ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    Call number: AWI A4-20-93991
    Description / Table of Contents: Over the last decades, the Arctic regions of the earth have warmed at a rate 2–3 times faster than the global average– a phenomenon called Arctic Amplification. A complex, non-linear interplay of physical processes and unique pecularities in the Arctic climate system is responsible for this, but the relative role of individual processes remains to be debated. This thesis focuses on the climate change and related processes on Svalbard, an archipelago in the North Atlantic sector of the Arctic, which is shown to be a "hotspot" for the amplified recent warming during winter. In this highly dynamical region, both oceanic and atmospheric large-scale transports of heat and moisture interfere with spatially inhomogenous surface conditions, and the corresponding energy exchange strongly shapes the atmospheric boundary layer. In the first part, Pan-Svalbard gradients in the surface air temperature (SAT) and sea ice extent (SIE) in the fjords are quantified and characterized. This analysis is based on observational data from meteorological stations, operational sea ice charts, and hydrographic observations from the adjacent ocean, which cover the 1980–2016 period. [...]
    Type of Medium: Dissertations
    Pages: xv, 123 Seiten , Illustrationen, Diagramme
    Language: English
    Note: Dissertation, Universität Potsdam, 2020 , CONTENTS 1 Introduction 1.1 Context: A rapidly changing Arctic 1.1.1 Documentation of recent changes in the Arctic 1.1.2 Research relevance 1.1.3 Objective: Svalbard as a hotspot for climate change 1.2 Physical Background 1.2.1 Radiation and surface energy balance 1.2.2 Peculiarities of the Arctic climate system 1.2.3 Role of atmospheric circulation 1.3 The regional setup on Svalbard 2 data and methods 2.1 Data description 2.1.1 Era-Interim atmospheric reanalysis 2.1.2 Svalbard Station Meteorology 2.1.3 Sea Ice Extent 2.1.4 Ocean data products 2.1.5 FLEXTRA Trajectories 2.2 Statistical Methods 2.2.1 Trend estimation 2.2.2 Correlation 2.2.3 Coefficient of Determination 3 state of surface climate parameters: pan-svalbard differences 3.1 Motivation 3.2 Surface air temperature 3.2.1 Annual cycle 3.2.2 Annual temperature range 3.2.3 Long-term trends 3.3 Fjord Sea Ice coverage 3.3.1 Climatology 3.3.2 Sea ice cover trends 3.3.3 Regional classification across Svalbard 3.3.4 Drivers of regional differences 3.4 Discussion and Conclusion 3.5 Current state of climate projections for the Svalbard region 4 Air mass back trajectories 4.1 Methodology 4.2 Winter 4.2.1 Source Regions of Ny-Ålesund Air 4.2.2 Circulation changes 4.2.3 Quantification of Advective Warming 4.3 Summer 4.3.1 Source Regions of Ny-Ålesund Air 4.3.2 Circulation changes 4.3.3 Quantification of advective cooling 4.3.4 Observational Case Study: May/June 2017 4.4 Discussion and Conclusion 5 Changing drivers of the arctic near surface temperature budget 5.1 Winter 5.2 Summer 5.3 Summary 6 Summary and conclusion A Details on calculations A.1 SLP composite Index A.2 Derivation of coefficient of determination A.3 Temperature effect of changing source regions over time B Supplementary figures Bibliography
    Location: AWI Reading room
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 12
    Call number: AWI Bio-20-93990
    Description / Table of Contents: Assumed comparable environmental conditions of early Mars and early Earth in 3.7 Ga ago – at a time when first fossil records of life on Earth could be found – suggest the possibility of life emerging on both planets in parallel. As conditions changed, the hypothetical life on Mars either became extinct or was able to adapt and might still exist in biological niches. The controversial discussed detection of methane on Mars led to the assumption, that it must have a recent origin – either abiotic through active volcanism or chemical processes, or through biogenic production. Spatial and seasonal variations in the detected methane concentrations and correlations between the presence of water vapor and geological features such as subsurface hydrogen, which are occurring together with locally increased detected concentrations of methane, gave fuel to the hypothesis of a possible biological source of the methane on Mars. Therefore the phylogenetically old methanogenic archaea, which have evolved under early Earth conditions, are often used as model-organisms in astrobiological studies to investigate the potential of life to exist in possible extraterrestrial habitats on our neighboring planet. In this thesis methanogenic archaea originating from two extreme environments on Earth were investigated to test their ability to be active under simulated Mars analog conditions. These extreme environments – the Siberian permafrost-affected soil and the chemoautotrophically based terrestrial ecosystem of Movile cave, Romania – are regarded as analogs for possible Martian (subsurface) habitats. Two novel species of methanogenic archaea isolated from these environments were described within the frame of this thesis. It could be shown that concentrations up to 1 wt% of Mars regolith analogs added to the growth media had a positive influence on the methane production rates of the tested methanogenic archaea, whereas higher concentrations resulted in decreasing rates. Nevertheless it was possible for the organisms to metabolize when incubated on water-saturated soil matrixes made of Mars regolith