bluuebunny/crossref_metadata_2025 huggingface dataset:
Updating the ESA Earth System Model for Future Gravity Missions Simulation Studies
Authors: Shihora Linus , Balidakis Kyriakos , Dill Robert , Dobslaw Henryk
Published: March 2024

The ESA Earth System Model (ESA ESM) provides a synthetic data-set of the time-variable global gravity field that includes realistic mass variations in atmosphere, oceans, terrestrial water storage, continental ice-sheets, and the solid Earth on a wide set of spatial and temporal frequencies. It was widely applied as a source model in simulations of for gravity missions, but has been also applied to study novel gravity observing concepts on the ground. For that purpose, the ESM needs to include a wide range of signals even at very small spatial scales which might not yet have been reliably observed by any active mission.In this contribution, we present first steps towards an update to the current ESA ESM. We focus in particular on an evolved oceanic component which will newly include (a) deep oceanic transport variations in the Atlantic Overturning Circulation and the associated variation in oceanic bottom pressure along the shelf slope of the Western boundary; (b) an update to the realistically perturbed de-aliasing model and (c) the inclusion of the Sea-Level Equation for spatially variable barystatic sea-level variations and global mass conservation.
Evaluation of the Impact of Uniform and Non-Uniform Resolution Implementations in Numerical Weather Prediction Models over the Accuracy of Short-Term Wind Prediction
Authors: Yalcin Ruhi Deniz , Yilmaz M. Tugrul , Yucel İsmail
Published: March 2024

The increasing integration of renewable energy resources to the national grids necessitatesaccurate prediction of power generation from those sources in terms of secure operation ofelectricity grid system and energy trading. Electricity generation of renewable energy powerplants such as wind and solar are inherently affected by weather conditions. The wind conditionparticularly is affected by surface characteristics such as orography and vegetation, therefore it isthe one of the near surface atmospheric variables having the strongest local variability. The high-resolution Numerical Weather Prediction (NWP) models are utilized to take the local conditionsinto account. WRF model is the one of the most common NWP models having been widelyinvestigated by various researchers. On the other hand, The Model for Prediction Across Scales(MPAS) is a relatively new NWP model utilizing non-uniform mesh structures, developed by theNational Center for Environmental Predictions (NCEP). However, there are limited studies in theliterature which compare the prediction performance of WRF and MPAS model in terms ofsurface wind speed. This study evaluates the prediction accuracy of near surface wind of twodownscaled NWP models namely, WRF-ARW and MPAS. Both models are configured withalmost identical physics suites and initialized with 3 hourly 00-UTC initialization of GlobalForecast System (GFS) data. The model outputs are obtained at 10 minutes interval for 48 hourshorizon. Hourly averaged model results are compared with observations from 104 on-sitemeteorological stations located in Turkiye having different complexity in terms of correlationcoefficient and RMSE.
The importance of making geoethics a central concern of Sri Lankan education strategy
Authors: Di Capua Giuseppe , Gunawardana Udaya
Published: March 2024

Like numerous regions worldwide, Sri Lanka faces significant environmental challenges that endanger its biodiversity, natural resources, and the well-being of its population. Predominant issues encompass water and air pollution, land degradation, deforestation, improper waste disposal, consequences of climate change, disaster risks, as well as the loss of biodiversity and geodiversity. The nexus between political, economic, and social factors contributes to these geo-environmental challenges, often exacerbated by the politicization of the environmental issues in Sri Lanka. However, it is crucial to acknowledge that human activities primarily drive these conditions. Gunnar Myrdal’s Soft State theory asserts that despite the existence of multiple governing bodies, regulations, and laws, humans strategically transcend the environment leading to the depletion of geo-environmental resources within a context of strong societal inequalities, particularly in developing countries influenced by the historical conditioning of colonial interests by developed nations. A philosophical exploration of this issue emphasizes the pivotal role of human indifference towards the environment and natural resources in causing these challenges. To address this issue effectively, a transformation in people's attitudes is imperative, and education emerges as the most potent tool for this purpose. However, a careful analysis of Sri Lanka's primary and secondary school curricula reveals an absence of a dedicated discipline addressing the philosophical and social dimensions of the geo-environmental matter. In light of this, the incorporation of subjects such as geoethics, which specifically addresses the ethical problems in the human-environment interaction, becomes paramount. Integrating geoethics into the educational framework, particularly at primary and secondary levels, stands as the foundation of a sustainable and responsible strategic approach to many societal and environmental problems. This educational strategy should envision as the most important solution to mitigate the majority of geo-environmental problems in Sri Lanka, fostering environmentally sensitive and responsible citizens.
Impact of Interplanetary Coronal Mass Ejections (ICME) on the geomagnetic tail from THEMIS observations
Authors: Alqeeq Soboh , Fontaine Dominique , Le Contel Olivier , Akhavan-Tafti Mojtaba , Cazzola Emanuele , Atilaw Tsige
Published: March 2024

