Refine
Year of publication
- 2022 (157) (remove)
Document Type
- Article (125)
- Doctoral Thesis (19)
- Postprint (9)
- Monograph/Edited Volume (2)
- Part of a Book (1)
- Review (1)
Is part of the Bibliography
- yes (157)
Keywords
- climate change (6)
- permafrost (6)
- Andes (3)
- machine learning (3)
- ocean color remote sensing (3)
- radiation belts (3)
- Arctic ocean (2)
- Argentina (2)
- Central Andes (2)
- Diffusion (2)
- ERA5 (2)
- GEDI (2)
- ICESat-2 (2)
- Landsat (2)
- Magnetotellurics (2)
- Opalinus Clay (2)
- Opalinuston (2)
- PHREEQC (2)
- Precipitation (2)
- Sentinel 2 (2)
- Tibetan Plateau (2)
- Vertical flux (2)
- analysis (2)
- bacteria (2)
- bat fatalities (2)
- biodiversity decline (2)
- canopy height (2)
- diffusion (2)
- earthquake (2)
- extreme events (2)
- flood risk (2)
- floods (2)
- food web (2)
- geodynamics (2)
- green-green dilemma (2)
- hydraulic fracturing (2)
- landscape evolution (2)
- lidar (2)
- mapping (2)
- modelling (2)
- monitoring (2)
- nearshore zone (2)
- numerical modelling (2)
- numerische Modellierung (2)
- radiocarbon (2)
- reactive transport (2)
- reaktiver Transport (2)
- renewable energy (2)
- savanna (2)
- sensitivity (2)
- subduction (2)
- surface processes (2)
- suspended sediment (2)
- wind energy production (2)
- %Ro (1)
- 16S rRNA genes (1)
- 2D Numerical Modelling (1)
- ASPECT (1)
- Active tectonics (1)
- Africa (1)
- Ahr (1)
- Ahr River (1)
- Air pollution (1)
- Alexander von Humboldt (1)
- Amazon region (1)
- Analog historical seismograms (1)
- Andean back-arc; (1)
- Anden (1)
- Antarctica (1)
- Arctic (1)
- Arctic Ocean (1)
- Arctic lakes (1)
- Arctic nearhore zone (1)
- Argentinien (1)
- Asia (1)
- Assapaat landslide (1)
- B-isotopes (1)
- Baryt (1)
- Bayesian inference (1)
- Bayesian model (1)
- Beaufort Sea (1)
- Beni Suef Basin (1)
- Best management practice (1)
- Biodiversity (1)
- Blattverschiebung (1)
- Bocono (1)
- Brazil (1)
- Bruchausbreitung (1)
- Building exposure modelling (1)
- CMIP6 (1)
- CO2 emissions (1)
- COH-fluid (1)
- CRNS (1)
- Carbonation (1)
- Causality (1)
- Cenozoic flat-slab (1)
- Chain structure (1)
- Change-point regression model (1)
- Chilean Coastal Cordillera (1)
- Chilean subduction zone (1)
- Climate (1)
- Climate change (1)
- Climate governance (1)
- Cluster analysis moment (1)
- Cologne (1)
- Colorado mineral belt (1)
- Comparative hydrology (1)
- Complex terrain (1)
- Conductive channel (1)
- Continental Rifts (1)
- Coordination number (1)
- Cost-benefit (1)
- DEM analysis (1)
- DOC (1)
- Data collection (1)
- Data-Mining (1)
- Deep carbon cycle (1)
- Deformation (1)
- Deformationsmechanismen (1)
- Densification (1)
- Dissolved organic matter (DOM) (1)
- Distributed acoustic sensing (1)
- EMIC (1)
- EMIC waves (1)
- Early pleistocene; (1)
- Earthquake loss modelling (1)
- Earthquake scenario (1)
- Earthquake source observations (1)
- Earthquake swarm (1)
- Eastern Alps (1)
- Eastern Dharwar craton (1)
- Egypt (1)
- El Nino Southern Oscillation (1)
- Electrical resistivity tomography (1)
- Embedding (1)
- Endlagerung nuklearer Abfälle (1)
- Ensemble (1)
- Epistemic uncertainty (1)
- Erdbeben (1)
- Erosion (1)
- Ethiopia rift (1)
- Etna (1)
- European Alps (1)
- Evolutionary ecology (1)
- Extreme (1)
- Extreme value statistics (1)
- Extremereignisse (1)
- Extremwertstatistik (1)
- Faceted taxonomy (1)
- Fagradalsfjall (1)
- FastScape (1)
- Field measurements (1)
- Fluid inclusion geochemistry (1)
- Fluid mixing (1)
- Fluid/magma reservoir (1)
- Forearc (1)
- Formationsschaden (1)
- Fourier analysis (1)
- Functional connectivity (1)
- GNSS (1)
- Ganga River (1)
- Garnet-orthopyroxene-cordierite gneiss (1)
- Gashydrate (1)
- Gefahrenkarten (1)
- Generalized Extreme Value distribution (1)
- Genetic algorithm (1)
- Geochronology (1)
- Geodynamic Modelling (1)
- Geodynamics (1)
- Geodynamik (1)
- Geodynamische Modellierung (1)
- Geomorphic systems (1)
- Geothermie (1)
- Germany (1)
- Gewässerfernerkundung (1)
- Global inversion (1)
- Global warming (1)
- Global warming potential (1)
- Gorkha earthquake (1)
- Grabenbrüche (1)
- Granulite enclaves (1)
- Graph theory (1)
- Greek Islands (1)
- Greenhouse gas emissions (1)
- Ground-based estimates (1)
- Ground-motion model (1)
- Groundwater recharge (1)
- Grundgestein (1)
- Guaymas Basin (1)
- HBV-light model (1)
- HP-experiments (1)
- Hadley-Walker Circulation (1)
- Heteroscedastic (1)
- High pressure and high temperature; (1)
- Himalaya (1)
- Hochwasserrisiko (1)
- Homo sapiens (1)
- Horizontal (1)
- Horizontal flux (1)
- Hydrology (1)
- Hydrothermal veins (1)
- Iceland (1)
- Image processing (1)
- InSAR (1)
- India (1)
- Indian monsoon (1)
- Indian summer monsoon (1)
- Induzierte Seismizität (1)
- Injektion (1)
- Injektionsschema (1)
- Intermediate-deep earthquakes (1)
- International policy (1)
- Inverse methods (1)
- Ischigualasto-Villa Union Basin (1)
- Isotopenfraktionierung (1)
- James Ross archipelago (1)
- Joint Inversion (1)
- Kenya Rift (1)
- Kerogen petrography (1)
- L-moments estimation (1)
- LP (1)
- Lacustrine sediment (1)
- Landscapes (1)
- Landslide chronosequences (1)
- Landslides (1)
- Las Chacras-Potrerillos (1)
- Limnology (1)
- Lithosphäre (1)
- Lokalisierung von Deformation (1)
- Low impact development (1)
- Lu-Hf (1)
- Machine learning (1)
- Magma-Entgasung (1)
- Magnitude scalin (1)
- Mallik (1)
- Mediterranean (1)
- Merida Andes (1)
- Methane (1)
- Microbial processes (1)
- Micropollutants (1)
- Mikroplatte (1)
- Mikrostrukturelle (1)
- Modellierung (1)
- Modellierung der Wassertrübung (1)
- Molybdenum mineralization (1)
- Mountain meteorology (1)
- Multivariate (1)
- N-butylpyridinium bromide (1)
- NSGA-II (1)
- Nd isotopic composition (1)
- Near-source saturation (1)
- Near-surface geophysics (1)
- Neotektonik (1)
- Nepal (1)
- Nocardioides alcanivorans (1)
- Non-uniqueness (1)
- Northern Alpine Foreland Basin (1)
- Numerische 2D Modellierung (1)
