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  • 1
    Call number: AWI G6-19-92461
    Type of Medium: Dissertations
    Pages: XVI, 203 Seiten , Illustrationen, Diagramme
    Language: English
    Note: Dissertation, Universität Potsdam, 2019 , Table of contents Abstract Zusammenfassung Abbreviations 1 Introduction 1.1 Scientific background 1.1.1 Permafrost in the Northern Hemisphere 1.1.2 The permafrost carbon climate feedback 1.1.3 Rapidly changing, deep permafrost environments 1.2 Aims of this dissertation 1.3 Investigated study areas 1.4 Basic method overview 1.4.1 Field work in the Arctic 1.4.2 Laboratory procedure 1.4.3 Analysis ofl andscape-scale carbon and nitrogen stocks 1.5 Thesis organization 1.6 Overview of publications 1.6.1 Publication#1 - Yedoma landscape publication 1.6.2 Publication#2 - Thermokarst lake sequence publication 1.6.3 Publication#3 - North Alaska Arctic river delta publication 1.6.4 Extended Abstract - Western Alaska river delta study 1.6.5 Appendices - Supplementary material and paper in preparation II Carbon and nitrogen pools in thermokarst-affected permafrost landscapes in Arctic Siberia 2.1 Abstract 2.2 Introduction 2.3 Material and methods 2.3.1 Study area 2.3.2 Field Work 2.3.3 Laboratory analysis 2.3.4 Landform classification and upscaling C and N pools 2.4 Results 2.4.1 Sedimentological results 2.4.2 Sampling site SOC and N stocks 2.4.3 Upscaling: Landscape SOC and N stocks 2.4.4 Radiocarbon dates 2.5 Discussion 2.5.1 Site specific soil organic C and N stock characteristics 2.5.2 Upscaling of C and N pools 2.5.3 Sediment and organic C accumulation rates 2.5.4 Characterizing soil organic carbon 2.5.5 The fate of organic carbon in thermokarst-affected yedoma in Siberia 2.6 Conclusions III Impacts of successive thermokarst lake stages on soil organic matter, Arctic Alaska 3.1 Abstract 3.2 Plain language summary 3.3 Introduction 3.4 Study site 3.5 Methods 3.5.1 Core collection 3.5.2 Biogeochemical analyses 3.5.3 Study area OC and N calculation 3.6 Results 3.6.1 Biogeochemistry 3.6.2 Sediment organic carbon and nitrogen stocks 3.6.3 Radiocarbon dates and carbon accumulation rates 3.6.4 Landscape C and N budget 3.7 Discussion 3.7.1 Impact of thermokarst lake dynamics on organic matter storage 3.7.2 High organic C and N stocks on the ACP 3.7.3 Landscape chronology 3.7.4 Organic matter accumulation 3.7.5 Future development 3.8 Conclusions IV Sedimentary and geochemical characteristics of two small permafrost-dominated Arctic river deltas in northern Alaska 4.1 Abstract 4.2 Introduction 4.3 Study area 4.4 Material and Methods 4.4.1 Soil organic carbon and soil nitrogen storage 4.4.2 Radiocarbon dating and organic carbon accumulation rates 4.4.3 Grain size distribution 4.4.4 Scaling carbon and nitrogen contents to landscape level 4.5 Results 4.5.1 Carbon and nitrogen contents 4.5.2 Radiocarbon dates and accumulation rates 4.5.3 Grain size distribution 4.5.4 Arctic river delta carbon and nitrogen storage 4.6. Discussion 4.6.1 Significance of carbon and nitrogen stocks in Arctic river deltas 4.6.2 SOC and SN distribution with depth 4.6.3 Sedimentary characteristics 4.6.3.1 Accumulation rates 4.6.3.2 Sediment distribution 4.6.4 Impacts of future changes 4.6.5 Significance of remotely sensed upscaling results 4.7 Conclusions V Soil carbon and nitrogen stocks in Arctic river deltas - New data for three Western Alaskan deltas 5.1 Abstract 5.2 Introduction 5.3 Study sites 5.4 Methods 5.5 Results and discussion 5.5 Conclusions VI Discussion 6.1 Interregional comparison 6.2 Changing thermokarst landscapes and their global impact 6.3 A growing C and N data base 6.4 Outlook - potential follow-up projects VII Synthesis VIII References Appendix A Synthesis of SOC and N inventories Appendix B Supplementary material to Chapter II Appendix C Supplementary material to Chapter III Appendix D Supplementary material to Chapter IV Appendix E Supplementary material to Chapter V Appendix F Arctic river delta data set - Version 1.0 Acknowledgements - Danksagung
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  • 2
    Publication Date: 2019-01-26
    Type: Dataset
    Format: text/tab-separated-values, 940 data points
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  • 3
    Publication Date: 2016-07-02
