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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
    Location: AWI Reading room
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  • 2
    Publication Date: 2015-05-06
    Description: Although a subsurface phenomenon, permafrost creates distinct features on the land surface which can be observed using remote sensing data. This is especially true for the East Siberian Arctic where ice-rich permafrost is abundant in the geological subsurface and only protected by a thin layer of organic soils. In the Lena River Delta, deeper seasonal thaw during increasingly frequent warm summers does not only result in irreversible loss of ground ice and subsequent land subsidence, but also in discharge of soil organic carbon that was previously fixed in permafrost. To characterize the dynamics of thawing permafrost and its impacts on landscapes, hydrology, and emission of methane and carbon dioxide we analyse optical remote sensing time series from various sensors. Local field measurements (meteorology, ground temperature, geodetic surveys) during several recent Russian-German Arctic expeditions complement our remote sensing studies and help differentiating factors causing relief and land cover changes. While previous studies concentrated on general inventory of thermokarst landforms, higher temporal resolution of contemporary image acquisitions provides unique information for the understanding of seasonal processes, such as ice-on and ice-off on thermokarst lakes, shore erosion on delta channels, water level changes and drainage events in lakes, and wettening/drying of thermokarst-affected areas. Ground truth data provides the basis for calibration and correction of 21 RapidEye scenes (level 1B) from 2014 using a bundle block adjustment procedure. Next steps will include extraction of seasonal variations of band metrics such as NDVI which we will compare to decadal Landsat time series of landcover change and multitemporal, photogrammetrically-derived digital elevation models in order to identify signatures and trends typical for permafrost thaw related processes on the surface. Our approach will allow assessment of rates and short-term changes in thermokarst dynamics and landscape evolution. In addition, the derived data will be valuable for permafrost-thaw model parameterization.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed , info:eu-repo/semantics/conferenceObject
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  • 3
    Publication Date: 2015-05-28
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 4
    Publication Date: 2016-01-05
    Description: Vast portions of Arctic and sub-Arctic Siberia, Alaska and the Yukon Territory are covered by ice-rich silts that are penetrated by large ice wedges, resulting from syngenetic sedimentation and freezing. Accompanied by wedge-ice growth, 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 permafrost deposits up to 50 meter thick. Because of fast incorporation of organic material into permafrost during formation, Yedoma deposits include low-decomposed organic matter. Moreover, ice-rich permafrost 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 the climate warming, as increased permafrost thaw is likely to cause a positive feedback loop. Therefore, a detailed assessment of the Yedoma deposit volume is of importance to estimate its potential future climate response. Moreover, as a step beyond the objectives of this synthesis study, our coverage (see figure for the Yedoma domain) and thickness estimation will provide critical data to refine the Yedoma permafrost organic carbon inventory, which is assumed to have freeze-locked between 83±12 and 129±30 gigatonnes (Gt) of organic carbon. Hence, we here synthesize data on the circum-Arctic and sub-Arctic distribution and thickness of Yedoma permafrost (see figure for the Yedoma domain) in the framework of an Action Group funded by the International Permafrost Association (IPA). The quantification of the Yedoma coverage is conducted by the digitization of geomorphological and Quaternary geological maps. Further data on Yedoma thickness is contributed from boreholes and exposures reported in the scientific literature.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed , info:eu-repo/semantics/conferenceObject
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  • 5
    Publication Date: 2016-05-22
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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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.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 7
    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.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 8
    Publication Date: 2018-07-15
    Description: The distinguishing feature of permafrost in the Arctic is the presence of a large amount of ice below the earth surface. Thermal degradation and subsequent destabilization of ground ice rich terrain cause thaw subsidence. Because these phenomena are hard to detect, they have received not much attention, despite their potentially global significance through the permafrost carbon feedback and implications for active layer thickness monitoring. Clearly, however, detailed local inventories are required to calibrate regional targeted long and short-term assessments for measuring surface deformation due to permafrost thaw. We analyze time series of repeat terrestrial laser scanning (rLiDAR) for quantification of land surface lowering on a tundra upland in the Teshekpuk Lake Special Area on Alaska´s North Slope. Here, considerable negative surface elevation changes have been detected over two years from 2015 to 2017. Spatial patterns of land elevation changes indicate that ice wedge polygon troughs are particularly prone to subsidence. This highlights the vulnerability of arctic tundra lowlands with ice-rich permafrost close to the surface.
    Repository Name: EPIC Alfred Wegener Institut
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  • 9
    Publication Date: 2018-07-05
    Description: Recent studies on permafrost organic matter (OM) suggest that a portion of previously frozen carbon will enter the active carbon cycle as high latitudes warm. Less is known about the fate of other OM components, including nutrients such as nitrogen (N). The abundance and availability of N following permafrost thaw will regulate the ability of plants to offset carbon losses. Additionally, lateral N losses could alter aquatic food webs. There is growing evidence that some N is lost vertically as N2O, a greenhouse gas 300 times stronger than CO2 over 100 years. Despite broad recognition of its role regulating both carbon and non-carbon aspects of the permafrost climate feedback, estimates of permafrost N remain uncertain. To address this knowledge gap, we quantified N content for different stratigraphic units, including yedoma, Holocene cover deposits, refrozen thermokarst deposits, taberal sediments, and active layer soils. The resulting N estimates from this one permafrost region were similar in magnitude to previous estimates for the entire permafrost zone. We conclude that the permafrost N pool is much larger than currently appreciated and a substantial pool of permafrost N could be mobilized after thaw, with continental-scale consequences for biogeochemical budgets and global-scale consequences.
    Repository Name: EPIC Alfred Wegener Institut
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  • 10
    Publication Date: 2018-10-23
    Description: As Arctic warming continues and permafrost thaws, more soil and sedimentary organic matter (OM) will be decomposed in northern high latitudes. Still, uncertainties remain in the quality of the OM and the size of the organic carbon (OC) pools stored in different deposit types of permafrost landscapes. This study presents OM 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 belowground OC pool size and OM quality of ice-rich permafrost on the Baldwin Peninsula. We provide the first detailed characterization of yedoma deposits on Baldwin Peninsula. We show that three-quarters of soil OC in the frozen deposits of the study region (total of 68Mt) is stored in DTLB deposits (52Mt) and one-quarter in the frozen yedoma deposits (16Mt). The lake sediments contain a relatively small OC pool (4Mt), but have the highest volumetric OC content (93kgm−3) compared to the DTLB (35kgm−3) and yedoma deposits (8kgm−3), largely due to differences in the ground ice content. The biomarker analysis indicates that the OM 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 a degradation trend with depth in the yedoma deposits indicates that OM stored in yedoma is less degraded than that stored in DTLB deposits. This suggests that OM in yedoma has a higher potential for decomposition upon thaw, despite the relatively small size of this pool. These findings show that the use of lipid biomarker analysis is valuable in the assessment of 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.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed , info:eu-repo/semantics/article
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