- Nutrients (1)
- ODP 659 (1)
- ODP 721/722 (1)
- ODP 967 (1)
- Oberflächenprozesse (1)
- Ohre Rift (1)
- OpenStreetMap (1)
- Optimization (1)
- Ore (1)
- Orinoco River system (1)
- PM balances (1)
- PM10, PM2, PM1 (1)
- PM10, PM2.5 and PM1.0 concentrations (1)
- PSD (1)
- Palaeoclimate (1)
- Paleoseismologie (1)
- Paläoklimatologie (1)
- Particle swarm optimization (1)
- Permafrostsedimente (1)
- Phytoplankton (1)
- Plio-Pleistocene (1)
- Plio-pleistocene transition (1)
- Prediction (1)
- Probabilistic exposure modelling (1)
- RCP4,5 and 8,5 (1)
- Raman spectroscopy (1)
- Raman-Spektroskopie (1)
- Reaktivierung von Störungszonen (1)
- Recharge controls (1)
- Recurrence analysis (1)
- Respiration (1)
- Reykjanes (1)
- Rhine basin (1)
- Rift (1)
- Risstransmissivität (1)
- Russian Arctic (1)
- SIMS (1)
- Salzgestein (1)
- Sava River (1)
- Scenario (1)
- Schadensmodellierung (1)
- Schallemissionen (1)
- Scheme (1)
- Sediment characterization (1)
- Sediment reuse (1)
- Seesystemreaktionen (1)
- Seismic damage assessment (1)
- Seismic nest (1)
- Seismic noise (1)
- Seismic risk (1)
- Seismicity and tectonics (1)
- Semiarid (1)
- Sensitivity analysis (1)
- Sentinel-1 InSAR (1)
- Short-lived climate pollutants (1)
- Siberia (1)
- Sierra de San Luis (1)
- Silicate melts (1)
- Slope temperature (1)
- Sm-Nd (1)
- Soil (1)
- Sorption (1)
- South America (1)
- South China Sea (1)
- Spannungsmessung (1)
- Spatially cross-correlated ground motion (1)
- Spectral accelerations (1)
- Spectroscopy (1)
- State space reconstruction (1)
- Statistical analysis (1)
- StorAge Selection function (1)
- Storm water management model (1)
- Strain Localisation (1)
- Streamflow (1)
- Strike-slip faults (1)
- Strukturgeologie (1)
- Subduktion (1)
- Surface (1)
- TanDEM-X DEM (1)
- Tauern Window; (1)
- Thick-skinned tectonics (1)
- Time series analysis (1)
- Time-series analysis (1)
- Torsion Experiments (1)
- Torsionsexperimente (1)
- Triassic rifting (1)
- Tropical lake (1)
- Trujillo Block (1)
- Ultra-low velocity zones (1)
- Uran (1)
- VERB (1)
- VLP (1)
- VT events and tremor (1)
- Walker circulation (1)
- Wasser-Gesteins-Wechselwirkungen (1)
- Water budget / balance (1)
- Waveform inversion (1)
- Windböen (1)
- Winderosion (1)
- Wirtsgesteinsskala (1)
- Within-model uncertainty (1)
- XANES (1)
- XRD in the clay fraction (1)
- XRF analysis (1)
- Yangtze River (1)
- Yedoma (1)
- Zentral Asien (1)
- acoustic emissions (1)
- afterslip inversion (1)
- age-heterogeneity (1)
- agemodeling (1)
- air pollution (1)
- ambient noise (1)
- anaerobe Inkubationensexperimente (1)
- anaerobic incubation experiments (1)
- andean geology (1)
- apatite geochemistry and U-Pb dating (1)
- aquatic carbon cycle (1)
- arctic (1)
- arktischer Nahküstenbereich (1)
- bacterial diversity (1)
- bacterial-community structure (1)
- barite (1)
- basement rock (1)
- basin modeling (1)
- biogeography (1)
- bioturbation (1)
- black carbon (1)
- body waves (1)
- bond strength (1)
- boreal forest (1)
- buildings (1)
- burial (1)
- carbon cycle (1)
- catchment (1)
- catchment nitrate export (1)
- catchment response (1)
- change (1)
- characteristics (1)
- chemistry (1)
- chorus waves (1)
- city district (1)
- clay (1)
- cleaner energy transitions (1)
- climat change (1)
- climate adaptation (1)
- climate benefits (1)
- climate change adaptation (1)
- climate gradient (1)
- climate modeling (1)
- climate time series analysis (1)
- climate transition (1)
- computational geosciences (1)
- conflict (1)
- cosmic-rays (1)
- cosmogenic nuclides (1)
- covalency (1)
- creep and unmapped faults; (1)
- crustal structure (1)
- damage modelling (1)
- data-mining (1)
- deep biosphere (1)
- deep long-period earthquakes (1)
- deformation (1)
- degradation (1)
- density-driven flow (1)
- deposition (1)
- derived flood risk analysis (1)
- deterministic (1)
- diamond anvil cell (1)
- dichtegetriebene Strömung (1)
- digital elevation models (1)
- directivity analysis (1)
- disaster risk (1)
- discharge (1)
- discharge time series (1)
- disturbance (1)
- downscaling (1)
- drainage-divide migration (1)
- earth system sciences (1)
- earthquake damage (1)
- earthquake hydrology (1)
- earthquakes (1)
- ecosystem service cascade (1)
- electrical resistivity tomography (1)
- electrochemistry (1)
- emergency management (1)
- empirical (1)
- enhanced geothermal system (1)
- enhanced geothermal systems (EGS) (1)
- environmental (1)
- environmentalism (1)
- equifinality (1)
- erosion (1)
- eruption (1)
- estimation (1)
- event characteristics (1)
- expedition (1)
- exposure (1)
- extensional tectonics (1)
- extreme seasons (1)
- fault network (1)
- fault reactivation (1)
- faults (1)
- fields (1)
- flat-slab (1)
- flood frequency (1)
- flood hazard mapping; (1)
- flood modelling; (1)
- flood risk analysis (1)
- floodplain wetlands (1)
- fluctuation (1)
- fluvial erosion (1)
- flux (1)
- forecasting (1)
- forecasting (1922, 4315, 7924, 7964) (1)
- formation damage (1)
- fracture growth (1)
- fracture transmissivity (1)
- frequency-domain electromagnetics (1)
- gas flux (1)
- gas hydrate (1)
- gas hydrates (1)
- generative model (1)
- geochronology (1)
- geogenic degassing (1)
- geoinformatics (1)
- geomodeling (1)
- geomorphic connectivity (1)
- geostatistics (1)
- geothermal energy (1)
- geyser (1)
- grain size (1)
- greenhouse gas (1)
- ground motion fields (1)
- ground motion modeling (1)
- groundwater recharge (1)
- habitat (1)
- heat flow (1)
- heavy tail behavior (1)
- hexadecane (1)
- high spatial resolution (1)
- high-pressure (1)
- historical floods (1)
- historical geography (1)
- historische Hochwasser (1)
- hominid (1)
- horizontaler Fluss (1)
- host rock scale (1)
- human evolution (1)
- hybrid (1)
- hydrate formation (1)
- hydraulische Risserzeugung (1)
- hydraulisches Aufbrechen (1)
- hydrodynamic interactions (1)
- hydrogen bond (1)
- hydrological modeling (1)
