Permafrost Thaw and Liberation of Inorganic Nitrogen in Eastern Siberia

The currently observed climate warming will lead to widespread degradation of near-surface permafrost, which may release substantial amounts of inorganic nitrogen (N) into arctic ecosystems. We studied 11 soil profiles at three different sites in arctic eastern Siberia to assess the amount of inorganic N stored in arctic permafrost soils. We modelled the potential thickening of the active layer for these sites using the CryoGrid2 permafrost model and representative concentration pathways (RCPs) 4.5 (a stabilisation scenario) and 8.5 (a business as usual emission scenario, with increasing carbon emissions). The modelled increases in active-layer thickness (ALT) were used to estimate potential annual liberation of inorganic N from permafrost soils during the course of climate change. We observed significant stores of inorganic ammonium in permafrost, up to 40-fold higher than in the active layer. The modelled increase in ALT under the RCP8.5 scenario can result in substantial liberation of N, reaching values up to the order of magnitude of annual fixation of atmospheric N in arctic soils. However, the thaw-induced liberation of N represents only a small flux in comparison with the overall ecosystem N cycling

Evaluation of PAEXO, a novel passive exoskeleton for overhead work

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Permafrost thaw and release of inorganic nitrogen from polygonal tundra soils in eastern Siberia

The currently observed climate warming will lead to substantial permafrost degradation and mobilization of formerly freeze-locked matter. Based on recent findings, we assume that there are substantial stocks of inorganic nitrogen (N) within the perennially frozen ground of arctic ecosystems. We studied eleven soil profiles down to one meter depth below surface at three different sites in arctic eastern Siberia, covering polygonal tundra and river floodplains, to assess the amount of inorganic N stores in arctic permafrost-affected soils. Furthermore, we modeled the potential thickening of the seasonally unfrozen uppermost soil (active) layer for these sites, using the CryoGrid2 permafrost model and representation concentration pathway (RCP) 4.5 and 8.5 scenarios. The first scenario, RCP4.5, is a stabilization pathway that reaches plateau atmospheric carbon concentrations early in the 21st century; the second, RCP8.5, is a business as usual emission scenario with increasing carbon emissions. The modeled increases in active layer thickness (ALT) were used to estimate potential annual N mobilization from permafrost-affected soils in the course of climate-induced active-layer deepening. We observed significant stores of inorganic ammonium in the perennially frozen ground of all investigated soils, up to 40-fold higher than in the active layer. The modeled ALT increase until 2100 under the RCP8.5 scenario was between 19 ± 3 cm and 35 ± 6 cm, depending on the location. Under the RCP4.5 scenario, the ALT remained stable in all investigated soils. Our estimated mean annual N release under the RCP8.5 scenario is between 8 ± 3 mg m−2 and 81 ± 14 mg m−2 for the different locations, which reaches values up to the order of magnitude of annual fixation of atmospheric N in arctic soils. However, the thawing induced release of N represents only a small flux in comparison with the overall ecosystem N cycling

Objective and Subjective Effects of a Passive Exoskeleton on Overhead Work

International audienceOverhead work is a frequent cause of shoulder work-related musculoskeletal disorders. Exoskeletons offering arm support have the potential to reduce shoulder strain, without requiring large scale reorganization of the workspace. Assessment of such systems however requires to take multiple factors into consideration. This paper presents a thorough in-lab assessment of PAEXO, a novel passive exoskeleton for arm support during overhead work. A list of evaluation criteria and associated performance metrics is proposed to cover both objective and subjective effects of the exoskeleton, on the user and on the task being performed. These metrics are measured during a lab study, where 12 participants perform an overhead pointing task with and without the exoskeleton, while their physical, physiological and psychological states are monitored. Results show that using PAEXO reduces shoulder physical strain as well as global physiological strain, without increasing low back strain nor degrading balance. These positive effects are achieved without degrading task performance. Importantly, participants' opinions of PAEXO are positive, in agreement with the objective measures. Thus, PAEXO seems a promising solution to help prevent shoulder injuries and diseases among overhead workers, without negatively impacting productivity

