Geomorphic impact of spring avalanches in Northwest Spitsbergen (79° N)

Using persistent snow cover as a debris trap enables isolation of snow avalanching from the combination of processes involved in debris transfer. In glacial cirques of Spitsbergen, accretion rates recorded in sample squares generally ranged from 0.04 mm/yr to 8.13 mm/yr, with extreme values close to 40 mm. Field observations carried out between 1982 and 1986 suggest that differences in erosional effects of spring avalanches primarily depend on morphostructural factors. For instance, rates of denudation presented here imply that the geomorphic impact of snow avalanching is at least twenty times higher on dissected mica schist walls than on steep and smooth gneissic walls. Moreover, it is noticeable that the average accretion rate of 0.3 mm/yr is roughly the same for pellicular avalanches studied in this paper and for major slush avalanches observed in Central Spitsbergen. However, if numerical values are similar, morphogenic effects are very different. While annual snow avalanches only rearrange debris by scraping scree slopes, episodic slush avalanches form long‐lasting boulder tongues.