bluuebunny/crossref_metadata_2025 huggingface dataset:
Infrasound Signatures of Mediterranean Hurricanes
Authors: Forestier Edouard , Listowski Constantino , Dafis Stavros , Le Pichon Alexis , Farges Thomas , De Carlo Marine , Vergoz Julien , Claud Chantal
Published: March 2022

Mediterranean hurricanes, or medicanes, are tropical-like cyclones forming once or twice per year essentially over the waters of Mediterranean Sea. These mesocyclones pose a serious threat to coastal infrastructures and lives, because of their strong winds and intense rainfalls. Infrasound technology has already been employed to investigate acoustic signatures of severe weather events. In order to characterize medicane infrasound detections, we use data from the International Monitoring System (IS48 infrasound station, Tunisia), processed with a multi-channel correlation algorithm. For four different medicanes, high and/or low frequency detections are corresponding to these events, and non-detected cases are also discussed. These detections are discussed by considering other datasets such as satellite observations, a surface lightning detection network, and products mapping the intensity of the swell. While convective systems and lightning seem to be the main sources of detections above 1 Hz, hotspots of swell related to the medicanes are evidenced in the 0.1-0.5 Hz range.
Magnitude, frequency and climate forcing of global volcanism during the last glacial period as seen in Greenland and Antarctic ice cores (60-9 ka)
Authors: Lin Jiamei , Svensson Anders , S. Hvidberg Christine , Lohmann Johannes , Kristiansen Steffen , Dahl-Jensen Dorthe , Peder Steffensen Jørgen , Olander Rasmussen Sune , Cook Eliza , Astrid Kjær Helle , M. Vinther Bo , Fischer Hubertus , Stocker Thomas , Sigl Michael , Bigler Matthias , Severi Mirko , Traversi Rita , Mulvaney Robert
Published: March 2022

Large volcanic eruptions occurring in the last glacial period can be detected by their accompanying sulfuric acid deposition in continuous ice cores. Here we employ continuous sulfate and sulfur records from three Greenland and three Antarctic ice cores to estimate the emission strength, the frequency and the climatic forcing of large volcanic eruptions that occurred during the second half of the last glacial period and the early Holocene, 60-9 ka years before AD 2000 (b2k). Over most of the investigated interval the ice cores are synchronized making it possible to distinguish large eruptions with a global sulfate distribution from eruptions detectable in one hemisphere only. Due to limited data resolution and large variability in the sulfate background signal, particularly in the Greenland glacial climate, we only list Greenland sulfate depositions larger than 20 kg km-2 and Antarctic sulfate depositions larger than 10 kg km-2. With those restrictions, we identify 1113 volcanic eruptions in Greenland and 740 eruptions in Antarctica within the 51 ka period - where the sulfate deposition of 85 eruptions is found at both poles (bipolar eruptions). Based on the ratio of Greenland and Antarctic sulfate deposition, we estimate the latitudinal band of the bipolar eruptions and assess their approximate climatic forcing based on established methods. Twenty-five of the identified bipolar eruptions are larger than any volcanic eruption occurring in the last 2500 years and 69 eruptions are estimated to have larger sulfur emission strengths than the Tambora, Indonesia eruption (1815 AD). Throughout the investigated period, the frequency of volcanic eruptions is rather constant and comparable to that of recent times. During the deglacial period (16-9 ka b2k), however, there is a notable increase in the frequency of volcanic events recorded in Greenland and an obvious increase in the fraction of very large eruptions. For Antarctica, the deglacial period cannot be distinguished from other periods. This confirms the suggestion that the isostatic unloading of the Northern Hemisphere (NH) ice sheets may be related to the enhanced NH volcanic activity. Our ice-core based volcanic sulfate records provide the atmospheric sulfate burden and estimates of climate forcing for further research on climate impact and understanding the mechanism of the Earth system.
On the Deflections of Switchbacks
Authors: Laker Ronan , Horbury Tim , Matteini Lorenzo , Woolley Thomas , Stawarz Julia , Bale Stuart
Published: March 2022

