Long-term destabilization of retrogressive thaw slumps (Herschel Island, Yukon, Canada)

Retrogressive thaw slumps (RTS) are a common thermokarst landform along Arctic coastlines and provide a large amount of material containing organic carbon to the nearshore zone. The number of RTS has strongly increased since the last century. They are characterized by rapidly changing topographical and internal structures e.g., mud flow deposits, seawater-affected sediments or permafrost bodies and are strongly influenced by gullies. Furthermore, we hypothesize that due to thermal and mechanical disturbance, large RTS preferentially develop a polycyclic behavior. To reveal the inner structures of the RTS several electrical resistivity tomography (ERT) transects were carried out in 2011, 2012, and 2019 on the biggest RTS on Herschel Island (Qikiqtaruk, YT, Canada), a highly active and well-monitored study area. 2D ERT transects were conducted crossing the RTS longitudinal and transversal, always reaching the undisturbed tundra. Parallel to the shoreline, and crossing the main gully draining the slump, we applied 3D ERT which was first measured in 2012 and repeated in 2019. The ERT data was calibrated in the field using frost probing to detect the unfrozen-frozen transition and with bulk sediment resistivity versus temperature curves measured on samples in the laboratory. The strong thermal and topographical disturbances by gullies developing into large erosional features like RTS, lead to long recovery rates for disturbed permafrost, probably taking more than decades. In this study we demonstrate that ERT can be used to determine long-lasting thermal and mechanical disturbances. We show that they are both likely to prime the sensitivity of RTS to a polycyclic reactivation

Anisotropic Strain Induced Soliton Movement Changes Stacking Order and Bandstructure of Graphene Multilayers

The crystal structure of solid-state matter greatly affects its electronic properties. For example in multilayer graphene, precise knowledge of the lateral layer arrangement is crucial, since the most stable configurations, Bernal and rhombohedral stacking, exhibit very different electronic properties. Nevertheless, both stacking orders can coexist within one flake, separated by a strain soliton that can host topologically protected states. Clearly, accessing the transport properties of the two stackings and the soliton is of high interest. However, the stacking orders can transform into one another and therefore, the seemingly trivial question how reliable electrical contact can be made to either stacking order can a priori not be answered easily. Here, we show that manufacturing metal contacts to multilayer graphene can move solitons by several $\mu$m, unidirectionally enlarging Bernal domains due to arising mechanical strain. Furthermore, we also find that during dry transfer of multilayer graphene onto hexagonal Boron Nitride, such a transformation can happen. Using density functional theory modeling, we corroborate that anisotropic deformations of the multilayer graphene lattice decrease the rhombohedral stacking stability. Finally, we have devised systematics to avoid soliton movement, and how to reliably realize contacts to both stacking configurations

Life Cycles and Polycyclicity of Mega Retrogressive Thaw Slumps in Arctic Permafrost Revealed by 2D/3D Geophysics and Long‐Term Retreat Monitoring

Mega retrogressive thaw slumps (MRTS, >106 m3) are a major threat to Arctic infrastructure, alter regional biogeochemistry, and impact Arctic carbon budgets. However, processes initiating and reactivating MRTS are insufficiently understood. We hypothesize that MRTS preferentially develop a polycyclic behavior because the material is thermally and mechanically prepared for subsequent generation failure. In contrast to remote sensing, geophysical reconnaissance reveals the inner structure and relative thermal state of MRTS decameters beneath slump surfaces, potentially controlling polycyclicity. Based on their life cycle development, five (M)RTS were studied on Herschel Island, an MRTS hotspot on the Canadian Beaufort coast. We combine >2 km of electrical resistivity tomography (ERT), 500 m of ground-penetrating radar (GPR) and annual monitoring of headwall retreat from 2004 to 2013 to reveal the thermal state, internal structure, and volume loss of slumps. ERT data were calibrated with unfrozen-frozen transitions from frost probing of active layer thickness and shallow boreholes. In initial stage MRTS, ERT displays surficial thermal perturbations a few meters deep, coincident with recent mud pool and mud flow development. In early stage polycyclic MRTS, ERT shows decameter deep-reaching thermal perturbations persisting even 300 years after the last activation. In peak-stage polycyclic MRTS, 3D-ERT highlights actively extending deep-reaching thermal perturbations caused by gully incisions, mud slides and mud flows. GPR and headwall monitoring reveal structural disturbance by historical mud flows, ice-rich permafrost, and a decadal quantification of headwall retreat and slump floor erosion. We show that geophysical signatures identify long-lasting thermal and mechanical disturbances in MRTS predefining their susceptibility to polycyclic reactivation

Regional environmental change versus local signal preservation in Holocene thermokarst lake sediments: A case study from Herschel Island, Yukon (Canada)

