Jökull - 01.12.1970, Blaðsíða 56

Fig. 4. An aerial view of Vedurárdalslón from NW slopes of Fauski, July 27, 1968. The ice-
dammed lake had drained subglacially a few days earlier. Its bottom is covered with ice blocks
and the shore lines can be seen in the mountain slopes. Photo: G. Sigbjarnarson.
Mynd 4. Veðurárdalur 27. júlí 1968. Myndin er tekin úr norðurhliðum Fauska. Lónið hafði
hlaupið fyrir nokkrum dögum. Lónbotninn er þaitinn jakahröngli, en strandlínurnar i fjallahlið-
um sýna vatnshœðina, sem var í lóninu.
Fig. 5. Mount Esja in Esjufjöll seen from the
Skálabjörg on the July 25, 1968. The glaciation
limits were at the black rockwall to the right
on the picture where the horizontal ice sur-
face meets the rockwall at an elevation of 1030
nr above sea level. Higher up it proved im-
possible to measure the lowering of the glacier,
because the hill slopes were more or less cover-
ed with snow and ice.
Photo: G. Sigbjarnarson.
Mynd 5. Esjan í Esjufjöllum 25. júli 1968 séð
frá Skálabjörgim. Hjarnmörkin á jöklinum
lágu við dökka hamarinn SV i Esjunni, en
hann sést til heegri á myndinni. Jökulyfirborðið
liggur þar alveg lárétt upp að klettaveggnum
í um 1030 m y. s. Þar fyrir ofan reyndist ókleift
að mcela jökulþynninguna, vegna þess að fannir
og is lágu i öllum fjallahlíðum.
54 JÖKULL 20. ÁR
only refer to the lowering of the glacier along
the flanks. They do not imply any possible
changes in the slope of the glacier surface
perpendicular to the mountain flank. With
regard to this the measurements can hardly be
expected to give the glacial lowering with
greater accuracy than ± 5 m. In its ablation
area the surface of the glacier is usually frac-
tured and rough and can therefore hardly be
defined with greater accuracy than ± 2 m. It
can therefore be assumed that these lowering
measurements are fairly reliable. Such measure-
ments can only be applied below the glacia-
tion limit because formation of new ice is
always taking place along the slopes of the
nunataks above that limit (Fig. 5). In Esjufjöll
the limit of glaciation proved to be in the
elevation of 900—950 m on the slopes facing
NE but in 1000—1050 m elevation on the moun-
tain slopes facing SW.
THE RECESSION
OF BREIDAMERKURJÖKULL
The above measurements have been used as
a basis for the calculation of the recession of
Breidamerkurjökull the results of which are
summarized in Table 2. The retreat of the
glacier was obtained from measurements of
glacier variations carried out under the guid-
ance of J. Eythorsson (1962, 1963, 1964 and
1966) and later supervised by S. Rist (1968).