Jökull - 01.12.1985, Blaðsíða 63

Survey of Gljúfurárjökull and Features associated
with a Glacier Burst in Gljúfurárdalur,
Northern Iceland
C.J. CASELDINE
Department of Geography
University of Exeter, UK
ABSTRACT
Survey ofthe marginal area of Gljúfurárjökull in 1983
has showed the glacier to have advanced 25 m between
1981 and 1983. Further lichenometric work was under-
taken re-examining some of the problems encountered
earlier in establishing the character of recent deglaci-
ation. A number of permanent lichen sites were also set
up to eventually make direct observations of lichen
growth rates. Detailed surveying and sampling of a
largely depositional feature found at the ice margin was
also undertaken and it is suggested that it was formed
very rapidly due to a ”burst“ of water in the ice-marginal
zone during the 1982—83 winter season.
INTRODUCTION
Gljúfurárjökull, a small valley-head glacier lying
above the main glacial trough of Skiðadalur in the
Tröllaskagi peninsula in Northern Iceland, has been the
subject of several studies of recent marginal fluctuations
and of the pattern of deglaciation experienced over the
last century. Although observations of such changes
have been and are still made largely by Icelandic work-
ers (Eythórsson 1956, 1963; Rist 1977, 1983), work has
also been undertaken by a number of British groups, in
particular from the Geography Department at Exeter
University (Caseldine and Cullingford 1981; Caseldine
1983, 1985). It is some of the results from the latest of
these visits, in 1983, that are presented here. At Gljúfur-
árjökull work was concentrated initially on resurveying
the glacier margin at the snout and dating, by the use of
lichenometry, a ridge found immediately outside the
main ridge system. This ridge was therefore outside the
margin previously identified as being of Little Ice Age
date. In order to evaluate the use of lichenometry as a
dating technique in the area a number of permanent
lichen sites were also established to begin direct
observation of lichen growth rates. Finally a detailed
examination and survey was undertaken of a feature
that appeared to be associated with a burst of water in
the ice-marginal zone. The relative freshness of this
ephemeral landform meant that much of the available
time at the glacier was concentrated on the description
and accurate mapping of what could be traced during
the period of survey.
ICE MARGIN SURVEY
Survey of the glacier margin in the snout area foll-
owed the same methods as those previously used in 1979
and 1981 (Caseldine and Cullingford 1981; Caseldine
1983) utilising the network of survey stations already
established in the valley. The persistence of a heavy
snow cover, heavier than that found in either July 1979
or July 1981, meant that many stations were not visible
and this, coupled with the concentration on other sur-
vey work, only enabled a small part of the margin to be
surveyed, with too few observations of ice altitudes to
allow for a recontouring of the ice surface. Neverthe-
less, the survey does show that Gljúfurárjökull has
continued to advance since 1981, extending some 25 m
further down valley (Fig. 1). The rate of advance has
slowed and between 1981 and 1983 was only 12.5 m/yr,
compared with up to 25 m/yr between 1977 and 1979,
and 15 m/yr between 1979 and 1981. A search for
stations previously set up on the ice was hampered by
thick snow but at least one station was no longer in
place, remains of a cairn being found in the crevassed
area of the western margin of the glacier. Of the remain-
ing stations, station IV in the middle of the glacier was
probably quite deeply buried and III was located but
could not be accurately surveyed from the available
stations.
MORAINE CHRONOLOGY
Using a iichen curve derived from abandoned farm-
steads in Skíðadalur, Caseldine (1983) has presented a
chronology for the post-Little Ice Age pattern of
JÖKULL 35. ÁR 61