The challenge of monitoring glaciers with extreme altitudinal range : mass-balance reconstruction for Kahiltna Glacier, Alaska

• Published in: Journal of Glaciology
• Main Authors: Young, Joanna C., Arendt, Anthony, Hock, Regine, Pettit, Erin
• Format: Article in Journal/Newspaper
• Language: English
• Published: Uppsala universitet, Luft-, vatten- och landskapslära 2018
• Subjects: glacier mass balance; glacier monitoring; mass-balance reconstruction; mountain glaciers; Physical Geography; Naturgeografi; glacier; glaciers; Journal of Glaciology; Alaska
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-351023; https://doi.org/10.1017/jog.2017.80

Glaciers spanning large altitudinal ranges often experience different climatic regimes with elevation, creating challenges in acquiring mass-balance and climate observations that represent the entire glacier. We use mixed methods to reconstruct the 1991-2014 mass balance of the Kahiltna Glacier in Alaska, a large (503 km(2)) glacier with one of the greatest elevation ranges globally (264-6108m a. s.l.). We calibrate an enhanced temperature index model to glacier-wide mass balances from repeat laser altimetry and point observations, finding a mean net mass-balance rate of -0.74 mw.e. a(-1)(+/-sigma = 0.04, std dev. of the best-performing model simulations). Results are validated against mass changes from NASA's Gravity Recovery and Climate Experiment (GRACE) satellites, a novel approach at the individual glacier scale. Correlation is strong between the detrended model-and GRACE-derived mass change time series (R-2 = 0.58 and p << 0.001), and between summer (R-2 = 0.69 and p = 0.003) and annual (R-2 = 0.63 and p = 0.006) balances, lending greater confidence to our modeling results. We find poor correlation, however, between modeled glacier-wide balances and recent single-stake monitoring. Finally, we make recommendations for monitoring glaciers with extreme altitudinal ranges, including characterizing precipitation via snow radar profiling.