bluuebunny/crossref_metadata_2025 huggingface dataset:
Transmission of foreshock waves through the Earth’s magnetosheath
Authors: Turc Lucile , Roberts Owen , Verscharen Daniel , Dimmock Andrew , Kajdic Primoz , Palmroth Minna , Pfau-Kempf Yann , Johlander Andreas , Dubart Maxime , Kilpua Emilia , Soucek Jan , Takahashi Kazue , Takahashi Naoko , Battarbee Markus , Ganse Urs
Published: March 2022

The foreshock, extending upstream of the quasi-parallel shock and populated with shock-reflected particles, is home to intense wave activity in the ultra-low frequency range. The most commonly observed of these waves are the "30-second" waves, fast magnetosonic waves propagating sunward in the plasma rest frame, but carried earthward by the faster solar wind flow. These waves are thought to be the main source of Pc3 magnetic pulsations (10 – 45 s periods) in the dayside magnetosphere, but how the waves can transmit through the bow shock and across the magnetosheath remains unclear. Global hybrid-Vlasov simulations performed with the Vlasiator model provide us with the global view of foreshock wave transmission across near-Earth space. We find that the foreshock waves act as fast-mode pulses hammering periodically the shock, which impulsively sends perturbations in the downstream at the fast-mode speed. These fast-mode disturbances propagate in the magnetosheath all the way to the magnetopause, where they can further transmit into the dayside magnetosphere. The wave propagation across the bow shock appears to be much more complex than the simple "direct transmission" of the foreshock waves which was inferred in early studies. This is due to the complex two-way interactions between the waves and the shock, including shock reformation. We compare our global simulation results with local 1D simulations, and we show that the wave signatures in the downstream strongly depend on the global properties of the shock-magnetosheath system. This emphasises the importance of carrying out global simulations in this context.
Monitoring a plant’s reaction to drought stress with hyperspectral remote sensing and sun-induced chlorophyll fluorescence
Authors: De Cannière simon , Jonard François
Published: March 2022

Water availability is a major constraint for crop production worldwide. Remote sensing provides an ideal mean to monitor vegetation status from the canopy to the ecosystem scale. Classical approaches have mainly used the reduced vegetation development as a stress indicator. This research discusses short-term reactions on a plant to drought stress as well as their corresponding effects on different hyperspectral remote sensing metrics.

As a first effect, a reduction in the plant water content results in a drop in the leaf turgor, which changes the leaf orientation. This effect changes the canopy structure, changing the near-infrared reflectance.

Second, a water shortage in a plant induces stomatal closure, which limits the gas exchange. This reduces the amount of CO2 that the photosynthetic apparatus can assimilate, causing an imbalance between the energy demanded by the CO2 assimilation part and the energy provided by the photosynthetic light reactions. As a consequence, an alternative electron sink is needed at the light reactions side. This is provided for by a series of mechanisms collectively known as non-photochemical quenching (NPQ). The increase in NPQ leads to a change in the hyperspectral photochemical index (PRI) and to a change in the sun-induced chlorophyll fluorescence (SIF) emission. The latter consists of the radiation that is re-emitted by a chlorophyll molecule.

To evaluate the effect of a drought stress on these remote sensing metrics, the hyperspectral reflectance and the SIF emission were measured over a mustard and a lettuce canopy. At the same time, the soil moisture and weather conditions were monitored. The PRI shows a clear diurnal pattern, in which the PRI is anticorrelated with the photosynthetically active radiation (PAR). The pattern is more expressed for stressed days. The canopy structure’s reaction to drought stress is very species-specific, as this reaction is affected by the presence of woody material in the canopy. The SIF reaction only becomes clear after it has been normalized for the PAR and for the canopy structure. The link between SIF and PAR depends on the plant stress status. We argue that the combination of these three factors (PRI, SIF and reflectance) provide solid information on the degree of water limitation in the plant.
Understanding drivers of inter-model differences in tropical free-tropospheric humidity in global storm-resolving models 
Authors: Lang Theresa , Naumann Ann Kristin , Schmidt Hauke , Buehler Stefan A.
Published: March 2022

