2: The Physical Environment
- Page ID
- 103314
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Chapter Summary
The ultimate source of energy driving the motion of the atmosphere and the ocean is radiant energy from the sun, which falls on different parts of the Earth in differing amounts. The oceans are the recipient of most of this solar energy, and they are therefore a major factor in regulating Earth’s climate. Climate is the prevailing weather conditions in an area in general or over a long period (years, decades, etc.) and includes seasonal and daily changes. Descriptions of climate usually include average temperature, humidity, wind, precipitation, as well as seasonal variability.
Species distributions are limited by tolerance to abiotic conditions. Each species has a set of environmental conditions within which it can best survive and reproduce. Temperature is one of many abiotic forces influencing where life can exist and the types of organisms found in different parts of the biosphere. Therefore, an understanding of the physical environment is key to understanding all ecological phenomena.
After reading this chapter you should be able to:
- Describe how differential heating of Earth's surface creates 3 climate zones: tropical, temperate, and polar.
- Describe the green house effect.
- Explain the some of the ways the oceans contribute to climate regulation.
- Explain how the Coriolis effect contributes to global wind patterns.
- Describe the location and directions of earths major surface currents (gyres).
- Explain the causes and effects of ENSO.
- 2.1: Climate
- Climate is the prevailing weather conditions in an area in general or over a long period. It is largely influenced by heat energy absorbed and transported by Earth’s atmosphere and oceans, creating three climatic zones; (tropics, temperate, and polar). Different kinds of living organisms, communities, and ecosystems exist in each of these zones.
- 2.2: Differential Heating of Earth's Surface
- Because the Earth is a sphere, sunlight is not equally distributed over the Earth’s surface. More sunlight reaches the Equator than the poles. This differential heating drives atmospheric circulation, creates wind which blow over the land and oceans, and create waves and surface currents. Both the atmosphere and the oceans distribute significant heat energy around the globe.
- 2.3: Atmospheric Circulation
- Uneven heating of Earths surface, with the tropics receiving more sunlight energy than the poles, drives Earths major atmospheric circulation cells. There are 3 cells in both the northern and southern hemisphere; the Hadley, Ferrell, and Polar cells. As the air in these cells moves over the surface of the Earth it is deflected to the right in the norther hemisphere, and the left in the southern hemisphere by the Coriolis Effect.
- 2.4: Global Winds and Precipitation
- The atmospheric circulation cells determine the amount of precipitation a region receives. As warm moist air rises higher into the atmosphere it cools. Cool air can't hold as much moisture as warm air so the moisture condenses into clouds and eventually rain or snow. Forests tend to dominate these areas of the globe. By the time the air sinks back towards Earth's surface it has lost most of its moisture and as a result, these regions of the globe tend to be dominated by deserts or other dry land
- 2.5: Oceanic Circulation
- Surface currents are driven by prevailing winds. Because of Coriolis deflection and the location of Earth's land masses surface currents form large-scale circular patterns of circulation called gyres that affect the top 200 meters. Thermohaline circulation describes the movement of deep ocean water. These currents are slow moving, driven by changes in water density, and overturn Earth's oceans every 1,000 years or so. Both surface and deep ocean circulation transport vast amounts of heat energy