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Oceans and
Atmosphere
Chapter 13
Oceans, Winds,
Waves, and
Coastlines
Geology Today
Barbara W. Murck
Brian J. Skinner
N. Lindsley-Griffin, 1999
Earth from space. Equator crosses Africa
through the green belt, Sahara desert is brown.
Earth’s Atmosphere
Atmosphere - the
gaseous envelope that
surrounds a planet or
other celestial body.
Shuttle view across east
end of Mediterranean
Sea, NE Africa and the
Mideast
(Fig. 13.1, p. 369)
Air is the gaseous
envelope that
surrounds the Earth.
Aerosols - small liquid or
solid particles suspended
in the air (fog, smoke)
Humidity - amount of
water vapor in air.
N. Lindsley-Griffin, 1999
Earth’s Atmosphere
Nitrogen and oxygen are the two most abundant
gases in the atmosphere.
(Fig. 13.2, p. 369)
N. Lindsley-Griffin, 1999
Earth’s
Atmosphere
The atmosphere is
divided into 4
temperature zones
divided by pauses,
levels where
temperature
changes greatly.
N. Lindsley-Griffin, 1999
Fig. 13.3, p. 370
The Troposphere
80% of atmosphere’s mass
Source of most weather
Contains greenhouse gases that trap heat to warm Earth’s surface
N. Lindsley-Griffin, 1999
Greenhouse Effect
1) Solar rays enter as shortwavelength radiation.
2) 30% reflected back by
clouds; 70% absorbed as heat.
3) Heat energy is radiated
back into space as longwavelength infrared energy.
4) Greenhouse gases absorb
radiated heat, slow down its
escape, help to heat air and
planet’s surface.
(Fig. 13.4, p. 371)
N. Lindsley-Griffin, 1999
Ultraviolet Radiation
Protection
Error in Fig. 13.5 (p. 372):
Thermosphere absorbs short
wavelengths
Mesosphere absorbs
intermediate wavelengths
Stratosphere absorbs long
wavelengths
Ozone layer (O3) in stratosphere
N. Lindsley-Griffin, 1999
Fig. 13.5, p. 372
Global Atmospheric Circulation
Sun’s heat and Earth’s
rotation cause oceans
and air to circulate.
Surface heats more
where Sun’s rays are
perpendicular…
less where rays are at
angle to the surface.
Warmer air/water flows
towards colder areas
N. Lindsley-Griffin, 1999
Fig. 13.6, p. 373
Global Circulation
(Fig. 13.7, p. 374)
Uneven heating creates huge
convection cells in the
atmosphere as hot air rises.
Convergence = trade winds
Equator - rising hot air, low P
air cools along top of cell
Subtropics - cool air sinks, hi P
air warms along bottom of cell
Polar front - warm moist air rises,
low Pressure
Poles - cold dry air descends, high
Pressure
N. Lindsley-Griffin, 1999
Global Circulation
Coriolis Force - tendency of
free-floating things (air,
water) to veer off course.
Causes the rising equatorial
air to move at an angle
instead of directly towards
poles.
Atmospheric and ocean
currents are both affected by:
Coriolis Force
arrangement of continents
and oceans.
(Fig. 13.7, p. 374)
N. Lindsley-Griffin, 1999
Global Climate Zones
Climate zones are controlled by air and ocean circulation
patterns: rainforests form where rising warm air cools off and
loses its moisture, deserts where dry air descends to surface.
(Fig. 13.8, p. 375)
N. Lindsley-Griffin, 1999
Climate vs. Weather
Weather - local
atmospheric conditions at
any particular time
Climate - weather
patterns averaged over a
long period of time
“Typical weather” is a
myth - weather actually
fluctuates between
extremes whose mean or
average is “climate”
N. Lindsley-Griffin, 1999
Monsoons
Monsoons = Seasonally reversing winds:
Winter winds blow from high cold central Asian plateau - dry
because cold air holds little moisture, and there is no source.
