Paleo Slide Set: Polar Ice Cores
Delta 18O and accumulation for 10,000-17,400 yr B.P.

This figure shows two important proxy measurements: d18O and accumulation for 10,000-17,400 yr 
B. P. As mentioned earlier, d18O acts as a paleothermometer; accumulation, on the other hand, 
is a measure of annual layer thickness normalized to account for the compression of ice layers 
at depth and corrected for ice flow dynamics. It is thus an approximate measure of past precipitation.

Notice how (as the ECM and calcium data suggested) the climatic regime quickly shifted from cold to 
warm phases during the turbulent glacial-interglacial transition. Researchers have found that major 
climatic changes such as the switch from the cold Younger Dryas event to the warm Holocene epoch may 
have occurred over just a few years, suggesting that climate during the last glacial period was inherently 
unstable and subject to rapid fluctuations. In fact, the last 10,000 years have witnessed the most consistent 
and stable climate in the 200,000 Greenland ice record. Note however, that this same last 10,000 years appears 
to have been less stable at lower latitudes. 

Photo Credits:
Thomas Andrews using data from Grootes and Alley 
Pieter Grootes, University of Washington & Richard Alley, Pennsylvania State University