analogs without any additional nutrients. Long-term desiccation resistance of more than 400 days was proven with reincubation and indirect counting of viable cells through a combined treatment with propidium monoazide (to inactivate DNA of destroyed cells) and quantitative PCR. Phyllosilicate rich regolith analogs seem to be the best soil mixtures for the tested methanogenic archaea to be active under Mars analog conditions. Furthermore, in a simulation chamber experiment the activity of the permafrost methanogen strain Methanosarcina soligelidi SMA-21 under Mars subsurface analog conditions could be proven. Through real-time wavelength modulation spectroscopy measurements the increase in the methane concentration at temperatures down to -5 °C could be detected. The results presented in this thesis contribute to the understanding of the activity potential of methanogenic archaea under Mars analog conditions and therefore provide insights to the possible habitability of present-day Mars (near) subsurface environments. Thus, it contributes also to the data interpretation of future life detection missions on that planet. For example the ExoMars mission of the European Space Agency (ESA) and Roscosmos which is planned to be launched in 2018 and is aiming to drill in the Martian subsurface
    Type of Medium: Dissertations
    Pages: VI, 108 Blätter , Illustrationen
    Language: English
    Note: Dissertation, Universität Potsdam, 2015 , Table of contents Preface Table of contents Summary Zusammenfassung 1. Introduction 1.1. Environmental conditions on past and present Mars 1.2. Detection of methane on Mars 1.3. Methanogenic archaea 1.4. Description of study sites 1.5. Aims and approaches 1.6. Overview of the publications 2. Publication I: Methanosarcina soligelidi sp. nov., a desiccationandfreeze-thaw-resistant methanogenic archaeon from a Siberianpermafrost-affected soil 3. Publication II: Methanobacterium movilense sp. nov.,ahydrogenotrophic, secondary-alcohol-utilizing methanogen fromthe anoxic sediment of a subsurface lake 4. Publication III: Influence of Martian Regolith Analogs on the activityand growth of methanogenic archaea,with special regard to long-term desiccation 5. Publication IV: Laser spectroscopic real time measurements ofmethanogenic activity under simulated Martian subsurface conditions 6. Synthesis and Conclusion 6.1. Synthesis 6.2. Conclusion and future perspectives 7. References 8. Acknowledgments
    Location: AWI Reading room
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 13
    Call number: AWI Bio-20-93993
    Type of Medium: Dissertations
    Pages: III, 127 Seiten , Illustrationen
    Language: English
    Note: Dissertation, Universität Potsdam, 2014 , Table of contents I - Abstract II - Zusammenfassung Chapter 1 - Introduction 1.1. Introduction 1.1.1 Motivation 1.1.2 Organisation of thesis 1.1 Scientific background 1.2.1 Arctic and wetland bryophytes 1.2.2 Bryophyte remains as palaeo-environmental indicators 1.2.3 Regional setting 1.3 Objectives ofthe thesis 1.4 Overview of the manuscripts 1.5 Contribution of the authors Chapter 2 - Manuscript #1 Abstract 2.1 Introduction 2.2 Geographic setting 2.3 Materials and methods 2.3.1 Fieldwork 2.3.2 Radiocarbon dating 2.3.3 Geochemical, stable carbon isotope, and granulometric analyses 2.3.4 Analyses of moss remains and vascular plant macrofossils 2.3.5 Pollen analysis 2.3.6 Diatom analysis 2.3.7 Statistical analysis 2.4 Results 2.4.1 High-resolution spatial characteristics oft the investigated polygon and vegetation pattern 2.4.2 Geochronology and age-depth relationships 2.4.3 General properties of the sedimentary fill 2.4.4 Bioindicators 2.4.5 Characterization oftwo different types of polygon pond sediment 2.5. Discussion 2.5.1 Small-scale spatial structure of polygons 2.5.2 Age-depth relationships 2.5.3 Proxy value of the analysed parameters 2.5.4 The general polygon development 2.5.5 Polygon development as a function of external controls and internal adjustment mechanisms 2.6 Conclusions Chapter 3 - Manuscript #11 Abstract 3.1 Introduction 3.2 Material und methods 3.2.1 Regional setting 3.2.3 Field methods and environmental data collection 3.2.4 Data analysis 3.3 Results 3.3.1 Major characteristics of the investigated polygons 3.3.2 Vegetation cover and its relationships with micro-relief and vegetation type 3.3.3 Vegetation alpha-diversity and its relationship with micro-relief and vegetation type 3.3.4 Vegetation composition and its relationship with micro-relief and vegetation type 3.4 Discussion 3.4.1 Patterns of cover, alpha-diversity and compositional turnover of vascular plants and bryophytes along the rim-pond transect (local-scale) 3.4.2 Patterns of cover, alpha-diversity and compositional turnover of vascular plants and bryophytes along the regional-scale forest-tundra transect 3.4.3 Indicator potential ofvascular plant and bryophyte remains from polygonal peats for the reconstruction of local hydrological and regional vegetation changes 3.4.4. Implications of the performed vegetation transect studies for future Arctic warming 3.5 Acknowledgements 2.4.4 Bioindicators 2.4.5 Characterization of two different types of polygon pond sediment 2.5. Discussion 2.5.1 Small-scale spatial structure of polygons 2.5.2 Age-depth relationships 2.5.3 Proxy value of the analysed parameters 2.5.4 The general polygon development 2.5.5 Polygon development as a function of external controls and internal adjustment mechanisms 2.6 Conclusions