The dry subsidence regions of the tropics and subtropics play an important role in setting the Earth’s clear-sky climate sensitivity, as the clear-sky feedback in these regions is particularly sensitive to both the baseline relative humidity (RH) and small RH changes under warming. Therefore, it is crucial that climate models reliably simulate the RH and its response to warming in these regions. However, considerable inter-model differences in RH remain, also in global storm-resolving models, the newest generation of climate models with horizontal grid spacings sufficient to explicitly resolve deep convection. The goal of this study is to identify potential causes for these inter-model differences and understand the mechanisms behind it. For this we examine the effect of changes in different model parameters – including microphysical parameters and vertical grid spacing – on tropical free-tropospheric humidity in a global storm-resolving model, focusing on the dry subsidence regions. Back-trajectory calculations allow us to determine the characteristics of the last saturation points for dry tropical air masses as well as the magnitude of moisture sources and sinks during subsequent advection, and how both change in the sensitivity experiments. The trajectory analysis confirms that moisture gains and losses during advection play a secondary role in setting the RH distribution in tropical dry zones in the model, as suggested by earlier studies based on coarser models. This leaves changes in the points of last saturation, which are determined by the circulation and the temperature field, as the more likely driver of RH changes. Preliminary results from the sensitivity experiments indicate that particularly changes in the vertical grid spacing of the model can affect the RH in tropical subsidence regions. These RH changes are explained by changes in the temperature of the main outflow regions of deep convection in the upper troposphere, where most last saturation points are located. These results highlight the importance of circulation and temperature differences across global storm-resolving models in driving inter-model differences in RH.
An integrated catchment modelling for assessment of water quality and its effect on aquatic ecology
Authors: Rankinen Katri , Cano-Bernal José , Vähä Juha-Pekka
Published: March 2022

The catchment is the appropriate scale to observe and quantify processes related to the water cycle and water quality. In the Karjaanjoki river basin (located in southern Finland) we aim to sustainable agricultural production that does not harm water ecosystems. Indicator species are trout and river pearl mussels. This is one of the few rivers that still has a natural pearl mussel population. Their living conditions have deteriorated, and the population is aging. We used mathematical models to assess the threats of human activity in the catchment area that can influence water quality and thus living conditions of these species. We estimated the change in living conditions from long water quality time series. We created an integrated, process-based model chain (Persist and INCA) to assess different loading scenarios from agricultural practices. Our results show that the agri-environmental measures are sufficient to maintain the current water quality, but more effective measures are needed to improve it. Climate change in particular is putting additional pressure on ecosystems.
PHUSICOS platform, dedicated to Nature-Based Solutions for Risk Reduction and Environmental Issues in Hilly and Mountainous Lands : presentation and qualitative NBS assessment
Authors: Bernardie Séverine , Baills Audrey , Garçin Manuel
Published: March 2022

PHUSICOS platform aims at gathering nature-based solutions (NBS) relevant to reduce hydro-geological risks in mountain landscapes. The platform can be accessed directly through a web portal. It is based on an Open Source CMS website, including a filter to store documents and a map server to bring ergonomic and powerful access.

To design the platform, an in-depth review of 11 existing platforms has been performed.  Furthermore, a list of metadata has been proposed to structure the information. These metadata have provided the baseline for database. The PHUSICOS platform currently references 176 NBS cases and 83 documents of interest (review articles, assessment papers…). It is continuously enriched through the contribution of NBS community.

For that, a questionnaire based on relevant data, necessary for the definition and identification of the NBS (metadata, to be used for searching the NBSs within the platform) has been defined to enter new entries. A preliminary analysis of the cases has been realized. To characterize and analyse the current 152 solutions, we have worked on the following four categories: The nature of impacted ecosystems, The hazard(s) concerned, The other challenges treated by the NBS, The type of exposed assets.

The platform also proposes a qualitative assessment of the NBSs collected according to 15 criteria related with five ambits: disaster risk reduction, technical and economical feasibility, environment, society, and local economy. The criteria level is sufficiently general to be analysed for the entire PHUSICOS platform NBSs whatever the type of work, the realized approaches, the problematic or the spatial or temporal scale.

The structure of the platform and a first analysis of the qualitative NBS assessment are presented in this work.
Ambient noise tomography of post-subduction setting in northern Borneo enhanced with machine learning
Authors: Fone Joseph , Pilia Simone , Rawlinson Nicholas , Hou Song
Published: March 2022

Given that subduction is an important driver of plate tectonics on Earth, it is notable that the effects of subduction termination are often complex and poorly understood. Northern Borneo is a prime example of a post-subduction environment, where two subduction zones have terminated within the last 20 Ma. The region however has seen very few seismic studies likely due to the low levels of seismicity in the region compared to the rest of Southeast Asia and due to the challenging deployment environment. The goal of the northern Borneo Orogeny Seismic Survey (nBOSS) network, which operated between 2018 and 2020 and consisted of 47 broadband instruments, was to provide constraints and answer first order questions about the structure of the lithosphere and asthenosphere in this post-subduction setting. Waveform data from this network were supplemented with data recorded by 33 permanent instruments operated by the Malaysian meteorological authority, METMalaysia. In this study we produce the first model of the crustal shear wave velocity structure under northern Borneo using surface wave ambient noise tomography to try and better understand the effects of subduction termination on the crust and to better understand the present day structure of the crust in this region which has not been imaged in this way before. We use a trans-dimensional tomography to produce variable resolution 2D Rayleigh wave phase velocity maps in the period range 2-30 seconds sampled every 2 seconds. Then to produce the final 3D shear wave velocity model a series of 1D inversions were used in combination with a neural network that is trained to find a generalised solution to the 1D inverse problem for this data set. This helps to prevent artefacts forming in the final model as a result of there being no lateral correlations in the 1D inversions by providing the more region specific trained neural network to perform the bulk of the 1D inversions. The result is a model that shows a detailed 3D shear wave velocity structure of the crust that matches expected velocity anomalies from known geological features. This includes the large sedimentary basins in the region, which are revealed as large slow velocity anomalies. Our new model agrees with results from other methods used to study this region, including receiver functions and surface wave tomography.
Multi-hazard risk analysis based on Bayesian networks for geothermal resources exploitation
Authors: Trevlopoulos Konstantinos , Jalayer Fatemeh
Published: March 2022