    Description: Vast portions of Arctic and sub-Arctic Siberia, Alaska and the Yukon Territory are covered by ice-rich silty to sandy deposits that are containing large ice wedges, resulting from syngenetic sedimentation and freezing. Accompanied by wedge-ice growth in polygonal landscapes, the sedimentation process was driven by cold continental climatic and environmental conditions in unglaciated regions during the late Pleistocene, inducing the accumulation of the unique Yedoma deposits up to >50 meters thick. Because of fast incorporation of organic material into syngenetic permafrost during its formation, Yedoma deposits include well-preserved organic matter. Ice-rich deposits like Yedoma are especially prone to degradation triggered by climate changes or human activity. When Yedoma deposits degrade, large amounts of sequestered organic carbon as well as other nutrients are released and become part of active biogeochemical cycling. This could be of global significance for future climate warming as increased permafrost thaw is likely to lead to a positive feedback through enhanced greenhouse gas fluxes. Therefore, a detailed assessment of the current Yedoma deposit coverage and its volume is of importance to estimate its potential response to future climate changes. We synthesized the map of the coverage (see figure) and thickness estimation, which will provide critical data needed for further research. In particular, this preliminary Yedoma map is a great step forward to understand the spatial heterogeneity of Yedoma deposits and its regional coverage. There will be further applications in the context of reconstructing paleo-environmental dynamics and past ecosystems like the mammoth-steppe-tundra, or ground ice distribution including future thermokarst vulnerability. Moreover, the map will be a crucial improvement of the data basis needed to refine the present-day Yedoma permafrost organic carbon inventory, which is assumed to be between 83±12 (Strauss et al., 2013) and 129±30 (Walter Anthony et al., 2014) gigatonnes (Gt) of organic carbon in perennially-frozen archives. Hence, here we synthesize data on the circum-Arctic and sub-Arctic distribution and thickness of Yedoma for compiling a preliminary circum-polar Yedoma map (see figure). For compiling this map, we used (1) maps of the previous Yedoma coverage estimates, (2) included the digitized areas from Grosse et al. (2013) as well as extracted areas of potential Yedoma distribution from additional surface geological and Quaternary geological maps (1.: 1:500,000: Q-51-V,G; P-51-A,B; P-52-A,B; Q-52-V,G; P-52-V,G; Q-51-A,B; R-51-V,G; R-52-V,G; R-52-A,B; 2.: 1:1,000,000: P-50-51; P-52-53; P-58-59; Q-42-43; Q-44-45; Q-50-51; Q-52-53; Q-54-55; Q-56-57; Q-58-59; Q-60; R-(40)-42; R-43-(45); R-(45)-47; R-48-(50); R-51; R-53-(55); R-(55)-57; R-58-(60); S-44-46; S-47-49; S-50-52; S-53-55; 3.: 1:2,500,000: Quaternary map of the territory of Russian Federation, 4.: Alaska Permafrost Map). The digitalization was done using GIS techniques (ArcGIS) and vectorization of raster Images (Adobe Photoshop and Illustrator). Data on Yedoma thickness are obtained from boreholes and exposures reported in the scientific literature. The map and database are still preliminary and will have to undergo a technical and scientific vetting and review process. In their current form, we included a range of attributes for Yedoma area polygons based on lithological and stratigraphical information from the original source maps as well as a confidence level for our classification of an area as Yedoma (3 stages: confirmed, likely, or uncertain). In its current version, our database includes more than 365 boreholes and exposures and more than 2000 digitized Yedoma areas. We expect that the database will continue to grow. In this preliminary stage, we estimate the Northern Hemisphere Yedoma deposit area to cover approximately 625,000 km². We estimate that 53% of the total Yedoma area today is located in the tundra zone, 47% in the taiga zone. Separated from west to east, 29% of the Yedoma area is found in North America and 71 % in North Asia. The latter include 9% in West Siberia, 11% in Central Siberia, 44% in East Siberia and 7% in Far East Russia. Adding the recent maximum Yedoma region (including all Yedoma uplands, thermokarst lakes and basins, and river