Chapter 43 The Biosphere (Sections 43.1 - 43.4)

43.1 Effects of El Niño El Niño is a recurring event in which equatorial waters of the eastern-central Pacific warm above their average temperature During an El Niño, marine currents interact with the atmosphere to influence weather patterns worldwide – causing floods, droughts, and fires Marine food webs along eastern Pacific coasts decline as warm water flow cuts off nutrient supplies to marine primary producers – in 1998, Galapagos sea lions starved to death

Effects on the Biosphere The opposite of El Niño is La Niña, in which eastern Pacific waters become cooler than average – the west coast of the United States gets little rainfall and the likelihood of hurricanes in the Atlantic increases El Niño/La Niña events are some of the factors that influence properties of the biosphere, which includes all places where we find life on Earth

Key Terms El Niño Periodic warming of equatorial Pacific waters and the associated shifts in global weather patterns La Niña Periodic cooling of equatorial Pacific waters and the associated shifts in global weather patterns biosphere All regions of Earth where organisms live

The Biosphere Interactions among Earth’s oceans and atmosphere give rise to El Niño and other climate patterns Figure 43.1 El Ni. Opposite, Ken Bradshaw rides a wave more than 12 meters (39 feet) high, during the most powerful El Ni of the past century. Above, interactions among Earth’s oceans and atmosphere give rise to an El Ni and to other climate patterns.

Effects of El Niño

Animation: Normal vs. El Niño Conditions

43.2 Air Circulation Patterns Climate refers to average weather conditions (cloud cover, temperature, humidity, wind speed) over time Regional climates are influenced by factors that affect winds and ocean currents (intensity of sunlight, distribution of land masses and seas, and elevation) climate Average weather conditions in a region over a long time period

Seasonal Effects Seasonal changes in day length and temperature occur because Earth’s axis is tilted about 23 degrees: In June, the Northern Hemisphere is tilted toward the sun, receives more intense sunlight, and has longer days than the Southern Hemisphere In December, the Southern Hemisphere tilts sunward In each hemisphere, the degree of seasonal change in day length increases with latitude

Earth’s Tilt and Yearly Rotation

Earth’s Tilt and Yearly Rotation D Spring equinox (March). Sun’s direct rays fall on equator; length of day equals length of night. A Summer solstice (June). Northern Hemisphere is most tilted toward sun; has its longest day. Sun Figure 43.2 Earth’s tilt and yearly rotation around the sun cause seasonal effects. The 23ｰ∆ tilt of Earth’s axis causes the Northern Hemisphere to receive more intense sunlight and have longer days in summer than in winter. C Winter solstice (December). Northern hemisphere is most tilted away from sun; has its shortest day. B Autumn equinox (September). Sun’s direct rays fall on equator; length of day equals length of night. Fig. 43.2, p. 724

Earth’s Tilt and Yearly Rotation D Spring equinox (March). Sun’s direct rays fall on equator; length of day equals length of night. A Summer solstice (June). Northern Hemisphere is most tilted toward sun; has its longest day. Sun C Winter solstice (December). Northern hemisphere is most tilted away from sun; has its shortest day. B Autumn equinox (September). Sun’s direct rays fall on equator; length of day equals length of night. Figure 43.2 Earth’s tilt and yearly rotation around the sun cause seasonal effects. The 23ｰ∆ tilt of Earth’s axis causes the Northern Hemisphere to receive more intense sunlight and have longer days in summer than in winter. Stepped Art Fig. 43.2, p. 724

Animation: Orbit Around the Sun

Air Circulation and Rainfall Equatorial regions get more sun energy than higher latitudes At high latitudes, sunlight is absorbed or reflected by more atmosphere, so less energy reaches the ground Energy in an incoming parcel of sunlight is spread out over a larger surface area at higher latitudes Variations in energy from sunlight causes surface warming, which drives global air circulation and rainfall patterns

Variation in Intensity of Solar Energy Figure 43.3 Variation in intensity of solar radiation with latitude. For simplicity, we depict two equal parcels of incoming radiation on an equinox, a day when incoming rays are perpendicular to Earth’s axis. Rays that fall on high latitudes A pass through more atmosphere (blue) than those that fall near the equator B. Compare the length of the green lines. Atmosphere is not to scale. Also, energy in the rays that fall at the high latitude is spread over a greater area than energy that falls on the equator. Compare the length of the red lines.

Circulation and Rainfall (cont.) Two important properties of air: As air warms, it becomes less dense and rises Warm air can hold more water than cooler air Global air circulation and rainfall patterns: At the equator, warm moist air rises and flows north and south, releasing rain that supports tropical rain forests At 30° north or south, dry cool air sinks over deserts At 60°, warm moist air rises again; then cool air sinks at the poles

Surface Wind Patterns Air masses are not attached to Earth’s surface – the Earth spins beneath them, moving faster at the equator and slower at the poles As a result, major winds seem to curve toward the right in the Northern Hemisphere; and toward the left in the Southern Hemisphere The prevailing winds in the United States are westerlies

Circulation Patterns and Major Winds

Circulation Patterns and Major Winds Idealized Pattern of Air Circulation Major Winds Near Earth’s Surface D At the poles, cold air sinks and moves toward lower latitudes. Cooled, dry air descends E Major winds near Earth’s surface do not blow directly north and south because of the effects of Earth’s rotation. Winds deflect to the right of their original direction in the Northern Hemisphere and to the left in the Southern Hemisphere. easterlies (winds from the east) C Air rises again at 60° north and south, where air flowing poleward meets air coming from the poles. westerlies (winds from the west) B As the air flows toward higher latitudes, it cools and loses moisture as rain. At around 30° north and south latitude, the air sinks and flows north and south along Earth’s surface. northeast tradewinds (doldrums) southeast tradewinds Figure 43.4 Global air circulation patterns. A Warmed by energy from the sun, air at the equator picks up moisture and rises. It reaches a high altitude, and spreads north and south. westerlies easterlies Fig. 43.4, p. 725

