Rit (Vísindafélag Íslendinga) - 01.06.1976, Blaðsíða 64

5. 5 Deep ice eore studies.
Dansgaard (1954) was the first to propose that the oxygen-18
content of glacier ice might reflect climatic changes of the past.
Since then extensive work has been carried out in this field, on
both of the big polar ice sheets, the Greenland ice-cap, and the
Antarctic ice-sheet.
The most successful work that has been done in this field is
undoubtedly that of Dansgaard et al. (1969), who measured the
oxygen-18 content of a 1390 m long ice core from Camp Century
in North Greenland. The Camp Century ice core, spanning ap-
proximately 120 000 years back in time, has been found to give
oxygen-18 variations that reflect all the climatic events in this
period, known from other independent studies (Johnson et al.
1972, Dansgaard et al. 1973).
Since the deuterium content of the precipitation is closely related
to the oxygen-18 content, the same results could have been obtained
by using deuterimn instead of oxygen-18.
The use of stable isotope profiles in ice as a past climatic record
is mainly of interest in the dry snow zones and possibly also in
the percolation zones of the big polar glaciers. In the soaked zones
of temperate glaciers, where an extensive homogenization has been
found to obliterate the isotopic variations and also to change the
original isotopic content of the accumulation, the method apparent-
ly fails. The ice at the bottom of the temperate glaciers is also
“very young”, possibly 2000 years. Therefore an ice profile from
a temperate glacier would span a very short period, compared with
profiles from the big polar ice-sheets. Under favourable conditions,
however, an ice profile from a temperate glacier might be used to
give a short climatic record.
In 1969, deuterium measurements were carried out on a 106 m
long ice core taken from a drill hole, V-18, on the Vatnajökull
glacier at an altitude of approximately 2000 m. For location of
V—18 see Fig. 11.
Tritium measurements allowed an exact dating of the ice core
back to the year 1954 (P. Theodórsson, Univ. of Iceland, private
communication). The lower part of the core was dated by iden-
tifying two volcanic ash layers preserved in the ice, which were
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