glacier retreat canada – From a Glaciers Perspective

Comparison of the Cummins Glacier from 1986 to 2015. Purple arrows indicate upglacier thinning and disconnection. Red arrow indicates 1986 terminus position. Note the lack of snowcover in 2015.

The Cummins Glacier is part of the Clemenceau Icefield Group in the Rocky Mountains of British Columbia. The Cummins Glacier via the Cummins River feeds the 430 square kilometer Kinbasket Lake, on the Columbia River. The lake is impounded by the 5,946 MW Mica Dam operated by BCHydro. Jiskoot et al (2009) examined the behavior of Clemenceau Icefield and the neighboring Chaba Icefield. They found that from the mid 1980’s to 2001 the Clemenceau Icefield glaciers had lost 42 square kilometers, or 14% of their area. Tennant and Menounos (2012) examined changes of the Rocky Mountain glaciers and found between 1919 and 2006 that glacier cover decreased by 590 square kilometers, 17 of 523 glaciers disappeared and 124 glaciers fragmented into multiple ice masses. Here we examine the Landsat images from 1986-2015 to illustrate that Cummins is one of those fragmenting glaciers.

Cummins Glacier on the western side of the Clemenceau Icefield shares a connection with Tusk Glacier.

In 1986 Cummins Glacier had a joint terminus with the main southeast flowing branch and the west flowing branch terminating at the red arrow. The glacier also had a substantial connection, purple arrow, with Tusk Glacier that flows east terminating northeast of Tusk Peak. There are other connections with other high elevation accumulation areas, purple arrows. In 2013 and 2014 Cummins Glacier had less than 20% retained snowcover by the end of the melt season. Typically 50-65% of a glacier must be snowcovered at the end of the summer season to be in equilibrium. In 2015 conditions were even worse with no retained snowcover, in fact there is only minor patches of retained firn from previous years. The lack of a persistent accumulation zone indicates a glacier that cannot survive the climate conditions (Pelto, 2010). By 2015 a proglacial lake had formed at the terminus that is 500 m long, representing the retreat during the thirty year period. The west flowing portion of the Cummins has detached from the larger branch. The connection to Tusk Glacier is nearly severed, and in terms of flow is effectively ended. Retreat of the margin higher on the glacier is also evident at each purple arrow. Tusk Glacier is no longer connected to Duplicate Glacier, and has retreated to the north side of Tusk Peak. The dominant change in Cummins Glacier has been thinning, it should now be poised for a more rapid retreat.

The result for Kinbasket Lake of the loss of the collective large area is a reduction in summer glacier melt and summer glacier runoff. The annual runoff which will be dominated by annual precipitation would not change just because of the glacier loss as noted in cases like the Skykomish Basin (Pelto, 2011) and on Bridge River (Stahl et al 2008).

2013 Landsat image indicating 20% retained snowcover with a month left in the melt season.

Landsat image 2014 about 25% retained snowcover with three week left in the melt season.

Google Earth Image of Cummins Glacier location to Kinbasket Lake.

The Waputik Icefield, near the Icefields Parkway, north of Banff, Alberta straddles the continental divide. The Waputik outlet “Liiliput” Glacier is a 3 kilometer long outlet draining east into Hector Lake and the Bow River. This glacier drains the north side of Lilliput Mountain, and is just southeast of Balfour Glacier, which it merged with in the late 19th century. That is why the glacier lacks a proper name, it was part of the Balfour Glacier when named. The Lilliput Glacier has retreated 2.3 km from its maximum. The Balfour Glacier with which it was joined retreated at a rate of 10 meters per year at the end of the 19th century and 40 meters per year up to 1945, by 1945 the glaciers had separated (Ommaney, 2000). From 1945 to 1970 limited retreat occurred on either Lilliput or Balfour Glacier.
This Lilliput Glacier is now continuing to retreat, 320 meters since the 1970 picture of the glacier was taken. In 1970 the glacier still has a single terminus in the valley and ended a short distance above a steep bedrock slope. By 1994 the glacier has developed two termini and has retreated 200 m from the 1970 position. The 2002 terminus in this Google Earth image has retreated an additional 100-200 meters depending on location along the front. A closeup of the terminus area indicates limited crevassing, indicating limited movement and continued retreat. The supraglacial stream (winding stream channel on glacier surface) that is visible has downcut a considerable channel, this too indicates limited movement. An active glacier terminus would closeup such a channel seasonally as movement continued and meltwater flow ceased. The glacier in 2002 still has an accumulation zone at the head of the glacier. For a glacier like this to be in equilibrium it needs at least 50% of its area to be snowcovered at the end of the summer, this percentage is the accumulation area ratio. In the image below the lines are annual accumulation horizons exposed in the glacier ice. This indicates a region of the glacier that is consistently exposed to ablation today. Only 40% of the glacier is snowcovered above this point. This indicates how little of the glacier is a consistent accumulation zone today. Without a consistent accumulation zone the glacier cannot survive.