Multisensor Satellite Monitoring of the Snow Cover and its Relation to Plant Distribution and Growing Season on Svalbard

Changes in the timing of the last and first day with snow cover are among the most sensitive indicators of climate change. By the end of the century, northeastern parts of Svalbard could experience a 6-8°C increase in annual temperatures due to decreasing sea-ice coverage. Hence, it is of the utmost importance to monitor the present state and ongoing changes. The snow cover is an especially important ecological factor affecting soil moisture, plant survival, plant community composition and controlling the length of the growing season.

This paper describes the most recent snow cover maps developed for the entire Svalbard archipelago. A ten-year long climate record on snow has been developed using Terra MODIS and Envisat ASAR satellite data from 2000 and 2003, respectively. Daily time-series of snow cover are used to derive the spatial distribution of snow, assessing the first day of snow free conditions in early summer, first day of snow in autumn and the annual number of snow free days. Corresponding yearly and average maps for the ten-year period have been produced. The developed map products provide valuable information about the exact timing of snow and its relationship to the variability of growing season, biodiversity and vegetation cover. A daily multisensor/multitemporal cloud free fractional snow cover area product is automatically generated based on multitemporal interpolation in combination with multisensoral fusion of SAR and optical data. At local scales we also introduce high-resolution snow maps from SAR sensors like TerraSAR-X and Radarsat-2 to study detailed snow melting patterns at the 2-5 meter scale.

By comparing the derived snow maps to Landsat TM based vegetation maps and to Terra MODIS based growing season maps, an intimate correlation between snow cover, vegetation composition and distribution of species are recorded. At the local scale, the amounts of snow varies in the terrain with a tiny snow cover on ridges and heavy snow in depressions. At the regional scale, the most varied vegetation is located in the inner Isfjord area with early snowmelt and a regionally long growing season. On the opposite side, the Arctic Polar Desert Zone which is located in the eastern and northernmost areas, is characterized by an extremely short growing season. Due to an abbreviated growing season only a few vascular plants are adapted to these harsh growing conditions.