valleys) of 1.4 million km² (see figure and Strauss et al. (2013)) and postulating that Yedoma occupied up to 80% of the adjacent formerly exposed and now flooded Beringia shelves (1.9 million km², down to 125 m below modern sea level, between 105°E – 128°W and >68°N), we assume that the Last Glacial Maximum Yedoma region likely covered more than 3 million km² of Beringia. Acknowledgements: This project is part of the Action Group “The Yedoma Region: A Synthesis of Circum-Arctic Distribution and Thickness” (funded by the International Permafrost Association (IPA) to J. Strauss) and is embedded into the Permafrost Carbon Network (working group Yedoma Carbon Stocks). We acknowledge the support by the European Research Council (Starting Grant #338335), 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 Grosse, G., Robinson, J.E., Bryant, R., Taylor, M.D., Harper, W., DeMasi, A., Kyker-Snowman, E., Veremeeva, A., Schirrmeister, L. and Harden, J., 2013. Distribution of late Pleistocene ice-rich syngenetic permafrost of the Yedoma Suite in east and central Siberia, Russia. US Geological Survey Open File Report, 1078. U.S. Geological Survey Reston, Virginia, 37 pp. Strauss, J., Schirrmeister, L., Grosse, G., Wetterich, S., Ulrich, M., Herzschuh, U. and Hubberten, H.-W., 2013. The Deep Permafrost Carbon Pool of the Yedoma Region in Siberia and Alaska. Geophysical Research Letters, 40: 6165–6170, doi:10.1002/2013GL058088. Walter Anthony, K.M., Zimov, S.A., Grosse, G., Jones, M.C., Anthony, P.M., Chapin III, F.S., Finlay, J.C., Mack, M.C., Davydov, S., Frenzel, P. and Frolking, S., 2014. A shift of thermokarst lakes from carbon sources to sinks during the Holocene epoch. Nature, 511: 452–456, doi:10.1038/nature13560.
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  • 4
    Publication Date: 2016-07-19
    Description: Late Pleistocene ice-rich syngenetic permafrost deposits called Yedoma store large amounts of organic carbon and are highly affected by climate warming and permafrost degradation. Permafrost thaw, ice-wedge melt, and thermokarst processes affect and expose these carbon-rich deposits to increased microbial activity. Therefore, organic carbon which has been protected by permafrost for thousands of years may partially be released to the atmosphere as greenhouse gases CO2 and CH4. However the fate of this low decomposed carbon and the amount and distribution of carbon stored in Yedoma uplands and deposits of thermokarst landforms is still discussed. Our study aims to present a detailed comparison of near-surface organic carbon and nitrogen stocks up to 3m depth in Yedoma uplands as well as thermokarst basins along two permafrost coring transects. The transects are located on Sobo-Sise Island in the eastern part of the Lena river delta (NE Siberia) and cover different stages of Yedoma degradation including adjacent deltaic deposits. Sobo-Sise Island is characterized by Yedoma uplands (third Lena River Delta terrace) which are fragmented by thaw-induced erosion and thermokarst landforms. Inventarization of relief units revealed that about one quarter (86 km2) of Sobo-Sise is covered by Yedoma and an additional 28% (95 km2) is covered by partially eroded Yedoma slopes between Yedoma and surrounding drained thaw lake basins or river channels. 11% (38 km2) are covered by lakes or rivers and the remaining area (117 km2 or 35%) is covered by drained thaw lake basins (DTLB). Our approach is based on transect based soil sampling including sample locations on Yedoma uplands, slopes, and adjacent drained thaw lake basins of different generations as well as delta floodplains. Two transects were sampled which run from Yedoma uplands into thermokarst basins in equidistant intervals between the sampling points. In total 15 locations have been sampled with soil pits for the active layer portion and a SIPRE corer for the underlying permafrost. Total depths reached range from 45 cm to 318 cm. Prior to drilling with the corer, soil pits have been excavated down to the bottom of the active layer for a soil description and sampling of the active layer soils. As a result, for most sites the whole soil profile was sampled including active, transient and permafrost layer. Soil cores were subsampled and described in the field. Visual core description included sedimentology, plant