columbia icefield glacier retreat – From a Glaciers Perspective

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.

In 1986 Landsat imagery the lake is 1000 m long. A 2004 Google Earth image indicates a step in elevation that is 500 m from the terminus. Glacier elevation lags the basal elevation change; hence the end of the lake is between 500 and 1000 m from the 2004 terminus. 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. The current terminus is still active with crevassing near the active front. The snowline in both August 2015 and July 2016 is close to 2800 m. A more detailed look at the 2016 mass balance conditions in the region just west of the glacier suggest Columbia Glacier had a more negative balance than in the Columbia River basin. 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.

A 2004 image of the glacier indicating the ogive band, and step where the upper limit of the lake likely occurs.

Sentinel image indicating the snowline at 2750-2800 m m on July 27, 2016.

The Saskatchewan Glacier is a major outlet glacier of the Columbia Icefield in Alberta. The glacier is a 12 km long valley glacier draining east from the icefield that ends within 6 km of Highway 93. This accessibility has led to numerous examinations of this glacier. The glacier is not as famous as its neighbor to the north Athabasca Glacier which the same highway brings a visitor to a parking lot at the margin of the glacier. I visited the glacier twice in the 1980’s, this post is mainly an examination of its retreat since then. A series of photographs from Parker’s Ridge in 1924, 1985, 2011 and 2014 provide a good view of the change in the glacier and the development of a lake that was at the margin and is now separated from the glacier. The first two images are from a report from Dan Smith, Univ. of Victoria BC on the dendrochronology of this glacier, the last image is from Ben Pelto in September of 2014. Interestingly Dan Smith found after a channel erosion event a buried forest that dated to 2800 to 3200 years ago. Indicating that the glacier is now shorter than in had been for at least that long. The lake has expanded in width and length even since 2011.

Ben Pelto image 2014

The terminus when I first visited the glacier in 1983 was just at the western margin of the lake that had developed at the glaciers terminus, first image below. The recession of the glacier since the late 19th century is similar to that of other glaciers in the area and was greater than 2 km. middle image from USGS. Bolch et al (2010) identified a 25% loss in glacier area in Alberta from 1985 to 2005, indicating the retreat goes on regionally. The third image is of the trimline above the glacier marking the height of the glacier a century before.

Below is a series of Landsat and Google Earth images from 1986, 2001, 2004 and 2012 in that order. The position of the terminus in the Landsat and Google Earth images rely on a few specific locations for reference. The outlet of the lake has remained the same over the last 25 years and is marked by an O. A ravine angled to the terminus in the 1980s from the north, yellow arrow. There is a pair of deep ravines on the south side that a pink arrow is between. The purple image indicates a tributary and the orange arrow the snowline. The glacier has retreated 700 meters from 1983 to 2012. The change in terminus position with respect to the lake is particularly evident. The tributary from the south has also retreated, purple arrow. The snowline in these images which are not at the end of the summer are at 2500 m, with the snowline rising to 2600 to 2700 m m by summer’s end. This is a higher snowline than reported for the glacier in the 1950’s, (Ommaney, 2002).

A close up view of the terminus in Google Earth indicates a series of recessional moraines that have formed during the retreat, green arrows, these typically form during the winter when the terminus can advance a few meters due to the lack of ablation. The lower portion of the glacier lacks crevassing and has numerous incised streams which suggests the retreat of 25-30 meters/year will continue. This is a slower rate than on the Columbia Glacier that drains east from the icefield.