Chapter 3 - Manuscript #II Abstract 3.1 Introduction 3.2 Material und methods 3.2.1 Regional setting 3.2.3 Field methods and environmental data collection 3.2.4 Data analysis 3.3 Results 3.3.1 Major characteristics of the investigated polygons 3.3.2 Vegetation cover and its relationships with micro-relief and vegetation type 3.3.3 Vegetation alpha-diversity and its relationship with micro-relief and vegetation type 3.3.4 Vegetation composition and its relationship with micro-relief and vegetation type 3.4 Discussion 3.4.1 Patterns of cover, alpha-diversity and compositional turnover of vascular plants and bryophytes along the rim-pond transect (local-scale) 3.4.2 Patterns of cover, alpha-diversity and compositional turnover of vascular plants and bryophytes along the regional-scale forest-tundra transect 3.4.3 Indicator potential of vascular plant and bryophyte remains from polygonal peats for the reconstruction of local hydrological and regional vegetation changes 3.4.4. Implications of the performed vegetation transect studies for future Arctic warming 3.5 Acknowledgements Chapter 4 - Manuscript #3 Abstract 4.1 Introduction 4.2 Material and methods 4.2.1 Sites 4.2.2 Sampling 4.2.3 Investigated moss species 4.2.4 Measurements 4.2.5 Statistical Tests 4.3 Results 4.4 Discussion Chapter 5 - Discussion 5.1 Bryophytes of polygonal landscapes in Siberia 5.1.1 Modern bryophytes in the Siberian Arctic 5.1.2 Biochemical and isotopic characteristics of mosses 5.1.3 Reliability and potential of fossil bryophyte remains as palaeoproxies 5.2 Dynamics of low-centred polygons during the late Holocene 5.3 Outlook Appendix I - Preliminary Report Motivation Material and methods Results and first interpretation Appendix II Additional tables and figures of manuscript #1 Appendix III Additional figures of manuscript #2 Appendix IV - Quantitative approach of Standard Moss Stem (SMS3) Bibliography Acknowledgements Eidesstattliche Erklärung
    Location: AWI Reading room
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 14
    Call number: AWI Bio-20-93994
    Type of Medium: Dissertations
    Pages: viii, 140 Seiten , Illustrationen, Diagramme
    Language: English
    Note: Dissertation, Universität Potsdam, 2017 , Table of Contents I. Abstract II. Deutsche Zusammenfassung 0 Challenge 1 Introduction 1.1 The treeline ecotone 1.2 Stand structure drivers in the treeline ecotone 1.3 Climate change and recent treeline changes 1.4 Methods for treeline studies 1.4.1 Overview 1.4.2 Field-based treeline studies 1.4.3 Modelling treeline dynamics 1.5 Study Area 1.6 The Siberian treeline ecotone 1.7 Larix as study Species 1.8 Objectives of this thesis 1.9 Thesis outline 1.10 Contribution of the authors 1.10.1 Manuscript!- published 1.10.2 Manuscript II - submitted 1.10.3 Manuscript III-in preparation 1.10.4 Manuscript IV-submitted 2 Manuscript I Treeline dynamics in Siberia under changing climates as inferred from an individual-based model for Larix 2.1 Abstract 2.2 Introduction 2.3 Materials and Methods 2.3.1 Reference sites 2.3.2 Description of the model LAVESI 2.3.3 The ODD-Protocol for LAVESI 2.3.4 Parameterization 2.3.5 Khatanga climate time-series 2.3.6 Sensitivity analysis 2.3.7 Model experiments 2.4 Results 2.4.1 Sensitivity analysis 2.4.2 Taymyr treeline application 2.4.3 Temperature experiments 2.5 Discussion 2.5.1 Assessment of LAVESI sensitivity 2.5.2 Larix stand simulation under the Taymyr Peninsula weather 2.5.3 Transient Larix response to hypothetical future temperature changes 2.5.4 Conclusions 2.6 Acknowledgements 3 Manuscript II Dissimilar responses of larch stands in northern Siberia to increasing temperatures - a field and simulation based study 3.1 Abstract 3.2 Introduction 3.3 Methods 3.3.1 Study area 3.3.2 Field-based approach 3.3.3 Age analyses 3.3.4 Stand structure analyses 3.3.5 Seed analyses 3.3.6 Establishment history 3.3.7 Modelling approach 3.4 Results 3.4.1 Field data 3.4.2 Simulation study 3.5 Discussion 3.5.1 Data acquisition 3.5.2 Larch-stand patterns across the Siberian treeline ecotone 3.5.3 Warming causes densification in the forest-tundra 3.5.4 Intra-specific competition inhibits densification in the closed forest 3.5.5 Recruitment limitation decelerates densification and northward expansion ofthe single-tree tundra 3.6 Conclusions 3.7 Acknowledgements 4 Manuscript III Spatial patterns and growth sensitivity of larch stands in the Taimyr Depression 4.1 Abstract 4.2 Introduction 4.3 Methods 4.3.1 Study Area 4.3.2 Field data collection 4.3.3 Spatial point patterns 4.3.4 Dendrological approach 4.4 Results 4.4.1 Spatial patterns 4.4.2 Tree growth 4.5 Discussion 4.5.1 Spatial patterns 4.5.2 Tree chronology characteristics 4.6 Conclusion 5 Manuscript IV Patterns of larch stands under different disturbance regimes in the lower Kolyma River area (Russian Far East) 5.1 Abstract 5.2 Introduction 5.3 Methods 5.3.1 Study area and field data collection 5.3.2 Site description 5.3.3 Dendrochronological approach 5.3.4 Statistical analyses 5.4 Results 5.4.1 General stand characteristics and age structure 5.4.2 Spatial patterns 5.5 Discussion 5.5.1 Fire related disturbances 5.5.2 Water-related disturbances: lake drainage, flooding, polygon development 5.5.3 Implications and conclusion 6 Synthesis and Discussion 6.1 Assessment of applied methods 6.1.1 Field-based observations: 6.1.2 Modelling 6.2 Overview of larch stand structures and spatial pattern on different spatial scales 6.2.1 Recent stand structures 6.2.2 Spatial Patterns 6.3 Stand structure drivers and treeline changes 6.3.1 Climate change 6.3.2 Disturbances 6.3.3 Autecology 6.4 Conclusion 6.5 Outlook 7 Appendix 7.1 Supplementary information for Manuscript I 7.2 Supplementary information for Manuscript II 7.2.1 Manuscript II: Appendix 1. Climatic information for the study region 7.2.2 Manuscript II: Appendix 2. Plot-specific values and krummholz appearance 7.2.3 Manuscript II: Appendix 3. Regression analysis for age data 7.2.4 Manuscript II: Appendix 4. Model description 7.3 Supplementary information for Manuscript III 7.4 Supplementary information for Manuscript IV 7.5 Supplementary information 8 References Danksagung Eidesstattliche Erklärung