The injection of fluids into the subsoil, which takes place during the exploitation of geothermal resources, may affect the quality of the air and the water in the subsoil, and it may be the source of induced earthquakes. A decision support system based on multi-hazard risk (seismic and environmental) analysis can help control the exploitation and keep risk in tolerable levels. In this work, we describe a traffic light system of this type applied in the case of the Basel geothermal site. This system relies on a Bayesian network to compute the probability of the red-amber-green lights for a given distribution of the rate of injection of fluids. The network has a single parent node for the injection rate. Here, we used data on European Plate Observing System Thematic Core Service for Anthropogenic Hazards for the injection rate, the air quality, and the water quality to characterize the links between the parent node and the nodes for air and water quality. The link between the injection rate and the node for the ground motion intensity measure was characterized based on an event-based probabilistic seismic hazard analysis using stochastic earthquake catalogs generated by a physics-based model. Subsequently, arbitrary thresholds of the peak ground velocity, steam production rate, and proppant injection rate, were selected for the amber and red lights to characterize the links between the corresponding nodes and their descendant node, i.e., the traffic light. The probabilities of the traffic lights were computed, and the probability of the red light was disaggregated to identify its driver in different scenarios.
The Potential of Green Roofs in London
Authors: Simpson Charles , Brousse Oscar , Heaviside Clare
Published: March 2022

Concerns about the cooling requirements of buildings and negative health effects from heat exposure are increasing with the public’s awareness of climate change. Green roofs have been considered a powerful mitigative and/or adaptive tool to reduce negative impacts of heat. In fact, they can reduce summer indoor-temperatures, as evapotranspiration increases latent heat-flux from a building’s roof. The cooling effect seems to be small on outdoor air temperatures, according to past studies, although green roofs have other benefits in terms of biodiversity, carbon storage, improved building thermal performance and flood management. As the need for sustainable and climate resilient building designs becomes the norm in cities, it is important to assess the status of green roofs coverage and explore potential for future implementation. Accurate information on the prevalence and characteristics of existing green roofs is indeed required to estimate any effect of green roofs on outdoor and indoor temperatures, although this information is often lacking.

Surveying Greater London, we identified existing green roofs and estimated the potential for buildings to be retrofitted with green roofs. Existing green roofs were identified using automated classification of aerial and satellite imagery. Potential for retrofit is assessed using a geospatial database of building characteristics, together with a digital surface model.

The current total green roof area in Greater London is around 1.5 square kilometres (around 0.5% of built area). We estimate that retrofitting existing suitable buildings could add another 3 square kilometres, corresponding to around 2% to the built area in Central London, and around 1% outside Central London. Existing green roofs appear mainly on new buildings rather than being retrofitted, and mainly occur on office and commercial buildings in Central London and residential blocks in redeveloped areas. Potential for retrofit may be highest in the borough of Tower Hamlets, largely on residential blocks with flat roofs.

 This work has direct relevance to sustainable planning policy, especially the London Plan Overheating and cooling policy, and will enable modelling of the building-stock and city-scale effects of green roofs.
Evapotranspiration in urban stormwater planter boxes: A study of eight lysimeters under temperate climate
Authors: Ouédraogo Ahmeda Assann , Berthier Emmanuel , Gromaire Marie-Christine
Published: March 2022

Sustainable urban drainage systems aim to promote the infiltration and the evapotranspiration (ET) processes rather than the runoff. In this study, the ET in 1 m3 pilot stormwater planters were studied from eight lysimeters monitored for three years in a dense urban environment in Paris (France). In each lysimeter, a piezometer, four weighing cells and a tipping bucket are used to measure respectively the water level in the internal water storage (IWS), the mass change of the whole lysimeter and the underdrain flow. Meteorological data, precipitation and water level are also collected respectively from the weather station, the rain gauge and the pan evaporimeter installed next to the lysimeters.

