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  • Potsdam : Universität Potsdam  (2)
  • [München] : Hanser
  • Baden-Baden : Nomos
  • New York, NY : Penguin Books
  • Hoboken, NJ : Wiley
  • Eberswalde : Waldkunde-Institut Eberswalde
  • Heidelberg : O'Reilly
  • Frankfurt am Main : Bund-Verlag
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  • 1
    Call number: AWI A7-24-95703
    Description / Table of Contents: The icosahedral non-hydrostatic large eddy model (ICON-LEM) was applied around the drift track of the Multidisciplinary Observatory Study of the Arctic (MOSAiC) in 2019 and 2020. The model was set up with horizontal grid-scales between 100m and 800m on areas with radii of 17.5km and 140 km. At its lateral boundaries, the model was driven by analysis data from the German Weather Service (DWD), downscaled by ICON in limited area mode (ICON-LAM) with horizontal grid-scale of 3 km. The aim of this thesis was the investigation of the atmospheric boundary layer near the surface in the central Arctic during polar winter with a high-resolution mesoscale model. The default settings in ICON-LEM prevent the model from representing the exchange processes in the Arctic boundary layer in accordance to the MOSAiC observations. The implemented sea-ice scheme in ICON does not include a snow layer on sea-ice, which causes a too slow response of the sea-ice surface temperature to atmospheric changes. To allow the sea-ice surface to respond faster to changes in the atmosphere, the implemented sea-ice parameterization in ICON was extended with an adapted heat capacity term. The adapted sea-ice parameterization resulted in better agreement with the MOSAiC observations. However, the sea-ice surface temperature in the model is generally lower than observed due to biases in the downwelling long-wave radiation and the lack of complex surface structures, like leads. The large eddy resolving turbulence closure yielded a better representation of the lower boundary layer under strongly stable stratification than the non-eddy-resolving turbulence closure. Furthermore, the integration of leads into the sea-ice surface reduced the overestimation of the sensible heat flux for different weather conditions. The results of this work help to better understand boundary layer processes in the central Arctic during the polar night. High-resolving mesoscale simulations are able to represent temporally and spatially small interactions and help to further develop parameterizations also for the application in regional and global models.
    Type of Medium: Dissertations
    Pages: xii, 110 Seiten , Illustrationen, Diagramme
    Language: English
    Note: Dissertation, Universität Potsdam, 2023 , Contents 1. Introduction 2. Boundary Layers Types of the Atmosphere 2.1. The Convective Boundary Layer (CBL) 2.2. The Neutral Boundary Layer (NBL) 2.3. The Stable Boundary Layer (SBL) 3. The Closure problem 4. Model description 4.1. Applied model versions 4.2. Governing equations 4.3. Horizontal grid 4.4. Vertical grid 4.5. Lateral boundaries 4.6. Parametrizations 4.6.1. Radiation scheme 4.6.2. Microphysics 4.6.3. Mellor-Yamada scheme 4.6.4. Smagorinsky scheme 4.6.5. Sea ice scheme 4.7. Difference to classical LES Models 5. Experimental Setup 6. MOSAiC Measurements 6.1. ARM Meteorological tower 6.2. Radiosondes 7. Model evaluation for the central Arctic 7.1. Impact of the horizontal resolution 7.1.1. Under cold, light wind conditions 7.1.2. Under stormy conditions 7.2. Impact of the sea-ice scheme 7.3. Impact of the lower boundary conditions 7.4. Impact of the parametrization schemes under cold, light wind conditions 7.4.1. Near-surface variables 7.4.2. Vertical profiles 7.4.3. Surface fluxes 7.4.4. Boundary Layer Height 7.5. Impact of the parametrization schemes under stormy conditions 7.5.1. Near-surface variables 7.5.2. Vertical profiles 7.5.3. Surface fluxes 7.5.4. Boundary Layer height 8. Discussion and Summary Acknowledgements Appendix
