Glaciers - Introduction
The icefields and mountain glaciers of Alberta are situated on the continental divide and the eastern slopes of the Canadian Rocky Mountains. Alberta’s glaciers are concentrated here for two primary reasons:
- They form at the highest elevations, where temperatures are coolest
- The continental divide and adjacent slopes receive large amounts of moisture from the Pacific air masses that flow in from B.C.
Approximately 37 peaks rise above 3,400 m along the spine of the Rockies, making this the highest obstacle that Pacific air masses encounter as they traverse southwestern Canada. Orographic uplift on the western slopes cools the air and induces precipitation. The resultant air masses are largely wrung out as they carry on eastward over the Canadian prairies.
The precipitation gradient in the eastern slopes of the Canadian Rocky Mountains is dramatic. Annual precipitation at the continental divide on Haig Glacier averaged 1,900mm between 2002-2009, for example (unpublished data), as compared with 430mm over this period in Calgary (Environment Canada, 2010) which lies 100 km to the east. Most of this falls as snow in the mountains, creating the numerous glaciers and icefields which are one of the hallmarks of the Canadian Rockies.
The report restricts its attention to runoff associated with glacier retreat: tapping of the water that is stored as ice in the glaciers of the Rocky Mountains. Runoff from the seasonal snowpack on glaciers is presumably ‘renewable’ – it will continue to feed the rivers even if the glaciers disappear from the landscape. However, with the loss of glacier ice, this snowpack contribution may also decline, as glaciers act as snow traps that encourage snow accumulation. The cold environment on glaciers also preserves much of this snow until later in the summer melt season, while routing through the glacier can introduce delays of weeks to months in delivering meltwater to the rivers, particularly in the early summer. Glacier retreat is therefore expected to result in earlier melting and runoff of seasonal snow from sites that are presently glaciated.
The locations of the glaciers referred to in the report include:
- Athabasca Glacier, Jasper National Park (52°11' N, 117°16' W)
- Haig Glacier, Kananaskis (50°43' N, 115°18' W)
- Kwadacha Glacier, Northern Rockies, B.C. (57°49' N, 124°55' W)
- Opabin Glacier, Yoho National Park (51°20' N, 116°18' W)
- Peyto Glacier, Banff National Park (51°41' N, 116°32' W)
These glaciers feed the Kananaskis (Bow River), Kicking Horse (Columbia River), Mistaya (North Saskatchewan River), Athabasca, and Kwadacha (Peace River).
General Comments on Glacier Water Resources
The contribution of glacier runoff to distal streamflow is often exaggerated. Glaciers offer a vivid element of the landscape and their contributions to surface runoff can indeed dominate in heavily-glacierized catchments, but a distinction needs to be made between the runoff from glacial ice and that derived from the seasonal snowpack.
For a glacier in equilibrium, there is no annual gain or loss of ice; the main effect of glacial cover is to create a more diffuse and extended season for meltwater runoff. That said, sustained glacier retreat does mean that long-term water storage is being tapped to augment the runoff derived from rainfall and seasonal snow. This means that current and future runoff is likely to be less than mean historical runoff.