We focus on a well-defined interplanetary coronal mass ejection (ICME) with a dynamic pressure Pdyn > 20 nPa, in December 2015. ACE observations and OMNI data allowed to identify ahead of Earth the expected features with shock and sheath regions preceding a magnetic cloud. This ICME triggered a storm in the magnetosphere with a storm sudden commencement (SSC) phase (SYM‐H ~ +50 nT) followed by a growth phase (SYM‐H < −150 nT at the minimum) and a long recovery phase lasting several days.We investigate the global impact of this ICME on the Earth's magnetotail from observations by the NASA mission THEMIS. Indeed we estimate the total pressure exerted on the magnetotail current sheet. We find that the current sheet is compressed to ~ >2nP in the main phase, i.e. 4 times more than in the quiet phase before the event. In contrast, the pressure gradually decreases in the recovery phase and approximately comes back towards quiet phase values. According to the tracking of magnetic field lines using the Tsyganenko T96 magnetic field model, the current sheet appears stretched right from the SSC phase, and even more than during the main phase, before returning progressively to a shape comparable to the quiet phase. We quantify and discuss these effects to provide a more precise description of the magnetospheric geomagnetic activity during solar events.
Evaluating the Synergy of Wind and Wave Energy in European Coastal Regions using Satellite Altimetry data
Authors: Ponce de León Alvarez Sonia , Bettencourt João , Ringwood John , Benveniste Jérôme
Published: March 2024

In this research, we present a comprehensive analysis of the combined potential of wind and wave energy across various European coastal locations. Our primary aim is to explore the viability of leveraging satellite altimetry for assessing the potential of wind and wave energy synergies on the European shelf. This exploration is driven by the premise that integrating wind and wave energy sources could significantly reduce the variability in energy supply. Our methodology employs the homogenized, multi-mission altimeter dataset provided by the European Space Agency's Sea State Climate Change Initiative (Sea_State_cci). This dataset spans 26 years, from January 1991 to December 2018, offering an extensive temporal and spatial coverage for estimating wind and wave power densities at various sites.
To calculate wave power density, we utilize an empirical model that derives the wave energy period from the altimeter's Ku-band significant wave height and radar backscatter coefficient. Our findings indicate a notable correlation between wind and wave energy in the Mediterranean, in contrast to the North Atlantic locations. Consequently, the Western North Atlantic seems to be the most promising region for combined wind and wave energy farms, considering the benefits of simultaneous exploitation.
The study also reveals interesting patterns in the relationship between the variability and average wave power across different sites, a critical factor for any marine renewable energy strategy. Notably, we observe that the overall variability in energy supply tends to decrease with an increase in average wave power, primarily because the more powerful swell waves exhibit a lower correlation with local wind conditions. This insight is pivotal for understanding the dynamics of marine renewable energy sources and optimizing their exploitation.
Root hairs facilitate root water uptake across soil textures – a numerical study
Authors: Duddek Patrick , Ahmed Mutez Ali , Javaux Mathieu , Vanderborght Jan , Lovric Goran , King Andrew , Carminati Andrea
Published: March 2024

By substantially increasing the surface area of roots available for soil resource capture, root hairs have been hypothesised to facilitate root water uptake, particularly in dry soil conditions. However, existing experimental and computational studies have shown that the effect of root hairs on water uptake cannot be generalised across soils and plant species.The objective of our study is to investigate to what extent and under which soil conditions root hairs facilitate root water uptake. Ultimately we aim to gain a mechanistic understanding of the effect of root hairs on root water uptake across soil textures.We scanned maize (Zea Mays L.) roots grown in two soil types (loamy and sandy soil) using synchrotron-based X-ray CT. We utilized an image‐based modelling approach to simulate water flow through the soil-root continuum by solving the flow equations numerically. This approach allowed us to incorporate rhizosphere properties (e.g. root-soil contact) and root hair shrinkage into the image-based model.Experimental and numerical results show that under dry soil conditions (-1 to -0.1 MPa) root hairs attenuate the gradient in soil matric potential across the rhizosphere. This results in a more effective water extraction compared to a hairless root. Our model revealed that the effect of hairs is determined by soil properties (e.g. soil porosity), root hair traits (e.g. length and density) and the capacity of hairs to remain turgid under drought stress. Compared to densely packed fine textured soils, the effect of hairs is more pronounced in coarse textured soils and loosely packed fine textured soil. This is explained by the steeper hydraulic conductivity curves of these soils.In conclusion, our results show that the effect of root hairs is determined by root-soil contact, which depends on soil properties, and root hair shrinkage.
Cryogrid modelling of permafrost temperature in the Maritime Antarctic (Barton Peninsula, King George Island)
Authors: Baptista Joana , Vieira Gonçalo , Westermann Sebastian , Lee Hyoungseok
Published: March 2024

