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Widespread thawing of permafrost in the northern Eurasian continent causes severe problems for infrastructure and global climate. We test the potential of Sentinel-1 SAR imagery to enhance detection of permafrost surface changes in the Siberian lowlands of the northern Eurasian continent at the Yamal peninsula site. We used InSAR time-series technique to detect seasonal surface movements related to permafrost active layer changes. The satellite InSAR time-series analysis has detected continuous movements, subsidence in three zones, which have occurred during the time period from 2017 to 2018. Observed subsidence zones show up to 180 mm yr−1 rates of seasonal active layers changes. These seasonal ground displacement patterns align well with lithology and linked to anthropogenic impact on the permafrost surface changes in the area. The results show that Sentinel-1 mission is of great importance for the longer-term monitoring of active layer thickening in permafrost regions. The combined analyses of the obtained InSAR time series with additional field observations may support regular process monitoring as part of a global warming risk assessment.

In this study fusion of optical (Sentinel-2) and radar (Sentinel-1) imagery is presented for vegetation cover classification in polar Arctic environment of the Western Siberia. Sentinel-1 and Sentinel-2 images were analyzed using parametric rule classification. Results showed significantly improved land cover classification results based on contextual analysis. Synergy of Sentinel-2 bands 4 and 3 and Sentinel-1 dual polarization VV and VH images increased the classification accuracy significantly. Specifically, classification accuracy increased for two classes — Erect dwarf-shrub tundra with 6% and Fresh Water with 10%. The classification accuracy as well test sites were analyzed using in situ data collected during three fieldwork campaigns in August-September (2016–2018) in the surrounding of Bovanenkovo settlement.

We investigated deep-seated gravitational slope deformation (DSGSD) and slow mass movements in the southern Tien Shan Mountains front using synthetic aperture radar (SAR) time-series data obtained by the ALOS/PALSAR satellite. DSGSD evolves with a variety of geomorphological changes (e.g. valley erosion, incision of slope drainage networks) over time that affect earth surfaces and, therefore, often remain unexplored. We analysed 118 interferograms generated from 20 SAR images that covered about 900 km2. To understand the spatial pattern of the slope movements and to identify triggering parameters, we correlated surface dynamics with the tectono-geomorphic processes and lithologic conditions of the active front of the Alai Range. We observed spatially continuous, constant hillslope movements with a downslope speed of approximately 71 mm year−1 velocity. Our findings suggest that the lithological and structural framework defined by protracted deformation was the main controlling factor for sustained relief and, consequently, downslope mass movements. The analysed structures revealed integration of a geological/structural setting with the superposition of Cretaceous–Paleogene alternating carbonatic and clastic sedimentary structures as the substratum for younger, less consolidated sediments. This type of structural setting causes the development of large-scale, gravity-driven DSGSD and slow mass movement. Surface deformations with clear scarps and multiple crest lines triggered planes for large-scale deep mass creeps, and these were related directly to active faults and folds in the geologic structures. Our study offers a new combination of InSAR techniques and structural field observations, along with morphometric and seismologic correlations, to identify and quantify slope instability phenomena along a tectonically active mountain front. These results contribute to an improved natural risk assessment in these structures.

Permafrost-affected river plains are highly diverse in discharge regime, floodplain morphology, channel forms, channel mobility and ecosystems. Frozen floodplains range from almost barren systems with high channel mobility, to extensive wetland areas with low channel mobility, abundant abandoned channels, back-swamps and shallow floodplain lakes. Floodplain processes are increasingly affected by climate-induced changes in river discharge and temperature regime: changes in the dates of freeze-up, break-up and spring floods, and changes in the discharge distribution throughout the year.In permafrost floodplains, changes in flooding frequency, flood height and water temperature affect active layer thickness, subsidence and erosion processes. Data from the Northeast Siberian Berelegh river floodplain (a tributary to the Indigirka river) demonstrate that increasing spring flood height potentially causes permafrost thaw, soil subsidence and increase of the floodplain area. INSAR (interferometric synthetic aperture radar) data indicate that poorly drained areas in this region are affected by soil subsidence. Morphological evidence for subsidence of the river floodplain is abundant, and river-connected lakes show expansion features also seen in thaw lakes.These floodplain wetland ecosystems are also affected by changes in the discharge regime and permafrost. On the one hand, floodplains are sites of active sedimentation of organic matter-rich sediments and sequestration of carbon. This carbon is derived from upstream erosion of permafrost and vegetation, and from autochthonous primary production. Nutrient supply by flood waters supports highly productive ecosystems with a comparatively large biomass.On the other hand, these ecosystems also emit high amounts of CH4, which may be affected by flooding regime. In the example presented here, the CH4 emission from floodplain wetlands is about seven times higher that the emission from similar tundra wetlands outside the floodplain.The dynamic nature of floodplains hinders carbon and greenhouse gas flux measurements. Better quantification of greenhouse gas fluxes from these floodplains, and their relation with river regime changes, is highly important to understand future emissions from thawing permafrost. Given the difficulties of surface greenhouse gas flux measurements, recent remote sensing material could play an important role here.