Daily ET was calculated for each lysimeter based on a mass balance approach. The uncertainties related to the daily ET estimates were assessed at ± 0.42 to 0.58 mm depending to the lysimeter and according to the uncertainty propagation law. Results showed that for these lysimeters, with an impluvium equal to 4 times the vegetated surface, ET is the major term in water budget (57 to 90% of the cumulated water inputs) with maximum daily values reaching 8 mm/d. In addition, the observations showed that the major determinants of ET are the existence or not of an internal water storage (IWS) and the atmospheric factors (global radiation, air temperature and in a minor extent air humidity). The type of vegetation is a secondary determinant, with little difference between the herbaceous and the shrub configurations, maximum ET for spontaneous vegetation and minimal values when the vegetation was regularly removed. Shading of lysimeters by surroundings buildings is also an important factor and leads to lower values. Finally, ET with an IWS is higher than reference values tested (evaporimeter, FAO-56, and local Météo-France equations), except for regional Météo-France formula which overestimates ET of lysimeters and especially in summer. For future studies, it is expected to include some aspects in the experiments for explicitly addressing shading effects and vegetation evolution.
A comparison of supraglacial lake characteristics and drainage dynamics in Southwest Greenland between an extreme high, and an extreme low, melt season
Authors: Glen Emily , Banwell Alison , Maddalena Jennifer , Leeson Amber , Corr Diarmuid , McMillan Mal
Published: March 2022

Mass loss from the Greenland Ice Sheet (GrIS) is predicted to contribute up to 10 cm to global sea level rise by 2100. This mass loss is due to both increased meltwater production and therefore increased runoff, which is occurring at higher elevations on the ice sheet, as well as ice-dynamical feedback processes such as supraglacial lakes (SGLs) draining rapidly to the ice sheet bed; enhancing basal sliding. Therefore, the specific processes through which SGLs drain has an important control on mass loss from the GrIS. This highlights the need for high-resolution, integrated datasets that provide a comprehensive view of supraglacial hydrological networks, including SGL drainage events, on the GrIS.

Here, we compare SGL characteristics and drainage dynamics of a southwestern sector of the GrIS throughout both an extreme high melt season (2019) and an extreme low melt season (2018). SGLs are delineated throughout both the summer seasons from Sentinel-2 and Landsat 8 optical imagery using threshold-based normalized difference water index (NDWI) methods followed by extensive manual enhancement to increase accuracy. SGL depths are calculated using a radiative transfer model and individual lake volume is determined. The resulting meltwater maps have a spatial resolution of 10 to 30 m and have a temporal resolution of weekly to fortnightly. The following SGL characteristics are determined: i) area; ii) volume; iii) elevation; iv) ice surface slope; and v) solidity. SGL drainage dynamics are analysed by tracking lakes through the duration of each melt season and determining if a lake drains rapidly by hydrofracture, slowly drains via channel incision and overflow, or does not drain and instead refreezes at the end of the melt season. To do this, we use the Fully Automated supraglacial lake area and volume tracking at enhanced resolution (FASTER) algorithm, developed by Williamson et al. (2018).

As temperatures continue to increase, the frequency of high melt years like 2019 will also increase. As such, it ever more important to understand supraglacial meltwater characteristics and dynamics in high melt seasons, especially compared to years with limited melt.
Convection-permitting climate models Offer More Certain Extreme Rainfall Projections
Authors: Fosser Giorgia , Adinolfi Marianna , Ban Nikolina , Belušić Danijel , Caillaud Cécile , Cardoso Rita M. , Coppola Erika , Demory Marie-Estelle , De Vries Hylke , Dobler Andreas , Feldmann Hendrik , Gaetani Marco , Görgen Klaus , Kendon Elizabeth J. , Lenderink Geert , Pichelli Emanuela , Schär Christoph , Soares Pedro M. M. , Somot Samuel , Tölle Merja H.
Published: March 2022

Compared to standard regional climate models (RCMs), convection-permitting models (CPMs) provide an improved representation of sub-daily precipitation statistics and extremes thanks mainly to the possibility to switch off the deep convection parameterisation, a known source of model error and uncertainties. The more realistic representation of local processes in CPMs leads to a greater confidence in their projections of future changes in short-duration precipitation extremes.

The quantification of uncertainties on future changes at this resolution has been barely touched. Using the first-ever ensemble of CPMs run within the UK Climate Projections project, Fosser et al. (2020) found that the climate change signal for extreme summer precipitation may converge in CPMs in contrast to RCMs, thanks to a more realistic representation of the local storm dynamics.

Here we use the first multi-model CPMs ensemble over the greater Alpine region, run under the auspices of the World Climate Research Programme’s (WCRP) Coordinated Regional Downscaling Experiment Flagship Pilot Study on Convective phenomena at high resolution over Europe and the Mediterranean (Coppola et al. 2020). Several statistics are used to determine the uncertainties in the climate change signal trying to disentangle model uncertainties from natural variability. We found that the contribution of model to the total uncertainties is substantially reduced in CPMs compared to the driving models in summer. This is likely linked to the removal of the uncertainties associated with the convective parameterisation and to a more realistic representation of convective and local dynamical processes in the CPMs.

