CHAPTER 37 EARTH’S ATMOSPHERE AND OCEANS

Earth’s Oceans Moderate Land Temperatures  Water has a large heat capacity.  So earth is slow to heat up or cool down; to cool down, water has to transfer heat to its surroundings/water absorbs a great deal of heat before its temperatures increase.  Water’s large heat capacity is why land bordering on the ocean have moderate temps.  Compare seasonal variations: San Francisco, Ca stays moderate year-round while Witchita, KS (on the same line of latitude but not bordering on an ocean) experiences major seasonal changes.

Evolution of the Earth’s Atmosphere and Oceans  The ancient atmosphere did not have free oxygen.  It was mostly H & He, with ammonia and methane.  Volcanoes expelled other gases: 80% water vapor, 10% CO 2, and 5% N.  Blue-green algae and stromatolites put O 2 in the atmosphere thru photosynthesis; took in CO 2 and released O 2.  Ozone (O 3 ) was formed in our atmosphere; ozone filters ultraviolet radiation.  As Earth cooled, water vapor condensed to form oceans.

Components of the Earth’s Atmosphere  At sea level, the air is dense and warm.  It gets thinner and cooler as elevation increases.  The atmosphere doesn’t have a defined top- it just gradually thins to outer space.  Air has weight. It exerts pressure. The pressure decreases with increasing height.  Gases include: 78% N, 21% O, 1% Ar, Ne, He, CH 4, and H 2.

Vertical Structure of the Atmosphere Exosphere Thermosphere Mesosphere Stratosphere Troposphere Ionosphere: between upper mesosphere and thermosphere

Solar Energy  Why are the Earth’s equitorial regions always warmer than the polar regions? Tilt Rays High noon at the equator is direct light High noon at the poles is light at an angle

The Seasons  Seasons are caused by variations in the angle of the sun’s rays striking the Earth’s surface.  Earth follows an elliptical path around the sun; the Earth is farthest from the sun when the Northern Hemisphere experiences summer!  It’s not the distance from the sun- it’s the angles of the rays that is responsible for the earth’s surface temperatures.

Tilt Rays also affect the length of daylight.  That’s why at the arctic/antarctic circles they experience 6 months of continuous daylight and 6 months of continuous night.  Summer solstice: longest daylight, June 21/22  Winter solstice: shortest daylight, Dec. 22/23  Vernal Equinox: Mar. 20/21  Autumnal Equinox: Sept. 22/23  In each equinox, the light to day hour ratio is equal

Terrestrial Radiation  The sun emits “solar radiation.”  It enters the atmosphere.  It gets absorbed by the land.  The heat gets remitted back into the atmosphere = “terrestrial radiation.”  Therefore it’s not the solar radiation that directly warms the lower atmosphere, it’s the terrestrial radiation.  The temperature of the earth depends on the amount of solar radiation that comes in versus the terrestrial radiation that goes out.

Terrestrial Radiation

The Greenhouse Effect & Global Warming  Terrestrial radiation gets absorbed by atmospheric gases: H 2 O vapor and CO 2.  This the greenhouse effect. It’s good. It keeps earth from freezing.  As carbon levels rise in the atmosphere, more heat gets trapped so the average temperature of the earth also increases.  Ways in which carbon gets added to the atmosphere are natural and by man: volcanic eruptions, industries and factories burning coal/oil, burning fossil fuels.

Greenhouse effect

Human Impact & Interactions