Following their presence during Parker Solar Probe’s (PSP) first encounter, switchbacks have become an active area of research with several proposed mechanisms for their formation. Many of these theories have testable predictions, although it is not trivial to compare simulation results with in-situ data from PSP. For example, there is some debate regarding the deflection direction of switchbacks, with some theories predicting a consistent magnetic deflection in the +T direction in the RTN coordinate system. Such arguments are largely focussed on the first two PSP encounters, as these are the most studied encounters in the literature. We examine the deflection direction of switchbacks for the first eight PSP encounters, with the aim to clear up any ambiguity regarding this property of switchbacks. Much like the earlier results of Horbury et al. 2020 (during the first encounter) we find that switchbacks tend to deflect in the same direction for hours at a time. Although there is some consistency in deflection direction within an individual encounter, crucially we find that there is no preferred deflection direction across all the encounters. We speculate about the cause of these results and what implications they may have for switchback formation theories.
Multifunctionality of belowground food webs
Authors: Potapov Anton
Published: March 2022

Belowground consumers create complex food webs that regulate functioning, ensure stability and support biodiversity both below and above ground. However, existing soil food-web reconstructions do not match recently accumulated empirical evidence and there is no comprehensive reproducible approach that accounts for the complex resource, size and spatial structure of food webs in soil. I build on generic food-web organization principles and use multifunctional classification of soil protists, invertebrates and vertebrates, to reconstruct “multichannel” food-web across size classes of soil-associated consumers. I then use food-web reconstruction, together with assimilation efficiencies, to calculate energy fluxes assuming a steady-state energetic system. Based on energy fluxes, I describe a number of indicators, related to stability, biodiversity and multiple ecosystem-level functions such as herbivory, top-down control, translocation and transformation of organic matter. The multichannel reconstruction can be used to assess trophic multifunctionality (analogous to ecosystem multifunctionality), i.e. simultaneous support of multiple trophic functions by the food-web, and compare it across communities and ecosystems spanning beyond the soil. With further validation and parametrization, the multichannel reconstruction approach provides an effective tool for understanding and analysing soil food webs. I believe that having this tool will inspire more people to comprehensively describe soil communities and belowground-aboveground interactions. Such studies will provide informative indicators for including consumers as active agents in biogeochemical models, not only locally but also on regional and global scales.
Isotopic and geochemical evolution of rainwater percolating through the rocky outcrops: Judaea mountain case study.   
Authors: Letz Or , Siebner Hagar , Avrahamov Naama , Egozi Roey , Dahan Ofer
Published: March 2022

Groundwater recharge of mountain aquifer requires detailed knowledge of the hydrologic system and adequate monitoring and modeling methods to determine water amount and water quality evolution. Mountain aquifers are well known of their highly complex lithologic structure and surface morphology. These become more significant in dry climate regions (<300 mm rainfall/year) which are characterized by erratic rain pattern and extreme deep thickness unsaturated zone.

In this study we monitor the isotopic and geo-chemical evolution affecting the composition of the unsaturated porewater during deep infiltration, from surface to depth that is not affected from evaporation. The geo-chemical processes were characterized related to land surface morphology and climate conditions.

The research setup includes instrumentation of first-order stream which is characterized by two main typical geomorphologic setting: rocky terrain and deep soil along the stream channel. Each plot was instrumented with a monitoring setup that include a meteorological station and Vadose Zone Monitoring System (VMS) that enables continuous water content measurement and collection of unsaturated porewater from the vadose zone.

Fast increases in water content and arrival of depleted δ18O (VSMOW) reveal quick and deep infiltration of rainwater during storm events, while enriched δ18O arrival indicates slower infiltration of water that is exposed to evaporation. In addition, the geo-chemical processes exhibited depletion in δ13C (PDB) of rainwater during the infiltration (-19 to -11 ‰) which indicates on dominant of biogenic activities and relatively low rock-water interactions. Major elements correlation network expresses the contribution of dust and rain to the rock evolution across the water flow path.

