The Cryosphere Discussions www.the-cryosphere-discuss.net 1994-0432 1994-0440 4 1 2010 10.5194/tcd-4-163-2010 http://www.the-cryosphere-discuss.net/4/163/2010/ http://www.the-cryosphere-discuss.net/4/163/2010/tcd-4-163-2010.html http://www.the-cryosphere-discuss.net/4/163/2010/tcd-4-163-2010.pdf 163 181 2010-02-11 An explanation for the dark region in the western melt zone of the Greenland ice sheet I. G. M. Wientjes i.g.m.wientjes@uu.nl J. Oerlemans Institute for Marine and Atmospheric Research (IMAU), Utrecht University, Utrecht, The Netherlands The western part of the Greenland ice sheet contains a region that is darker than the surrounding ice. This feature has been analysed with the help of MODIS images. The dark region appears every year during the summer season and can always be found at the same location, which makes meltwater unlikely as the only source for the low albedos. Spectral information indicates that the ice in this region contains more debris than the ice closer to the margin. An ASTER image reveals wavy patterns in the darker ice. Based on these findings we conclude that ice, containing dust from colder periods, is presently outcropping near the margin, leading to albedos lower than observed for the remaining ablation area. Therefore it can be concluded that the accumulation of melt water is a result rather than a cause of the darkening. Ambach, W.: Zur Schätzung der Eis-Nettoablation im Randgebiet des Grönländischen \mboxInlandeises, Polarforschung, 42, 18–23, 1972. Bøggild, C E., Oerter, H., and Tukiainen, T.: Increased ablation of Wisconsin ice in eastern north Greenland: observations and modelling, Ann. Glaciol., 23, 144–148, 1996. Braithwaite, R J. and Olesen, O B.: Seasonal variation of ice ablation at the margin of the Greenland ice sheet and its sensitivity to climate change, Qamanârssûp sermia, West Greenland, J. Glaciol., 39, 267–274, 1993. Greuell, W.: Melt-water accumulation on the surface of the Greenland ice sheet: effect on albedo and mass balance, Geogr. Ann. A, 82, 489–498, 2000. Greuell, W. and Knap, W H.: Remote sensing of the albedo and detection of the slush line on the Greenland ice sheet, J. Geophys. Res., 105, 15567–15576, 2000. Knap, W H. and Oerlemans, J.: The surface albedo of the Greenland ice sheet: satellite-derived and in situ measurements in the Søndre Strømfjord area during the 1991 melt season, J. Glaciol., 42, 364–374, 1996. Oerlemans, J. and Vugts, H F.: A meteorological experiment in the melting zone of the Greenland ice sheet, Bull. Am. Meteorol. Soc., 74, 355–365, 1993. Petrenko, V V., Severinghaus, J P., Brook, E J., Reeh, N., and Schaefer, H.: Gas records from the West Greenland ice margin covering the Last Glacial Termination: a horizontal ice core, Quat. Sci. Rev., 25, 865–875, 2005. Reeh, N., Thomsen, H H., and Clausen, H B.: The Greenland ice-sheet margin – a mine of ice for paleo-environmental studies, Palaeogeogr., Palaeoclimatol., Palaeocol., 58, 229–234, 1987. Reeh, N., Oerter, H., and Thomsen, H H.: Comparison between Greenland ice-margin and ice-core oxygen-18 records, Ann. Glaciol., 35, 136–144, 2002. Ruth, U., Wagenbach, D., Steffensen, J P., and Bigler, M.: Continuous record of microparticle concentration and size distribution in the central Greenland NGRIP ice core during the last glacial period, J. Geophys. Res., 108, 4098, \doi10.1029/2002JD002376, 2003. Takeuchi, N., Kohshima, S., Shiraiwa, T., and Kubota, K.: Characteristics of cryoconite (surface dust on glaciers) and surface albedo of a Patagonian glacier, Tyndall Glacier, Southern Patagonia Icefield, Bull. Glaciol. Res., 18, 65–69, 2001. Van de Wal, R. S W.: Ice and Climate, Ph.D. thesis, IMAU, Utrecht University, 1992. Van de Wal, R. S W. and Oerlemans, J.: An energy balance model for the Greenland ice sheet, Global Planet. Change, 9, 115–131, 1994. Van den Broeke, M., Smeets, P., Ettema, J., and Munneke, P K.: Surface radiation balance in the ablation zone of the west Greenland ice sheet, J. Geophys. Res., 113, D13105, \doi10.1029/2007JD009283, 2008. Zeng, Q., Cao, M., Feng, X., Liang, F., Chen, X., and Sheng, W.: A study of spectral reflection characteristics for snow, ice and water in the north of China, in: Hydrological Applications of Remote Sesing and Remote Data Transmission, edited by Goodison, B E., IAHS, 145, 451–462, 1984. Zuo, Z. and Oerlemans, J.: Modelling albedo and specific balance of the Greenland ice sheet: calculations for the Søndre Strømfjord transect, J. Glaciol., 42, 305–317, 1996.