Field site characteristics

Midre Lovenbreen and Austre Br0ggerbreen (Fig. 1) are two small, north-facing valley glaciers located on the Br0ggerhalv0ya Peninsula, western Spitsbergen, Svalbard (78°50/ N, 12°00' E). Continuous permafrost in the area ranges in depths from 100 to 400 m (Liest0l 1977). The geology of the peninsula is complex, but Caledonian age metamorphic rocks (phyllite and schists) exist virtually throughout the glacierized basins, with some overlying sedimentary rocks (sandstones and carbonates) occurring, more so at Austre Br0ggerb-reen (Hjelle 1993; Hodson et al 2000). The glaciers extend from c. 50 m to c. 600 m above sea level (a.s.l.), both being of maximum thicknesses < 180 m with an ELA c. 400 m a.s.l. Both glaciers have been characterized by negative mass balances since the end of the Little Ice Age (Hagen & Liest0l 1990; Lefaucon-nier & Hagen 1990).

The 6.1 km2 Austre Br0ggerbreen catchment is now thought to be entirely cold-based (cf. Hodson et al 1998b; Hodson & Ferguson 1999). As a result, meltwater drainage is primarily routed sub-aerially in marginal and supraglacial channels. There is a well-developed englacial system (Hagen et al 1991; Hodson et al 2002) that appears to emerge close to the glacier surface on the eastern margin. Midre Lovenbreen, covering an area of 5.5 km2, is polythermal, with a temperate ice core and cold margins (Bjornsson et al 1996). The temperate ice zone is in the accumulation and upper ablation areas (Bjornsson et al 1996; Rippin et al 2003). Summer meltwater is only partly drained supraglacially, with a subglacial system discharging significant quantities of water to the proglacial region. Annually, this subglacial system emerges at the snout of the glacier as a turbid artesian upwelling (Hodson et al 2000), indicating the temporary storage and enhanced water pressure at the glacier bed prior to the hydrological breach of the cold margin.

The south-facing Glacier B28 (Inland Waters Branch 1969), unofficially named 'Stagnation Glacier' (72°58' N 78°22' W), is located on the south side of Bylot Island, Nunavut (Fig. 1). Moorman and Michel (2000b) suggested that the 14.0 km2 Stagnation Glacier is polythermal. Aerial imagery between 1948 and 1994 suggests Stagnation Glacier has been retreating at c. 26 m/a, while observations since 1999 indicate that retreat has slowed to approximately 5 m/a. The glacier snout is at c. 320 m a.s.l., and the ELA is at c. 1050 m a.s.l. The basin's geology is primarily Archean igneous and metamorphic

Austre Braggerbreen arid Midre Lovénbreen. Svalbarü

Austre Braggerbreen Midre Lovénbreen Key:

---Moraine * Subglacial upwelling

- Proglaciai stream ° AWS

EEmi Glacier ice 3fi Gauging station

Austre Braggerbreen Midre Lovénbreen Key:

---Moraine * Subglacial upwelling

- Proglaciai stream ° AWS

EEmi Glacier ice 3fi Gauging station

Austre Braggerbreen arid Midre Lovénbreen. Svalbarü

Stagnation Glacier

Fig. 1. Location map showing study sites and sketch maps of the three glacier basins rocks (Jackson et al 1975), and local continuous permafrost depths reach a maximum of c. 400 m (Moorman & Michel, 2000a). Subaerial hydrology dominates Stagnation Glacier; marginal channels and deeply incised supraglacial channels are the principal drainage routes. Temporary vertical displacement of the glacier was recorded in 2000, possibly indicative of transient subglacial water storage. Dye trace experiments in 2001 and 2002 suggest the existence of en- and/or subglacial drainage.

Because Austre Br0ggerbreen is a cold-based glacier, no 'winter runoff' occurs. At the two polythermal glaciers, Midre Lovenbreen and Stagnation Glacier, winter runoff enables naled icing forms to develop. At both glaciers, icings extend up to 500 m from the snout, occupying proglaciai topographic depressions.

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