6. DAISY WORLD, LIGHT/DARK DASIES EFFECT OF DASIES ON GLOBAL CLIMATE

7. EFFECT OF CARBON DIOXIDE ON GLOBAL CLIMATE AS SUN EVOLVES AND WARMS.

8. The Ice Ages

9. What is an Ice Age Ice ages are times when large areas of the earths surface are covered with ice sheets The term can be used to describe time periods when the earth is at a cooler temperature than usual(10-100 million years), or shorter time periods when glaciers are at their maximum extent (10s of thousands of years)

10. Causes of Ice Ages There are many factor thought to influence the creation of ice ages Plate Tectonics Milankovich Cycles Ocean and Atmospheric Circulation Volcanic eruptions Solar Cycles (i.e. Sunspots)

11. Plate Tectonics Plate tectonics is believed to be a factor in the development of ice ages Large ice sheets can form when landmasses are in and near polar regions Plate tectonics also can affect atmospheric and ocean currents

13. EXTERNAL INFLUENCES ON CLIMATE

15. Milankovich Cycles Milankovich Cycles arise from orbital variation of earth about the sun There are three main variations in the earth’s motion around the sun; Orbital Eccentricity, Obliquity, and Precession These factors affect the amount of radiation the earth receives from the sun

16. Orbital Eccentricity The earths orbit around the sun is slightly elliptical with the elongation of the ellipse changing about every 100,000 years The more elliptical the orbit of the earth, the greater the contrast in temperature between summers and winters in both hemispheres

17. Orbital Eccentricity

18. Obliquity The axis of the earth is tilted 23.5 degrees at this time The tilt of the earth varies from 22.1 degrees to 24.5 degrees The tilt of the earth varies on a 41,000 year cycle The smaller the tilt angle, the less radiation the poles receive

19. Obliquity

20. Precession Precession is just the wobble of the earth axis The means that the seasons are not always at the same spot on the earths orbit A Precession cycle takes about 23,000 years

21. Precession

22. Milankovich Cycles The conditions most conducive to an ice age would be Orbital eccentricity at its maximum Obliquity at its minimum Precession so that summer is farthest from the sun and winter is closest to the sun

23. Solid red line is “my average”, Data show large, fast changes

25. Atmospheric and Oceanic Circulation Changes in Atmospheric and Oceanic Circulation can promote the beginning of an ice age E.G. currents that bring warmer water near the polar regions can start ice ages because of increased precipitation, as resulted from opening Strait of Magellan 25 M years ago

26. Atmospheric and Oceanic Circulation For example, 3.5 million years ago, the Isthmus of Panama formed,and cut off east- west ocean current circulation. This strengthened the gulf stream. The gulf stream then brought warmer water to the northern hemisphere which increased precipitation over the north pole, initiating the formation of ice sheets, as the theory goes...

27. Volcanic eruptions Volcanic eruptions can reduce the radiation from the sun that reaches the surface of the earth by the release of ash into the air Only extremely large, or continuing eruptions can effect global climate The Mt Pinatubo eruption in 1991 cooled the climate of Europe by about 1 degree for 1 year. A more dramatic example, is shown Mt. Tambora eruption of April 10, 1815...

28. Volcanic Eruptions

29. Sunspots Sunspots are magnetic storms on the sun. These regions are cooler than the rest of the sun The solar wind is increased when there are more sunspots, because of high magnetic activity which enhances particle ejection processes Thus fewer sunspots means less energetic input from the sun which lowers Earth’s temperature, as occurred in the ‘Maunder Minimum(~1650 -1720)

30. Factors lengthening ice ages Once large continental ice sheets form they create a positive feedback loop making the temperature colder This results from the high albedo for ice, which reflects solar insolation well Thus less of the Sun’s radiation is absorbed by the Earth, reducing the temperature

31. Additional factors Glaciation causes heavy erosion of rocks by ice grinding the rock surface This releases minerals and rock debris to exposure to the air and reaction with CO2 This causes a reduction of CO2 which causes an “Ice house” effect

32. Some Effects of Ice ages Rise and fall of sea level as water is contained/released from glaciers on land into the oceans (not sea ice) Great amounts of erosion and deposition For example: carving of mountain valleys by glaciers, and formation of the flat topography and rich soils in the northern Midwest Isostatic depression and rebound from effects of continental glaciers

33. ISOSTATIC REBOUND IS CONTINUING IN SCANDANAVIA TODAY... ISOSTATIC DEPRESSION OF A CONTINENT

34. Predictions for the next ice age Predictions are that the next glaciation will occur sometime after the next 5,000 years ?? This is based on the Milankovich Cycle Theory The greenhouse effect could make it more difficult for ice ages to happen, or could accelerate it... A catastrophic volcanic eruption could occur at any time, releasing atmospheric aerosols … e.g. Yellowstone and Huckleberry Ridge...