The Cryosphere www.the-cryosphere.net 1994-0416 1994-0424 2 2 2008 10.5194/tc-2-147-2008 http://www.the-cryosphere.net/2/147/2008/ http://www.the-cryosphere.net/2/147/2008/tc-2-147-2008.html http://www.the-cryosphere.net/2/147/2008/tc-2-147-2008.pdf 147 157 2008-11-13 The equilibrium flow and mass balance of the Taku Glacier, Alaska 1950–2006 M. S. Pelto mspelto@nichols.edu M. M. Miller G. W. Adema M. J. Beedle S. R. McGee K. F. Sprenke M. Lang Nichols College Dudley, MA 01571, USA Glaciological and Arctic Sciences Institute, University of Idaho, Moscow ID 83843, USA Institute of Geodesy, Universitat der Bundeswehr, Werner Heisenberg Weg, 85577 Neubiberg, Germany Geography Program, University of Northern British Columbia, 3333 University Way, Prince George, B.C. V2L 2R4, Canada Denali National Park and Preserve, P.O. Box 9, Denali Park, AK 99755, USA The Taku Glacier, Alaska has advanced 7.5 km since the late nineteenth century, while all other primary outlet glaciers of the Juneau Icefield are in retreat. The Juneau Icefield Research Program has completed field work on the Taku Glacier annually since 1946. The collected observations of surface mass balance, glacier velocity and glacier thickness at Profile IV 29 km above the terminus and 4 km above the equilibrium line provide a means to assess the equilibrium nature of the Taku Glacier. Annual velocity measured and summer velocity measurements completed at a Profile IV from 1950–2006 indicate insignificant variations in velocity seasonally or from year to year. The consistency of velocity over the 56-year period indicates that in the vicinity of the equilibrium line, the flow of the Taku Glacier has been in an equilibrium state. Surface mass balance was positive from 1946–1988 averaging +0.42 m a−1. This led to glacier thickening. From 1988–2006 an important change has occurred and annual balance has been −0.14 m a−1, and the glacier thickness has ceased increasing along Profile IV. Field measurements of ice depth and surface velocity allow calculation of the volume flux at Profile IV. Volume flux is then compared with the surface balance flux from the region of the glacier above Profile IV, determined annually in the field. Above Profile IV the observed mean surface flux from 1950–2006 is 5.50×108 m3 a−1 (±5%), while the calculated volume flux range for the same period flowing through profile IV is 5.00–5.47×108 m3 a−1. The mean surface flux has been greater than the volume flux, which has led to slow thickening of the Taku Glacier up to 1988. The thickening has not led to a change in the flow of Taku Glacier at Profile IV. Arendt, A. A.: Volume changes of Alaska glaciers: contributions to rising sea level and links to climate change, Ph.D dissertation, University of Alaska, Fairbanks, 2006. Arendt, A. A., Echelmeyer, K. A., Harrison, W. D., Lingle, C. S., and Valentine, V. B.: Rapid wastage of Alaskan glaciers and their contribution to rising sea level, Science, 297(5880), 382–385, 2002. Daellenbach, K. and Welsch, W.: Determination of surface velocities, strain rates, and mass flow rates on the Taku Glacier, Juneau Icefield, Alaska, Zeitschrift für Gletscherkunde und Glazialgeologie, Band 26, Heft 2, 169–177, 1993. Dobrin, M. B.: Introduction to Geophysical Prospecting, 3rd Edition, McGraw-Hill, New York, 201–254, 1960. Dyugerov, M. B. and Meier, M. F.: Year to year fluctuations of global mass balance of small glaciers and their contributions to sea level, Arctic Alpine Res., 29, 392–402, 1997. Lang, M.: Geodetic Activities of the 1997 Juneau Icefield Research Program Field Season, Open File Survey Report, Juneau Icefield Research Program, Foundation