Kooperativer Bibliotheksverbund

UID:

Format: xi, 121 Seiten , Diagramme, Illustrationen

Content: 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. [...]

Note: Dissertation Universität Potsdam 2022

Additional Edition: Erscheint auch als Online-Ausgabe Schulte, Luise Dynamics of Larix (Mill.) species in Siberia during the last 50,000 years inferred from sedimentary ancient DNA Potsdam, 2022

Language: English

Keywords: Hochschulschrift ; Hochschulschrift ; Hochschulschrift

URL: https://doi.org/10.25932/publishup-55878

UID:

Format: iv, 26 Seiten , Illustrationen

Series Statement: CRREL Report 83-29

Content: A literature review indicated that the effects or permafrost on streambank erodibility and stability are not yet understood because systematic and quantitative measurements are seriously lacking. Consequently, general controversy exists as to whether perennially frozen ground inhibits lateral erosion and bankline recession, or whether it increases bank recession rates. Perennially frozen streambanks erode because of modification of the bank's thermal regime by exposure to air and water, and because of various erosional processes. Factors that determine rates and locations of erosion include physical, thermal and structural properties of bank sediments, stream hydraulics and climate. Thermal and physical modification of streambanks may also induce accelerated erosion within permafrost terrain removed from the immediate river environment. Bankline or bluffline recession rates are highly variable, ranging from less than 1 m/year to over 30 m/year and, exceptionally, to over 60 m/year. Long-term observations of the physical and thermal erosion processes and systematic ground surveys and measurements of bankline-bluffline recession rates are needed.

Note: CONTENTS Abstract Preface Introduction Stream bank erosional processes Permafrost and related factors Permafrost and erosion General Erosional processes Bank zone processes Bluff zone processes Factors affecting perm afrost erodibility Exposure to currents and wind waves Texture and stratigraphy Ice content, distribution and type Slope aspect Coriolis force Timing and depth of thaw Water level and temperature Vegetation Ice and snow cover Groundwater Rates and timing of erosion and recession Overall effects of permafrost Recommendations for research Literature cited Appendix A : Processes of stream bank modifications

In: CRREL Report, 83-29

Language: English

Keywords: Forschungsbericht

URL: https://apps.dtic.mil/docs/citations/ADA138410

URL: https://hdl.handle.net/11681/9290

UID:

Format: v, 34 Seiten , Illustrationen

Series Statement: CRREL Report 85-1

Content: An expensive drill has been modified to provide researchers with the ability to auger an open hole or to acquire continuous, undisturbed 76-mm-diam core samples of a variety of perennially frozen materials that are suitable for chemical and petrographic analysis. It was developed by field testing in support of research from 1980 to 1983. Operation of the drill is based mainly on using a minimum of power to cut through frozen ground with tungsten carbide cutters on a CRREL coring auger. The ice content, temperature and grain size of the frozen sediments are important variables determining the sampling depth. Perennially frozen sediments with temperatures in the range of -0.5 C to -8.5 C have been continuously cored with this drill. Drilling and sampling are most efficiently conducted when ambient air temperatures are below freezing and the active layer is frozen. The self-contained lightweight drill is readily transportable off-road by helicopter or tracked vehicle, or by towing over roads. It is locally self-mobile by use of a winch. Total cost of the drill and modifications is estimated at approximately $10,000.

Note: CONTENTS Abstract Preface Introduction Background on development Drill development and configuration Equipment Modifications Operations Assembly and disassembly Field transport and movement Typical operating procedures Effect of material properties, weather and water Depth and hole completion time Summary Literature cited

In: CRREL Report, 85-1

Language: English

Keywords: Forschungsbericht

URL: https://apps.dtic.mil/docs/citations/ADA152388

URL: https://hdl.handle.net/11681/9352

UID:

Format: xix, 223 Seiten , Illustrationen, Diagramme

Content: The concept of hydrologic connectivity summarizes all flow processes that link separate regions of a landscape. As such, it is a central theme in the field of catchment hydrology, with influence on neighboring disciplines such as ecology and geomorphology. It is widely acknowledged to be an important key in understanding the response behavior of a catchment and has at the same time inspired research on internal processes over a broad range of scales. From this process-hydrological point of view, hydrological connectivity is the conceptual framework to link local observations across space and scales. This is the context in which the four studies this thesis comprises of were conducted. The focus was on structures and their spatial organization as important control on preferential subsurface flow. Each experiment covered a part of the conceptualized flow path from hillslopes to the stream: soil profile, hillslope, riparian zone, and stream. For each study site, the most characteristic structures of the investigated domain and scale, such as slope deposits and peat layers were identified based on preliminary or previous investigations or literature reviews. Additionally, further structural data was collected and topographical analyses were carried out. [...]