    Location: AWI Reading room
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 15
    Call number: AWI Bio-20-93992
    Type of Medium: Dissertations
    Pages: XIII, 137 Seiten , Illustrationen, Diagramme , 1 CD-ROM
    Language: English
    Note: Dissertation, Universität Potsdam, 2017 , Content List of Abbreviations List of Figures List of Tables Summary Zusammenfassung Motivation Chapter 1 1. Scientific background 1.1 Late Quaternary climate changes and treeline transition in northern Siberia 1.2 Natural archives and proxies to assess vegetation history 1.3 Study area 1.3 Objectives of the thesis 1.4 Thesis outline 1.4.1 Chapters and manuscripts 1.4.2 Author's contribution 1.4.2.1 Manuscript I - published 1.4.2.2 Manuscript II - submitted 1.4.2.3 Manuscript III - prepared for submission Chapter 2 2. Manuscript I: Sedimentary ancient DNA and pollen reveal the composition of plant organic matter in Late Quaternary permafrost sediments of the Buor Khaya Peninsula (north-eastern Siberia) 2.1 Abstract 2.2 Introduction 2.3 Geographical settings 2.4 Material and methods 2.4.1 Core material 2.4.2 Subsampling of the permafrost core 2.4.3 Molecular genetic laboratory work 2.4.4 Analysis of sequence data and taxonomic assignments 2.4.5 Pollen sample treatment and analysis 2.4.6 Statistical analyses and visualization 2.5 Results 2.5.1 SedaDNA 2.5.1.1 SedaDNA of terrestrial plants 2.5.1.2 SedaDNA of swamp and aquatic plants 2.5.1.3 SedaDNA of bryophytes and algae 2.5.2 Pollen 2.5.2.1 Pollen of terrestrial plants 2.5.2.2 Pollen and spores of swamp and aquatic plants 2.5.2.3 Spores and algae 2.5.3 Ratios of terrestrial to swamp and aquatic taxa and Poaceae to Cyperaceae 2.6 Discussion 2.6.1 Quality and proxy value of sedaDNA and pollen data 2.6.2 Environmental conditions during the pre-LGM (54-51 kyr BP, 18.9-8.35 m) and composition of deposited organic matter 2.6.3 Environmental conditions during the post-LGM (11.4-9.7 kyr BP (13.4-11.1 cal kyr BP)) and composition of deposited organic matter 2.7 Conclusions 2.8 Acknowledgements Chapter 3 3. Manuscript II: Genetic variation of larches at the Siberian tundra-taiga ecotone inferred from the assembly of chloroplast genomes and mitochondrial sequences 3.1. Abstract 3.2. Introduction 3.3. Material and methods 3.3.1 Plant material 3.3.2 DNA isolation and sequencing 3.3.3 Sequence processing and de novo assembly 3.3.4 Chloroplast genome assembly, annotation and variant detection 3.3.5 Mitochondrial sequences 3.3.6 Analyses of genetic variation 3.4 Results 3.4.1 Chloroplast genome structure and genetic variation 3.4.2 Mitochondrial sequences and genetic variation 3.5 Discussion 3.5.1 De novo assembly and genetic variation of chloroplast genomes and mitochondrial sequences 3.5.2 The distribution of genetic variation at the tundra-taiga ecotone 3.6 Conclusions 3.7 Acknowledgements Chapter 4 4. Manuscript III: The history of tree and shrub taxa and past genetic variation of larches on Bol'shoy Lyakhovsky Island (New Siberian Archipelago) since the last interglacial uncovered by sedimentary ancient DNA 4.1 Abstract 4.2 Introduction 4.3 Materials and methods 4.3.1 Geographic setting 4.3.2 Core material 4.3.2.1 Core L14-02: Yedoma Ice Complex 4.3.2.2 Core L14-03: Thermo terrace 4.3.2.3 Core L14-04 and hand-pieces L14-04B and L14-04C: Thermo terrace including Eemian deposits 4.3.2.4 Core L14-05: Alas 4.3.3 Core sub-sampling 4.3.4 Molecular genetic laboratory work 4.3.4.1 Sedimentary ancient DNA metabarcoding approach 4.3.4.2 Specific amplification of Larix from sedimentary ancient DNA 4.3.5 Filtering of Illumina sequencing data and taxonomic assignments 4.3.6 Statistical analyses and visualization 4.3.7 Geochronology 4.4. Results 4.4.1 Overall composition of the DNA metabarcoding data 4.4.2 Terrestrial vegetation composition 4.4.2.1 Core L14-02: Late Pleistocene Yedoma Ice Complex 4.4.2.2 L14-03: Deeper late Pleistocene deposits 4.4.2.3 L14-04 Thermo terrace including Eemian deposits 4.4.2.4 Core L14-05: Alas with Holocene lake deposits and taberits of the Yedoma Ice Complex 4.4.2.5 The multivariate structure of the terrestrial vegetation among samples and cores 4.4.3 Genetic variation ofsediment-derived Larix sequences 4.5 Discussion 4.5.1 Tree taxa in the sedaDNA record - where do they come from? 4.5.2 Terrestrial plant community changes of warm phases since the last interglacial 4.5.3 Past genetic diversity of larch populations on Bol'shoy Lyakhovsky Island 4.6 Conclusion 4.7 Acknowledgements Chapter 5 5. Synopsis 5.1 The proxy potential of sedaDNA in paleobotanical reconstructions from sedimentary deposits 5.1.1 Combining sedaDNA and pollen to assess plant diversity and vegetation composition 5.1.2 Current limits and opportunities of sedaDNA approaches 5.2 Using genomic data to trace modern and past treeline dynamics 5.2.1 Modern genomic variation at the Siberian treeline 5.2.2 PCR-based markers for paleoenvironmental genetics 5.3 Terrestrial plant community changes and treeline dynamics in north-eastern Siberia since the last interglacial 5.3.1 Vegetation changes in north-eastern Siberia since the last interglacial 5.3.2 Implications for treeline dynamics 5.4 Conclusion 5.5 Outlook Appendix 1. Supplementary material for Manuscript I (Chapter 2) 2. Supplementary material for Manuscript II (Chapter 3) 3. Supplementary material for Manuscript III (Chapter 4) References Acknowledgements Erklärung
