GEOL 300i; Earth Systems and Global Change;
Lecture 12

 
Earth System Models

• Attempt to understand and reproduce the mass & energy transfers between subsystems of the Earth
• Problems & limitations of models
• Inadequate understanding of process
• Inadequate coverage of data in geologic past
• Poor spacial resolution
• Computational power limits chronologic resolution
• Biosphere is a key system
• Yet, perspective is primarily physical/chemical

• James Lovelock & Lynn Margulis (1970’s on)
• Origin
• Physical/chemical disequilibrium of Earth’s atmosphere compared with Mars’
• The biota of the world (biosphere) are primarily responsible for modulating the climate & environment of the Earth to its benefit
• Biosphere regulates the environment, instead of just adapting to it
• Through negative feedback mechanisms
• Achieves homeostasis (dynamic stability)
• Comparable to a single living organism
• Automatically responds to insure survival
• No teleological implication intended
• Life processes have greatly modified the atmosphere & oceans
• Decreased CO₂ (temperature regulation)
• Maintained temperature between 10° -20° C
• By changes in CO₂ concentration
• While the sun’s luminosity has increased 30%
• Increased O₂ (aerobic respiration)
• Atmospheric oxygen maintained between 10-30%
• Built up O₃ (shield UV radiation)
• I.e., the Earth is a self-regulating environment
• Oceanic salinity has remained between 3-4%???
• Symbiosis and cooperation more important than competition
• From a Systems perspective:
• Survival is not important at the individual or species level
• Survival of the ecological system is important
• This can survive for eons

• White daisies
• High albedo
• Black daisies
• Low albedo
• Growth rates of each type depends on local temperatures
• Biosphere can only survive moderate temperatures
• Incidence of solar radiation can change
• White daisies do better at higher temperatures
• They reflect light and don’t get too hot
• Black daisies do better at lower temperatures
• They absorb light and don’t get too cold
• Primary biogeochemical mechanisms
• Biosphere has a strong control of CO₂ cycling
• Photosynthetic removal of CO₂ into organic matter
• Organic matter stored in sediment & recycled by tectonics
• Microbial breakdown of organic matter produces acidic water for weathering
• Marine organisms bind Ca⁺² & HCO₃^- to form CaCO₃
• But, inorganic CaCO₃can also precipitate - "whitings" in Bahamas

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John Francis
Email: jfrancis@csulb.edu
Phone: 562-985-4928
written by R. Behl.
Last changes: 22 Oct. 1997