Ice core methodology - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 132

Figure 3.19. Rate of accumulation increased in the Holocene (Cuffey and Clow, 1997).

Use of climate models
An atmosphere general circulation model was used by Werner et al. (2000) to
estimate Greenland temperatures during the LGM about 20 kybp , and these
results support the borehole estimates rather than the isotope correlations. This
corroborates the belief that the temperature difference from today during the
LGM was about twice as great during the LGM as the isotope correlations would
predict. The most plausible explanation for this discrepancy is that during the
LGM, it was so cold in the Greenland area that precipitation was greatly reduced
during winter seasons. Thus, most of the precipitation occurred in summer. The
contrast between summer and winter precipitation is illustrated in Figure 3.20 . As
this diagram shows, summer precipitation produces a lower isotope ratio than the
yearly average.

Figure 3.20. Difference between isotope ratios in summer and winter (adapted from

Thorsteinsson).