@article{PhilippDietzUllmannetal.2023, author = {Philipp, Marius and Dietz, Andreas and Ullmann, Tobias and Kuenzer, Claudia}, title = {A circum-Arctic monitoring framework for quantifying annual erosion rates of permafrost coasts}, series = {Remote Sensing}, volume = {15}, journal = {Remote Sensing}, number = {3}, issn = {2072-4292}, doi = {10.3390/rs15030818}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-304447}, year = {2023}, abstract = {This study demonstrates a circum-Arctic monitoring framework for quantifying annual change of permafrost-affected coasts at a spatial resolution of 10 m. Frequent cloud coverage and challenging lighting conditions, including polar night, limit the usability of optical data in Arctic regions. For this reason, Synthetic Aperture RADAR (SAR) data in the form of annual median and standard deviation (sd) Sentinel-1 (S1) backscatter images covering the months June-September for the years 2017-2021 were computed. Annual composites for the year 2020 were hereby utilized as input for the generation of a high-quality coastline product via a Deep Learning (DL) workflow, covering 161,600 km of the Arctic coastline. The previously computed annual S1 composites for the years 2017 and 2021 were employed as input data for the Change Vector Analysis (CVA)-based coastal change investigation. The generated DL coastline product served hereby as a reference. Maximum erosion rates of up to 67 m per year could be observed based on 400 m coastline segments. Overall highest average annual erosion can be reported for the United States (Alaska) with 0.75 m per year, followed by Russia with 0.62 m per year. Out of all seas covered in this study, the Beaufort Sea featured the overall strongest average annual coastal erosion of 1.12 m. Several quality layers are provided for both the DL coastline product and the CVA-based coastal change analysis to assess the applicability and accuracy of the output products. The predicted coastal change rates show good agreement with findings published in previous literature. The proposed methods and data may act as a valuable tool for future analysis of permafrost loss and carbon emissions in Arctic coastal environments.}, language = {en} } @article{PhilippDietzUllmannetal.2022, author = {Philipp, Marius and Dietz, Andreas and Ullmann, Tobias and Kuenzer, Claudia}, title = {Automated extraction of annual erosion rates for Arctic permafrost coasts using Sentinel-1, Deep Learning, and Change Vector Analysis}, series = {Remote Sensing}, volume = {14}, journal = {Remote Sensing}, number = {15}, issn = {2072-4292}, doi = {10.3390/rs14153656}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-281956}, year = {2022}, abstract = {Arctic permafrost coasts become increasingly vulnerable due to environmental drivers such as the reduced sea-ice extent and duration as well as the thawing of permafrost itself. A continuous quantification of the erosion process on large to circum-Arctic scales is required to fully assess the extent and understand the consequences of eroding permafrost coastlines. This study presents a novel approach to quantify annual Arctic coastal erosion and build-up rates based on Sentinel-1 (S1) Synthetic Aperture RADAR (SAR) backscatter data, in combination with Deep Learning (DL) and Change Vector Analysis (CVA). The methodology includes the generation of a high-quality Arctic coastline product via DL, which acted as a reference for quantifying coastal erosion and build-up rates from annual median and standard deviation (sd) backscatter images via CVA. The analysis was applied on ten test sites distributed across the Arctic and covering about 1038 km of coastline. Results revealed maximum erosion rates of up to 160 m for some areas and an average erosion rate of 4.37 m across all test sites within a three-year temporal window from 2017 to 2020. The observed erosion rates within the framework of this study agree with findings published in the previous literature. The proposed methods and data can be applied on large scales and, prospectively, even for the entire Arctic. The generated products may be used for quantifying the loss of frozen ground, estimating the release of stored organic material, and can act as a basis for further related studies in Arctic coastal environments.