Determining Past Climate Change - Oxygen Isotopes

• normal oxygen contains 8 protons, 8 neutrons (O₁₆)
• a small fraction (one in a thousand) of oxygen atoms contain 8 protons, 10 neutrons (O₁₈)
  • this is an isotope of oxygen and is heavier than O₁₆
• O₁₆ will evaporate more readily than O₁₈ since it is lighter
• Hence, during a warm period, the relative amount of O₁₈ will increase in the ocean waters since more of the O₁₆ is evaporating
• Hence, looking at the ratio of O₁₆ to O₁₈ in the past can give clues about global temperatures.

• Ice cores from glaciers can also give you similar information

image adopted from The Amosphere by Lutgens and Tarbuck, © 1998 by Prentice-Hall, Inc