bluuebunny/crossref_metadata_2025 huggingface dataset:
Comprehensive analysis of the response of the ionospheric F2-layer to the largest geomagnetic storms from solar cycle #24 over Europe
Authors: Berényi Kitti Alexandra , Kis Árpád , Heilig Balázs , Urbář Jaroslav , Barta Veronika
Published: March 2022

The complex analysis of the largest geomagnetic storms of solar cycle #24 maximum is our main aim in this study. Our focus is on the ionosphere, more precisely on the ionospheric F2-layer. The selected storm intervals are: 11-17 November 2012 (Kpmax=6.33, Dstmin=-108 nT ), 16-23 March 2013 (Kpmax= 6.67, Dstmin=-132 nT ),  and 16-25 March 2015 (Kpmax=7.67, Dstmin=-228 nT). Data from 6 digisonde (DPS4D) stations, ground GNSS TEC and Swarm satellite constellation have been used for the investigation.

This study is the next step to validate our previous results discussed in Berényi et al. (2018). We analyse the meridional behaviour of the geomagnetic disturbance caused ionospheric storms to understand and interpret the evolution of the caused effects.

The storm from 2012 is a no-positive phase (NPP) storm, but the 2013 and 2015 storms show the pattern of the regular positive phase (RPP) storm type (after the categorization by Mendillo and Narvaez, 2010). In all three cases a significant increase in electron density of the F2-layer can be observed at dawn/early morning (around 6:00 UT, 07:00 LT).  We compared also the digisonde foF2 parameter with the GNSS TEC data. Besides, we observed the fade-out of the ionospheric layers at night during the geomagnetically disturbed time periods of storm 2012 and 2015. In order to determine whether this fade-out is connected to the L-shell location of the plasmapause we analysed the Swarm observations (for the storm 2015), too.

Berényi, K. A., Barta, V., & Kis. (2018). Midlatitude ionospheric F2-layer response to eruptive solar events-caused geomagnetic disturbances over Hungary during the maximum of the solar cycle 24: A case study. Advances in Space Research, 61(5), 1230–1243. https://doi.org/10.1016/j.asr.2017.12.021

Mendillo, M., & Narvaez, C. (2010). Ionospheric storms at geophysically-equivalent sites - Part 2: Local time storm patterns for sub-auroral ionospheres. Annales Geophysicae, 28(7), 1449–1462. https://doi.org/10.5194/angeo-28-1449-2010
Correcting UAV derived winter snow depth on glaciers by modelling the evolution of the No-Snow glacier surface 
Authors: Hynek Bernhard , Neureiter Anton , Weyss Gernot , Ludewig Elke , Schöner Wolfgang
Published: March 2022

Spatially distributed winter snow accumulation over glaciers is an important information for a lot of purposes. Typically, snow depth on glaciers is measured by manual snow probing or ground penetrating radar. The point measurements of snow depth and snow density are then used to calculate the winter mass balance of the glacier.

In the last decade remote sensing techniques such as LIDAR and structure from motion (sfm) photogrammetry in combination with unmanned aerial vehicles (UAVs) have become more frequent to reconstruct snow surfaces providing a better spatial coverage and spatial resolution. Snow depth is calculated by DEM differencing of a No-Snow surface (summer surface) and the snow surface (winter surface).

However, using DEM differencing to extract snow depth over glaciers introduces the problem, that the No-Snow surface is not constant, as (1) the glacier is moving between the survey dates and (2) the surface possibly undergoes surface lowering due to melt after the summer survey.

In this study we present measurements on two small mass balance glaciers in the Austrian Alps (Goldbergkees and Kleinfleißkees). We account for the evolution of the No-Snow surface by (1) applying a simple model of the vertical ice movement and by (2) calculating the surface lowering due to melt using a distributed mass balance model.  The effect of both corrections is then validated using a dense network of manual snow depth measurements across the glacier.
Risk perception, regulation, community engagement and acceptance: Navigating the legal and social UK geothermal landscape 
Authors: Ryder Stacia , Rohse Mel , Abesser Corinna
Published: March 2022

Deep geothermal energy is regarded as an important renewable source of power and heat that has the potential to occupy a central place in a just energy transition as part of the UK’s strategy to meet its Net Zero Commitment.  Access to deep geothermal energy bears some similar risks to shale gas development, a practice met in the UK with much public concern and controversy. Existing research on shale gas has established that risk perceptions, notably around induced seismicity, were of particular importance to the public and in local communities where exploration was proposed. Furthermore, the UK government’s approach to regulating induced seismicity across these two industries has not been uniform. It thus remains unclear how the exploitation of geothermal energy will be received more broadly, and how the government might regulate geothermal activity . 

