IBESS Topic 6.1: Introduction to the Atmosphere

Overview

• Main Topic: Atmospheric Systems and Society
• Significant Idea #1: The atmosphere is a dynamic system essential to life on Earth.
• Significant Idea #2: Behavior, structure, and composition of the atmosphere influence variations in ecosystems.

Evolution of Earth's Atmosphere

• First Atmosphere:
  • Composed mostly of hydrogen and helium.
  • Dispersed by solar wind.
• Second Atmosphere:
  • Formed from volcanic outgassing (water vapor, carbon dioxide, methane, ammonia).
  • Oceans formed as Earth cooled, absorbing CO2.
  • Small oxygen amounts produced by photolysis.
• Third Atmosphere:
  • Oxygen levels rose due to photosynthesis by early organisms.
  • Current atmosphere primarily nitrogen and oxygen.

Atmospheric System Dynamics

• Components: Inputs, outputs, flows, storages of energy and matter.
• Energy Dynamics:
  • Incoming solar radiation absorbed or reflected.
  • Long wave radiation emitted and absorbed by clouds and gases.

Structure of the Atmosphere

• Five Atmospheric Layers:
  • Troposphere: Temperature decreases with altitude.
  • Stratosphere: Temperature increases due to ozone layer.
  • Mesosphere: Temperature decreases.
  • Thermosphere: Temperature increases.
  • Exosphere: Outermost layer.
• Pressure: Decreases with altitude across all layers.

Atmospheric Influence on Ecosystems

• Heat Balance:
  • Tropical latitudes gain solar energy; poles lose energy.
  • Atmospheric circulation balances energy distribution.
• Greenhouse Effect:
  • Natural phenomenon maintaining Earth's temperature.
  • Greenhouse gases (CO2, water vapor, methane, etc.) trap infrared radiation.

Human Impact on Atmospheric Composition

• Enhanced Greenhouse Effect:
  • Human activities increase greenhouse gases.
  • Results in higher global temperatures.
• Sources of Greenhouse Gases:
  • CO2 from fossil fuels and deforestation.
  • Methane from agriculture (rice paddies, cattle).
  • Nitrous oxide from fertilizers.
  • CFCs from refrigeration, aerosols.
  • Smog contributes to tropospheric ozone (also a greenhouse gas).
• Ozone Layer Depletion:
  • Caused by air pollution, to be detailed in Topic 6.2.

Conclusion

• Resources: IBESS textbook, Cognity online platform.
• Slides and images by Dr. Nina Markham.

Note: Future topics will cover air pollution (6.3) and stratospheric ozone (6.2) in more detail.