1. GEOS 112 Lecture Topics 4/28/03 Read Chapter 12 (Glaciers) Final Exam – Monday, May 5 1:00pm 1.Types of Glaciers; 2.Glacier Formation, Mass Balance, and Motion 3.Glacial Landscapes 4. Ice Ages Glaciers and Glacial Processes

2. Major Ice Ages in Earth History Pleistocene epoch = 1.8 m.y. to 10,000 yr ago The classic “Ice Age”

3. Last Ice Age was ~6  C colder than present temperatures Last glacial

4. The Last Ice Age Northern NJ was covered by ~1 km thick ice sheet 30% of the land surface was covered by ice (only 10% is covered today)

5. Sea level was 60 to 80 meters lower than today

6. Evidence of Past Ice Ages 1.Geologic evidence (glacial deposits and landscapes) 2.Oxygen isotope record of marine microfossils 3.Climate records in Antarctic and Greenland ice cores.

7. COLD WARM Marine Oxygen Isotope Record Microfossils made of CaCO 3 18 O/ 16 O is a function of ice volume and hence global temperatures

8. Antarctic/Greenland Ice Core Records 1.Oxygen isotopes of the ice (H 2 O) 2.CO 2 trapped in air bubbles

9. Antarctic Ice Core Data gases trapped in bubbles in the ice oxygen isotope composition of the ice There is a strong correlation between atmospheric composition and global climate; HOWEVER, we don’t know what responds first.

10. COLD WARM Causes of Ice Ages?? Climate change over short time scales (<1,000 years) Related to complex, poorly understand interactions between atmosphere, hydrosphere, and lithosphere

11. The Earth’s Climate System

12. COLD WARM Possible Causes 1.Orbital Parameters of the Earth 2.Changes in Atmospheric Composition 3.Changes in Position of Continents and Ocean Circulation Causes of Ice Ages?? Climate change over short time scales (<1,000 years) Related to complex, poorly understand interactions between atmosphere, hydrosphere, and lithosphere

13. “Milankovitch Cycles”

14. Why do glaciers advance and retreat periodically during an ice age? In 1920, Mulutin Milankovitch showed that regular variations in the shape of Earth's orbit and the orientation of its axis create variations of solar intensity at high latitudes: warm summers in which glaciers retreat, and cool summers when they advance. These climate cycles, called Milankovitch Cycles, are determined by three factors: orbital eccentricity, shown in View 1, changes in the tilt of Earth's axis, View 2, and the precession of Earth's axis, View 3. [by Stephen Marshak] Play Animation Windows version >> Play Animation Macintosh version >>

15. Milankovitch Cycles can explain timing, but not the magnitude of the observed temperature changes

16. COLD WARM Possible Causes 1.Orbital Parameters of the Earth 2.Changes in Atmospheric Composition 3.Changes in Position of Continents and Ocean Circulation Causes of Ice Ages?? Climate change over short time scales (<1,000 years) Related to complex, poorly understand interactions between atmosphere, hydrosphere, and lithosphere

17. Changes in Atmospheric Composition 1.Amount of Volcanic Activity Increased volcanism inputs huge quantities of greenhouse gases (mostly H 2 O and CO 2 ) into the atmosphere

18. Mesozoic Warm Period Changes in Atmospheric Composition 1.Amount of Volcanic Activity Increased volcanism inputs huge quantities of greenhouse gases (mostly H 2 O and CO 2 ) into the atmosphere

19. Breakup of Pangaea increased volcanic activity at mid-ocean ridges, subduction zones, and mantle plumes Permian (~250 Ma) Cretaceous (~100 Ma)

20. 2. Uplift of Large Mountain Ranges (Himalayas, Tibetan Plateau) Increased chemical weathering of exposed rocks lowers atmospheric CO 2 Changes in Atmospheric Composition

21. Cenozoic cooling 2. Uplift of Large Mountain Ranges (Himalayas, Tibetan Plateau) Increased chemical weathering of exposed rocks lowers atmospheric CO 2 Changes in Atmospheric Composition

22. Uplift of Himalaya Mtns and Tibetan Plateau Indian Plate (continental) Eurasian Plate (continental) Exposure of large volume of crust increases chemical weathering and lowers atmospheric CO 2

23. COLD WARM Possible Causes 1.Orbital Parameters of the Earth 2.Changes in Atmospheric Composition 3.Changes in Position of Continents and Ocean Circulation Causes of Ice Ages?? Climate change over short time scales (<1,000 years) Related to complex, poorly understand interactions between atmosphere, hydrosphere, and lithosphere

24. Changes in Position of Continents and Ocean Circulation 1.Geographic Arrangement of Continents: affects ocean circulation patterns and distribution of heat on the planet Disruption of this circulation could cause rapid climate change due to changes in the distribution of heat across the planet

25. Changes in Position of Continents and Ocean Circulation 1.Geographic Arrangement of Continents: affects ocean circulation patterns and distribution of heat on the planet Permian Ice Age

26. Causes of Permian Ice Age?? Large land mass over the south pole global equatorial to polar oceanic circulation blocked

28. The last Ice Age The present interglacial Natural climate change over the last 18,000 yrs

29. COLD WARM The last Ice Age The present interglacial Dust Record in Greenland Ice Core WARM End of last Ice Age was very rapid!! COLD

30. Present Global Ocean Circulation Pattern Disruption of this circulation could cause rapid climate change due to changes in the distribution of heat across the planet