August 18, 2013
Mangin Glacier and its unnamed neighbor flow down the north slope of Mount Joffre, Alberta and drain into Kananaskis Lake. The glacier like the vast majority in Alberta has been losing area and volume during its retreat. Bolch et al (2010) noted that the glaciers in western Canada had on average lost 11% of their area from 1985 to 2005, 16% on the east slope of the continental divide in the Rocky Mountains of Alberta. A comparison of Landsat imagery from 1994 and 2013, Google Earth imagery from 2005 and the Canadian Topographic map published in 1994, based on early 1990’s aerial photographs. In the map Mangin Glacier was a single ice body that extended for 3.2 km ending in a small lake at 2575 m, sections A-C were all joined, green line is glacier boundary for the map and brown line the 2005 glacier margin. By 1994 section C, yellow arrow, has only a tenuous connection and is clearly going to separate from parts A and B. Further a ridge between A and B is beginning to develop, red arrow. By 2005 in the Google Earth image sections A and B are nearly separated by the expanding ridge and C is fully separated from A and B. By 2013 A and B are fully separated, this image is from mid-August with a month of melting to go. The light blue is snowcover and the darker blue is bare glacier ice. In another month the amount of snowcover will be very small. For example earlier this month on Sholes Glacier in the North Cascades we observed rapid expansion of the blue ice zone from 12, 500 square meters on Aug. 3 to 35,000 square meters on Aug. 9. The retreat of the unnamed glacier labeled D is apparent in the comparison of the 1994 and 2013 images, note the green arrow. This retreat is 300-400 m, with much of the retreat coming after 2005. Mangin Glacier’s retreat from the map based on early 1990’s imagery is 500 m, combined with retreat of the top of the glacier 20% of the glacier length has been lost in the last 20 years. Mangin Glacier has been retreating even on its upper margin, this is indicative of a glacier without a consistent accumulation zone, and a glacier that will not survive(Pelto, 2010). Just southeast is Petain Glacier also retreating. As the glaciers retreat their meltwater that is primarily yielded in late summer when other sources are at a minimum will decline. It is anticipated that during this century glacier contributions to streamflow in Alberta will decline from 1.1 km3 a−1 in the early 2000s to 0.1 km3 a−1 by the end of this century Marshall et al (2011).