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  • 2
    Call number: AWI G3-24-95700
    Description / Table of Contents: With Arctic ground as a huge and temperature-sensitive carbon reservoir, maintaining low ground temperatures and frozen conditions to prevent further carbon emissions that contrib-ute to global climate warming is a key element in humankind’s fight to maintain habitable con-ditions on earth. Former studies showed that during the late Pleistocene, Arctic ground condi-tions were generally colder and more stable as the result of an ecosystem dominated by large herbivorous mammals and vast extents of graminoid vegetation – the mammoth steppe. Characterised by high plant productivity (grassland) and low ground insulation due to animal-caused compression and removal of snow, this ecosystem enabled deep permafrost aggrad-ation. Now, with tundra and shrub vegetation common in the terrestrial Arctic, these effects are not in place anymore. However, it appears to be possible to recreate this ecosystem local-ly by artificially increasing animal numbers, and hence keep Arctic ground cold to reduce or-ganic matter decomposition and carbon release into the atmosphere. By measuring thaw depth, total organic carbon and total nitrogen content, stable carbon iso-tope ratio, radiocarbon age, n-alkane and alcohol characteristics and assessing dominant vegetation types along grazing intensity transects in two contrasting Arctic areas, it was found that recreating conditions locally, similar to the mammoth steppe, seems to be possible. For permafrost-affected soil, it was shown that intensive grazing in direct comparison to non-grazed areas reduces active layer depth and leads to higher TOC contents in the active layer soil. For soil only frozen on top in winter, an increase of TOC with grazing intensity could not be found, most likely because of confounding factors such as vertical water and carbon movement, which is not possible with an impermeable layer in permafrost. In both areas, high animal activity led to a vegetation transformation towards species-poor graminoid-dominated landscapes with less shrubs. Lipid biomarker analysis revealed that, even though the available organic material is different between the study areas, in both permafrost-affected and sea-sonally frozen soils the organic material in sites affected by high animal activity was less de-composed than under less intensive grazing pressure. In conclusion, high animal activity af-fects decomposition processes in Arctic soils and the ground thermal regime, visible from reduced active layer depth in permafrost areas. Therefore, grazing management might be utilised to locally stabilise permafrost and reduce Arctic carbon emissions in the future, but is likely not scalable to the entire permafrost region.
    Type of Medium: Dissertations
    Pages: X, 104, A-57 Seiten , Illustrationen, Diagramme
    Language: English
    Note: Dissertation, Universität Potsdam, 2024 , Table of contents ABSTRACT ZUSAMMENFASSUNG ABBREVIATIONS AND NOMENCLATURE CHAPTER 1: INTRODUCTION 1.1 SCIENTIFIC BACKGROUND 1.1.1 ARCTIC GROUND 1.1.2 THE PHENOMENON OF PERMAFROST 1.1.3 ARCTIC NON - PERMAFROST AREAS 1.1.4 HYPOTHESIS 1.2 AIMS AND OBJECTIVES 1.3 METHODS 1.3.1 FIELD METHODS AND SAMPLING APPROACH 1.3.2 STUDY AREA SELECTION 1.3.3 LABORATORY METHODS 1.4 THESIS ORGANISATION CHAPTER 2: LARGE HERBIVORES ON PERMAFROST – A PILOT STUDY OF GRAZING IMPACTS ON PERMAFROST SOIL CARBON STORAGE IN NORTHEASTERN SIBERIA 