Note: Kumulative Dissertation , Dissertation Universität Potsdam 2018

Additional Edition: Erscheint auch als

Language: English

Keywords: Hochschulschrift

DOI: 10.25932/publishup-42454

URN: urn:nbn:de:kobv:517-opus4-424542

URL: http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-424542

Author information: Blume, Theresa

Author information: Merz, Bruno

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Format: iii, 16 Seiten , Illustrationen

Series Statement: CRREL Report 81-27

Content: Existing classifications for deposits in the glacial environment are inadequate and inconsistent. Deposits should be classified both descriptively and genetically; adequate descriptive classifications already exist. A major problem for previous genetic classifications has been that glacial deposition and the resulting deposits' properties were poorly understood. On the basis of three criteria-sediment source, uniqueness to the glacial environment, and preservation of glacier-derived properties-deposits in the glacial environment result from either of two groups of processes: primary or secondary. Primary processes release the debris of the glacier directly and form deposits that may bear properties related to the glacier and its mechanics. Their deposits are classified genetically as till and are the only deposits indicative of glaciation. In contrast, secondary processes mobilize, rework, transport and resediment debris and deposits in the glacial environment. They develop new, nonglacial properties in their deposits, while destroying or substantially modifying glacier-derived properties. Interpretation of their properties may provide information on the depositional are classified genetically according to the depositional process just as they are in other sedimentary environments. This genetic classification differs from previous classifications in that not all diamictons deposited in the glacial environment are classified as till; it is based strictly on process-related criteria. The origin of properties of glacial deposits in relation to the glacier's mechanics and environment must be recognized if the mechanisms and depositional processes of former glaciers are to be precisely understood.

Note: CONTENTS Abstract Preface Introduction Criteria for process grouping Depositional processes Deposit groups-tills and nontills Comparison of melt-out and sediment flow Melt-out Sediment flow Classification of glacial deposits Conclusions Literature cited

In: CRREL Report, 81-27

Language: English

Keywords: Forschungsbericht

URL: https://hdl.handle.net/11681/9444

UID:

Format: VI, 108 Blätter , Illustrationen

Content: 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

Note: kumulative Dissertation , 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

Language: English

Keywords: Hochschulschrift

URN: urn:nbn:de:kobv:517-opus4-73010

URL: http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-73010

UID:

Format: xx, 167 Seiten : Illustrationen, Diagramme

Content: Throughout the last ~3 million years, the Earth's climate system was characterised by cycles of glacial and interglacial periods. The current warm period, the Holocene, is comparably stable and stands out from this long-term cyclicality. However, since the industrial revolution, the climate has been increasingly affected by a human-induced increase in greenhouse gas concentrations. While instrumental observations are used to describe changes over the past ~200 years, indirect observations via proxy data are the main source of information beyond this instrumental era. These data are indicators of past climatic conditions, stored in palaeoclimate archives around the Earth. The proxy signal is affected by processes independent of the prevailing climatic conditions. In particular, for sedimentary archives such as marine sediments and polar ice sheets, material may be redistributed during or after the initial deposition and subsequent formation of the archive. This leads to noise in the records challenging reliable reconstructions on local or short time scales. This dissertation characterises the initial deposition of the climatic signal and quantifies the resulting archive-internal heterogeneity and its influence on the observed proxy signal to improve the representativity and interpretation of climate reconstructions from marine sediments and ice cores. To this end, the horizontal and vertical variation in radiocarbon content of a box-core from the South China Sea is investigated. The three-dimensional resolution is used to quantify the true uncertainty in radiocarbon age estimates from planktonic foraminifera with an extensive sampling scheme, including different sample volumes and replicated measurements of batches of small and large numbers of specimen. An assessment on the variability stemming from sediment mixing by benthic organisms reveals strong internal heterogeneity. Hence, sediment mixing leads to substantial time uncertainty of proxy-based reconstructions with error terms two to five times larger than previously assumed. A second three-dimensional analysis of the upper snowpack provides insights into the heterogeneous signal deposition and imprint in snow and firn. A new study design which combines a structure-from-motion photogrammetry approach with two-dimensional isotopic data is performed at a study site in the accumulation zone of the Greenland Ice Sheet. The photogrammetry method reveals an intermittent character of snowfall, a layer-wise snow deposition with substantial contributions by wind-driven erosion and redistribution to the final spatially variable accumulation and illustrated the evolution of stratigraphic noise at the surface. The isotopic data show the preservation of stratigraphic noise within the upper firn column, leading to a spatially variable climate signal imprint and heterogeneous layer thicknesses. Additional post-depositional modifications due to snow-air exchange are also investigated, but without a conclusive quantification of the contribution to the final isotopic signature. Finally, this characterisation and quantification of the complex signal formation in marine sediments and polar ice contributes to a better understanding of the signal content in proxy data which is needed to assess the natural climate variability during the Holocene.