    Location: AWI Reading room
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 16
    Call number: AWI G3-19-92415
    Type of Medium: Dissertations
    Pages: VIII, 154, xv Seiten , Illustrationen, Diagramme, Karten
    Language: English
    Note: Table of contents Abstract Zusammenfassung 1 Motivation 2 Introduction 2.1 Arctic climate changes and their impacts on Coastal processes 2.2 Shoreline retreat along Arctic coasts 2.3 Impacts of Coastal erosion 2.3.1 Material fluxes 2.3.2 Retrogressive thaw slumps 2.3.3 Socio-economic impacts 2.4 Objectives 2.5 Study area 2.6 Thesis structure 2.7 Authors’ contributions 3 Variability in rates of Coastal change along the Yukon coast, 1951 to 2015 3.1 Introduction 3.2 Study Area 3.3 Data and Methods 3.3.1 Remote sensing data 3.3.2 Field survey data 3.3.3 Classification of shoreline 3.3.4 Transect-wise analyses of shoreline movements through time 3.4 Results 3.4.1 Temporal variations in shoreline change rates 3.4.2 Alongshore rates of change 3.4.3 Shoreline dynamics along field sites 3.4.4 Dynamics of lagoons, barrier Islands and spits (gravel features) 3.4.5 Yukon Territory land loss 3.5 Discussion 3.5.1 Temporal variations in shoreline change rates 3.5.2 Alongshore rates of change 3.5.3 Dynamics of lagoons, barrier Islands, and spits (gravel features) 3.5.4 Expected shoreline changes as a consequence of future climate warming 3.6 Conclusions Context 4 Coastal erosion of permafrost Solls along the Yukon Coastal Plain and Kuxes oforganic carbon to the Canadian Beaufort Sea 4.1 Introduction 4.2 Study Area 4.3 Methods 4.3.1 Sample collection and laboratory analyses 4.3.2 Soll organic carbon determinations 4.3.3 Flux of organic soil carbon and Sediments 4.3.4 Fate of the eroded soil organic carbon 4.4 Results 4.4.1 Ground lce 4.4.2 Organic carbon contents 4.4.3 Material fluxes 4.5 Discussion 4.5.1 Ground lce 4.5.2 Organic carbon contents 4.5.3 Material fluxes 4.5.4 Organic carbon in nearshore Sediments 4.6 Conclusion Context 5 Terrain Controls on the occurrence of Coastal retrogressive thaw slumpsalong the Yukon Coast, Canada 5.1 Introduction 5.2 Study Area 5.3 Methods 5.3.1 Mapping of RTSs and landform Classification 5.3.2 Environmental variables 5.3.3 Univariate regression trees 5.4 Results 5.4.1 Characteristics of RTS along the coast 5.4.2 Density and areal coverage od RTSs along the Yukon Coast 5.5 Discussion 5.5.1 Characteristics and distribution of RTSs along the Yukon Coast 5.5.2 Terrain factors explaining RTS occurrence 5.5.3 Coastal processes 5.6 Conclusions Context 6 Impacts of past and fiiture Coastal changes on the Yukon coast - threats forcultural sites, infrastructure and travel routes 6.1 Introduction 6.2 Study Area 6.3 Methods 6.3.1 Data for shoreline projections 6.3.2 Shoreline projection for the conservative scenario (S1) 6.3.3 Shoreline Projection for the dynamic scenario (S2) 6.3.4 Positioning and characterizing of cultural sites 6.3.5 Calculation of losses under the S1 and S2 scenarios 6.3.6 Estimation of future dynamics in very dynamic areas 6.4 Results and discussion 6.4.1 Past and future shoreline change rates 6.4.2 Cultural sites 6.4.3 Infrastructure and travel routes 6.5 Conclusions 7 Discussion 7.1 The importance of understanding climatic drivers of Coastal changes 7.2 The influence of shoreline change rates on retrogressive thaw slump activity 7.3 On the calculation of carbon fluxes from Coastal erosion along the Yukon coast 7.4 Impacts of present and future Coastal erosion on the natural and human environment 7.5 Synthesis 8 Summary and Conclusions Bibliography Supporting Material Data Set ds01 Table S1 Table S3 Abbreviations and Nomendature Acknowledgements
    Location: AWI Reading room
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 17
    Call number: AWI G3-22-94687
    Description / Table of Contents: Permafrost is warming globally, which leads to widespread permafrost thaw and impacts the surrounding landscapes, ecosystems and infrastructure. Especially ice-rich permafrost is vulnerable to rapid and abrupt thaw, resulting from the melting of excess ground ice. Local remote sensing studies have detected increasing rates of abrupt permafrost disturbances, such as thermokarst lake change and drainage, coastal erosion and RTS in the last two decades. All of which indicate an acceleration of permafrost degradation. In particular retrogressive thaw slumps (RTS) are abrupt disturbances that expand by up to several meters each year and impact local and regional topographic gradients, hydrological pathways, sediment and nutrient mobilisation into aquatic systems, and increased permafrost carbon mobilisation. The feedback between abrupt permafrost thaw and the carbon cycle is a crucial component of the Earth system and a relevant driver in global climate models. However, an assessment of RTS at high temporal resolution to determine the ...
