July 3, 2011

Spectacular Retreat of Melbern Glacier, British Columbia

Posted by Mauri Pelto

The combined Melbern and Grand Pacific Glacier with a length of 55 km and width of 2-5 km, is a large valley glacier draining from the Saint Elias Mountains near the British Columbia-Alaska boundary. The glacier separates into two distinct glacier termini at Grand Pacific Pass. One of the tongues, Melbern Glacier, flows 20 km northwest ending in . Grand Pacific Glacier flows southeast to Tarr Inlet of Glacier Bay, just across the Alaska boundary. The Melbern Glacier turns north and ends in Lake Melbern. Lake Melbern began to form around 1979 as noted by Clague and Evans (1993). By 1986 the lake had expanded greatly as the former tributary to Melbern Glacier, Konamoxt Glacier had separated, and a 7km retreat of Melbern Glacier from the Konamoxt Glacier had ensued, first image from their paper. Clague and Evans (1993) in the second image further note that the ice dam of the Konamoxt Glacier that blocks Melbern Lake had broken by 1991 and the lake level had dropped. The retreat has continued unabated up through 2009. Here we use a series of Landsat images and one Google Earth Image to illustrate the retreat up to 2013. The first is a 1986 Landsat Image, K=Konamoxt and M=Melbern. In this image Konamoxt still blocks Melbern Lake and Melbern Glacier terminates adjacent to another tributary from the south, orange marks the 1986 terminus of both glaciers. The second image is a false color Landsat image from 2001. Konamoxt Glacier extends partly across the lake but not completely. The lake to the northwest of Konamoxt is filled with icebergs. Melbern Glacier has retreated 3 km since 1986. The third image is the Google Earth image also from 2001 showing the 1986 margin as well, in orange and the 2007 terminus in purple. The fourth image is from 2007, indicating a 1.5 km retreat of Melbern Glacier in the last six years. By 2013 the retreat is 2.25 km since 2001 and 5.25 km since 1986. Konamoxt Glacier no longer reaches Lake Melbern proper and is beginning a retreat up its own valley. The lake itself has changed color and lost its fleet of icebergs. The last image is from July 2013 and Lake Melbern is now 20 km long and still expanding. melbern glacier 2013
Melbern Glacier is following the same pattern as nearby Yakutat Glacier and Grand Plateau Glacier. The lower 3 km of the glacier appears stagnant. However, there is a moraine band 10m km above the terminus that has shifted down glacier 1000-1500 meters from 2001 to 2007 as seen in images from those dates below. The green line indicates the moraine position in 2007. This indicates significant flow at this point. Thus, it is evident that retreat will continue on Melbern Glacier, but should slow as either the lake basin is left behind, or the moraine band is approached