Rit (Vísindafélag Íslendinga) - 01.06.1976, Side 66

each year has been dated by using tritium measurements (P. Theo-
dórsson, personal communication). At depths of 32 m, 87 m, 110 m,
118 m, 177 m, 236 m, 315 m and 372 m, the core has been dated
accurately by identifying volcanic ash layers found at the respec-
tive depths (Steinþórsson, 1975). The dating is still uncertain for
depths exceeding 372 m, but it is hoped that more detailed studies
of several volcanic ash layers found in the deepest part of the core
will permit accurate dating of this part of the core also. The present
studies, however, indicate that the ice at the bottom of the hole
originates from precipitation deposited approximately in the year
1550.
The deuterium record in the uppermost part of the 415 m core
from V-21, extending back to the year 1917, shows a very similar
trend to that of the 106 m core from V-18. The shortterm ðD-varia-
tions of the precipitation have obviously been preserved in the firn
for several years, indicating that even at an altitude of 1800 m the
isotopic content of the ice is not seriously disturbed by percolation
of meltwater. The 8D-variations with an amplitude of several years
found in V—18 are also reflected in the V—21 core.
The detailed deuterium results obtained for the deep core will
be presented in a separate paper, together with other studies per-
formed on the core. In this work we are mainly interested in how
the mean deuterium content of the precipitation changes over longer
periods of time. This information can obviously be obtained from
the above studies for a period of approximately 400 years.
Fig. 13 shows five-year means and fifty-year means of the 8D-
content of the V—21 core plotted against the age of the ice. The
time-scale is based on the identified tephra layers. Between the
tephra layers the scale is simply interpolated, assuming equal thick-
ness for each year. As mentioned previously the dating is expected
to be reliable to a depth of 372 m, corresponding to the year 1725.
Before 1725 the age of the ice is rather uncertain.
Apparently the 8D-values of the core reflect climatic changes,
where colder climate results in lower 8D-values. It is interesting to
compare the air temperature data from the Stykkishólmur weather
station with the 8D-data of the ice core. In spite of the fact that Styk-
kishólmur is located in the western part of the country far from the
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