The exploration and exploitation of geothermal energy is intrinsically technical, yet geothermal developments also include social, spatial and political aspects that have so far been neglected in geothermal energy research. As such, in this paper we draw on multiple data sets, including interviews with government, industry and public stakeholders to compare and contrast governance approaches and public risk perceptions tied to shale gas and geothermal energy production in the UK. We suggest some key differences between the shale and geothermal energy industries in terms of technologies, social acceptance and implications for climate change. Yet we also point to divergent issues, in terms of a lack of a cohesive regulatory framework or guidance for community engagement tied to geothermal energy, and how this might negatively impact public perceptions of the practice, thwarting social acceptance. In closing, we make recommendations for establishing more systematic geothermal regulations and policies aimed at creating consistent, environmentally sustainable and socially just practices in the industry moving forward. 
Lower magnitude volcanic eruptions as Global Catastrophic Risks
Authors: Mani Lara , Tzachor Asaf , Cole Paul
Published: March 2022

Large-magnitude volcanic eruptions have long been considered to pose a threat to the continued flourishing of humanity. The dominant narrative focuses on the nuclear-winter climatic scenarios that may develop as a result of a large-magnitude eruption (magnitudes 7+ on the Volcanic Explosivity Index (VEI)) propelling large quantities of ash and gas into our upper atmosphere and devastating global crop production. However, the probability of such an event remains rare, and this narrative fails to fully consider the vulnerability component of the risk equation. We propose that volcanic eruptions of even moderate magnitudes (VEI 3-6) could constitute a global catastrophic risk (events that might inflict damage to human welfare on a global scale) where the impacts of the eruption are amplified through cascading critical system failures.

Increased globalisation in our modern world has resulted in our overreliance on global critical system – networks and supply chains vital to the support and continued development of our societies (e.g. submarine cables, global shipping routes, transport and trade networks). We observe that many of these critical infrastructures and networks converge in regions where they could be exposed to moderate-scale volcanic eruptions (VEI 3-6). These regions of intersection, or pinch points, present localities where we have prioritised efficiency over resilience, and manufactured a new GCR landscape, presenting a scenario for global risk propagation. We present seven global pinch points, including the Strait of Malacca and the Mediterranean, which represent localities where disruption to any of these systems can result in a cascade of global disruptions. This is exemplified by the 2010 Eyjafjallajökull VEI 4 eruption which resulted in the closure of European airspace and cascaded to cause global disruption to just-in-time supply chains and transportation networks.

We suggest that volcanic risk assessments should incorporate interdisciplinary systems thinking in order to increase our resilience to volcanic GCRs.
Deep learning approaches to study floods through river cameras
Authors: Vandaele Remy , Dance Sarah L , Ojha Varun
Published: March 2022

The monitoring of river water-levels is essential to study floods and mitigate their risks. However, it is difficult to obtain accurate measurements of river water-levels: indeed, the river gauges commonly used to measure these levels can be overwhelmed during flood events, and their number is declining globally [1,2]. This means that the monitoring and study of floods relying on gauge station measurements can only be based on sparse and possibly inaccurate river water-level data distributed unevenly along the rivers, sometimes several kilometres away from the location of interest.

We investigate if deep learning can be used to monitor river water-levels in a more flexible and efficient way. More specifically, we apply two deep learning approaches on river cameras, which are CCTV cameras commonly used to monitor the surroundings of rivers and could be easily installed at new locations. The first approach [3,4] relies on transfer learning to train water segmentation networks able to find the water pixels within the camera images and use the number of water pixels within (regions of) the images to monitor the relative evolution of the river water-level. The second approach is based on the creation of a large dataset of 32,715 images annotated with distant gauge water-level data in order to accurately train networks able to produce river water-level indexes independent from the field of view of the cameras. 

We show that both approaches can be used as sources of river water-level data. The first approach is able to produce river water-level indexes highly correlated with ground truth river water-levels (Pearson correlation coefficient >0.94). While the second approach is less accurate (Pearson correlation coefficients between 0.8 and 0.94), it is able to produce calibrated indexes independent from the field of view of the camera. 

 

[1] Mishra, A. K., and Coulibaly, P. (2009), Developments in hydrometric network design: A review, Rev. Geophys., 47, RG2001, doi:10.1029/2007RG000243.

[2] Global Runoff Data Center (2016).  Global runoff data base, temporal distribution of available discharge data.  https://www.bafg.de/SharedDocs/Bilder/Bilder_GRDC/grdcStations_tornadoChart.jpg. Last visited:2021-04-26.

[3] Vandaele, R., Dance, S. L., & Ojha, V. (2020, September). Automated water segmentation and river level detection on camera images using transfer learning. In DAGM German Conference on Pattern Recognition (pp. 232-245). Springer, Cham.

