Current state of Alaska's glaciers and evolution of Black Rapids Glacier constrained by observations and modeling

• Main Author: Kienholz, Christian
• Other Authors: Hock, Regine, Arendt, Anthony, Bliss, Andrew, Braun, Matthias, Meyer, Franz, Truffer, Martin
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2016
• Subjects: Canada; Fairbanks; alaska range; glacier; glacier*; glaciers; Alaska
• Online Access: http://hdl.handle.net/11122/7319

Dissertation (Ph.D.) University of Alaska Fairbanks, 2016 Glaciological studies rely on a wide range of input data, the most basic of which, accurate glacier extents, were not available on an Alaska wide scale prior to this work. We thus compiled a glacier database for Alaska and neighboring Canada using multi-sensor satellite data from 2000 to 2011. The inventory yielded a glacierized area of 86,720 km², which corresponds to ~12% of the global glacierized area outside the ice sheets. For each of the ~27,100 glaciers, we derived outlines and 51 variables, including centerline lengths, outline types, and debris cover, which provide key input for observational and modeling studies across Alaska. Expanding on this large-scale observational snapshot, we conducted two case studies on Black Rapids Glacier, Eastern Alaska Range, to assess its evolution during the late 20th and 21st centuries. Black Rapids Glacier, 250 km² in area, was chosen given its surge-type dynamics and proximity to critical infrastructure. Remotely sensed and in-situ elevation observations over the 1980--2001--2010 period indicated strong mass loss of Black Rapids Glacier (~0.5 m w.e. a⁻¹), with higher thinning rates over the 2001--2010 (~0.65 m w.e. a⁻¹) than the 1980--2001 period (~0.4 m w.e. a⁻¹). A coupled surface mass balance-glacier dynamics model, driven by reanalysis climate data, reproduced the glacier shrinkage. It identified the increasingly negative summer balances, a consequence of the warming atmosphere, as the main driver for the negative mass balance trend. Elevation observations in Black Rapids' surge reservoir suggested a surge was not imminent at the time of the analysis due to the lack of ice thickening. Re-initiation of sufficient elevation growth in the surge reservoir would require more favorable surface mass balances, as observed in the early 1980s. Compared to nearby Gulkana Glacier (a USGS benchmark glacier), the observed specific mass losses at Black Rapids Glacier were less pronounced, ~0.4 vs. 0.5 m w.e. a⁻¹ ...