CRYSYS: Glaciers in Canada - CRYSYS - CRYosphere SYStem in Canada - [Meteorological Service of Canada

GLACIERS IN CANADA

Glaciers are an important part of the Canadian landscape, as Canada’s surface terrain has been defined by a million years of glacier and ice-sheet fluctuations. Today only Antarctica and Greenland have more glacier ice. In certain parts of Canada glaciers also play a key role in supplying communities with fresh water for irrigation, drinking, and hydro-electric power. By storing water seasonally for up to thousands of years, glaciers regulate stream flow by augmenting inputs when precipitation is low and masking the variability of precipitation inputs.

Berg Lake & glacier, Mt. Robson, Alberta (Doug Latimer)

GLACIERS AND CLIMATE

Glaciers have much to tell us about past and present environmental conditions. Analysis of ice cores taken from glaciers reveals a layer-by-layer record of past temperatures, pollution levels, and atmospheric conditions. This information about past climates helps researchers understand variations in the earth’s climate, and predict the effects of changes in the future. Today, glacier fluctuations are recognised as high-confidence indicators of air temperature trends and as valuable evidence in the early detection of man-induced climate changes.

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Figure 1: Graph showing the retreat of the Athabasca and Saskatchewan glaciers since 1700 (M. Brugman).

Since the end of the Little Ice Age (about 1850), glaciers have been melting steadily in most parts the world. This loss in glacier mass has been greatest in small alpine-type glaciers (e.g. eastern Rocky Mountains - see Figure 1 above). Current research indicates that global warming may be playing a significant part in this meltdown, as the current rate of glacier shrinkage is broadly consistent with estimated anthropogenic greenhouse forcing (a few Wm^-2). More recent results from studies in the mid 1990s (compared to previous studies carried out in the 1950s and 1960s) indicate that the Columbia Icefield glaciers (e.g. Athabasca, Saskatchewan glaciers) have further thinned and retreated dramatically, and that an acceleration in the flow (below the accumulation area) has occurred.

MEASURING GLACIERS

Various methods have been employed to measure the "health" of glaciers, among them being mass balance calculations and interferometry. The mass balance of a glacier is the difference between the mass that the glacier accumulates in winter (from snow) and that which is lost by melting (ablation) during the summer. It involves detailed in-situ observation and scientific monitoring of a glacier over several seasons. The photo below shows a cryospheric scientist in the field measuring glacial properties in order to calculate a mass-balance value.

a cryospheric scientist in the field measuring glacial properties

Figure 2: A CRYSYS scientist taking measurements in the Rockies (Photo: Chris Hopkinson).

Interferometry involves remote sensing and the use of a Synthetic Aperture Radar (SAR). The method is capable of providing the annual net balance of a glacier and can also provide details on the thickness change and flow continuity of a glacier when the surface melt is minimal.

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Figure 3: An Interferometric map of Columbia Icefields (east) showing 24hr surface ice motion in Fall 1995. Each interference fringe on this map represents approximately 6 cm/day away from the ERS satellite (on an ascending path). In the extreme bottom of the image are broad half-elipsoidal curves surrounded by a "Bull's Eye"; these correspond to the Saskatchewan Glacier showing an increase in ice velocity from the terminus (lower right side of the image) to a peak (indicated by the "bulls-eye"), which is located just up-glacier from Castleguard Meadows. Glacier velocity and ice depth is at maximum in this region (near the mean annual snowline). To the left side of this feature, is the accumulation are of Columbia Icefields where the ice velocities are lower, and to the north lie the Athabasca and Dome glaciers. The ice velocities determined by this interferometric method agree well with the field measurements of ice velocity. Source: M. Brugman.

Interferometric analysis can provide a very accurate topographic map of a glacier or icefield. The results can be combined with field survey and velocity studies at the same time to provide a unique data set on detailed glacier motion and topographic change. However, there are problems related to the 3-dimensional flow field that is sensed by the interferometry method.

GLIMS

GLIMS (Global Land Ice Measurements from Space) is a new project designed to monitor the world's glaciers primarily using data from the ASTER (Advanced Spaceborne Thermal Emission and reflection Radiometer) instrument aboard the EOS Terra spacecraft, launched in December 1999. A set of software tools is being applied to the tracking of glaciers' areal extent, location of snow line at the end of the melt season, velocity field and the location of terminus. A network of centers around the world that will monitor the glaciers in their regions the database infrastructure capable of storing and manipulating approximately 80 gigabytes of additional data per year.

CANADIAN GLACIER INVENTORY

The Canadian glacier inventory was initiated in 1945 to monitor glacier contributions to river systems. Its objective was to identify and measure every perennial snow and ice body in Canada. Data was initially obtained from maps, air photos and field surveys (surface elevations, flow velocities, ice marginal positions) and was used mainly for forecasting water supply and in flood monitoring. The Water Survey of Canada continued these glacier observations and terrestrial photogrammetry until about 1980.

Over the years, a complete air photograph coverage of all the glacierized areas in Canada has been acquired. The Canadian Glacier Inventory now contains quantitative information on about 40,000 of Canada's 100,000 glaciers, and annotated maps and photographs of many more. A large collection of historical photographs of Baffin and Bylot Islands exist, and there are several thousand photographs of glaciers in the Coast Ranges taken around 1900. Special software, called GLADYS, has been developed to store and retrieve the basic inventory data, and a bibliography has been assembled with some 40,000 references to all aspects of snow and ice studies in Canada from 1975 onwards. The whole inventory now resides at the Canadian Glacier Information Centre (CGIC) in Saskatoon.