No abstract

Maps of glacier area in western Canada have recently been generated for 1985(Bolch et al., 2010, providing the first complete inventory of glacier cover in Alberta and British Columbia. Western Canada lost about 11% of its glacier area over this period, with area loss exceeding 20% on the eastern slopes of the Canadian Rockies. Glacier area is difficult to relate to glacier volume, which is the attribute of relevance to water resources and global sea level rise. We apply several possible volume-area scaling relations and glacier slope-thickness relations to estimate the volume of glacier ice in the headwater regions of rivers that spring from the eastern slopes of the Canadian Rocky Mountains, arriving at an estimate of 55 ± 15 km 3 . We cannot preclude higher values, because the available data indicate that large valley glaciers in the Rocky Mountains may be anomalously thick relative to what is typical in the global database that forms the basis for empirical volume-area scaling relations.Incorporating multivariate statistical analysis using observed mass balance data from Peyto Glacier, Alberta and synoptic meteorological conditions in the Canadian Rockies (1966Rockies ( -2007, we model future glacier mass balance scenarios on the eastern slopes of the Rockies. We simulate future volume changes for the glaciers of the Rockies by using these mass balance scenarios in conjunction with a regional ice dynamics model. These projections indicate that glaciers on the eastern slopes will lose 80-90%

We reconstruct the terminus position of a mountain glacier in British Columbia, Canada from annual push moraines formed between 1959 and 2007. Our reconstruction represents the longest, annually‐resolved record of length change for a North American glacier. Comparison of annual recession with climate records indicates that glacier recession is controlled by air temperatures during the ablation season and accumulation season precipitation during the previous decade. Analysis among records of glacier frontal variation and mass balance in western North America similarly reveals an immediate terminus reaction to summer and net balance and a delayed reaction to winter and net balance. Other mountain ranges may contain long series of push moraines that could be exploited as climate proxies, and to improve understanding of glacier response to climate.

We acquired center-line surface elevations from glaciers in the St Elias Mountains of Alaska/northwestern Canada using aircraft laser altimetry during 2000–05, and compared these with repeat measurements acquired in 2007. The resulting elevation changes were used to estimate the mass balance of 32 900 km2 of glaciers in the St Elias Mountains during September 2003 to August 2007, yielding a value of −21.2 ± 3.8 Gt a−1, equivalent to an area-averaged mass balance of −0.64 ± 0.12 m a−1 water equivalent (w.e.). High-resolution (2 arc-degrees spatial and 10 day temporal) Gravity Recovery and Climate Experiment (GRACE) mass-balance estimates during this time period were scaled to glaciers of the St Elias Mountains, yielding a value of −20.6 ± 3.0 Gt a−1, or an area-averaged mass balance of −0.63 ± 0.09 m a−1 w.e. The difference in balance estimates (altimetry minus GRACE) was −0.6 ± 4.8 Gt a−1, well within the estimated errors. Differences likely resulted from uncertainties in subgrid sampling of the GRACE mass concentration (mascon) solutions, and from errors in assigning an appropriate near-surface density in the altimetry estimates. The good correspondence between GRACE and aircraft altimetry data suggests that high-resolution GRACE mascon solutions can be used to accurately assess mass-balance trends of mountain glacier regions that are undergoing large changes.

We estimate the glacier mass balance of a 9.5 km2 mountain glacier using three approaches for balance years 2009, 2010 and 2011. The photogrammetric, GPS and glaciological methods yielded sampling densities of 100, 5 and 2 points km-2, with measurement precisions of ± 0.40, ± 0.10 and ± 0.10 m w.e. respectively. Our glaciological measurements likely include a positive bias, due to omission of internal and basal mass balance, and uncertainty in determining the interface between snow and firn with a probe (±0.10 m w.e.). Measurements from our photogrammetric method include a negative bias introduced by the manual operator and our temperature index model used to correct for different dates of imaging (0.15 m w.e.), whereas GPS measurements avoid these biases. The photogrammetric and GPS methods are suitable for estimating glacier-wide annual mass balance, and thus provide a valuable measure that complements the glaciological method. These approaches, however, cannot be used to estimate mass balance at a point or mass-balance profiles without a detailed understanding of the vertical component of ice velocity.