December 4, 2019
Wright Glacier, Alaska Snowline and Terminus Retreat
Posted by Mauri Pelto
Wright Glacier in 1984 and 2019 Landsat images. The red arrow indicates 1984 terminus location, yellow arrow 2019 terminus location, pink arrow where the surface slope steepens and red dots indicate the snowline.
Wright Glacier is the largest glacier draining an icefield just south of the Taku River and the larger Juneau Icefield. The glacier accumulation zone is mainly in British Columbia. The glacier filled a lake basin in 1948 as illustrated by the USGS map and NSIDC collection, though the terminus is beginning to break up.
In 1984 the glacier ended at a peninsula in the lake where the lake turns east. This was my view of this glacier during the summers of 1981-1984 from the Juneau Icefield with the Juneau Icefield Research Program. Our bad weather came from that direction so keeping an eye on that region during intervals between weather events was the practice. Here we examine Landsat imagery from 1984-2019 to document the retreat of Wright Glacier and the rise in elevation of the snowline.
In 1984 the lake had a length of 3.1 km extending northwest from the glacier terminus. The snowline in mid-August with a month left in the melt season was at 1150 m at a main glacier junction. By 1993 the glacier had retreated little on the north side of the lake and 200 m on the south side. The snowline in mid-September close to the end of the melt season was at 1150 m. By 2013 the glacier had retreated 900 m and was terminating in a narrower portion of the expanding lake, 30 m/year. The snowline was again at the main junction near 1150 m. In 2018 the snowline on September 16th was at 1450 m with less than 25% of the glacier in the accumulation zone. In 2019 on Aug. 2 the snowline was at 1500 m, likely the highest snowline in the last 70 years, as was the case at nearby Taku Glacier. The high snowlines of recent years has driven an acceleration of the retreat of 1000 m since 2013, 150+ m/year. The glacier has a steeper surface slope 2 km beyond the current terminus front indicating the lake ends either near this point, pink arrow. This could lead to a reduction in the retreat rate, though calving has not been a major factor in retreat of this glacier.
The glacier drains the same icefield as the retreating West Speel and Speel Glacier.
Wright Glacier in 1993 and 2018 Landsat images. The red arrow indicates 1984 terminus location, yellow arrow 2019 terminus location, pink arrow where the surface slope steepens and red dots indicate the snowline.
Wright Glacier in 2013 Landsat images and USGS Topo imagery. The red arrow indicates 1984 terminus location, yellow arrow 2019 terminus location, pink arrow where the surface slope steepens and red dots indicate the snowline.
[…] Fonte/Source: https://blogs.agu.org/fromaglaciersperspective/2019/12/04/wright-glacier-alaska-snowline-and-terminu… […]