- hydrological uplift and subsidence (1)
- hydrothermal system; (1)
- ice complex (1)
- imaging (1)
- impact (1)
- incommensurate modulation (1)
- induced seismicity (1)
- injection (1)
- injection scheme (1)
- intercultural understanding (1)
- interdisciplinarity (1)
- interseismic strain rate (1)
- inundation simulation (1)
- inverse analysis (1)
- inverse modeling (1)
- ionic liquids (1)
- iron (1)
- isotopic fractionation (1)
- knickpoints (1)
- lake system responses (1)
- larch forest (1)
- laterally constrained inversion (1)
- lethal violence (1)
- level (1)
- lithosphere (1)
- low-frequency (1)
- machine learning (0555) (1)
- magma degassing (1)
- magma plumbing system (1)
- marine sediments (1)
- maschinelles Lernen (1)
- mathematical geology (1)
- mesoscale heterogeneous catchment (1)
- metal-containing ionic liquids; (1)
- methane (1)
- methane hydrate (1)
- microbial community (1)
- microbial diversity (1)
- microbial mats (1)
- microplate (1)
- microstructural deformation mechanisms (1)
- minimum gradient support regularization (1)
- mining sciences (1)
- model (1)
- modeling; (1)
- molecular biomarkers (1)
- molekulare Biomarker (1)
- morphometric indices (1)
- mountain growth (1)
- multiperspective reception of AvH (1)
- multisensor system (1)
- multivariate statistics (1)
- muons (1)
- near-surface monitoring (1)
- neutrons (1)
- nitrogen (1)
- nitrogen legacies (1)
- normal faults (1)
- nuclear waste disposal (1)
- numerical simulation (1)
- numerical simulations (1)
- offene Daten (1)
- online (1)
- open data (1)
- organic carbon stabilization (1)
- organic matter (1)
- organisches Material (1)
- orographic rainfall (1)
- paleoceanography (1)
- paleoclimatology (1)
- paleoseismology (1)
- parameter (1)
- peat characterization (1)
- pegmatite (1)
- periglacial process (1)
- permafost (1)
- permafrost sediments (1)
- permutation entropy (1)
- petrothermales System (EGS) (1)
- phase transition (1)
- phytoplankton (1)
- planktonic foraminifera (1)
- planning indicators (1)
- plasma density (1)
- plastic degradation (1)
- plastisphere (1)
- pollen (1)
- population pressure (1)
- poroelasticity (1)
- power-law rheology (1)
- precaution (1)
- precipitation (1)
- propagating uplift (1)
- provenance (1)
- quartäre Geochronologie (1)
- radial flow (1)
- radiale Strömung (1)
- radiocarbon dating (1)
- reactive transport simulation (1)
- reaktive Transportsimulation (1)
- redox processes (1)
- reduction (1)
- regional flood frequency analysis (1)
- relaxation (1)
- remote sensing (1)
- renya Rift (1)
- reservoirs (1)
- rheology (1)
- rift (1)
- rift transfer zone (1)
- rifts (1)
- risk (1)
- risk management (1)
- river dynamics (1)
- river incision (1)
- rotational sensor (1)
- russische Arktis (1)
- salt rock (1)
- sediment (1)
- sediment dynamics (1)
- sediment routing system (1)
- sedimentary aquifer (1)
- seismic monitoring (1)
- seismic tomography (1)
- seismicity (1)
- seismicity model (1)
- sensitivity analysis (1)
- slope aspect (1)
- soil formation (1)
- soil-moisture (1)
- sorption (1)
- source rock evaluation (1)
- spin (1)
- stabile Isotope (1)
- stable carbon isotopes (1)
- stable isotopes (1)
- statistics (1)
- steric factors (1)
- stress measurement (1)
- strike-slip (1)
- subcatchment response (1)
- subduction zone (1)
- submarine gas vents (1)
- subsurface life (1)
- sulfate reduction (1)
- surface type-function-concept (1)
- surface velocity (1)
- surface wave (1)
- surface wave, inversion, near surface (1)
- tectonic geodesy (1)
- temperature sensor (1)
- tensor inversion (1)
- terrestrial (1)
- tetrahalidometallates (1)
- thaw (1)
- thermochronological modelling (AFT, AHe and ZHe) (1)
- thermochronology (1)
- thermodynamic and kinetic properties (1)
- thermodynamische und kinetische Eigenschaften (1)
- thermokarst (1)
- thermokarst lakes (1)
- thermophiles; (1)
- time series analysis (1)
- tourmaline (1)
- transition (1)
- travel time distribution (1)
- triaxial deformation experiments (1)
- triaxiale Deformationsexperimente (1)
- tropical climate (1)
- turbidity modelling (1)
- twin domains (1)
- ultra-relativistic electrons (1)
- upper tail (1)
- uranium (1)
- urban green (1)
- urban planning practice (1)
- variability (1)
- varved lake sediments (1)
- verbesserte geothermische Systeme (1)
- vertikaler Fluss (1)
- volcano-seismology (1)
- volcanoseismology (1)
- vulnerability (1)
- warfare (1)
- warvierte Seesedimente (1)
- water balance (1)
- water quality (1)
- water quality modeling (1)
- water rock interactions (1)
- water table (1)
- wetland (1)
- wetland hydrology (1)
- wind energy-biodiversity (1)
- wind energy-biodiversity conflict (1)
- wind gusts (1)
- winderosion (1)
- yedoma (1)
- yedoma ice complex (1)
- Überflutungssimulation (1)
Institute
- Institut für Geowissenschaften (157) (remove)
Ground motion with strong-velocity pulses can cause significant damage to buildings and structures at certain periods; hence, knowing the period and velocity amplitude of such pulses is critical for earthquake structural engineering.
However, the physical factors relating the scaling of pulse periods with magnitude are poorly understood.
In this study, we investigate moderate but damaging earthquakes (M-w 6-7) and characterize ground- motion pulses using the method of Shahi and Baker (2014) while considering the potential static-offset effects.
We confirm that the within-event variability of the pulses is large. The identified pulses in this study are mostly from strike-slip-like earthquakes. We further perform simulations using the freq uency-wavenumber algorithm to investigate the causes of the variability of the pulse periods within and between events for moderate strike-slip earthquakes.
We test the effect of fault dips, and the impact of the asperity locations and sizes. The simulations reveal that the asperity properties have a high impact on the pulse periods and amplitudes at nearby stations.
