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Glacial mass balance estimated through the geodetic method requires glacial surface coordinate observations from historical and contemporary sources. Contemporary observations and historical topographic maps are typically referenced to separate horizontal and vertical datums and observed with different sampling intervals. This research demonstrates the sensitivity of glacial change detection to the datum considerations and sampling schemes through case studies of Andrei, Bridge and Peyto glaciers in Western Canada. To simulate the procedure of observing the glacial surfaces, profile lines were sampled from Digital Elevation Model (DEMs) on contour intervals for historical data and horizontal intervals for contemporary data. Profile lines from the following scenarios were compared: (1) different horizontal and vertical sampling schemes; (2) the horizontal datum was correctly reconciled but the vertical datum was not; (3) the vertical datum was correctly reconciled but the horizontal datum was not; (4) both the horizontal and vertical datums were correctly reconciled; and (5) both the horizontal and vertical datums were incorrectly reconciled. Vertical errors of up to 6.9 m, 6.0 m and 5.0 m were observed due to sampling effects and vertical errors of 22.2 m, 9.9 m and 55.0 m were observed due to datum inconsistencies on Bridge, Andrei and Peyto glacier respectively. Horizontal datum inconsistencies manifested as erratic levels of growth or downwasting along the glacial surface profile and vertical datum errors manifested as a consistent vertical offset. Datum inconsistencies were identified to contribute errors of up to 257.2 × 106 m3 (or 87%) and 54.6 × 106 m3 (or 580%) of estimated volume change below and above the equilibrium line respectively on Peyto Glacier. The results of this study provide an estimate of typical errors due to sampling constraints or datum inconsistencies as well as guidance for identifying where these error sources have contaminated mass balance results.

Ground-penetrating radar (GPR) surveys at a center frequency of 500 MHz were used to determine winter (2007/08) and net annual (2005–07) snow water equivalent (SWE) patterns across the upper parts of Belcher Glacier, Devon Ice Cap, Nunavut, Canada. The GPR measurements were validated against snow depths determined from avalanche probe measurements, and converted to SWE values using densities measured with a down-borehole neutron density probe and in shallow snow pits. Distinct internal reflection horizons (IRHs) in the GPR record were formed during warm summers in 2007 and 2005, and a large rain event in summer 2006 which caused ice to accumulate above the 2005 melt surface. Elevation provides the dominant control on winter SWE distribution across the basin, with surface topography (e.g. gullies) also being locally important. Based on the location where IRHs intersected the ice-cap surface, the basin-wide firn line occurred at an altitude of 1260–1300 m over the period 2005–08. Net mass balance across the accumulation area of Belcher Glacier averaged 0.24 m w.e. a−1 over the period 2005–07, mainly dependent on altitude. This is a little higher than most previous estimates for the period since the 1960s, although the differences lie within error limits.

Recognizing that climate influences both annual tree-ring growth and glacier mass balance, changes in the mass balance of Place Glacier, British Columbia, were documented from increment core records. Annually resolved ring-width (RW), maximum (MXD), and mean density (MD) chronologies were developed from Engelmann spruce and Douglas-fir trees sampled at sites within the surrounding region. A snowpack record dating to AD 1730 was reconstructed using a multivariate regression of spruce MD and fir RW chronologies. Spruce MXD and RW chronologies were used to reconstruct winter mass balance (Bw) for Place Glacier to AD 1585. Summer mass balance (Bs) was reconstructed using the RW chronology from spruce, and net balance was calculated from Bw and Bs. The reconstructions provide insight into the changes that snowpack and mass balance have undergone in the last 400 years, as well as identifying relationships to air temperature and circulation indices in southern British Columbia. These changes are consistent with other regional mass-balance reconstructions and indicate that the persistent weather systems characterizing large scale climate-forcing mechanisms play a significant glaciological role in this region. A comparison to dated moraine surfaces in the surrounding region substantiates that the mass-balance shifts recorded in the proxy data are evident in the response of glaciers throughout the region.

The influence of digital elevation model (DEM) resolution to modelled glacier melt during peak melt production was evaluated by performing a clear sky GIS radiation simulation over the Peyto Glacier in the Canadian Rockies. DEMs were generated at eight resolutions ranging from 1 m to 1000 m grid spacing from airborne lidar data. When applied to the planar area (PA) of the terrain, it was found that total melt increased with DEM resolution (r2 = 0·63) by 4% over 3 orders of magnitude. This systematic scaling-effect was mitigated at the basin scale, however, when the DEM slope variant area (SVA) was used to account for the increased divergence from PA as resolution increases. However, even after the inclusion of SVA in glacier surface melt simulations, localized melt variations with scale were still evident in the ablation and accumulation zone observations. In the ablation zone, there was a systematic increase in simulated melt (∼4%) as resolution decreased from 1 m to 1000 m (r2 = 0·89), with the opposite effect in the accumulation zone (r2 = 0·81). DEM resolution also affected the diurnal melt cycle, such that for the entire glacier there was a tendency for a morning over-estimation and afternoon underestimation of melt rate with decreasing resolution. For the accumulation zone, there was an increased melt rate at low resolutions occurring in the afternoon, while in the ablation zone there was a tendency for increasing melt rates with decreasing resolution throughout the day. These localized spatio-temporal variations in simulated melt are largely due to the lowering of ridges and raising of valley floors that occur as resolution decreases. This scale dependence in the representation of terrain morphology directly controls the pattern and relative proportion of direct beam shadowing over actively melting surfaces and thereby has a systematic influence on the grid cell-level hydrological balance. It is recommended that GIS-based glacier melt modelling routines take into account the slope area of grid cells, while noting that the choice of DEM scale can have a discernible and systematic influence on modelled runoff magnitude. It is important to note that while higher grid resolutions mitigate the effect of terrain smoothing on spatio-temporal melt patterns, lower resolutions actually mitigate the systematic error associated with assuming all surface areas are planar. Copyright © 2010 John Wiley & Sons, Ltd and Her Majesty the Queen in right of Canada.