This thesis presents new approaches of SAR methods and their application to tectonically active systems and related surface deformation. With 3 publications two case studies are presented: (1) The coseismic deformation related to the Nura earthquake (5th October 2008, magnitude Mw 6.6) at the eastern termination of the intramontane Alai valley. Located between the southern Tien Shan and the northern Pamir the coseismic surface displacements are analysed using SAR (Synthetic Aperture RADAR) data. The results show clear gradients in the vertical and horizontal directions along a complex pattern of surface ruptures and active faults. To integrate and to interpret these observations in the context of the regional active tectonics a SAR data analysis is complemented with seismological data and geological field observations. The main moment release of the Nura earthquake appears to be on the Pamir Frontal thrust, while the main surface displacements and surface rupture occurred in the footwall and along of the NE–SW striking Irkeshtam fault. With InSAR data from ascending and descending satellite tracks along with pixel offset measurements the Nura earthquake source is modelled as a segmented rupture. One fault segment corresponds to high-angle brittle faulting at the Pamir Frontal thrust and two more fault segments show moderate-angle and low-friction thrusting at the Irkeshtam fault. The integrated analysis of the coseismic deformation argues for a rupture segmentation and strain partitioning associated to the earthquake. It possibly activated an orogenic wedge in the easternmost segment of the Pamir-Alai collision zone. Further, the style of the segmentation may be associated with the presence of Paleogene evaporites. (2) The second focus is put on slope instabilities and consequent landslides in the area of prominent topographic transition between the Fergana basin and high-relief Alai range. The Alai range constitutes an active orogenic wedge of the Pamir – Tien Shan collision zone that described as a progressively northward propagating fold-and-thrust belt. The interferometric analysis of ALOS/PALSAR radar data integrates a period of 4 years (2007-2010) based on the Small Baseline Subset (SBAS) time-series technique to assess surface deformation with millimeter surface change accuracy. 118 interferograms are analyzed to observe spatially-continuous movements with downslope velocities up to 71 mm/yr. The obtained rates indicate slow movement of the deep-seated landslides during the observation time. We correlated these movements with precipitation and seismic records. The results suggest that the deformation peaks correlate with rainfall in the 3 preceding months and with one earthquake event. In the next step, to understand the spatial pattern of landslide processes, the tectonic morphologic and lithologic settings are combined with the patterns of surface deformation. We demonstrate that the lithological and tectonic structural patterns are the main controlling factors for landslide occurrence and surface deformation magnitudes. Furthermore active contractional deformation in the front of the orogenic wedge is the main mechanism to sustain relief. Some of the slower but continuously moving slope instabilities are directly related to tectonically active faults and unconsolidated young Quaternary syn-orogenic sedimentary sequences. The InSAR observed slow moving landslides represent active deep-seated gravitational slope deformation phenomena which is first time observed in the Tien Shan mountains. Our approach offers a new combination of InSAR techniques and tectonic aspects to localize and understand enhanced slope instabilities in tectonically active mountain fronts in the Kyrgyz Tien Shan. Die vorliegende Arbeit stellt neue Ansätze zu Methoden des „Synthetic Aperture Radar“ (SAR) vor und wendet diese auf tektonisch aktive Systeme und die damit einhergehende Oberflächenverformung an. In drei wissenschaftlich begutachteten Publikationen in internationalen Fachzeitschriften werden im wesentlichen zwei Fallstudien präsentiert: (1) Die koseismische Verformung in Folge des Nura-Erdbebens (5. Oktober 2008, Mw 6.6) am östlichen Rand des intramontanen Alai-Beckens. Die koseismischen Verformungen an der Erdoberfläche wurden im Bereich zwischen dem südlichen Tien Shan und dem nördlichen Pamir mit Hilfe von SAR („Synthetic Aperture Radar“) Daten analysiert. Die Ergebnisse zeigen klare, sowohl horizontale als auch vertikale Gradienten, die entlang eines komplexen Musters von Brüchen an der Oberfläche und aktiven Störungen ausgebildet sind. Um diese Beobachtungen interpretieren und in den regionalen tektonischen Zusammenhang stellen zu können, wurde die SAR-Analyse durch seismologische und geologische Felduntersuchungen ergänzt. Die hauptsächliche Freisetzung der seismischen Energie des Nura-Erdbebens scheint an der frontalen Pamir-Überschiebung erfolgt zu sein, während die Hauptverformung und Oberflächenrupturen im Liegenden und entlang der NE-SW streichenden Irkeshtam-Störung auftraten. Unter Nutzung von InSAR-Daten von den aufsteigenden und absteigenden Satelliten-Bahnen sowie von Pixel-Versatz-Messungen wurde das Nura-Erdbeben als ein segmentierter Bruch modelliert. Dabei entspricht ein Segment einer steilen spröden Verwerfung an der frontalen Pamir-Überschiebung, während zwei andere Segmente mittel-steile und reibungsarme Verwerfungen an der Irkeshtam-Störung zeigen. Die integrierte Analyse der koseismischen Deformation spricht für eine Segmentierung des Bruches und eine Verteilung der Verformung in Folge des Erdbebens. Dies hat möglicherweise einen Gebirgskeil im äußersten östlichen Teil der Pamir-Alai-Kollisionszone aktiviert. Zudem könnte die Art der Segmentierung mit der Ablagerung von Paläogenen Evaporiten assoziiert sein. (2) Der zweite Schwerpunkt wurde auf tief-liegende langsame Böschungsverformungen gelegt, die insbesondere im Gebiet des markanten Übergangs zwischen dem Fergana-Tal und dem Hochrelief der Alai-Gebirgskette ausgeprägt sind. Die Alai-Kette stellt einen aktiven Gebirgskeil der Pamir-Tien-Shan-Kollisionszone dar, welche als ein sich stufenweise nach Norden fortsetzender Falten- und Überschiebungsgürtel beschrieben wird. Die interferometrische Analyse von ALOS/PALSAR-Radardaten deckt einen Zeitraum von vier Jahren ab (2007-2010) und nutzt den „Small-Basline-Subset“ (SBAS) Zeitreihenansatz um Oberflächendeformationen mit Millimeter-Genauigkeit zu bestimmen. 118 Interferogramme wurden analysiert, um die räumlich-kontinuierlichen Bewegungen mit Hangabwärts-Geschwindigkeiten von bis zu 71 mm/Jahr zu beobachten. Die erhaltenen Raten weisen auf eine langsame Bewegung von tief-verwurzelten Hangrutschungen während der Beobachtungszeit hin. Wir korrelierten diese Bewegungen mit Niederschlags- und seismischen Beobachtungen. Die Ergebnisse deuten darauf hin, dass die größten Deformationen mit den Regenmengen der drei vorhergehenden Monate und mit einem Erdbebenereignis korrelieren. Im nächsten Schritt wurden die tektonischen und lithologischen Verhältnisse mit den Mustern der Oberflächendeformation kombiniert, um das räumliche Muster der Hangrutschungsprozesse zu verstehen. Wir zeigen, dass die lithologischen und tektonischen Strukturen die Hauptkontrollmechanismen für das Auftreten von Hangrutschungen und für den Grad der Oberflächendeformation sind. Darüber hinaus ist die aktive Kontraktion und Einengungstektonik an der Vorderseite und Front des kontinentalen Akkretionskeils der hauptsächliche Mechanismus der Relieferhaltung. Einige der langsameren aber kontinuierlich in Bewegung befindlichen Instabilitäten stehen in direktem Zusammenhang mit der tektonisch aktiven Störungen und Hebung sowie mit unkonsolidierten, jung-quartären synorogenen Molassesedimenten. Unser Ansatz bietet eine neue Kombination von InSAR-Techniken und tektonischen Aspekten um Hanginstabilitäten in tektonisch aktiven Gebirgsfronten im Kirgisischen Tien Shan zu lokalisieren und zu verstehen.