Summer winds blow from warm moist Indian Ocean - heavy
rains and hot humid weather.
(Fig. 13.9, p. 377)
N. Lindsley-Griffin, 1999
Earth’s Oceans
Oldest rocks on Earth are about 4.0 b.y. old, gneisses that
were once sedimentary strata. Therefore, liquid water covered
much of the Earth foe at least 4.0 b.y.
- Probably condensed from steam during volcanic eruptions
N. Lindsley-Griffin, 1999
Earth’s Oceans
Review - Ocean floor features
(Fig. 4.2, p. 90)
N. Lindsley-Griffin, 1999
Major
Ocean
Layers
Surface Layer - About 100 m deep
Relatively warm low-density water
Major life-zone of the sea
Fig. 13.10, p. 379
View looking west along the equator
N. Lindsley-Griffin, 1999
Major
Ocean
Layers
Thermocline - water temperature decreases rapidly
as depth increases (Figure caption wrong in book)
Deep zone - water is uniformly cold (2 C), dense
Note that both reach surface near poles
Fig. 13.10, p. 379
View looking west along the equator
N. Lindsley-Griffin, 1999
Surface
Currents
N. Lindsley-Griffin, 1999
Surface currents
curve CW in No.
hemisphere,
CCW in So.
hemisphere
Deep Ocean Currents
Deep ocean currents begin in Polar regions where cold dense
water sinks and spreads slowly outward. Saline because of sea
ice formation which removes fresh water from ocean.
Fig. 13.12, p. 381
N. Lindsley-Griffin, 1999
Deep Ocean Currents
The cold dense water gradually wells up, becoming warmer
and less saline at shallower levels. Cycle = 1000 yrs.
Fig. 13.12, p. 381
N. Lindsley-Griffin, 1999
El Nino
4
Normal years:
1) Cool deep water
upwells off Peru.
2) Tradewinds and
warm currents move
east to west.
3) A warm water pool
forms in the western
Pacific, causing moist air
to rise and cool off.
4) Cooling initiates
precipitation and
abundant rain falls on
Indonesia.
(Fig. B13.1, p. 383)
N. Lindsley-Griffin, 1999
2
3
1
El Nino
El Nino years:
1) Tradewinds slacken
and warm water moves
to central Pacific.
2) Air currents reverse;
cool, dry air descends
over Indonesia, bringing
drought.
3) Rising moist air over
the warm water pool
increases precipitation
over the central Pacific.
4) Eastern Pacific water
warms up, downwelling
shuts off nutrient supply,
kills fish.
(Fig. B13.1, p. 383)
N. Lindsley-Griffin, 1999
2
2
3
1
4
Tides
Tides - the cycle of
regular rise and fall of
water level in large
bodies of water.
Result from
gravitational
interaction of the
Moon, the Sun, and
Earth, together with
inertia of the EarthMoon system.
N. Lindsley-Griffin, 1999
Tides
On the side facing the
Moon, gravity distorts
water into a tidal
bulge.
On the opposite side,
inertial forces are
greater than pull of
Moon’s gravity and a
bulge forms in the
other direction.
Bulges remain
stationary while Earth
rotates through each.
Fig. 13.13, p. 384
N. Lindsley-Griffin, 1999
Tides
Spring Tides -- maximum range
Twice monthly
Earth, Moon, and Sun aligned
Sun adds slight pull.
Neap Tides -- minimal range
Twice monthly
Sun 90 degrees away from EarthMoon, counteracts their influence
Targant & Lutgens, J.R. Griffin, N. Lindsley-Griffin, 1999
Tides
Bay of Fundy, Nova Scotia
Has some of the largest
tidal ranges in the world
- Because bay narrows
towards its tip, forcing
tidal waters to constrict
and build up higher.
Tidal Bore - An actual
wave moves up the bay at
the front of the advancing
tide.
N. Lindsley-Griffin, 1999