macrofossils, and cryostratigraphy. Samples were transported frozen and analyzed in the laboratory for bulk density, total carbon (TC), total nitrogen (TN), total organic carbon (TOC), and grain size. 13 samples of plant macrofossils from both Yedoma uplands and drained thaw lake basin deposits were submitted for Accelerated Mass Spectrometry (AMS) radiocarbon dating to the Poznan Radiocarbon Laboratory, Poland. Mean soil organic carbon and nitrogen estimates were calculated based on the dry bulk density and % TOC and % TN respectively and added up to the reference depths of 30 cm and 100 cm. For an upscaling of the carbon content of the third terrace and whole Sobo-Sise Island, multispectral RapidEye satellite images at 5 m spatial resolution, Landsat satellite data at 30 m resolution and a GeoEye-1 based DEM with 2 m spatial resolution were included to establish a land cover classification. Results show a mean soil organic carbon storage for the third terrace on Sobo-Sise of 13.20 kg/m2 ± 1.69 for 0-30 cm and 25.35 kg/m2 ± 8.99 for 0-100 cm of which 31% is stored in permanently frozen soil. The soil organic carbon mean values for drained thaw lake basins are slightly slower with 7.63 kg/m2 ± 3.13 and 19.97 kg/m2 ± 7.28 for 0-30 and 0-100 cm respectively, of which 58% is stored in the permafrost layer in 0-100 cm depth. However, this is only the first meter of soil. Taking into account deeper layers, significantly more organic carbon is stored in the permafrost layer. Mean TOC for Yedoma upland samples (n=80) is 3.74 wt % ± 2.33; for DTLB samples (n=114) 2.97 wt % ± 2.56. The TOC values for DTLB are therefore slightly lower, which is due to a sample site in one drained thaw lake basin that had very low organic carbon contents. Excluding this extreme outlier, the mean TOC value for DTLB samples is still lower than for Yedoma samples. Mean nitrogen storage for Yedoma upland sites is 2.6 kg/m2 for 0-100 cm and for DTLB samples 1.5 kg/m2 for 0-100 cm. In comparison to the 1.2 kg/m2 ± 0.4 for the Holocene river terrace and 0.9 kg/m2 ± 0.4 for the active floodplains found by Zubrzycki et al. (2013), these values are higher and accordingly also represent a substantial nitrogen pool. Overall, this indicates that sites in drained thaw lake basins on Sobo-Sise are more depleted in organic carbon and nitrogen than sites on the Yedoma uplands. This study adds new data to and insights in the permafrost soil carbon storage estimate of the Lena river delta. Our study region on the third river terrace of Sobo-Sise Island has not been previously covered. A first total carbon pool estimation for Yedoma uplands and slopes representing the third terrace on Sobo-Sise Island (181 km2) results in about 2 Tg organic carbon stored in the first meter of soil when taking into account a wedge-ice content of 46.3 volume % (proposed by Ulrich et al., 2014) for Yedoma regions. In this first assessment, we only cover the first meter of soil and therefore our Yedoma upland data can be considered a mix of modern active layer soils and Holocene cover deposits, while our radiocarbon dates indicate no presence of Late Pleistocene Yedoma in the first meter of soil. For 0-200 cm TOC for the third terrace on Sobo-Sise can be estimated to about 4 Tg; however, this estimate is based on only three sample sites. Our results are a contribution to a growing soil carbon database (Hugelius et al., 2014) and add top soil data for Yedoma environments where modern soils and Holocene cover deposits overlie Yedoma deposits. More data will be processed in the future, in particular soil samples from three transects on the nearby Bykovksy Peninsula, to increase the significance of our findings and to investigate whether the rather low soil organic carbon storage in drained thaw lake basins of the western Lena Delta compared to Holocene cover deposits on Yedoma uplands on Sobo-Sise are exceptional or typical for the eastern Lena Delta region. References: Hugelius G, Strauss J, Zubrzycki S, Harden JW, Schuur EAG, Ping C-L, Schirrmeister L, Grosse G, Michaelson GJ, Koven CD, O`Donnell OA, Elberling B, Mishra U, Camill P, Yu Z, Palmtag J, Kuhry P. 2014. Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified gaps. Biogeosciences 11: 6573-6593. DOI:10.5194/bg-11-6573-2014 Ulrich M, Grosse G, Strauss J, Schirrmeister L. 2014.Quantifying wedge-ice volumes in Yedoma and thermokarst basin deposits. Permafrost and Periglacial Processes 25: 151–161. DOI:10.1002/ppp.1810 Zubrzycki S, Kutzbach L, Grosse G, Desyatkin A, Pfeiffer E-M. 2013. Organic carbon and total nitrogen stocks in soils of the Lena River Delta. Biogeosciences 10: 3507-3524. DOI:10.5194/bg-10-3507-2013