Our results emphasize the importance of asperity characteristics, in addition to earthquake magnitudes for the occurrence and properties of pulses produced by the forward directivity effect.
We finally quantify and discuss within- and between-event variabilities of pulse properties at short distances.
Among the multitude of geomorphological processes, aeolian shaping processes are of special character, Pedogenic dust is one of the most important sources of atmospheric aerosols and therefore regarded as a key player for atmospheric processes. Soil dust emissions, being complex in composition and properties, influence atmospheric processes and air quality and has impacts on other ecosystems. In this because even though their immediate impact can be considered low (exceptions exist), their constant and large-scale force makes them a powerful player in the earth system. dissertation, we unravel a novel scientific understanding of this complex system based on a holistic dataset acquired during a series of field experiments on arable land in La Pampa, Argentina. The field experiments as well as the generated data provide information about topography, various soil parameters, the atmospheric dynamics in the very lower atmosphere (4m height) as well as measurements regarding aeolian particle movement across a wide range of particle size classes between 0.2μm up to the coarse sand.
The investigations focus on three topics: (a) the effects of low-scale landscape structures on aeolian transport processes of the coarse particle fraction, (b) the horizontal and vertical fluxes of the very fine particles and (c) the impact of wind gusts on particle emissions.
Among other considerations presented in this thesis, it could in particular be shown, that even though the small-scale topology does have a clear impact on erosion and deposition patterns, also physical soil parameters need to be taken into account for a robust statistical modelling of the latter. Furthermore, specifically the vertical fluxes of particulate matter have different characteristics for the particle size classes. Finally, a novel statistical measure was introduced to quantify the impact of wind gusts on the particle uptake and its application on the provided data set. The aforementioned measure shows significantly increased particle concentrations during points in time defined as gust event.
With its holistic approach, this thesis further contributes to the fundamental understanding of how atmosphere and pedosphere are intertwined and affect each other.
Wetlands are dynamic ecosystems that require continuous monitoring and assessment of degradation status to design strategies for their sustainable management. While hydrology provides the primary functional control for the wetland ecosystem, the loss of landscape connectivity influences wetland degradation in a major way as it leads to fragmentation. This article aims to integrate hydrogeomorphic and ecological concepts for the assessment of degradation status and its causal factors for a large wetland in the western Ganga plains, India, the Haiderpur, using a wetlandscape approach. We have used a remote-sensing-based approach, which offers a powerful tool for assessing and linking cross-scale structures, functions, and controls in a wetlandscape. The Haiderpur, a Ramsar site since December 2021, is an artificial wetland located on the right bank of the Ganga River wherein the inflows are controlled by a barrage constructed on the Ganga River apart from smaller tributaries flowing in from the north. A novel aspect of this work is the integration of river dynamics and its connectivity to the wetlandscape to understand the spatiotemporal variability in the waterspread area in the wetland. In this work, we have developed an integrated wetlandscape assessment approach by evaluating wetland's geomorphic and hydrological connectivity status for the period 1993-2019 (25 years) across three different spatial scales - regional, catchment, and wetland. We have highlighted the ecological implications of connectivity and patch dynamics for developing sustainable wetland management plans.
Humankind and their environment need to be protected from the harmful effects of spent nuclear fuel, and therefore disposal in deep geological formations is favoured worldwide. Suitability of potential host rocks is evaluated, among others, by the retention capacity with respect to radionuclides. Safety assessments are based on the quantification of radionuclide migration lengths with numerical simulations as experiments cannot cover the required temporal (1 Ma) and spatial scales (>100 m).
Aim of the present thesis is to assess the migration of uranium, a geochemically complex radionuclide, in the potential host rock Opalinus Clay. Radionuclide migration in clay formations is governed by diffusion due to their low permeability and retarded by sorption. Both processes highly depend on pore water geochemistry and mineralogy that vary between different facies. Diffusion is quantified with the single-component (SC) approach using one diffusion coefficient for all species and the process-based multi-component (MC) option. With this, each species is assigned its own diffusion coefficient and the interaction with the diffuse double layer is taken into account. Sorption is integrated via a bottom-up approach using mechanistic surface complexation models and cation exchange. Therefore, reactive transport simulations are conducted with the geochemical code PHREEQC to quantify uranium migration, i.e. diffusion and sorption, as a function of mineralogical and geochemical heterogeneities on the host rock scale.
Sorption processes are facies dependent. Migration lengths vary between the Opalinus Clay facies by up to 10 m. Thereby, the geochemistry of the pore water, in particular the partial pressure of carbon dioxide (pCO2), is more decisive for the sorption capacity than the amount of clay minerals. Nevertheless, higher clay mineral quantities compensate geochemical variations. Consequently, sorption processes must be quantified as a function of pore water geochemistry in contact with the mineral assemblage.
Uranium diffusion in the Opalinus Clay is facies independent. Speciation is dominated by aqueous ternary complexes of U(VI) with calcium and carbonate. Differences in the migration lengths between SC and MC diffusion are with +/-5 m negligible. Further, the application of the MC approach highly depends on the quality and availability of the underlying data. Therefore, diffusion processes can be adequately quantified with the SC approach using experimentally determined diffusion coefficients.
The hydrogeological system governs pore water geochemistry within the formation rather than the mineralogy. Diffusive exchange with the adjacent aquifers established geochemical gradients over geological time scales that can enhance migration by up to 25 m. Consequently, uranium sorption processes must be quantified following the identified priority: pCO2 > hydrogeology > mineralogy.
The presented research provides a workflow and orientation for other potential disposal sites with similar pore water geochemistry due to the identified mechanisms and dependencies. With a maximum migration length of 70 m, the retention capacity of the Opalinus Clay with respect to uranium is sufficient to fulfill the German legal minimum requirement of a thickness of at least 100 m.
Groundwater is critical in supporting current and future reliable water supply throughout Africa. Although continental maps of groundwater storage and recharge have been developed, we currently lack a clear understanding on how the controls on groundwater recharge vary across the entire continent. Reviewing the existing literature, we synthesize information on reported groundwater recharge controls in Africa. We find that 15 out of 22 of these controls can be characterised using global datasets. We develop 11 descriptors of climatic, topographic, vegetation, soil and geologic properties using global datasets, to characterise groundwater recharge controls in Africa. These descriptors cluster Africa into 15 Recharge Landscape Units for which we expect recharge controls to be similar. Over 80% of the continents land area is organized by just nine of these units. We also find that aggregating the Units by similarity into four broader Recharge Landscapes (Desert, Dryland, Wet tropical and Wet tropical forest) provides a suitable level of landscape organisation to explain differences in ground-based long-term mean annual recharge and recharge ratio (annual recharge / annual precipitation) estimates. Furthermore, wetter Recharge Landscapes are more efficient in converting rainfall to recharge than drier Recharge Landscapes as well as having higher annual recharge rates. In Dryland Recharge Landscapes, we found that annual recharge rates largely varied according to mean annual precipitation, whereas recharge ratio estimates increase with increasing monthly variability in P-PET. However, we were unable to explain why ground based estimates of recharge signatures vary across other Recharge Landscapes, in which there are fewer ground based recharge estimates, using global datasets alone. Even in dryland regions, there is still considerable unexplained variability in the estimates of annual recharge and recharge ratio, stressing the limitations of global datasets for investigating ground-based information.
