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Currents and Climate
Currents
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A current is a large stream of
moving water that flows
through the oceans.
Currents carry water great
distances and some currents
move water at the surface of
the ocean, while others move
the deep water.
Currents move the Sun’s energy
from the equator to the poles.
They also move cold water
from the poles towards the
equator.
This moderates the climate of
our planet.
One Way to Explore
Currents
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Norwegian explorer
Thor Heyerdahl
proved his theory that
ocean currents
influenced human
migration by using a
raft that was powered
only by wind and
ocean currents.
He showed that
Polynesia could have
been settled from
people migrating from
South America.
Surface Currents
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The wind mainly drives
surface currents, which
affects water to the
depth of several
hundred meters.
If Earth were not
rotating, winds and
currents would only
flow in straight lines to
the north and south
poles.
This Coriolis effect
causes the winds to
curve.
Coriolis Effect
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The Earth’s
rotation causes the
winds and currents
to curve in relation
to Earth’s surface.
In the northern
hemisphere the
Coriolis effect
causes the
currents to curve
to the left.
The Gulf Stream
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The largest and most
powerful surface current
is the Gulf Stream in the
North Atlantic Ocean.
It is caused by strong
winds from the west.
The Gulf Stream carries
warm water from the Gulf
of Mexico to the
Caribbean Sea, then
northward along the coast
of the United States.
This current keeps
Northern Europe much
warmer in the winter than
it would otherwise be.
Ocean Current Map
How Surface Currents Affect
Climate
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Climate is a pattern of
temperature and
precipitation, typical
for an area over a
long period of time.
Currents affect the
climate by moving
cold and warm water
around the globe.
A surface current
warms or cools the air
above it, affecting the
climate of the land
near the coast.
Deep Currents
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Streamlike movements
of ocean water located
far below the surface
are called deep
currents. Deep
currents are not
controlled by wind.
Deep currents form in
parts of the ocean
where water density
increases. The density
of the ocean is affected
by temperature and
salinity.
Deep currents are
caused by changes in
density.
Deep Currents, continued
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Formation and Movement of Deep
Currents Differences in water density
cause variations in the movement of deep
currents.
Surface Currents and Climate
• Warm-Water Currents and Climate
Warm-water currents create warmer climates
in coastal areas that would otherwise be much
cooler.
Surface Currents and Climate,
continued
• Cold-Water Currents and Climate
Cold-water currents keep climates along a
coast cooler than the inland climate yearround.
Surface Currents and Climate,
continued
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Upwelling is the
movement of deep, cold,
and nutrient-rich water
to the surface of the
ocean.
The nutrients that are
brought to the surface
support the growth of
plankton. Plankton
support larger
organisms, such as fish
and seabirds.
Upwelling is shown on
the next slide.
El Nino
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El Nino~an abnormal
climate event that
occurs every two to
seven years in the
Pacific Ocean.
It begins when an
unusual pattern of
winds form over the
western Pacific.
Produces a change in the
water temperature in
the Pacific Ocean that
produces a warm
current.
It can last one to two
years.
Effects of El Nino
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El Niño alters
weather patterns
enough to cause
disasters,
including flash
floods, mudslides,
and droughts. El
Niño also prevents
upwelling off the
coast of South
America.
El Nino Impact (Western Coast of
South America)
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Disastrous consequences.
Warm surface water
prevents upwelling off of
the western coast of
South America.
Without nutrients brought
up by upwelling, fish die
or go somewhere else to
find food.
Sea birds have no fish to
eat, and also must leave
the area or die.
El Nino Impact (On Land)
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Causes shifts in weather patterns around the world, bringing
severe conditions to different areas.
Unusually warm winter in northeastern U.S.
Heavy rains, flooding, and mud slides in California.
Deadly tornadoes in Florida.
Studying & Predicting El Nino
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Learning as much as
possible about El Niño is
important because of its
effects on organisms and
land.
To study El Niño,
scientist use a network of
buoys located along the
equator. The buoys
collect data about
surface temperature, air
temperature, currents,
and wind.
Forecasting El Nino
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Scientist don’t fully
understand the
conditions that create
El Nino
They can predict its
occurrence by using
computer models of
the world climate
Knowing when El Nino
will strike, officials will
give notice and can
plan for unusual
weather patterns.
El Nino (2006 hurricane season)
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Why hasn’t there been many
hurricanes in the 2006
hurricane season?
The seasonal activity was lower
than expected because of the
rapid development of El Nino.
This year there were only 9
named storms, 5 became
hurricanes, and 2 became
major hurricanes in Category 3
or higher.
2005 was the most active
season on record, with 28
named storms, of which 15
became hurricanes.
Five of the seven major storms
hit the US, including Katrina.