Glaciological measurements and mass balances from Sperry Glacier, Montana, USA, years 2005–2015

Abstract

Abstract. Glacier mass balance measurements help to provide an understanding of the behavior of glaciers and their response to local and regional climate. In 2005 the United States Geological Survey established a surface mass balance monitoring program on Sperry Glacier, Montana, USA. This project is the first quantitative study of mass changes of a glacier in the US northern Rocky Mountains and continues to the present. The following paper describes the methods used during the first 11 years of measurements and reports the associated results. From 2005 to 2015, Sperry Glacier had a cumulative mean mass balance loss of 4.37 m w.e. (water equivalent). The mean winter, summer, and annual glacier-wide mass balances were 2.92, −3.41, and −0.40 m w.e. yr−1 respectively. We derive these cumulative and mean results from an expansive data set of snow depth, snow density, and ablation measurements taken at selected points on the glacier. These data allow for the determination of mass balance point values and a time series of seasonal and annual glacier-wide mass balances for all 11 measurement years. We also provide measurements of glacier extent and accumulation areas for select years. All data have been submitted to the World Glacier Monitoring Service and are available at doi:10.5904/wgms-fog-2016-08. This foundational work provides valuable insight about Sperry Glacier and supplies additional data to the worldwide record of glaciers measured using the glaciological method. Future research will focus on the processes that control accumulation and ablation patterns across the glacier. Also we plan to examine the uncertainties related to our methods and eventually quantify a more robust estimate of error associated with our results.

Local topography increasingly influences the mass balance of a retreating cirque glacier

“…3) would suggest that the equilibrium line altitude remained relatively constant from 1950 to 2014 despite climate warming. Thus as Sperry Glacier retreated, its accumulation area ratio (Cogley et al, 2011) increased. With an increased fraction of the glacier remaining snow-covered throughout the melt season, the average glacier albedo increases (Naegeli and Huss, 2017).…”

“…Therefore, glaciological mass balance measurements of seasonal mass gains and losses at Sperry Glacier are available from the year 2005 onward (Clark et al, 2017). We used these data, measured in the field according to standard mass balance protocols (Kaser et al, 2003;Østrem and Brugman, 1991), to define specific, conventional (Cogley et al, 2011) winter and summer glacier mass balance from 2005 to 2014. We also analyzed point balance data collected along a longitudinal transect (stakes in Fig.…”

Local topography increasingly influences the mass balance of a retreating cirque glacier

“…To convert volume to mass, we adopted the approximation outlined by Huss (2013), and assigned ice density as ρ = 850 ± 60 kg m -3 . Note that this differs somewhat from the 874 kg m -3 used for Sperry Glacier glaciological mass balance by Clark et al (2017), but that this value falls within the uncertainty bounds of our assigned ice density of 850 ± 60 kg m -3 .…”

“…m -1 for winter and 0.003-0.011 m w.e. m -1 for summer (Clark et al, 2017). The ±60 kg m -3 density error amounted to <8% error on geodetic mass balances.…”

“…Glacier are available from the year 2005 onward (Clark et al, 2017). We used these data, measured in the field according to standard mass balance protocols (Kaser et al, 2003;Ostrem and Brugman, 1991) to define specific, conventional (Cogley et al, 2011) winter and summer glacier mass balance from 2005-2014.…”