The study results clearly exhibited different infiltration rates in each site. Fast infiltration at the rocky terrain due to rock outcrops on the surface create funnels for collecting the local runoff and delivering it into high permeability fractured zones where the water penetrates directly to the deep sections. In contrast, the bare soil areas such as hilltops or man-made terraces in streams with highly developed soil cross-section, reveal limited infiltration. Also, the annual rainfall pattern impacts the geochemical process and finally impacts the groundwater quantity and quality.
Understanding the taphonomic bias on the benthic foraminiferal bottom current proxy
Authors: Schmidt Johanna , Herwartz Daniel , Saupe Anna , Petersen Jassin , Grunert Patrick
Published: March 2022

Benthic foraminifera provide key information for the reconstruction of ocean bottom currents. In the Iberian Margin Contourite Drift System, abundances of a distinct group of benthic foraminifera are controlled by the strength and nutrient load of bottom currents. This so-called elevated epifauna (EEF) comprises highly specialized suspension feeding benthic foraminifera attached to elevated substrates as an adaptation to strong bottom currents. Schönfeld (2002) demonstrated a direct relation between EEF abundances and Mediterranean Outflow Water strength at the Iberian Margin in modern surface samples and established EEF abundances as a bottom current proxy. Faunal and geochemical data from Pliocene-Pleistocene contourites drilled during IODP Exp. 339 in the Gulf of Cádiz, however, showed a poor correlation of EEF abundances with other bottom current proxy data, indicating a bias by depositional or taphonomic processes.

The tectonically active Iberian Margin is characterized by a complex depositional environment shaped by alongslope and downslope transport. Taphonomic processes linked to transport and loss of foraminiferal tests during early fossilization potentially bias fossil EEF abundances in marine slope sediments and may result in overestimation of bottom current speeds. Our understanding of these taphonomic processes is still rather poor. Stable oxygen and carbon isotope ratios from foraminiferal tests in Pleistocene contourites and turbidites can be used to identify allochthonous tests and provide insights into the extent of downslope transport at the Iberian Margin. The aim of this study is to quantify the effects of taphonomic processes on fossil foraminiferal assemblages and to establish an improved EEF proxy method. The improved method will provide researchers with a reliable, well-calibrated and easily applicable tool for bottom current reconstruction.

 

Reference: Schönfeld, J. (2002). A new benthic foraminiferal proxy for near-bottom current velocities in the Gulf of Cadiz, northeastern Atlantic Ocean. Deep Sea Research Part I: Oceanographic Research Papers, 49(10), 1853-1875.
Sea level projections portal for communicating impacts to policymakers
Authors: Matthews Andrew , Jevrejeva Sveta
Published: March 2022

Small island developing states are particularly at risk from extreme water levels and coastal erosion. Policy makers require information to support decision making on how to improve resilience and adapt to future changes. Here we present a web portal designed to display different sea level projections across the Caribbean Sea, developed as part of our contribution to the UK Government’s Commonwealth Marine Economies (CME) programme and the UK Natural Environment Research Council’s ACCORD programme.

The portal has been designed using free and open-source software, and is self-contained, allowing it to be deployed on local partner websites with minimal effort. The responsive design allows the portal to work as well on as it does on PCs.

Currently the portal displays projected sea level for over 50 locations across the Caribbean, along with sea level data available at the site, but extra sites can be added easily. Quality controlled data has been used where possible; where this is not available, we have used automated software developed earlier in the CME programme to perform basic quality control.

Similarly, the portal provides projections from four sea level scenarios based on earlier National Oceanography Centre work, but other projections can be added by updating configuration files.

The portal can be accessed at https://psmsl.org/accord/projections.html
COVID-19 effects on measurements of the Earth Magnetic Field in the urbanized area of Brest 
Authors: Oehler Jean-Francois , Leon Alexandre , Lucas Sylvain , Lusven André , Delachienne Gildas
Published: March 2022

COVID-19 effects on measurements of the Earth Magnetic Field in the urbanized area of Brest (Brittany, France)

Jean-François OEHLER1, Sylvain LUCAS1, Alexandre LEON1, André LUSVEN1, Gildas DELACHIENNE1

1Shom (Service Hydrographique et Océanographique de la Marine), Brest, France

 

Since September 2019, Shom’s Magnetic Station (SMS) has been deployed in the north neighbourhoods of the medium-sized city of Brest (Brittany, France, about 210,000 inhabitants). SMS continuously measures the intensity of the Earth Magnetic Field (EMF) with an absolute Overhauser sensor. The main goal of SMS is to derive local external variations of the EMF mainly due to solar activity. These variations consist of low and high parasitic frequencies in magnetic data and need to be corrected. Magnetic mobile stations or permanent observatories are usually installed in isolated areas, far from human activities and electromagnetic effects. It is clearly not the case for SMS, mainly for practical reasons of security, maintenance and data accessibility. However, despite its location in an urbanized area, SMS stays the far western reference station for processing marine magnetic data collected along the Atlantic and Channel coasts of France.

