What Goes Around Comes Around:

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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 700 pm Room
Natural Sciences Rm. 1
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AgainEarth As A Closed System
Closed system exchange of energy but negligible
exchange of mass with surroundings
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AgainThe Earths Four Spheres
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The state of the Earth at any given time are the
sum of the interactions between Earths 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. Unfortu
nately, the systems approach is at odds with the
traditional reductionist approach and therefore
is slow to become a focus in practical research.
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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 ?
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An Example of Feedback in the Earth System
Plate Tectonics and Anchovies
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Plate Tectonic Environments Note Trench
Offshore of Peru (Deep Water)
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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)
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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)
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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 Earths
spin Westward-blowing winds generate
westward-flowing currents in Surface water
Prevailing winds blow westward
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• 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.

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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
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Major contributor to economy of Peru The Anchovy
Fishery
Schooling Anchovies !
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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
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Normal Winter Weather System
Low pressure system usually sits over Southeast
Asia/Australia since warm water is pushed westward
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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
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Increased rainfall, floods in South
America. Unseasonably wet conditions felt as far
afield as northern U.S and Canada in 1997.
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Consequences of El Niño
Drought in Southeast Asia and Australia
Crash in Anchovy fishery in Peru
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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.
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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
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O.k., So lets 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
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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 CaCO3 in 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)
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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 stormsetc. So another
possible feedback loop
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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 react with 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 ?
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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.
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END OF LECTURE