Thermokarst lakes cover nearly one fourth of ice-rich permafrost lowlands in the Arctic. Sediments from an athalassic subsaline thermokarst lake on Herschel Island (69°36′N; 139°04′W, Canadian Arctic) were used to understand regional changes in climate and in sediment transport, hydrology, nutrient availability and permafrost disturbance. The sediment record spans the last ~ 11,700 years and the basal date is in good agreement with the Holocene onset of thermokarst initiation in the region. Electrical conductivity in pore water continuously decreases, thus indicating desalinization and continuous increase of lake size and water level. The inc/coh ratio of XRF scans provides a high-resolution organic-carbon proxy which correlates with TOC measurements. XRF-derived Mn/Fe ratios indicate aerobic versus anaerobic conditions which moderate the preservation potential of organic matter in lake sediments. The coexistence of marine, brackish and freshwater ostracods and foraminifera is explained by (1) oligohaline to mesohaline water chemistry of the past lake and (2) redeposition of Pleistocene specimens found within upthrusted marine sediments around the lake. Episodes of catchment disturbance are identified when calcareous fossils and allochthonous material were transported into the lake by thermokarst processes such as active-layer detachments, slumping and erosion of ice-rich shores. The pollen record does not show major variations and the pollen-based climate record does not match well with other summer air temperature reconstructions from this region. Local vegetation patterns in small catchments are strongly linked to morphology and sub-surface permafrost conditions rather than to climate. Multidisciplinary studies can identify the onset and life cycle of thermokarst lakes as they play a crucial role in Arctic freshwater ecosystems and in the global carbon cycle of the past, present and future

First pan-Arctic assessment of dissolved organic carbon in lakes of the permafrost region

Lakes in permafrost regions are dynamiclandscape components and play an important role for climatechange feedbacks. Lake processes such as mineralizationand flocculation of dissolved organic carbon (DOC), oneof the main carbon fractions in lakes, contribute to thegreenhouse effect and are part of the global carbon cycle.These processes are in the focus of climate research, butstudies so far are limited to specific study regions. Inour synthesis, we analyzed 2167 water samples from 1833lakes across the Arctic in permafrost regions of Alaska,Canada, Greenland, and Siberia to provide first pan-Arcticinsights for linkages between DOC concentrations andthe environment. Using published data and unpublisheddatasets from the author team, we report regional DOCdifferences linked to latitude, permafrost zones, ecoregions,geology, near-surface soil organic carbon contents, andground ice classification of each lake region. The lakeDOC concentrations in our dataset range from 0 to1130 mg L−1(10.8 mg L−1median DOC concentration).Regarding the permafrost regions of our synthesis, wefound median lake DOC concentrations of 12.4 mg L−1(Siberia), 12.3 mg L−1(Alaska), 10.3 mg L−1(Greenland),and 4.5 mg L−1(Canada). Our synthesis shows a significantrelationship between lake DOC concentration and lakeecoregion. We found higher lake DOC concentrationsat boreal permafrost sites compared to tundra sites. Wefound significantly higher DOC concentrations in lakesin regions with ice-rich syngenetic permafrost deposits(yedoma) compared to non-yedoma lakes and a weak butsignificant relationship between soil organic carbon contentand lake DOC concentration as well as between ground icecontent and lake DOC. Our pan-Arctic dataset shows that theDOC concentration of a lake depends on its environmentalproperties, especially on permafrost extent and ecoregion, aswell as vegetation, which is the most important driver of lakeDOC in this study. This new dataset will be fundamental toquantify a pan-Arctic lake DOC pool for estimations of theimpact of lake DOC on the global carbon cycle and climatechange

Small Lake - Large Impact? Sedimentary records from Northern Alaska reveal lake expansion history and carbon dynamics

Thermokarst lakes are characteristic and dynamic landscape features of ice-rich permafrost environments. Our study of sedimentary records and shoreline expansion of Peatball Lake on the Alaska Arctic Coastal Plain reveals 1,400 years of thermokarst activity. While Peatball Lake likely initiated from a remnant pond of a drained lake basin, the catchment is likewise characterized by mid to late Holocene aged drained basins and remnants of Pleistocene and early Holocene aged uplands. As the lake expanded through lateral permafrost degradation, the sediment source has changed as indicated by internal-lake variability in sediment deposition. Reversed radiocarbon ages show recycling of “old” carbon and degraded organic matter became redeposited in the lake basin resulting in nutrient-poor sublittoral deposits. Our sedimentary records reflect the complexity of depositional environments in thermokarst lakes due to spatio-temporal changes in lake and catchment morphology as well as the impact of thermokarst lake activity on carbon storage of periglacial landscapes

Impacts of shore expansion and catchment characteristics on lacustrine thermokarst records in permafrost lowlands, Alaska Arctic Coastal Plain