Note: Dissertation, Universität Potsdam, 2023 (publikationsbasierte Dissertation) , CONTENTS 1 Introduction 1.1 Introduction to climate reconstructions 1.1.1 Radiocarbon as a tracer of time 1.1.2 Environmental information stored in snow 1.2 Challenges of climate reconstructions 1.2.1 The particle flux 1.2.2 Modifications after the initial deposition 1.2.3 Sampling and measurement uncertainty 1.3 Objectives and overview of the thesis 1.4 Author contributions to the Manuscripts 2 Age-heterogeneity in marine sediments revealed by three-dimensional high-resolution radio-carbon measurements 2.1 Introduction 2.2 Methods 2.2.1 Study approach 2.2.2 Core setup and sampling 2.2.3 Estimation of the sediment accumulation rate 2.2.4 Estimation of the sediment mixing strength 2.2.5 Estimation of the net sediment displacement 2.2.6 Visual assessment of mixing 2.3 Results 2.3.1 Radiocarbon measurements 2.3.2 Sediment accumulation rate 2.3.3 Sediment mixing estimates 2.3.4 Spatial structure of sediment mixing 2.3.5 Components of age uncertainty 2.4 Discussion 2.4.1 Spatial scale of sediment heterogeneity 2.4.2 Potential implications for palaeo-reconstructions 2.4.3 Suggested 14C measurement strategy 2.5 Conclusions 2.6 Supplementary Material 2.6.1 Supplementary figures and tables 2.6.2 Supplementary table 3 Local-scale deposition of surface snow on the Greenland ice sheet 3.1 Introduction 3.2 Data and methods 3.2.1 Study site 3.2.2 SfM photogrammetry 3.2.3 Additional snow height and snowfall data 3.2.4 Estimation of surface roughness 3.3 Results 3.3.1 Relative snow heights from DEMs 3.3.2 Temporal snow height evolution 3.3.3 Day-to-day variations of snowfall 3.3.4 Changes in surface roughness 3.3.5 Implied internal structure of the snowpack 3.4 Discussion 3.4.1 Changes of surface structures 3.4.2 Implications for proxy data 3.4.3 Implications for snow accumulation 3.4.4 SfM as an efficient monitoring tool 3.5 Conclusions 3.6 Appendix 3.6.1 Additional information 3.6.2 Accuracy estimates and validation 3.6.3 Validation 3.6.4 Overall snow height evolution 3.6.5 Surface roughness 4 A snapshot on the buildup of the stable water isotopic signal in the upper snowpack at east-grip, Geenland ice sheet 4.1 Introduction 4.2 Methods and data 4.2.1 Study site 4.2.2 DEM generation 4.2.3 Isotope measurements 4.2.4 Simulation of the snowpack layering 4.2.5 Expected uncertainty 4.3 Results 4.3.1 Snow height evolution 4.3.2 Mean isotopic records 4.3.3 Combining isotopic data with snow height information 4.3.4 Observed vs. simulated composition 4.3.5 Changes in the isotope signal over time 4.4 Discussion 4.4.1 Evolution of the snow surface 4.4.2 Two-dimensional view of isotopes in snow 4.4.3 Buildup of the snowpack isotopic signal 4.5 Conclusion 5 General discussion and conclusions 5.1 Heterogeneity in sedimentary archives 5.1.1 Quantifying archive-internal heterogeneity 5.1.2 Relation between signal and heterogeneity 5.2 Methods to improve climate reconstructions 5.3 Implications for climate reconstructions 5.4 Concluding remarks Bibliography A the role of sublimation as a driver of climate signals in the water isotope content of surface snow: laboratory and field experimental results A.1 Introduction A.2 Methods A.2.1 Laboratory experimental methods A.2.2 Field experimental methods A.3 Results A.3.1 Laboratory experiments A.3.2 Field experiments A.4 Discussion A.5 Conclusions B Atmosphere-snow exchange explains surface snow isotope variability Acknowledgments Eidesstattliche Erklärung