    Type of Medium: Dissertations
    Pages: xxiv, 134 Seiten , Illustrationen, Diagramme, Karten
    Language: English
    Note: Dissertation, Universität Potsdam, 2021 , Table of Contents Abstract Zusammenfassung List of Figures List of Tables Abbreviations 1 Introduction 1.1 Scientific background and motivation 1.1.1 Permafrost and climate change 1.1.2 Permafrost thaw and disturbances 1.1.3 Abrupt permafrost disturbances 1.1.4 Remote sensing 1.1.5 Remote sensing of permafrost disturbances 1.2 Aims and objectives 1.3 Study area 1.4 General data and methods 1.4.1 Landsat and Sentinel-2 1.4.2 Google Earth Engine 1.5 Thesis structure 1.6 Overview of publications and authors’ contribution 1.6.1 Chapter 2 - Comparing Spectral Characteristics of Landsat-8 and Sentinel-2 Same-Day Data for Arctic-Boreal Regions 1.6.2 Chapter 3 - Mosaicking Landsat and Sentinel-2 Data to Enhance LandTrendr Time Series Analysis in Northern High Latitude Permafrost Regions 1.6.3 Chapter 4 - Remote Sensing Annual Dynamics of Rapid Permafrost Thaw Disturbances with LandTrendr 2 Comparing Spectral Characteristics of Landsat-8 and Sentinel-2 Same-Day Data for Arctic-Boreal Regions 2.1 Abstract 2.2 Introduction 2.3 Materials and Methods 2.3.1 Study Sites 2.3.2 Data 2.3.3 Data Processing 2.3.3.1 Filtering Image Collections 2.3.3.2 Creating L8, S2, and Site Masks 2.3.3.3 Preparing Sentinel-2 Surface Reflectance Images in SNAP 2.3.3.4 Applying Site Masks 2.3.4 Spectral Band Comparison and Adjustment 2.4 Results 2.4.1 Spectral Band Comparison 2.4.2 Spectral Band Adjustment 2.4.3 ES and HLS Spectral Band Adjustment 2.5 Discussion 2.6 Conclusions 2.7 Acknowledgements 2.8 Appendix Chapter 2 3 Mosaicking Landsat and Sentinel-2 Data to Enhance LandTrendr Time Series Analysis in Northern High Latitude Permafrost Regions 3.1 Abstract 3.2 Introduction 3.3 Materials and Methods 3.3.1 Study Sites 3.3.2 Data 3.3.3 Data Processing and Mosaicking Workflow 3.3.4 Data Availability Assessment 3.3.5 Mosaic Coverage and Quality Assessment 3.4 Results 3.4.1 Data Availability Assessment 3.4.2 Mosaic Coverage and Quality Assessment 3.5 Discussion 3.6 Conclusions 4 Remote Sensing Annual Dynamics of Rapid Permafrost Thaw Disturbances with LandTrendr 4.1 Abstract 4.2 Introduction 4.3 Study Area and Methods 4.3.1 Study area 4.3.2 General workflow and ground truth data 4.3.3 Data and LandTrendr 4.3.4 Index selection 4.3.5 Temporal Segmentation 4.3.6 Spectral Filtering 4.3.7 Spatial masking and filtering 4.3.8 Machine-learning object filter 4.4 Results 4.4.1 Focus sites 4.4.2 North Siberia 4.5 Discussion 4.5.1 Mapping of RTS 4.5.2 Spatio-temporal variability of RTS dynamics 4.5.3 LT-LS2 capabilities and limitations 4.6 Conclusion 4.7 Appendix 5 Synthesis and Discussion 5.1 Google Earth Engine 5.2 Landsat and Sentinel-2 5.3 Image mosaics and disturbance detection algorithm 5.4 Mapping RTS and their annual temporal dynamics 5.5 Limitations and technical considerations 5.6 Key findings 5.7 Outlook References Acknowledgements
    Location: AWI Reading room
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 18
    Call number: AWI Bio-22-95014
    Description / Table of Contents: The deciduous needle tree larch (Larix Mill.) covers more than 80% of the Asian boreal forests. Only a few Larix species constitute the vast forests and these species differ markedly in their ecological traits, most importantly in their ability to grow on and stabilize underlying permafrost. The pronounced dominance of the summergreen larches makes the Asian boreal forests unique, as the rest of the northern hemisphere boreal forests is almost exclusively dominated by evergreen needle-leaf forests. Global warming is impacting the whole world but is especially pronounced in the arctic and boreal regions. Although adapted to extreme climatic conditions, larch forests are sensitive to varying climatic conditions. By their sheer size, changes in Asian larch forests as range shifts or changes in species composition and the resulting vegetation-climate feedbacks are of global relevance. It is however still uncertain if larch forests will persist under the ongoing warming climate or if they will be replaced by evergreen forests. It is therefore of great importance to understand how these ecosystems will react to future climate warmings and if they will maintain their dominance. One step in the better understanding of larch dynamics is to study how the vast dominant forests developed and why they only established in northern Asia. A second step is to study how the species reacted to past changes in the climate. The first objective of this thesis was to review and identify factors promoting Asian larch dominance. I achieved this by synthesizing and comparing reported larch occurrences and influencing components on the northern hemisphere continents in the present and in the past. The second objective was to find a possibility to directly study past Larix populations in Siberia and specifically their genetic variation, enabling the study of geographic movements. For this, I established chloroplast enrichment by hybridization capture from sedimentary ancient DNA (sedaDNA) isolated from lake sediment records. The third objective was to use the established method to track past larch populations, their glacial refugia during the Last Glacial Maximum (LGM) around 21,000 years before present (ka BP), and their post-glacial migration patterns. To study larch promoting factors, I compared the present state of larch species ranges, areas of dominance, their bioclimatic niches, and the distribution on different extents and thaw depths of permafrost. The species comparison showed that the bioclimatic niches greatly overlap between the American and Asian species and that it is only in the extremely continental climates in which only the Asian larch species can persist. I revealed that the area of dominance is strongly connected to permafrost extent but less linked to permafrost seasonal thaw depths. Comparisons of the paleorecord of larch between the continents suggest differences in the recolonization history. Outside of northern Asia and Alaska, glacial refugial populations of larch were confined to the southern regions and thus recolonization could only occur as migration from south to north. Alaskan larch populations could not establish wide-range dominant forest which could be related to their own genetically depletion as separated refugial population. In Asia, it is still unclear whether or not the northern refugial populations contributed and enhanced the postglacial colonization or whether they were replaced by populations invading from the south in the course of climate warming. Asian larch dominance is thus promoted partly by adaptions to extremely continental climates and by adaptations to grow on continuous permafrost but could be also connected to differences in glacial survival and recolonization history of Larix species. Except for extremely rare macrofossil findings of fossilized cones, traditional methods to study past vegetation are not able to distinguish between larch species or populations. Within the scope of this thesis, I therefore established a method to retrieve genetic information of past larch populations to distinguish between species. Using the Larix chloroplast genome as target, I successfully applied the method of DNA target enrichment by hybridization capture on sedaDNA samples from lake records and showed that it is able to distinguish between larch species. I then used the method on samples from lake records from across Siberia dating back up to 50 ka BP. The results allowed me to address the question of glacial survival and post-glacial recolonization mode in Siberian larch species. The analyzed pattern showed that LGM refugia were almost exclusively constituted by L. gmelinii, even in sites of current L. sibirica distribution. For included study sites, L. sibirica migrated into its extant northern distribution area only in the Holocene. Consequently, the post-glacial recolonization of L. sibirica was not enhanced by northern glacial refugia. In case of sites in extant distribution area of L. gmelinii, the absence of a genetic turn-over point to a continuous population rather than an invasion of southern refugia. The results suggest that climate has a strong influence on the distribution of Larix species and that species may also respond differently to future climate warming. Because species differ in their ecological characteristics, species distribution is also relevant with respect to further feedbacks between vegetation and climate. With this thesis, I give an overview of present and past larch occurrences and evaluate which factors promote their dominance. Furthermore, I provide the tools to study past Larix species and give first important insights into the glacial history of Larix populations.
