Chickamin Glacier covers the north slope of Sinister Peak in the North Cascade Range of Washington. The glacier has a valley tongue that descends to an outwash plain. Here we examine retreat of the glacier from 1979 to 2012. The glacier had advanced from 1955-1975, before commencing retreat.
Chickamin Glacier (Tom Hammond)
USGS Map of Chickamin Glacier
In 1979 the glacier terminus was at the pink arrow, several hundred meters beyond a prominent buttress, red arrow, where the glacier turns west. The lowest icefall is indicated by a green arrow. In 1991 the glacier has retreated from the pink arrow, but still is turning the corner beyond the buttress. The lower icefall is still extensively crevassed. By 1998 in a Google Earth image the terminus is outlined with yellow dots and has retreated 230 m from the 1979 position. The lower icefall is still crevassed. By 2005 in a photograph from Tom Hammond (North Cascades Conservation Council), the glacier has retreated to the buttress. in a 2006 Google Earth image the terminus position is indicated by yellow dots, with a retreat of 50 m since 1998. The lower portion of the glacier has limited crevassing. In the 2012 image the glacier terminus no longer reaches the buttress and has retreated 360 m since 1979. We observed exceptional ablation conditions in the North Cascades in 2013 and 2014, which combined with exceptionally low snowpack in 2015 will lead to a continued significant retreat of this glacier. The crevassing in the lowest icefall has declined and is now superficial. All 47 glaciers observed by the North Cascade Glacier Climate Project have been retreating and four have disappeared (Pelto, 2011). This glacier is similar in size and retreat to Boston Glacier and Honeycomb Glacier.
Chickamin Glacier 1979 (Austin Post)
1991 Chickamin Glacier
1998 Google Earth image
2005 Chickamin Glacier (Tom Hammond)
2006 Google Earth image
2012 Google Earth Image
Anderson Glacier was the headwaters of the Quinault River in the Olympic Mountains of Washington. A century ago the glacier was 2 km long, and a half kilometer wide. Retreat of this glacier in the first half of the 20th century exposed a new alpine lake as the glacier retreated 1 kilometer. From 1950-1980 the glacier diminished slowly. From 1959 to 1990 the glacier thinned and retreated from the shore of the lake trapped behind the Little Ice Age moraine. The 1959 picture below was donated to me by Austin Post. Since 1990 the glacier has begun to shrink rapidly. The Google Earth image from 1990, indicates Anderson Glacier has retreated 200 m from the 1959 terminus position near the lake shore, green arrow to the 1990 position, pink arrow. The red arrow indicates a future location of a bedrock outcrop.
1959 Austin Post image
1990 Google Earth image
Investigating this glacier in 1992 we measured its area at 0.38 square kilometers, down from 1.15 square kilometers a century before. Ten years later the glacier had diminished to 0.28 square kilometers, but had thinned even more, leaving it poised for a spectacular change, over the next five years. Large outcrops of rock appeared beginning in 2003 and further exposed in 2005 and 2007 in the middle of the glacier. Note the outcrops in the 2007 image from Kathy Chrestensen. The 2009 Google Earth image indicates the 1990 terminus position, pink arrow, and the fact that there is no longer a ribbon of snow that is even 50 m wide. The snow patches have insufficient size or thickness to be classified as a glacier. The largest outcrop at the red arrow had been beneath the ice in 1990, giving a scale to the thinning. The glacier at this point no longer exists. In 2014 an Eric Hovden image indicates some seasonal snow in the basin, but the thin ribbon of snow has numerous holes in it as well, indicating the thin nature of the remaining snow patches, with a month left in the 2014 melt season.
Kathy Chrestensen Image
2009 Google Earth Image
2014 Eric Hovden image.
This glacier had become a series of small disconnected relict glacier ice patches in 2005 and by 2009 had disappeared. It is not the only glacier that is disappearing, which has led to a visual model for forecasting glacier survival (Pelto, 2010). The key is observed retreat of the margin of the upper portion of the glacier and emerging rock outcrops in the upper part of the glacier where snow should accumulate and be retained through the melt season. If a glacier does not have a significant persistent accumulation zone it cannot survive. Anderson Glacier was not the only glacier feeding the Quinault River, all the others are retreating as well. The result of this glacier retreat is reduced late summer and early fall streamflow, impacting salmon runs at that time of the year. This is primarily the fall Coho, Chum and Chinook salmon and Steelhead summer run. During the spring and early summer runoff increases as snowmelt still occurs, but is not retained in the glacier system.To get a sense of the special nature of this area Out of the Mist is an excellent start
In the 1990’s the North Cascade Glacier Climate Project undertook a study of all the glaciers around Glacier Peak, one century after they had been first observed by C.E. Rusk. This post focuses on one of those glaciers, Dusty Glacier on the Northeast side of the peak.
