Jökull - 01.10.1998, Blaðsíða 38

Previous observations on the mass balance of Vat-
najökull have been rather patchy. The first mass bal-
ance measurements on Vatnajökull were done in 1919
using tephra layers as a reference (Wadell, 1920). Dur-
ing the years 1936-39 detailed mass balance measure-
ments were undertaken on Hoffellsjökull, a southeast-
em outlet of Vatnajökull (Ahlmann and Thorarinsson,
1937a, 1937b, 1938, 1939; Ahlmann, 1937, 1939,
1940; Thorarinsson, 1939). In 1951 and 1960 the win-
ter balance was measured in a number of points all
over the ice cap (Rist, 1952, 1961). Since 1954, sys-
tematic measurements of accumulation have been
done in the Grímsvötn area in the interior of Vatna-
jökull (Bjömsson, 1985) and sporadic measurements
of accumulation and melting have been done on vari-
ous parts of the glacier. Further, mass balance mea-
surements were carried out in 1985-86 on Tungna-
árjökull, a western outlet (Björnsson, 1988). Since
1991, mass balance has been regularily monitored
along flowlines on several outlets of the ice cap
(Bjömsson and others, 1992,1995a,b).
SITE DES CRIPTION
Vatnajökull is located close to the southeastern
coast of Iceland, extending 150 km from west to east
and 100 km from south to north, 8100 km2 in area.
The ice cap contains a number of outlet glaciers
which drain several domes. The monitoring of the
mass balance, which started in 1991-1992, has been
carried out on the westem and northem outlets of the
ice cap which contain altogether about 4000 km2 or
Fig. 1. Contour map of Vatnajökull. Rivers draining the glacier, streamflow gauges operated by the National Energy Authori-
ty and the National Power Company, and meteorological stations.
- Vatnajökull, jökulár, rennslismœlar og veðurstöðvar.
36
JOKULL, No. 45, 1998