Rit (Vísindafélag Íslendinga) - 01.06.1976, Qupperneq 50

5. STABLE ISOTOPES IN GLACIERS
5. 1 General.
During the last decade extensive studies have been made on the
isotopic composition of glaciers, both in the uppermost firn layers
and in the deeper strata of the glacier ice. An extensive review of
these studies has already been given, both for polar and temperate
glaciers (Dansgaard et al. 1973, Árnason 1976).
Since the dry snow and percolation zones (Benson 1962) of
glaciers at higher latitudes are known to preserve the entire precipi-
tation in unbroken sequence, it might seem that glaciers are espe-
cially well-suited for the study of the isotopic composition of the
precipitation of the past and its variation with time. The matter is,
however, not quite so simple. From the moment the snow has
settled on the glacier surface the isotopic composition of the snow-
pack begins to change because of various modifying processes. Such
processes affect not only the uppermost firn layers, but may also
affect the entire ice mass.
The modifying processes differ in nature depending on whether
they occur in the dry snow and percolation zones of the polar gla-
ciers, the soaked zones of the temperate glaciers, or in deeper gla-
cier ice. In the dry snow zone and the percolation zone of high
polar glaciers, processes such as snow drift, changes in ice-vapour
systems and diffusion in solid ice are of importance in smoothing
out the stable isotope variations in the precipitation preserved in
the glaciers. These processes are of little importance in the soaked
zones and possibly also in the lowest part of the percolation zones
fotmd on temperate glaciers. On temperate glaciers the most im-
portant process is isotopic exchange in the ice-water system.
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