Introduction and Rationale

The aim of this contribution is to describe the landform-sediment assemblages at the margins of polythermal glaciers in Svalbard and to present a landsystem model for terrestrially-based glaciers in this maritime high-arctic setting. The discussion is restricted principally to non-surge-type glaciers as the landform-sediment assemblages at surge-type glaciers are considered in a separate chapter (Evans and Rea, Chapter 11). The structural glaciological controls on landform development are described, together with the dominant landform types and their sedimentary facies.

The Svalbard archipelago (77°N to 80°N) lies at the northern extent of the Norwegian Current, a branch of the Gulf Stream, and enjoys a climate that is relatively mild and moist for its northern latitude. On the western coast the average annual temperature is —6 °C, the average temperature of the warmest month (July) is +5 °C, and in the coldest month (January) it is -15 °C. Although there are contrasts between the maritime west coast and the interior, precipitation in Svalbard at sea level varies typically from 400 to 600 mm annually. Orographic effects increase precipitation in the highland regions, but even on the glaciers snowfall of more than 2-4 m is rare (Hagen et al., 1993). Ice-free land areas are underlain by permafrost to depths of between 100 and 460 m (Hjelle, 1993).

The archipelago is 60 per cent glacierized, the largest volumes of ice being accounted for by the highland ice fields and ice caps of northwestern, northeastern and southern Spitsbergen and Nordaustlandet (Fig. 4.1). These ice masses cover the highland areas, and their outlets are divided into individual glaciers by mountain ridges and nunataks. Many glaciers reach the sea, forming wide calving fronts. Smaller cirque glaciers are also common, particularly in the more alpine terrain of western Svalbard (Fig. 4.2). Many of the larger glaciers in Svalbard are polythermal, with extensive areas of temperate ice in the accumulation area, but with their termini frozen to the bed (Hagen and Saetrang, 1991; Hagen et al., 1991; Odegard et al, 1992; Bjornsson et al, 1996). Most of the smaller cirque glaciers are probably cold-based throughout. The hydrology of polythermal glaciers is poorly understood compared with alpine glaciers (Bamber, 1989; Hagen

Esker Diagram
Figure 4.1 The Svalbard archipelago, showing location of glaciers mentioned in text.

and Saetrang, 1991; Hagen et al., 1991; Vatne et al., 1996), although recent advances have been made in this field (Hodgkins, 1997).

Until recently, the relationship between ice structure and debris distribution in polythermal glaciers was poorly understood in comparison with temperate glaciers (Weertman, 1961; Swinzow, 1962; Boulton, 1970, 1972b, 1978; Hooke, 1973a; Clapperton, 1975; Hambrey and

Figure 4.2 Norsk Polarinstitutt vertical aerial photograph S90-6526 of Br0ggerhalv0ya, on the southern side of Kongsfjorden in northwest Spitsbergen. Valley glaciers shown are (from left to right): Vestre Lovenbreen, Midtre Lovenbreen, Austre Lovenbreen, Pedersenbreen and Botnfjellbreen. These glaciers are typical of many Svalbard valley glaciers, with multiple accumulation basins feeding a single glacier tongue. The snout of Kongsvegen is just visible at the head of Kongsfjorden, in the lower right of the photograph. The large glacier at the bottom of the photograph is Uversbreen.

Figure 4.2 Norsk Polarinstitutt vertical aerial photograph S90-6526 of Br0ggerhalv0ya, on the southern side of Kongsfjorden in northwest Spitsbergen. Valley glaciers shown are (from left to right): Vestre Lovenbreen, Midtre Lovenbreen, Austre Lovenbreen, Pedersenbreen and Botnfjellbreen. These glaciers are typical of many Svalbard valley glaciers, with multiple accumulation basins feeding a single glacier tongue. The snout of Kongsvegen is just visible at the head of Kongsfjorden, in the lower right of the photograph. The large glacier at the bottom of the photograph is Uversbreen.