 

Fosser G, Kendon EJ, Stephenson D, Tucker S (2020) Convection‐Permitting Models Offer Promise of More Certain Extreme Rainfall Projections. Geophys Res Lett 47:0–2. doi: 10.1029/2020GL088151

Coppola, E., Sobolowski, S., Pichelli, E. et al.A first-of-its-kind multi-model convection permitting ensemble for investigating convective phenomena over Europe and the Mediterranean. Clim Dyn55, 3–34 (2020). https://doi.org/10.1007/s00382-018-4521-8
Corona structures as a window into volcano-tectonic activity on Venus: key insights and ways forward
Authors: Gülcher Anna , Gerya Taras , Montési Laurent
Published: March 2022

Our neighbouring planet Venus holds key insights into terrestrial planet evolution. At present, there is no mosaic of mobile tectonic plates on the planet, yet Venus’ surface is scarred with many tectonic and volcanic structures. Surface deformation seems to be related to regional-scale tectonic deformation and/or mantle upwellings, but it remains questionable exactly when, and how, Venus is resurfacing. “Coronae” are ~circular crown-like structures with traces of tectonic and volcanic activity. They are commonly proposed to be surface manifestations of mantle plume upwellings and/or magmatism, and may therefore provide fundamental insights to Venus’ interior dynamics through time. The exact processes underlying their development and the reasons for their diverse morphologies have been widely debated in the past, with several key outcomes for the Venus scientific community. 

In this presentation, I focus on our recent 3D numerical studyof plume-induced corona formation [1] and discuss what insights this study gives on the thermal evolution of Venus, as well as its present-day geological activity. The modelled corona morphologies are strongly on the lithospheric structure and the underlying dynamic processes at play. By a detailed comparison the modeling results with observed corona features (data from NASA’s Magellan mission), widespread plume activity on Venus was identified.  Moreover, I present prompting new results on the gravitational signatures of these modelled corona structures, and discuss whether we can distinguish between different stages of corona evolution in the gravity field. These outcomes may be important for future radio science experiments aboard ESA’s EnVision orbiter.

Finally, I’ll touch upon several key directions for future research on these enigmatic coronae structures, which are relevant in light of the upcoming ‘Decade(s) of Venus Science’. While I mainly formulate these key questions form a geodynamical point-of-view, I invite scientists from all disciplines of the Geo- and Planetary sciences to join the discussion on how these unique coronae can provide key information on the evolution of the interior and surface of Earth’s twin planet.

[1] Gülcher, A.J.P., Gerya, T.V., Montési, L.G.J., and Munch, J., (2020). Corona structures driven by plume–lithosphere interactions and evidence for ongoing plume activity on Venus. Nature Geoscience, 13, 547–554. 
Comparison of deep learning methods for colorizing historical aerial imagery
Authors: Tanaka Shimon , Miyamoto Hitoshi , Ishii Ryusei , Carbonneau Patrice
Published: March 2022

Historical aerial imagery dating back to the mid-twentieth century offers high potential to distinguish anthropogenic impacts from natural causes of environmental change and reanalyze the long-term surface evolution from local to regional scales. However, the older portion of the imagery is often acquired in panchromatic grayscale thus making image classification a very challenging task.  This research aims to compare deep learning image colorisation methods, namely, , the Neural Style Transfer (NST) and the Cycle Generative Adversarial Network (CycleGAN), for colorizing archival images of Japanese river basins for land cover analysis. Historical monochrome images were examined with `4096 x 4096` pixels of three river basins, i.e., the Kurobe, Tenryu, and Chikugo Rivers. In the NST method, we used the transfer learning model with optimal hyperparameters that had already been fine-tuned for the river basin colorization of the archival river images (Ishii et al., 2021). As for the CycleGAN method, we trained the CycleGAN with 8000 image tiles of `256 x256` pixels to obtain the optimal hyperparameters for the river basin colorization. The image tiles used in training consisted of 10 land-use types, including paddy fields, agricultural lands, forests, wastelands, cities and villages, transportation land, rivers, lakes, coastal areas, and so forth. The training result of the CycleGAN reached an optimal model in which the root mean square error (RMSE) of colorization was 18.3 in 8-bit RGB color resolution with optimal hyperparameters of the dropout ratio (0.4), cycle consistency loss (10), and identity mapping loss (0.5). Colorization comparison of the two-deep learning methods gave us the following three findings. (i) CycleGAN requires much less training effort than the NST because the CycleGAN used an unsupervised learning algorithm. CycleGAN used 8000 images without labelling for training while the NST used 60k with labelling in transfer learning. (ii) The colorization quality of the two methods was basically the same in the evaluation stage; RMSEs in CycleGAN were 15.4 for Kurobe, 13.7 for Tenryu and 18.7 for Chikugo, while RMSE in NST were 9.9 for Kurobe, 15.8 for Tenryu, and 14.2 for Chikugo, respectively. (iii) The CycleGAN indicated much higher performance on the colorization of dull surfaces without any textual features, such as the river course in Tenryu River, than the NST. In future research work, colorized imagery by both the NST and CycleGAN will be further used for land cover classification with AI technology to investigate its role in image recognition. [Reference]: Ishii, R. et al.(2021) Colorization of archival aerial imagery using deep learning, EGU General Assembly 2021, EGU21-11925, https://doi.org/10.5194/egusphere-egu21-11925.
Temporal Disconnect of Seasonal Plant Nutrient Demand and Thaw Depth implies an Increasing Source of N2O in High-Latitude Permafrost Ecosystems 
Authors: Lacroix Fabrice , Zaehle Sönke , Caldararu Silvia , Schaller Jörg , Stimmler Peter , Goeckede Mathias
Published: March 2022

Thawing and degradation of permafrost in high latitudes could have an important effect on the Earth’s greenhouse budget. Implications of increased nutrient availability resulting from thawing of nutrient-rich permafrost, however, remain poorly assessed, despite nutrients having being identified as a strong present-day constraint for plant growth and microbial activity in the high latitudes. In our pan-arctic scale study, we extend the terrestrial ecosystem model QUINCY, which already couples C-N-P cycles in soil and vegetation, for a better representation of high-latitude processes. With this model version, we perform historical simulations at the site-level over 1960-2019. Averaged over high-latitude grassland sites, our simulations show an average increase in the soil active layer depth of 0.1m and an increased gradient of biologically-available P and N at the permafrost front. In spite of this, only 11 % of the simulated increase over the GPP (+34%) is a result of increased nutrient supply from permafrost organic matter degradation. This owes to spatial and temporal decoupling of the simulated vegetation growth peak (mid-to-late-July), the time period where plant nutrient demand is the highest, and the maximum of the seasonal thaw depth (mid-to-late August), the time period in which nutrients in the deep active layer would potentially be available for uptake. As a result, increased nitrogen at the permafrost front and alternating aerobic-anaerobic conditions contribute to enhancing nitrification and denitrification in the model, causing a weak source of N2O to the atmosphere of 0.7 kg N ha-1 yr-1, which undergoes a considerable upward trend of up to 0.1 kg N ha-1 decade-1, locally,over the simulation time frame. Considering the vastness of the permafrost domain, and that N2O emissions from these regions have been largely neglected in the past, these results imply that high latitudes could be a considerable and growing contributor to the global atmospheric N2O budget.
Sensitivity of the Eurasian Ice Sheet: Improved model-data comparison routines
Authors: Archer Rosie , Ely Jeremy , Heaton Timothy , Clark Chris
Published: March 2022

At the Last Glacial Maximum, the Eurasian Ice Sheet (EIS) was one of the largest ice masses, reaching an area of 5.5 Mkm2 at its maximum. Recent advances in numerical ice sheet modelling hold significant promise for improving our understanding of ice sheet dynamics, but remain limited by the significant uncertainty as to the appropriate values for the various model input parameters. The EIS left behind a rich library of observational evidence, in the form of glacial landforms and sediments. Integrating this evidence with numerical ice sheet models allows inference on these key model parameters, leading to a better understanding of the behaviour of the EIS and a framework for advancing numerical ice sheet models. To quantify how successfully a particular model run matches the available data, model-data comparison tools are required. Here, we model the EIS using the Parallel Ice Sheet Model (PISM), a hybrid shallow-ice shallow shelf ice sheet model. We perform sensitivity analyses to reveal the most important parameters controlling the evolution of our modelled EIS. Results from this analysis allow us to reduce the parameter space required for a future ensemble experiment. This ensemble experiment will utilise novel model-data comparison tools which compare ice-free timings to geochronological evidence and modelled flow directions with drumlins. Unlike previous model-data comparison routines, our tools provide a more nuanced, and probabilistic, assessment of fit than a simple pass-fail. This offers significant benefits for future parameter selection.
Estimation of the NASA Mars2020 Perseverance rover path through Visual Odometry
Authors: Andolfo Simone , Petricca Flavio , Genova Antonio
Published: March 2022

The future space exploration missions will require autonomous robotic systems capable to safely move across the operational environment and reach sites of scientific interest with limited commands from the ground operators.

The NASA Mars2020 Perseverance rover is the most advanced robotic vehicle ever sent on the planet Mars and is currently exploring the Jezero crater searching for signs of ancient life and investigating the geological history of the planet. The increased computational resources of the Perseverance’s onboard computer enable the navigation software to continuously adjust the path, by processing visual inputs through the navigation cameras. The stereo images with the left and right rover cameras are analyzed to build local 3D maps of the surrounding terrain to identify hazardous areas (e.g., steep slopes) that could affect the rover’s safety.

We use Visual Odometry (VO) methods to accurately update the rover’s position and attitude (i.e., pose), by detecting and tracking the image-locations of landmarks (e.g., the sharp edge of a rock) through successive stereo pairs. VO is a fundamental technique to enhance the localization accuracies of wheeled vehicles in planetary environments where Global Navigation Satellite Systems (GNSS) are not available.