The corona pandemic has had unexpected consequences on the quality of measurements collected by SMS. For example, during the French first lockdown between March and May 2020, the noise level significantly decreased of about 50%. Average standard deviations computed on 1 Hz-time series over 1 min. periods fell from about 1.5 nT to 0.8 nT. This more stable behavior of SMS is clearly correlated with the drop of human activities and traffic in the city of Brest.

 

Keywords: Shom’s Magnetic Station (SMS), Earth Magnetic Field, COVID19.

 
On the use of ABACUS high resolution glider observations for theassessment of phytoplankton ocean biomass from CMEMS model products
Authors: Aulicino Giuseppe , Cesarano Cinzia , Zerrouki Mohammed , Ruiz Simon , Budillon Giorgio , Cotroneo Yuri
Published: March 2022

Ocean biomass distribution has a growing importance in the world economy as a global strategic reserve, due to environmental and industrial applications and its variability related to climate change. Satellite imagery allows multi-resolution methodologies to obtain estimation, and hopefully classification, of biomass content over sea surface. This information is largely used in numerical simulations and nowadays represents an important contribute to future projections. Nevertheless, satellite, models and classical in situ monitoring resolution/accuracy sometimes cannot provide data at the finer spatial scales needed to describe the complex threedimensional water column system. On the other hand, glider surveys allow scientists to collect observations of ocean phenomena at very high resolution along the water column, to assess numerical simulations reliability and, eventually, to assimilate these data into ocean models. In this study, we present a quantitative comparison between the glider observations collected in the Algerian Basin (Western Mediterranean Sea) during the ABACUS surveys from 2014 to 2018, and the daily outputs of two co-located CMEMS model products (i.e., GLB and IBI).
The achieved results point out that model products are well correlated with glider potential temperature measurements but they still need improvements to provide a correct representation of the chlorophyll concentration variability in the study area. Generally, IBI daily simulations present higher linear correlation with concurrent glider in situ data than GLB ones. IBI products also reproduce better the pattern of the local maxima of chlorophyll concentration across the Algerian Basin. Nevertheless, they largely underestimate glider chlorophyll measurements and present significant differences that limit their capability to reproduce its upper ocean concentration that is needed for accomplishing advanced ecological studies.
Annual estimates of basal melting and calving from Antarctic ice shelves during 2010-2019
Authors: Davison Benjamin , Hogg Anna , Gourmelen Noel , Andreasen Julia , Rigby Richard , Wuite Jan , Nagler Thomas
Published: March 2022

Ice shelves play a crucial role in controlling rates of ice discharge across Antarctica’s grounding lines. Mass loss from ice shelves, predominately due to basal melting and calving, can reduce the buttressing force provided by ice shelves, leading to increased grounded ice discharge. Despite the importance of ice shelves, existing estimates of calving and freshwater fluxes from ice shelves have utilised disparate datasets valid for inconsistent time periods or have relied on simplifying assumptions, resulting in a limited account of the health of many ice shelves and little indication of processes driving ice shelf mass imbalance.

Here, we quantify calving and basal melt fluxes at annual temporal resolution during 2010 to 2019. Our annual measurements account for annual variations in ice velocity and basal melt rate for 183 ice shelves, and annual variations calving front position for 34 major ice shelves (accounting for ~90% of the ice shelf area). On average during the study period, a calving flux of 1283±109 Gt yr-1 is roughly equal to a melt flux of 1247±149 Gt yr-1. Inter-annual variations in the fluxes of both basal meltwater and calving mean that the melt contribution to ice shelf mass loss varies between 35% and 62%, with the lowest contributions in years with large calving events. These large (>100 Gt) calving events are rare (8 events during 2010-2019), yet account for 35% of the total ice shelf calving flux, highlighting the importance of large calving events for ice shelf mass balance over short time scales. Eighty percent of ice shelves, including many in East Antarctica, are melting at or faster than their balance rates, indicating that ocean-driven erosion of ice shelf grounding lines is widespread around Antarctica. Furthermore, we find a significant and strong positive correlation (R=0.68) between basal melt flux and grounding line discharge, implying that ocean-driven melt may pace grounded ice loss from Antarctica.
Mitigating array-induced bias in ambient noise beamforming
Authors: Löer Katrin , Finger Claudia
Published: March 2022

We show that the geometry of a seismic array affects estimates of velocity and propagation direction of ambient seismic noise wavefields measured with beamforming techniques. We demonstrate how this results in apparent anisotropy estimates and present first approaches to mitigate the effect.

