Transcript How do ocean currents affect climate?

Ocean Currents &
Climate
Currents
Large streams of
moving water that flow
through the oceans
• surface current –
wind-driven currents
which affect water to a
depth of several
hundred meters and
can move as fast as
100 km/day
How do winds impact surface
currents?
• Cause surface currents to flow in the direction
that the wind is blowing.
• Example: Jet Stream
Gyres
Earth’s oceans
contain large, looped
systems of surface
currents called gyres.
Gyres in the northern hemisphere circle clockwise.
Gyres in the southern hemisphere circle
counterclockwise this is known as the Coriolis
effect.
Coriolis Effect
Movement of wind and water to the right or left
that is caused by Earth’s rotation
Deep currents
Caused by differences in density of
ocean water
Deep currents - move and mix
water around the Earth, moving
slower than surface currents,
carrying cold water from poles to
equator
Upwellings – movement of cold
water to the surface to replace
warmer water and bring tiny
organisms, minerals and other
nutrients from deep ocean layers
keeping the ocean ecosystem in
balance.
What causes deep
ocean currents?
• The vertical movement of ocean currents
that mixes with deep waters. Caused by:
• Change in density: Denser water SINKS
– Change in temperature: Decreasing
temperature increases density
– Change in salinity: Increasing salinity
increases density
Climate
Pattern of temperature and precipitation typical of
an area over a long period of time
• Solar energy drives convection currents in the
ocean. Surface currents warm or cool the air
above it, influencing the climate of the land near
the coast.
Great Ocean Conveyor Belt
Another large system of ocean currents that
affect weather and climate. It is a global “belt” of
surface and density currents that distribute
thermal energy around Earth.
Cold water currents:
Bring cold water the
surface to warmer regions
(upwelling)
Warm water currents:
Bring warm water to
colder regions
How do currents affect climate?
• Water holds heat very well (high heat of vaporization!),
so ocean currents easily transfer heat across the Earth
• 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.
How do currents affect
coastal climates?
• Ocean currents are important to coastal regions
because they can warm or cool air
temperatures along the coast. Think about how
it tends to be warm/cold during the
winter/summer on the coast
• Interesting side note – the Atacama desert!
One of the driest places on earth is partially
caused by a coastal current
Atacama Desert
The Atacama Desert is one of the driest places on
Earth. The Atacama is in the country of Chile in South
America. In an average year, much of this desert gets
less than 1 millimeter (0.04 inch) of rain! That makes it
50 times drier than Death Valley in California.
The Atacama is the driest hot desert in the world.
There are some weather stations in the Atacama
where there has never been any rain! Not all deserts
are hot. The Dry Valleys in Antarctica are cold
deserts. They are the driest deserts on Earth.
The Atacama is also one of the oldest deserts in the
world. Scientists think parts of it have been dry for at
least 20 million years and maybe as long as 40 million
years. That is much older than other very dry deserts.
The Dry Valleys of Antarctica are about 10-11 million
years old. The Namib Desert in Africa is only 5 million
years old. Some dry river beds in the Atacama haven't
had water flowing in them for 120,000 years!
Why so dry?
Winds and Currents!
• First there are two air currents that bring dry air into the regio,
second it is located in a “rain shadow” between two mountain
ranges (the Andes and the Chilean Coastal Range) and lastly the
cold ocean current call the Humboldt current carries water up
from Antarctica. The cold current of water cools the air as it is
coming in from the ocean stripping it of moisture because cooler
air can not keep as much moisture as warm air.
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/
resources/graphics/2008-09-25-el-ninola-nina-affect-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