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| Measuring the snowpack
in a snowpit on Gulkana Glacier. Photo by R. March. |
The 3rd largest spring snowpack in
36 years was measured on Gulkana Glacier on April 19-22, 2001.
The
2001 spring snowpack averaged 1.45 meters water equivalent for the
whole glacier. The snowpack was measured at three elevations on the
glacier and combined to estimate the average. At 1,836 meters
elevation, the snow depth was 4.00 meters and the snow water
equivalent was 1.67 meters. At 1,679 meters elevation, the snow
depth was 3.35 meters and the snow water equivalent was 1.33 meters.
At 1,358 feet elevation, the snow depth was 1.91 meters and the snow
water equivalent was 0.68 meters.
The largest snowpack ever measured was in 1968
when the snow water equivalent averaged 1.57 meters for the whole
glacier. The second largest snowpack was measured in the spring of
1982 when the snow water equivalent averaged 1.55 meters. This
spring’s measurement of 1.45 meters of water equivalent ties for 3rd
place with the snowpacks of 1973 and 2000. Together, the spring snowpacks of 2000 and 2001
are the largest two consecutive snowpacks in the 36-year record.
A large spring snowpack; indeed, even a series of large
snowpacks, is not necessarily a harbinger of the end of the current
slow retreat and a change toward glacier growth. This is because
spring snowpacks at Gulkana Glacier are less variable than summer
melt. Hence, an exceptional spring snowpack can easily be wiped out
by a relatively normal summer melt season. For instance, despite the
large snowpack in 2000, that year ended the melt season with an
annual mass balance slightly below normal. The possible effect of
this year’s large snowpack on the annual mass balance will not be
known until the end of the summer. Visit the Gulkana
Glacier mass balance web page for updates (only a couple times a
year).
The
large snowpack measured on Gulkana Glacier contrasts with USDA,
Natural Resources Conservation Service mountain snow water
equivalent map
for May 1st that shows the snowpack in the area to be about
average.
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| Upper Gulkana Glacier in
spring. Photo
by R. March |
Gulkana
Glacier is located on the south side of the Alaska Range about 10
miles north of Paxson along the Richardson Highway. The USGS has
measured the mass balance on Gulkana Glacier since 1967 as part of a
program to document long-term glacier and climate trends. This
monitoring program includes automated recording of daily air
temperature, precipitation, wind speed, and runoff, as well as
surveying of surface elevation, velocities, and mass balance at
three sites on the glacier, two or three times a year. In general,
the long-term trend is for shrinkage of the glacier.
USGS
News Release on spring snowpack (June 4, 2001)
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