}, language = {en} } @article{SchwindtKneisel2011, author = {Schwindt, Daniel and Kneisel, Christof}, title = {Optimisation of quasi-3D electrical resistivity imaging - application and inversion for investigating heterogeneous mountain permafrost}, series = {The Cryosphere Discuss}, volume = {5}, journal = {The Cryosphere Discuss}, doi = {10.5194/tcd-5-3383-2011}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-138017}, pages = {3383-3421}, year = {2011}, abstract = {This study aimed to optimise the application, efficiency and interpretability of quasi-3D resistivity imaging for investigating the heterogeneous permafrost distribution at mountain sites by a systematic forward modelling approach. A three dimensional geocryologic model, representative for most mountain permafrost settings, was developed. Based on this geocryologic model quasi-3D models were generated by collating synthetic orthogonal 2D arrays, demonstrating the effects of array types and electrode spacing on resolution and interpretability of the inversion results. The effects of minimising the number of 2D arrays per quasi-3D grid were tested by enlarging the spacing between adjacent lines and by reducing the number of perpendicular tie lines with regard to model resolution and loss of information value. Synthetic and measured quasi-3D models were investigated with regard to the lateral and vertical resolution, reliability of inverted resistivity values, the possibility of a quantitative interpretation of resistivities and the response of the inversion process on the validity of quasi-3D models. Results show that setups using orthogonal 2D arrays with electrode spacings of 2 m and 3 m are capable of delineating lateral heterogeneity with high accuracy and also deliver reliable data on active layer thickness. Detection of permafrost thickness, especially if the permafrost base is close to the penetration depth of the setups, and the reliability of absolute resistivity values emerged to be a weakness of the method. Quasi-3D imaging has proven to be a promising tool for investigating permafrost in mountain environments especially for delineating the often small-scale permafrost heterogeneity, and therefore provides an enhanced possibility for aligning permafrost distribution with site specific surface properties and morphological settings.}, language = {en} } @article{DobińskiKneisel2021, author = {Dobiński, Wojciech and Kneisel, Christof}, title = {Permafrost and glaciers: perspectives for the Earth and planetary sciences — another step forward}, series = {Geosciences}, volume = {11}, journal = {Geosciences}, number = {2}, issn = {2076-3263}, doi = {10.3390/geosciences11020068}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-228766}, year = {2021}, abstract = {No abstract available}, language = {en} } @phdthesis{Emmert2020, author = {Emmert, Adrian Alexander}, title = {The Internal Structure of Periglacial Landforms - Assessments of Subsurface Variations in Permafrost-related and Frost-related Phenomena by Multi-dimensional Geophysical Investigations}, edition = {1. Auflage}, publisher = {W{\"u}rzburg University Press}, address = {W{\"u}rzburg}, isbn = {978-3-95826-138-9}, doi = {10.25972/WUP-978-3-95826-139-6}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-202437}, school = {W{\"u}rzburg University Press}, pages = {xix, 167}, year = {2020}, abstract = {The internal structure of periglacial landforms contains valuable information on past and present environmental conditions. To benefit from this archive, however, an enhanced understanding of subsurface variations is crucial. This enables to assess the influence of the internal structure on prevailing process regimes and to evaluate the sensitivity of different landform units to environmental changes. This thesis investigates structural variations in the subsurface of (i) rock glaciers,(ii) solifluction lobes, (iii) palsas/ lithalsas and (iv) patterned ground, which occur between the different landform types, but also between landform units of the same type. Investigated variables comprise (i) the spatial distribution of permafrost, (ii) ground ice content, (iii) the origin of ground ice, (iv) thickness of the active layer and (v) frost table topography. Multi-dimensional investigations by the geophysical methods Electrical Resistivity Imaging (ERI) and Ground-Penetrating Radar (GPR) were performed in six study areas (a-f): four of them are located in high-alpine environments in Switzerland and two of them are located in the subarctic highlands of Iceland. Additionally, surface and subsurface temperature values were continuously recorded at selected study sites. At one study site, pF-values, representing the matric potential (or water potential), were recorded. From a methodological view, this thesis focuses on the application of quasi-3-D ERI, an approach in which many two-dimensional data sets are combined to create one three-dimensional data set. This permits e.g., a three-dimensional delimitation of subsurface structures and a spatial investigation of the distribution of ground ice. Besides the analysis of field data, this thesis incudes a comparison between inversion models produced with different