2. Multi-year time scale variations El Nino and La Nina are important phenomena Occur every ~2 to 7 years when typical ocean-atmosphere circulation breaks down

3. During normal years, warm surface waters in the Pacific lie in the east off Indonesia When the pattern oscillates to an “El Nino”, the warm water shifts east “La Nina” is characterized by colder sea-surface temperatures and stronger trade winds in the eastern tropical Pacific

4. South America During “Normal Years” Warm water in the western Pacific causes low pressure and high rainfall; pressure system drives tradewinds from east to west; tradewinds drive warm water to the west; causing cold water to rise off South America and flow west.

5. South America During “El Nino” Warm water shift to the eastern Pacific causes drought in western Pacific; low pressure over the warm eastern Pacific causes heavy rains and inhibits upwellings along the coast of South America.

6. South America During “El Nino” Warm water shift to the eastern Pacific causes drought in western Pacific; low pressure over the warm eastern Pacific causes heavy rains and inhibits upwellings along the coast of South America. Strong El Nino year 1982-83:

7. 1982-83 El Nino Floods in Peru-Ecuador (600 fatalities) California flooding led to $300 million damages Hurricanes in Hawaii, Tahiti Australia: drought and wildfires

8. 1997-1998 El Nino Effects

9. La Nina hazards Can bring warming and low rainfall to much of U.S. –Can lead to fires Allows growth of hurricanes in Atlantic

10. 19582003 Climate Change

11. Records of Climate Change National Academy of Science Report, 2006

12. Records of Climate Change Historical data Proxy data –Marine sediment –Ice –Coral –Lake sediment –Tree Rings –Boreholes –Glacial advance/retreat –Old glacial deposits, etc.

13. Oxygen isotopes Same atomic number (8) Different atomic mass 99.63%0.0375% 0.1995% concise.britannica.com

14. Delta notation

15. Ice data Influence of temperature on ice composition Record of atmospheric composition

16. earthobservatory.nasa.gov Composition of precipitation versus temperature

17. Greenland and Antarctic Ice Sheet Records >700,000 yrs Layers counted like tree rings Greenland and Antarctic Ice Sheet Records >700,000 yrs Layers counted like tree rings Photos: NASA

18. Figure 21.5A

21. Interpreted from Greenland ice core O-isotope data

22. Seafloor record Microfossils of organisms in surface and bottom water Limited by age of oceanic crust (oldest ~180 my)

23. Source: NOAA

24. Influence of ice volume on O- isotope composition of seawater

25. Ice is depleted in 18 O Residual seawater is enriched in 18 O Positive ( 18 O-enriched) values of organisms indicate larger ice volume Influence of ice volume on O- isotope composition of seawater

26. Figure 21.4

28. Temperature effects The ratio of 18 O to 16 O in foraminifera shells varies slightly depending on the temperature of the surrounding water, as well the water's salinity.

29. Dealing with temperature effect Use benthic organisms in from deep bottom waters (relatively constant temperature) Use trace element ratios tied to precipitation temperature (e.g., Sr/Ca)

30. Figure 21.8

31. Annual growth rings in x-rayed coral (NASA)

32. Chapter 21 Opening Figure

33. Figure 21.6 Ring thickness and density a function of climate (e.g., high latitude and altitude trees sensitive mainly to temperature)

34. Cross dating in dendrochronology

35. Mapping glacial deposits

36. Figure 18.32 300 my old glacial deposits on Pangaea

37. Long term climate record

38. Climate Variations over Time Early earth: atmosphere full of CO 2 Surface would have been much hotter because of greenhouse effect What changed? Much CO 2 has gone into rock form (limestones primarily)

40. Figure 21.5B Interpreted from Greenland ice core O-isotope data

43. Dust can be a large scale process