We present here the reconstructed position and attitude of the Perseverance rover that we retrieved by processing images acquired by the navigation cameras during sols 65, 66, 72, and 120. 3D-to-3D algorithms were applied accounting for the nonlinear optical effects that affect the raw images. The estimated rover’s orientation is fully in line with the accurate measurements provided by the onboard Inertial Measurement Units (IMUs). The displacements between the telemetered and the reconstructed rover’s location suggest errors in the WO measurements, which are compensated by our VO estimate.
Bayesian inversion of shear wave velocity profile based on dispersion curve 
Authors: Wang Xuanhao , Cao Zijun , Du Wenqi
Published: March 2022

Dispersion curve inversion is a key step of analyzing data from multichannel surface wave method (MASW) for investigating the shear wave velocity-depth (vs-h) profile. The profile is usually simplified to be a stratification model consisting of horizontal and homogenous layers. Model parameters include the number (N) and thicknesses (h) of layers and shear wave velocity (vs) in each layer. The N represents model complexity. The larger N value is, the more complex the model is. A model that is too complex is prone to overfitting. The opposite is true for too simple models that underfit. Mathematically, the dispersion curve inversion problem is ill-posed, that is, there are a number of stratification models of the vs-h profile with different N, h, and vs values resulting in identical, or at least, similar dispersion curves. Because the N value is usually unknown during the inversion, the model selection is necessary in which a model fitting well with data and proper model complexity is identified in a pool of competitive models.

Nonetheless, research is rare that addresses the model selection issue in dispersion curve inversion problems. Bayesian framework can be used in model selection by quantifying the uncertainty in the stratification model. In this study, critical issues of Bayesian frameworks for quantifying the uncertainty in stratification model selection are discussed, including Bayesian inversion with a variable or a fixed number of layers in stratification models. Then, the major difficulties in computing the posterior distribution and Bayesian model evidence for determining N are demonstrated and discussed, which are mainly caused by the high-dimensional and highly nonlinear likelihood function. Finally, the sensitivity of model complexity to the error associated with the dispersion curve is explored preliminarily.
Global sensitivity analyses to characterize the risk of earth fissures in subsiding basins
Authors: Li Yueting , Zoccarato Claudia , Friedman Noemi , Benczúr András , Teatini Pietro
Published: March 2022

Earth fissure associated with groundwater pumping is a severe geohazard jeopardizing several subsiding basins generally in arid countries (e.g., Mexico, Arizona, Iran, China, Pakistan). Up to 15 km long, 1–2 m wide, 15–20 m deep, and more than 2 m vertically dislocated fissures have been reported. A common geological condition favoring the occurrence of earth fissures is the presence of shallow bedrock ridge buried by compacting sedimentary deposits. This study aims to improve the understanding of this mechanism by evaluating the effects of various factors on the risk of fissure formation and development. Several parameters playing a role in the fissure occurrence have been considered, such as the shape of the bedrock ridge, the aquifer thickness, the pressure depletion in the aquifer system, and its compressibility. A realistic case is developed where the characteristics of fissure like displacements and stresses are quantified with aid of a numerical approach based on finite elements for the continuum and interface elements for the discretization of the fissures. Modelling results show that the presence of bedrock ridge causes tension accumulation around its tip and results in fissure opening from land surface downward after long term piezometry depletion. Different global sensitivity analysis methods are applied to measure the importance of each single factor (or group of them) on the quantity of interest, i.e., the fissure opening. A conventional variance-based method is first presented with Sobol indices computed from Monte Carlo simulations, although its accuracy is only guaranteed with a high number of forward simulations. As alternatives, generalized polynomial chaos expansion and gradient boosting tree are introduced to approximate the forward model and implement the corresponding sensitivity assessment at a significantly reduced computational cost. All the measures provide similar results that highlight the importance of bedrock ridge in earth fissuring. Generally, the steeper bedrock ridge the higher the risk of significant fissure opening. Pore pressure depletion is secondarily key factor which is essential for fissure formation.
The thermal regime of mid-ocean ridges: geological perspectives and numerical modelling
Authors: Cannat Mathilde , Chen Jie , Olive Jean Arthur
Published: March 2022

The thermal regime of mid-ocean ridges determines their spreading modes (i.e., the combination of mid-ocean ridge tectonic, magmatic and hydrothermal processes that control the composition and structure of the oceanic lithosphere). It is determined by the balance of heat supply and heat loss in the axial region. Most heat is supplied through magma, while hydrothermal energy fluxes depend on the permeability and depth extent of the hydrothermal cooling domain, and on the thickness of the conductive boundary layer at its base. At fast spreading ridges, the flux of melt is high, the thermal regime is hot, and melt resides at depths of only a few kms in a steady state fashion, well within the reach of vigourous axial hydrothermal convection. At slow ridges, the melt flux is lower, the thermal regime is colder, so that melt can only reside durably at depths that are commonly > 10 km, out of the reach of vigourous (high permeability) hydrothermal systems. Melt there, however, is commonly injected higher up in the axial lithosphere, forming transient melt bodies in colder host rocks and triggering high temperature, black smoker, hydrothermal systems.

