Jökull - 01.12.1981, Blaðsíða 97

Variations in meltwater characteristics at
Kaldalónsjökull, Iceland, 1979
JAMES D. HANSOM
Department of Geography, University of Sheffield, Sheffield, England.
DAVID ROBERTS
Deparlment of Geography, University of Aberdeen, Aberdeen, Scotland.
abstract
Dunng the summer of 1979, variations in the
glacial meltwater discharge and sediment load of the
Rwer Mórilla at Kaldalón, Vestfirdir were measured.
The following paper reports the results obtained
between 6 and 20th July, 1979 and compares them
with observations of the meteorological and ice ablation
conditions on Kaldalónsjökull over the same penod.
INTRODUCTION
The aims of this project were firstly to esta-
blish the order of magnitude of the variations
ln discharge and sediment load of the River
Mórilla, a glacial meltwater stream issuing
from the rapidly retreating glacier of Kalda-
lónsjökull. A secondary aim was to assess, as
far as was possible, the effects of glacier retreat
upon sediment transport rates.
Ehe present glacier in Kaldalón is confined
to the valley head although it is fed by
approximately 40 km2of ice draining from the
Drangajökull Ice Cap. Since 10800 BP and in
spite of several fluctuations, substantial
glacier retreat has occurred at all the outlet
glaciers of Drangajökull (John and Alexander,
1975) and this has been recorded systemati-
cally since 1931 by Eythorsson (1960),John and
Sugden, (1962), Lewis (1964) and John and Ale-
xander (1975). Such records show that Kalda-
lónsjökull has retreated some 1.1 km in 48
years (Fig. 1). Fig. 1 also shows the present
location of the glacier snout as surveyed by
autoset level in July 1979. At this time the
small rock bar noted first by Lewis (1964) and
subsequently by John and Alexander (1975) had
emerged substantially, separating the glacier
into two ice streams and threatening eventual
ice starvation of the lower snout.
METHODS
Two recording sites were established close
to the glacier snout in July 1979 (Fig. 1). The
first was a meteorological station sited at c.
305 m above sea-level on the rock bar above
the lower snout. At this station a continuous
thermohydrograph trace recorded air tem-
perature and humidity. Wind measurements
were taken daily at 1200 hrs. using a hand
held anemometer and precipitation, collected
by a c. 13 cm (5”) rain gauge, was monitored
at the same time. Ablation measurements
were taken from one line of graduated ab-
lation poles inserted into the ice surface above
the rock bar at 20 m vertical intervals up to
420 m above sea-level.
The second site was a river discharge station
established at 30 m above sea-level on the out-
wash surface close to the glacier snout (Fig. 1).
Using an OTT current meter, a cross-section
and velocity profile was derived and stage-
discharge curve plotted. River stage was sub-
sequently recorded at 0600, 1200 and 1800
hours each day. Suspended sediment concen-
tration was sampled following the method of
Hjulström (1939) and 0strem (1975). A 1-liter
plastic bottle, bunged and fitted with 1 cm
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