Irradiance and cloud optical properties from solar photovoltaic systems

Solar photovoltaic power output is modulated by atmospheric aerosols and clouds and thus contains valuable information on the optical properties of the atmosphere. As a ground-based data source with high spatiotemporal resolution it has great potential to complement other ground-based solar irradiance measurements as well as those of weather models and satellites, thus leading to an improved characterisation of global horizontal irradiance. In this work several algorithms are presented that can retrieve global tilted and horizontal irradiance and atmospheric optical properties from solar photovoltaic data and/or pyranometer measurements. Specifically, the aerosol (cloud) optical depth is inferred during clear sky (completely overcast) conditions. The method is tested on data from two measurement campaigns that took place in Allgäu, Germany in autumn 2018 and summer 2019, and the results are compared with local pyranometer measurements as well as satellite and weather model data. Using power data measured at 1 Hz and averaged to 1 minute resolution, the hourly global horizontal irradiance is extracted with a mean bias error compared to concurrent pyranometer measurements of 11.45 W m−2, averaged over the two campaigns, whereas for the retrieval using coarser 15 minute power data the mean bias error is 16.39 W m−2. During completely overcast periods the cloud optical depth is extracted from photovoltaic power using a lookup table method based on a one-dimensional radiative transfer simulation, and the results are compared to both satellite retrievals as well as data from the COSMO weather model. Potential applications of this approach for extracting cloud optical properties are discussed, as well as certain limitations, such as the representation of 3D radiative effects that occur under broken cloud conditions. In principle this method could provide an unprecedented amount of ground-based data on both irradiance and optical properties of the atmosphere, as long as the required photovoltaic power data are available and are properly pre-screened to remove unwanted artefacts in the signal. Possible solutions to this problem are discussed in the context of future work

Evaluation of PAEXO, a novel passive exoskeleton for overhead work

International audienc

Identifikation von Zukunftsforschungsfeldern für eine Forschungseinrichtung

Der Bedarf an Instrumenten zur Unterstützung bei der strategischen Ausrichtung von Forschungsaktivitäten steigt aufgrund der zunehmenden Dynamik der Technologieentwicklung und der zunehmenden Komplexität konvergierender Technologiefelder sowohl für Unternehmen als auch für Forschungseinrichtungen. Die Identifikation zukünftiger Forschungsfelder wird zum essenziellen Bestandteil der strategischen Ausrichtung. In Forschungseinrichtungen erfolgt dieser Prozess wenig standardisiert und es werden nur in geringem Umfang Vorausschauaktivitäten genutzt. Die erkenntnisgeleitete Entfaltung der Forschungsaktivitäten einzelner Forschungsgruppen ist von großer Relevanz. Dies bedeutet, dass die strategische Ausrichtung in Forschungseinrichtungen zu einem relevanten Anteil dezentral und nicht durch übergeordnete, zentrale Organisationseinheiten erfolgt. Die Forschungsaktivitäten sollten sich an der spezifischen Mission der jeweiligen Forschungseinrichtung ausrichten und Grundsätze der Wissenschaftsverantwortung berücksichtigen. Insbesondere für den Bereich der angewandten Forschung, der mit dem Unternehmensumfeld eng verbunden ist, stellt sich die Frage, ob sich Ansätze aus der Unternehmenspraxis auf Forschungseinrichtungen übertragen las-sen. Vor diesem Hintergrund wird eine Vorgehensweise skizziert, die ein Vorgehen zur Erstellung eines Technologie-Portfolios für Unternehmen aufgreift und an die spezifischen Rahmenbedingungen einer großen, dezentralen Forschungseinrichtung für angewandte Forschung anpasst. Der Bewertungsansatz umfasst eine Kombination aus qualitativen und quantitativen Analysen basierend auf Zukunfts-studien, Patent- und Publikationsdaten sowie Erkenntnissen zur internationalen Forschungsförderung. Die Attraktivität eines Forschungsfeldes wird in einem Portfolio dem spezifischen Niveau der Forschungsaktivitäten der Forschungseinrichtung gegenübergestellt. Die Methodik wurde für ausgewählte institutsüber-greifende Forschungsfelder bei Fraunhofer angewendet und getestet. Das Vorgehen wird anhand des Beispiels der additiven Fertigung skizziert und weitere Anwendungsbeispiele werden diskutiert. Abschließend wird erläutert, welche Schlussfolgerungen sich für die Identifikation von Zukunftsforschungsfeldern für Forschungseinrichtungen im Allgemeinen ergeben und wie eine Weiterentwicklung des Ansatzes erfolgen könnte

