Ice core data - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 155

According to them, ''these ice core histories provide compelling evidence that
the growth (glaciation) and decay (deglaciation) of large ice fields in the lower
latitudes are often asynchronous, both between the hemispheres and with high
latitude glaciation that occurs on [long] timescales.'' They concluded that, despite
the fact that global-scale cooling occurred during the last ice age, precipitation was
the primary driver of glaciation in low latitudes. There appear to be many excur-
sions in the d 18 O profiles that most likely derive from changes in precipitation
patterns. However, several of the records show a sharp (positive) increase in d 18 O
between 10 and 15 kybp , which do appear to be responsive to the worldwide
deglaciation that took place. Nevertheless, the Guliya record from Tibet does
seem to demonstrate precipitation change as a major factor in mid-latitude ice
records. Ice core records have been systematically recovered from mid-latitude
high-elevation ice fields across the Tibetan Plateau (Thompson et al. 2006).
4.6 CARBON DIOXIDE
Petit et al. (1999) measured the CO 2 content of gases encased in the Vostok ice
core and found the results shown in Figure 4.20 . The peaks and valleys of the
CO 2 vs. time curve are quite similar to the temperature vs. time curve. These
results show a basically repeatable pattern in which the concentration of CO 2 in
the atmosphere ranges from about 180-200 ppm during glacial peak periods and
about 280 ppm during interglacial periods.
Figure 4.20. Vostok (Antarctica) record of CO 2 ,CH 4 , and temperature (from d D) (Petit et al.,
1999).