Chapter 8:

Circulation of the Atmosphere Part II

and

Chapter 9:

Circulation of the Ocean Part I

1Photo from The Cloud Appreciation Society

If the Earth’s latitude causes differences

in direct heating of the Earth,

what causes seasons?

2

Temperature is lower at higher

latitudes:

1) Bigger area

2) More atmosphere

3) Reflection is higher (albedo)

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What drives Earth’s temperatures?

Although average

temperature constant,

distribution not equal.

Oceans and atmosphere

move excess heat from

equator to poles.

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Movement of the Atmosphere

• Air always flows from high to low pressure.

• Wind – moving air

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Convection: heat transfer by moving fluids.

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Smaller scale examples of convection cells:

sea breezes (day)

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Smaller scale examples of convection cells:

land breezes (night)

This is a cartoon of a very

simple model of

atmospheric circulation:

you would expect

air to rise at the Equator,

move to the poles,

and sink.

Thickness of the

atmosphere is not to scale!!

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Coriolis Effect

But that’s not what happens

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Coriolis force cause objects to move:

right in northern hemisphere

left in southern hemisphere

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http://www.classzone.

com/books/earth_scie

nce/terc/content/visu

alizations/es1904/es1

904page01.cfm

Chapter 9:

Circulation of the Ocean

“Tropical” gardens on Britain’s Scilly

Isles. Only 48 kilometers (30 miles)

off the coast of Cornwall at 50° N,

these scenic islands lie in the path of

the warm waters of the Gulf Stream.

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Learning Goals:

Circulation of the Ocean

• Ocean circulation is driven by winds and by differences

in water density. Winds and ocean currents distribute

heat worldwide.

• Surface currents: driven by wind, they move in

circular patterns (gyres) around the edges of major

ocean basins. Surface = top 100 meters

• Thermohaline currents: slow, deep currents that affect

the bulk of seawater below the pycnocline.

• Upwelling supports the most productive fisheries.

• El Niño and La Niña affect ocean and atmosphere.

In El Niño years, the normal wind and current flow

changes near the coast of Peru (and influences the

whole world). 14

Winds, driven by uneven

solar heating and Earth’s

spin, drive the movement

of the ocean’s surface

currents.

Two types of winds are

most important to ocean

circulation:

1) powerful westerlies

and

2) persistent trade winds

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Northern

Hemisphere:

Coriolis Effect moves

surface waters to

right of winds.

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Gyres –

surface currents

circulating around

ocean basins

Four processes

(or things)

create gyres:

1. Sun’s heat

2. Surface winds

3. Coriolis effect

4. Land

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For example,

the North

Atlantic Gyre

includes four

currents.

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Earth has 2 northern gyres, 4 southern.

North Pacific Gyre

North

Atlantic Gyre

South Pacific GyreSouth

Atlantic Gyre

Indian

Ocean Gyre

Circum - Antarctic Gyre

Surface currents can be illustrated by

sea surface temperature.

Red: 25°–28°Celsius (77°–82°F).

Yellow: 20°–25°C (68°–77°F);

Green: 15°–20°C (59°–68°F);

Blue: 0°–15°C (32°–59°F).

Purple: below the freezing point of fresh water.

Note the distortion of the temperature patterns we might expect

from the effects of solar heating alone—the patterns twist

clockwise in the Northern Hemisphere, counterclockwise in the

Southern.

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Waters brought from equator – warm-water current

“ “ “ poles – cold-water current

Surface currents, summarized with

names and usual directions.

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