The Nitrogen Inventory of the Yedoma Permafrost Region

The biogeochemical composition of fossil organic matter stored in permafrost is an important subject in current climate change research. Multiple studies on the quality and quantity of permafrost organic carbon suggest that there is a high potential for carbon release into the active carbon turnover cycle through permafrost thaw in a warming Arctic. Other components of organic matter that are important for biogeochemical cycling, however, are less studied so far, including the amount and distribution of nitrogen (Keuper et al., 2012; Mack et al., 2004; Rustad et al., 2001). Nitrogen from thawing permafrost could be a significant source of the greenhouse gas N2O. Given its high global warming potential (about 300 times larger than CO2 over 100 years), even small releases of N2O can affect the permafrost-climate feedback. This study focuses on the abundance and distribution of nitrogen currently freeze-locked in the Yedoma region of Siberia and Alaska. Organic matter in permafrost deposits of the northern circumpolar region accumulated over tens of thousands of years during the last glacial and interglacial periods. A part of this permafrost region, the Yedoma region, is composed of thick ice-rich silts intersected by large ice wedges, resulting from sedimentation and syngenetic freezing accompanied by ice wedge growth in polygonal tundra, which was driven by certain climatic and environmental conditions during the late Pleistocene. These unique materials are called Yedoma deposits. They constitute a large organic carbon inventory of the (sub)Arctic but are also known to be nutrient-rich due to burial and freezing of plant remains. Besides carbon inventory estimates, detailed quantification of total nitrogen (TN) stocks is lacking. Based on the most comprehensive data set of TN content in permafrost to date, our study aims to estimate the present pool of nitrogen stored in the different stratigraphic units of the Yedoma region, which are (1) late Pleistocene Yedoma deposits; (2) in-situ thawed and diagenetically altered Yedoma deposits (taberite); (3) Holocene thermokarst deposits; (4) Holocene cover deposits on top of Yedoma and (5) the modern active layer of soils. Nitrogen stock calculations are based on statistical bootstrapping techniques using resampled observed values. The total mean pool size estimate is derived for every of the 10,000 bootstrapping runs, resulting in an overall mean derived from 10,000 individual observation-based bootstrapping means. The conceptual formula for our nitrogen stock calculation is given below. We show that the deposits of the Yedoma region store a significant pool of TN. At least a portion of this nitrogen is expected to get mobilized after thaw, affecting biogeochemical budgets and cycles of thawing permafrost-affected ecosystems. Possible effects include mitigation of the current nitrogen limitation of Arctic tundra ecosystems or a contribution of additional greenhouse gases in the form of N2O. In both cases, the permafrost-climate feedback will be affected by the amount and availability of so far not accessible nitrogen. Acknowledgements: This project is integrated into the Action Group “The Yedoma Region: A Synthesis of Circum-Arctic Distribution and Thickness” (funded by the International Permafrost Association (IPA) to J. Strauss). We acknowledge the support by the European Research Council (Starting Grant #338335), the German and Russian Science Foundations (DFG and RFBR “Polygon” project, DFG-HE 3622-16-1, and RFBR-11-04-91332-NNIO-a), the German Federal Ministry of Education and Research (Grant 01DM12011, and “CarboPerm” (03G0836A)), the Initiative and Networking Fund of the Helmholtz Association (#ERC-0013) and the German Federal Environment Agency (UBA, project UFOPLAN FKZ 3712 41 106). References Keuper, F., van Bodegom, P.M., Dorrepaal, E., Weedon, J.T., van Hal, J., van Logtestijn, R.S.P. and Aerts, R., 2012. A frozen feast: thawing permafrost increases plant-available nitrogen in subarctic peatlands. Global Change Biology, 18(6): 1998-2007, doi:10.1111/j.1365-2486.2012.02663.x. Mack, M.C., Schuur, E.A.G., Bret-Harte, M.S., Shaver, G.R. and Chapin, F.S., 2004. Ecosystem carbon storage in arctic tundra reduced by long-term nutrient fertilization. Nature, 431(7007): 440-443, doi:10.1038/nature02887. Rustad, L.E., Campbell, J.L., Marion, G.M., Norby, R.J., Mitchell, M.J., Hartley, A.E., Cornelissen, J.H.C., Gurevitch, J. and Gcte, N., 2001. A Meta-Analysis of the Response of Soil Respiration, Net Nitrogen Mineralization, and Aboveground Plant Growth to Experimental Ecosystem Warming. Oecologia, 126(4): 543-562, doi:10.1007/s004420000544

