Suretta Sud Glacier - Servizio Glaciologico Lombardo

mass balance
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processed with a specific, commercial
software;
production of a terrain digital model
through a mesh of irregular triangles
(TIN, Triangulated Irregular Network),
starting from the quoted points of the
previous step, using the 3D Analyst
module of ArcView;
calculation of a square-mesh elevation
model with a 5 m cell side (GRID) starting
from the TIN. The raster model is a
mandatory step if the different surfaces
have to be compared to identify the variations
among two successive periods.
The 2004 surface GRID is represented
in Fig. 4;
elaboration of the net mass balance of
the glaciological year 2003-2004, using
the Map Algebra functions implemented
in the Spatial Analyst module of
ArcView,
production of the map of positive or
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Fig. 6: Suretta Sud Glacier:
the position of the ablation
measurements stakes installed
in September 2003.
negative altitude variations (Fig. 5), as
a result of the comparisons between the
2003 and the 2004 GRIDS;
• calculation of the altitude variations
GRID (Fig. 6), by subtracting the corresponding
cells of both overlapped matrixes
(2003 GRID minus 2004 GRID).
For a better interpretation of the figures, it is
worth to remind that the altitude variations in
the considered period are the combined result
of two different phenomena, both acting
at the same time: the accumulation/ablation
processes and the mass transfer from the accumulation
area to the ablation one.
The comparison between the two surfaces
has allowed the calculation of the glacier’s net
mass balance during the 2003-2004 season
(September 14, 2003 –September 5, 2004).
The net mass balance was – 86.000 m3 water
equivalent (w.e.), i.e. a loss of 0,52 m w.e. for
the entire surface. This figure is then compared
with the readings of the ablation stakes