The temperature dynamics of permafrost is crucial for ecosystem processes in the ice-free areas of the Antarctic Peninsula, where a strong long-term warming trend with an increase of 3.4 ºC in the mean annual air temperature since 1950 has been recorded (Turner et al., 2020). The consequences of this warming on past and future permafrost degradation are still not fully understood, mainly due to the sparse spatial coverage and short time span of borehole data, only available after the mid to late 2000’s (Vieira et al., 2010; Bockheim et al., 2013). The Cryogrid Community Model is an adaptable toolbox for simulating the ground thermal regime and the ice/water balance for permafrost (Westermann et al., 2017, 2022). The modular structure allows combinations of classes that represent the snow conditions and the subsurface materials. Here, permafrost temperatures from the 13 m depth King Sejong Station borehole (KSS), from Barton Peninsula, King George Island were used to assess the performance of Cryogrid and the quality of ERA5 forcing. For evaluating model performance, the setup was firstly used in its basic version with the GROUND_freeW_ubtf class, which considers a temperature boundary condition, for which air temperatures from KSS were used. Modifications to the stratigraphy and parameters were performed to achieve the strongest correlations and lower Mean Absolute Errors (MAE) between the simulated and observed ground temperature at nine depth levels. This approach allowed for the definition of the stratigraphy and parameters later used with the GROUND_freeW_seb_snow class, in which the surface energy balance scheme is included. The results show that ERA5 air temperature underestimates the records from KSS, especially during the summer, impacting the representation of surface warming. This deviation was corrected using linear regression corrected temperatures. The Cryogrid modelling results indicate an overestimation of the ground temperature during the thawing season and an underestimation during the freezing season, being the difference more pronounced at the surface. A strong correlation was shown between the simulated and measured ground temperatures in KSS down to 6 m depth (r>0.9) with MAE ranging from 0.4 to 0.9 ºC. Below 6 m the correlation weakens to 0.45 (13 m depth) due to differences in heat propagation and lack of temperature oscillation on the records when compared with the simulation. However, MAE values are residual, ranging from 0.1 to 0.2 ºC. The active layer thickness was overestimated in about 1 m. This research was funded by the project THAWIMPACT (FCT2022.06628.PTDC) and by CEG/IGOT (UIDP/00295/2020). Joana Baptista is funded by the FCT with a doctoral grant (2021.05119.BD).
Analysis of the first data collected by the High Accuracy Accelerometer (HAA) onboard the JUICE spacecraft
Authors: De Filippis Umberto , Cappuccio Paolo , Di benedetto Mauro , Iess Luciano
Published: March 2024

The JUpiter ICy moons Explorer (JUICE) mission is a cornerstone of the European Space Agency (ESA). The mission was launched in April 2023 from Kourou with an Ariane V launcher and is expected to arrive at Jupiter in 2031. JUICE will investigate the gas giant planet Jupiter, its atmosphere, magnetosphere, and its icy moons, Ganymede, Europa and Callisto. The mission will focus on Ganymede, during the low altitude circular and polar orbital phase.The spacecraft will carry a suite of scientific instruments, including a camera, a spectrometer, a radar system, a laser altimeter, and a suite of instrumentation dedicated to radio science experiments: the Ka-band Transponder (KaT), the Ultra Stable Oscillator (USO) and the High Accuracy Accelerometer (HAA).The Gravity & Geophysics of Jupiter and Galilean Moons experiment (3GM) instrumentation will be used to study the gravity field up to degree and order 40 of Ganymede and the extent of internal oceans on the icy moons. Furthermore, during radio occultations, the 3GM experiment will investigate the structure of the neutral atmospheres and ionospheres of Jupiter and its moons.The HAA accelerometer will play a fundamental role during the 3GM experiment even if it will not directly measure any of the physical quantities connected with the experiment scientific goals. It aims to measure the perturbations of non-gravitational forces that the JUICE spacecraft will undergo during 3GM measurements with an accuracy of  in the frequency band of  Hz. Such perturbations are mainly induced by the propellant sloshing within the tanks, especially during the moon flybys. These perturbing accelerations are included in the orbital determination algorithm. In this work we show the first inflight data collected by the HAA instrument during the cruise. We present the data collected after launch (April-June 2023) during the deployment of the spacecraft moving appendages such as the RIME antenna, the Langmuir probes and the magnetometer boom. The analysis of these data aims to preliminary characterize the instrument behaviour and the spacecraft dynamic environment. Additionally, we show the analysis of the HAA data collected during the first payload checkout (January 2024), with a focus on the preliminary assessment on the instrument in-flight scientific performances.  
Reactive transport modeling of the effects of seafloor sediment hydrodynamics on ocean alkalinization
Authors: Ramasamy Murugan , Amann Thorben , Moosdorf Nils
Published: March 2024