Beamforming is an array technique originating from earthquake seismology that has become increasingly popular to analyse the ambient noise wavefield with the goal to characterise ambient noise sources (e.g., regions of origin of Love and Rayleigh waves) as well as subsurface structures (shear-velocity profiles, fracture orientation). Beamforming techniques estimate the dominant velocity, direction of propagation, and (in case of three-component data) the polarisation of a wavefield recorded within a limited time window at a seismic array. An important parameter in beamforming is the array response function, which shows the response of an array to a wave that is arriving directly from below. It can be thought of as the fingerprint of the array and depends on the array geometry, i.e., number of stations, station spacing, and orientation of station pairs. A biased array can lead to oversampling of certain directions and, thus, prioritising them in the beamform heatmap.

The first attempt to mitigate the influence of the array focuses on analysing the orientation of station pairs in an array and applying a weighting matrix in order to enhance contributions from orientations that are underrepresented. This approach leads to a modified array response function, that looks more regular and has the fingerprint of the array partly removed. Using synthetic data and different array geometries we demonstrate the effect on the estimated anisotropy.

The second approach is based on simulating synthetic, isotropic wavefield recordings at an array of choice and measuring their dominant velocities and propagation directions using beamforming. Comparing expected and observed values shows that the effect of the array can be significant, in particular when multiple sources act simultaneously (as is often the case for ambient noise): both measured velocities and propagation directions are affected by the design of the array, leading to erroneous anisotropy estimates. Once we have an estimate of array-induced anisotropy, however, we can subtract it from the anisotropy measured in real data and thereby reduce the effect. Examples for different array geometries are presented and compared.
An optimized online version of NESTORE software package for the forecasting of strong aftershocks: an application to Italian clusters 
Authors: Gentili Stefania , Brondi Piero , Di Giovambattista Rita
Published: March 2022

NESTORE (Next STrOng Related Earthquake) is a recently developed algorithm (Gentili & Di Giovambattista 2017, 2020) to recognize clusters in which a strong mainshock is followed by an aftershock of similar magnitude. Specifically, NESTORE labels clusters as type A if the magnitude difference between the mainshock and its strongest aftershock is less than or equal to 1, otherwise as type B. After an intense earthquake, the prediction of strong following events is strategic for civil protection purposes. In fact, already weakened structures may suffer further damage, increasing the risk of collapse and casualties. The goal of NESTORE is a near real-time estimation of the probability that the ongoing cluster is type A. The software is based on a set of parameters (features) of seismic clusters calculated at increasing time intervals after the mainshock. In particular, the algorithm exploits a training procedure with a feature-based machine learning approach. The features are related to the evolution of the number of events and their space-magnitude distribution over time. To make NESTORE a suitable software for online sharing, we optimized its structure. Specifically, some functions have been improved, further ones have been added, and a new name structure has been introduced to better characterize the three independent modules of NESTORE (cluster identification, training, and testing). This software renovation has been developed in the frame of project “Analysis of seismic sequences for strong aftershock forecasting” funded by a grant from the Italian Ministry of Foreign Affairs and International Cooperation within the collaboration in science and technology between Italy and Japan. We applied this new version of NESTORE to Italian seismicity and in particular to North-Eastern Italy, and obtained information on the features with best performances in terms of type A and B cluster discrimination.