Statistical distributions of flood peak discharge often show heavy tail behavior, that is, extreme floods are more likely to occur than would be predicted by commonly used distributions that have exponential asymptotic behavior.
This heavy tail behavior may surprise flood managers and citizens, as human intuition tends to expect light tail behavior, and the heaviness of the tails is very difficult to predict, which may lead to unnecessarily high flood damage.
Despite its high importance, the literature on the heavy tail behavior of flood distributions is rather fragmented.
In this review, we provide a coherent overview of the processes causing heavy flood tails and the implications for science and practice.
Specifically, we propose nine hypotheses on the mechanisms causing heavy tails in flood peak distributions related to processes in the atmosphere, the catchment, and the river system.
We then discuss to which extent the current knowledge supports or contradicts these hypotheses.
We also discuss the statistical conditions for the emergence of heavy tail behavior based on derived distribution theory and relate them to the hypotheses and flood generation mechanisms.
We review the degree to which the heaviness of the tails can be predicted from process knowledge and data. Finally, we recommend further research toward testing the hypotheses and improving the prediction of heavy tails.
On 7 January 2020, an M-w 6.4 earthquake occurred in the northeastern Caribbean, a few kilometers offshore of the island of Puerto Rico. It was the mainshock of a complex seismic sequence, characterized by a large number of energetic earthquakes illuminating an east-west elongated area along the southwestern coast of Puerto Rico. Deformation fields constrained by Interferometric Synthetic Aperture Radar and Global Navigation Satellite System data indicate that the coseismic movements affected only the western part of the island. To assess the mainshock's source fault parameters, we combined the geodetically derived coseismic deformation with teleseismic waveforms using Bayesian inference. The results indicate a roughly east-west oriented fault, dipping northward and accommodating similar to 1.4 m of transtensional motion. Besides, the determined location and orientation parameters suggest an offshore continuation of the recently mapped North Boqueron Bay-Punta Montalva fault in southwest Puerto Rico. This highlights the existence of unmapped faults with moderate-to-large earthquake potential within the Puerto Rico region.
Efforts have been made in the past to enhance building exposure models on a regional scale with increasing spatial resolutions by integrating different data sources. This work follows a similar path and focuses on the downscaling of the existing SARA exposure model that was proposed for the residential building stock of the communes of Valparaiso and Vina del Mar (Chile). Although this model allowed great progress in harmonising building classes and characterising their differential physical vulnerabilities, it is now outdated, and in any case, it is spatially aggregated over large administrative units. Hence, to more accurately consider the impact of future earthquakes on these cities, it is necessary to employ more reliable exposure models. For such a purpose, we propose updating this existing model through a Bayesian approach by integrating ancillary data that has been made increasingly available from Volunteering Geo-Information (VGI) activities. Its spatial representation is also optimised in higher resolution aggregation units that avoid the inconvenience of having incomplete building-by-building footprints. A worst-case earthquake scenario is presented to calculate direct economic losses and highlight the degree of uncertainty imposed by exposure models in comparison with other parameters used to generate the seismic ground motions within a sensitivity analysis. This example study shows the great potential of using increasingly available VGI to update worldwide building exposure models as well as its importance in scenario-based seismic risk assessment.
It is widely recognized that collisional mountain belt topography is generated by crustal thickening and lowered by river bedrock erosion, linking climate and tectonics(1-4). However, whether surface processes or lithospheric strength control mountain belt height, shape and longevity remains uncertain. Additionally, how to reconcile high erosion rates in some active orogens with long-term survival of mountain belts for hundreds of millions of years remains enigmatic. Here we investigate mountain belt growth and decay using a new coupled surface process(5,6) and mantle-scale tectonic model(7). End-member models and the new non-dimensional Beaumont number, Bm, quantify how surface processes and tectonics control the topographic evolution of mountain belts, and enable the definition of three end-member types of growing orogens: type 1, non-steady state, strength controlled (Bm > 0.5); type 2, flux steady state(8), strength controlled (Bm approximate to 0.4-0.5); and type 3, flux steady state, erosion controlled (Bm < 0.4). Our results indicate that tectonics dominate in Himalaya-Tibet and the Central Andes (both type 1), efficient surface processes balance high convergence rates in Taiwan (probably type 2) and surface processes dominate in the Southern Alps of New Zealand (type 3). Orogenic decay is determined by erosional efficiency and can be subdivided into two phases with variable isostatic rebound characteristics and associated timescales. The results presented here provide a unified framework explaining how surface processes and lithospheric strength control the height, shape, and longevity of mountain belts.
Seismology, like many scientific fields, e.g., music information retrieval and speech signal pro- cessing, is experiencing exponential growth in the amount of data acquired by modern seismo- logical networks. In this thesis, I take advantage of the opportunities offered by "big data" and by the methods developed in the areas of music information retrieval and machine learning to predict better the ground motion generated by earthquakes and to study the properties of the surface layers of the Earth. In order to better predict seismic ground motions, I propose two approaches based on unsupervised deep learning methods, an autoencoder network and Generative Adversarial Networks. The autoencoder technique explores a massive amount of ground motion data, evaluates the required parameters, and generates synthetic ground motion data in the Fourier amplitude spectra (FAS) domain. This method is tested on two synthetic datasets and one real dataset. The application on the real dataset shows that the substantial information contained within the FAS data can be encoded to a four to the five-dimensional manifold. Consequently, only a few independent parameters are required for efficient ground motion prediction. I also propose a method based on Conditional Generative Adversarial Networks (CGAN) for simulating ground motion records in the time-frequency and time domains. CGAN generates the time-frequency domains based on the parameters: magnitude, distance, and shear wave velocities to 30 m depth (VS30). After generating the amplitude of the time-frequency domains using the CGAN model, instead of classical conventional methods that assume the amplitude spectra with a random phase spectrum, the phase of the time-frequency domains is recovered by minimizing the observed and reconstructed spectrograms. In the second part of this dissertation, I propose two methods for the monitoring and characterization of near-surface materials and site effect analyses. I implement an autocorrelation function and an interferometry method to monitor the velocity changes of near-surface materials resulting from the Kumamoto earthquake sequence (Japan, 2016). The observed seismic velocity changes during the strong shaking are due to the non-linear response of the near-surface materials. The results show that the velocity changes lasted for about two months after the Kumamoto mainshock. Furthermore, I used the velocity changes to evaluate the in-situ strain-stress relationship. I also propose a method for assessing the site proxy "VS30" using non-invasive analysis. In the proposed method, a dispersion curve of surface waves is inverted to estimate the shear wave velocity of the subsurface. This method is based on the Dix-like linear operators, which relate the shear wave velocity to the phase velocity. The proposed method is fast, efficient, and stable. All of the methods presented in this work can be used for processing "big data" in seismology and for the analysis of weak and strong ground motion data, to predict ground shaking, and to analyze site responses by considering potential time dependencies and nonlinearities.
