The Rapid Retreat of Jakobshavns Isbræ, West Greenland: Field Observations of 2005 and Structural Analysis of its Evolution
- 79 Downloads
Jakobshavns Isbræ in West Greenland (terminus at ≈69° 10′ N/50° W), a major outlet glacier of the Greenland Ice Sheet and a continuously fast-moving ice stream, has long been the fastest moving and one of the most productive glaciers on Earth. It had been moving continuously at speeds of over 20 m/day with a stable front position throughout most of the latter half of the twentieth century, except for relatively small seasonal changes. In 2002, the ice stream apparently suddenly entered a phase of rapid retreat. The ice front started to break up, the floating tongue disintegrated, and the production of icebergs increased. In July 2005, we conducted an extensive aerial survey of Jakobshavns Isbræ to measure and document the present state of retreat compared to our previous field observations since 1996. We use an approach that combines structural analysis of deformation features with continuum mechanics to assess the kinematics and dynamics of glaciers, based on aerial imagery, satellite data and GPS measurements. Results from interpretation of ERS-SAR and ASTER data from 1995 to 2005 in combination with aerial imagery from 1996 to 2005 shed light on the question of changes versus stability and their causes in the Jakobshavns Isbræ dynamical system. The recently observed retreat of Jakobshavns Isbræ is attributed to climatic warming, rather than to an inherent change in the glaciodynamic system. Close to the retreating front, deformation structures are characteristic of extension and disintegration. Deformation provinces that do not border the retreating front have had the same deformation characteristics throughout the past decade (1996–2005).
KeywordsStructural geology structural glaciology fast-moving glaciers Greenland glaciology satellite data SAR data ASTER data
We would like to thank our pilots Dr. med. Thomas Rose (private), Jan Wilken and Egon Dietz (Grønlandsfly) and Bo Isaaksen (Air Alpha) for excellent survey flights, Monika Stauber, Oliver Zahner and Marion Stellmes, Geomathematik Universität Trier, and Steven Sucht, CIRES, University of Colorado, for assistance with acquisition and processing of the 1995–1999 ERS SAR data, Koni Steffen, CIRES, University of Colorado, for acquisition of the raw ASTER data from 2003, and to Ralf Greve for helpful suggestions on the manuscript. Support provided by Deutsche Forschungsgemeinschaft (grants He 1547/4, He1547/8 and Ma2486/1) and through a CIRES Visitor Fellowship (UCH) is gratefully acknowledged.
- Abdalati W., Manizade S., Golder J., Thomas R. H., Krabill W., Csatho B. (2003) Recent increase in flow rates of the Jakobshavn Isbræ, Greenland. Eos Trans. Am. Geophys. Union, 84(46 Suppl.):F370Google Scholar
- Bennike, O., Mikkelsen, N., Klinge Pedersen, H., and Weidick, A., eds., 2004, Ilulissat Icefjord. Geological Survey of Denmark and Greenland (GEUS), Copenhagen, 116 ppGoogle Scholar
- Echelmeyer K., Clarke T. S., Harrison W. D. (1991) Surficial glaciology of Jakobshavns Isbræ, West Greenland: Part i. Surface morphology. J. Glaciol. 37(127):368–382Google Scholar
- Echelmeyer K., Harrison W. D. (1990) Jakobshavns Isbræ, West Greenland: seasonal variations in velocity—or lack thereof. J. Glaciol. 36:82–88Google Scholar
- Herzfeld, U. C., 1998, The 1993–1995 surge of Bering Glacier (Alaska)—a photographic documentation of crevasse patterns and environmental changes. Trierer Geograph. Studien 17: 211 pp, Geograph. Gesellschaft Trier and Fachbereich VI—Geographie/Geowissenschaften, Universität Trier, TrierGoogle Scholar
- Herzfeld, U. C., Box, J. E., Steffen, K., Mayer, H., Caine, N., and Losleben, M. V., 2006, A case study on the influence of snow and ice surface roughness on melt energy: Zeitschrift Gletscherkunde Glazialgeol, v. 39 (2003/2004, printed 2006), p. 1–42.Google Scholar
- Herzfeld U. C., Mayer H. (1997) Surge of Bering Glacier and Bagley Ice Field, Alaska: an update to August 1995 and an interpretation of brittle-deformation patterns. J. Glaciol. 43(145):427–434Google Scholar
- Herzfeld U. C., Mayer H., Feller W., Mimler M. (1999) Glacier roughness surveys of Jakobshavns Isbrae Drainage Basin, West Greenland, and morphological characterization. Zeitschrift für Gletscherkunde und Glazialgeologie 35(2):117–146Google Scholar
- Hollin J. T. (1962) On the glacial history of Antarctica. J.Glaciol. 4(32):173–195Google Scholar
- Luckman, A., and Murray, T. (2005) Seasonal variation in velocity before retreat of Jakobshavn Isbræ, Greenland: Geophys. Res. Lett. 32, L08501. doi: 10.1029/2005GL022519.
- Mayer, H. and Herzfeld, U. C., 2001, A structural segmentation, kinematic analysis and dynamic interpretation of Jakobshavns Isbræ, West Greenland: Zeitschrift für Gletscherkunde und Glazialgeologie, v. 37, no. 2, (2001, printed 2002), p. 107–123.Google Scholar
- Muszynski I., Birchfield G. E. (1987) A coupled marine ice stream—ice shelf model. J. Glaciol. 33:3–15Google Scholar
- Pelto M. S., Hughes T. J., Brecher H. H. (1989) Equilibrium state of Jakobshavns Isbræ, West Greenland. Ann. Glaciol. 12:127–131Google Scholar
- Thomas R. H. (1977) Calving bay dynamics and ice sheet retreat up the St. Lawrence valley system. Geogr. Phys. Quat. 31:167–177Google Scholar
- Vandrekort Nordgrønland, Ilulissat, Scale 1:100000, contour interval 25 m, 1995/96, Compukort, Denmark.Google Scholar