Ocean Currents

Not only do oceans affect climate, but regions with a maritime or partial maritime climate are influenced by the temperature of the nearby ocean. For example, cool, foggy San Francisco weather is affected by

The concept of latent heat answers important questions about climate. For example, why is March cooler than September in the Northern Hemisphere, even though at any given location the two months have the same day length and the same solar radiation? March is cooler because much of the Sun's incoming energy goes into changing ice to water; that is, into melting snow and ice. (Much of the power of hurricanes comes from latent heat as water vapor transforms into rain.)

Besides latent heat, there is another important heat type. Imagine walking barefoot on a sunny, sandy beach. The sand is hot, but the water is pleasantly cool, although each material is receiving the same amount of solar radiation. There are three reasons for this:

© (1) Water has a much higher specific heat than sand. Specific heat is the amount of energy needed to raise the temperature of one gram of material by 1.8°F (i°C). If water and sand absorb equal amounts of solar radiation, the sand becomes hotter than the water.

© Heat disperses more effectively through water because the Sun's rays can penetrate deeper into it. Also, liquid is able to disperse heat by convection while sand is not.

© Water loses heat by evaporative cooling, the cooling that takes place as water changes state from a liquid to a gas, due to the latent heat of vaporization.

the cold California Current that flows from the northern Pacific Ocean. But the warm Gulf Stream that runs from the equator up the Atlantic coast of the southeastern United States brings warm, humid weather to Virginia Beach in the summer. So the temperature of nearby ocean currents, which is controlled by where the water is coming from, influence the climate of adjacent lands.

A map of the east-west portions of the surface ocean currents looks a lot like the map of atmospheric circulation. This is because surface currents are driven primarily by the wind, although, of course, the water, being heavier, does not move nearly as fast. For example, the westerlies drag North Pacific water from west to east, while the trade winds north and south of the equator drag surface currents from east to west.

If the Earth were covered entirely by water, surface currents would move in giant belts around the globe. But over most of the planet, the currents run into continents, where they are influenced by the Coriolis effect. As with atmospheric currents, surface currents turn to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. The currents continue to travel along the continent until they run into an east-west flowing current going in the opposite direction. The result is that surface currents travel in loops called gyres, which rotate clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.

Wind Driven Surface Currents Gyres

The major surface ocean currents. The five gyres are the North and South Pacific, the North and South Atlantic, and the Indian.

As discussed in the San Francisco and Virginia Beach examples, ocean currents alter the temperature of the air above them. The North Equatorial Current, which is warmed by the Sun as it travels from east to west in the Atlantic Ocean from the equator, turns north when it hits the Americas to become the Gulf Stream. This large, swift warm-water current raises air temperatures as it moves northward along the eastern United States and southeastern Canada. The current then swings away from North America and heads east toward Europe as the North Atlantic Drift. Once it arrives, it divides into two currents. One moves south along Europe and flows back toward the equator. The other travels north along Britain and Norway, bringing relatively warm water to the northern latitudes. This process has an enormous effect on the climate of northern Europe. Although London is at 51°N latitude, several degrees north of Quebec, the climate there is much more temperate, with rain instead of snow as the dominant winter precipitation.

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Responses

  • Deborah
    What ocean current is virginia beach located on?
    8 years ago
  • Virpi
    Where is Wind Wind drift cold ocean current in a map?
    8 years ago
  • erik
    What are the five major gyres?
    8 years ago
  • gianna romani
    What are the five major currrent gyres?
    7 years ago
  • JULIANE
    What atmospheric circulation is responsible for the north pacific gyre?
    7 years ago
  • mentha
    What are the northern hemisphere gyres?
    5 years ago
  • mitchel
    Do the pacific ocean currents run clockwise or counterclockwise?
    4 years ago
  • phoebe king
    What is loops and gyres in Ocean Current?
    3 years ago
  • MICHELANGELO
    How does ocean currents affect air quality?
    2 years ago
  • alan
    How do ocean currents affect the tropical rainforest?
    1 year ago
  • arthur
    How do ocean currents affect tropical rainforests?
    10 months ago
  • birgit brandt
    How does air poluution relate to ocean currents?
    9 months ago
  • klaus
    How has south asia’s ocean currents affected by pollution?
    5 months ago
  • selma
    How wind currents affect pollution?
    5 months ago

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