Coastal environments are pivotal in the global carbon cycle. Introducing alkaline materials, like olivine-rich rocks, for enhanced weathering and ocean alkalinity enhancement (OAE) holds promise for atmospheric carbon sequestration. Material weathering is incomplete in the water column but occurs significantly after deposition on the ground. This study elucidates the intricate geochemical processes that occur after deposition of the introduced olivine along coastal seabeds, focusing on the impact of mixing zones between terrestrial groundwater and saltwater in the sediment. These zones, where diverse water compositions converge, may promote rock dissolution, influencing OAE. The collective interaction of these factors with OAE remains insufficiently explored. Utilizing a 2D modeling approach with FEFLOW coupled with piChem software, our research comprehensively simulates dynamic coastal systems. The model, incorporating multi-component transport, assesses factors like flow rates, groundwater and seawater composition, alkaline material concentration, and sediment permeability, impacting carbon sequestration efficacy. Results showcase olivine settling dynamics, revealing varying times for different-sized grains to reach the seafloor. Notably, 10 µm olivine grains take about a month to settle in 1000 m water depth, while 100 µm grains settle within days. Preliminary findings highlight substantial mineral weathering on the seafloor, emphasizing hydrological conditions' significant influence. Discussions focus the implications of alkalinity transfer into the sediment, crucial for understanding overall process efficiency. This ongoing research emphasizes the need for a holistic understanding of geochemical dynamics in coastal environments to optimize carbon sequestration through OAE.
Mercury(Hg) Speciation in different environmental compartments of the India: A Thermo-desorption-Driven Approach
Authors: Padalkar Prasad , Chakraborty Parthasarathi , Dey Arup , Bhattacharya Malay
Published: March 2024

India has a rich environmental ecosystem, stretching from high-rise mountains to coastal areas. The surge in industrialization and economic growth in the country has imposed a considerable burden on the environment, hindering progress toward sustainable development goals. One critical concern in this context is mercury (Hg) pollution, where special attention is needed. On June 18th 2018, India ratified the Minamata Convention to address Hg pollution. However, a significant data gap exists regarding comprehensive baseline information from different environmental compartments in India, which is crucial for assessing the convention's effects. To bridge this research gap, an effort was made to access Hg distribution and speciation in various environments. For this study, soil and sediments samples were collected from diverse regions: the metropolitan city (Kochi, Kerala, India), agricultural lands (Dhapa, Kolkata), hilly areas (Tea Garden, Darjeeling), and the coastal sediments (collected from continental shelf/slope of the west coast of India). The total soil Hg concentration in metropolitan soil, agricultural soil, and tea garden soil ranged from 16 ± 0.84 µg/kg to 2674 ± 133 µg/kg, 726 ± 36 µg/kg to 2318 ± 115 µg/kg, and 158 ± 7 µg/kg to 9441 ± 472 µg/kg, respectively. Meanwhile, the total Hg concentration in the studied continental shelf sediment samples varied from 8 ± 0.14 µg/kg to 50 ± 2 µg/kg. This result shows that a significantly higher total concentration of Hg in the tea garden soil, whereas lowest Hg concentration were observed in the coastal sediment. Chemical speciation of Hg was carried out using thermo-desorption technique. It was found that the major part of the total Hg was predominantly associated with organic matter in the soil as well as in the coastal sediments. This indicates that organic matter was key host for Hg in soil as well as in coastal sediments. Interestingly, the second-highest fraction in the all types of soil was Hg0, indicating more reduction of Hg in the soil. The elevated Hg0 levels in the soils raises concerns due to its high volatility at ambient temperatures. The evasion of Hg0 from the soil can serve as a significant non-point source of Hg, posing potential risks to individuals living in these areas. Prolonged exposure to this toxic metal could lead to adverse health effects for the local population. Further in the sediments, Hg associated with sulphide was the second dominant Hg fraction, playing crucial role in Hg stability. Overall, these findings not only help to stakeholders and policy makers in addressing Hg pollution, but also contributes to progress towards achieving Sustainable Development Goals.
Cold – water springs as integral part of geothermal systems: an example from Sri Lanka
Authors: Bandara Dilshan , Smit Jeroen , Wohnlich Stefan , Heinze Thomas
Published: March 2024

Hot water springs are typical surface manifestations of a geothermal system, especially in low enthalpy, amagmatic systems. In many of these systems, numerous cold-water springs are often associated with hot water springs. The smaller number of hot water springs and the wider spatial distribution between them make it difficult to perform a comprehensive study of such a geothermal system. In this case, associated cold water springs can be of particular help in understanding the hydrogeological setting of the geothermal system which is vital information for any future geothermal exploration programs.There are 9 known hot springs in Sri Lanka, however they are spread over a larger area of the eastern lowlands of the country. On the other hand, there are over 225 known cold-water springs distributed among the hot water springs, making Sri Lanka a perfect location for a case study.Most hot water springs are located at a great distance from their recharge zone (~ 50-100 km). With the exception of very few springs, cold water springs have short recharge to discharge distances (< 25 km). Geochemical and isotopic studies of the hot springs and the nearby cold springs show that both kinds are of the same origin and recharge at similar altitudes (> 600m). The electrical resistivity of cold-water springs is comparatively higher than that of rain and fresh surface water, but lower than that of hot water springs. This suggests that these cold spring waters also travel longer through the fault/fracture network through which hot spring waters circulate from recharge zones to discharge zones. These observations of cold-water springs show that they are also part of the geothermal system in Sri Lanka and reveal important information about the fluid flow paths of the geothermal system. The results and observations of the present study highlight the importance of cold-water springs in understanding the hydrogeological setting of a geothermal system. In addition, the new knowledge will be of significant benefit to future geothermal exploration programs, particularly in systems with a smaller number of hot water springs spread over a larger area.
Accurate information on land elevation is key – Towards proper coastal flood risk assessment in data-sparse river deltas and coastal lowlands
Authors: Seeger Katharina , Minderhoud Philip S. J.
Published: March 2024