The 100 km wide Merida Andes extend from the Colombian/Venezuelan border to the Coastal Cordillera. The mountain chain and its associated major strike-slip fault systems in western Venezuela formed due to oblique convergence of the Caribbean with the South American Plates and the north-eastwards expulsion of the North Andean Block. Due to the limited knowledge of lithospheric structures related to the formation of the Merida Andes research projects have been developed to illuminate this zone with deep geophysical data. In this study, we present three-dimensional inversion of broadband magnetotelluric data, collected along a 240 km long profile crossing the Merida Andes and the Maracaibo and Barinas-Apure foreland basins. The distribution of the stations limits resolution of the model to off-profile features. Combining 3D inversion of synthetic data sets derived from 3D modelling with 3D inversion of measured data, we could derive a 10 to 15 km wide corridor with good lateral resolution to develop hypotheses about the origin of deep-reaching anomalies of high electrical conductivity. The Merida Andes appear generally as electrically resistive structures, separated by anomalies associated with the most important fault systems of the region, the Bocono and Valera faults. Sensitivity tests suggest that the Valera Fault reaches to depths of up to 12 km and the Bocono Fault to more than 35 km depth. Both structures are connected to a sizeable conductor located east of the profile at 12-15 km depth. We propose that the high conductivity associated with this off-profile conductor may be related to the detachment of the Trujillo Block. We also identified a conductive zone that correlates spatially with the location of a gravity low, possibly representing a SE tilt of the Maracaibo Triangular Block under the mountain chain to great depths (>30 km). The relevance of these tectonic blocks in our models at crustal depths seems to be consistent with proposed theories that describe the geodynamics of western Venezuela as dominated by floating blocks or orogens. Our results stress the importance of the Trujillo Block for the current tectonic evolution of western Venezuela and confirm the relevance of the Bocono Fault carrying deformation to the lower crust and upper mantle. The Barinas-Apure and the Maracaibo sedimentary basins are imaged as electrically conductive with depths of 4 to 5 km and 5 to 10 km, respectively. The Barinas-Apure basin is imaged as a simple 1D structure, in contrast to the Maracaibo Basin, where a series of conductive and resistive bodies could be related to active deformation causing the juxtaposition of older geological formations and younger basin sediments.
The Andes are a ~7000 km long N-S trending mountain range developed along the South American western continental margin. Driven by the subduction of the oceanic Nazca plate beneath the continental South American plate, the formation of the northern and central parts of the orogen is a type case for a non-collisional orogeny. In the southern Central Andes (SCA, 29°S-39°S), the oceanic plate changes the subduction angle between 33°S and 35°S from almost horizontal (< 5° dip) in the north to a steeper angle (~30° dip) in the south. This sector of the Andes also displays remarkable along- and across- strike variations of the tectonic deformation patterns. These include a systematic decrease of topographic elevation, of crustal shortening and foreland and orogenic width, as well as an alternation of the foreland deformation style between thick-skinned and thin-skinned recorded along- and across the strike of the subduction zone. Moreover, the SCA are a very seismically active region. The continental plate is characterized by a relatively shallow seismicity (< 30 km depth) which is mainly focussed at the transition from the orogen to the lowland areas of the foreland and the forearc; in contrast, deeper seismicity occurs below the interiors of the northern foreland. Additionally, frequent seismicity is also recorded in the shallow parts of the oceanic plate and in a sector of the flat slab segment between 31°S and 33°S. The observed spatial heterogeneity in tectonic and seismic deformation in the SCA has been attributed to multiple causes, including variations in sediment thickness, the presence of inherited structures and changes in the subduction angle of the oceanic slab. However, there is no study that inquired the relationship between the long-term rheological configuration of the SCA and the spatial deformation patterns. Moreover, the effects of the density and thickness configuration of the continental plate and of variations in the slab dip angle in the rheological state of the lithosphere have been not thoroughly investigated yet. Since rheology depends on composition, pressure and temperature, a detailed characterization of the compositional, structural and thermal fields of the lithosphere is needed. Therefore, by using multiple geophysical approaches and data sources, I constructed the following 3D models of the SCA lithosphere: (i) a seismically-constrained structural and density model that was tested against the gravity field; (ii) a thermal model integrating the conversion of mantle shear-wave velocities to temperature with steady-state conductive calculations in the uppermost lithosphere (< 50 km depth), validated by temperature and heat-flow measurements; and (iii) a rheological model of the long-term lithospheric strength using as input the previously-generated models.
The results of this dissertation indicate that the present-day thermal and rheological fields of the SCA are controlled by different mechanisms at different depths. At shallow depths (< 50 km), the thermomechanical field is modulated by the heterogeneous composition of the continental lithosphere. The overprint of the oceanic slab is detectable where the oceanic plate is shallow (< 85 km depth) and the radiogenic crust is thin, resulting in overall lower temperatures and higher strength compared to regions where the slab is steep and the radiogenic crust is thick. At depths > 50 km, largest temperatures variations occur where the descending slab is detected, which implies that the deep thermal field is mainly affected by the slab dip geometry.
The outcomes of this thesis suggests that long-term thermomechanical state of the lithosphere influences the spatial distribution of seismic deformation. Most of the seismicity within the continental plate occurs above the modelled transition from brittle to ductile conditions. Additionally, there is a spatial correlation between the location of these events and the transition from the mechanically strong domains of the forearc and foreland to the weak domain of the orogen. In contrast, seismicity within the oceanic plate is also detected where long-term ductile conditions are expected. I therefore analysed the possible influence of additional mechanisms triggering these earthquakes, including the compaction of sediments in the subduction interface and dehydration reactions in the slab. To that aim, I carried out a qualitative analysis of the state of hydration in the mantle using the ratio between compressional- and shear-wave velocity (vp/vs ratio) from a previous seismic tomography. The results from this analysis indicate that the majority of the seismicity spatially correlates with hydrated areas of the slab and overlying continental mantle, with the exception of the cluster within the flat slab segment. In this region, earthquakes are likely triggered by flexural processes where the slab changes from a flat to a steep subduction angle.
First-order variations in the observed tectonic patterns also seem to be influenced by the thermomechanical configuration of the lithosphere. The mechanically strong domains of the forearc and foreland, due to their resistance to deformation, display smaller amounts of shortening than the relatively weak orogenic domain. In addition, the structural and thermomechanical characteristics modelled in this dissertation confirm previous analyses from geodynamic models pointing to the control of the observed heterogeneities in the orogen and foreland deformation style. These characteristics include the lithospheric and crustal thickness, the presence of weak sediments and the variations in gravitational potential energy.
Specific conditions occur in the cold and strong northern foreland, which is characterized by active seismicity and thick-skinned structures, although the modelled crustal strength exceeds the typical values of externally-applied tectonic stresses. The additional mechanisms that could explain the strain localization in a region that should resist deformation are: (i) increased tectonic forces coming from the steepening of the slab and (ii) enhanced weakening along inherited structures from pre-Andean deformation events. Finally, the thermomechanical conditions of this sector of the foreland could be a key factor influencing the preservation of the flat subduction angle at these latitudes of the SCA.