software products, based on two synthetic data sets. The detection of resistivity structures and reflection patterns provides valuable insights into the internal structure of the investigated landform units: At the high-alpine study site at (a) Piz Nair, a highly variable ice content indicates a complex development of the investigated rock glacier assembly. The local formation of ground ice is attributed to an embedding of surface patches of snow or ice into the subsurface by rockfall. Results of geoelectric monitoring surveys on selected rock glaciers show the influence of seasonal alterations in the internal structure on subsurface meltwater flow. At the study site at (b) Piz {\"U}ertsch, results indicate the occurrences of isolated ground ice patches in a significantly larger rock glacier. Detected characteristics of the internal structure enable to reconstruct the development of the rock glacier, in which a temporary override of an adjacent glacier tongue on the rock glacier is considered crucial for the current distribution of ground ice. However, results of this thesis clearly show the absence of buried glacier ice in the subsurface of the rock glacier. Results from a rock glacier near the (c) Las Trais Fluors mountain ridge affirm the existence of a water-permeable frozen layer, which was assumed in previous studies. Furthermore, results show that the rock glacier contains large amounts of rockfall deposits. A joint interpretation of ERI and GPR results from the investigated scree slope at the mountain (d) Blauberg (Furka Pass) reveals characteristic structures in the subsurface, which enable a differentiation between solifluction lobes and pebbly rock glaciers. At the subarctic study site (e) Orravatnsr{\´u}stir, results show that the internal structure of palsas can be used to deduce their current development stage and to assess past and future developments. Presented results affirm a long history of palsa development at the study site, as assumed in previous studies, but indicate recently changing environmental conditions. The investigated occurrences of patterned ground in the proglacial area of the glacier (f) Hofsj{\"o}kull are currently not influenced by the detected occurrence of permafrost, according to the presented results. Therefore, a temporary formation of pattered ground is assumed, which is linked to the retreat of the glacier. This thesis shows discrepancies between the internal structure of some of the investigated landform units and the recent environmental conditions. This indicates a delayed adaption and a low sensitivity of the landform units to environmental changes. Findings indicate that the future development of permafrost will be strongly affected by variations in snowfall. Furthermore, the detection of isolated occurrences of ground ice at several study sites contradicts the widely assumed effectivity of balancing heat fluxes to create homogenous subsurface conditions in relatively fine-grained subsurface materials.}, subject = {Permafrost}, language = {en} } @article{KunzUllmannKneiseletal.2023, author = {Kunz, Julius and Ullmann, T. and Kneisel, C. and Baumhauer, R.}, title = {Three-dimensional subsurface architecture and its influence on the spatiotemporal development of a retrogressive thaw slump in the Richardson Mountains, Northwest Territories, Canada}, series = {Arctic, Antarctic, and Alpine Research}, volume = {55}, journal = {Arctic, Antarctic, and Alpine Research}, number = {1}, issn = {1523-0430}, doi = {10.1080/15230430.2023.2167358}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-350147}, year = {2023}, abstract = {The development of retrogressive thaw slumps (RTS) is known to be strongly influenced by relief-related parameters, permafrost characteristics, and climatic triggers. To deepen the understanding of RTS, this study examines the subsurface characteristics in the vicinity of an active thaw slump, located in the Richardson Mountains (Western Canadian Arctic). The investigations aim to identify relationships between the spatiotemporal slump development and the influence of subsurface structures. Information on these were gained by means of electrical resistivity tomography (ERT) and ground-penetrating radar (GPR). The spatiotemporal development of the slump was revealed by high-resolution satellite imagery and unmanned aerial vehicle-based digital elevation models (DEMs). The analysis indicated an acceleration of slump expansion, especially since 2018. The comparison of the DEMs enabled the detailed balancing of erosion and accumulation within the slump area between August 2018 and August 2019. In addition, manual frost probing and GPR revealed a strong relationship between the active layer thickness, surface morphology, and hydrology. Detected furrows in permafrost table topography seem to affect the active layer hydrology and cause a canalization of runoff toward the slump. The three-dimensional ERT data revealed a partly unfrozen layer underlying a heterogeneous permafrost body. This may influence the local hydrology and affect the development of the RTS. The results highlight the complex relationships between slump development, subsurface structure, and hydrology and indicate a distinct research need for other RTSs.