EARTH SCIENCE > CLIMATE INDICATORS > PALEOCLIMATE INDICATORS > ICE CORE RECORDS > ISOTOPES
The isotopic record found in ice cores reveal direct information about the past climate. d18O (delta oxygen-18), 16O and 18O are isotopes of oxygen with slight differences in atomic weight. Depending on the temperature of evaporation and how far the water has had to travel before it fell as snow, the ratio of 18O to 16O will vary. This ratio, known as d18O, can be measured very accurately using a mass spectrometer. Over short time scales the change in temperature from summer to winter produces a very clear oscillation in the 18O/16O ratio. This oscillation is used to determine the age of the core at different depths, simply by counting the oscillations. Over longer time periods, this ratio indicates the average temperature of the regions between the evaporation site and the coring site. Investigators in Greenland and Antarctica are also analyzing for the ratio of 1H/2H (Hydrogen to deuterium) which will allow even finer detail about source temperature and condensation history to be obtained.
GISP2 Ice core (Greenland) and Climate Change: http://www.gisp2.sr.unh.edu/GISP2/MoreInfo/Ice_Cores_Past.html