The stabilizing properties of mineral-organic carbon (OC) interactions have been studied in many soil environments (temperate soils, podzol lateritic soils, and paddy soils). Recently, interest in their role in permafrost regions is increasing as permafrost was identified as a hotspot of change. In thawing ice-rich permafrost regions, such as the Yedoma domain, 327-466 Gt of frozen OC is buried in deep sediments. Interactions between minerals and OC are important because OC is located very near the mineral matrix. Mineral surfaces and elements could mitigate recent and future greenhouse gas emissions through physical and/or physicochemical protection of OC. The dynamic changes in redox and pH conditions associated with thermokarst lake formation and drainage trigger metal-oxide dissolution and precipitation, likely influencing OC stabilization and microbial mineralization. However, the influence of thermokarst processes on mineral-OC interactions remains poorly constrained. In this study, we aim to characterize Fe, Mn, Al, and Ca minerals and their potential protective role for OC. Total and selective extractions were used to assess the crystalline and amorphous oxides or complexed metal pools as well as the organic acids found within these pools. We analyzed four sediment cores from an ice-rich permafrost area in Central Yakutia, which were drilled (i) in undisturbed Yedoma uplands, (ii) beneath a recent lake formed within Yedoma deposits, (iii) in a drained thermokarst lake basin, and (iv) beneath a mature thermokarst lake from the early Holocene period. We find a decrease in the amount of reactive Fe, Mn, Al, and Ca in the deposits on lake formation (promoting reduction reactions), and this was largely balanced by an increase in the amount of reactive metals in the deposits on lake drainage (promoting oxidation reactions). We demonstrate an increase in the metal to C molar ratio on thermokarst process, which may indicate an increase in metal-C bindings and could provide a higher protective role against microbial mineralization of organic matter. Finally, we find that an increase in mineral-OC interactions corresponded to a decrease in CO2 and CH4 gas emissions on thermokarst process. Mineral-OC interactions could mitigate greenhouse gas production from permafrost thaw as soon as lake drainage occurs.
Boreal forests cover over half of the global permafrost area and protect underlying permafrost. Boreal forest development, therefore, has an impact on permafrost evolution, especially under a warming climate.
Forest disturbances and changing climate conditions cause vegetation shifts and potentially destabilize the carbon stored within the vegetation and permafrost. Disturbed permafrost-forest ecosystems can develop into a dry or swampy bush- or grasslands, shift toward broadleaf- or evergreen needleleaf-dominated forests, or recover to the pre-disturbance state.
An increase in the number and intensity of fires, as well as intensified logging activities, could lead to a partial or complete ecosystem and permafrost degradation. We study the impact of forest disturbances (logging, surface, and canopy fires) on the thermal and hydrological permafrost conditions and ecosystem resilience.
We use a dynamic multilayer canopy-permafrost model to simulate different scenarios at a study site in eastern Siberia. We implement expected mortality, defoliation, and ground surface changes and analyze the interplay between forest recovery and permafrost. We find that forest loss induces soil drying of up to 44%, leading to lower active layer thicknesses and abrupt or steady decline of a larch forest, depending on disturbance intensity.
Only after surface fires, the most common disturbances, inducing low mortality rates, forests can recover and overpass pre-disturbance leaf area index values. We find that the trajectory of larch forests after surface fires is dependent on the precipitation conditions in the years after the disturbance. Dryer years can drastically change the direction of the larch forest development within the studied period.
Reconstructing thermal histories in thrust belts is commonly used to infer the age and rates of thrusting and hence the driving mechanisms of orogenesis.
In areas where ancient basins have been incorporated into the orogenic wedge, a quantitative reconstruction of the thermal history helps distinguish among potential mechanisms responsible for heating events.
We present such a reconstruction for the Ischigualasto-Villa Union basin in the western Pampean Ranges of Argentina, where Triassic rifting and late Cretaceous-Cenozoic retroarc foreland basin development has been widely documented, including Miocene flat-slab subduction.
We report results of organic and inorganic thermal indicators acquired along three stratigraphic sections, including vitrinite reflectance and X-ray diffractometry in claystones and new thermochronological [(apatite fission-track and apatite and zircon [U-Th]/He)] analyses.
Despite up to 5 km-thick Cenozoic overburden and unlike previously thought, the thermal peak in the basin is not due to Cenozoic burial but occurred in the Triassic, associated with a high heat flow of up to 90 mWm(-2) and <2 km of burial, which heated the base of the Triassic strata to similar to 160 degrees C. Following exhumation, attested by the development of an unconformity between the Triassic and Late-Cretaceous-Cenozoic sequences, Cenozoic re-burial increased the temperature to similar to 110 degrees C at the base of the Triassic section and only similar to 50 degrees C 7 km upsection, suggesting a dramatic decrease in the thermal gradient.
The onset of Cenozoic cooling occurred at similar to 10(-8) Ma, concomitant with sediment accumulation and thus preceding the latest Miocene onset of thrusting that has been independently documented by stratigraphic-cross-cutting relationships.
We argue that the onset of cooling is associated with lithospheric refrigeration following establishment of flat-slab subduction, leading to the eastward displacement of the asthenospheric wedge beneath the South American plate.
Our study places time and temperature constraints on flat-slab cooling that calls for a careful interpretation of exhumation signals in thrustbelts inferred from thermochronology only.
The spatial pattern of extreme precipitation from 40 years of gauge data in the central Himalaya
(2022)
The topography of the Himalaya exerts a substantial control on the spatial distribution of monsoonal rainfall, which is a vital water source for the regional economy and population. But the occurrence of short-lived and high-intensity precipitation results in socio-economic losses. This study relies on 40 years of daily data from 204 ground stations in Nepal to derive extreme precipitation thresholds, amounts, and days at the 95th percentile. We additionally determine the precipitation magnitude-frequency relation. We observe that extreme precipitation amounts follow an almost uniform band parallel to topographic contour lines in the southern Himalaya mountains in central and eastern Nepal but not in western Nepal. The relationship of extreme precipitation indices with topographic relief shows that extreme precipitation thresholds decrease with increasing elevation, but extreme precipitation days increase in higher elevation areas. Furthermore, stations above 1 km elevation exhibit a power-law relation in the rainfall magnitude-frequency framework. Stations at higher elevations generally have lower values of power-law exponents than low elevation areas. This suggests a fundamentally different behaviour of the rainfall distribution and an increased occurrence of extreme rainfall storms in the high elevation areas of Nepal.
Agricultural production worldwide has been increasing in the last decades at a very fast pace and with it the waste generation. Livestock activities are one of the largest producers of residues in the agricultural sector and contribute greatly to climate change. The present chapter gives an introduction and an in-depth analysis of the waste management of livestock for the conversion in a circular agriculture and economy based on research and experience in the sector conducted in the last decades. The conversion of animal waste into energy generation is an opportunity for farmers to obtain additional economic benefits, while contributing to the environment by preventing the release of GHGs into the atmosphere. The use of animal waste for energy generation through anaerobic digestion is a progressive technique and is being widely accepted in Europe, where Germany is the leading country in the use of biogas plants for energy production among others in the European Union. Economically speaking, the livestock industry faces the challenge of converting its production into a clean and more profitable production. The goal of this chapter is to analyze the economic benefit as well as the environmental contribution and future challenges of the use of livestock waste in the biorefineries sector from different perspectives, based on an intensive literature review. This review is accompanied by a geospatial analysis component, mapping biogas reactor hotspots and clusters in Germany, by means of methods of spatial statistics as analysis methods as kernel density estimations (KDE) and K-means clustering, based on volunteer geographic data. The applied methods easily can be transferred to other regions and allow a quick macroscopic overview over existing biogas reactors; furthermore, an identification of cluster and hotspots with a high biogas potential, that in a subsequent step can be analyzed in depth in larger scales.
