Spatial variability
Studies of the spatial variability of snow stability and the
snowpack have been one of the core themes of research at Montana
State University's Earth Sciences Department since the 1960s.
The National Avalanche Center is cooperating with researchers
from Montana State University and the Swiss
Federal Institute for Snow and Avalanche Research to continue
to investigate spatial variability at a number of spatial and
temporal scales.
Charles Bradley investigates the spatial variability
of slopes in the Bridger Range in the 1960s utilizing his resitograph
(photo by Dr. John Montagne)
Spatial variability at the mountain range scale
Spatial variability at the mountain range scale is extremely
important for regional avalanche forecasters, who typically try
to predict snow stability over large areas. In spite of this,
little formal research on spatial variability at the mountain
range scale has been conducted, though experience has demonstrated
that the snowpack clearly varies with known parameters like elevation
and aspect. In the mid-1990s we worked on a project investigating
the spatial variability of snowpack and snow stability measures
in the Bridger Mountains over an area of several hundred square
kilometers. The research utilized six teams of observers who were
shuttled around in helicopters to collect data from over 70 snow
pits in a given day. The results demonstrated that statistically
significant patterns of snow stability exist, and that these patterns
can change through time. During sampling, more unstable conditions
existed at higher elevations and more northerly aspects. This
work formed the basis for Karl Birkeland's dissertation research
[download the dissertation here,
but realize it is a big 14 MB file!] and was presented at the
International Snow Science Workshop and published in this
article the Journal of Glaciology.
Spatial variability at the slope scale
The snowpack varies widely over short distances, and knowledge
of these variations is critical for forecasting avalanches. Natural
avalanches are believed to release from zones of localized weakness,
while triggered avalanches can be released more easily from relatively
weaker areas. All of this has implications for the placement of
explosives for avalanche mitigation work and the positioning of
snow pits to accurately assess the avalanche conditions while
traveling in the backcountry. Since the late-1980s we have been
interested in the spatial variability of snowpack properties at
the slope scale. A project from 1988 to 1990 utilizing the digital
resistograph formed the basis for Karl Birkeland's MS work, which
was summarized in this article in
the Journal of Glaciology. The results demonstrated that average
snow strength was relatively high in areas of wind drifting and
relatively low in areas with a thin snowpack or areas over the
top of rock outcrops.
The digital resistograph (left), a tool developed
by Tim Dowd and Bob Brown in the mid-1980s, was used for slope
scale spatial variability research from 1988 to 1990 (right).
Spatial variability on uniform slopes
In the late 1990s Chris Landry, a MS student in Montana State
University's Earth Sciences Department, worked with the National
Avalanche Center to investigate variations in snow stability at
the slope scale using the Quantified Loaded
Column Test he developed. His research involved doing 10 QLCT
tests in each of five locations on 30 by 30 m planar, wind-protected
slopes with a relatively uniform substrates. His results showed
that about a third of all of his snowpits could not reliably predict
the snow stability of even these small plots. The reasons for
these variations are not entirely clear, but are being further
investigated. Complete results are reported in a paper
for the 2002 International Snow Science Workshop, and in an article
for Cold Regions Science and Technology. Or, you can look at his
whole thesis here.
Spatial variability through time
The National Avalanche Center is currently working on a project
looking at changes in slope scale spatial variability through
time. We hope that this project might improve avalanche forecasting
by enhancing our understanding of the conditions that lead to
more or less variable snowpack conditions on slopes. This project
will utilizes the SnowMicroPen and
stability tests to look at the spatial variability on parts of
uniform slopes through time. Some of the ideas for this project
came out of our work with Chris Landry, and were presented at
the 2002 International Snow Science Workshop in this
paper, and some preliminary results are reported in this
article for the Annals of Glaciology. This research is being
funded by a National Science Foundation Grant awarded to Kathy
Hansen, Karl Birkeland, John Borkowski and Ed Adams. In addition
to Montana State University, cooperators on the project include
the Center for Snow and Avalanche
Studies, and the Swiss Federal
Institute for Snow and Avalanche Research.
The project also continues to investigate slope scale spatial
variability of snow stability and snow structure. Spencer Logan
did his MSc on this project, investigating spatial and temporal
changes in shear strength and stability using the shear frame
test. He presented this work at the International Snow Science
Workshop in Jackson Hole in 2004. You can check out his ISSW paper
here, or his entire thesis
here.
Eric Lutz has also been working on this project as part of his
PhD work at Montana State University. His focus has been on analyzing
and interpreting the data from the SnowMicroPen (SMP). You can
check out his ISSW paper here.
