Comparison of Columbia Glacier, which is the glacier flowing into the lake at top in 1986 and 2015 Landsat images. The red arrow is the 1986 terminus, yellow arrow the 2015 terminus position and purple arrow the tributary.
The Columbia Glacier drains the northwest side of Columbia Icefield into the Athabasca River in Alberta. The glacier in 1964 was 8.5 km long, by 1980 9.5 km long and in 2015 6.2 km long. The glacier drops rapidly from the plateau area over a major ice fall from 2400-1950 m.
The icefall leads to the creation of a series of ogives during the 1960-1990 period. Ogives are annual wave bulges that form at the base of an icefall due to differential seasonal flow velocity. Ommaney (2002) noted that the glacier advanced over one kilometer from 1966 to 1980 the glacier completely filled the large proglacial lake that now exists.
By 1986 retreat had again opened the lake. Tennant and Menounos (2013) examined changes in the Columbia Icefield 1919-2009 and found a mean retreat of 1150 m and mean thinning of 49 m for glaciers of the icefield. They noted that the fastest rate of loss on Columbia Icefield glaciers from 1919-2009 was during the 2000-2009 period.
By 2015 the lake is 4000 m long indicating a 3000 meter retreat from 1986-2015. The rate of retreat has been less since 2004, 300 m, as the glacier approaches the upper limit of the lake basin. When the glacier terminus retreats to this step, the lake will no longer enhance retreat via calving and retreat rates will diminish. A further change is noted in the absence of ogives at the base of the icefall. As the icefall has narrowed and slowed the result has been a cessation of this process. The purple arrow indicates a tributary that joined the glacier below the icefall in 1986 that now has a separate terminus.
|A 2004 image of the glacier indicating the ogive band, and step where the upper limit of the lake likely occurs.|
With time left in the ablation season the snowline is at too high of an elevation to sustain strong flow through the icefall. The retreat is more extensive than the more famous and oft visited glaciers draining east from the icefield Athabasca Glacier and Saskatchewan Glacier.
The above post is reprinted from Materials provided by American Geophysical Union..