Global Change Abstracts The Swiss Contribution - SCNAT

Global Change Abstracts – The Swiss Contribution | Cryosphere
day has been observed at South Pole, due to high
OH and NO levels present in a relatively shallow
boundary layer. Field and laboratory experiments
have determined that the origin of the observed
NOx flux is the photochemistry of nitrate within
the snowpack, however some details of the mechanism
have not yet been elucidated. A variety of
low molecular weight organic compounds have
been shown to be emitted from sunlit snowpacks,
the source of which has been proposed to be either
direct or indirect photo-oxidation of natural
organic materials present in the snow. Although
myriad studies have observed active processing
of species within irradiated snowpacks, the fundamental
chemistry occurring remains poorly
understood. Here we consider the nature of snow
at a fundamental, physical level; photochemical
processes within snow and the caveats needed for
comparison to atmospheric photochemistry; our
current understanding of nitrogen, oxidant, halogen
and organic photochemistry within snow; the
current limitations faced by the field and implications
for the future.
Atmospheric Chemistry and Physics, 2007, V7,
N16, pp 4329-4373.
08.1-225
Snow avalanche hazard modelling of large
areas using shallow water numerical methods
and GIS
Gruber U, Bartelt P
Switzerland
Cryology / Glaciology , Modelling , Instruments &
Instrumentation
Snow avalanches threaten settlements and roads
in steep mountainous areas. Hazard mitigation
strategies apply numerical models in combination
with GIS-based methods to determine run out distances
and pressure maps of snow avalanches in
three-dimensional terrain. The snow avalanche
modelling system is usually applied to study
single avalanche tracks. In this paper we investigate
the application of a numerical modelling
system for large area hazard analysis. We begin by
briefly presenting the depth-averaged equations
governing avalanche flow. Then, we describe the
statistical and GIS-based methods that are applied
to define the initial fracture depths and release
areas for snow avalanche modelling. We discuss
the calibration of the avalanche model friction
coefficients for extreme avalanches in function
of altitude, avalanche size and topography. Seven
test sites with areas between 100 and 350 km(2),
that are well distributed over the different snow
climates and elevation ranges of Switzerland,
were used to calibrate the model by comparing
123
the simulation results with historic avalanche
events and existing avalanche hazard maps. We
then show how the avalanche modelling system
was applied over the mountainous region of Switzerland
(25,000 km(2)) to delineate forests with
protective function against avalanches.
Environmental Modelling Software, 2007, V22,
N10, OCT, pp 1472-1481.
08.1-226
Retreat scenarios of Unteraargletscher, Switzerland,
using a combined ice-flow mass-balance
model
Huss M, Sugiyama S, Bauder A, Funk M
Switzerland, Japan
Modelling , Meteorology & Atmospheric Sciences ,
Cryology / Glaciology
The future evolution of Unteraargletscher, a large
valley glacier in the Swiss Alps, is assessed for the
period 2005 to 2050 using a flowline model. Detailed
measurements of surface velocity from the
last decade allow us to relate ice flux to glacier
thickness and width. Mass balance is calculated
using a distributed temperature- index model
calibrated with ice volume changes derived independently
from comparison of repeated digital
elevation models. The model was validated for the
period 1961 to 2005 and showed good agreement
between the simulated and observed evolution
of surface geometry. Regional climate scenarios
with seasonal resolution were used to investigate
the anticipated response of Unteraargletscher to
future climate changes. Three mass balance scenarios
were defined, corresponding to 2.5%, 50%,
and 97.5% quantiles of a statistical analysis of 16
different climate model results. We present a forecast
of the future extent of Unteraargletscher in
the next five decades and analyze relevant parameters
with respect to the past. The model predicts
a retreat of the glacier terminus of 800-1025 in by
2035, and of 1250-2300 in by 2050. The debris coverage
of the glacier tongue reduces the retreat rate
by a factor of three. The thinning, rate increased
by 50-183% by 2050 depending on the scenario applied,
compared to the period 1997 to 2005.
Arctic Antarctic and Alpine Research, 2007, V39,
N3, AUG, pp 422-431.