Müller, 1978). Recent studies have clarified this relationship, confirming the importance of thrusting in elevating basal debris within polythermal glaciers (Hambrey and Huddart, 1995; Bennett et al., 1996a and b; Hambrey et al., 1996; Murray et al., 1997). These studies have also highlighted the significance of folding of debris-rich stratification in re-organizing both supraglacial, basal and glacifluvial debris (Hambrey and Dowdeswell, 1997; Glasser et al., 1998a, 1999; Hambrey et al., 1999; Glasser and Hambrey, 2001a and b).

Estimates of the percentage of surge-type glaciers in Svalbard range from 13 per cent (Jiskoot et al., 1998, 2000), to 35 per cent (Hamilton and Dowdeswell, 1996), and even as high as 90 per cent (Lefauconnier and Hagen, 1991). These glaciers are prone to dramatic increases in velocity and rapid frontal advances, followed by periods of quiescence during which velocities are generally low. Surge-type glaciers in Svalbard typically have relatively long quiescent phases between surge events (Dowdeswell et al., 1991). Surges have been documented at numerous Svalbard glaciers including Usherbreen (Hagen, 1987, 1988), Bakaninbreen (Murray et al., 1997), the Kongsvegen/Kronebreen tidewater complex (Melvold and Hagen, 1998; Bennett et al., 1999), Seftstrembreen (Boulton et al., 1996), Holmstrombreen (Boulton et al., 1999), Brasvellbreen (Solheim and Pfirman, 1985) and Fridtjovbreen (Glasser et al., 1998b; see Fig. 4.1 for locations of glaciers).

Most glaciers in Svalbard are currently receding from their Neoglacial maxima, achieved circa 1890—1900 (Fig. 4.3). Mass-balance measurements have been made at two Svalbard glaciers, Austre Breggerbreen and Midtre Lovenbreen, since the 1960s (Hagen and Liestel, 1990; Lefauconnier et al., 1999). Statistical analysis of these records and of associated climatic data suggests that the net mass balance of these glaciers has been negative in the majority of years since 1900 (Lefauconnier and Hagen, 1990). Consequently, most glaciers terminating on land in Svalbard have receded 1—2 km since that time (Hagen et al., 1993). Volume losses since 1900 have been substantial, possibly as much as 33 per cent, based on former ice-marginal positions and trim lines. Historical and photographic records show that, at the Neoglacial maximum, many Svalbard glaciers had near-vertical fronts with thick debris layers (Liestel, 1988). This trend of overall recession means that many Svalbard glaciers have extensive zones of exposed sediments and landforms between their Neoglacial maxima and current snouts

Midtre Lovenbreen Glacier

Figure 4.3 Norsk Polarinstitutt vertical aerial photograph S90-5788 of Midtre Lovenbreen (left) and Austre Lovenbreen (right) showing the recent (post c. 1890) recession of these two valley glaciers. Both have a prominent outer moraine ridge, within which are moraine-mound complexes, glacifluvial facies and linear debris stripes composed of supraglacial debris.

Figure 4.3 Norsk Polarinstitutt vertical aerial photograph S90-5788 of Midtre Lovenbreen (left) and Austre Lovenbreen (right) showing the recent (post c. 1890) recession of these two valley glaciers. Both have a prominent outer moraine ridge, within which are moraine-mound complexes, glacifluvial facies and linear debris stripes composed of supraglacial debris.

Figure 4.4 Part of Norsk Polarinstitutt vertical aerial photograph S95-I087 of Austre Br0ggerbreen. Although heavily modified by glacifluvial activity and partly flooded by proglacial lakes, linear debris stripes are still a strong component of the landform-sediment assemblage at Austre Br0ggerbreen.

Figure 4.4 Part of Norsk Polarinstitutt vertical aerial photograph S95-I087 of Austre Br0ggerbreen. Although heavily modified by glacifluvial activity and partly flooded by proglacial lakes, linear debris stripes are still a strong component of the landform-sediment assemblage at Austre Br0ggerbreen.

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