[4] Vandaele, R., Dance, S. L., & Ojha, V. (2021). Deep learning for automated river-level monitoring through river camera images: an approach based on water segmentation and transfer learning. Hydrology and Earth System Sciences, 25(8), 4435-4453.
Early-Miocene stable isotope paleoaltimetry estimates for the Central Alps
Authors: Ballian Armelle , Meijers Maud J. M. , Cojan Isabelle , Huyghe Damien , Fiebig Jens , Mulch Andreas
Published: March 2022

Quantifying surface elevation over geological time is essential for reconstructing coupled climatic and mountain building processes. Surface uplift of an orogen, such as the European Alps, results from the interplay between subsurface geodynamic processes and climate-induced denudation. Although being one of the most studied mountain ranges worldwide, knowledge about the elevation history of the European Alps is still scarce. Stable isotope paleoaltimetry is a robust tool to reconstruct paleoelevations of orogens. The method is based on the systematic inverse relationship of isotope ratios of oxygen (δ18O) and hydrogen (δD) in precipitation with elevation. Recent stable isotope paleoaltimetry studies that focused on the Central Alps indicate elevations locally exceeding 4 km during the Mid-Miocene. Here, we reconstruct past Alpine surface elevations by applying stable isotope paleoaltimetry coupled with clumped isotope, T(Δ47), temperature reconstructions in Miocene paleosols of the Alpine foreland basins. Knowledge of low-elevation (near sea level) temperature conditions allows to refine low-elevation, near sea level estimates for δ18O in precipitation. Contrasting these low-elevation isotope in precipitation values with age equivalent records from high elevation counterparts hence permits calculation of surface elevation differences between the foreland basin and the orogen interior. With a spatio-temporally enhanced coverage of the European Alps, we present a long-term terrestrial climate record covering the time interval between ca. 23 and 14 Ma including sites in the Western and Central Alps. Pedogenic carbonate nodules from paleosols of the Digne-Valensole basin (Western Alps, France) indicate relatively warm and stable temperatures (ca. 26°C) for the early Miocene (23-20 Ma) followed by enhanced temperature variability with maximum values of 34°C at ca. 16.5 Ma. By contrasting temperature-corrected foreland basin pedogenic carbonate δ18O values from the Digne-Valensole Basin with δD values of dated, clay-bearing fault gouge from the Periadriatic Fault in Val Morobbia (Switzerland), we conclude that the stable isotope paleoaltimetry data permit peak elevations of 4-5 km in the Central Alps during the earliest Miocene (ca. 23 Ma).

References

Krsnik et al., 2021: SED, doi: 10.5194/se-2021-59

Zwingmann & Mancktelow, 2004: EPSL, doi: 10.1016/j.epsl.2004.04.041
Ca and Sr in the technozem of various ore deposits of Eastern Transbaikalia
Authors: Uliana Guliaeva , Tatyana Kuzmina , Vadim Ermakov
Published: March 2022

In the Urov sub-region of the biosphere (Eastern Transbaikalia), a local increased content of Sr in soils and plants was found due to high concentrations of Sr in soil-forming rocks (carbonated granites). The purpose of this study is to assess the concentrations of Ca and Sr in the technozem of dumps and quarries of seven developed deposits (W-Mo, Mo-Cu, Pb-Zn, Au). The fraction of technozem (< 1 mm) was ground to a grain size of 150-200 mesh and analyzed by XRF. The content of Ca and Sr in plant mowing was determined by the flame variant of AAS. It was found that the content of Ca and Sr in 25 samples of technozem varied between 4970-37200 mg/kg (Ca) and 100-620 mg/kg (Sr). The average content of Sr is 308 ± 122 mg/kg. The increased Sr content was characteristic of carbonate technozems with an increased level of Ca (Mo-Cu ore occurrence). Increased accumulation of Ca and Sr in mowing plants was found in the technozems of the Zhireken Mo-Cu deposit: 35100 mg/kg (Ca) and 397 mg/kg (Sr). In general, the concentrations of Ca and Sr in technozem approach to their content in conditionally background soils and do not significantly contribute to the pollution of natural landscapes within the Urov-region of the biosphere.
Spatial heterogeneity of buried and recent soils in a drift sand area in North-Eastern Germany
Authors: Uchino Kazuki , Raab Alexandra , Bonhage Alexander , Schneider Anna , Raab Thomas , Wechler Klaus-Peter , Bauriegel Albrecht
Published: March 2022

In the North European Lowland, on the sandy deposits of the Weichselian glaciation, soils developed during periods of landscape stability are often conserved under windblown sand. However, small-scale changes of sediments and other soil forming factors can result in high spatial variation of soil properties in these landscapes; and relocation of soil material by geomorphic processes further increases the spatial heterogeneity of the soil landscape. These spatial variations in soil properties and conservation need to be considered in order to correctly decipher and interpret the buried soils as records of past environmental conditions.

In the forefield of the open-cast mine Cottbus-Nord, archaeological excavations in a dune and drift sand area revealed widespread buried soils of different characteristics. The densely spaced excavation trenches give exceptionally good insights into the pedosphere, allow for reconstructing the distribution of fossil and recent soils in a high spatial resolution, and offer good opportunities to improve the understanding of spatial and temporal patterns of soil formation. Remains of postpleistocene hunter-gatherer campsites were documented in archaeological excavations and found to be associated with a buried soil horizon.

We recorded the stratigraphy of soil profiles along more than 15 trenches within an area of about 20 ha, and additionally described the position of buried soils from GPR surveys and microdrone photogrammetry. In a recently opened, 455 m long trench, all characteristic soils and sediments of the study region could be observed and stratigraphically connected. Within this trench, four profiles were identified for further research. Each profile was classified and described according to WRB and German Guidelines for Soil Mapping; and was sampled and investigated through laboratory analyses including determination of organic matter, total carbon and nitrogen contents, soil colour identification, texture analysis, magnetic susceptibility measurement, metal content analysis using X-ray fluorescence analyzer and pH measurement. The compaction and cementation of soil horizons was assessed in situ with a pocket penetrometer.

Results show a small-scale mosaic of soils developed on fluvio-aeolian, limnic and aeolian sediments, high spatial variations in pedogenesis due to varying groundwater influence and intensity of horizontal and vertical leachate transport, and high variations in the erosion or conservation of fossil soils. The soil and sediment stratigraphy reflects several phases of landscape development: i) the formation of a Late Pleistocene soil on fluvio-aeolian deposits, ii) a fossilization by aeolian sands, iii) a stability phase with intensive podsolization and peat formation, and iv) a land use-induced aeolian remobilization of the sands. 
On the use, misuse and alternatives to probability distributions in descriptions of future climate
Authors: Thompson Erica , Katzav Joel , Risbey James , Stainforth David , Bradley Seamus , Frisch Matthias
Published: March 2022

Probability distribution functions (PDFs) are widely used in projections of future climate, projections of the impacts of future climate, and by climate services aiming to provide information to support practical climate change adaptation. Furthermore they are often used as a means of connecting these different activities and linking the variety of disciplines involved in climate science and climate social science.

Here we present an assessment of when such probability distributions misrepresent our uncertainty and a discussion of how we might recognise when such misrepresentations occur [1]. We go on to provide a collection of alternatives to probability distributions for use in such situations.

We start by categorising the ways that probability distributions can misrepresent the state of our knowledge about future climate. Such misrepresentation is of importance because it may adversely affect practical societal decisions, particularly in regard to adaptation activities, as well as misdirecting other research efforts.

We follow this with a discussion of how we might identify such misrepresentations. Doing so would help us communicate climate information better and consequently provided better reasoned and more robust scientific conclusions and societal decisions. Such assessments are an important component in the evaluation of climate information provided by climate services: what aspects of the information can be described as actionable.

We consider two perspectives on these issues. On one, available theory and evidence in climate science essentially excludes using probability distributions to represent our uncertainty. On the other, which represents a significant strand of current practice, probability distributions can legitimately be provided by relying on appropriate expert judgement and the recognition of associated risks.  We discuss the reasoning behind each perspective, framed in terms of the analysis of climate models and expert judgement.

Finally we explore alternatives to the use of probability distributions. We describe two formal alternatives, namely imprecise probabilities and possibilistic distribution functions, as well as some informal possibilistic alternatives. We suggest that the possibilistic alternatives are preferable.

 

[1] Katzav, Thompson, Risbey, Stainforth, Bradley and Frisch, On the appropriate and inappropriate uses of probability distributions in climate projections and some alternatives, Climatic Change, 2021.
Waves in the Earth’s core. 2: Diffusive Magneto-Coriolis waves.
Authors: Luo Jiawen , Jackson Andrew , Marti Philippe
Published: March 2022

Various types of waves exist in the Earth’s core. Waves associated with the magnetic field can leave a signature in the observed geomagnetic field, which may allow one to infer properties of the core. Among those, a balance of magnetic, Coriolis and pressure forces forms a type of waves known as Magneto-Coriolis (MC) waves. Previous studies of MC wave have mostly been focused on the ideal limit (without magnetic diffusion and viscous dissipation) with a columnar ansatz for the flow field. In this study, we investigate this problem by retaining the magnetic diffusion and three-dimensional flows in a full sphere. With several choices of axisymmetric background magnetic field, we analyse various branches of normal modes. The dependence of the normal mode's structure on the background field is clearly seen. A westward propagating branch with perfect columnar flows is found for some background B. We have also found eastward propagating modes constituted by flows with weaker columnarity. With the choice of Elsasser number Λ=1 (Coriolis and magnetic forces of similar magnitude), for axisymmetric background fields we find most of the MC modes have decay rates comparable or larger than their frequencies.
Uncertainties in marine ice-sheet retreat are dominated by basal melt
Authors: Berends Tijn , Stap Lennert , van de Wal Roderik
Published: March 2022

The loss of ice in Antarctica is dominated by the melting of floating ice shelves due to warming oceans. However, the relation between changing ocean temperatures and rates of sub-shelf melt is poorly constrained. Ice-sheet models currently employ a range of different approaches to this problem, varying in complexity from simple parameterizations based on linear temperature-melt relations to fully coupled ocean models. While several studies have compared two or more parameterisations, such efforts are complicated by the complex geometry of the Antarctic ice-sheet, as well as the uncertainty in (future) patterns of ocean circulation and atmospheric forcing.

The MISMIP/ISOMIP/MISOMIP family of experiments (Asay-Davis et al., 2016) provides a framework for intercomparing basal melt parameterisations in an idealized geometry, reducing the many difficulties of applying them in a realistic setting. Here, we present results of the MISOMIP1 experiment with the ice-sheet model IMAU-ICE. We show that the differences in simulated ice-sheet retreat caused by the use of different basal melt models are much larger than those arising from other model uncertainties such as the formulation of basal sliding, stress balance approximations, and model resolution. This suggests that basal melt is likely the largest source of uncertainty in future projections of Antarctic ice-sheet retreat.
The Seismic Cycle on Rate and State Faults with Different Evolution Laws and Fault Geometries 
Authors: Tal Yuval
Published: March 2022

Earthquakes occur by sudden slippage along pre-existing faults via a frictional instability. Laboratory-derived rate and state friction laws have emerged as powerful tools for investigating the mechanics of earthquakes. Two types of state‐variable evolution laws are commonly used to fit the experimental data, the aging and slip laws. The aging evolution law has been used extensively to model the earthquake cycle, including the nucleation, dynamic rupture propagation and arrest, and interseismic period. The slip law, which generally provides a better fit to rock friction experiments, has rarely been used in simulations of the whole seismic cycle. In addition, faults are zones with complex internal structure and non-planar geometry, which also affect the rupture process during the seismic cycle.

In this study, I examine the effects of fault geometry, state evolution law, and friction parameters on the earthquake source process with fully dynamic 2-D simulations of earthquake sequences on planar and non-planar faults. The numerical approach accounts for all stages in the seismic cycle and enables modeling slip that is comparable to the minimum wavelength of roughness. I test the statistics of the events in terms of static source parameters and analyze in detail the rupture process during the nucleation and dynamic propagation stages. For the same friction parameters and fault geometry, the slip law results in a more rapid weakening of the friction coefficient than the aging law. That leads to ruptures with smaller nucleation sizes, larger slip rates, and larger rupture speeds for the slip law, including transition to supershear. With the aging law, a small level of fault roughness is enough to introduce considerable complexity into the rupture process, with larger amount of aseismic slip and larger variability in earthquake sizes.  For the same level of roughness, those effects are significantly smaller in the case of the slip law.
How does thawing permafrost change groundwater discharge? A case study from southern Siberia 
Authors: Han Li , Park Hotaek , Menzel Lucas
Published: March 2022

In permafrost environments, groundwater recharge and groundwater flow are strongly affected by seasonal thawing and freezing cycles, the depth of the active layer, and the spatial coverage of permafrost. In such areas, groundwater is an important supply to the regional water resources, especially during the cold season when the frozen ground strongly restricts the water flows close to the ground and the runoff in rivers. However, due to absent or very limited groundwater observations in the permafrost domain, in combination with remoteness and harsh environments such as in Siberia, key processes and factors that control the subsurface dynamics on the large scale are not well understood yet. In a warming climate, the storage and movement of water in the subsurface system are expected to be altered through degrading permafrost and changing underground connections. However, due to the lack of corresponding studies, assumptions in this regard are very speculative.

Based on long-term daily river flow records (1950-2010) of large southern Siberian catchments (about 1,600,000 km² in total) with different permafrost conditions, we investigate the historical variations in magnitude, timing, and duration of low flow (as an indicator of groundwater dynamics) during the winter period. Our results show that the magnitude of low flow in the catchments has increased during 1950-2010, with the most considerable rise being noticed in the late 30-years period since 1980. Furthermore, we also found that the occurrence of the minflow (i.e., the minimum value of low flow) fluctuates between early and late winter in the catchments with sparse permafrost coverage. In contrast, in the catchments where continuous permafrost prevails, the minflow always occurs in late winter. Finally, for the catchments underlain by discontinuous permafrost, the timing of minflow shows relatively stable conditions in the earlier 30-year period. However, it starts fluctuating between early and late winter during the latter 30 years when a significant rise in low flow is observed. Given the unprecedented warming over the last decades in southern Siberia, these significant changes in both the magnitude and timing of low flow could be induced by the altered surface water-groundwater interactions that are triggered by the degrading permafrost. Overall, our results provide insights into the potential evolutions in the large-scale groundwater dynamics over varied temporal and spatial distributions of permafrost under a warming climate.
Spatial and temporal development of the dune instability
Authors: Claudin Philippe , Gadal Cyril , Narteau Clément , Ewing Ryan C , Gunn Andrew , Jerolmack Douglas , Andreotti Bruno
Published: March 2022

Wind-blown sand dunes emerge due the linear instability of a flat sedimentary bed. This instability has been studied in experiments and numerical models but rarely in the field, because of the large time and length scales involved. Here we examine dune formation at the upwind margin of the White Sands Dune Field in New Mexico (USA), using 4 years of lidar topographic data to follow the spatial and temporal development of incipient dunes. Data quantify dune wavelength, growth rate, and propagation velocity and also the characteristic length scale associated with the growth process. We show that all these measurements are in quantitative agreement with predictions from linear stability analysis. This validation makes it possible to use the theory to reliably interpret dune-pattern characteristics and provide quantitative constraints on associated wind regimes and sediment properties, where direct local measurements are not available or feasible.

Reference: Gadal et al., Geophys. Res. Lett. 47, e2020GL088919 (2020).
Investigation of the flicker nature of the day-boundary differences of GNSS orbits
Authors: Ait-Lakbir Hanane , Santamaria Alvaro , Perosanz Félix , Ray Jim
Published: March 2022

Day-boundary orbit comparison is one of the criteria used to assess the performance of GNSS orbits. The overall statistics of orbit discontinuities such as RMS are usually computed to assess dynamical modeling and the processing configurations. Additional information about the systematic orbit errors is also accessible through their spectral content.

A particular feature is the flicker or 1/f noise describing the low-frequency band, indicating time-correlated orbital errors. This type of noise is observed not only in the orbits but also in other GNSS-derived geodetic time series such as in station positions, Earth rotation parameters,... The sources explaining this feature, either from the GNSS orbit modeling or from unaccounted orbital perturbations, are not well understood. By computing simulated orbits, we look at possible causes in the orbit determination processing.
West Greenland surface runoff extent, mapped from daily MODIS imagery 2000 to 2021
Authors: Machguth Horst , Tedstone Andrew , Mattea Enrico
Published: March 2022

Streams and lakes develop each summer over the marginal regions of the Greenland ice sheet. These hydrological systems reach well into the accumulation area and indicate that surface runoff of meltwater is an important component of the mass balance of the Greenland ice sheet. Here we map the slush limit, a proxy for the extent of surface runoff, using daily MODIS data (500 m spatial resolution) for the 22 melt seasons from 2000 to 2021. We develop an automated algorithm capable of detecting daily slush limits, provided sufficient image quality. The algorithm is applied to Greenland's west coast. Albeit MODIS' spatial resolution is too coarse to resolve streams, slush fields or lakes, the results highly agree to surface runoff mapping from better resolution satellite imagery. The data document the evolution of the slush limit across latitudes and during the individual melt seasons. We find significant increasing trends in slush limits until the year 2012, but not thereafter. We show that the slush limit typically rises quickly early in the melt season, but upward migration halts before melting ceases. The reasons behind this behaviour remain somewhat enigmatic. For the year 2012, we are able to demonstrate that upward migration of surface runoff stopped early in the melt season, at the upper margin of the ice slabs. These thick and continuous ice layers are located close to the surface, in the firn, and prevent percolation of melt into the otherwise porous firn. Had the ice slabs extended further into the accumulation area, the summer 2012 saw sufficient energy to raise the slush limit by another ~300 m in elevation.
A Climatology of Tropical Transitions in the North Atlantic Ocean
Authors: Calvo-Sancho Carlos , González-Alemán Juan Jesús , Bolgiani Pedro , Santos-Muñoz Daniel , Farrán José Ignacio , Sastre Mariano , Martín María Luisa
Published: March 2022

In recent years, western Europe has been threatened by anomalous tropical cyclones, developed from tropical transition (TT) processes in which a baroclinic cyclone becomes in a fully barotropic cyclone. Thirty-three tropical transition events were identified in the North Atlantic basin during the period 1979-2019 using ERA5 and HURDAT datasets. The TTs show a favored seasonality covering 70% of total between September and November.

A TT climatology is built and analyzed using large-scale storm-centered composites to study their common features and highlighting their differences respect the long-term climatology. The results reveal that TT synoptic environment is mainly characterized by a trough at 300 hPa and a strong anticyclone located north of the cyclone. In addition, a previous westerlies meridional trough with quasigeostrophic forcing acts as precursor. As the ERA5 does not accurately represent the diabatic processes due to its horizontal resolution, the deepening of mean sea level pressure is not shown in the composites. The average Potential Vorticity 300-200 hPa (PV) shows a decreasing in the upper troposphere around the cyclones as the moment of TT is approaching, while the PV is increasing in the lower troposphere. This PV conjunction promotes low-level wind speed intensification around the cyclone center that is linked with differential diabatic heat source in the low troposphere.
Heatwave-related extreme rainfall events
Authors: Sauter Christoph , White Christopher , Fowler Hayley , Westra Seth
Published: March 2022

Research on heatwave-related impacts typically focusses on risks to health or critical infrastructure. However, since high temperatures are an important element of convection-driven extreme rainfall events that can trigger flash floods, heatwave-induced extreme rainfall events are also important when considering heatwave impacts. Heavy rainfall events following heatwaves might alleviate the direct impacts of the heat but introduce other risks related to flash floods.

Using sub-daily rainfall observations on a global scale, we show that short duration rainfall extremes are indeed more likely to occur if preceded by a heatwave than compared to non-heatwave events. In addition, these rainfall events are more intense as well. However, this link is dependent on the region, with some locations, especially arid regions, showing no relationship between the two phenomena at all. We also investigate if hotter heatwaves are more likely to be followed by rainfall extremes. This could have implications for future heatwaves which are projected to become more intense.
Segmentation of subducting oceanic plates by brittle-ductile damage
Authors: Gerya Taras , Bercovici David , Becker Thorsten
Published: March 2022

Subducting oceanic plates experience intense normal faulting during bending that accommodates the transition from horizontal to downward motion at the outer rise at subduction trenches. We investigated numerically the consequences of the plate bending on the mechanical properties of subducting slabs using 2D subduction models in which both brittle and ductile deformation, as well as grain size evolution, are tracked and coupled self-consistently. Numerical results suggest that pervasive brittle-ductile slab damage and segmentation can occur at the outer rise region and under the forearc that strongly affects subsequent evolution of subducting slabs in the mantle. This slab-damage phenomenon explains the subduction dichotomy of strong plates and weak slabs, the development of large-offset normal faults near trenches and the occurrence of segmented seismic velocity anomalies and interfaces imaged within subducted slabs. Furthermore, brittle-viscously damaged slabs show a strong tendency for slab breakoff at elevated mantle temperatures that may have destabilized continued oceanic subduction and plate tectonics in the Precambrian (Gerya et al., 2021).

Gerya, T.V., Bercovici, D., Becker, T.W. (2021) Dynamic slab segmentation due to brittle-ductile damage in the outer rise. Nature, 599, 245-250.
Constraining Upper Mantle Viscosity Using Temperature and Water Content Inferred from Seismic and Magnetotelluric Data
Authors: Ramirez Florence , Selway Kate , Conrad Clint , Lithgow-Bertelloni Carolina
Published: March 2022

Mantle viscosity controls a variety of geodynamic processes such as glacial isostatic adjustment (GIA), but it is poorly constrained because it cannot be measured directly from geophysical measurements. To improve viscosity estimates, we develop a method that computes viscosity using empirical viscosity flow laws and mantle parameters (temperature and water content) inferred from geophysical observations. We find that combining both seismic and magnetotelluric constraints allows us to place significantly tighter bounds on viscosity estimates compared to either geophysical observation by itself. In particular, electrical conductivity inferred from MT data can determine whether upper mantle minerals are hydrated, which is not seismically detectible but significantly reduces viscosity. Additionally, we show that rock composition should be considered when estimating viscosity from geophysical data because composition directly affects both seismic velocity and electrical conductivity. Therefore, temperature and water content is more uncertain for rocks of unknown composition, which makes viscosity also more uncertain. Furthermore, calculations that assume pure thermal control of seismic velocity may misinterpret compositional heterogeneity for temperature variations, producing erroneous predictions of mantle temperature and viscosity. Stress and grain size also affect the viscosity and its associated uncertainty, particularly via their controls on deformation regime. Overall, mantle viscosity can be estimated best when both seismic and MT data are available and the mantle composition, grain size and stress can be estimated. Collecting additional MT data probably offers the greatest opportunity to improve geodynamic or GIA models that rely on viscosity estimates.
Exploiting GPU capability in the fully spectral magnetohydrodynamics code QuICC
Authors: Tolmachev Dmitrii , Jackson Andrew , Marti Philippe , Castiglioni Giacomo
Published: March 2022

QuiCC is a code designed to solve the equations of magnetohydrodynamics in a full sphere and other geometries. The aim is to provide understanding of the dynamo process
that sustains planetary magnetic fields for billions of years by thermally-driven convective motion of an electrically-conducting fluid. It also aims to provide the first
clues as to how and why the magnetic fields can undergo reversals. The code must solve the coupled equations of conservation of momentum (the Navier Stokes equation), Maxwell's equations of electrodynamics and the equation of heat transfer. For accuracy and to facilitate imposition of boundary conditions,
a fully spectral method is used in which angular variables in a spherical polar coordinate system are expanded in spherical harmonics, and radial variables are expanded in a
special polynomial expansion in Jones-Worland polynomials. As a result the coordinate singularities at the north and south poles and at the origin disappear.
The code is designed to run on upward of 10^4 processors using MPI and shows excellent scaling.
At the heart of the method is the ability to move between physical and spectral space by a variety of exact transforms: these involve the well-known Fast Fourier Transform (FFT) and also the Legendre transform and Jones-Worland transform.
In this talk we will focus on the latest advancements in the field of fast GPU algorithms for these types of discrete transforms. We present an extension to the publicly-released VkFFT library - GPU Fast Fourier Transform library for Vulkan, CUDA, HIP and OpenCL, that allows the calculation of the Discrete Cosine Transforms of types I-IV. This is a very exciting addition to what VkFFT can do as DCTs are often used in image processing, data compression and numerous other scientific tasks.
So far, this is the first publicly available optimized GPU implementation of DCTs. We also present our progress in creating efficient Spherical Harmonic transforms (SHTs) and radial transforms using  GPU implementations.  This talk will present Jones-Worland and Associated Legendre Polynomial Transforms for modern GPU architectures, implemented based on the VkFFT runtime kernel optimization model. Combined, they can be used to create a new era of full-sphere models for planetary simulations in geophysics.
How will belowground plant biomass in deep soil respond to warming in temperate forests?
Authors: Sun Binyan , Zosso Cyrill , Wiesenberg Guido , Schmidt Michael , Torn Margaret
Published: March 2022

