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

• Published in: Journal of Glaciology
• Main Authors: JOANNA C. YOUNG, ANTHONY ARENDT, REGINE HOCK, ERIN PETTIT
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2018
• Subjects: glacier mass balance; glacier monitoring; mass-balance reconstruction; mountain glaciers; Environmental sciences; GE1-350; Meteorology. Climatology; QC851-999; glacier; glaciers; Journal of Glaciology; Alaska
• Online Access: https://doi.org/10.1017/jog.2017.80; https://doaj.org/article/4117e57ee7724da4b831614d75199cd2

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 km2) glacier with one of the greatest elevation ranges globally (264–6108 m 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( ± σ = 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.