In 1940 J.B. Richardson of the Forest Service photographed many North Cascade glaciers surrounding Glacier Peak. From 1946-1958 William Long, of the Forest Service surveyed many glaciers throughout the North Cascades (Long, 1955). From 1950-1955 Richard Hubley, University of Washington, completed the first aerial glacier surveys of North Cascade termini, noting the beginning of an advance on many (Hubley, 1956). The USGS in 1960 began an annual aerial photographic survey of North Cascade glaciers that continued up through 1979. In 1984 the North Cascade Glacier Climate Project began annual terminus observations on 47 glaciers and mass balance measurements on ten of these (Pelto, 1996). The average retreat of Glacier Peak glaciers from the LIA to the 1958 positions was 1640 m. Richard Hubley noted that on Glacier Peak glaciers began to advance in the early 1950s, after 30 years of rapid retreat. The advance was in response to a sharp rise in winter precipitation and a decline in summer temperature beginning in 1944 (Hubley, 1956; Long, 1955 and 1956). Ten of the fifteen glaciers around Glacier Peak advanced, including all of the glaciers directly on the mountains slopes. Advances of Glacier Peak glaciers ranged from 15 to 480 m and culminated in 1978. All 11 Glacier Peak glaciers that advanced during the 1950-1979 period emplaced identifiable maximum advance terminal moraines. By 1984, all the Glacier Peak glaciers were again retreating. This retreat has been monitored by NCGCP. Two of the glaciers including Milk Lake Glacier and North Branch Whitechuck Glacier have disappeared.
The depth of snowpack even in Mid-August near the top of the Dusty Glacier is what drives the rapid movement and crevassing of the glacier. In the first image below the red arrow indicates the annual layer, which was 5.7 m thick in 1997. Thew second image has me standing at the terminus in 1994, which was still active even though it was retreating.
Dusty Glacier has the widest most fearsome crevasses of any glacier in the North Cascades. The glacier descends from 2750 m to 2560 m before plunging over an icefall. The glacier levels out in a basin at 2325 m, before descending a second icefall to its current terminus at 1960 m. Dusty Glacier joined with the North Guardian Glacier during the LIA, separating during the 1930’s. During the LIA the glacier advanced to 1465 m. The retreat of this glacier by 1906 when Rusk observed it had been only 400 m. The glacier ended in a basin that was filled with ice, though much of the ice was stagnant. This basin became known as Recession Basin, for the ensuing rapid retreat up until 1946 when the glacier had retreated out of the basin and ended just north of Recession Rock (R) at 2020 m. By 1955 advance was underway, an advance of 130 m had already occurred (Hubley, 1956). The advance ceased until 1967 when it began again, the glacier reaching another 150 m down into the upper part of Recession Basin at 1865 m. The terminus today is very active with extensive crevassing. In fact it is a true icefall. The glacier retreated 220 meters from its 1970’s advance moraine by 1994 during our first visit, 260 m by 1997-1998 at the time of our second visit and 400 meters by 2006 in the Google Earth imagery. The glacier remains quite crevassed though not nearly as much as in 1955. Below the first image is from 1955 taken by Richard Hubley, the second is in 2004, third in 2006 and last in 2008. In each image Recession Rock is labelled with a purple R, the maximum advance of the 1955-1970’s indicated by a orange arrow and the crevassed top of the lower icefall by a green arrow.
Google Earth images from 1998 and 2006 illustrate the retreat over the last 35 years. This glacier has not lost as much area as others around Glacier Peak, such as Milk Lake Glacier which disappeared, Honeycomb Glacier or Vista Glacier. The area loss has been more modest like on Suiattle and Kennedy Glacier.