    Type of Medium: Dissertations
    Pages: x, 121 Seiten , Illustrationen
    Language: English
    Note: Dissertation, Universität Potsdam, 2022 , Table of Contents Summary Deutsche Zusammenfassung Table of Contents 1 Introduction 1.1 Larix forests in a changing climate 1.2 The genus Larix 1.3 Larix distribution in the world and their dominance in northern Asia 1.4 Methods to study past species dynamics 1.4.1 Modern genetic marker studies 1.4.2 Lake sediments as archives of the past 1.4.3 Pollen and macrofossils 1.4.4 Metabarcoding of sedimentary ancient DNA 1.4.5 Metagenomic shotgun sequencing 1.4.6 Target enrichment by hybridization capture 1.5 Thesis Objectives 1.6 Thesis outline & author contributions 2 Manuscript I 2.1 Abstract 2.2 Introduction 2.3 Material and methods 2.3.1 Bioclimatic limits 2.3.2 Pollen, macrofossil, and DNA datasets 2.3.3 Ice sheets 2.4 Results 2.4.1 Bioclimatic limits of Larix and its distribution on permafrost 2.4.2 Glacial occurrence patterns of Larix 2.5 Discussion 2.5.1 Are differences in species bioclimatic limits responsible for disparity in Larix distribution across continents? 2.5.2 Do high latitude glacial refugia guarantee larch dominance? 2.5.3 What role does postglacial migration play in larch dominance? 2.5.4 Fire as an additional factor 2.5.5 Outlook 2.6 Conclusion 2.7 Acknowledgements 2.8 Author contributions 2.9 References 3 Manuscript II 3.1 Abstract 3.2 Introduction 3.3 Methods 3.3.1 Sample material 3.3.2 Laboratory work 3.3.3 Data analysis 3.4 Results 3.4.1 Overview of the shotgun and hybridization capture data sets 3.4.2 Ancient DNA authenticity 3.4.3 Retrieval of the Larix chloroplast genome 3.5 Discussion 3.5.1 Taxonomic classification—conservative approach results in low numbers of assignment 3.5.2 Target enrichment success—Larix reads increased by orders of magnitude along with other taxonomic groups 3.5.3 Complete retrieval of ancient Larix chloroplast genomes 3.5.4 Larix sibirica variants present over time 3.5.5 Larch forest decline over the last 7000 years 3.6 Conclusion 3.7 Acknowledgments 3.8 Author contributions 3.9 References 4 Manuscript III 4.1 Abstract 4.2 Introduction 4.3 Results & Discussion 4.3.1 Chloroplast and repetitive DNA enrichment in the sedaDNA samples 4.3.2 A wider pre-glacial distribution of L. sibirica 4.3.3 Larix gmelinii formed northern LGM refugia across Siberia 4.3.4 Postglacial colonization history - differences among larch species 4.3.5 Environment likely plays a more important role than biogeography 4.4 Conclusion 4.5 Material & methods 4.5.1 Sample material 4.5.2 Sequence data analysis 4.6 Data availability 4.7 Acknowledgments 4.8 Author contributions 4.9 References 5 Discussion and synthesis 5.1 Hybridization capture is a well-suited method to study ancient species dynamics 5.1.1 Advantages and limitations of shotgun sequencing 5.1.2 Successful hybridization capture enrichment using chloroplast DNA 5.1.3 Challenges in single-copy target enrichment 5.1.4 Limitations and potentials to improve sedaDNA capture studies 5.2 Factors promoting Asian larch dominance 5.3 Drivers of Larix species distribution 5.3.1 Implications for larch forests under climate warming 5.4 Conclusion 5.5 Outlook 6 References 7 Appendix 7.1 Appendix to manuscript I 7.2 Appendix to manuscript II 7.3 Appendix to manuscript III 7.3.1 Material and Methods 7.3.2 Additional Results & Discussions 7.3.3 References Acknowledgements Eidesstattliche Erklärung
    Location: AWI Reading room
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 19
    Call number: AWI A8-20-93986
    Type of Medium: Dissertations
    Pages: VI, 129 Seiten , Diagramme
    Language: German
    Note: Inhaltsverzeichnis Kurzfassung Abstract 1 EINFÜHRUNG 2 GRUNDLAGEN 2.1 Allgemeine Zirkulation 2.2 Barokline Instabiltät 2.3 Horizontale und vertikale Wellenausbreitung 2.4 Die Rolle der Arktis im Klimasystem 2.5 Einfluss des klimatischen Wandels in der Arktis auf die mittleren Breiten 2.6 Atmosphärisches Energiespektrum und Skalenwechselwirkung 3 DATEN UND METHODEN 3.1 Verwendete Reanalyse- und Modelldaten 3.1.1 ERA-Interim 3.1.2 AFES 3.1.3 Aufteilung der verwendeten Daten in Zeiträume mit hoher und niedriger Meereisbedeckung 3.2 Methoden 3.2.1 Instabilitätsanalyse für einen zonalgemittelten Grundzustand 3.2.2 Identifikation bevorzugter großskaliger Zirkulationsmuster 3.2.3 Energie- und Enstrophiespektren 3.2.4 Statistische Testverfahren 4 ERGEBNISSE 4.1 Instabilitätsanalyse für einen zonalgemittelten Grundzustand . 