September 19, 2013

Toby Glacier Retreat, Purcell Range, British Columbia

Posted by Mauri Pelto

Toby Glacier is in the Purcell Mountains of southern British Columbia, part of the Purcell Wilderness Conservancy Park. Here we examine retreat of this glacier from 1998 to 2014 using Landsat imagery and Google Earth images. The map image indicates the Little Ice Age advance moraine (LIA_on other imagers) at 1960 m, a lower lake (LL)at 2060 m, an upper lake (UL) at 2280 m, the former ELA at a slope change at 2500 m and the recent ELA at 2600-2650 m, all images are oriented with north at the bottom. toby map In the 1998 Landsat image the glacier terminates at the yellow arrow 250 m from the Upper Lake. The snowline in 1998 is at 2650 m and only 25% of the glacier is snowcovered. By 2005 in the Google Earth view from 2005 the glacier terminates 450 m from the Upper Lake. In 2013 the glacier terminates 800 m from the Upper Lake, pink arrow. Yellow arrow marks 1988 terminus for comparison. The snowline is again at 2650 m in 2013 with a month left in the melt season, no more than 20% of the glacier will be snowcovered by the end of the summer. In 2014 on Aug. 18th the snowline is between 2600 and 2650 m with six weeks left in the melt season, purple dots. By the end of the summer little will remain snowcovered. The terminus has retreated additionally from 2013 but not an amount that can be assessed accurately. Typically 60% snowcover is necessary for glacier equilibrium. The result of the substantial negative mass balance that result from the high snowlines and small accumulation zone will be continued retreat. There are significant bedrock areas emerging in the upper portion of the glacier indicating a lack of a persistent accumulation zone indicative of a glacier that cannot survive (Pelto, 2010). A glacier lacking a consistent accumulation zone is experiencing a disequilibrium response to climate and cannot retreat to a point of equilibrium. This is exemplified best in an image from Wildair Photography-image 36. The glacier retreat is like that of Vowell Glacier and Conrad Icefield in the nearby Bugaboos. TOBY GLACIER 1998
1998 Landsat image
2013 Landsat image
toby glacier 2014
2014 Landsat image
toby glacier tiltview
2005 Google Earth view

toby glacier ge
2005 Google Earth view