Spatio-temporal Variability of Snow Cover in Svalbard Derived From a Combination of Spaceborne Scatterometer, Glaciological Ground Truth and Meteorological Data

Evidence for ongoing large changes in the Arctic climate has been accumulating during the last decade, particularly with regards to sea ice, permafrost and glacier mass balance. Due to the effect of global warming dramatic changes in the Arctic snow and ice coverage are currently observed, expressed by a reduction of 10% over the last 30 years associated with an extended and longer lasting melting season. Previous studies have demonstrated the capacities of active microwave instruments for the detection of surface melt and freeze-up due to the high sensitivity of radar backscatter to snow wetness. Spaceborne scatterometers provide data at low spatial but high temporal resolution allowing consistent observations on a daily time scale. This study focuses on the Svalbard region characterized by a highly variable climate throughout the year due to its position within a zone that includes both the polar ocean and atmospheric fronts between the Arctic Ocean, Nordic Seas and Barents Sea. Nevertheless, over a long enough period of time we expect to see a general climatic trend by monitoring the spatio-temporal variability of snow distribution and melt all over Svalbard. For this we utilize microwave backscattering measurements continuously carried out by the Ku-band scatterometer QSCAT since fall 1999. Furthermore, we tested retrieval algorithms for the assessment of single snow fall events and the amount of snow accumulation during winter. A set of glaciological ground-truth data serves us for interpretation of the backscattering signatures, i.e. snow accumulation measurements by means of snow probing, snow pit sampling, drilling of shallow ice cores as well as ground penetrating radar measurements. In addition, meteorological data from weather stations around Svalbard are available to investigate links between atmospheric circulation, moisture transport, near surface air temperature and corresponding deposition and melting of snow, respectively. The analysis demonstrates that coarse resolution scatterometer data can be usefully applied to trace consequences of a warming climate in Svalbard.