Many river deltas and coastal lowlands in the world are densely populated and located in the Global South. Due to relative sea-level rise (rSLR), they face an increasing risk of drowning and flooding and thus require reliable impact and risk assessments of rSLR and flooding. As both sea-level rise (SLR) impact and flood inundation are closely related to land elevation, the quality of these assessments largely relies on vertical accuracy and proper datum referencing of the elevation data used. However, high-quality digital elevation models (DEMs) representing elevation at spatial resolutions and vertical accuracies at centimetre to decimetre scale are still not available or accessible for major parts of the Earth’s coasts, including densely populated Asian and African coastal lowlands or Small Island Development States. In these regions, global DEMs are often used even though they suffer from large vertical errors and artefacts, thereby impacting the quality of flood exposure assessments. While the accuracy of those global DEMs is extensively addressed both in their dataset documentation and literature, the relevance and proper vertical datum conversion from global geoid and ellipsoid models to local sea level is often still omitted in many applied studies; in part because the process is complicated in data-poor regions, where tide gauge records are often insufficient or outdated. Sea surface data based on satellite altimetry may serve as a substitute but the referencing of the land elevation and sea surface data to a common vertical datum includes several steps of datum conversion beforehand, which – if not performed properly – can introduce local errors of sea level to the land elevation up to several metres.In this study, we test and present a workflow of globally consistent vertical datum conversion of elevation data to continuous local mean sea level by integrating globally available data on coastal elevation and sea surface. We apply our approach to recently published global DEMs and validate them for several key coastal lowlands such as the Ayeyarwady and Mekong Deltas, and show the improvement of the performance of global DEMs for impact assessments in data-poor regions. This proves the potential to improve impact assessments of SLR and flood exposure in coastal lowlands around the world where high-quality elevation information is not accessible.
Advances and challenges in quantification of greenhouse gas emissions by UAVs – A review
Authors: Allen Grant , McQuilkin Jamie , Yong Han
Published: March 2024

Accurate and efficient quantification of emissions from sources (both natural and anthropogenic) underpins our understanding of the natural drivers of climate change and the success of emissions mitigation strategies. While there exists many excellent methods and measurement networks from which to constrain emissions at national and regional scales (e.g. through transport inversion modelling), a dynamic and accurate picture of emissions from hotspot sources (e.g. landfill, oil and gas infrastructure etc) remains a technical and scientific challenge. Recent international agreements and national regulations to monitor, report, and validate GHG emissions by sector, all require robust and standardised approaches to directly measure emissions to prioritise targets for emissions reduction and mitigation.Emissions quantification by UAV survey is a rapidly expanding field both academically and commercially. Since the first known report on the feasibility of such a capability around 10 years ago (2014), there now exists a mature international academic community, which continues to refine and validate methods, and a growing international commercial sector that can now provide survey capability and drive further technological development. However, transparency and robust validation of methods remains a barrier to largescale adoption by regulators and those compiling national emissions inventories.This paper will review recent advances in unmanned aerial vehicle (UAV) platforms, GHG instrumentation, methodologies and field operations in the pursuit of emissions quantification. Building on Shaw et al., 2021 (https://doi.org/10.1098/rsta.2020.0450), which reviewed methane emissions quantification by UAVs at that time, we report and reflect here on current progress, capability, and challenges. We will report recent fieldwork (by ourselves and published by others)  to quantify methane emissions from natural and anthropogenic sources and discuss promising new combined survey approaches that could help bridge the gap between snapshot emissions case studies and more long-term (dynamic) monitoring. We shall also discuss future work planned to survey onshore UK anthropogenic sources by the UK NERC MOMENTUM project.
ApRES observations of ice fabric in Greenland: From a climatic transition in the North to a potential historical ice stream remnant in the South
Authors: Rutishauser Anja , Drews Reinhard , Ershadi Reza M. , Oraschewski Falk M. , Scanlan Kirk M. , Karlsson Nanna B. , Martin Carlos , Solgaard Anne M. , Andresen Camilla S. , Ahlstrøm Andreas P.
Published: March 2024

