Jökull - 01.12.1971, Blaðsíða 18

Fig. 10.
Position of stakes, pits,
sounding profiles, rain gaug-
es and the meteorological
station. The map of the
glacier was drawn frorn air
photos from the autumn of
1960 and profile surveys on
the glacier in 1967 and 1968.
The contour line through
Depill was defined as 1250
m a. s. 1.
10. mynd.
Staðsetning mælistika, snjó-
gryfja, mœlilína, regnmœla
og veðurathugunarstöðvar.
formation of superimposed ice during the per-
colation of the first melt water. However,
soundings around the ablation stakes did not
indicate formation of any appreciable amount
of superimposed ice.
In the autumn 1967 the mass balance year
terminated about October 1 but in 1968 the
balance liad to be summed up on August 18,
due to lack of observations later in the autumn.
Converting melted ice volume in the ablation
area to water equivalent the ice density was
taken to be 0.9 g/'cm3. The main results of the
mass budget are given in Table 6 and Fig. 12.
The true balances are considered to be within
± 10 cm of the value given.
The net balance was positive in the glacio-
logical year 1967—68. About 21 percent (or
0.25 m water equivalent per km2) of the winter
balance remained on the glacier. Equally di-
stributed over the whole calendar year this net
balance amounts to runoff of 7.9 1/s of water
per km2. ln 1968 the net balance was positive
on August 18 but measurements of the runoff
1 6 JÖKULL 21. ÁR
which continued to later in the autumn, and
measurements of precipitation from Akureyri
suggest that at the end of the glaciological
year at about September 20 the net balance
was appoximately zero or slightly positive. Un-
fortunately, the important height of the equi-
librium line for zero net balance could not be
determined this year.
The stratigraphic method used here gives
both the magnitude of the mass balance terms
and their distribution on the glacier. As it
concerns the magnitude there is a striking
clifference between the two years considered.
Both the winter and summer balance were
greater for the second year than the respective
quantities for the first year. This feature re-
flects the markecl difference between the
general weather conditions in the two years.
On the other hancl there is a clear similarity
in the forrn of the distribution curves, which
can be explained by local factors in orography
and micrometeorology. The summer balance
changes fairly little with height. The reason
*