Ice core methodology - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 106

Figure 3.2. The sintering process as snow is converted to firn and then on to ice with bubbles of
air entrapped (adapted from http://www.csa.com/discoveryguides/icecore/review.php ).

bubbles in ice cores provide a record of atmospheric concentrations of trace gases
including greenhouse gases such as carbon dioxide, methane, and nitrous oxide.
Furthermore, the ice cores contain records of aerosols and dust content resulting
from volcanic eruptions and other changes in particulate content in the atmo-
sphere. The relative atmospheric concentrations of greenhouse gases as well as
aerosol and particulate content coupled with other climate information can
provide insight into both the importance of these as causes or effects of tempera-
ture change, as well as how they might couple in either a positive or negative
feedback sense.
According to Soon and Baliunas (2003a, b):

''The ice sheets that cover Antarctica, Greenland, the islands north of
Canada and Russia, and the tops of some mountainous areas, represent the
accumulation of as much as several hundred thousand years of snowfall. In very
cold, dry areas, such as the interior of Greenland and Antarctica, the record is
particularly good because there is little year-to-year evaporation or melt, and
snow compresses into annual layers of ice. The thickness of these layers is an
indication of the amount of precipitation that fell at that location during the year
the layer was deposited, and the isotopic make-up of the water in the ice can
provide a proxy for temperature . Heavier HDO and H 2 18 O molecules will

condense more quickly than H 2 16 O. The concentration of D and 18 O in the ice
sample is a measure of the temperature at which the snow that formed that ice
fell. However, as more precipitation falls, the water vapor in the atmosphere

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