Paleo Slide Sets

Paleo Slide Set: Polar Ice Cores

The ratio between the heavier H218O and lighter H216O water molecules in the ice

The ratio between the heavier H₂¹⁸O and lighter H₂¹⁶O water molecules in the ice is expressed as the departure from a standard --d ¹⁸O=1000x(¹⁸O/¹⁶Oice -¹⁸O/¹⁶O std). Snow falling on the Greenland Ice Sheet under colder temperatures is more negative, that is it contains more of the light H₂¹⁶Omolecules. Thus, a plot of the d¹⁸O of snow versus temperature shows an excellent correlation. Since d¹⁸O is primarily temperature-dependent, it serves as a paleothermometer providing important information about past climate.

Photo Credits:
Graphic produced by Thomas Andrews using data from Johnsen et al. (1989)
NOAA Paleoclimatology Program

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