Circulation Patterns and Major Winds Figure 43.4 Global air circulation patterns. Fig. 43.4, p. 725

Animation: Global Air Circulation Patterns To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

Key Concepts Air Circulation Patterns Air circulation starts with latitudinal differences in energy inputs from the sun Movement of air from the equator toward poles is affected by Earth’s rotation and gives rise to major surface winds and latitudinal patterns in rainfall

Animation: Air Circulation and Climate I To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

Animation: Air Circulation and Climate II To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

43.3 Ocean, Landforms, and Climates The ocean is a continuous body of water that covers more than 71% of Earth’s surface Its water moves in currents that distribute nutrients through marine ecosystems Warm and cold surface currents affect coastal climates

Ocean Currents As in air, sunlight affects ocean temperature and sets major currents moving away from the equator The direction of surface currents is determined by the force of major winds, Earth’s rotation, and topography Clockwise in the Northern Hemisphere Counterclockwise in the Southern Hemisphere Deep, narrow currents flow away from the equator along the eastern coast of continents; shallow, wide currents flow toward the equator on western coasts

Climate and Major Surface Currents Figure 43.5 Major climate zones correlated with surface currents and surface drifts of the world ocean. Warm surface currents start moving from the equator toward the poles, but prevailing winds, Earth’s rotation, gravity, the shape of ocean basins, and landforms influence the direction of flow. Water temperatures, which differ with latitude and depth, contribute to regional differences in air temperature and rainfall.

Regional Effects Mountains, valleys, and other land features affect climate High mountain ranges (such as the Rockies) that parallel the coast block moist air from moving inland, causing a rain shadow on their leeward side rain shadow Dry region downwind of a coastal mountain range

Rain Shadow Effect

Rain Shadow Effect Figure 43.6 Rain shadow effect. On the side of mountains facing away from prevailing winds, rainfall is light. Black numbers signify annual precipitation, in centimeters, averaged on both sides of the Sierra Nevada, a mountain range. White numbers signify elevations, in meters. Fig. 43.6.1, p. 727

Rain Shadow Effect A Prevailing winds move moisture inland from the Pacific Ocean. B Clouds pile up and rain forms on side of mountain range facing prevailing winds. moist habitats C Rain shadow on side facing away from the prevailing winds makes arid conditions. 4,000/ 75 3,000/ 85 2,000/25 1,800/ 125 moist habitats 1,000/25 1,000/ 85 15/ 25 Figure 43.6 Rain shadow effect. On the side of mountains facing away from prevailing winds, rainfall is light. Black numbers signify annual precipitation, in centimeters, averaged on both sides of the Sierra Nevada, a mountain range. White numbers signify elevations, in meters. Fig. 43.6.1, p. 727

Rain Shadow Effect Figure 43.6 Rain shadow effect. On the side of mountains facing away from prevailing winds, rainfall is light. Black numbers signify annual precipitation, in centimeters, averaged on both sides of the Sierra Nevada, a mountain range. White numbers signify elevations, in meters. Fig. 43.6.2, p. 727

Rain Shadow Effect Figure 43.6 Rain shadow effect. On the side of mountains facing away from prevailing winds, rainfall is light. Black numbers signify annual precipitation, in centimeters, averaged on both sides of the Sierra Nevada, a mountain range. White numbers signify elevations, in meters. Fig. 43.6.3, p. 727

Coastal Breezes

Coastal Breezes A In afternoon; the land is warmer than the sea, so the breeze blows onto shore. cool air warm air Figure 43.7 Coastal breezes. Fig. 43.7a, p. 727

Coastal Breezes B In the evening, the sea is warmer than the land; the breeze blows out to sea. Figure 43.7 Coastal breezes. Fig. 43.7b, p. 727

Coastal Breezes A In afternoon; the land is warmer than the sea, so the breeze blows onto shore. cool air warm air B In the evening, the sea is warmer than the land; the breeze blows out to sea. Figure 43.7 Coastal breezes. Stepped Art Fig. 43.7, p. 727

Monsoons Differential heating of water and land also causes monsoons Example: In the summer, hot air rises over Asia, drawing in moist air from the Indian Ocean; in the winter, cool air sinks and a dry wind blows toward the coast monsoon Wind that reverses direction seasonally

Key Concepts Ocean Circulation Patterns Heating of the tropics also sets ocean waters in motion As water circulates, it carries and releases heat, and so affects the climate on land Interactions between oceans, air, and land affect coastal climates

Animation: Major Climate Zones and Ocean Currents To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

43.4 Biomes Biomes are communities with similar climates and vegetation that evolve in widely separated regions as a result of similar environmental factors biome Discontinuous region characterized by its climate and dominant vegetation

Differences Between Biomes Rainfall and temperature are the main determinants of the type of biome in a given region Soils also influence biome distribution Properties of soils vary depending on the types, proportions, and compaction of mineral particles and varying amounts of humus Climate and soils affect primary production, so primary production varies among biomes

Major Biomes and Marine Ecoregions Figure 43.8 Global distribution of major categories of biomes and marine ecoregions.

Major Biomes and Marine Ecoregions Figure 43.8 Global distribution of major categories of biomes and marine ecoregions.

Primary Productivity

Similarities Within a Biome Unrelated species in widely separated parts of a biome may have similar body structures that arose by morphological convergence Example: Cactuses with water-storing stems live in North American deserts, and euphorbs with water-storing stems live in African deserts, but cactuses and euphorbs do not share a common ancestor with a water-storing stem

Animation: Rain Shadow Effect To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

Animation: Major Biomes To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE