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  • 1
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    The Hidden Giant: How a rift pulse triggered a cascade of sector collapses and voluminous secondary mass‐transport events in the early evolution of Santorini (2022)
    Details
    Publication Date: 2022-10-01
    Description: Volcanic island sector collapses have the potential to trigger devastating tsunamis and volcanic eruptions that threaten coastal communities and infrastructure. Considered one of the most hazardous volcano‐tectonic regions in the world, the Christiana‐Santorini‐Kolumbo Volcanic Field (CSKVF) lies in the South Aegean Sea in an active rift zone. Previous studies identified an enigmatic voluminous mass‐transport deposit west and east of Santorini emplaced during the early evolution of the edifice. However, the distribution and volume as well as the nature and emplacement dynamics of this deposit remained unknown up to now. In this study, we use an extensive dataset of high‐resolution seismic profiles to unravel the distribution and internal architecture of this deposit. We show that it is located in all basins surrounding Santorini and has a bulk volume of up to 125 km3, thus representing the largest known volcanic island mass‐transport deposit in the entire Mediterranean Sea. We propose that the deposit is the result of a complex geohazard cascade that was initiated by an intensive rift pulse. This rifting event triggered a series of smaller precursory mass‐transport events before large‐scale sector collapses occurred on the northeastern flank of the extinct Christiana Volcano and on the southeastern flank of the nascent Santorini. This was followed by the emplacement of large‐scale secondary sediment failures on the slopes of Santorini, which transitioned into debris and turbidity flows that traveled far into the neighboring rift basins. Following this cascade, a distinct change in the volcanic behaviour of the CSKVF occurred, suggesting a close relationship between crustal extension, mass transport and volcanism. Cascading geohazards seem to be more common in the evolution of marine volcanic systems than previously appreciated. Wider awareness and a better understanding of cascading effects are crucial for more holistic hazard assessments.
    Description: Schematic Reconstruction of the Santorini Mass‐Transport Cascade (SMTC): After a phase of volcanic quiescence (A), a rift pulse (B) triggered precursory mass‐wasting events (C), large‐scale sector collapses (D) and secondary sediment failures (E), which culminated in a change in the volcanic behaviour of the system (F).
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:551.21
    Language: English
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    CITATION GEO-LEO
  • 2
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    A framework for ensemble modelling of climate change impacts on lakes worldwide: the ISIMIP Lake Sector (2022)
    In:  Geoscientific Model Development
    Details
    Publication Date: 2022-07-20
    Description: Empirical evidence demonstrates that lakes and reservoirs are warming across the globe. Consequently, there is an increased need to project future changes in lake thermal structure and resulting changes in lake biogeochemistry in order to plan for the likely impacts. Previous studies of the impacts of climate change on lakes have often relied on a single model forced with limited scenario-driven projections of future climate for a relatively small number of lakes. As a result, our understanding of the effects of climate change on lakes is fragmentary, based on scattered studies using different data sources and modelling protocols, and mainly focused on individual lakes or lake regions. This has precluded identification of the main impacts of climate change on lakes at global and regional scales and has likely contributed to the lack of lake water quality considerations in policy-relevant documents, such as the Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC). Here, we describe a simulation protocol developed by the Lake Sector of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) for simulating climate change impacts on lakes using an ensemble of lake models and climate change scenarios. The protocol prescribes lake simulations driven by climate forcing from gridded observations and different Earth system models under various Representative Greenhouse Gas Concentration Pathways, all consistently bias-corrected on a 0.5° × 0.5° global grid. In ISIMIP phase 2, 11 lake models were forced with these data to project the thermal structure of 62 well-studied lakes where data were available for calibration under historical conditions, and for nearly 17,500 lakes using uncalibrated models and forcing data from the global grid where lakes are present. In ISIMIP phase 3, this approach was expanded to consider more lakes, more models, and more processes. The ISIMIP Lake Sector is the largest international effort to project future water temperature, thermal structure, and ice phenology of lakes at local and global scales and paves the way for future simulations of the impacts of climate change on water quality and biogeochemistry in lakes.
    Language: English
    Type: info:eu-repo/semantics/article
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    CITATION PIK
  • 3
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    DVC and 3D stereo DIC data from analogue models exploring interaction of viscous flow and surface deformation in rotational rift systems (2022)
    GFZ Data Services
    Details
    Publication Date: 2022-08-05
    Description: Abstract
    Description: This dataset includes surface 3D stereoscopic Digital Image Correlation (3D stereo DIC) images and videos of 10 analogue models on crustal scale rifting with a rotational component. In addition, this dataset provides CT imagery of four analogue models that have been analyzed by means of Digital Volume Correlation (DVC) applied on X-Ray computed tomography volumes. Data of CT scanned models also includes slices of the volumetric displacement set for each displacement component. Using a brittle-viscous two-layer setup, the experiments focused on surface rift propagation, internal viscous flow driven by a horizontal pressure gradient and the interaction of internal and surface deformation. All experiments were performed at the Tectonic Modelling Laboratory of the University of Bern (UB). 3D stereo DIC analyses were performed at the GFZ German Research Centre for Geosciences (GFZ) and DVC analyses were performed at the Royal Holloway University London (RHUL). All models consist of a two-layer brittle-viscous set up with a total thickness of 6 cm. Thickness variations in brittle and ductile layers are expressed by the ratio RBD = brittle layer thickness/ductile layer thickness, which ranges from RBD = 0.5 to RBD = 2. The model set up lies on top of a 5 cm thick foam base with a trapezoidal shape with a height of 900 mm and a pair of bases with widths of 310 mm and 350 mm at the far ends, respectively. The foam block is sliced into segments such that 7 interlayered 0.5 cm thick plexiglass bars prevent foam collapse under the model weight. Before model construction, the foam-plexiglass assemblage is placed between longitudinal side walls. The experimental set-up is such that rotational extension in one part of the model domain is separated from rotational shortening in the other part of the model domain by a vertical rotation axis (Fig. 1). During the model run, the foam homogeneously expands in the domain undergoing extension and homogeneously contracts in the domain undergoing shortening. The applied velocity for all models is 10 mm/h and refers to the divergence of the sidewalls furthest away from the rotation axis which decreases linearly towards the rotation axis. This results in a maximum displacement of 40 mm at the outermost circular segment after a total run time of 4h.
    Keywords: multi-scale laboratories ; Digital Image Correlation (DIC) / Particle Image Velocimetry (PIV) 〉 StrainMaster (La Vision GmbH) ; analogue models of geologic processes ; continental rifting ; rotational rifting ; EPOS ; 3D stereo DIC ; software tools ; deformation 〉 rifting ; SLR camera ; Sand 〉 Quartz sand ; Surface elevation ; analogue modelling results ; analogue models of geologic processes ; property data of analogue modelling materials ; analogue modelling results ; software tools ; EARTH SCIENCE 〉 SOLID EARTH 〉 TECTONICS 〉 PLATE TECTONICS 〉 PLATE BOUNDARIES ; EARTH SCIENCE SERVICES 〉 MODELS 〉 PHYSICAL/LABORATORY MODELS
    Type: Dataset , Dataset
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    DATA GFZ
  • 4
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    Magmatic Activity and Dynamics of Melt Supply of Volcanic Centers of Ultraslow Spreading Ridges: Hints From Local Earthquake Tomography at the Knipovich Ridge (2022)
    AGU
    In:  EPIC3Geochemistry, Geophysics, Geosystems, AGU, 23(e2021G)
    Details
    Publication Date: 2022-10-24
    Description: Along ultraslow spreading ridges melt is distributed unequally, but melt focusing guides melt away from amagmatic segments toward volcanic centers. An interplay of tectonism and magmatism is thought to control melt ascent, but the detailed process of melt extraction is not yet understood. We present a detailed image of the seismic velocity structure of the Logachev volcanic center and adjacent region along the Knipovich Ridge. With travel times of P- and S-waves of 3,959 earthquakes we performed a local earthquake tomography. We simultaneously inverted for source locations, velocity structure and the Vp/Vs-ratio. An extensive low velocity anomaly coincident with high Vp/Vs-ratios 〉1.9 lies underneath the volcanic center at depths of 10 km below sea level in an aseismic area. More shallow, tightly clustered earthquake swarms connect the anomaly to a shallow anomaly with high Vp/Vs-ratio beneath the basaltic seafloor. We consider the deep low-velocity anomaly to represent an area of partial melt from which melts ascent vertically to the surface and northwards into the adjacent segment. By comparing tomographic studies of the Logachev and Southwest Indian Ridge Segment-8 volcano we conclude that volcanic centers of ultraslow spreading ridges host spatially confined, circular partial melt areas below 10 km depth, in contrast to the shallow extended melt lenses along fast spreading ridges. Lateral feeding over distances of 35 km is possible at orthogonal spreading segments, but limited at the obliquely spreading Knipovich Ridge.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
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    Global Oceans [in “State of the Climate in 2020”] (2022)
    American Meteorological Society
    Details
    Publication Date: 2022-06-09
    Description: Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 102(8), (2021): S143–S198, https://doi.org/10.1175/BAMS-D-21-0083.1.
    Description: This chapter details 2020 global patterns in select observed oceanic physical, chemical, and biological variables relative to long-term climatologies, their differences between 2020 and 2019, and puts 2020 observations in the context of the historical record. In this overview we address a few of the highlights, first in haiku, then paragraph form: La Niña arrives, shifts winds, rain, heat, salt, carbon: Pacific—beyond. Global ocean conditions in 2020 reflected a transition from an El Niño in 2018–19 to a La Niña in late 2020. Pacific trade winds strengthened in 2020 relative to 2019, driving anomalously westward Pacific equatorial surface currents. Sea surface temperatures (SSTs), upper ocean heat content, and sea surface height all fell in the eastern tropical Pacific and rose in the western tropical Pacific. Efflux of carbon dioxide from ocean to atmosphere was larger than average across much of the equatorial Pacific, and both chlorophyll-a and phytoplankton carbon concentrations were elevated across the tropical Pacific. Less rain fell and more water evaporated in the western equatorial Pacific, consonant with increased sea surface salinity (SSS) there. SSS may also have increased as a result of anomalously westward surface currents advecting salty water from the east. El Niño–Southern Oscillation conditions have global ramifications that reverberate throughout the report.
    Description: Argo data used in the chapter were collected and made freely available by the International Argo Program and the national programs that contribute to it. (https://argo.ucsd.edu, https://www.ocean-ops. org). The Argo Program is part of the Global Ocean Observing System. Many authors of the chapter are supported by NOAA Research, the NOAA Global Ocean Monitoring and Observing Program, or the NOAA Ocean Acidification Program. • L. Cheng is supported by National Natural Science Foundation of China (42076202) and Strategic Priority Research Program of the Chinese Academy of Sciences (XDB42040402. • R. E. Killick is supported by the Met Office Hadley Centre Climate Programme funded by BEIS and Defra. PMEL contribution numbers 5214, 5215, 5216, 5217, and 5247.
    Repository Name: Woods Hole Open Access Server
    Type: Book chapter
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  • 6
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    Heralds of Future Volcanism: Swarms of Microseismicity Beneath the Submarine Kolumbo Volcano Indicate Opening of Near‐Vertical Fractures Exploited by Ascending Melts (2022)
    In:  Geochemistry Geophysics Geosystems (G3)
    Details
    Publication Date: 2022-11-09
    Description: The Kolumbo submarine volcano in the southern Aegean (Greece) is associated with repeated seismic unrest since at least two decades and the causes of this unrest are poorly understood. We present a ten-month long microseismicity data set for the period 2006–2007. The majority of earthquakes cluster in a cone-shaped portion of the crust below Kolumbo. The tip of this cone coincides with a low Vp-anomaly at 2–4 km depth, which is interpreted as a crustal melt reservoir. Our data set includes several earthquake swarms, of which we analyze the four with the highest events numbers in detail. Together the swarms form a zone of fracturing elongated in the SW-NE direction, parallel to major regional faults. All four swarms show a general upward migration of hypocenters and the cracking front propagates unusually fast, compared to swarms in other volcanic areas. We conclude that the swarm seismicity is most likely triggered by a combination of pore-pressure perturbations and the re-distribution of elastic stresses. Fluid pressure perturbations are induced likely by obstructions in the melt conduits in a rheologically strong layer between 6 and 9 km depth. We conclude that the zone of fractures below Kolumbo is exploited by melts ascending from the mantle and filling the crustal melt reservoir. Together with the recurring seismic unrest, our study suggests that a future eruption is probable and monitoring of the Kolumbo volcanic system is highly advisable.
    Type: info:eu-repo/semantics/article
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  • 7
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    Co-limitation towards lower latitudes shapes global forest diversity gradients (2022)
    In:  Nature Ecology & Evolution
    Details
    Publication Date: 2022-11-18
    Description: The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers.
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  • 8
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    Investigation of Different Trench Geometries for Optimized Bedding of Buried Power Cables (2022)
    In:  Abstracts
    Details
    Publication Date: 2022-12-05
    Description: For an efficient integration of renewable energies, many transmission lines of the electrical power grid have to be extended or newly built. Besides the common overhead transmission lines, an increasing proportion of these grid expansions is conducted using underground power cables.During the operation of buried cable systems, the mechanical and thermal properties of the cable's surroundings need to meet certain requirements. To avoid insulation faults in the cables due to overheating, the ampacity is limited by specific conductor temperatures and the thermal energy resulting from the electric losses during transmission needs to be reliably dissipated. Thus, the actual performance of a buried power cable system depends strongly on the thermal properties of the cable bedding materials and soil.In practice, buried power cable lines typically require the use of cable trenches. The pre-existing soil from the cable trench is usually replaced by sand or artificial fluidized backfill materials with well-known material properties, which may differ from the properties of the surrounding soil. Thus, heterogeneous structures are created in the shallow subsurface, which affect the heat and water transport around the power cables. With an installation depth of 0.5 - 2.5 m, the cables are typically located in the vadose zone, where the thermal properties of the bedding are affected by the varying water content by up to one order of magnitude. Therefore, precise knowledge of the influence of size and geometry of the cable trench on the water distribution around the cable is crucial for an adequate assessment of the cable's ampacity ratings.Within the scope of our research, the influence of cable trench geometry and size on heat and mass transfer around buried power cables were investigated with a coupled approach of laboratory experiments and numerical modeling.
    Type: info:eu-repo/semantics/conferenceObject
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  • 9
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    Analyses of the Impact of Soil Conditions and Soil Degradation on Vegetation Vitality and Crop Productivity Based on Airborne Hyperspectral VNIR–SWIR–TIR Data in a Semi-Arid Rainfed Agricultural Area (Camarena, Central Spain) (2022)
    In:  Remote Sensing
    Details
    Publication Date: 2022-12-12
    Description: Soils are an essential factor contributing to the agricultural production of rainfed crops such as barley and triticale cereals. Changing environmental conditions and inadequate land management are endangering soil quality and productivity and, in turn, crop quality and productivity are affected. Advances in hyperspectral remote sensing are of great use for the spatial characterization and monitoring of the soil degradation status, as well as its impact on crop growth and agricultural productivity. In this study, hyperspectral airborne data covering the visible, near-infrared, short-wave infrared, and thermal infrared (VNIR–SWIR–TIR, 0.4–12 µm) were acquired in a Mediterranean agricultural area of central Spain and used to analyze the spatial differences in vegetation vitality and grain yield in relation to the soil degradation status. Specifically, leaf area index (LAI), crop water stress index (CWSI), and the biomass of the crop yield are derived from the remote sensing data and discussed regarding their spatial differences and relationship to a classification of erosion and accumulation stages (SEAS) based on previous remote sensing analyses during bare soil conditions. LAI and harvested crop biomass yield could be well estimated by PLS regression based on the hyperspectral and in situ reference data (R2 of 0.83, r of 0.91, and an RMSE of 0.2 m2 m−2 for LAI and an R2 of 0.85, r of 0.92, and an RMSE of 0.48 t ha−1 for grain yield). In addition, the soil erosion and accumulation stages (SEAS) were successfully predicted based on the canopy spectral signal of vegetated crop fields using a random forest machine learning approach. Overall accuracy was achieved above 71% by combining the VNIR–SWIR–TIR canopy reflectance and emissivity of the growing season with topographic information after reducing the redundancy in the spectral dataset. The results show that the estimated crop traits are spatially related to the soil’s degradation status, with shallow and highly eroded soils, as well as sandy accumulation zones being associated with areas of low LAI, crop yield, and high crop water stress. Overall, the results of this study illustrate the enormous potential of imaging spectroscopy for a combined analysis of the plant-soil system in the frame of land and soil degradation monitoring.
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  • 10
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    Causality guided machine learning model on wetland CH4 emissions across global wetlands (2022)
    In:  Agricultural and Forest Meteorology
    Details
    Publication Date: 2022-08-17
    Description: Wetland CH4 emissions are among the most uncertain components of the global CH4 budget. The complex nature of wetland CH4 processes makes it challenging to identify causal relationships for improving our understanding and predictability of CH4 emissions. In this study, we used the flux measurements of CH4 from eddy covariance towers (30 sites from 4 wetlands types: bog, fen, marsh, and wet tundra) to construct a causality-constrained machine learning (ML) framework to explain the regulative factors and to capture CH4 emissions at sub-seasonal scale. We found that soil temperature is the dominant factor for CH4 emissions in all studied wetland types. Ecosystem respiration (CO2) and gross primary productivity exert controls at bog, fen, and marsh sites with lagged responses of days to weeks. Integrating these asynchronous environmental and biological causal relationships in predictive models significantly improved model performance. More importantly, modeled CH4 emissions differed by up to a factor of 4 under a +1°C warming scenario when causality constraints were considered. These results highlight the significant role of causality in modeling wetland CH4 emissions especially under future warming conditions, while traditional data-driven ML models may reproduce observations for the wrong reasons. Our proposed causality-guided model could benefit predictive modeling, large-scale upscaling, data gap-filling, and surrogate modeling of wetland CH4 emissions within earth system land models.
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