Transitional rock glaciers at sea level in northern Norway

• Published in: Earth Surface Dynamics
• Main Authors: Lilleøren, Karianne S., Etzelmüller, Bernd, Rouyet, Line, Eiken, Trond, Slinde, Gaute, Hilbich, Christin
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2022
• Subjects: article; Verlagsveröffentlichung; Nordkinn; Norway; Fennoscandia; glacier; Ice; Northern Norway; permafrost; Subarctic
• Online Access: https://doi.org/10.5194/esurf-10-975-2022; https://noa.gwlb.de/receive/cop_mods_00062908; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00062058/esurf-10-975-2022.pdf; https://esurf.copernicus.org/articles/10/975/2022/esurf-10-975-2022.pdf

Rock glaciers are geomorphological expressions of permafrost. Close to sea level in northernmost Norway, in the subarctic Nordkinn peninsula, we have observed several rock glaciers that appear to be active now or were active in the recent past. Active rock glaciers at this elevation have never before been described in Fennoscandia, and they are outside the climatic limits of present-day permafrost according to models. In this study, we have investigated whether or not these rock glaciers are active under the current climate situation. We made detailed geomorphological maps of three rock glacier areas in Nordkinn and investigated the regional ground dynamics using synthetic aperture radar interferometry (InSAR). One of the rock glaciers, namely the Ivarsfjorden rock glacier, was investigated in more detail by combining observations of vertical and horizontal changes from optical images acquired by airborne and terrestrial sensors and terrestrial laser scans (TLSs). The subsurface of the same rock glacier was investigated using a combination of electrical resistivity tomography (ERT) and refraction seismic tomography (RST). We also measured ground surface temperatures between 2016 and 2020, complemented by investigations using an infrared thermal camera, and a multi-decadal climatic analysis. We mapped the rock glaciers in the innermost parts of Store and Lille Skogfjorden as relict, while the more active ones are in the mouths of both fjords, fed by active talus in the upper slopes. Several of the rock glaciers cross over both the Younger Dryas shoreline (25 m a.s.l.) and the Early to Mid-Holocene shoreline at 13 m a.s.l. Both InSAR and optical remote sensing observations reveal low yearly movement rates (centimetres to millimetres per year). The ERT and RST suggest that there is no longer permafrost and ground ice in the rock glacier, while temperature observations on the front slope indicate freezing conditions also in summer. Based on the in situ temperature measurements and the interpolated regional ...