Nordenskiold Land in Central Spitsbergen, Svalbard is characterized as a high latitude, high relief periglacial landscape with permafrost occurring both in mountains and lowlands. Freezing and thawing of the active layer causes seasonal frost heave and thaw subsidence, while permafrost-related mass-wasting processes induce downslope ground displacements on valley sides. Displacement rate varies spatially and temporally depending on environmental factors. In our study, we apply Satellite Synthetic Aperture Radar Interferometry (InSAR) to investigate the magnitude, spatial distribution and timing of seasonal ground displacements in and around Adventdalen using TerraSAR-X StripMap Mode (2009-2017) and Sentinel-1 Interferometric Wide Swath Mode (2015-2017) SAR images. First, we show that InSAR results from both sensors highlight consistent patterns and provide a comprehensive overview of the distribution of displacement rates. Secondly, two-dimensional (2D) TerraSAR-X InSAR results from combined ascending and descending geometries document the spatial variability of the vertical and east-west horizontal displacement rates for an average of nine thawing seasons. The remote sensing results are compared to a simplified geomorphological map enabling the identification of specific magnitudes and orientations of displacements for 14 selected geomorphological units. Finally, June to December 2017 6-day sampling interval Sentinel-1 time series was retrieved and compared to active layer ground temperatures from two boreholes. The timing of the subsidence and heave detected by InSAR matches the thawing and freeze-back periods measured by in-situ sensors. Our results highlight the value of InSAR to obtain landscape scale knowledge about the seasonal dynamics of complex periglacial environments.

Needle ice growth is one of the more widespread and easily visible, but less studied, climate related processes shaping soil evolution, surface dynamics and ecosystem changes in the alpine environments. Here, we show the results of the monitoring of needle ice development at four plots located at 2670 m a.s.l. close to the Stelvio Pass in the Italian Central Alps during 2016. Needle Ice formation and evolution with time was monitored through the photogrammetric technique of the Structure from Motion (SfM). Our monitoring data included also quantitative measurements of some selected physical and climatic parameters like air temperature, ground temperature and ground water content at depths of 2 and 5 cm. Our data demonstrate that needle ice can develop with a relatively low ground water content (13.2%), at a relatively high minimum ground temperature (-0.3 degrees C) and with a low cooling rate (< 1.8 degrees C h(-1)). Moreover, for the first time, we observed that needle ice can form below a thin snow cover (< 25 mm) that can enhance the sensible heat flow from the ground to the atmosphere and, therefore, promote the cooling of the near surface ground. Statistically, the minimum air temperature results in the leading factor for the needle ice growth. The total frost heave seems to be related to the abundance of fine material (although we couldn't demonstrate it statistically). The absence of statistically significant relationships between frost heave and frost creep could be probably due to the importance of the observed needle ice toppling and the possible sliding of the clasts during the melting phases.