The crystal orientation fabric (COF) of ice sheets, characterized as the net alignment of ice crystals, can contain a record of past ice sheet dynamics and potentially climatic conditions. In turn, the COF significantly influences ice viscosity, thus impacting present-day ice deformation and flow velocities. Due to its dielectric properties, anisotropic COF can be detected with polarimetric radar measurements, including Autonomous phase-sensitive Radio-Echo Sounders (ApRES).Here, we present findings from polarimetric ApRES measurements conducted at Camp Century North-West Greenland, and two sites in Southwest Greenland: Dye-2 and KAN-U. At Camp Century, the ApRES measurements indicate some COF anisotropy throughout the ice column, with a distinct boundary at the depth of the Holocene-Wisconsin ice transition, previously identified in a nearby ice core. We investigate the origin of this boundary in the ApRES data, and whether such signatures can be used to identify glacial-interglacial transitions from polarimetric radar data.At both sites in Southwest Greenland, the signal is strongly attenuated and falls below the noise level beyond 500 m depth, likely due to significant scattering within a heterogeneous firn column. However, Dye-2 exhibits strong COF anisotropy in the uppermost 100-500 m of the ice column, despite the region’s slow ice flow. Conversely, KAN-U displays no evidence of  COF anisotropy. We investigate causes of the peculiar localized anisotropy at Dye-2, hypothesizing it as a residual imprint of a historic fast flowing, far inland-reaching ice stream.
Surface regimes can provide an inherent perspective into interior dynamics
Authors: Henke-Seemann Oliver , Noack Lena
Published: March 2024

Tectonic processes shape the Earth's lithosphere and surface. Deformation, as a result of tectonic forcings, arises mainly in the regions of plate boundaries. A recurring process is the subduction of oceanic lithosphere, which is widely regarded as the main driver of plate tectonics and the recycling of surface material into the mantle. In geodynamic models, the breaking of the strong crust is facilitated by processes that mimic plastic deformation. Most efforts to include plate tectonics self-consistently into mantle convection models, combine Newtonian diffusion creep with a stress-dependent pseudo-plastic rheology, given in the form of a yield criterion. Studies from seismology and geodynamic modelling indicate that cold lithospheric crust can reach the lowermost mantle regions, even the core-mantle-boundary. Additionally, the agglomeration of continental lithosphere (the most extreme variants of which are called supercontinents) inhibits the escape of heat over large surface areas, resulting in an abnormally heated mantle beneath. Therefore, it can be argued, that surface processes exert control on mantle dynamics as a whole, by introducing thermal and compositional heterogeneities.An example of the influence of surface tectonics on the interior can be found in the study of the Earth's geodynamo. Theoretical considerations and numerical models indicate, that the heat flux at the core-mantle boundary partly governs the variability of the geodynamo, and therefore the frequency of geomagnetic reversals and excursions. We run several numerical mantle convection simulations in a 2D-spherical annulus geometry, with a visco-plastic rheology to facilitate surface mobilisation. The models are evaluated with respect to well-known diagnostic values, used to recognise plate-like surface deformation, as well as the thermal structure of the lower mantle. In this, we aim to connect tectonic regimes or continental configurations that arise dynamically at the surface, to evolutionary trends in the mantles thermal structure.
Lagrangian description for the drift of large floating debris in rivers during floods
Authors: Sansen Damien , Archambeau Pierre , Pirotton Michel , Erpicum Sébastien , Dewals Benjamin
Published: March 2024

During floods, the drift of floating debris is a common phenomenon that may exacerbate the flood con-sequences. These objects often have the potential to induce clogging, particularly when they accumulate at bridge piers and obstruct river flow. Accurately predicting such clogging or other interaction with fixed structures is essential for enhancing flood risk assessment and management.To effectively model their effect, the fundamental dynamics of floating objects must be investigated, as well as debris-structures interactions. The latter requires a model for obstacle generation, collision detec-tion and simulation of the influence of collisions on the debris dynamics. Besides, detailed validation against high quality laboratory data is a prerequisite before considering reliable model application to real-world rivers. In this research, improvements have been brought to the Lagrangian modelling of large floating debris colliding with fixed obstacles. A promising approach involves discretizing obstacles into rectangles, for which the mathematical description of the collision process is known. Furthermore, the proposed method reproduces the effect of collisions by adjusting the debris dynamics rather than forcing its trajectory after collision. The debris motion modelled by the developed 2D Lagrangian model leads to plausible trajecto-ries, generally in agreement with experimental data. The model also succeeds in recreating clogging situa-tions. Precise consideration of collision dynamics makes it possible to distinguish between temporary and permanent clogging, depending on certain parameters such as the adopted geometry and the debris size. Extra developments are still necessary for extending these findings to the context of real-world rivers.
Frequency-dependent delay time analysis for Bhutan Himalaya
Authors: Bala Sayan , Dutta Abhisek , Singh Chandrani
Published: March 2024

