Landslide monitoring using multi-temporal terrestrial laser scanning(TLS) and electrical resistivity tomography (ERT) in the high Arctic,Ny-Ålesund

International audienceThe acceleration of climate-induced changes in high arctic environments is evident and lead to a wide range ofprocesses (e.g. glacier retreat, landslide activity). Recent studies (Bernard et al. 2014) provide evidence that, thestability of the talus covered slopes is reducing and thus landslides are occurring more frequently on the slopessurrounding the Austre Lovénbreen glacier.The Austre Lovénbreen glacier basin is a relatively small arctic glacier basin located at 79◦N, Ny-Ålesund(Svalbard) and geologically is part of the Kongsvegen Group, which is composed of the Nielsenfjellet, Steenfjelletand the Bogegga Formation. This study focusses on the quantitative and spatiotemporal identification of shallowtranslational soil slides (i.e. debris slides, Hungr et al. 2014) originating from the talus-covered slopes of theperiglacial valley system.The assessment of the soil slides on the slopes of the Austre Lovénbreen basin was performed i) by geo-logical field surveys (09/2017, 09/2018), ii) by terrestrial laser scanning (TLS) campaigns measuring more than300 single laser scans (08/2012, 08/2013, 08/2014, 08/2015, 08/2016, 09/2017, 09/2018), and iii) by electricalresistivity tomography (ERT) in order to perform subsurface investigations (09/2018).The results provide insights into the slide geometry, thickness, volume, as well as time of formation anddeformation behaviour. Data show that since 2012 several soil slides in the range between 500 m3 und 5000 m3have failed on the steeply inclined (35-42◦) talus slopes. In many cases the failure surface was formed at thecontact between the talus material and a subsurface ice layer, which is covered by the talus deposits. Interestingly,the ice layers extent up to 100 m above the present-day Austre Lovénbreen glacier surface in the basin. The icelayer was also detectable by previous ground penetrating radar (GPR) studies, and if exposed by slides, alsovisible by TLS measurements (reflectivity), webcam images and field surveys. The subsurface ice, acting as afailure surface, limits the slide thickness to values between 1 and 5 m.Concerning trigger mechanisms, rainfall data in combination with the webcam images suggests that theformation of the shallow soil slides is related to intense rainfall events and furthermore to the mass loss of thevalley glacier reducing the retaining effect at the foot.The results contribute to better understanding of recent changes in high arctic landscape systems and maygive further indications on future landslide activity in the high arctic