Jökull - 01.12.1983, Side 5

Satellite Glaciology of Iceland
RICHARD S. WILLIAMS, jr.
U. S. Geological Survey, Reston, VA 22092, U. S. A
ABSTRACT
The glaciers of Iceland have been studied by scientistsfor
nearly 200 years, and variations have been monitored for
about 50 years. Allhough maps of the principal glaciers
appeared in 1792 (Pálsson), 1844 (Gunnlaugsson), and
1901 (Thoroddsen), modem maps were not available until
the Danish Geodetic Survey conducted plane-table surveys
from 1904 untiljust before World War II. Several series of
modem maps prepared by using aerial photogrammetric
techniques, by the Defense Mapping Agency (U.S.) and/or
the Icelandic Geodetic Survey, have been published since
World War II. Aerial photographs of Iceland’s glaciers
wereJirst acquired in the 1930’s. Aerialphotographs of most
of Iceland have been acquired twice by the United States in
1944-45 and in 1956 and 1969-61. During this sameperiod
the Icelandic Geodetic Survey has also acquired aerial
photographs of selected areas of Iceland.
Periodic monitoring of Iceland’s glaciers, usually on an
annual basis, was begun by Eythórsson in the 1930’s. After
his death, the annual measurement of glacier variation has
been carried out by Rist. At the present time about 40
positions are measured annually, including the 34 Inter-
national Hydrological Decade (IHD) index-numbered
glacier margins. This represents about 12percent of the total
number of named and unnamed glaciers and outlet glaáers
that could be monitored annually (total about 330).
For the past lOyears (1972-82) the Landsal series of
satelliles has been imaging Iceland’s glaáers. Successive
Landsat images acquired by U.S., Canadian, and Swedish
recáving stations have provided new information about the
glaáers of Iceland and have also provided a new way of
monitoring changes in glaáer area and changes in positions
of glaáer termini and margins of ice caps. Although satellite
glaciology of Iceland is only in its infancy, the following
studies have been completed by different sáentists: glaáer
advance and recession (including surging glaáers), effect on
the glacier surface of subglaáal volcanic and geothermal
activity, effect of jökulhlaups, glaáer jlow, ablation
phenomena, and geomorphic, structural, and tectonic studies
of the subglaáal terrain. Landsat images have also been used
toproduce special image maps of Iceland’s glaciers.
INTRODUCTION
Iceland abounds in dynamic geological phenom-
ena which, for over 200 years, has attracted the
attention of geologists. Special scientific emphasis
have been directed at: (1) its geothermal areas
(especially the occurence of hot springs and
geysers), (2) its frequent volcanic activity and great
diversity of volcanic landforms, and (3) its glaciers
and the landforms produced by glacier action. It is
Iceland’s glaciers that are the subject of this paper,
including a discussion of how the rapidly develop-
ing technology of satellite remote sensing is being
used to provide a periodic and permanent record, in
image form, of changes in the following physical
characteristics of its glaciers: surface area, ice cap
margins and glacier termini, and surface features
caused by glacier flow or subglacial volcanic and
geothermal acitivity.
OCCURRENCE OF GLACIERS
Glaciers in Iceland occur principally as ice caps
or outlet glaciers from ice caps. Figure 1 is a sketch
map showing the 13 principal ice caps of Iceland.
According to published maps, books, and journal
articles there are 33 separate glaciers (geographic
place names of ice caps (not including outlet glaci-
ers) and cirque glaciers where the suffix jökull
occur) in Iceland. Most of these glacier names were
listed by Thorarinsson (1943) in his discussion of the
areas of Iceland’s glaciers. From published maps,
books, and journal articles, however, there are actu-
ally a total of 85 separately named outlet glaciers of
the 13 individual ice caps out of a potential total of
about 330 separate named and unnamed ice caps,
outlet glaciers, and other types of glaciers (mostly
cirque-type) which can be identified on maps of
Iceland at a scale of 1:100,000 or smaller. The 13
major ice caps, all ofwhose areas exceed 20 km2, are
listed in Table 1.
JÖKULL 33. ÁR 3