In this study, we have evaluated the scattering nature of the crust beneath the Bhutan Himalaya, located in the eastern part of the Himalayan arc. We have analysed high-quality waveforms of 566 events having magnitude (ML) below 6, recorded by broadband stations of the GANSSER network operated by the Swiss Seismological Service at ETH Zurich from Jan, 2013 to Nov, 2014. We have investigated the peak delay time (tpd), defined as the time interval between the initial S-wave appearance and the peak amplitude of its envelope, for the frequency ranges of 4–8, 6–12, 8–16 and 12–24 Hz. Initially, we have analysed frequency-dependent nature of tpd at 9 stations (BHE01, BHE09, BHE13, BHN02, BHN06, BHN11, BHW01, BHW10 and BHW16). The observed values of Bfreq, which indicates the frequency dependence of the peak delay time, show mostly low positive values up to 0.3. It shows that tpd is independent of frequency which may be associated with the relative proportions of large as well as small scale heterogeneities present in the medium. At BHE09, Bfreq exhibits a negative value, which might be attributed to the limited sampling of high-frequency signals that capture small portions of the subsurface along their paths. The crust beneath BHE09 experiences reduced scattering, probably due to the absence of a strongly attenuating body in the subsurface. Furthermore, we aim to extend this study for all the stations and to compare the frequency-dependent nature of T5%-75% (time interval between 5% and 75% of the total integrated power value) and the tpd for the study region.
Differences in the uptake of biogenic volatile organic compounds (BVOCs) between habitat types and peat layers in boreal peatlands
Authors: Korrensalo Aino , Davie-Martin Cleo , Männistö Elisa , Blande James , Rinnan Riikka
Published: March 2024

Biogenic volatile organic compounds (BVOCs) released by boreal vegetation have a net cooling impact on climate, both in the boreal and Arctic regions. While boreal forests play a major role in this process, the release and uptake of BVOCs in peatlands is poorly understood, even though they cover up to 28% of the boreal region. Furthermore, soil BVOC sinks and sources are an understudied component of the boreal BVOC budget. Recently, microbial uptake of BVOCs has been found to regulate BVOC release from the soil into the atmosphere. In peatlands, methane emissions from the peat are known to be controlled by microbial oxidation within the living mosses, but it is unknown whether similar uptake occurs with BVOCs.Our aim was to quantify the release and uptake of BVOCs across different boreal peatland habitats. We collected peat samples, including the living moss layer, from four peatland habitats varying in fertility, wetness, and vegetation composition (bog hollow, bog hummock, fen, bog peat). The samples were split into the living moss layer, as well as the oxic and anoxic peat layers, above and below the water table, respectively. First, we investigated the potential uptake of peat-derived BVOCs in the living moss layer by incubating the peat and moss layers in glass jars both separately and together with other layers from the same habitat. Next, we quantified the uptake of four specific compounds by introducing 13C-labeled BVOCs into jars containing peat or moss layers. The magnitude and compound composition of BVOCs was measured with proton transfer reaction–time of flight–mass spectrometry (PTR-TOF-MS).Contrary to our expectations, BVOC uptake of peat-derived compounds was observed in the living moss layer, as well as in the oxic and anoxic peat layers. The most important layer for BVOC release and uptake varied between the peatland habitats. For example, the number of released compounds and the total BVOC emissions were largest for anoxic peat in the fen, while it was the living mosses in the bog hollow. Anoxic bog peat had the largest BVOC uptake of all of the habitats and layers. BVOC uptake varied between the studied compounds; while ethanol was taken up by all layers in every habitat, we observed no uptake of acetic acid. Acetone was mostly consumed in the peat layers, while acetaldehyde uptake occurred in bog hummock and fen habitats, regardless of the layer. According to our results, BVOC emissions from boreal peatland soil into the atmosphere are a net outcome of production and consumption both in the peat and moss layers. As these patterns vary even within habitats of the same site, changes in vegetation have the potential to modify BVOC fluxes in boreal peatlands.
Ambient noise characteristics of the Chung-Liao Tunnel area in National Highway No. 3
Authors: Lin Ting-Yu , Chen Ying-Nien , Rau Ruey-Juin
Published: March 2024

    Under a uniform scattered wave field, the continuous recording of Cross-Correlation Functions (CCF) between monitoring stations can be approximated by the Green's function between these stations. Therefore, passive seismic noise interference techniques can be employed to monitor changes in the structural properties of the Earth. The Zhongliao Tunnel in the southern section of National Highway No. 3 cuts through two significant active structures, the chishan Fault and the Chekualin Fault. In order to investigate the impact of fault activity on the tunnel's structure, our laboratory deployed a dense array composed of 33 portable seismometers around the Zhongliao Tunnel starting in 2020, conducting seismic observations for an entire year. With an average station spacing of less than 1 kilometer in this dense array, there is a chance to obtain high-frequency Green's functions, enabling monitoring of shallow structures. However, non-uniform distribution of noise energy may cause differences between interference waveforms and real Green's functions. Therefore, this study focuses on the spatiotemporal characteristics of background high-frequency signals, aiming to clarify their sources as a foundation for future research. Through Power Spectral Density (PSD) analysis of the stations, we observed energy drops at night in the range of 1-12Hz , possibly attributed to body waves or surface waves generated by vehicular traffic on the highway. To identify the distribution of noise sources, the research area was subdivided into 121 grid points as potential signal sources. Surface wave and body wave energy decay characteristics were fitted separately to the spatial distribution of that energy, revealing that the predominant seismic mode is surface waves, and the most likely noise source is located at the tunnel entrance, unevenly distributed on the highway. Furthermore, an analysis of the amplitude asymmetry in the cross-correlation functions between stations indicated that the high-frequency signals originate from the tunnel entrance. As there are no specific conditions near the tunnel entrance that can autonomously generate high-frequency signals, we speculate that these signals are still caused by vehicles on the highway. When seismic waves propagate around the tunnel, the velocity structure causes energy to focus at the tunnel entrance, radiating outward. In the future, we will use Eikonal tomography to analyze the velocity structure beneath the array and conduct waveform simulations to test this hypothesis.
Constraining glacial ocean carbon cycle – A multi-model study
Authors: Liu Bo , Ilyina Tatiana , Brovkin Victor , Willeit Matteo , Ye Ying , Völker Christoph , Köhler Peter , Heinemann Malte , Kurahashi-Nakamura Takasumi , Paul André , Schulz Michael , Merkel Ute , Lhardy Fanny
Published: March 2024

