Jökull - 01.12.1982, Síða 32

Numerous detailed morphological maps ofparts
of the area are included in various papers (Price
1969, 1970, 1971, Howarth 1971, Derbyshire 1974).
The aerial photographic coverage of the area is as
follows:
Date Approx. Scale
August 1945 1:46,000
July 1960 1:36,000
July 1961 1:37,000
June 1964 1:40,000
Sept. 1964 1:30,000
August 1965 1:15,000
Sept. 1980/81 1:36,000
Source
U.S.A. Dept. of Defence
Landmaelingar Islands
Landmaelingar Islands
Landmaelingar Islands
Landmaelingar Islands
Glasgow University
Landmaelingar Islands
The cartographic and photographic record of the
area can also be supplemented by some excellent
local information provided by Mr. Flosi Björnsson
of Kvísker. There can be few glaciers and proglacial
areas in the world for which exist such a detailed
record of ice matginal positions, ice wastage and
morphological and drainage changes.
THE RETREAT AND DOWNWASTAGE OF
BREIDAMERKURJÖKULL
Breidamerkurjökull reached its maximum extent
in historical times about 1890 (Thorarinsson 1943, p.
29). Remnants of the moraine ridge formed at the
maximum extension of the glacier still exist and are
marked on the 1903 Danish Geodetic Survey (Fig.
la). From the published maps and the available
aerial photographic coverage it is possible to record
the retreat of the ice front (Fig. 2) and the down-
Fig. 2. Position of the front of Breidamerkurjökull
in 1903/04, 1945, 1965, 1980. A-B, C-D lines of
profiles in Fig. 3.
Mynd. 2. Lega jaðars Breiðamerkurj'ókuls árin 1903/04,
1945, 1965, 1980.
Fig. 3. Profiles of the surface of Breidamerkurjök-
ull along lines A-B, and C-D. Fig. 2.
Mynd 3. Snið afyfirborði Breiðamerkurjökuls á línum A-
B og C-D, sjá mynd 2.
wastage of the ice surface since 1903 (Fig. 3). The
period between 1903 and 1948 involved an average
rate of annual frontal retreat ofbetween 30 and 40 m
along both profiles (A-B, C-D on Fig. 2). Between
1945 and 1965 therate of frontal retreat increased to
between 53 m (C-D) and 62 m (A-B) per one year
and increased again along line A-B between 1965
and 1980 to 70 m per year while decreasing along
line C-D to48 m peryear. Therateoffrontal retreat
is controlled not only by the rate of downwastage of
the ice surface but also by the angle and direction of
the ground surface across which the glacierfront is
retreating (Príce 1969, Fig. 3). The average rate of
frontal retreat along both A-B and C-D between
1903 and 1980 has been approximately 50 m per
year. The average rate of downwastage of the ice
surface at a location 1 km up glacier from the 1965
ice margin has been approximately 4 m per year.
Although the general picture at Breidamerkurjökull
is one of ice wastage and frontal retreat small re-
advances have been recorded. In the east, read-
Fig. 1. Breidamerkurjökull and its proglacial area.
A. 1903/04. Based on Danish Geodetic Institute
Map: 1:100.000.
B. 1945. Based on University of Glasgow photo-
metric map: 1:30.000.
C. 1965. Based on University of Glasgow photo-
metric map: 1:30.000.
D. 1980. Based on 1965 map with modifications
from 1980 aerial photography.
Mynd 1. Breiðamerkurjökull og svæði framan við hann.
30 JÖKULL 32. ÁR