What Goes Around Comes Around:

1. What Goes Around Comes Around: Humankind, the Environmental Crisis, and the Future of Life on Earth Reminder: Earth Sciences 088F Final Exam Saturday, December 9, 2006 7:00 pm Room: Natural Sciences Rm. 1

2. Again…Earth As A Closed System Closed system: exchange of energy but negligible exchange of mass with surroundings

3. Again…The Earth’s Four Spheres

4. The state of the Earth at any given time are the sum of the interactions between Earth’s processes of the four spheres. Significance: If we have any hope in gaining a representative view of the global system, we must appreciate the individual components as well as their interactions. Unfortunately, the systems approach is at odds with the traditional reductionist approach and therefore is slow to become a focus in practical research.

5. Global Warming: Should we care about it ? Obvious effects: Increase aridity of already arid lands Flooding of coastal areas where humans live in high densities At first glance, these appear to be trivial matters Just increase irrigation and stop building close to shore, right ? Direct effects are the least of our worries. What can be learn from looking at the Earth as a system ?

6. An Example of Feedback in the Earth System: Plate Tectonics and Anchovies

7. Plate Tectonic Environments: Note Trench Offshore of Peru (Deep Water)

8. Stratification of Water Masses in Ocean Surface water Boundary Layer (Thermo-/Halo-/Pycnocline) Deep water Surface Water: warm, low salinity, but nutrient poor (high oxygen) Boundary Layer: rapid cooling, increase in salinity, moderate nutrients Deep Water: cold, saline, high nutrients (lower oxygen)

9. Nutrient levels highest in deep, cold water Nutrient poor surface water Nutrient rich deep water Nazca Plate Peru Nutrient levels very high in very deep waters of Peru-Chile trench (trench produced by subduction)

10. Prevailing winds in Peru associated with rising of air at equator. But winds veer westward due to Coriolis force as they approach equator Coriolis effect, in turn, due to Earth’s spin Westward-blowing winds generate westward-flowing currents in Surface water Prevailing winds blow westward

11. El Niño: • A disruption of the ocean-atmosphere system in the tropical Pacific • Having important consequences for weather around the globe. • Among these consequences are: • Increased rainfall across the southern tier of the US and in Peru, which has caused destructive flooding, and drought in the West Pacific • Devastating brush fires in Australia. • Observations of conditions in the tropical Pacific are considered essential for the prediction of short term (a few months to 1 year) climate variations, so such events can be disasterous to the economy.

12. Normal Conditions wind High primary productivity in low P area Warm, nutrient-poor surface waters pushed westward Under normal conditions, surface water is pushed westward, creating low pressure area off coast of Peru Upwelling of cold, nutrient rich waters amplifies primary productivity Thermocline Upwelling of cold, nutrient-rich deep water (to relieve pressure deficit) Warm water Cold water

13. Major contributor to economy of Peru: The Anchovy Fishery Schooling Anchovies !

14. El Niño Conditions Wind decreases in intensity Primary productivity crashes due to nutrient loss Warm, nutrient-poor surface waters slosh back eastward Under El Niño conditions, wind dies down. Warm, nutrient-poor surface water sloshes eastward because wind is not longer pushing it westward Cold, nutrient rich waters no longer reach surface due to loss of pressure gradient Thermocline Upwelling of cold, nutrient-rich deep water shut off or reduced due to loss of pressure gradient Warm water Cold water

15. Normal Winter Weather System Low pressure system usually sits over Southeast Asia/Australia since warm water is pushed westward

16. Weather System During El Niño Event During El Niño event, low pressure system shifts westward, making normally warm, wet weather in Southeast Asia unseasonably dry, and normally cold, dry weather in South America unseasonably warm and wet

17. Increased rainfall, floods in South America. Unseasonably wet conditions felt as far afield as northern U.S and Canada in 1997.

18. Consequences of El Niño Drought in Southeast Asia and Australia Crash in Anchovy fishery in Peru

19. Economic Losses Due to El Niño Economic Losses attributed to 1997-98 El Niño event Note: these disturbances are focused in tropical regions where most countries are of “third world” economic rank.

20. An apparent increase in the frequency of El Niño events through time Global warming decreases wind gradients and therefore makes the “sloshing eastward” of warm, surface waters more likely

21. O.k., So let’s just count on higher frequencies of El Niño and prepare for them. Big Deal, right ? How bad can it be ? Melting of permafrost, release of methane from methane hydrates Anthropogenic greenhouse gas emissions Global warming Deforestation (reduce consumption of carbon dioxide) Anaerobic decomposition of organic wastes (release methane and carbon dioxide) Cattle Ranching (producer of methane) Increase in human population Bottom line: positive feedback makes slight changes BIG CHANGES

22. Another factor: Carbonate Solubility CO2 + H2O + CaCO3= 2HCO3- + Ca 2+ Remember how this equilibrium controls carbonate production in oceans ? Cold water – contains more CO2 so tends to dissolve CaCO3 Warm water – has less CO2 so tends to make more CaCO3 But what if atmospheric CO2 increases ? Increase atmospheric CO2, dissolve more CaCO3in oceans ? CO2 + H2O + CaCO3= 2HCO3- + Ca 2+ How temperature offsets this effect is not yet clear BUT reef growth has been reduced, so less CO2 is being taken up By reef photosynthesis (remember that corals have algal symbionts)

23. What if coral reefs and other carbonate producers are killed off ? Reefs form natural breakwaters in tropical coastal countries, so remove them and be prepared for more destruction from tropical storms. Decrease CO2 uptake, augment CO2 content of atmosphere Further warming Another climatic effect on global warming – climate becomes more erratic, more tropical storms…etc. So another possible feedback loop

24. Yet another scenario… Further increases in fossil fuel combustion It is obvious that fossil fuel use contributes CO2 to the atmosphere But it also increases content of SOx and NOx concentrations SOx and NOx reactwith H2O in the atmosphere, producing sulphuric and nitric acids and increasing acidity of precipitation And we all know what happens when carbonates come in contact with acid, right ?

25. Carbonates react with acid to produce CO2 So, increase acid precipitation, increase CO2 input to atmosphere Warms atmosphere further Bottom Line: Global warming is not a simple matter to clear up But… life goes on.

26. END OF LECTURE