Download Currents and Climates

Currents and
Climates
Notes
Surface Currents
• Surface currents, which affect water to a depth of
several hundred meters, are driven mainly by
winds.
• A current is a large stream of moving water that
flows through the oceans. Unlike waves, currents
carry water from place to place.
• Surface currents move in circular patterns in the
oceans. Most currents flow east or west, and then
turn back to complete the circle.
Surface Currents
• Earth rotates on its axis. The effect that Earth’s
rotation has on the direction of winds and currents
is called the Coriolis Effect. The Coriolis effect
causes ocean currents and winds to move in
circular patterns.
• In the Northern Hemisphere, the Coriolis effect
causes the currents to turn to the right. In the
Southern Hemisphere, the Coriolis effect causes
currents to shift to the left.
http://daphne.palomar.edu/pdeen/Animations/34_
Coriolis.swf
Surface Currents
• Currents affect climate by moving cold and warm
water around the world. Some currents carry
warm water from the equator to the poles (Gulf
Stream). Other currents carry cold water from the
poles to the equator (California Current). Warm
water warms the air above it. Cold water cools
the air above it.
• Remember that warm air holds more moisture, so
warm surface currents usually bring more rain
than cold surface currents.
Surface Currents
• Sometimes, changes in wind patterns and
currents occur. Such changes can have big
effects on oceans and the land nearby.
• One example of a change in wind patterns and
currents is El Niño. El Niño is an uncommon
climate event that happens every two to seven
years in the Pacific Ocean. During an El Niño,
warm water moves toward the South American
coast (it usually moves AWAY).
Surface Currents
• La Niña, on the other hand, is a period of
colder than normal surface waters in the
Pacific Ocean. La Niña is the opposite of El
Niño. La Niña brings cold winters and
greater precipitation to the Pacific Northwest
of the United States.
• This reversal of surface currents has planetwide impacts on weather conditions.
Deep
Currents
• Deep currents are caused by differences in
density of ocean water. Deep currents move and
mix water around the world. They carry cold water
from the poles toward the equator.
• The density of water depends on the water’s
temperature and salinity. When warm water flows
toward the poles, the water gets cooler. Some of
the water freezes and becomes ice. When water
freezes, it leaves its salts behind. That causes the
salinity of the remaining water to increase.
• As the water gets colder, and its salinity
increases, the water becomes denser. The denser
water will sink.
Deep Currents
• Deep currents, due to their high density,
travel very slowly.
• The Arctic Bottom Water is so cold and
dense that it can take 750 years to
travel from the Arctic Ocean to the
equator.
• http://oceanexplorer.noaa.gov/edu/learn
ing/player/lesson08.html