(NW S PITSBERGEN ) USING REMOTE SENSING DATA

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Department of Cryology and Polar Research, Institute of Geography, N. Copernicus University, Poland

Fluctuations of glacier ranges are one of the basic elements in the study of their geometry changes. The studies of the fluctuation of the glaciers in the Forlandsundet area (NW Spitsbergen) were made in three main regions: Kaffiøyra, St. Jonsfjorden and Prins Karls Forland. The investigations refer to mountain and calving type glaciers.

The main investigative aim of this article is to estimate and interpret changes of glacier ranges in the Forlandsundet area in the XX and XXI centuries by remote sensing data and field measurements.

We used ASTER ortho-images and a digital elevation model derived from 3N and 3B bands to determine the fluctuations of the glaciers. The data analysis confirmed that most of the glaciers in this area are in a recession phase (Figure 1). In the 21th century the rate of recession increased. The most quickly retreating are the calving type glaciers - Aavatsmarkbreen, Konowbreen, Osbornebreen and Dahlbreen. The front of the Aavatsmarkbreen retreated from 2000 to 2006 max. about 700 m (100 m/y). Between 2000 and 2006, the glacier area reduced by over 1.6 (km2/y). The glaciers terminating in the sea were characterized by a distinct retreat at the beginning of 21th century. The six small valley glaciers in Kaffiøyra in this period retreated several m/year. Maximum glacier front recession in the period 2000-2006 we noted on the Osbornebreen (700-800 m/y). The retreat and mass loss noted on almost all these glaciers have been observed on entire Spitsbergen. The recession (retreat and mass loss) is triggered by changes in climatic conditions. Due to various factors of the topoclimatic - geomorphologic nature, the recession has taken a diverse course with respect to particular glaciers.

Moreover in this article we present the results of soundings profiles made during the summer seasons 2004, 2005 and 2006 on chosen calving type glaciers. Based on submarine relief evidence and marginal zones we made an attempt to determine old zones of glaciers (at glacial episode 3.0-2.5 ka BP and Late Vistulian 13-10 ka BP).

One of the key issues while modelling subaqual glacial relief is the dynamics of the ice cliffs. The research carried out by Brown et al. (1982), Boulton (1986) and Jania (1986) showed that ice cliffs can undergo considerable fluctuations in short periods of time (such as a hydrological year or a balance year), irrespective of the general

of ‘using’ the masses of snow delivered in winter; it also has minimal rate of ice cliff calving. Winter advance may result in pushing glacial and fluvioglacial deposits up, thus forming annual small push moraines. It often happens that the distance between these moraines equals the mean annual recession. Accumulation of larger push moraines, both subareal and subaqual ones, is predominantly connected with intensive dynamics of movement and surge (Jania 1988).

Figure 1. The retreat of glaciers in Forlandsundet region (Spitsbergen). Numbers means the maximum recession of a front of glaciers in the period 2000-2006.

Using the forms of the sea bottom and of the land marginal zones the author tried to delimit the old ranges of the Aavatsmarkbreen and Dahlbreen. As the first results show, the subaqual relief of the sea forefield of the selected glaciers was created by pushing both glacial and marine material up by the anchored zone of a glacier which ends in the sea. In the presented profiles perpendicular to the ice cliffs forms both seasonal and multi-annual oscillations are visible. Seasonal forms (Fig. 2) are from 3 to 10 m high; their genesis is probably connected with the winter re-advance

of the ice front. Such a mechanism has already been described in the literature by Boulton (1986) and Jania (1988). Marsz (1987) states a longer stagnation of an ice cliff with an underwater bottom leads to the formation of a subaqual frontal moraine at the foot of the cliff.

Figure 2. Annually push moraines in the forefield of Aavatsmarkbreen formed between 2004 and 2001 H- height of form, W- width of form, 2004- ice cliff range in 2004.

The oldest range of Dahlbreen, recorded in the sea bottom relief, is probably connected with the glacial episode of 3.0-2.5 ka BP. It is, however, smaller than the one delimited by Szupryczyński (1983). A trace of the Little Ice Age is clearly visible in the bottom relief. It corresponds with the deposits of that age left on the land (Grześ et al. 2007, Lankauf 2002). Morphogenetic analysis of the subaqual forms of the sea bottoms where the studied glaciers end needs further research. However, their sequence as well as the fact that they correspond with the old ranges of glaciers proves their glacial genesis. Echo sounders’ results of the surging Aavatsmarkbreen are also interesting.

References

Boulton G.S., 1986. Push-moraines and glacier-contact fans in marine and terrestrial environments, Sedimentology, 33, 677-698.

Brown C.S., Meier M.F., Post A. 1982. Calving speed of Alaska tidewater glaciers, with application to Columbia Glacier. U.S. Geological Survey Professional Paper 1044-9612, C1-C13.

Grześ M., Król M., Sobota I. 2007. Subaqual recordings of the changes in the range of glaciers in the Forlandsundet region (NW Spitsbergen). Landform Analysis, 5, 148-150. Jania J. 1986. Dynamika czół spitsbergeńskich lodowców uchodzących do morza

(Dynamics of the Spitsbergen tidewater glaciers fronts - Engl. summary), Geographia, Studia et dissertationes, vol. 9, Uniwersytet Śląski, Katowice.

Jania J. 1988. Dynamiczne procesy glacjalne na południowym Spitsbergenie (w świetle badań fotointerpretacyjnych i fotogrametrycznych), Prace Naukowe Uniwersytetu Śląskiego w Katowicach Nr 955, Katowice. pp. 257.