Marzena Kaczmarska MSc
Norwegian Polar Institute, Tromsø, Norway
The following report details part of work on Isfallsglaciären, between 6.09.2000 to 13.09.2000 as part of the European Union funded Field Glaciology Course at Tarfala Research Station. Members of the course carried out several different glaciological projects partly supervised by staff of the station.
Introduction
Changes of glacier front position are most of all a result of glacier ice flow, mass balance and bed morphology. Actual measurements of glacier front positions in the Tarfala valley were initiated in 1897. Although number of measurements conducted before 1945 were few. During the Holocene several glacier advances and front retreats were noticed and measured. Historic information about glacier fluctuations in the Kebnekaise and Sarek National Park areas were collected by Karlen (1973) and Karlen and Denton (1975).
Field investigation and study site
Isfallsgläciaren is a polythermal land-based glacier. It is located in the Kebnekaise mountain area, in northern Sweden, between 1185 and 1750 m a.s.l. (Fig. 1). Its area is 1,32 km2, length 2,1 km and volume ab. 0,09 km3. The average depth is 72 m but in several places reaches thickness of 220 m (Holmlund et al., 1996). The snout is divided into two sections by an outcrop of rock called Nunataken and a moraine ridge. In the period 1910-1989 glacier reatreated ab. 550 m. The retreat was followed by a small advance. Between 1989 and 1994 glacier front moved forward for ab. 15 m.
Table 1. Glacier front changes in Kebnekaise area in m/year (Holmlund,
1993).
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Changes of the front position from 1990 to 1997 were not significant. The only exception is the southern part of the front which retreated ab. 100 m in that period of time (Fig. 2).
First velocity studies were carried out on the lower parts of the glacier in 1968-69 by Jonsson (1970). A maximum speed of 0,04 m/d (expressed as a yearly average) was recorded close to the equilibrium line, while the speed of 0,01 m/d was measured at the front. Although during summer seasons 1968 and 1969 the velocity of ice was approximately 5-10 times higher than mean annual speed of ice flow (Jonsson, 1973).
The new velocity stakes net was established in July 2000. Positions of the stakes were measured by L.Orbring (unpubl. data) on 1st August and these data are available. Bad weather conditions and technical problems allowed only for one full day of measurements during the glaciology course on the Isfallsglaciären in September 2000. The position of 20 velocity stakes (Fig. 3) were measured using the Global Positioning System. At each stake the position had been recording for app. 2 minutes. The front position was measured continuously along the glacier front edge. Raw data had been processed and transformed into WGS84 coordinates system by dr. J. Moore. Transformed data were used to calculate rate of movement of each measured stake and then calculating of the average surface ice velocity was done. Positions of the stakes were marked on the map as well as the ice front margin (Fig. 3).
Results
Within the 42 days in the ablation period mean rate of movement of velocity stakes was app. 2,04 m. Mean ice flow velocity was 0,05 m/d (Table 2).
Table 2. Rate of movement (X) and ice flow velocity (Vg) on the Isfallsglaciären,
1.8-12.9.2000.
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The most significant changes of movement were registered for stakes located in a crevassed southern frontal part of the glacier. The steepness of the frontal part of the glacier seems to be the most important factor that steers velocity of ice.
The position of the glacier front was also measured. Since 1990 northern front advanced slightly about 10 m, but in the same time southern part of the glacier snout retreated for 5-15 m (Fig. 3). The southernmost end of the front of Isfallsglaciären got separated from the rest of the glacier ice and is slowly shrinking.
Conclusions
Isfallsglaciären is in many ways very similar to other Kebnekaise glaciers. Mean surface velocity of the glacier during summer is almost the same as for Storglaciären (0,05 m/d). Also changes of the front position might be seen as representative for the region. Part of the front retreats while the rest slightly advances however the rate of advance/recession is not significant. The surface velocity of the ice flow measured in summer 2000 is almost the same as it was registered by Jonsson more than 30 years ago. Jonsson’s research (1973) suggest strong correlation between summer ice speed, rate of ablation and high air temperatures in May and June. The result is increasing amount of melt water in the bottom of the glacier which causes higher than average velocity of ice.
References
Holmlund, P., 1993: Surveys of post-Little Ice Age glacier fluctuations in northern Sweden /In:/
Zeitschrift fur Gletscherkunde und Glazialgeologie, 29 (19), p. 1-13.
Holmlund, P., Karlen, W., Grudd, H., 1996: fifty years of mass balance and glacier front
Isfallsglaciären, northern Sweden /In:/ Geogr. Ann.,55(A), p.64-68.
Karlen, W., 1973: Holocene glacier and climatic variations, Kebnekaise mountains, Swedish
Lappland /In:/ Geografiska Ann., 55A (1), p. 29-63.
Karlen, W., Danton, G.H., 1975: Holocene glacier variations in Sarek National Park, northern
Sweden /In:/ Boreas, 5, p.25-56.
Orbring, L., unpubl. data.
