Improving estimation of glacier volume change: a GLIMS case study of Bering Glacier System, Alaska

• Main Authors: Beedle, M. J., Dyurgerov, M., Tangborn, W., Khalsa, S. J. S., Helm, C., Raup, B., Armstrong, R., Barry, R. G.
• Other Authors: National Snow and Ice Data Center (NSIDC), University of Colorado Boulder, Geography Program, University of Northern British Columbia Prince George (UNBC), Institute of Arctic Alpine Research University of Colorado Boulder (INSTAAR), HyMet Inc., 13629 Burma Rd. SW
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; glacier; The Cryosphere; The Cryosphere Discussions; Alaska
• Online Access: https://hal.archives-ouvertes.fr/hal-00298527; https://hal.archives-ouvertes.fr/hal-00298527/document; https://hal.archives-ouvertes.fr/hal-00298527/file/tcd-1-169-2007.pdf

International audience The Global Land Ice Measurements from Space (GLIMS) project has developed tools and methods that can be employed by analysts to create accurate glacier outlines and resultant measures of glacier extent. To illustrate the importance of accurate glacier outlines and the effectiveness of GLIMS standards we have conducted a case study on Bering Glacier System (BGS), Alaska. BGS is a complex glacier system aggregated from multiple drainage basins, numerous individual ice streams, and many accumulation areas. Published measurements of BGS surface area vary from 1740 to 6200 km 2 , depending on how the boundaries of this system have been defined. Utilizing GLIMS tools and standards we have completed a new outline and analysis of the area-altitude distribution (hypsometry) of BGS using Landsat images from 2000 and 2001. We compared this new outline (3632 km 2 ) with three previous outlines to illustrate the errors that result from the widely varying estimates used in previous analysis of BGS area. The use of different BGS outlines results in highly variable measures of volume change and net balance (b n ). Outline variability alone results in a net balance rate range of ?1.0 to ?3.2 m/yr water equivalent (W.E.), a volume change range of ?4.2 to ?8.2 km 3 /yr, and a near doubling in contributions to sea level equivalent (SLE), 0.0122 mm/yr to 0.0236 mm/yr. A study of three different models of BGS net balance leads us to favor estimates of b n of ?1.2 m/yr W.E. and total volume change of ?4.2 km 3 /yr for the period 1950?2004. These estimates result in a near doubling of contributions to sea level equivalent when compared with previous studies. While current inaccuracies in glacier outlines hinder our ability to fully understand glacier change, there is no reason why our understanding of glacier extents should not be comprehensive and accurate. Such accuracy is possible with the increasing volume of satellite imagery of glacierized regions, and recent advances in tools and standards.