Ocean Currents
• The Reality of Sending a Message in a Bottle
Why is Ocean Circulation
Important?
• Transport heat
– Equator to poles
• Transport nutrients and
organisms
• Influences weather and
climate
• Influences commerce
Non-rotating Earth
Convection
cell model
Warm water flows from
The tropics THE EQUATOR
Add rotation and add landmasses
unequal heating and cooling of the Earth
Two Types of Currents
Surface Currents
• Wind Driven
Deep Ocean Currents
• Density Driven
Ocean Currents
Surface Currents
Flow across the surface to a depth of a few
hundred meters
Deep Water Currents
Flow near the ocean
floor below the waters
surface
Surface Currents
Main Causes
1. Solar Heating (temp,
density)
2. Winds- main cause of
currents you see on
the surface (Global
winds)
3. Coriolis- rotation
4. Continental Deflection
Wind-driven surface currents
Sailors have know about ocean currents for centuries
Sailors have know that “rivers”
flow in the seas since
ancient times. They used
them to shorten voyages, or
were delayed by trying to
stem them.
If navigators do not correct to
deflection by currents, they
may be far away from where
they think they are and meet
disaster.
What do Nike shoes,
rubber ducks, and
hockey gloves have to
do with currents?
Lost at Sea
2004-2007
Barber’s Point
DEEP CURRENTS
form when…
• Warm and cold surface currents meet and mix
• Result from differences in temperature and
DENSITY
• COLD WATER=DENSE
• HEAVY= pushes down to the bottom
• Not Wind Driven!! Temperature/Density Driven
Surface and Deep-Sea Current
Interactions
Unifying concept: “Global Ocean Conveyor Belt”
http://seis.natsci.csulb.edu/rbehl/ConvBelt.htm
North Pacific Subtropical Gyre
• “Great Pacific Garbage Patch”
• Estimate: 46,000 pieces of floating garbage/mi2.
North Pacific Subtropical Gyre
135° to 155°W and 35° to 42°N
North Pacific Subtropical Gyre
YOUTUBE
Inquiry
1. What is a convection cell?
2. Why don’t currents travel in straight lines?
3. How are surface currents created?
4. What is a gyre?
5. How are deep currents created?