4.1.1 Klimatologie ERA-Interim und AFES 4.1.2 Sensititvitätsstudie 4.2 Identifikation bevorzugter großskaliger Zirkulationsmuster 4.2.1 September 4.2.2 Oktober 4.2.3 November 4.2.4 Dezember 4.2.5 Januar 4.2.6 Februar 4.2.7 Zugehörige synoptisch-skalige Aktivität und 2m-Temperatur 4.3 Kinetische Energiespektren und nichtlineare Wechselwirkungen 4.3.1 Kinetische Energiespektren 4.3.2 Enstrophiespektren 4.3.3 Nichtlineare Energiewechselwirkungen, Energieflüsse und Enstrophieflüsse 5 ZUSAMMENFASSUNG UND AUSBLICK Tabellenverzeichnis Abbildungsverzeichnis Variablen und Symbole Literaturverzeichnis Danksagung Anhang A.1 Hough-Funktionen und vertikale Strukturfunktionen A.2 Zugeordnete Legendre-Polynome und Kugelflächenfunktionen Eidesstattliche Erklärung
    Location: AWI Reading room
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 20
    Call number: AWI G5-20-94097
    Type of Medium: Dissertations
    Pages: vi, 127 Seiten , Illustrationen, Diagramme, Karten
    Language: English
    Note: Dissertation, Universität Potsdam, 2020 , Table of contents Abstract Kurzfassung Table of contents Chapter 1: Introduction 1.1 The challenge of proxy uncertainties 1.2 Aims and approaches 1.3 Thesis outline and author's contributions Chapter 2: Comparing methods for analysing time scale dependent correlations in irregularly sampled time series data 2.1 Abstract 2.2 Introduction 2.3 Methods 2.3.1 Time scale dependency 2.3.2 Irregularity 2.3.3 Surrogate data 2.3.3.1 Construction of surrogate signals 2.3.3.2 Construction of irregular sampling 2.3.4 Evaluation of the estimation methods 2.4 Results 2.4.1 Correlation of red signal - white noise time series 2.4.2 Correlation of white signal - white noise time series 2.5 Discussion 2.5.1 Effect of irregularity and non-simultaneousness in sampling 2.5.2 Choosing the best method 2.5.2.1 Handling irregularity 2.5.2.2 Accounting for time scale dependency 2.5.3 Example application to observed proxy records 2.6 Conclusion 2.7 Computer code availability 2.8 Acknowledgements 2.9 Appendix 2-A. Significance test for time scale dependent correlation estimates Chapter 3: Empirical estimate of the signal content of Holocene temperature proxy records 3.1 Abstract 3.2 Introduction 3.3 Data 3.3,1 Proxy records 3.3.2 Climate model simulations 3.4 Method 3.4.1 Approach and assumptions 3.4.2 Spatial correlation structure of model vs. reanalysis data 3.4.3 Processing steps 3.4.3.1 Estimation of the spatial correlation structure 3.4.3.2 Estimation of the SNRs 3.5 Results 3.5.1 Spatial correlation structure and correlation decay length 3.5.2 SNR estimates 3.6 Discussion 3.6.1 Spatial correlation structure of model simulations 3.6.2 Finite number of proxy records 3.6.3 Proxy-specific recording of climate variables 3.6.4 Time uncertainty and non-climatic components of the proxy signal 3.6.5 Implications and future steps forward 3.7 Conclusion 3.8 Code availability 3.9 Data availability 3.10 Acknowledgements Chapter 4: Testing the consistency of Holocene and Last Glacial Maximum spatial correlations in temperature proxy records 4.1 Abstract 4.2 Introduction 4.3 Data 4.4 Method 4.4.1 Approach and assumptions 4.4.2 Holocene and LGM spatial correlation structure from climate model simulation 4.4.3 Effect of changes in climate variability on the predicted correlations 4.4.4 Effect of changes in time uncertainty on the predicted correlations 4.4.S Estimating the surrogate-based LGM spatial correlation and accounting for parameter uncertainty 4.5 Results 4.6 Discussion 4.6.1 Proxy-specific recording and finite number of records 4.6.2 Time uncertainty of proxy records 4.6.3 Contrary behaviour of U K'37 records 4.6.4 Spatial correlation structure and orbital trends 4.7 Conclusion 4.8 Acknowledgements 4.9 Appendix 4-A. Deriving the effect of a different signal variance on the correlation Chapter 5: Synthesis 5.1 Irregular sampling and time scale dependent correlations 5.2 Spatial correlation structure of proxy records 5.3 Consistency of spatial correlations for different climate states 5.4 Signal content of proxy records 5.5 Concluding remarks and Outlook Chapter A: Supplement of Chapter 3 - Empirical estimate of the signal content of Holocene temperature proxy records A.1 Supplementary Figures A.2 Supplementary Tables Chapter B: Supplement of Chapter 4 - Testing the consistency of Holocene and Last Glacial Maximum spatial correlations of temperature proxy records 8.1 Supplementary Figures 8.2 Supplementary Tables References Danksagung Eidesstattliche Erklärung
    Location: AWI Reading room
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...