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  • 5
    Publication Date: 2016-09-22
    Description: Arctic river deltas are highly dynamic environments at the interface of land to ocean. Arctic deltas are underlain by permafrost deposits, which are highly vulnerable to a warming climate. The amount of soil carbon stored in these deltas and potentially vulnerable to mobilization due to permafrost thaw is poorly known and based on few data only. Previous soil carbon estimates (e.g. Hugelius et al., 2014, Tarnocai et al., 2009) were based on data from three large deltas, and no data is so far available for small (< 500 km2) Arctic river deltas. In this study, we investigate the soil carbon pools of two small Arctic river deltas entering the Beaufort Sea on the Alaska North Slope, the Ikpikpuk and the Fish Creek river deltas. Our approach couples soil carbon information with remotely sensed data to estimate the total carbon stock in the upper 1 m for these environments. Both river deltas are located within the continuous permafrost zone and are characterized by typical fluvial-deltaic features and processes, such as river channels and islands, floodplains and mudflats, sand dunes, as well as episodic flooding, erosion, and deposition. In addition, permafrost processes are an important factor for thaw, erosion, transport, and accumulation dynamics within these deltas. As a result, features specific to permafrost-dominated deltas are widespread such as thermokarst lakes, drained thaw lake basins and ice wedge polygonal tundra. Under future climate warming projections, Arctic river deltas will be threatened due to thawing permafrost (including melting and settling of ice-rich deposits) and a rising sea level in combination with coastal erosion. To better estimate how much soil carbon may be vulnerable to mobilization under these projected changes and might be released as greenhouse gases, it is necessary to study the total soil carbon storage in Arctic river deltas. This study presents the first carbon storage estimation in surface soils and sediments for two small Arctic deltas, which each cover each an area of about 100 km2. Nine different soil cores between 54 and 215 cm depth, including both, non-permanently and permanently frozen deposits, were collected in April 2014 and July 2015, and were analyzed in the laboratory for total organic carbon (TOC), total carbon (TC), total nitrogen (TN), stable isotopes (δ13C), grain size, and deposit age (14C). The soil C parameters were upscaled to each delta based on landcover classifications derived from Landsat and Spot images in combination with high-resolution digital terrain models (DTM) from airborne LIDAR and IfSAR datasets. The upscaling of the total carbon storage was based on different approaches including the correlation of near surface soil carbon storage with various remotely sensed landcover indices. These indices, such as the Tasseled Cap or NDVI for the year 2014 were derived from linear trend analyses of Landsat data taking into account the full Landsat 5-8 archive from 1985-2014. For comparison, a supervised classification (maximum likelihood) with Landsat 8 and Spot 5 images was established based on training areas derived from field information from two field trips, very high resolution aerial and satellite images, and high resolution surface elevation information. The carbon content was finally upscaled based on mean carbon values for the different land cover classes. The total organic carbon storage for the two deltas ranges between 1.5 and 2 teragrams (Tg) of carbon each for the first meter of soil (excluding all water areas), depending on the upscaling method and dataset used. The results compare favorably (comparing the mean carbon storage values per square meter) with what has been previously estimated for other, larger Arctic river deltas. This study shows that remote sensing is a suitable tool to upscale soil carbon values in remote Arctic river deltas where only few soil data is available. We are further working on extending our approach to other Arctic permafrost-influenced river deltas, such as the large Lena river delta, Siberia, where we and other colleagues have previously collected a substantial amount of soil carbon and landcover ground truth data. Hugelius G, Strauss J, Zubrzycki S, Harden JW, Schuur EAG, Ping C-L, Schirrmeister L, Grosse G, Michaelson GJ, Koven CD, O`Donnell OA, Elberling B, Mishra U, Camill P, Yu Z, Palmtag J, Kuhry P. 2014. Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified gaps. Biogeosciences 11: 6573-6593. DOI:10.5194/bg-11-6573-2014 Tarnocai C, Canadell JG, Schuur EAG, Kuhry P, Mazhitova G, Zimov S. 2009. Soil organic carbon pools in the northern circumpolar permafrost region. Global Biogeochemical Cycles 23: GB2023. DOI:10.1029/2008GB003327
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  • 6
    Publication Date: 2017-06-06
    Description: This study investigates the soil organic carbon SOC) storage in Tarfala Valley, northern Sweden. Field inventories, upscaled based on land cover, show that this alpine permafrost environment does not store large amounts of SOC, with an estimate mean of 0.9 ± 0.2 kg C/m2 for the upper meter of soil. This is 1 to 2 orders of magnitude lower than what has been reported for lowland permafrost terrain. The SOC storage varies for different land cover classes and ranges from 0.05 kg C/m2 for stone-dominated to 8.4 kg C/m2 for grass-dominated areas. No signs of organic matter burial through cryoturbation or slope processes were found, and radiocarbon-dated SOC is generally of recent origin (<2000 cal yr BP). An inventory of permafrost distribution in Tarfala Valley, based on the bottom temperature of snow measurements and a logistic regression model,showed that at an altitude where permafrost is probable the SOC storage is very low. In the high-altitude permafrost zones (above 1500 m), soils store only ca. 0.1 kg C/m2. Under future climate warming, an upward shift of vegetation zones may lead to a net ecosystem C uptake from increased biomass and soil development. As a consequence, alpine permafrost environments could act as a net carbon sink in the future,as there is no loss of older or deeper SOC from thawing permafrost.
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  • 7
    Publication Date: 2017-09-05
    Description: Ice rich Yedoma-dominated landscapes store considerable amounts of organic carbon (C) and nitrogen (N) and are vulnerable to degradation under climate warming. We investigate the C and N pools in two thermokarst-affected Yedoma landscapes – on Sobo-Sise Island and on Bykovsky Peninsula in the North of East Siberia. Soil cores up to three meters depth were collected along geomorphic gradients and analysed for organic C and N contents. A high vertical sampling density in the profiles allowed the calculation of C and N stocks for short soil column intervals and enhanced understanding of within-core parameter variability. Profile-level C and N stocks were scaled to the landscape level based on landform classifications from five-meter resolution, multispectral RapidEye satellite imagery. Mean landscape C and N storage in the first meter of soil for Sobo-Sise Island is estimated to be 20.2 kg C m−2 and 1.8 kg N m−2 and for Bykovsky Peninsula 25.9 kg C m−2 and 2.2 kg N m−2. Radiocarbon dating demonstrates the Holocene age of thermokarst basin deposits but also suggests the presence of thick Holocene aged cover layers which can reach up to two meters on top of intact Yedoma landforms. Reconstructed sedimentation rates of 0.10 mm yr−1–0.57 mm yr−1 suggest sustained mineral soil accumulation across all investigated landforms. Both Yedoma and thermokarst landforms are characterized by limited accumulation of organic soil layers (peat). We further estimate that an active layer deepening by about 100 cm will increase organic C availability in a seasonally thawed state in the two study areas by ~ 5.8 Tg (13.2 kg C m−2). Our study demonstrates the importance of increasing the number of C and N storage inventories in ice-rich Yedoma and thermokarst environments in order to account for high variability of permafrost and thermokarst environments in pan-permafrost soil C and N pool estimates.
