Rit (Vísindafélag Íslendinga) - 01.06.1976, Side 68

Vatnajökull glacier, this station has been chosen since there exists
an unbroken air temperature record back to the year 1860.
Temperature data from Stykkishólmur show that in the two 30-
year periods 1931—1960 and 1891—1920, the mean air tempera-
ture was 4.2°C and 3.1 °C respectively. The mean ðD of the ice
core in the same periods is ðD = — 95.6%0 and ðD = — 100.9%0 re-
spectively. Thus the mean temperature difference at Stykkishólmur
between these two periods At = 1.1 °C is reflected in the deuterium
difference of the ice core AðD = 5.3%0.
Fig. 13 shows that although the five-year means and the fifty-
year means of the ðD-values in the ice vary, the variations fluctuate
within a range of ±10%0 and ±5%0 respectively. Consequently the
mean ðD-values of the present-day precipitation obtained for a given
place in the country, within these limits, are comparable to the
ðD-value of precipitation deposited at the same place in the period
1550 to 1972. ðo18-measurements carried out on two Greenland ice
cores, Camp Century (Dansgaard et al. 1969) and Crete (Dans-
gaard et al. 1974), show that the ðD-variations in these ice cores,
for the period 1700—1960 A.D., are quite comparable in ampli-
tude to the ðD-variations found in the V—21 core. Furthermore, the
Camp Century ice core shows that the ðD-variations throughout the
past 8000 years are of similar size. The Camp Century record ob-
tained by Dansgaard et al. is given in Fig. 14. In the period of the
last glaciation, 10 000 to 60 000 years ago, the ðD-value of the Camp
Century core on the other hand was 50%o to 100%o lower than the
present.
According to Dansgaard et al. (1971) the ð018-values (and also
the ðD-values) of the Camp Century core are found to reflect clima-
tic changes of the past, resulting in much lower ð-values in the
cold glaciation period.
It is not possible to compare quantitatively the ðD-values of the
precipitation in North Greenland and Iceland. It is however rea-
sonable to assvnne that the ð-values at both places show a similar
trend in general. Consequently it is to be expected that there have
been no great climatic changes, resulting in great changes in the
ðo-value of the precipitation in Iceland, during the past 8000 years.
Thus the ðD-value of the precipitation deposited at any location in
the country during this time has only varied within the same range
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