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Ocean Currents
What makes that River Flow?
What’s the role of wind?
1st: High heat capacity of water (and ocean currents)
buffer ocean temperatures
2nd: Land temperatures fluctuate more, especially in
higher latitudes
3rd: These differences in surface energy create
prevailing winds.
4th: These prevailing winds drive surface currents.
winds and currents
Which way do currents flow?
Northern Hemisphere: surface currents rotate clockwise
(Coriolis aids in this, wind driven mostly)
Southern Hemisphere: currents rotate counterclockwise
Gyres
1. Circular
current flow
due to coriolis
effect
2. Currents tend
to “hug” the
coasts as they
move CW in
the N. Hemis.
Global Conveyer Belt
•Ocean currents move 40% of “excess heat” from equator to poles
•Driven by circulation of deep ocean waters (cold, salty water)
(density) and surface winds
•Warm currents (east coast) away for equator; cold (west coast)
toward equator
Our Closest Currents
East coast: Influence of Gulf Stream
& N. Atlantic
Notice how the
Arctic Ice is
pushed back by
the warm water.
For the area
located at higher
latitudes, average
temperatures are
significantly
warmer than other
areas at the same
latitude. (England,
Norway, etc)
The Labrador Current (cold):
Bringer of Death!!
Icebergs from Greenland calve off and
enter the N. Atlantic via the Labrador
Current. Ex. Titanic
East Coast Currents
• Cold- Labrador
(Canada)
• Warm- Gulf Stream
(FL to Canada) & N.
Atlantic (Canada to
England)
Surface Currents
West Coast Currents
• Cold
– California Currentsouth along west coast
from OR toward Baja
penisula
– North Pacific Currenttoward Washington
state, British Columbia
(really between cold
and warm)
• Warm
– Alaska-north to Alaska
As bottom currents reach landforms,
upwelling occurs. The cold water
reaches the surface and warms (keeps the
process going).
So how do the following influence ocean
currents?
1) Winds?
Answer: Surface winds tends to push water along in the
same direction as the wind
2) Temperature?
Answer: Colder water will sink and warmer water rises
(Convection).
3) Salinity (density)?
Answer: The more salt dissolved in the water the more dense
the water, thus the greater the salinity, the more likely the water
is going to sink.
So putting the three together
Fresh warm water (such as runoff from rivers) or fresh cool
water (from melting ice) will most often be found near the
surface.
Cold, salty water is very dense and is most likely to be
near the bottom of the ocean.
Together, a circulation is created as cold, salty water (from
polar regions) sinks towards/moves along the bottom of the
ocean and warm, salty (usually less salty than the bottom)
moves along the surface (from the equator).