The ocean contained a larger carbon content at the Last Glacial Maximum (LGM, ~21kyr before present) compared to the late Holocene, making a considerable contribution to the deglacial atmospheric CO2 rise of about 90 ppm. Yet, there’s no consensus on the mechanisms controlling the glacial-interglacial changes in oceanic carbon storage due to uncertainties and sparseness of proxy data. Numerical simulations have been widely used to quantify the impact of key factors, such as changes in sea surface temperatures, ocean circulation and biological production, on glacial ocean carbon sequestration. However, the robustness of these findings is subject to further testing due to the differences in process representation, parameterization, model architecture, or external forcing employed by models.Towards further constraining the LGM ocean carbon cycle, we conducted a multi-model comparison with three comprehensive Earth System Models (Alfred Wegener Institute Earth System Model, AWI-ESM; Community Earth System Model, CESM; Max Planck Institute Earth System Model, MPI-ESM) and one Earth system Model of Intermediate Complexity (CLIMBER-X). We carried out three coordinated experiments with each model: 1) PI (the pre-industrial control simulation), 2) LGM-PMIP (following PMIP4 LGM protocol) and 3) LGM-LowCO2 (as LGM-PMIP, but with boosted alkalinity inventory to lower atmospheric CO2 to about 190 ppm. All experiments were conducted with the prognostic CO2 for the carbon cycle, considering only the atmosphere and ocean reservoirs, and prescribed CO2 for radiative forcing.All models consistently show that applying the PMIP4 LGM boundary conditions alone leads to only a 5-40 ppm decrease in atmospheric CO2. Globally, the glacial CO2 drawdown in LGM-PMIP is mainly controlled by the enhanced solubility pump. The spatial distribution of the increased glacial DIC depends on the ocean circulation state in each model. In MPI-ESM and CLIMBER-X, the shallower and weaker AMOC facilitates carbon storage in the deep Atlantic. An LGM atmospheric CO2 of 190 ppm can be achieved by boosting alkalinity by 5-8% in scenario LGM-LowCO2. In all models, boosting LGM alkalinity inventory increases DIC in the bottom water. However, comparison to proxy data reveals that the models lack respired carbon, particularly in the deep Pacific. This suggests a need to enhance the glacial biological carbon pump in the models.
Objective Probability of Detection Functions for High-Resolution Detection of Point-Source Methane Emissions from Space 
Authors: Conrad Bradley , Johnson Matthew
Published: March 2024

Reliable detection and localization of methane point sources is critical to rapidly mitigating methane emissions and avoiding the worst-case projected scenarios of climate change.  With increasingly widespread coverage and short revisit periods, satellite-based detection of methane point-sources is well-suited to identifying the largest emitters for mitigation.  To fully understand how satellite-based detection fits within multi-scale monitoring, reporting, and verification (MRV) frameworks, however, it is crucial to robustly characterize the probability of detection (POD) of active and planned instruments.  This is especially true in the upstream oil and gas sector, where measurements show highly right-skewed emissions size distributions that raise doubt on the portion of sector-wide emissions detectable from space.  While there is no shortage of statements regarding vaguely defined limits of detection (LODs) or PODs within the literature and press releases, these are often opaquely derived and, crucially, are not placed in the context of false positive rates.  Moreover, LODs based on single-blind controlled release testing are inherently problematic as prior knowledge of controlled releases precludes objective interpretation of detectability.  With ongoing efforts to improve detection sensitivities and quantification accuracies, a standardized framework for objective and transparent PODs is needed to ensure satellite-based instruments are leveraged to their full capacity.
Here, we present an innovative framework to objectively quantify detection probabilities for satellite observations of methane point sources.  This generalized framework is independent of satellite resolution and precision in addition to the underlying – and potentially proprietary – method for plume segmentation.  Based in frequentist hypothesis testing, the new framework provides a POD function for satellite-specific characteristics, given a permissible false positive rate.  This latter point is critical when considering satellite techniques for use in MRV as well as leak detection and repair (LDAR) programs where nuisance detections (i.e., false positives) can render satellite approaches cost prohibitive.  We apply this new framework to methane-detecting satellite instruments in two scenarios: 1) idealized conditions of spatially uncorrelated image noise and 2) realistic conditions with spatially correlated noise derived from publicly available image data.  These analyses identify best-case PODs as a function of imagery resolution and precision and show the detrimental effect of spatially correlated noise on automated plume segmentation.  