Introduction

Glacier surging is one of the most fascinating and enigmatic topics in glaciological research. When glacier surging suddenly triggers, the glacier becomes heavily crevassed and in most cases the glacier terminus rapidly advances. The short dramatic active phase is followed by a long quiescent phase, where the glacier terminus undergoes thinning and recession while the accumulation area regains in mass before the next surge event occurs. This cyclic behaviour superimposes any climatic variations. Hence, it is very important to identify surge-type glaciers in order to exclude them in attempts to relate glacier terminus fluctuations to climate change.

Although research on glacier surging has been in progress for more than 50 years, it is still unclear why some glaciers surge while adjacent glaciers do not and what exactly triggers and terminates surge events. There seems to be consensus in the glaciological community in that several mechanics may lead glacier surging (e.g. Murray et al., 2003).

Also, surge-type glaciers appear as a regional phenomenon in many glacierized areas, while they are almost absent in other regions. In recent years, a number of papers have identified surge-type glaciers in regions such as Iceland (Thorarinsson, 1969; Bjornsson et al. 2003), Svalbard (Hagen, 1988; Hagen et al., 1993; Dowdeswell et al., 1995; Hamilton and Dowdeswell, 1996; Jiskoot et al., 1998, 2000), Russian High Arctic (Dowdeswell and Williams, 1997), Caucasus (Dolgoushin and Osipova, 1975), Pamirs (Dolgoushin and Osipova, 1975), Tien-Shan (Dolgoushin and Osipova, 1975), Karakoram Himalaya (Barrand and Murray, 2006), Kamchatka (Dolgoushin and Osipova, 1975), Alaska-Yukon (Post, 1969; Clarke et al., 1986), Canadian High Arctic (Copland et al., 2003), and East Greenland (Jiskoot et al., 2003).

This paper follows this line of research and presents the results of a systematic examination of the incidence of surge-type glaciers on Disko Island, West Greenland. These surge-type glaciers constitute together with surge-type glaciers on Nuussuaq Peninsula, situated north of Disko Island, the Disko-Nuussuaq surge cluster. At present, only two glaciers (glacier 1IA02034 and glacier 1IB26003) on Nuussuaq Peninsula are categorized as surge-type glaciers (Weidick, 1988; Weidick et al., 1992), but a thorough examination is likely to reveal more. The current literature categorizes 24 glaciers on Disko Island as surge-type glaciers, and only four of these have been observed during their active surge phase (Weidick, 1988; Weidick et al., 1992; Gilbert et al., 2002).

In Greenland two surge clusters have been recognized; the East Greenland surge cluster and the Disko-Nuussuaq surge cluster. Both surge clusters are mainly situated in basaltic provinces. The East Greenland surge cluster comprises 71 surge-type glaciers and is the best described (Rucklidge, 1966; Henriksen and Watt, 1968; Olesen and Reeh, 1969; Rutishauser, 1971; Colvill, 1984; Weidick, 1988; Jiskoot et al., 2001, 2003; Murray et al., 2002; Woodward et al., 2002; Pritchard et al., 2003). In addition, surge events have been reported on outlet glaciers in South Greenland (Weidick, 1984a,b), Northwest Greenland (Mock, 1966; Rignot and Kanagaratnam, 2006), North Greenland (Higgins and Weidick, 1988) and Northeast Greenland (Reeh et al., 1994).

As only a few glaciers on Disko Island have official names, reference to specific glaciers is given to their hydrological code in the regional glacier inventory (Weidick et al., 1992).

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