Download How do ocean currents affect climate?

How do ocean
currents affect
climate?
• Water holds heat
very well, so ocean
currents easily
transfer heat across
the Earth
How do ocean
currents affect
climate?
• When currents from the
equator (low latitude)
move towards the poles
(high latitude), heat is
transferred from
warmer to cooler areas
• As cold water currents
travel toward the
equator, they help
regulate the warm
temperatures of nearby
land areas.
Every three to seven years, El Niño occurs in the Pacific Ocean. El Niño means "the
(Christ) Child" because it commonly appears at Christmas time. El Niño begins when
water warms up by more than 1°F along the equator in the eastern Pacific and off
the coast of Peru. Nutrients normally found in the cold waters of the area disappear.
Underwater plants called Phytoplankton which use these nutrients, just like plants
on land use fertilizer, grow slowly or die. This leaves less food for small animals
called zooplankton. Small fish and other creatures who eat the zooplankton leave
the area or starve to death. A few months after the water warms up in the eastern
tropical Pacific, weather patterns around the world begin to change.
Normally, the trade-winds blow strongly from east to west across the tropical
Pacific. This flow of the winds from east to west is part of the Walker Circulation,
named after Sir Gilbert Walker who studied atmospheric circulation in the 1920's.
Walker circulation forces the warm surface water to the west along the equator.
This produces a big pool of water hot as 86°F or 30°C in the western equatorial
Pacific.
As the winds blow along the equator, the Coriolis force causes water to flow
northward away from the Equator in the northern hemisphere and southward in
the southern hemisphere. The water pushed away from the equator must be
replaced by water pulled up from deeper in the ocean, a process called upwelling.
In the west, upwelling brings up warm water. In the east, upwelling brings up
nutrient-rich water as cold as 73°F or 23°C, causing the ocean to teem with life.
El Nino is set in motion when the trade-winds in the western Pacific,
which normally blow quite vigorously, slow down or reverse their
direction. The weak winds can no longer hold the warm pool in the
west. So the warm nutrient-poor water in the west surges back along
the equator towards South America.
Warm water heats the air. The warm air rises and produces heavy rains
shown by clouds in the diagram. As El Niño develops, the rain follows
the warm water eastward into the central equatorial pacific. Because
rain drives the Walker circulation, the circulation changes. Soon the
changed Walker circulation causes a change in weather all over the
world.If you imagine the world as a room, with warm water in the
ocean acting like a heater, you can see how moving the heater could
make parts of the room that were once cold to warm up. Moving this
heater also makes parts of the room that were once warm to cool off.
Eventually, in one to two years, normal air pressure patterns and the
trade-winds go back to normal. Warm water is once again pushed to
the western Pacific, and cold upwelled water returns in the east.
How do currents
affect coastal
climates?
• Ocean currents are
important to coastal
regions because they
can warm or cool air
temperatures along
the coast.
How do
ocean
currents
affect
climate?
• Ocean circulation can
result in climate
changes.
• El Niño: periodic
warming of the ocean
that occurs in the
central and eastern
Pacific
– Tends to happen
April-October
What
causes El
Nino?
• Trade winds normally
blow west towards the
Pacific and push warm
surface water away from
the coast of South
America and towards
Australia/Asia
– This water is cold and rich
in nutrients.
• During El Nino, trade
winds calm down in the
central and western
Pacific, causing warm
water to gather near the
surface.
http://usatoday30.usatoday.com/weather/res
ources/graphics/2008-09-25-el-nino-la-ninaaffect-us-weather_n.htm
Normal conditions
During El Niño
What are the
effects of El
Nino?
• Mudslides in California
from heavy rain
• Droughts US Midwest,
Central America,
Australia
• Unusually mild winters
in eastern US
• Dying off of fish in
western Pacific
because of nutrient
loss.
• ice storms in eastern
Canada and New
England