The Water Cycle and Water Isotopes

Water isotope tracer methods utilize slight mass differences between water molecules that cause them to behave differently during evaporation and condensation during the hydrologic cycle; between gas (humidity), liquid (rain) and solid (snow). Water isotopes are preserved in geologic archives when water molecules are locked into materials from which we can later release without altering their amounts, such as lake and wetland sediments and tree-rings. With well-understood relationships between temperature, humidity and atmospheric circulation, we can reconstruct the climate conditions that existed when precipitation was formed.