June 2, 2011

Columbia Glacier Past, Present and Future

Posted by Mauri Pelto

For the last 27 years the first week of August has found me on the Columbia Glacier in the North Cascades of Washington. Annual visit pictures up to 2008 can be seen at bottom of post.

This is the lowest elevation large glacier in the North Cascades. Columbia Glacier occupies a deep cirque above Blanca Lake and ranging in altitude from 1400 meters to 1700 meters. Kyes, Monte Cristo and Columbia Peak surround the glacier with summits 700 meters above the glacier. The glacier is the beneficiary of heavy orographic lifting over the surrounding peaks, and heavy avalanching off the same peaks. Over the last twenty seven years the annual mass balance measurements indicate the glacier has lost 14 meters of thickness. Given the average thickness of the glacier of close to 75 meters in 1984 this represents a 20% loss in glacier volume. To compensate for this loss would require 16 million cubic meters of snow water equivalent. During the same period the glacier has retreated 135 meters, 8% of its length. Most of the loss of volume of this glacier has been through thinning not retreat. The glacier remains thick, but cannot survive current climate, which has left the glacier without any snowpack by the end of the summer in five of the last 10 years. This lack of persistence is the sign of a glacier than cannot survive (Pelto, 2010). We can look at the past of the Milk Lake Glacier near Glacier Peak in 1988, 30 miles northeast of Columbia Glacier, and the present of Milk Lake without the glacier. The green arrow points to the forming lake filled with by both icebergs and the still evident glacier. The upper margin of the glacier is indicated by the red arrow. The lake in 2009 still is a nice jade green from glacier erosion. This lake will slowly become more azure in color as no new glacier sediment is added.

In the same respect we can look at the past and present of Columbia Glacier comparing a 1986 and 2010 photograph. The blue arrows indicate moraines that the glacier was in contact with in 1986, and now are 100 meters from the glacier. The green arrow indicates the glacier active ice margin in 1986 and again that same location in 2007 now well off the glacier. The red arrow indicates the same location in terms of GPS measurements, this had been in the midst of the glacier near the top of the first main slope in 1986. In 2007 this location is at the edge of the glacier in a swale.

To look to the future Jill Pelto, my daughter, painted the glacier as it was in 2009 (top) and then what the area would like without the glacier in the future, at least 50 years in the future (middle), and Jill at the sketching location (bottom), turned 180 degrees to view Blanca Lake. The lake is colored by the glacier flour from Columbia Glacier to the gorgeous shade of jade.

Clearly the area will still be beautiful and we will gain two new alpine lakes with the loss of the glacier. After making over 200 measurements in 2010 we completed a mass balance map of the glacier. This summer we will be back again for the 28th annual checkup.