Jökull - 01.01.2019, Blaðsíða 104

Perennial snow patch detection based on remote sensing data on
Tröllaskagi Peninsula, northern Iceland
Hannah Tussetschläger1,∗, Skafti Brynjólfsson2, Sveinn Brynjólfsson3, Thomas Nagler4,
Rudolf Sailer1, Johann Stötter1 and Jan Wuite4
1Institute of Geography, University of Innsbruck, Austria; 2Icelandic Institute of Natural History, 600 Akureyri, Iceland
3Icelandic Meteorological Office, 600 Akureyri, Iceland 4ENVEO - Environmental Earth Observation, Austria
∗Correspondence: Hannah.Tussetschlaeger@uibk.ac.at
https://doi.org/10.33799/jokull2019.69.103
The understanding of permafrost distribution in Iceland is still limited and current knowledge is mainly based
on small scale observations and regional modelling using temperature data. In the Alps Perennial Snow Patches
have been considered to protect permafrost from solar radiation and are used as an indicator for the occurrence
of local permafrost. In this study perennial snow fields are detected and classified based on aerial and satellite
images. Effects of climatic and topographic factors on the snow field occurrence are investigated aiming to
provide insight into the distribution of local permafrost in northern Iceland. Multi-temporal optical satellite im-
ages (Landsat-5/-7/-8 and Sentinel-2, 1984–2017) have revealed a time-variable distribution of perennial snow
patches as possible permafrost indicators on the Tröllaskagi Peninsula in northern Iceland. Calculated normal-
ized difference snow index in combination with different threshold values at the end of summer season within
six selected study areas show that several snow patches are present in a time period of over 30 years. Perennial
snow patches in the study areas exhibit strong fluctuations in extent due to different local characteristics, e.g.
elevation, aspect or topography (plateau/open slopes vs. valleys/cirques). In three of the six study areas snow
patches have a high probability of occurrence and the pattern of the distribution is very similar in each time
period. Comparison with climate data from nearby weather stations indicates that perennial snow patches can
be used in combination with mean annual air temperatures as indicators for local permafrost distributions.
INTRODUCTION
While there are several studies on geomorphologi-
cal features indicating extensive periglacial activity in
Iceland in general (e.g. Thórarinsson, 1964; Friedman
et al., 1971; Schunke, 1974; Van Vliet-Lanoë et al.,
1998), the understanding of the regional distribution
of permafrost is still limited. According to Lilleøren
et al. (2013) knowledge of the local distribution of
permafrost as well as of its thermal state is impor-
tant for different issues, e.g. slope stability, natural
hazard assessment and infrastructure development. In
the mountain regions of Iceland, current knowledge
on permafrost distribution is based on a limited num-
ber of small-scale observations (e.g. Sæmundsson et
al., 2012, Kneisel et al., 2007; Sæmundsson et al.,
2018; Morino et al., 2019). Among the first inven-
tories of the permafrost distribution are those made
by Þórarinsson (1951), Stingl and Hermann (1976),
Priesnitz and Schunke (1978), Stötter (1991), Whal-
ley and Martin (1994), Þórhallsdóttir (1994; 1996;
1997) and Sæmundsson et al. (2012). Based on point-
measurements, Etzelmüller et al. (2007) and Farbrot
et al. (2007a) developed the first ideas on Icelandic-
wide patterns of permafrost distribution using the
mean annual air temperature (MAAT) as an indicator.
Etzelmüller et al. (2007) point out that permafrost ex-
ists at sites with limited snow cover below the MAAT
-3◦C isotherm, ranging from ca. 700 meter above sea
level (m a.s.l.) in the north to ca. 1000 m a.s.l. in the
JÖKULL No. 69, 2019 103