Due to access difficulties in active alpine moraine environments, it can be challenging to accurately map and quantify debris cover and ice-core extent. To aid in identifying the presence and extent of ice-cored moraine, a non-invasive method of mapping spatial and temporal moraine temperature patterns using a light detection and ranging (lidar) digital elevation model (DEM) and sequences of oblique thermal imagery was evaluated. A procedure of lidar DEM-based orthorectification of thermal images collected through time from different locations enabled maps of temperature change to be generated and thermal signatures plotted. Although no exposed ice was visible on the moraine slope studied, the presence of shallow ice core beneath the debris-covered surface was inferred in areas of cooler temperatures during daylight solar heating and rapid thermal decay after sunset. It is presumed that this apparent increased heat loss in some areas of the moraine is being used to drive internal melt processes. It is bel...

A large rock and ice avalanche occurred on the north face of Mount Steele, southwest Yukon Territory, Canada, on July 24, 2007. In the days and weeks preceding the landslide, several smaller avalanches initiated from the same slope. The ice and rock debris traveled a maximum horizontal distance 5.76 km with a maximum vertical descent of 2,160 m, leaving a deposit 3.66 km2 in area on Steele Glacier. The seismic magnitude estimated from long-period surface waves (M s) is 5.2. Modeling of the waveforms suggests an estimated duration of approximately 100 s and an average velocity of between 35 and 65 m/s. This landslide is one of 18 large rock avalanches known to have occurred since 1899 on slopes adjacent to glaciers in western Canada. We describe the setting, reconstruct the event chronology and present a preliminary characterization of the Mount Steele ice and rock avalanches based on field reconnaissance, analysis of seismic records and an airborne LiDAR survey. We also present the results of a successful dynamic simulation for the July 24 event.

Interpretation of ice mass elevation changes observed by satellite altimetry demands quantification of the proportion of elevation change which is attributable to variations in firn densification. Detailed stratigraphic logging of snowpack structure and density was carried out at ~1km intervals along a 47 km transect on Devon Ice Cap, Canada, in spring (pre-melt) and autumn (during/ after melt) 2004 and 2006 to characterize seasonal snowpack variability across the full range of snow facies. Simultaneous meteorological measurements were gathered. Spring (pre-melt) snowpacks show low variability over large spatial scales, with low-magnitude changes in density. The end-of-summer/ autumn density profiles show high variability in both 2004 and 2006, with vastly different melt regimes generating dissimilar patterns of ice-layer formation over the two melt seasons. Dye-tracing experiments from spring to autumn 2006 reveal that vertical and horizontal distribution of meltwater flow within and below the annual snowpack is strongly affected by the pre-existing, often subtle stratigraphic interfaces in the snowpack, rather than its bulk properties. Strong interannual variability suggests that using a simple relationship between air temperature, elevation and snowpack densification to derive mass change from measurements of elevation change across High Arctic ice caps may be misguided. Melt timing and duration are important extrinsic factors governing snowpack densification and ice-layer formation in summer, rather than averaged air temperatures.

Three ice cores were recovered on or near Mount Logan, Yukon, Canada, at 3017, 4135 and 5340 ma.s.l. in 2002. Prior to ice-core drilling, we collected snow-pit and shallow core samples from Mount Logan in 2001 to study seasonal and spatial variations of snow chemistry. We dug snow pits at six sites between 2420 and 5340 m a.s.l. before the beginning of the melt season, with the exception of a pit at 3180 m a.s.l., where the melt season had just started but had affected only the near-surface stratigraphy. Three of the pits were extended deeper with a shallow core. The snow-pit and core samples were analyzed for ion chemistry and δ18O. A series of depth profiles of ions and δ18O shows spatial variations, though characteristic peaks can usually be traced across all the profiles. Concentrations and deposition fluxes of Na+ and Cl−, which are mainly of sea-salt origin, decrease with altitude. On the other hand, deposition fluxes of NO3−, SO42–, Ca2+ and NH4+ show a weak positive relationship with elevation below the summit plateau. Stable isotopes (δ18O) decrease with altitude, with a distinctive jump between 3200 and 4500 m a.s.l., as was reported previously. Stable isotopes (δ18O), Cl−, CH3SO3− (MSA), Na+ and Ca2+ show clear seasonal variations, which would enable us to date the cores by annual-layer counting.

Maps of glacier area in western Canada have recently been generated for 1985 and 2005 (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 km3. 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. Inco...

Discusses logistics and applications of the first complete airborne scanning LiDAR survey of a glacierised mountain basin. The survey was conducted over a 25/spl times/6 km area with ground height variation from 1800 m asl to 3400 m asl. The resolution of survey points on the ground varied from 1 per sq metre to around 1 per 4 sq metres, depending on elevation. Correspondence from swath to swath is very good despite the extreme nature of the topography and individual ground laser heights are accurate to within 20 cm. Glaciological applications for the high-resolution digital elevation data are outlined. Special attention is paid to radiation loading model-scaling issues.