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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:
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