Neural networks learning structure in temporal signals

Cortical networks are strongly recurrent, and neurons have intrinsic temporal dynamics. This sets them apart from deep feed-forward networks. Despite the tremendous progress in the application of feed-forward networks and their theoretical understanding, it remains unclear how the interplay of recurrence and non-linearities in recurrent cortical networks contributes to their function. The purpose of this work is to present a solvable recurrent network model that links to feed forward networks. By perturbative methods we transform the time-continuous,recurrent dynamics into an effective feed-forward structure of linear and non-linear temporal kernels. The resulting analytical expressions allow us to build optimal time-series classifiers from random reservoir networks. Firstly, this allows us to optimize not only the readout vectors, but also the input projection, demonstrating a strong potential performance gain. Secondly, the analysis exposes how the second order stimulus statistics is a crucial element that interacts with the non-linearity of the dynamics and boosts performance

Schlussbericht: Transitionsgestaltung für nachhaltige Innovationen – Initiativen in den kommunal geprägten Handlungsfeldern Energie, Wasser, Bauen & Wohnen (TransNIK)

The aim of the TransNIK project was to investigate drivers and obstacles to the development and dissemination of innovative sustainable approaches in three fields of activity: energy, water and building & living. Furthermore it was the goal to identify key points for a transition to new solutions. The data collection for the case studies, which took place in the course of 2016, is based primarily on a total of 67 semi-structured interviews and was supplemented by internet research and document analyzes. The analyzes shows that in all areas of activity, the niches are struggling with a limited match with current regulation and institutions. Furthermore, there are areas of tension between the ideas of the project teams and the other involved actors, e.g. of the population/potential users, but also of institutions such as banks. Advisers and comparable interpreters, who can support the project groups in professionalisation, play a special role here. Such mediators have so far been less active in the water sector than in the areas of heating and living. Apart from that, lack of expertise continuously poses a challenge to projects. Integration with other project driven on the municipal scale can lead to synergies and increased efficiency. However, often actors seem to be operat-ing on the edge of their capacities. Thus, these synergies are only realized seldomly. The existing infrastructure or the accessibility and the adaptability of the existing infra-structure have an important influence on the success of the projects in scope. This raises questions, in particular, to what extent windows of opportunity can and need to be used in order to to escape socio-technical intertia. Finally, a quantitative evaluation of the sustainability impacts hardly take place in the projects, even if it is an important motivation. The generated results shed light on the complexity of sustainability related governance on the municipal level, but also offers policy suggestions to accelerate local transitions