Language: English

Keywords: Hochschulschrift

URL: https://doi.org/10.25932/publishup-58286

UID:

Format: iii, 41 Seiten , Illustrationen

Series Statement: CRREL Report 80-4

Content: The primary objectives of this study were to 1) prepare a map from Landsat imagery of the Upper Susitna River Basin drainage network, lakes, glaciers and snowfields, 2) identify possible faults and lineaments within the upper basin and within a 100-km radius of the proposed Devil Canyon and Watana dam sites as observed on Landsat imagery, and 3) prepare a Landsat-derived map showing the distribution of surficial geologic materials and poorly drained areas. The EROS Digital Image Enhancement System (EDIES) provided computer- enhanced images of Landsat-1 scene 5470-19560. The EDIES false color composite of this scene was used as the base for mapping drainage network, lakes, glaciers and snowfields, six surficial geologic materials units and poorly drained areas. We used some single-band and other color composites of Landsat images during interpretation. All the above maps were prepared by photointerpretation of Landsat images without using computer analysis, aerial photographs, field data, or published reports. These other data sources were used only after the mapping was completed to compare and verify the information interpreted and delineations mapped from the Landsat images. Four Landsat-1 MSS band 7 winter scenes were used in the photomosaic prepared for the lineament mapping. We mapped only those lineaments related to reported regional tectonics, although there were many more lineaments evident on the Landsat photomosaic.

Note: CONTENTS Abstract Preface Summary Objectives Conclusions Introduction Background Previous cooperative investigations Project rationale and coordination Approach Landsat imagery Interpretation techniques Part I. Use of Landsat imagery in mapping the drainage network, lakes, glaciers and snowfields (Lawrence W. Gatto) Objective Methods Results Conclusions Part II. Use of Landsat imagery in mapping and evaluating geologiclineaments and possible faults (Carolyn J. Merry) Objective Geologic structure Methods Results Conclusions Part Ill. Use of Landsat imagery in mapping surficial materials Section A. Landsat mapping (Harlan L. McKim) Objective Methods Results Section B. Field evaluation (Daniel E. Lawson) Objectives Methods Results Discussion Section C. Conclusions (Daniel E. Lawson and Harlan L. McKim) Literature cited Glossary

In: CRREL Report, 80-4

Language: English

Keywords: Forschungsbericht

URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a084900.pdf

URL: https://hdl.handle.net/11681/9039

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Format: x, 136 Seiten , Illustrationen, Diagramme, Karten

