mount baker glacier runoff – From a Glaciers Perspective

Mass balance, terminus and supra glacial stream assessment are illustrated in the video, Filmed by Mauri Pelto, Jill Pelto, Melanie Gajewski, with music from Scott Powers.

This is the story of the annual monitoring of Easton Glacier, Washington. We have been monitoring Easton Glacier on Mount Baker, a stratovolcano in the North Cascade Range, Washington since 1990. Each year we survey the terminus position, measure its mass balance, assess crevasse depths and map surface elevation on a transect across the glacier. In 1990 Easton Glacier was in contact with an advance moraine built from the late 1950’s- 1980’s. The advance moraine is noted in the 2015 Washington DNR Lidar image of the terminus area by black arrows. The green arrows indicate the recessional moraine from the winter of 2015. Red arrows indicate the Little Ice Age lateral moraines Railroad Grade (RG) to the west and Metcalfe Moraine (MM) to the east. From 1990-2017 the glacier has retreated 370 m, including 65 m in the last three years. The second Lidar image indicates the transect where the surface elevation is mapped, red line. This is close to 2000 m in elevation, and in a good snow year retains snowpack and in most recent years has lost its snowpack (note paired image below). In 2015 the worst year, the snowpack had been lost by the end of July. Note the comparison of the 2017 transect snowpack and 2015 lack of snowpack.

Washington DNR Lidar image of Easton Glacier , black arrows indicate 1980’s advance moraine, green arrows 2015 winter moraine and red arrows the Little Ice Age lateral moraines. Blue dots indicate the glacier margin.

Washington DNR Lidar image of Easton Glacier. Blue dots indicate the glacier margin. Red line the cross glacier profile.

A view along the cross glacier profile at 2000 m in early August of 2015, snowpack gone already and in 2017 with 2 m of snowpack remaining.

More than 5000 measurements of snow depth and melt have been completed illustrating the glacier has lost 16.6 m of water equivalent thickness, over 18 m of thickness from 1990-2016. For a glacier that averaged 70 m in thickness in 1990 this is ~25% of the volume of the glacier gone. The glacier has not maintained sufficient snow cover at the end of the summer to have a positive mass balance, this is the accumulation area ratio. The mass balance and terminus data is reported annually to the World Glacier Monitoring Service. The area lost in the terminus region due to the retreat has been 0.22 km2.

The glacier has also slowed its movement as it has thinned, evidenced by a reduction in number of crevasses. In the lowest icefall Jill Pelto has surveyed the crevasse depths finding a mean depth 20 m and a maximum depth of 32 m. This glacier supplies runoff to Baker Lake and its associated hydropower projects. Our annual measurements here and on Rainbow Glacier and Lower Curtis Glacier in the same watershed provide a direct assessment of the contribution of glaciers to Baker Lake. The glacier is also adjacent to Deming Glacier, which supplies water to Bellingham, WA. The Deming is too difficult to access, and we use the Easton Glacier to understand timing and magnitude of glacier runoff from Deming Glacier. Deming Glacier has retreated a greater distance during this period, 705 m, but has lost a similar area.

Annual terminus survey in 2015 terminus exposed to melting by early July. In 2017 terminus being exposed first week in August. Taken from same location.

Crevasses measurement in lower icefall and on the cross profile. In both cases crevasse depth is measured, on the profile 2017 winter snow depth remaining measured.

Easton Terminus viewed from our benchmark location just beyond 1980’s margin. Tree in foreground is over 50 years old.

2017 Field Season Video

For the thirty fourth consecutive summer we headed into the field to monitor the continued response of North Cascade glaciers to climate change. In 1984 when I began this program we selected 10 key glaciers to monitor. Two of these have now disappeared. All the glaciers have retreated extensively and lost considerable volume. The mass balance loss is 19 m of water equivalent thickness, which is over 20 m of ice thickness loss on glaciers that averaged less than 75 m thick. This is significant with 25-30% of their entire volume lost. This project continues to monitor glacier loss and the runoff they provide. We also complete an annual inventory of ice worms on Sholes Glacier and mountain goats on Ptarmigan Ridge region. In 2017 our key project was a continue partnership with the Nooksack Indian Tribe monitoring glacier melt and runoff in the North Fork Nooksack River basin. We have not yet had the chance to determine the daily glacier discharge and the resultant contribution to the North Fork Nooksack River. The dry conditions of August certainly will lead to many days with more than 40% of the flow coming from glacier melt as was the case in 2015.

The snowpack on April 1st snowpack was 110% of normal, by June 1st, the snowpack was trending down steeply, but
remained well above the last four years and similar to 2012. Summer turned out to be the driest on record in Seattle and

tied for the warmest for the June 21-Sept. 22nd period (KOMONews). In the mountains the overall melt season temperatures for May 1 through Sept. 30th was 0.15 C cooler than 2015 values, due to a cooler spring. The most striking feature of the field season was the forest fire smoke largely from British Columbia that obscured views most days.

Of the glaciers observed one had a significant positive balance, one a slight positive balance-essentially equilibrium and seven had negative mass balances. The two glaciers with the most positive balance were the Sholes and Rainbow Glacier, adjacent glacier on the north side of Mount Baker. The nearby Mount Baker ski area reported 860 inches of snow in 2017, significantly above average. Compared to other locations in the range this winter snowfall was a positive anomaly, that also was observed on the nearby glaciers. The snow water equivalent in multiple crevasses on Rainbow Glacier at 2000 m in early August was 3.8-4.1 m. On both Easton and Rainbow Glacier the mass balance gradient was steeper than usual. On Rainbow Glacier the mass balance was -3 m at 1500 m, 0 at 1700 m and +2.5 m at 200 m as summer ended. We also observed terminus retreat on every glacier. Retreat averaged 12 m in 2017, lower than in 2015 or 2016. More striking than retreat in some cases is thinning that reduces slope and frontal thickness. On Lower Curtis Glacier the terminus seracs are 15 m shorter than two years ago. On Columbia Glacier the lowest 200 m of the glacier has a slope that has declined by 5 degrees in the last three years and the glacier terminus has retreated 60 m in two years.