oceans and atmosphere chapter 13 oceans, winds, waves, and coastlines geology today barbara w. murck...
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Oceans and AtmosphereOceans and Atmosphere
Chapter 13
Oceans, Winds, Waves, and Coastlines
Geology Today
Barbara W. Murck
Brian J. Skinner
N. Lindsley-Griffin, 1999Earth from space. Equator crosses Africa through the green belt, Sahara desert is brown.
Earth’s AtmosphereEarth’s AtmosphereAtmosphere - the gaseous envelope that surrounds a planet or other celestial body.
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
Shuttle view across east end of Mediterranean Sea, NE Africa and the Mideast
(Fig. 13.1, p. 369)
Earth’s AtmosphereEarth’s Atmosphere
Nitrogen and oxygen are the two most abundant gases in the atmosphere. (Fig. 13.2, p. 369)
N. Lindsley-Griffin, 1999
Earth’sAtmosphere
Earth’sAtmosphere
N. Lindsley-Griffin, 1999
The atmosphere is divided into 4 temperature zones divided by pauses, levels where temperature changes greatly.
Fig. 13.3, p. 370
N. Lindsley-Griffin, 1999
80% of atmosphere’s mass Source of most weather
Contains greenhouse gases that trap heat to warm Earth’s surface
The TroposphereThe Troposphere
Greenhouse EffectGreenhouse Effect
N. Lindsley-Griffin, 1999
1) Solar rays enter as short- wavelength radiation.
2) 30% reflected back by clouds; 70% absorbed as heat.
3) Heat energy is radiated back into space as long-wavelength 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)
Ultraviolet Radiation Protection
Ultraviolet Radiation Protection
N. Lindsley-Griffin, 1999
Error in Fig. 13.5 (p. 372):
Thermosphere absorbs short wavelengths
Mesosphere absorbs intermediate wavelengths
Stratosphere absorbs long wavelengths
Ozone layer (O3) in stratosphere
Fig. 13.5, p. 372
Global Atmospheric CirculationGlobal 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
N. Lindsley-Griffin, 1999
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
Global CirculationGlobal Circulation (Fig. 13.7, p. 374)
N. Lindsley-Griffin, 1999
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)
Global CirculationGlobal Circulation
Global Climate ZonesGlobal Climate Zones
N. Lindsley-Griffin, 1999
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)
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”
Climate vs. WeatherClimate vs. Weather
N. Lindsley-Griffin, 1999
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)
MonsoonsMonsoons
N. Lindsley-Griffin, 1999
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
Earth’s OceansEarth’s Oceans
N. Lindsley-Griffin, 1999
Review - Ocean floor features
(Fig. 4.2, p. 90)
Earth’s OceansEarth’s Oceans
N. Lindsley-Griffin, 1999
Surface Layer - About 100 m deep
Relatively warm low-density water
Major life-zone of the sea
Major Ocean Layers
Major Ocean Layers
N. Lindsley-Griffin, 1999
Fig. 13.10, p. 379
View looking west along the equator
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
Major Ocean Layers
Major Ocean Layers
N. Lindsley-Griffin, 1999
Fig. 13.10, p. 379
View looking west along the equator
Surface CurrentsSurface
Currents
N. Lindsley-Griffin, 1999
Surface currents curve CW in No. hemisphere, CCW in So. hemisphere
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.
Deep Ocean CurrentsDeep Ocean Currents
N. Lindsley-Griffin, 1999
Fig. 13.12, p. 381
The cold dense water gradually wells up, becoming warmer and less saline at shallower levels. Cycle = 1000 yrs.
N. Lindsley-Griffin, 1999
Fig. 13.12, p. 381
Deep Ocean CurrentsDeep Ocean Currents
NormalNormal 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)
El NinoEl Nino
N. Lindsley-Griffin, 1999
1
2
3
4
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)
El NinoEl Nino
N. Lindsley-Griffin, 1999
1
2
2
3
4
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 Earth-Moon system.
TidesTides
N. Lindsley-Griffin, 1999
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.
TidesTides
N. Lindsley-Griffin, 1999
Fig. 13.13, p. 384
TidesTides
Targant & Lutgens, J.R. Griffin, N. Lindsley-Griffin, 1999
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 Earth-Moon, counteracts their influence
TidesTides
N. Lindsley-Griffin, 1999
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.