Content: Over the last decades, the rate of near-surface warming in the Arctic is at least double than elsewhere on our planet (Arctic amplification). However, the relative contribution of different feedback processes to Arctic amplification is a topic of ongoing research, including the role of aerosol and clouds. Lidar systems are well-suited for the investigation of aerosol and optically-thin clouds as they provide vertically-resolved information on fine temporal scales. Global aerosol models fail to converge on the sign of the Arctic aerosol radiative effect (ARE). In the first part of this work, the optical and microphysical properties of Arctic aerosol were characterized at case study level in order to assess the short-wave (SW) ARE. A long-range transport episode was first investigated. Geometrically similar aerosol layers were captured over three locations. Although the aerosol size distribution was different between Fram Strait(bi-modal) and Ny-Ålesund (fine mono-modal), the atmospheric column ARE was similar. The latter was related to the domination of accumulation mode aerosol. Over both locations top of the atmosphere (TOA) warming was accompanied by surface cooling. Subsequently, the sensitivity of ARE was investigated with respect to different aerosol and spring-time ambient conditions. A 10% change in the single-scattering albedo (SSA) induced higher ARE perturbations compared to a 30% change in the aerosol extinction coefficient. With respect to ambient conditions, the ARETOA was more sensitive to solar elevation changes compared to AREsur f ace. Over dark surfaces the ARE profile was exclusively negative, while over bright surfaces a negative to positive shift occurred above the aerosol layers. Consequently, the sign of ARE can be highly sensitive in spring since this season is characterized by transitional surface albedo conditions. As the inversion of the aerosol microphysics is an ill-posed problem, the inferred aerosol size distribution of a low-tropospheric event was compared to the in-situ measured distribution. Both techniques revealed a bi-modal distribution, with good agreement in the total volume concentration. However, in terms of SSA a disagreement was found, with the lidar inversion indicating highly scattering particles and the in-situ measurements pointing to absorbing particles. The discrepancies could stem from assumptions in the inversion (e.g. wavelength-independent refractive index) and errors in the conversion of the in-situ measured light attenuation into absorption. Another source of discrepancy might be related to an incomplete capture of fine particles in the in-situ sensors. The disagreement in the most critical parameter for the Arctic ARE necessitates further exploration in the frame of aerosol closure experiments. Care must be taken in ARE modelling studies, which may use either the in-situ or lidar-derived SSA as input. Reliable characterization of cirrus geometrical and optical properties is necessary for improving their radiative estimates. In this respect, the detection of sub-visible cirrus is of special importance. The total cloud radiative effect (CRE) can be negatively biased, should only the optically-thin and opaque cirrus contributions are considered. To this end, a cirrus retrieval scheme was developed aiming at increased sensitivity to thin clouds. The cirrus detection was based on the wavelet covariance transform (WCT) method, extended by dynamic thresholds. The dynamic WCT exhibited high sensitivity to faint and thin cirrus layers (less than 200 m) that were partly or completely undetected by the existing static method. The optical characterization scheme extended the Klett–Fernald retrieval by an iterative lidar ratio (LR) determination (constrained Klett). The iterative process was constrained by a reference value, which indicated the aerosol concentration beneath the cirrus cloud. Contrary to existing approaches, the aerosol-free assumption was not adopted, but the aerosol conditions were approximated by an initial guess. The inherent uncertainties of the constrained Klett were higher for optically-thinner cirrus, but an overall good agreement was found with two established retrievals. Additionally, existing approaches, which rely on aerosol-free assumptions, presented increased accuracy when the proposed reference value was adopted. The constrained Klett retrieved reliably the optical properties in all cirrus regimes, including upper sub-visible cirrus with COD down to 0.02. Cirrus is the only cloud type capable of inducing TOA cooling or heating at daytime. Over the Arctic, however, the properties and CRE of cirrus are under-explored. In the final part of this work, long-term cirrus geometrical and optical properties were investigated for the first time over an Arctic site (Ny-Ålesund). To this end, the newly developed retrieval scheme was employed. Cirrus layers over Ny-Ålesund seemed to be more absorbing in the visible spectral region compared to lower latitudes and comprise relatively more spherical ice particles. Such meridional differences could be related to discrepancies in absolute humidity and ice nucleation mechanisms. The COD tended to decline for less spherical and smaller ice particles probably due to reduced water vapor deposition on the particle surface. The cirrus optical properties presented weak dependence on ambient temperature and wind conditions. Over the 10 years of the analysis, no clear temporal trend was found and the seasonal cycle was not pronounced. However, winter cirrus appeared under colder conditions and stronger winds. Moreover, they were optically-thicker, less absorbing and consisted of relatively more spherical ice particles. A positive CREnet was primarily revealed for a broad range of representative cloud properties and ambient conditions. Only for high COD (above 10) and over tundra a negative CREnet was estimated, which did not hold true over snow/ice surfaces. Consequently, the COD in combination with the surface albedo seem to play the most critical role in determining the CRE sign over the high European Arctic.

