Jökull - 01.12.1983, Side 10

From analysis af Landsat images of Iceland the
following types of glaciological phenomena have
been observed on individual or successive paired
images: (1) glacier advance and recession (includ-
ingsurgingglaciers), (2) eíTecton theglaciersurface
of subglacial volcanic and geothermal activity, (3)
variation in proglacial lakes, (4) efTect of jökul-
hlaups, (5) glacier flow, and (6) ablation pheno-
mena.
Glacier advance or recession has been noted on a
number of sequential Landsat images during the
past decade. Eyjabakkajökull, an outlet glacier in
the northeastern part ofVatnajökull, began to surge
in late August 1972, and had already surged about 1
km by the time of the acquisition of the first Landsat
image of the area on October 14, 1972 (1083-12023)
(Williams et al 1974). A September 22, 1973 image
(1426-12070) showed additional movement of 1.8
km. Figure 2 is an oblique aerial photograph of
Eyjabakkajökull as it appeared on July 25, 1973.
Figure 3 is a Landsat 3 RBV image (30157-11565-
D) of Eyjabakkajökull on August 9, 1978. The
Landsat 3 RBV image has nearly three times better
resolution than the MSS image and shows consider-
ably more detail (Williams 1979, Williams andFerrigno
1981). The advance, during the past several yearsof
Hagafellsjökull eystri, an outlet glacier in south-
western Langjökull, can also be monitored on suc-
cessive Landsat images. An image taken on Sept-
ember 27, 1981, (22440-12034), shows that the
glacier has reentered Hagavatn and is now at
approximately the same position as it was on aerial
photographs taken on Project CJ20A by the U.S.
Army Air Force on September 23, 1945 (Sortie
1234, Roll 1-1, frames 137 and 138). A comparison
with the August 19, 1973 Landsat image (1392-
12191) shows an advance of approximately 2 km
across a 3-km-wide terminus during the past 8
years. Crabtree (1976) compared his field observa-
tions of Mýrdalsjökull with aerial photographs and
Fig. 3. Part of Landsat 3 RBV image 30157—11565—D, which was acquired on August 9, 1978. This
Landsat 3 RBV image of the surging glacier Eyjabakkajökull indicates the amount of detail available on
such images.
Mynd 3. Landsat-mynd frá 9. ágúst 1978.
8 JÖKULL 33. ÁR