August 31, 2012
The 2011/12 winter was a La Nina winter that led to the typical La Nina excellent snowpack. By May 1 the 2012 snowpack was one of the top five snowpacks of the last 30 years. After an average May and a cool June, the snowpack was still high on July 1. July and August tied 1998 and 2009 as the warmest over the last 30 years in the North Cascades, leading to rapid glacier melt. The result with four to six weeks left in the melt season is that glaciers are going to finish the year with a mix of glaciers that gained and lost mass despite the good winter. The duration and intensity of melt if sustained above average will leave most glaciers with a loss.
We started on Columbia Glacier, a low elevation cirque glacier fed by tremendous avalanching, that had received considerable snow accumulation from avalanching off the slopes of Columbia Peak. Our measurements found an average snowpack of 4.2 meters at the start of August. The glacier lost 9 feet of snow pack during the month of August. The glacier will likely finish the season with a small positive balance, unless September is significantly above average in temperature.
We were joined by Oliver Grah, Nooksack Indian Tribe Water Resource Manager in assessing Rainbow and Sholes Glacier. Average melt and runoff was 11 cm/day from Sholes Glacier. On Rainbow Glacier snowpack was well above average on the lower half of the glacier below 1600 meters, but had very little increase with elevation and only average accumulation at the top of icefall at 1800-2000 m. The Rainbow Glacier will likely have a positive mass balance. Sholes Glacier had an an average snowpack of 3.5 m in early August, and 1.5 meters by the end of August. This will likely lead to a close to equilibrium balance.
On Lower Curtis Glacier the south facing terminus does not retain snowpack well, and is more sensitive to summer conditions. As a result the high ablation of July and August had led to rapid melt of the terminus seracs and icefall. We were able to get beneath the glacier, where the rapid melting has led to the glacier being off its base in many areas. The glacier will finish the year with negative mass balance, regardless of September weather.
The next stop was Easton Glacier where Oliver Grah, his assistant Jezra Beaulieu, Western Washington U., Peter Sinclair videographer joined us. The lower kilometer of the glacier was mostly blue ice already by August 12. By the end of August little snowpack remained below the 2000 meter bench. This glacier does not receive avalanching and again is more susceptible to summer conditions. Like Lower Curtis Glacier this glacier will finish the season with a negative mass balance. Snowpack remaining rose from 3.2 m at 2000 m to 5.7 meters at 2500 meters in mid-August. A detailed survey of crevasse with, length and depth that will be repeated will hopefully be able to identify glacier velocity changes going forward.
On Mount Daniels we examined Ice Worm Glacier, Daniels and Lynch Glacier. The snowpack on these glacier the furthest south and east that we observe was the best of anywhere. Ice Worm Glacier is an avalanche fed small cirque glacier that had excellent snowpack. Daniels Glacier for the first time since 1999 was fully snowcovered even on August 16th. Lynch Glacier had good snowpack as well with the blue ice area limited to less than 10% of the glacier. All three of these glaciers will finish the year with a positive mass balance.
Mauri Pelto, Tom Hammond, Ben Pelto and Jill Pelto