July 22, 2011

Mazama Glacier Retreat, North Cascades, Washington

Posted by Mauri Pelto

Mazama Glacier flows down the north side of Mount Baker, a strato volcano in the North Cascades of Washington. The glacier begins at the summit plateau, 3260 meters, and terminates at the head of Wells Creek 1470 meters. This is a glacier we visit briefly each summer since 1984, but is not a focus of detailed observations. In 2010 we descended from its divide with Rainbow Glacier at 2100 meters to just above the terminus. In the 1970’s the USGS map (top image in sequence) indicates the terminus extended down valley to 1200 meters, this was after a period of advance for the glacier. The glacier advance 450 meters from 1950-1980 (Pelto and Hedlund, 2001). In 1987 we observed the glacier to have begun to retreat. By 1993 the glacier had retreated 200 meters. From 1993 (middle) to 2009 (bottom image) the glacier retreated an additional 750 meters. The rate of retreat has been higher for this glacier because of the loss of the low elevation debris covered terminus that had existed from the 1950’s-1990’s. The glacier is still heavily crevassed and active. The retreat will continue as indicated by thinning near the snowline of the glacier from 1993 to 2009. Note the expansion of the rock outcrop in glacier center (A) from the top image, 1993 to 2009 bottom image. There is also considerably less crevassing near Point A. Also note the stranded glacier ice at Point B and C in 2009. This loss has been due to 7 of the last 10 years having a snowline that rose above the elevation necessary for equilibrium. In 2009 at the end of the summer just 36% of the glacier was snowcovered, 65% needs to be snowcovered for equilibrium. .
In two weeks we will be visiting Mazama Glacier again. Given the heavy 2011 snowpack it is unlikely we will get to see the terminus which should be under avalanche debris.