Jökull - 01.01.2020, Blaðsíða 79

Guðmundsson and Björnsson
VARIATIONS OF KVÍSKERJAJÖKLAR
IN THE 18th, 19th and 20th CENTURIES
Geomorphological records of the terminal positions
of Kvískerjajöklar are distinct but scattered. Con-
spicuous terminal moraines in the canyon foreland
indicate two main glacier advances during the LIA.
The moraines lie largely parallel, separated by tens to
>140 m, although the two outermost moraines sporad-
ically merge. We suggest the end moraine might be
named after the Icelandic naturalist Sveinn Pálsson,
who described it when scaling the easternmost peaks
of the Öræfajökull caldera rim in 1794. He pointed
out that the glacier had retreated a few fathoms from
this moraine (Pálsson, 1945, 2004). Moreover, Páls-
son noted that the canyon west of the farm Kvísker
leads up to the glacier margin. To do so the glacier
tongue had to occupy the gorge Rótarfjallsgljúfur and
reach over its outer rim (Figure 3), otherwise it would
not have been spotted from the farm site. A series
of moraines on the outer rim of the Rótarfjallsgljúfur
gorge, as well as shallow streambeds, most likely in-
cised by glacial water, reflect at least six glacier ad-
vances or short standstills of the glacier front during
the post-LIAmax retreat (Figure 3). This observation
is in accordance with information reported by the late
Flosi Björnsson (1957, 1965, 1998), forwarded orally
to him by his ancestors who lived at Kvísker. Further,
Björnsson states that in the late 1880s the Kvískerja-
jöklar glaciers almost reached the outermost “Páls-
son moraine” and the inner moraine was most likely
formed at this time, he commented. The Kvísker
farmers and the 19th century documents indicate that
through the 18th to the late 19th century glaciers sub-
merged the inner part of Múlagljúfur gorge (Figures 1
and 3) and still remained there until 1930. Series of
moraines indicate several advances between the 1880s
and the 1930s. In the 1880s, the glacier was still at
the outer rim of Rótarfjallsgljúfur but receded some
distance into the gorge near the end of the 19th cen-
tury. In the 1930s, the glacier retreated from the deep-
est section of the gorge and gradually vanished (Hen-
derson 1957; Thoroddsen, 1959; Björnsson, 1998).
Based on this information, we can conclude that Kví-
skerjajöklar had already reached their LIAmax in the
18th century and more or less maintained that ad-
vanced extent until the late 19th century. Therefore,
in our discussion of the glacier changes we use infor-
mation dating to the late 19th century to describe the
glacier extent at the end of the Little Ice Age, but the
glacier most likely reached its largest in the 18th cen-
tury.
The post-LIAmax glacier extent of Kvískerjajöklar
can be traced from a few geodetic maps. The maps of
the Danish General Staff (DGS), based on a triangula-
tion survey of SE-Iceland in 1903–1938, describe the
topography in the early 20th century. However, the
map of Kvískerjajöklar lacks details, as the surveyors
never entered this rugged terrain. No trace is shown
of the Rótarfjallsgljúfur gorge, indicating that it may
still have been occupied by ice at the beginning of the
20th century.
A few photographers, including the English-
man F. W. W. Howell (1857–1901) and the Ice-
lander Magnús Ólafsson (1862–1937), captured sev-
eral glaciers in Southeast Iceland in the 1890s and the
first decades of the 20th century, recording the posi-
tion of the ice margin at several locations around the
time of the LIAmax extent or shortly after the glaciers
started to retreat. However, only one photograph ex-
ists of the upper part of Kvískerjajöklar, taken in 1890
or 1891 by Howell.
Mapping of glacier variations
The positions of the termini were recorded in the field
by GPS, digitized on topographical maps, aerial pho-
tographs, satellite (Landsat) and airborne lidar images
and then all digitized into ArcMap. The area changes
of Kvískerjajöklar since the LIAmax extent to 2016
are shown in Figure 4.
The DGS (1905) maps depict the 1904 extent of
the outlet glaciers of Vatnajökull but they are not ac-
curate for Kvískerjajöklar. The C762 maps of the US
Army Map service (AMS), based on photogramme-
try, and the underlying aerial photographs taken in
1945 (AMS 1951) show the mid-20th century ice mar-
gin. The AMS maps have been proven to be accurate
to ±5 m elevation after co-registration with the lidar
DEMs. Recently, improved DEMs and georectified
images of Öræfajökull have been created by digital
processing of the original AMS stereo imagery (Be-
lart et al., 2019).
76 JÖKULL No. 70, 2020