}, language = {en} } @article{KunzKneisel2021, author = {Kunz, Julius and Kneisel, Christof}, title = {Three-dimensional investigation of an open- and a closed-system Pingo in northwestern Canada}, series = {Permafrost and Periglacial Processes}, volume = {32}, journal = {Permafrost and Periglacial Processes}, number = {4}, doi = {10.1002/ppp.2115}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257678}, pages = {541-557}, year = {2021}, abstract = {The present study presents three-dimensional investigations of a hydrostatic pingo in the Mackenzie Delta region and a hydraulic pingo in the Ogilvie Mountains and contributes to a better understanding about the internal structures of the two pingo types. A combined approach using quasi-three-dimensional electrical resistivity tomography, ground-penetrating radar and frost probing allowed a clear delineation of frozen and unfrozen areas in the subsurface. At the hydrostatic pingo a massive ice core as well as a surrounding talik could be detected, but the location of the ice core and the talik differs from previous published assumptions. In contrast to acknowledged theory, at our site the massive ice core is not located in the center of the pingo but at the western edge, whereas the eastern flank is underlain by a talik, which surrounds the massive ice core. At the hydraulic pingo, the expected internal structure could be confirmed and the pathway of upwelling water could also be detected. The combined approach of the applied methods represents the first known three-dimensional geoelectrical investigation of pingos and provides new insights into the internal structure and architecture of the two different pingo types. The chosen approach allows further conclusions on the formation of these permafrost-affected landforms.}, language = {en} } @article{PhilippDietzBucheltetal.2021, author = {Philipp, Marius and Dietz, Andreas and Buchelt, Sebastian and Kuenzer, Claudia}, title = {Trends in satellite earth observation for permafrost related analyses — A review}, series = {Remote Sensing}, volume = {13}, journal = {Remote Sensing}, number = {6}, doi = {10.3390/rs13061217}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-234198}, year = {2021}, abstract = {Climate change and associated Arctic amplification cause a degradation of permafrost which in turn has major implications for the environment. The potential turnover of frozen ground from a carbon sink to a carbon source, eroding coastlines, landslides, amplified surface deformation and endangerment of human infrastructure are some of the consequences connected with thawing permafrost. Satellite remote sensing is hereby a powerful tool to identify and monitor these features and processes on a spatially explicit, cheap, operational, long-term basis and up to circum-Arctic scale. By filtering after a selection of relevant keywords, a total of 325 articles from 30 international journals published during the last two decades were analyzed based on study location, spatio- temporal resolution of applied remote sensing data, platform, sensor combination and studied environmental focus for a comprehensive overview of past achievements, current efforts, together with future challenges and opportunities. The temporal development of publication frequency, utilized platforms/sensors and the addressed environmental topic is thereby highlighted. The total number of publications more than doubled since 2015. Distinct geographical study hot spots were revealed, while at the same time large portions of the continuous permafrost zone are still only sparsely covered by satellite remote sensing investigations. Moreover, studies related to Arctic greenhouse gas emissions in the context of permafrost degradation appear heavily underrepresented. New tools (e.g., Google Earth Engine (GEE)), methodologies (e.g., deep learning or data fusion etc.)and satellite data (e.g., the Methane Remote Sensing LiDAR Mission (Merlin) and the Sentinel-fleet)will thereby enable future studies to further investigate the distribution of permafrost, its thermal state and its implications on the environment such as thermokarst features and greenhouse gas emission rates on increasingly larger spatial and temporal scales.}, language = {en} }