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Southwestern Disko Island, central West Greenland (70oN). Positions given in UTM-coordinates for each rock glacier in data set. The data set includes observations on talus-derived rock glaciers, glacier-derived rock glaciers and large ice-cored moraines.
Period of investigation: 1983-1997
Principal investigator: Ole Humlum
Institute of Geography
University of Copenhagen
Oester Voldgade 10
DK 1350 Copenhagen K
Telephone: +45 3532 2500
Fax: +45 3532 2501
Disko Island (8600 km2) is situated west of central mainland Greenland. The island is part of the Tertiary volcanic province of West Greenland and is mainly made up by lavas. The landscape is a plateau basalt landscape with cirque carved lava plateaus and U-shaped valleys and fjords. Rock glaciers are frequent in Disko Island (Humlum, 1982). In southern Disko Island, about 60 km SSE of the two study sites, meteorological observations have been carried out since 1923 in the village of Godhavn. The present (1961-1990) mean annual air temperature is -3.9C, the coldest month is March (-15.1C), and July is the warmest month (7.1C). The mean annual precipitation at Godhavn is about 400 mm water equivalent. Most of the precipitation (75 %) usually falls during the period June to December, associated with advection of moist, maritime air masses from the south and southwest along the Davis Strait. The remaining part of the year is comparatively dry, as it is dominated by cold and dry katabatic air masses flowing of f the Greenland Ice Sheet to the east. Approximately 60-70 % of the mean annual precipitation is snow and in Godhavn a persistent snow cover is registered from late September to late May.
No systematic mapping of permafrost or permafrost related terrain features have been carried out in this part of West Greenland. Weidick (1968), however, places Disko Island within the zone of continuous permafrost. This is supported by the occurrence of open system pingos (Christiansen, 1995) and numerous rock glaciers (Humlum, 1982, 1984, 1988a, 1988b, 1996; Humlum et al., 1995; Rasch et al. 1996), which are geomorphic indications of the presence of widespread permafrost in Disko Island. Adopting a standard continental geothermal gradient of about 0.033C m-1, the mean annual air temperature of -7.5C (1991-96) indicates a potential permafrost thickness of about 175-225 m. This estimate is presumably somewhat conservative, as the Little Ice Age annual air temperature presumably was about 2C below modern values (Humlum, 1996), which would provide conditions for a somewhat thicker permafrost layer than is suggested by modern meteorological values. The high frequency of rock glaciers on Disko Island is presumably derived from high rock weathering rates (Humlum, 1992).
Christiansen, H.H. 1995. Observations of Open System Pingos in a Marsh Environment, Mellemfjord, Disko, Central West Greenland. Danish Journal of Geography, 95, 42-48.
Hansen, B.U.; Humlum, O; Nielsen, N.; Rasch, M. and Funch, P. 1997: Meteorological Observations in 1996 at the Arctic Station, Qeqertarsuaq (Godhavn), Central West Greenland. Danish Journal of Geography, Vol.97, 152-153.
Humlum, O. 1982. Rock glacier types on Disko, central West Greenland, Geografisk Tidsskrift, 82, 59-66.
Humlum, O. 1984. Altitudinal trends of talus-derived lobate rock glaciers on Disko, central West Greenland, XXV. International Geographical Congress, Royal Danish Geographical Society, Occasional Papers, 7, 35-39.
Humlum, O. 1987. Glacier behaviour and the influence of upper-air conditions during the Little Ice Age in Disko, central West Greenland. Danish Journal of Geography, 87, 1-12.
Humlum, O. 1988a. Rock glacier appearance level and rock glacier initiation line altitude: a methodological approach to the study of rock glaciers, Arctic and Alpine Research, 20, 160-178.
Humlum, O. 1988b. Natural cairns on rock glaciers as an indication of a solid ice core, Geografisk Tidsskrift, 88, 78-82.
Humlum, O. 1992. Observations on Rock Moisture Variability in Gneiss and Basalt under Natural, Arctic Conditions. Geografiska Annaler, 74A, 197-205.
Humlum, O. 1996. Origin of Rock Glaciers: Observations from Mellemfjord, Disko Island, central West Greenland, Permafrost and Periglacial Processes, 7, 361-380.
Humlum, O. 1997. Active Layer Thermal Regime at three Rock Glaciers in Greenland. Permafrost and Periglacial Processes, Vol.8, p. 383-408.
Humlum, O., Christiansen, H.H., Hansen, B.U., Hasholt, B., Jakobsen, B.H., Nielsen, N. and Rasch, M. 1995. Holocene Landscape Evolution in the Mellemfjord Area, Disko Island, Central West Greenland: Area Presentation and Preliminary Results. Danish Journal of Geography, 95, 28-41.
Humlum, O.; Nielsen, N. and Hansen, B.U. 1996: Meteorological Observations in 1995 at the Arctic Station, Qeqertarsuaq (Godhavn), Central West Greenland. Danish Journal of Geography, 96:119-122.
Nielsen, N.; Humlum, O.; Hansen, B.U.; and M. Rasch. 1995: Meteorological observations at Arctic Station, Qeqertarsuaq (Godhavn), Central West Greenland. Danish Journal of Geography, 95:97-104.
Rasch, M. and Nielsen, N., 1994: Holocene relative sea-level changes indicated by morphostratigraphic sequences; Signifik, Disko Island, West Greenland. Danish Journal of Geography, 94: 37-45.
Rasch, M. and Nielsen, N., 1995: Coastal morpho-stratigraphy and Holocene relative sea level changes at Tuapaat, southeastern Disko Island, central West Greenland. Polar Research, 14: 277-289.
Rasch, M., Christiansen, H.H., Hansen, B.U., Hasholt, B., Humlum, O., Jakobsen, B.H. and Nielsen, N. 1996. Greenland Landscape Elements as Indicators of Rapid Environmental Change. In: Geoindicators: Assessing Rapid Environmental Changes in Earth Systems, Berger, A.R. & Iams, W.J. (eds.) Balkema Publishers, Holland, p. 69-92.
Weidick, A. 1968. Observations on some Holocene glacier fluctuations in West Greenland. Meddelelser om Groenland, 164(6), 202p.
Humlum, O. 1998. Rock glaciers, Disko Island, Greenland. In: International Permafrost Association, Data and Information Working Group, comp. Circumpolar Active-Layer Permafrost System (CAPS), version 1.0. CD-ROM available from National Snow and Ice Data Center, email@example.com. Boulder, Colorado: NSIDC, University of Colorado at Boulder.