Determination of morphologic and volumetric change, Peyto Glacier, Alberta, 1966-1989

During the summer months of July and August 1989, approximately 23 years after a photogrammetric survey on August 22, 1966, Peyto Glacier, a glacier selected for study during the International Hydrologic Decade (IHD) 1965-74, was re-surveyed using terrestrial geodetic surveying techniques. The volumetric and morphologic change of Peyto Glacier, Alberta from 1966 to 1989 is estimated through a combined application of digital cartometry, digital geodetic survey and Triangulated Irregular Network (TIN) digital terrain modeling and analysis. Changes in glacial volume, areal extent, teriminus position, percentage basin glaciation, slope, and aspect for the 23 year interval are shown. Additionally, a 1:10000 contour map of the 1989 Peyto Glacier is presented. The volumetric change of Peyto Glacier is estimated to be -154.6 10^6m3 and compares favourably with the figure of -155.3 106m3 obtained through a directly measured accumulation/ablation stake network. The surface area of Peyto Glacier 1989 is estimated at 12.04 km2, a loss of 1.07 km2 from the 1966 surface area of 13.11 km2. The terminus of Peyto Glacier has retreated 592 m. Significant ablation of the glacier surface below approximately 2600 masl has occurred. A maximum of 86 m vertical loss was measured in the ablation zone. Slope and aspect analysis reveals that although significant ablation has occurred below 2600 masl, surface geometry has remained remarkably similar. This is also true of the hypsometry which, with the exception of the area below 2100 masl, shows areal distributions have changed little over the twenty-three years. Despite complications encountered with aspects of the surface data sets, examination of the methods applied suggests that in situ digital geodetic surveying in concert with TIN DTM analysis is an efficient, reliable, and relatively inexpensive means of assessing glacial morphologic and volumetric change