2. Currents
• Current – a large stream of moving water
that flows through the ocean. Capable of
moving large amounts of water long
distances.
• Surface Currents
– Affect water to a depth of several hundred
meters and are driven mainly by wind.
– Currents move in circular patterns in each of
the five major ocean basins.
3. Currents
• Factors that affect currents
– Sun’s heat
– Earth’s winds
– Earth’s rotation
• Coriolis effect – the effect of Earth’s rotation on
the direction of winds and currents
– This is why currents in the Northern Hemisphere are
clockwise, and those in the Southern Hemisphere run
counter-clockwise
5. Currents
• The largest and most powerful current in
the North Atlantic Ocean is the Gulf
Stream.
– Caused by strong winds coming from the west
(the same ones that move weather fronts
from west to east)
– More than 30 km wide and 300 m deep
– Carries warm water up the East Coast
Surface Current http://youtu.be/YCorkyBe66o
6. Currents
• Deep Currents – caused by differences in density
•
rather than by surface winds
Density of ocean water depends on two factors
– Temperature (cold water = more dense = sinks to
bottom)
– Salinity (amount of salt, more salt = more dense =
sinks to bottom)
• Warm water surface currents move water from
the equator toward the poles, where the water
gets very cold.
7. Currents
• As ice forms at the poles, the salinity of
the water increases.
• When temperature decreases and salinity
increases, the density of the water
increases.
• This causes the water to sink to the
bottom of the ocean floor.
• Deep currents move much more slowly
than surface currents.
8. Currents
• Upwelling – the upward movement of
colder water from the ocean depths.
• Caused by the winds.
– Wind blows the warm surface water
away, causing cold water to rise up to replace
it.
9. Currents
• Upwelling also brings up
– Tiny ocean organisms
– Minerals
– Other nutrients
• Without this, the surface waters would
have very little nutrients.
• Upwelling zones are typically home to
enormous schools of fish
10. Currents
• One major area of upwelling is in the
Pacific Ocean off of South America.
• Upwelling occurs when strong winds from
the Andes Mountains sweep across the
ocean.
– This creates a fishing area that is important to
millions of people who depend on it for food
and jobs.
12. Quick Check Review
• What are the two types of currents found
in the ocean?
• What is the Coriolis Effect?
• What three things does upwelling bring to
the surface?