Another person working on the project from January, 2004 to June,
2005 has been post-doctoral researcher and assistant research
professor Kalle Kronholm. Kalle has been involved in all aspects
of the project, helping to organize field work and data, assisting
with advising students, programming analysis tools for the data,
and working on a cellular automata model to supplement our field
data collection. You can read his ISSW paper here,
and he has several other papers in the works (as of summer, 2005).
Our project included lots of field work and moving (literally)
tons of snow! Here Kalle Kronholm works on a manual profile while
Spencer Logan prepares for shear frame tests and Eric Lutz (background)
conducts SnowMicroPen measurements.
References and associated Nat'l Avalanche Center papers on
spatial variability:
Birkeland, K.W., K.J. Hansen, and R.L. Brown. 1995. The spatial
variability of snow resistance on potential avalanche slopes.
J. Glaciology 41(137), 183-190. [Abstract]
[Article]
Birkeland, K.W. 1997. Spatial and temporal variations in snow
stability and snowpack conditions throughout the Bridger Mountains,
Montana. Ph.D. Dissertation, Department of Geography, Arizona
State University, Tempe, Arizona. 205 pp. [Warning! This is a
big file, so you'll want a fast connection! PDF
(14 MB)]
Birkeland, K.W. 2001. Spatial patterns of snow stability throughout
a small mountain range. Journal of Glaciology 47(157),
176-186. [Abstract] [Article
(3.6 MB)]
Birkeland, K.W. and C.C. Landry. 2002. Changes in spatial patterns
of snow stability through time. Proceedings of the 2002 International
Snow Science Workshop, Penticton, BC, Canada, 482-490. [Article]
Birkeland, K., K. Kronholm, M. Schneebeli, and C. Pielemeier.
2004. Changes in the shear strength and micro-penetration hardness
of a buried surface hoar layer. Annals of Glaciology 38,
223-228. [Abstract] [Article]
Birkeland, K.W. and K. Kronholm. 2004. A comparison of the spatial
patterns of penetration resistance of slabs and weak layers. Proceedings
of the 2004 International Snow Science Workshop, Jackson Hole,
Wyoming. [Extended abstract]
Birkeland, K., K. Kronholm, and S. Logan. 2004. A comparison
of the spatal structure of the penetration resistance of snow
layers in two different snow climates. Proceedings of the International
Symposium on Snow Monitoring and Avalanches, Manali, India,
in press. [Article]
Kronholm, K. 2004. Spatial variability of snow mechanical properties
with regard to avalanche formation. Ph.D. Dissertation, Department
of Geography, University of Zurich. 187 pp. [PDF
(6 MB)]
Kronholm, K. and K.W. Birkeland. 2004. Relating spatial variability
to snow stability using a cellular automaton model initialized
with field data. Proceedings of the 2004 International Snow
Science Workshop, Jackson Hole, Wyoming. [Article]
Landry, C., K. Birkeland, K. Hansen, J. Borkowski, R. Brown,
and R. Aspinall. 2002. Snow stability on uniform slopes: Implications
for extrapolation. Proceedings of the 2002 International Snow
Science Workshop, Penticton, BC, Canada, 532-539. [Article]
Landry, C.C. 2002. Spatial variations in snow stability on uniform
slopes: Implications for extrapolation to surrounding terrain.
M.S. Thesis, Department of Earth Sciences, Montana State Universtity.
248 pp. [PDF (900K)]
Landry, C., K. Birkeland, K. Hansen, J. Borkowski, R. Brown,
and R. Aspinall. 2004. Variations in snow strength and stability
on uniform slopes. Cold Reg. Sci. Tech. 39, 205-218. [Abstract]
[Article]
Logan, S., K. Birkeland, K. Kronholm, and K. Hansen. 2004. Temporal
changes in the spatial variability of shear strength and stability.
Proceedings of the 2004 International Snow Science Workshop,
Jackson Hole, Wyoming. [Article]
Logan, S. 2005. Temporal changes in the spatial patterns of weak
layer shear strength and stability on uniform slopes. M.S. Thesis,
Department of Earth Sciences, Montana State University. 157 pp.
[PDF (5.5 MB)]
Lutz, E.R., K.W. Birkeland, K. Kronholm, K. Hansen, and R. Aspinall.
2004. Correlating snow micro-structure with snow shear strength.
Proceedings of the 2004 International Snow Science Workshop,
Jackson Hole, Wyoming. [Extended
abstract]