Note: Dissertation, Universität Potsdam, 2021 , CONTENTS 1 INTRODUCTION 1.1 Motivation: Aerosol and cloud relevance to Arctic amplification 1.2 Theoretical background 1.2.1 Atmospheric aerosol 1.2.2 Aerosol in the Arctic 1.2.3 Cirrus clouds 1.3 Research questions 2 METHODS 2.1 lidar remote sensing techniqu 2.1.1 Elastic and Raman lidar equations 2.1.2 lidar signal corrections 2.1.3 Derivation of particle optical properties and related uncertainties 2.2 Lidar systems 2.2.1 Ground-based system KARL 2.2.2 Air-borne system AMALi 2.2.3 Space-borne system CALIOP 2.3 Ancillary instrumentation 2.3.1 Radiosondes 2.3.2 Sun-photometers 2.3.3 Radiation sensors 2.4 Modeling tools 2.4.1 Air mass backward trajectories 2.4.2 Aerosol microphysics retrieval algorithm 2.4.3 Radiative transfer model SCIATRAN 2.4.4 Multiple-scattering correction model 2.4.5 Simplified cloud radiative effect model 3 ARCTIC AEROSOL PROPERTIES AND RADIATIVE EFFECT (CASE STUDIES) 3.1 Aerosol in the upper troposphere (Spring) 3.1.1 Overview of aerosol observations and air mass origin 3.1.2 Modification of aerosol optical and microphysical properties 3.1.3 Aerosol radiative effect (ARE) 3.2 Sensitivities of the spring-time Arctic ARE 3.2.1 Sensitivity on aerosol related parameters 3.2.2 Sensitivity on ambient conditions 3.3 Aerosol in the lower troposphere (Winter) 3.3.1 Overview of remote sensing and in-situ measurements 3.3.2 Aerosol properties from the remote sensing perspective: KARL and CALIOP 3.3.3 Aerosol microphysical properties from in-situ and remote sensing perspectives 3.4 Discussion and Conclusions 4 DEVELOPMENT OF A CIRRUS CLOUD RETRIEVAL SCHEME 4.1 Fine-scale cirrus cloud detection 4.1.1 Selection of cirrus clouds 4.1.2 Wavelet Covariance Transform method 4.1.3 Revised detection method: Dynamic Wavelet Covariance Transform 4.2 Comparison of dynamic and static cirrus detection 4.3 Cirrus cloud optical retrievals 4.3.1 Existing cirrus optical retrievals: double-ended Klett and Raman 4.3.2 Temporal averaging within stationary periods 4.3.3 Revised optical retrieval: constrained Klett method 4.4 Comparison to established optical retrievals 4.5 How uncertainties in cirrus detection affect the optical retrievals? 4.6 Discussion 4.6.1 Limitations of cirrus retrieval schemes 4.6.2 Strengths of the revised retrieval scheme 4.7 Conclusions 5 LONG-TERM ANALYSIS OF ARCTIC CIRRUS CLOUD PROPERTIES 5.1 Overview of cirrus occurrence and meteorological conditions over Ny-Ålesund 5.2 Quality assurance of optical properties 5.2.1 Specular reflection effect 5.2.2 Investigation of extreme cirrus lidar ratio values 5.2.3 Multiple-scattering correction 5.3 Overview of cirrus optical properties over Ny-Ålesund 5.4 Inter-relations of cirrus properties 5.5 Dependence on meteorological conditions 5.5.1 Cirrus clouds in the tropopause 5.6 CRE estimation at TOA: sensitivity analysis 5.7 Conclusions 6 CONCLUSIONS AND OUTLOOK A CIRRUS DETECTION SENSITIVITIES a.1 Wavelet Covariance Transform - dilation sensitivity a.2 Wavelet Covariance Transform - wavelength dependency B CIRRUS OPTICAL CHARACTERIZATION SENSITIVITIES b.1 Reference value accuracy and limitations b.2 Inherent uncertainties of constrained Klett C MULTIPLE-SCATTERING CORRECTION FOR CIRRUS CLOUDS D SEASONAL CIRRUS PROPERTIES: DESCRIPTIVE STATISTICS BIBLIOGRAPHY

Language: English

Keywords: Hochschulschrift

DOI: 10.25932/publishup-53036

URN: urn:nbn:de:kobv:517-opus4-530366

URL: https://doi.org/10.25932/publishup-53036

URL: https://nbn-resolving.org/urn:nbn:de:kobv:517-opus4-530366

URL: https://d-nb.info/1248561724/34

Author information: Rex, Markus 1966-

UID:

Format: X, 104, A-57 Seiten , Illustrationen, Diagramme

Content: 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.

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

Language: English

Keywords: Hochschulschrift

DOI: 10.25932/publishup-62424

URL: https://doi.org/10.25932/publishup-62424

Author information: Große, Guido 1976-