Temporal Snowcover Change

The health of a glacial system is a direct function of both short-term weather and long-term climate conditions. Long-term changes in mass balance are generally not easily discernible from one year to the next. It is only when comparing multi-year data that these changes can be detected. Short-term changes are due to local weather patterns and may easily be detected when comparing the conditions at a site from one year to the next.

The Juneau Icefield Research Program has been monitoring the mass balance of the Juneau Icefield for the past 50 years. This data quantifies the long-term climatalogical changes. However, it is often useful to understand the short-term changes from one year to the next. The series of photographs presented here document those changes with respect to the amount of snowcover. While qualitative in nature, these comparative photographs nevertheless provide valuable insight into the changing conditions on the Juneau Icefield.

Note to Other JIRP Members:
If you have photos similar to these, and if you would like to contribute to this photo series, please let me know so that I can include them here.

~ July 8, 1988	~ July 6, 1996	July 6, 1999
This view is looking east toward the Juneau Icefield from a small pond along the Lemon Creek Trail. Compare the snowcover on the mountains in the background.

~ July 6, 1996	July 6, 1999	July 11, 2000
View to the southeast toward the Ptarmigan Glacier (out of view) and the Ptarmigan Valley. Notice the stream in the 1996 photo that is completely buried by snow in the 1999 and 2000 photos.

2^nd week of July, 1988	2^nd week of July, 1993	July 11, 2000
These photos shows the terminal area of the Lemon Glacier (bottom of photo) and the terminus of the Thomas Glacier in the upper half of the photo. Significant changes are evident at the terminus of the Lemon Glacier.

July 30, 1999	July 12, 2001
This is the head of the Lemon Glacier, showing the perennial supraglacial lakes (Lake Lynn in the foreground, and Lake Linda in the background). Notice the change in snowcover on the ridge behind lake Lynn, and on the slopes of Cairn peak behind Lake Linda.

July 30, 1999	July 12, 2001
The Dead Branch of the Norris Glacier, directly east of the Lemon glacier, has been significantly thinning for the past 30 years. These marginal lakes don't change much from year to year, however it is interesting to note the snowcover changes on the mountainside behind them.

Mid-July, 1988	Mid-July, 1990	Mid-July, 1999	July 25, 2000	July 18, 2001
This series of photos show the changing snowcover at Camp 10 and Taku B, the peak in the background behind camp. While the general trend is one of decreasing snowcover on Taku B, it is interesting to note that there was slightly more snow in the immediate area of camp in 1999 than there was in 1990. This is most likely due to different winter wind patterns which resulted in more drifting around the building in 1999. However, the marked increase in snowcover in July 2000and 2001 was seen all across the Icefield, from Camp 17 to Atlin.

Mid-July, 1993	Mid-July, 1997	Mid-July, 1998	Mid-July, 1999	July 29, 2000	July 18, 2001
This nunatak is located approximately 2 kilometers south of Camp 10. As in the previous photos of Taku B, this area has also received more snow in the past several years, as compared to 1997. Notice the large slab avalanche that occurred in 1993.

3^rd week of July, 1997	3^rd week of July, 1998	July 27, 2001
This small nunatak is at the junction of the Taku Glacier and its Northwest Branch. Note the prominent change from 1997 to 1998, with the opening of a large crevasse. By 2001, retained accumulation had once again closed the crevasse, and indeed had covered much of the exposed rock.

~ July 10, 1987	July 28, 1989	~ July 31, 1992	July 31, 1999	August 1, 2000	July 21, 2001
The snowcover here at Camp 9 has varied considerably since 1987. As you can see, the building was nearly engulfed in 1987. It was then completely buried and lost until 1989, when half of it was exposed. By 1992 the snowcover was such that the building was once again completely visible. The snowcover had increased so much by 2001 that we had to use GPS to locate the survey benchmark and dig it out. Although the camera angles of these photos are slightly different, they nevertheless demonstrate the significant snowcover change in this area of the Juneau Icefield. Credits for the 1987 photo go to The Juneau Icefield: A Different Perspective.

~ August 10, 1986	Mid-August, 1988	Mid-August, 1996	August 2, 2000	August 1, 2001
The area around Camp 18 also has seen dramatic changes in the past 12 years. Here you can see in the left photo that the snow completely surrounded the generator shed in mid-August, 1986. A nearly identical photo in mid-August, 1988 shows the snow somewhat retracted, while the 1996 photo shows the snow well behind the shed. By August, 2000 the snow level had once again increased, reflecting higher snowfall during winter '99-'00. Credits for the 1986 photo go to The Juneau Icefield: A Different Perspective.

Mid-August, 1990	Mid-August, 1998	August 13, 2000
The snowcover change in the Camp 18 area, as shown in the three previous photos, is also reflected in changes to the glaciers in the Gilkey Trench, 600 meters below the camp. These photos show the Little Vaughan Lewis Icefall as it enters the Trench. Notice in the 1990 photograph that the Icefall is connected to the Gilkey Glacier. By the summer of 1997 the lower third of the Icefall had thinned to the point that several small holes had developed, exposing subglacial caves and waterfalls cascading over the rocks underneath the ice. In mid-August of 1998, the lower portion of the Icefall experienced a catastrophic collapse of the ice. This was due to the thinning of the ice in conjunction with the expansion of the subglacial, water-carved caverns. Eventually, the ice could no longer support itself, which then avalanched, leaving the Icefall nearly fully detached from the bottom of the Gilkey Trench. By August, 2000 the Icefall was completely detached from the Gilkey Glacier

Mid-August, 1988	Mid-August, 1996
Here's another comparison set that shows the snowcover around the generator shed at Camp18. These photos were taken from the hill behind the shed and look to the west. The red line in the the right-hand photo delimits the mid-August, 1988 snow level.

Mid-August, 1988	Mid-August, 1999	August 2, 2000	August 12, 2001
Looking south from Camp 18 to the northern slope of Mammary Peak. The highly fractured ice is the upper portion of the Vaughan Lewis Icefall. Snowcover change is evidenced by the newly-exposed outcrops on the skyline ridge of the peak.

Late August, 1990

Late August, 1996

The Cathedral Glacier, located approximately 50 kilometers south of Atlin, British Columbia,
has undergone significant downwasting since 1990. Occupying a mountain cirque, the glacier
has retreated out of the terminal lake shown here. The ice seen on the right-hand side of the
1990 photo is a stagnant remnant from when the main body of the glacier extended further
down valley. Although it is stagnant, the 1990 photo shows that it is still physically attached to
the Cathedral Glacier by a thin veneer of ice. By 1996 this ice had disappeared, leaving the
stagnant patch of ice now completely detached from the main glacier. This patch has also
retreated and downwasted as evidenced by the stream that undercuts it.

Late August, 1996	Late August, 1997
This is the main Cathedral Glacier, which is out of view in the previous two photographs. Here you can see the small detached stagnant patch of ice in relation to the glacier itself. Notice too the difference in snowcover between the two photos.

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