2.1 ABSTRACT 2.2 I NTRODUCTION 2.3 STUDY AREA 2.4 METHODS 2.4.1 FIELD SAMPLING APPROACH 2.4.2 LABORATORY WORK 2.4.3 DATA ANALYSIS AND EXTERNAL DATA 2.5 RESULTS 2.5.1 VEGETATION ASSESSMENT 2.5.2 SEASONAL THAW DEPTH 2.5.3 CARBON PARAMETERS (TOC, TOC/TN RATIOS , AND Δ13 C RATIOS ) 2.5.4 GRAIN SIZE DISTRIBUTION AND WATER CONTENT 2.5.5 STATISTICS AND CORRELATION ANALYSIS 2.6 DISCUSSION 2.6.1 EFFECTS OF GRAZING ON VEGETATION STRUCTURE AND PERMAFROST THAW 2.6.2 CARBON ACCUMULATION UNDER GRAZING IMPACT 2.6.3 METHODOLOGICAL LIMITATIONS OF THE PILOT STUDY 2.7 CONCLUSION 2.8 DATA AVAILABILITY STATEMENT 2.9 AUTHOR CONTRIBUTIONS 2.10 FUNDING 2.11 ACKNOWLEDGEMENTS 2.12 CONFLICT OF INTERESTS CHAPTER 3: IMPACTS OF REINDEER ON SOIL CARBON STORAGE IN THE SEASONALLY FROZEN GROUND OF NORTHERN FINLAND: A PILOT STUDY 3.1 ABSTRACT 3.2 I NTRODUCTION 3.3 STUDY AREA 3.4 METHODS 3.4.1 FIELD WORK 3.4.2 LABORATORY ANALYSIS 3.4.3 DATA ANALYSIS AND CALCULATIONS 3.5 RESULTS 3.5.1 CORE DESCRIPTIONS 3.5.2 VEGETATION 3.5.3 CARBON PARAMETERS 3.5.6 COMPARATIVE DATA ANALYSIS 3.6 DISCUSSION 3.6.1 REINDEER IMPACT ON SOIL CARBON STORAGE 3.6.2 REINDEER IMPACT ON VEGETATION 3.6.3 REINDEER IMPACT ON GROUND CHARACTERISTICS 3.6.4 SOC DENSITY AND STOCKS ACROSS THE KUTUHARJU STATION AREA 3.6.5 METHODOLOGICAL LIMITATIONS OF THE PILOT STUDY DESIGN 3.6.6 IMPLICATIONS OF THE PILOT STUDY FOR FUTURE RESEARCH 3.7 CONCLUSION 3.8 DATA AVAILABILITY 3.9 AUTHOR CONTRIBUTION 3.10 COMPETING INTERESTS 3.11 ACKNOWLEDGEMENTS 3.12 FUNDING TABLE 3-1 TABLE 3-2 TABLE 3-3 CHAPTER 4: LIPID BIOMARKER SCREENING TO TRACE RECENT LARGE HERBIVORE INFLUENCE ON SOIL CARBON IN PERMAFROST AND SEASONALLY FROZEN ARCTIC GROUND 4.1 ABSTRACT 4.2 I NTRODUCTION 4.3 STUDY AREA 4.4 METHODS 4.4.1 SAMPLING APPROACH 4.4.2 LABORATORY ANALYSIS 4.4.3 LIPID BIOMARKER INDICES 4.4.4 STATISTICS 4.5 RESULTS 4.5.1 TOC 4.5.2 C/N RATIO 4.5.3 STABLE CARBON ISOTOPE RATIO 4.5.4 ABSOLUTE N- ALKANE CONCENTRATION 4.5.5 AVERAGE CHAIN LENGTH 4.5.6 CARBON PREFERENCE INDEX 4.5.7 HIGHER - PLANT ALCOHOL INDEX 4.5.8 STATISTICAL RESULTS 4.6 DISCUSSION 4.6.1 EFFECTS OF GRAZING INTENSITY ON BIOMARKER SIGNALS 4.6.2 EFFECTS OF GROUND THERMAL REGIME ON SOIL OM DEGRADATION 4.6.3 I MPACT OF HERBIVORY ON PERMAFROST OM STORAGE 4.7 CONCLUSION 4.8 ACKNOWLEDGEMENTS 4.9 COMPETING INTERESTS 4.10 AUTHOR CONTRIBUTION 4.11 FUNDING 4.12 DATA AVAILABILITY CHAPTER 5: SYNTHESIS 5.1 ECOSYSTEM CHANGES UNDER THE IMPACT OF LARGE HERBIVORES 5.2 GRAZING EFFECTS ON SOIL ORGANIC MATTER DECOMPOSITION 5.3 F EASIBILITY OF UTILISING HERBIVORY IN THE ARCTIC 5.4 RESEARCH IMPLICATIONS FOR SUCCESSFUL PLANNING AND USE OF ARCTIC HERBIVORY REFERENCES 93 FINANCIAL AND TECHNICAL SUPPORT APPENDIX 1 APPENDIX I ORGANIC CARBON CHARACTERISTICS IN ICE - RICH PERMAFROST IN ALAS AND YEDOMA DEPOSITS , CENTRAL YAKUTIA, SIBERIA APPENDIX II WHAT ARE THE EFFECTS OF HERBIVORE DIVERSITY ON TUNDRA ECOSYSTEMS ? A SYSTEMATIC REVIEW (ABSTRACT) APPENDIX III SUPPLEMENTARY MATERIAL TO CHAPTER 2: LARGE HERBIVORES ON PERMAFROST – A PILOT STUDY OF GRAZING IMPACTS ON PERMAFROST SOIL CARBON STORAGE IN NORTHEASTERN SIBERIA APPENDIX IV SUPPLEMENTARY MATERIAL TO CHAPTER 3: IMPACTS OF REINDEER ON SOIL CARBON STORAGE IN THE SEASONALLY FROZEN GROUND OF NORTHERN FINLAND : A PILOT STUDY APPENDIX V SUPPLEMENTARY MATERIAL TO CHAPTER 4: A PILOT STUDY OF LIPID BIOMARKERS TO TRACE RECENT LARGE HERBIVORE INFLUENCE ON SOIL CARBON IN PERMAFROST AND SEASONALLY ROZEN ARCTIC GROUND APPENDIX VI SUPPLEMENTARY MATERIAL TO APPENDIX IV: ORGANIC CARBON CHARACTERISTICS IN ICE - RICH PERMAFROST IN ALAS AND YEDOMA DEPOSITS , CENTRAL YAKUTIA, SIBERIA ACKNOWLEDGEMENTS - DANKSAGUNG
    Location: AWI Reading room
    Branch Library: AWI Library
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