Surface Currents
Strong winds blowing over the ocean are set in motion by the uneven heating of Earth’s surface. These winds cause surface currents to flow. The currents extend only about 100 to 200 meters down into the ocean, but they cover large areas. Earth’s rotation curls surface currents into giant clockwise whirlpools in the Northern Hemisphere. In the Southern Hemisphere, currents curl counter-clockwise because of Earth’s rotation. The shapes of continents also affect the paths of surface currents. Surface currents carry warm water away from the equator and cool water away from the poles.
Deep Water Currents
In addition to surface currents, there are also currents flowing deep in the ocean. Deep currents are driven by differences in water density. Seawater can become denser because of cooling, an increase in salinity, or both. The densest water is found in the Polar Regions. For example, as sea ice forms near Antarctica, the salinity of the cold water beneath the ice increases. The highly dense water sinks down the continental slope of Antarctica and then moves slowly across the ocean floor. It may take 1000 years for water from this current to resurface near the equator. Another deep current flows out from the Arctic Ocean.
A change in even one of the Earth’s surface currents can result in huge changes in weather patterns. Most years, winds blow westward across the tropical Pacific Ocean. Every three – seven years, however, these winds do not blow as strongly as usual. Without the winds, the movement of currents in the Pacific is disrupted. These changes in air and water movements cause a global weather event called El Nino, which may last for 12 to 18 months.
During El Nino years, weather patterns change around the planet. Some places get more or less rain or snow than usual. Temperatures may be warmer or cooler in other years.
Surface Currents
Strong winds blowing over the ocean are set in motion by the uneven heating of Earth’s surface. These winds cause surface currents to flow. The currents extend only about 100 to 200 meters down into the ocean, but they cover large areas. Earth’s rotation curls surface currents into giant clockwise whirlpools in the Northern Hemisphere. In the Southern Hemisphere, currents curl counter-clockwise because of Earth’s rotation. The shapes of continents also affect the paths of surface currents. Surface currents carry warm water away from the equator and cool water away from the poles.
Deep Water Currents
In addition to surface currents, there are also currents flowing deep in the ocean. Deep currents are driven by differences in water density. Seawater can become denser because of cooling, an increase in salinity, or both. The densest water is found in the Polar Regions. For example, as sea ice forms near Antarctica, the salinity of the cold water beneath the ice increases. The highly dense water sinks down the continental slope of Antarctica and then moves slowly across the ocean floor. It may take 1000 years for water from this current to resurface near the equator. Another deep current flows out from the Arctic Ocean.