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, :00 pm Room: Natural Sciences Rm. 1

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

Again…The Earth’s Four Spheres

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.

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 ?

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

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

Stratification of Water Masses in Ocean Surface water Deep water Boundary Layer (Thermo-/Halo-/Pycnocline) 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)

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

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

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: 1.Increased rainfall across the southern tier of the US and in Peru, which has caused destructive flooding, and drought in the West Pacific 2.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.

Normal Conditions Thermocline wind High primary productivity in low P area Upwelling of cold, nutrient-rich deep water (to relieve pressure deficit) Warm, nutrient-poor surface waters pushed westward Warm water Cold water 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

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

El Niño Conditions Thermocline Wind decreases in intensity Primary productivity crashes due to nutrient loss Upwelling of cold, nutrient-rich deep water shut off or reduced due to loss of pressure gradient Warm, nutrient-poor surface waters slosh back eastward Warm water Cold water 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

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

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

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

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

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

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

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 ? Global warming Deforestation (reduce consumption of carbon dioxide) Cattle Ranching (producer of methane) Anaerobic decomposition of organic wastes (release methane and carbon dioxide) Melting of permafrost, release of methane from methane hydrates Anthropogenic greenhouse gas emissions Increase in human population Bottom line: positive feedback makes slight changes BIG CHANGES

Another factor: Carbonate Solubility CO 2 + H 2 O + CaCO 3 = 2HCO Ca 2+ Remember how this equilibrium controls carbonate production in oceans ? Cold water – contains more CO 2 so tends to dissolve CaCO 3 Warm water – has less CO 2 so tends to make more CaCO 3 But what if atmospheric CO 2 increases ? Increase atmospheric CO 2, dissolve more CaCO 3 in oceans ? CO 2 + H 2 O + CaCO 3 = 2HCO Ca 2+ How temperature offsets this effect is not yet clear BUT reef growth has been reduced, so less CO 2 is being taken up By reef photosynthesis (remember that corals have algal symbionts)

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 CO 2 uptake, augment CO 2 content of atmosphere Further warming Another climatic effect on global warming – climate becomes more erratic, more tropical storms…etc. So another possible feedback loop

Yet another scenario… Further increases in fossil fuel combustion It is obvious that fossil fuel use contributes CO 2 to the atmosphere But it also increases content of SO x and NO x concentrations SO x and NO x react with H 2 O 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 ?

Carbonates react with acid to produce CO 2 So, increase acid precipitation, increase CO 2 input to atmosphere Warms atmosphere further Bottom Line: Global warming is not a simple matter to clear up But… life goes on.

END OF LECTURE