Here we report on numerical models that explore the thermal effects of varying both the melt flux and the depth of magma emplacement, a parameter that previously published mid-ocean ridge thermal models did not take into account. Our models do predict the large variability in thermal regime that is documented at slow ridges, from cold detachment-dominated settings, to hotter melt-rich segment centers. We discuss these results and the strengths and limitations of the modelling approach. We also explore the potential effects of varying the melt flux and melt emplacement depth with time at a given slow spreading ridge location, on crustal construction processes and on the respective roles of faults and melt intrusions to accommodate plate divergence.  
Attenuation of surface waves in the Antarctic marginal ice zone from in-situ measurements
Authors: Wahlgren Stina , Swart Sebastiaan , Biddle Louise , Thomson Jim , Hošeková Lucia
Published: March 2022

Antarctic sea ice has an important impact on the global climate, affecting albedo, global circulation and heat- and gas exchange between the ocean and the atmosphere. Wave energy propagating into the sea ice can affect the quality and extent of the sea ice, and wave attenuation in sea ice is therefore an important factor for understanding changes in the ice cover. Yet in-situ observations of wave activity in the Antarctic marginal ice zone are scarce, due to the extreme conditions of the region.

We estimate attenuation of significant wave height in the Antarctic marginal ice zone using in-situ data from two drifting Surface Wave Instrument Float with Tracking (SWIFT) buoys deployed in the Southern Ocean for two days in the Antarctic winter and two weeks in the Antarctic spring. The buoy location ranges from open water to more than 200 km into the sea ice. The extent of the sea ice coverage is determined using satellite sea ice concentration from AMSR-E and SAR imagery from Sentinel-1. Waves were observed more than 150 km into the sea ice, and in higher than 85 % sea ice concentration. Significant wave height and wave direction measured by the buoys in open water agreed well with ERA5 reanalysis data. We find that the significant wave height decayed exponentially in sea ice, which is consistent with physical experiments and other field observations in the Arctic and Antarctic marginal ice zones. 
Integrating responsiveness in the identification and characterization of compound heavy rainfall and wave storms events
Authors: Jiménez Jose A. , Costa Jose , Ortego Maribel , Llasat Maria del Carmen
Published: March 2022

From a risk management perspective, the relevance of compound events lies in the fact that they can significantly increase the intensity and/or the spatial and temporal extension of the impact (and damage) due to the synergic and/or cumulative action of different hazards. This compounding effect may overwhelm the capability of emergency-response services since these have to tackle an “unusual” high-damaging situation, they have to respond to a large number of emergency situations throughout the region at the same time, and/or they have to maintain the level of response during a relatively long period. Due to this, from this perspective, it would be important to incorporate the emergency/recovery services responsiveness to identify these events, as well as to evaluate their probability of occurrence. In this work we investigate this by parameterising this response as a time window between individual extreme events (rainfall and waves) to define the presence of a compound event. This time window depends on the intrinsic capacity of response of the available services, but also on the magnitude of contributing events as well as their spatial scale. In this work we analyse the variation of the probability of occurrence of compound heavy rainfall and wave storms events along the Catalan coast (NW Mediterranean) as a function of the responsiveness.

This work was supported by the Spanish Agency of Research in the framework of the C3RiskMed (PID2020-113638RB-C21/ AEI /  10.13039/501100011033)
Illuminating the deeper radio-stratigraphy of an alpine glacier using SAR processing 
Authors: Oraschewski Falk , Koch Inka , Ershadi Mohammadreza , Hawkins Jonathan , Drews Reinhard
Published: March 2022

The internal stratigraphy of alpine glaciers entails information about its past dynamics and accumulation rates. It further can be used for intercalibrating the age-depth scales of ice cores. The internal ice stratigraphy is often imaged using radar, but similar to polar ice sheets the deeper stratigraphy is often difficult to resolve with classical pulsed radar systems. For polar ice sheets, the introduction of phase coherent radars has illuminated this former echo-free zone (EFZ) and now patterns of folded, buckled and disrupted ice stratigraphy are clearly visible. Unfortunately, the new airborne and ground-based radar systems applied in polar regions are typically too heavy to be deployed in an alpine environment.

Here, we transfer the lightweight autonomous phase-sensitive radio-echo sounder (ApRES) to an alpine glacier targeting its echo-free zone (Colle Gnifetti, Italy/Switzerland). The ApRES is a coherent frequency modulated continuous wave radar with an integration time of 1 s per trace which we deployed in combination with a GNSS used in real time kinematic (RTK) mode. The latter allows repositioning of the antennas with sub-wavelength accuracy (approximately 5 cm) required to exploit the coherent signal. Like this, the radio-stratigraphy of the former EFZ at this site could be imaged using a matched filtering SAR method. The resulting radargrams cover former ice core sites (e.g., Ice Memory and KCC) and can be used to harmonize conflicting age-depth scales. This dataset will be analysed further in conjunction with ice-fabric measurements from ice cores to reveal how the anisotropic ice rheology imprints on the flow field of glaciers.