Multi-year evaluation of airborne geodetic surveys to estimate seasonal mass balance, Columbia and Rocky Mountains, Canada

Abstract

Abstract. Seasonal measurements of glacier mass balance provide insight into the relation between climate forcing and glacier change. To evaluate the feasibility of using remotely sensed methods to assess seasonal balance, we completed tandem airborne laser scanning (ALS) surveys and field-based glaciological measurements over a 4-year period for six alpine glaciers that lie in the Columbia and Rocky Mountains, near the headwaters of the Columbia River, British Columbia, Canada. We calculated annual geodetic balance using coregistered late summer digital elevation models (DEMs) and distributed estimates of density based on surface classification of ice, snow, and firn surfaces. Winter balance was derived using coregistered late summer and spring DEMs, as well as density measurements from regional snow survey observations and our glaciological measurements. Geodetic summer balance was calculated as the difference between winter and annual balance. Winter mass balance from our glaciological observations averaged 1.95±0.09 m w.e. (meter water equivalent), 4 % larger than those derived from geodetic surveys. Average glaciological summer and annual balance were 3 % smaller and 3 % larger, respectively, than our geodetic estimates. We find that distributing snow, firn, and ice density based on surface classification has a greater influence on geodetic annual mass change than the density values themselves. Our results demonstrate that accurate assessments of seasonal mass change can be produced using ALS over a series of glaciers spanning several mountain ranges. Such agreement over multiple seasons, years, and glaciers demonstrates the ability of high-resolution geodetic methods to increase the number of glaciers where seasonal mass balance can be reliably estimated.

Glacier mass and area changes on the Kenai Peninsula, Alaska, 1986–2016

“…of the elevation differences between the ASTER DEMs and IFSAR DEM over nonglacierized pixels (stable terrain; σ non ) can be used as a first estimate of the σ autocorr , if the spatial correlation of the elevation differences is accounted for (Rolstad and others, 2009). Following Gardelle and others (2013), we calculated the standard error (SE) of the mean elevation change:where N eff is the effective number of the pixels after de-correlation defined by,where N tot is the total number of pixels on the nonglacierized area (stable terrain); R is the pixel size (30 m), d is the de-correlation distance assumed to be 600 m as suggested by Bolch and others (2011) and also used in previous geodetic mass-balance studies (Brun and others, 2017; Menounos and others, 2019; Pelto and others, 2019). σ autocorr was then calculated using SE and the mean elevation differences of the nonglacier region :…”

Multi-scale snowdrift-permitting modelling of mountain snowpack

“…The summer and winter DEMs were co-registered to minimize slope and aspect-induced errors (Nuth and Kääb, 2011). Additional details about the processing workflow over snow-covered terrain can be found in Pelto et al (2019).…”

“…Cells of the 50-m raster that contained more than 75 % of masked cells in the 5-m snow depth map were masked out. In addition, grid points covered by glaciers identified in the Randolph Glacier Inventory (Pfeffer et al, 2014) were removed from the analysis since elevation change over these surfaces is also influenced by ice dynamics (Pelto et al, 2019). and the Wasserstein distance of order 1, W1, (Rüschendorf, 1985) were used to quantify the agreement between the simulated and the observed distributions.…”

Summary and synthesis of Changing Cold Regions Network (CCRN) research in the interior of western Canada – Part 2: Future change in cryosphere, vegetation, and hydrology

“…There may also be an interaction with wildfire in western Canada, with deposition of black carbon and forest-fire fallout further reducing glacier albedo and providing nutrients to microbial communities (e.g., Marshall and Miller, 2020). High thinning rates in the upper accumulation area of many glaciers in western Canada indicate that these processes are well under way (Pelto et al, 2019), while reductions in accumulation zone extent can lead to rapid glacier disintegration, and even complete disappearance. Glacier fragmentation and detachment of tributary ice streams leads to loss of ice supply to lower reaches, which can then become stagnant and melt out.…”