Arctic lowland landscapes have been modified by thermokarst lake processes throughout the Holocene. Thermokarst lakes form as a result of ice-rich permafrost degradation, and they may expand over time through thermal and mechanical shoreline erosion. We studied proximal and distal sedimentary records from a thermokarst lake located on the Arctic Coastal Plain of northern Alaska to reconstruct the impact of catchment dynamics and morphology on the lacustrine depositional environment and to quantify carbon accumulation in thermokarst lake sediments. Short cores were collected for analysis of pollen, sedimentological, and geochemical proxies. Radiocarbon and 210Pb/137Cs dating, as well as extrapolation of measured historic lake expansion rates, were applied to estimate a minimum lake age of ~1400 calendar years BP. The pollen record is in agreement with the young lake age as it does not include evidence of the “alder high” that occurred in the region ~4000 cal yr BP. The lake most likely initiated from a remnant pond in a drained thermokarst lake basin (DTLB) and deepened rapidly as evidenced by accumulation of laminated sediments. Increasing oxygenation of the water column as shown by higher Fe/Ti and Fe/S ratios in the sediment indicate shifts in ice regime with increasing water depth. More recently, the sediment source changed as the thermokarst lake expanded through lateral permafrost degradation, alternating from redeposited DTLB sediments, to increased amounts of sediment from eroding, older upland deposits, followed by a more balanced combination of both DTLB and upland sources. The characterizing shifts in sediment sources and depositional regimes in expanding thermokarst lakes were, therefore, archived in the thermokarst lake sedimentary record. This study also highlights the potential for Arctic lakes to recycle old carbon from thawing permafrost and thermokarst processes

UNDERCOVEREISAGENTEN - ERSTE EXPEDITION UND AKTUELLER STAND DES ARKTISCHEN PERMAFROSTPROJEKTS

Die Menschen in der Arktis sind seit mehreren Jahrzehnten mit Veränderungen ihres Lebensraums, wie dem Auftauen des Permafrosts durch den globalen Klimawandel, konfrontiert. Ziel dieses Projekts ist es, die Erste Expedition und aktueller Stand des arktischen Permafrostprojekts Auswirkungen des Permafrosttauens durch die Erfassung und Analyse von Bildmaterial von UAVs zusammen mit Schüler*innen (SuS) in Kanada und Deutschland zu untersuchen. Während einer Expedition im September 2022 in Nordkanada durch das AWI, DLR und HeiGIT wurden erste UAV-Daten gemeinsam mit SuS der Moose Kerr School in Aklavik aufgenommen. Neben den rund 30000 Einzelfotos über einer Fläche von ca. 13km² wurden die Grundlagen der Datenerhebung sowie die Projektziele der gemeinschaftlichen Permafrost-Untersuchung vermittelt. Vermittelte Ziele sind die selbstständig fortgeführte Datenaufnahme durch interessierte SuS, sowie die selbstständige Formulierung eigener wissenschaftl. Fragestellungen. Es erfolgte plangemäß die Einarbeitung von lokalem Wissen, um weitere Fragestellungen der lokalen Bevölkerung zu adressieren. Die Daten werden aktuell aufbereitet, um über eine Crowdmapping-Anwendung zur Verfügung gestellt zu werden

Nursing students' trait mindfulness and psychological stress: A correlation and mediation analysis

Background Nursing students face a great amount of psychological stress during their nursing education. Mindfulness-based training has received increased recognition from nurse educators regarding its effect on reducing students' psychological stress. Study evidence has supported that cultivation of trait mindfulness through Mindfulness-based training was the key to this effect. However, there is a lack of research that focuses on intricate relationships between various facets of trait mindfulness and psychological stress. Objective Examining the relationships between various trait mindfulness facets and psychological stress. Design A cross-sectional design was used to collect data on trait mindfulness facets and psychological stress. Participants A convenience sample of 99 undergraduate nursing students from a Bachelor of Nursing program completed this study. Setting This study was conducted in a university in the south-eastern United States. Method Participants completed an online questionnaire, which collected their demographic information, trait mindfulness (the Five Factor Mindfulness Questionnaire), and psychological stress (the Perceived Stress Scale-10). Correlation and mediation analyses were applied. Results Other than the trait mindfulness facet of observing, the remaining three facets (acting with awareness, non-judging, and non-reactivity) were negatively correlated with psychological stress. Observing had little to low correlations with non-judging and acting with awareness, but attained a moderately positive correlation with non-reactivity. Moreover, observing could indirectly predict psychological stress, when non-reactivity served as a mediator. Finally, non-judging partially mediated the relationship between acting with awareness and psychological stress. Conclusions The results of the current study can help nurse educators better understand the intricate relationships between various facets of trait mindfulness and psychological stress. Specifically, facets of acting with awareness, non-judging, and non-reactivity are directly relevant to the reduction of psychological stress. Therefore, regardless of formal or informal practices of mindfulness, nurse educators ought to assist students in cultivating these facets as means toward stress management

Auf dem Weg zur klimaneutralen Industrie - Herausforderungen und Strategien

Der Beitrag beleuchtet die Herausforderungen und Strategien für die Industrie in Deutschland im Rahmen der Energiewende. Der Fokus liegt hierbei auf den Themen Kreislaufwirtschaft, Wasserstoffnutzung, Erneuerbare Prozesswärme und Bioenergie sowie auf den sich darausergebenden Herausforderungen an die Infrastruktur und die Politik