Snowcover Survey over an Arctic Glacier Forefield: Contribution of Photogrammetry to Identify “Icing” Variability and Processes
Résumé
The global climate shift currently underway has significant impacts on
both the quality and quantity of snow precipitation. This directly
influences the spatial variability of the snowpack as well as cumulative
snow height. Contemporary glacier retreat reorganizes periglacial
morphology: while the glacier area decreases, the moraine area
increases. The latter is becoming a new water storage potential that is
almost as important as the glacier itself, but with considerably more
complex topography. Hence, this work fills one of the missing variables
of the hydrological budget equation of an arctic glacier basin by
providing an estimate of the snow water equivalent (SWE) of the moraine
contribution. Such a result is achieved by investigating Structure from
Motion (SfM) image processing that is applied to pictures collected from
an Unmanned Aerial Vehicle (UAV) as a method for producing snow depth
maps over the proglacial moraine area. Several UAV campaigns were
carried out on a small glacial basin in Spitsbergen (Arctic): the
measurements were made at the maximum snow accumulation season (late
April), while the reference topography maps were acquired at the end of
the hydrological year (late September) when the moraine is mostly free
of snow. The snow depth is determined from Digital Surface Model (DSM)
subtraction. Utilizing dedicated and natural ground control points for
relative positioning of the DSMs, the relative DSM georeferencing with
sub-meter accuracy removes the main source of uncertainty when assessing
snow depth. For areas where snow is deposited on bare rock surfaces,
the correlation between avalanche probe in-situ snow depth measurements
and DSM differences is excellent. Differences in ice covered areas
between the two measurement techniques are attributed to the different
quantities measured: while the former only measures snow accumulation,
the latter includes all of the ice accumulation during winter through
which the probe cannot penetrate, in addition to the snow cover. When
such inconsistencies are observed, icing thicknesses are the source of
the discrepancy that is observed between avalanche probe snow cover
depth measurements and differences of DSMs
Domaines
Autre
Origine : Publication financée par une institution
