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Biogeography: Climate, Biomes, and Terrestrial Biodiversity

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  1. Biogeography: Climate, Biomes, and Terrestrial Biodiversity

  2. Benefits of Blowing Wind • Wind connects all life on Earth • With no wind, the equator would be unbearably hot and the rest of the planet would freeze • Transports nutrients such as dust rich in phosphates blowing across the Atlantic from the Sahara to help replenish the rainforests in Brazil and build up agricultural soils in the Bahamas • Iron rich dust blowing from China’s Gobi Desert falls into the Pacific between Hawaii and Alaska and stimulates growth of phytoplankton • Determines the type of animal and plant life found in major biomes and also influences global air circulation patterns

  3. Harmful Effects of Wind • Wind also transports harmful substances such as particles with banned pesticides blowing from Africa’s deserts to Florida and degrading or killing coral reefs • Asian industrial pollution degrades air quality along the Washington and Oregon coasts • Carries volcanic ash with trace minerals that circle the globe and cools the planet such as the eruption of Mt. Pinatubo in the Philippines • Soil is moved from place to place when left unprotected thus hastening soil erosion

  4. What is Weather? • Set of physical properties in the troposphere • Temperature • Pressure • Humidity • Precipitation • Sunshine • Cloud cover • Wind direction and speed • Computer models use data from balloons, aircraft, radar, etc. to forecast the weather in each box of a 7-layer grid for the next 12 hours • Other models project weather for next several days • Calculates the probabilities that air masses and wind will move

  5. Weather Changeability • Weather changes as one air mass replaces or meets another • Cold air tends to sink and warm air rises • Dramatic weather changes occur along fronts • Fronts – boundary between 2 warm air masses • Warm front – boundary between a warm air mass and cooler one it’s replacing • Rises over cool air • Moisture condenses into droplets to form clouds such as high wispy clouds announcing first signs • Moist warm fronts can bring days of cloudy skies and drizzle

  6. Cold front – leading edge of an advancing mass of cold air • Advancing cold air is dense and stays close to ground • Thunderheads are produced • As overlying warm air is pushed upward it cools and water vapor condenses to form droplets • High – cold air and clear conditions • Low – warm air and bad weather

  7. Weather extremes • Tornadoes – areas of extreme low pressure and very high winds over land, water spouts over water • Tropical cyclones • Hurricanes in the Atlantic Ocean • Typhoons in the Pacific Ocean • They can kill and damage property • They can have long-term ecological and economic benefits • Flushes excess nutrients from land runoff • Channels can be cut to let seawater flood bays • Reduces brown tide • Increases growth of grasses • Increases production of commercially vital species

  8. What is Climate? • A region’s general pattern of atmospheric and weather over 30-1,000,000 years determined by • Average precipitation and temperature • Influenced by latitude, altitude, ocean currents • Affects where people live, how they live, and what they grow • Temperature and precipitation is caused primarily by the way air and water circulate on a round planet.

  9. Global Air Circulation and Regional Climates • Uneven heating of the Earth’s surface • Tropical regions near the equator are hot • Polar regions are cold • Temperate regions have intermediate temperatures • Seasonal changes in temperature and precipitation • Earth’s tilted axis is 23 ½o • Regions are tipped toward or away • Rotation of the Earth on its axis • Prevents air currents from moving due north and south • Force created by rotation – Coriolis Force which creates 6 huge convection cells (Hadley Cells) of swirling air masses • 3 north and 3 south of the equator • They transfer heat and water from one area to another

  10. Long-term variations in the amount of solar energy striking the Earth • Caused by occasional changes in solar output • Caused by slight planetary shifts in which the Earth’s axis wobbles (22,000 year cycle) and tilts(44,000 year cycle) as it revolves around the sun

  11. Ocean Currents Affecting Climates • Water density and previous factors create warm and cold ocean currents • Currents driven by winds and Earth’s rotation redistribute heat and thus influence climate and coastal vegetation • Gulf Stream warms NW Europe • Equatorial currents warm Alaska and northern Japan • Currents mix ocean waters and distribute nutrients and dissolved oxygen • Upwellingsreplace surface water pushed away from land and by constant trade winds blowing along some steep western coasts • Cold, nutrient-rich bottom water • Bring plant nutrients from deep to surface • Support large populations of plankton, zooplankton, fish and fish-eating seabirds

  12. El Nino – Southern Oscillation • Prevailing westerly winds weaken or cease and the surface water along South and North American coasts becomes warmer • Upwellings are blocked and primary productivity is reduced and a sharp decline in fish populations drops • ENSO can trigger extreme weather conditions over 2/3 of the globe, especially the Pacific and Indian Oceans

  13. El Nino – cont’d • In 1997 and 1998, the world experienced the strongest ENSO • Some models project that if Earth’s atmosphere continues to warm, El Nino-like weather will be the norm and cause major ecological and socio-economic problems • The 97-98 ENSO caused a mild winter in the North and Mid-West and blocked hurricanes along the Atlantic preventing loss of life and property damage

  14. La Nina • El Nino is followed by a cooling counterpart called La Nina • More Atlantic Ocean hurricanes • Colder winters in Canada and the Northeast • Warmer and drier winters for the SE and SW and US • Wetter winters in the Pacific NW • Torrential rains in SE Asia • Lower wheat yields in Argentina • More wildfires in Florida • La Nina is worse than El Nino for the US • Evidence shows that US is moving into this pattern for the next 2-3 decades

  15. How chemical makeup of the atmosphere leads to the Greenhouse • Greenhouse gases allow light, infrared radiation, and some UV radiation from the sun through • H2O vapor • CO2 • O3 • CH4 • N2O • CFCs • Earth absorbs and degrades it to long wavelength infrared radiation (heat) which warms the air (greenhouse effect) • The amounts of these gases undergo minor fluctuations over hundreds to thousands of years • However mathematical models of Earth’s climate indicate that natural or human induced global warming taking place could be disastrous for all life on this planet