for Glacier and Environmental Research, Moscow, Idaho, 1997. Larsen, C. F., Motyka, R. J., Arendt, A. A., Echelmeyer, K. A., and Geissler, P. E.: Glacier changes in southeast Alaska and northern British Columbia and contribution to sea level rise, J. Geophys. Res., 112, F01007, doi:10.1029/2006JF000586, 2007. March, R. S. and Trabant, D. C.: Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1992 balance year, US Geological Survey Water-Resources Investigations Report 95–4277, 1996. Mayo, L. R., Trabant, D. C., and March, R. S.: A 30-Year Record of Surface Mass Balance (1966–95), and Motion and Surface Altitude (1975–95) at Wolverine Glacier, Alaska, US Geological Survey Open-File Report 2004–1069, 2004. McGee, S.: Juneau Icefield GPS Movement Profile Coordinates, JIRP Open File Survey Report, Juneau Icefield Research Program, Foundation for Glacier and Environmental Research, Moscow, Idaho, 2000. Miller, M. M.: Taku Glacier Evaluation Report. State of Alaska, Dept. of Highways and Bureau of Public Roads, US Dept. of Commerce, 1963. Miller, M. M. and Pelto, M.: Mass balance measurements on the Lemon Creek Glacier, Juneau Icefield, AK 1953–1998, Geografiska Annaler, 81A, 671–681, 1999. Motyka, R. and Post, A.: Taku Glacier influence of sedimentation, accumulation to total area ratio and channel geometry on the advance of a fjord-type glacier, in: Proceedings of the Third Glacier Bay Symposium, edited by: Engstrom, D. R., National Park Service, Anchorage AK, 38–45, 1995. Motyka, R. and Beget, J. E.: Taku Glacier, Southeast Alaska, U. S. A.: Late Holocene history of a tidewater glacier, Arctic Alpine Res., 28(1), 42–51, 1996. Nick, F. M., van der Veen, C. J., and Oerlemans, J.: Controls on advance of tidewater glaciers: Results from numerical modeling applied to Columbia Glacier, J. Geophys. Res., 112, F03S24, doi:10.1029/2006JF000551, 2007. Nolan, M., Echelmeyer, K., Motyka, R., and Trabant, D.: Ice thickness measurements of Taku Glacier, Alaska, USA, and their relevance to its recent behavior, J. Glaciol., 41(139), 541–552, 1995. Nye, J. F.: The flow of a glacier in a valley of rectangular, elliptic or parabolic cross section, J. Glaciol., 5(41) 661–690, 1965. Paterson, W. S. B.: The Physics of Glaciers, 2nd ed., Pergamon Press, Oxford. Pelto, M. and Miller, M. M.: Mass Balance of the Taku Glacier, Alaska from 1946 to 1986, Northwest Sci., 64(3), 121–130, 1990. Post, A. and Motyka, R.: Taku and Le Conte Glaciers, Alaska: Calving speed control of late-Holocene asynchrounous advances and retreats, Phys. Geogr., 16, 59–82, 1995. Ramage, J. M., Isacks, B. L., and Miller, M. M.: Radar Glacier zones in southeast Alaska, U.S.A.: field and satellite observations, J. Glaciol., 46(153), 287–296, 2000. Sprenke, K. F., Miller, M. M., McDonald, F., Haagen, C., Adema, G., Kelly, M., Barbour, S., and Caceres, B.: Geophysical investigation of the Taku-Llewellyn Divide: a NASA Earth Systems Field Research Project, Juneau Icefield, Alaska, Juneau Icefield Research Program Geophysics Open File Report 97-1, (Moscow, Idaho: Glaciological and Arctic Science Institute, University of Idaho), 1997. Van der Veen, C. J.: Fundamentals of Glacier Dynamics, Lisse, A. A. Balkema, 462 pp., 1999. Welsch, W., Lang, M., and Miller, M. M.: Geodetic Activites – Juneau Icefield, Alaska 1981–1996, Schriftenreihe des Studiengangs Vermessungskunde, Universität der Bundeswehr, Heft 50, 1996. Welsch, W. and Lang, M.: Geodetic Activities of the 1998 Juneau Icefield Research Program Field Season, Open File Survey Report, Juneau Icefield Research Program, Foundation for Glacier and Environmental Research, Moscow, Idaho, 81 pp., 1998.