May 12, 2013

North Cascade Glacier Accumulation Season Ends

Posted by Mauri Pelto

The typical maximum snowpack accumulation on North Cascade glaciers occurs on May 10. Because the network of USDA Snotel stations are at lower elevations, the best measure of winter accumulation from these valuable long term stations is on April 1. The first image below is the mean April 1 SWE from seven long term stations in the North Cascades. In 2013 April 1 SWE is 10% below the 1984-2012 mean. For the glaciers additional snowpack occurred in April 2013, but about average for April. The accumulation season ended on April 29 and 30th with a final snowfall. From May 3-10 temperatures reached at least 11 C everyday at Lyman Lake which is the station closest to a glacier, just 2 km away. This led to the most rapid start of the melt season since 1998, with 20% of the snowpack at the Snotel stations lost.april 1 swe
April 1 Snowpack Water Equivalent at seven North Cascade USDA Snotel stations (Fish Lake, Harts Pass, Lyman Lake, Park Creek Ridge, Rainy Pass, Stampede Pass, Stevens Pass)
early may ablation
May 1-10 Snowpack Water Equivalent at seven North Cascade USDA Snotel stations from May 1 to May 10.

As the melt season begins the snow lays deeply on Easton Glacier, 15-20 feet deep. When we are making measurements late in the summer how deep will the snow be? We will back in the field for the 30th consecutive summer this year measuring the mass balance of North Cascade glacier, the early indications are that the mass balance will be negative.

From 1984 to 2010 glaciers in western North America mass balance losses have been extensive. The video below indicates the similarity in the cumulative mass balance and trends on a series of glaciers from Alaska, Washington and British Columbia. In each graph the red line is the mean for all glaciers and the blue line the cumulative annual mass balance of the individual glaciers.