IPCC climate models (RCP8.5) suggest 4°C warming until 2100, which could potentially accelerate soil carbon loss, greenhouse gas release, and thus promote global warming. Despite low carbon concentrations, subsoils (> 30 cm) store more than half of the total global soil carbon stocks. Retaining this is crucial to mitigate soil carbon greenhouse gas release. However, how deep soil carbon will respond to warming and how increased root-derived carbon could contribute to carbon stabilization in subsoils is under-studied and largely unknown. We aim to i) quantify the decomposition rate of root-litter at different depths with a +4°C warming field experiment, ii) assess whether various plant polymers will degrade differently in heated and control plots, iii) identify decomposition products of plant biomass remaining after three years of incubation.

In a field experiment in a temperate forest, 13C labelled root-litter was added at different soil depths (10-14, 45-49, 85-89 cm) in 2016 and retrieved half of the cores in 2017 and the remaining half in 2019. So far, we measured bulk soil carbon concentrations and d13C-composition of individual microbial biomarkers (PLFA).

Results confirm that bulk carbon concentrations and d13C values follow typical depth trends, except for the three horizons containing 13C labelled root-litter incubations. Next, we will quantify above- and below-ground biomarkers (cutin and suberin, respectively) and determine compound-specific 13C-composition in each molecular fraction in heated and control plots. We suspect that the presumably difficult to degrade compounds (cutin, suberin, and lignin polymers) will degrade slower than bulk organic matter over the observation period, and likely faster in heated than control plots. However, early results from warming experiments provide circumstantial evidence that also these compounds might degrade in synchrony with the bulk organic matter.
A new frequency-domain based approach for detecting low frequency seismic events: An application to the Mt. Vesuvius seismicity
Authors: Manzo Roberto , Galluzzo Danilo , La Rocca Mario , Di Maio Rosa
Published: March 2022

The detection of low energy seismic events and tremor related to volcanic activity in areas characterized by high background noise represents a crucial challenge for monitoring and surveillance purposes. In the last three years, the seismicity of the Mt. Vesuvius (southern Italy) has been characterized by low-magnitude volcano tectonic earthquakes, the most of which are located at depth shallower than 3 km b.s.l., while very few low-frequency earthquakes and tremor episodes are located at about 6-7 km depth. It is well known that magmatic and hydrothermal systems can play an important role in the generation of low-frequency seismic events, which could be important precursors for assessing the reawakening of a volcano. Therefore, our main objective is to develop a methodology for detecting the presence of low frequency (LF) events hidden in the background noise and not identifiable by classical detection procedures. In particular, we suggest a frequency domain approach based on a joint application of coherence analysis among signals from local network seismic stations and parameterization of the amplitude spectra according to the statistical moments. The proposed methodology has been applied to the analysis of continuous seismic signals recorded over three years at Mt. Vesuvius. Spectral parameters, such as central frequency W, shape factor d and coherence c, were evaluated on 30-s windows signals in the frequency range between 2 and 40 Hz. The selection of the signal windows that could potentially contain low-frequency events or tremor signals was performed according to the following criteria: a) 0.45 < δ < 0.65; b) 3 Hz < W < 6 Hz and c) c greater than 0.5, which are based on the results of preliminary analyses of the seismicity observed at Mt. Vesuvius. The detected signal windows were visually inspected and compared with the seismic catalogues to eliminate those corresponding to earthquakes occurred outside the area of interest. For the three-years of analyzed data, more than 200 episodes of low frequency signals were identified, 120 of which are not present in the seismic catalog. Most of them appear as low-amplitude tremor episodes, with no clear evidence of P and S phases, hidden in the noisy raw signals but visible at the entire seismic network after proper signal filtering. Compared to the few LF events detected and analysed in the past, our findings suggest that the proposed methodology can be an efficient tool for detecting low-amplitude signals not easily identifiable in the background noise and could represent an improvement for the monitoring system of the Mt. Vesuvius volcanic area.