21.1 Ocean Currents
Ocean Currents
Section 21.1
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The Restless Ocean
water is constantly in motion
winds generate surface currents
moon and sun produce tides
density differences create deep-ocean circulation
Click for NOAA current animation
Surface Currents
· controlled by 3 factors: air currents (wind), Earth's
rotation, location of continents
· winds are the primary driving force of surface
currents
created by the uneven heating of the atmosphere
colder, denser air sinks and creates high pressure
areas
air moves away from high-pressure areas creating
winds
· wind passes its energy to the ocean and the
surface waters begin to move
· when winds change direction so do surface
currents
Trade Winds & Westerlies
· trade winds - push currents to the west
· westerlies - push currents to the east
1 Surface currents are generated by all of
the following EXCEPT
A
continents
B
Earth's rotations
C
density differences
D
wind
Coriolis Effect
· curving of the oceans and winds due to Earth's
rotation
· N. Hemisphere - water flows to the right (clockwise)
· S. Hemisphere - water flows to the left
(counterclockwise)
Click for Coriolis animation
21.1 Ocean Currents
Major Surface Currents
2 The trade winds and the westerlies help
move ocean water counterclockwise
(left) in the Northern hemisphere and
clockwise (right) in the Southern
hemisphere.
True
False
· North and South Equatorial Current form the
"backbone" of ocean currents
Importance of Ocean Currents
· navigating ships - GO WITH THE FLOW!
· heat balance
heat is transferred from the tropics to polar regions
· global climate
colder currents from the poles moderate tropical
heat close to the equator
Deep Currents
· aka global conveyor belt
· governed by gravity and driven by density
differences
· water at the surface is made colder (heat loss) and
saltier (evaporation of water) as it circulates
(thermohaline circulation)
causes the water to become more dense
· dense water sinks and less dense water rises
· dense water is created in Arctic and Antarctic
waters
Thermohaline Circulation
3
Thermohaline circulation helps regulate
global temperature, while surface
currents help ships navigate ocean
water.
True
False