In this study fusion of optical (Sentinel-2) and radar (Sentinel-1) imagery is presented for vegetation cover classification in polar Arctic environment of the Western Siberia. Sentinel-1 and Sentinel-2 images were analyzed using parametric rule classification. Results showed significantly improved land cover classification results based on contextual analysis. Synergy of Sentinel-2 bands 4 and 3 and Sentinel-1 dual polarization VV and VH images increased the classification accuracy significantly. Specifically, classification accuracy increased for two classes — Erect dwarf-shrub tundra with 6% and Fresh Water with 10%. The classification accuracy as well test sites were analyzed using in situ data collected during three fieldwork campaigns in August-September (2016–2018) in the surrounding of Bovanenkovo settlement.

Thaw of surficial permafrost ice bodies (ice wedges and ice-rich mounds) causes formation of ponds with enhanced emission of CH4 and CO2 . Usually these ponds develop in dry Betula nana shrub vegetation, which, when undisturbed, is a sink for both greenhouse gases. We mapped thaw pond development over time using satellite images of various ages and sources (Corona military intelligence images, recent high resolution images, Sentinel SAR) for the Kytalayk tundra research station in the Indigirka lowlands, Northeast Siberia. Areal expansion of thaw ponds is difficult to quantify because of water level fluctuations. However, ponds appear to expand in number, although ponds also disappear by vegetation succession. There is no evidence of better drainage due to permafrost thaw, as has been suggested for other permafrost areas. Greenhouse gas emission was quantified by chamber flux measurements. Besides high CH4 and CO2 emissions, occasionally also N2O emissions were also recorded. This indicates that these ponds are an increasing greenhouse gas source. However, vegetation succession studies have shown that their lifetime is short as they are colonized by CO2-sequestering vegetation within a few years. This life time has to be taken into account for quantifying the net greenhouse gas source as shown by our conceptual model.