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  • 8
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A microscopic statistical dynamical theory of the slow dynamics of entangled macromolecular fluids has been formulated at the level of effective generalized Langevin equations-of-motion of a tagged polymer. A novel macromolecular version of mode-coupling theory is employed to approximately capture the cooperative motions of entangled polymers induced by the long range, self-similiar interchain correlations. Polymer integral equation methods are used to determine the required equilibrium structural input. Entanglements arise due to time and space correlations of the excluded volume forces exerted by the surrounding matrix on a tagged macromolecule. A spatially resolved description of entanglement constraint amplitudes relates the fluctuating forces to fluid structure. Constraint relaxation proceeds via three parallel processes: probe center-of-mass translation and shape fluctuations, and collective matrix relaxation. Asymptotic scaling law predictions for the molecular weight and concentration dependences of transport coefficients and relaxation times of chain polymer solutions and melts are in qualitative agreement with the phenomenological reptation theory. Predictions for finite frequency properties such as anomalous diffusion, and shear stress and dielectric relaxation, are derived. Enhanced, power law dissipation for properties controlled by conformational relaxation is predicted, with the corresponding frequency scaling exponents in good agreement with experiments but differing from reptation behavior. For experimentally accessible chain lengths strong finite size corrections for the transport coefficients arise due to entanglement constraint porosity and constraint release. Successful quantitative applications to many experimental data sets suggest the theory provides a unified microscopic understanding of the non-asymptotic scaling laws observed for the viscosity, dielectric relaxation time, and solution self and tracer diffusion constants. Generalization to fractal macromolecular architectures allows semi-quantitative treatment of ring and spherical microgel melts, and tracer diffusion in gels. A theory for the influence of concentration fluctuations in entangled polymer blends and diblock copolymers has also been developed. Self-diffusion in blends is quantitatively suppressed due to dynamical constraints associated with domain formation. Much stronger suppression of diffusion and chain relaxation is predicted near and well below the order-disorder transition of diblock copolymer melts due to microdomain formation. New dynamical scaling laws are predicted, and quantitative agreement of the theory with recent measurements on polyolefin diblocks is demonstrated. Limitations of the theory, open problems, and possible future directions are discussed.
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  • 9
    Publication Date: 2018-05-17
    Description: As Arctic warming continues and permafrost thaws, more soil and sedimentary organic carbon (OC) will be decomposed in northern high latitudes. Still, uncertainties remain in the quantity and quality of OC stored in different deposit types of permafrost landscapes. This study presents OC data from deep permafrost and lake deposits on the Baldwin Peninsula which is located in the southern portion of the continuous permafrost zone in West-Alaska. Sediment samples from yedoma and drained thermokarst lake basin (DTLB) deposits as well as thermokarst lake sediments were analyzed for cryostratigraphical and biogeochemical parameters and their lipid biomarker composition to identify the size and quality of belowground OC pools in ice-rich permafrost on Baldwin Peninsula. We provide the first detailed characterization of yedoma deposits on Baldwin Peninsula. We show that three quarters of soil organic carbon in the frozen deposits of the study region (total of 68 Mt) is stored in DTLB deposits (52 Mt) and one quarter in the frozen yedoma deposits (16 Mt). The lake sediments contain a relatively small OC pool (4 Mt), but have the highest volumetric OC content(93 kg m-3) compared to the DTLB (35 kg m-3) and yedoma deposits (8 kg m-3), largely due to differences in the ground ice content. The biomarker analysis indicates that the OC in both yedoma and DTLB deposits is mainly of terrestrial origin. Nevertheless, the relatively high carbon preference index of plant leaf waxes in combination with a lack of degradation trend with depth in the yedoma deposits indicates that OC stored in yedoma is less degraded than that stored in DTLB deposits. This suggests that OC in yedoma has a higher potential for decomposition upon thaw, despite the relatively small size of this pool. These findings highlight the importance of molecular OC analysis for determining the potential future greenhouse gas emissions from thawing permafrost, especially because this area close to the discontinuous permafrost boundary is projected to thaw substantially within the 21st century.
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  • 10
    Publication Date: 2015-02-04
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed , info:eu-repo/semantics/conferenceObject
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