Jökull - 01.12.1967, Page 39

Elev.
m
Fig. 8: Hypsographic curves o£ Hagafellsjökull
Eystri (cf. Fig. 7), according to the maps of
1938 and 1945. The area, which became de-
glaciated during these 7 years is hatched.
Linurit yfir hœðardreifingu Hagafellsjökuls
eystri samkvcemt kortunum frá 1938 og 1945.
Svæði það, sem jökullinn liopaði af á þessu
sjö ára timabili, er sýnt skástrikað á linuritinu.
this way the ablation per km2 in between each
100 m equidistance was computed. The abla-
tion of Hagafellsjökull Eystri provecl to be as
shown in Table VL
The recession of the glacier in the Tungu-
fljót drainage area and the Langjökull as a
whole was computed from these data and hypso-
graphic curves (Bauer 1955). The recession be-
fore 1938 and after 1945 was then calculated
assuming that the changes in volume of the
glacier were proportional to the changes in its
area (Liestþl 1962) during each period of time.
The obtained results are shown in Table VII.
According to these computations the total
shrinkage of Langjökull from its maximum
extent to that of the year 1966 has been about
31 km3, by far the most of which took place
after 1922. The average annual rate of recession
after 1922 has been about 650 x 10° m3, which
corresponds to a thinning of 59 cm in water
equivalent.
The effecl of the glacial recession
on the discharge of the rivers
Finally some calculation as to the possible
eífect of this great shrinkage of Langjökull on
the discharge of the rivers into which the glacier
TABLE IV
The loss in area of Langjökull and its outlet glaciers since its maximum extent ca. 1890
ca. 1890 1938 1945 1966
km- km2 km2 km2
Hagafellsjökull Eystri 122 109 101 83*
Tungufljót Drainage Area . . . . 304 282 267 240*
Langjökull 1073* 1022 988 924*
Calculated value.
TABLE V
An example of tlie calculations of the loss in volume 1938—1945
Map 1938 Map 1945 Differ-
Elevation Glacier Glacier Dcglaciated ence Ablation
m km2 km2 land, km2 km2
880 72.1 69.7 0.9 1.5 (1.5 + 2) X 20 t
900 69.9 67.2 0.7 2.0 2
JÖKULL 17. ÁR 273