The Walker Circulation (WC) is an east-west trending band of atmospheric circulation cells along the equator and the predominant controller of heat and moisture transport in the tropics. Its variability is closely linked to the sea-surface temperature (SST) changes across the Pacific, the Indian and the Atlantic Oceans and can have pronounced effects on the humidity regimes of the adjacent continents. In recent years, the evolution of the WC during the Plioand Pleistocene epochs has been intensely studied in the context of the effectiveness of the tropics in modulating global climate change (e.g., the intensification of Northern Hemisphere glaciation). However, the onset of the modern WC pattern as well as its global impact during the Plioand Pleistocene is controversially assessed in the literature. For its onset, previous studies have suggested dates ranging between 2.4 and 0.8 million years ago (Myr), while its argued impact ranges from crucially influencing the increase of Northern Hemisphere ice sheet growth by channelling heat and moisture from the tropics into the high latitudes to having no effect on global ice volume changes. In order to achieve a comprehensive understanding of the spatiotemporal evolution of the WC during this time frame, we statistically analysed 30 globally distributed SST records covering the low and high latitudes between 3.5 and 1.5 Myr, encompassing the Late Pliocene to Early Pleistocene. We utilized a statistical change-point regression model to determine significant change points in the SST evolution of the (sub)-tropics and high latitudes that potentially relate to changes in the WC. We find that the WC experienced a multifaceted evolution between the Late Pliocene and the Early Pleistocene with significant transitional steps at-2.7 and-2.1 Ma. Our results suggest after the Late Pliocene, a pre-modern WC set in, which was characterized by a progressively strengthened Pacific Walker Cell alongside a weakened Indian Ocean Walker Cell. This change was potentially triggered by the constriction of the Indonesian seaway, an important transmitter between the Pacific and Indian Ocean. The ensuing mode of the WC intensified until-2.1 Myr, when SST values around the global scale signalled a progressive strengthening of the Indian Walker Cell in phase with the progressive strengthening of the Pacific and Atlantic Cells. Our findings indicate that a shift from a pre-modern to a modern-like WC potentially only occurred during the mid-Pleistocene.
We produce climate projections through the 21st century using the fractional energy balance equation (FEBE): a generalization of the standard energy balance equation (EBE). The FEBE can be derived from Budyko-Sellers models or phenomenologically through the application of the scaling symmetry to energy storage processes, easily implemented by changing the integer order of the storage (derivative) term in the EBE to a fractional value.
The FEBE is defined by three parameters: a fundamental shape parameter, a timescale and an amplitude, corresponding to, respectively, the scaling exponent h, the relaxation time tau and the equilibrium climate sensitivity (ECS). Two additional parameters were needed for the forcing: an aerosol recalibration factor alpha to account for the large aerosol uncertainty and a volcanic intermittency correction exponent upsilon. A Bayesian framework based on historical temperatures and natural and anthropogenic forcing series was used for parameter estimation. Significantly, the error model was not ad hoc but rather predicted by the model itself: the internal variability response to white noise internal forcing.
The 90 % credible interval (CI) of the exponent and relaxation time were h = [0.33, 0.44] (median = 0.38) and tau = [2.4, 7.0] (median = 4.7) years compared to the usual EBE h = 1, and literature values of tau typically in the range 2-8 years. Aerosol forcings were too strong, requiring a decrease by an average factor alpha = [0.2, 1.0] (median = 0.6); the volcanic intermittency correction exponent was upsilon = [0.15, 0.41] (median = 0.28) compared to standard values alpha = upsilon = 1. The overpowered aerosols support a revision of the global modern (2005) aerosol forcing 90 % CI to a narrower range [ -1.0, -0.2] W m(-2). The key parameter ECS in comparison to IPCC AR5 (and to the CMIP6 MME), the 90 % CI range is reduced from [1.5, 4.5] K ([2.0, 5.5] K) to [1.6, 2.4] K ([1.5, 2.2] K), with median value lowered from 3.0 K (3.7 K) to 2.0 K (1.8 K) Similarly we found for the transient climate response (TCR), the 90 % CI range shrinks from [1.0, 2.5] K ([1.2, 2.8] K) to [1.2, 1.8] K ([1.1, 1.6] K) and the median estimate decreases from 1.8 K (2.0 K) to 1.5 K (1.4 K). As often seen in other observational-based studies, the FEBE values for climate sensitivities are therefore somewhat lower but still consistent with those in IPCC AR5 and the CMIP6 MME. <br /> Using these parameters, we made projections to 2100 using both the Representative Concentration Pathway (RCP) and Shared Socioeconomic Pathway (SSP) scenarios, and compared them to the corresponding CMIP5 and CMIP6 multi-model ensembles (MMEs). The FEBE historical reconstructions (1880-2020) closely follow observations, notably during the 1998-2014 slowdown ("hiatus"). We also reproduce the internal variability with the FEBE and statistically validate this against centennial-scale temperature observations. Overall, the FEBE projections were 10 %-15 % lower but due to their smaller uncertainties, their 90 % CIs lie completely within the GCM 90 % CIs. This agreement means that the FEBE validates the MME, and vice versa.
The effect of lithology on the relationship between denudation rate and chemical weathering pathways
(2022)
The denudation of rocks in mountain belts exposes a range of fresh minerals to the surface of the Earth that are chemically weathered by acidic and oxygenated fluids. The impact of the resulting coupling between denudation and weathering rates fundamentally depends on the types of minerals that are weathering. Whereas silicate weathering sequesters CO2, the combination of sulfide oxidation and carbonate dissolution emits CO2 to the atmosphere. Here, we combine the concentrations of dissolved major elements in stream waters with Be-10 basin-wide denudation rates from 35 small catchments in eastern Tibet to elucidate the importance of lithology in modulating the relationships between denudation rate, chemical weathering pathways, and CO2 consumption or release. Our catchments span 3 orders of magnitude in denudation rate in low-grade flysch, high-grade metapelites, and granitoid rocks. For each stream, we estimate the concentrations of solutes sourced from silicate weathering, carbonate dissolution, and sulfide oxidation using a mixing model. We find that for all lithologies, cation concentrations from silicate weathering are largely independent of denudation rate, but solute concentrations from carbonates and, where present, sulfides increase with increasing denudation rate. With increasing denudation rates, weathering may therefore shift from consuming to releasing CO2 in both (meta)sedimentary and granitoid lithologies. For a given denudation rate, we report dissolved solid concentrations and inferred weathering fluxes in catchments underlain by (meta)sedimentary rock that are 2-10 times higher compared to catchments containing granitoid lithologies, even though climatic and topographic parameters do not vary systematically between these catchments. Thus, varying proportions of exposed (meta)sedimentary and igneous rocks during orogenesis could lead to changes in the sequestration and release of CO2 that are independent of denudation rate.