By Matt Beedle
The longest continuous record of annual length change for a North America glacier now stands at 55 years (1959-2013). In 2013 Castle Creek Glacier retreated 26.3 meters, the fifth largest annual measurement since 1959. Total 1959-2013 retreat now stands at 803 m, with an average annual rate of 14.6 m.
Annual length change of Castle Creek Glacier in meters (top), and cumulative length change in meters (bottom). Both plots include data from 1959 to 2013. A full discussion of the methods used to derive this data set can be found here.
Glacier retreat over decades can be dramatic. For instance, Castle has lost nearly 2 km2 of surface area since 1952, most of it near the terminus. Repeat photography of glaciers typically uses pairs of images separated by multiple decades, revealing this stunning multi-decade change.
Two aerial photographs of the terminus area of Castle Creek Glacier. The 1952 image is from the National Air Photo Library, Natural Resources Canada. The 2011 image includes the near infrared band – vegetation appears red.
In my numerous trips to Castle Creek Glacier over the past six years I’ve been no less moved by the annual changes of a much smaller magnitude, however. The change we see around us is always in relation to scale, proximity and familiarity.
One of my annual tasks at Castle Creek Glacier has been to walk the terminus of Castle Creek Glacier with a high-precision GPS on my pack, mapping the glacier margin and measuring annual change. This annual walk – often times more of a scramble – reveals a great deal. The revelation is in terms of quantifiable glacier retreat, but also a more subjective experience of glacier landscapes and glacier change. John Muir – reflecting on a brief exploration of the terminus area of Baird Glacier, Alaska in 1879 – captures this experience well:
“The whole front of the glacier is gashed and sculptured into a maze of shallow caves and crevasses, and a bewildering variety of novel architectural forms, clusters of glittering lance-tipped spires, gables, and obelisk, bold outstanding bastions and plain mural cliffs, adorned along the top with fretted cornice and battlement, while every gorge and crevasse, groove and hollow, was filled with light, shimmering and throbbing in pale-blue tones of ineffable tenderness and beauty.”
-John Muir, Travels in Alaska
Along with mapping the glacier margin and annual retreat, I’ve had the opportunity to observe and photograph Castle Creek Glacier’s annual changes. With each visit I’m astonished by the volume loss, change in form and alteration in character that is quantified blandly (yet importantly!) in our measurements of change. These repeat photographs, dating back to 2007, don’t show the marked change of repeat photos separated by decades. They do, however, catalog the more experiential understanding of the annual glacier change of Castle Creek Glacier. If you’re fortunate enough to have a ‘local’ glacier, make an effort to pay it a visit each year – you will be richly rewarded.