 

Funded by a grant from the Italian Ministry of Foreign Affairs and International Cooperation
Beyond Hasselmann and Leith: The challenge of non-Markovian and fractional stochastic climate modelling
Authors: Watkins Nicholas Wynn , Calel Raphael , Chapman Sandra , Chechkin Aleksei , Ford Ian , Klages Rainer , Stainforth David
Published: March 2022

The stochastic energy balance models (SEBMs) pioneered by  Hasselmann and  Mitchell [1] have long been known to climate scientists to be important aids to gaining both qualitative insight and quantitative information about global mean temperatures.  SEBMs are now much more widely visible, after the award of last year’s Nobel Prize to Hasselmann, shared with Manabe and Parisi [1].

The earliest univariate SEBMs were, however, built around the simplest linear and Markovian stochastic process, and researchers have very intentionally exploited their equivalence to the Langevin equation of 1908. Although multivariate SEBMs have now been extensively studied [1,2] and provide one important route to incorporating non-Markovian memory effects into climate dynamics, my presentation will discuss the continuing value of univariate SEBMs, especially when coupled to other models. I  will also highlight how we and others (e.g. [4,5]) are going beyond the first SEBMs to incorporate more general models of temporal dependence, motivated by evidence of non-Markovian, and in particular long-ranged, memory in the climate system.  This effort has brought new and interesting challenges, both in mathematical methods and physical interpretation.

I will highlight our recent paper [3] on using a Hasselmann-type EBM to study the economic impacts of climate change and variability and our other ongoing work [6, and its updated version, 7] on  generalised (and in particular fractional) Hasselmann univariate SEBMs. I will compare our model [6,7] with Lovejoy and co-workers' FEBE [5], and discuss what the requirements are in order for such non-Markovian SEBMs to exhibit fluctuation-dissipation relations, which have been debated in the  SEBM field since the early work of Leith in the 1970s.

[1] Scientific background on the Nobel prize in physics 2021, Nobel Committee, Royal Swedish Academy of Sciences.

[2] Franzke and O’Kane, eds. Nonlinear and Stochastic Climate Dynamics, CUP, 2017.

[3] Calel et al, Nature Communications, 2020.

[4] Rypdal et al, Climate, 2018.

[5] Lovejoy et al, QJRMS, 2021.

[6] Watkins et al, On Generalized Langevin Dynamics and the Modelling of Global Mean Temperature, 2021, https://link.springer.com/chapter/10.1007%2F978-3-030-67318-5_29

[7] Watkins et al, arXiv: https://arxiv.org/abs/2007.06464v2.
A pore-scale study of bacterial chemotaxis with segregated and controlled nutrient sources
Authors: Stoll Maximilian F. , Stocker Roman , Jimenez-Martinez Joaquin
Published: March 2022

Natural porous systems, like soils and aquifers, are physically and chemically highly heterogeneous. Microorganisms inhabiting these environments are therefore exposed to heterogeneous fluid flow velocities and nutrient landscapes. Bacteria capable of biasing their motion to swim along chemical gradients – known as chemotaxis – profit from their ability to localize and navigate towards nutrient hot spots, such as soil aggregates or plant roots.
We propose a novel experimental microfluidic platform to study chemotaxis at the pore-scale, allowing full optical access to the pore space and simultaneously enabling control over the spatio-temporal availability of nutrients. The microfluidic device contains hydrogel features, acting as nutrient hotspots, embedded in a porous medium, made out of transparent polydimethylsiloxane (PDMS) pillars. Nutrients are transported by diffusion from the access channels through the hydrogel into the porous medium, where they are released. The generated nutrient gradients downstream of the hotspots under flow conditions drive the swimming of chemotactic bacteria.
This approach enables the study of subsurface processes at the pore-scale under more realistic conditions, and shed new light onto the influence of physical and chemical heterogeneity on bacterial dispersion and residence time in the subsurface.

Keywords: porous media, soil, chemotaxis, microfluidics, heterogeneity
Machine learning and RFID-based large wood tracking in rivers 
Authors: Aarnink Janbert , Ruiz-Villanueva Virginia , Vuaridel Marceline
Published: March 2022

Large wood (10cm diameter & 1m long) gets recruited into a mountain river system from surrounding forested areas. Instream large wood positively influences the diversity of the river system, creating habitats for terrestrial and aquatic species. However, the corresponding risk to the presence of instream large wood is a more controversial topic in river management. On the one hand, large wood increases the riverbed roughness, partly dissipating energy during a flood. On the other hand, its transport during floods might cause damage to infrastructure. Direct observations or monitoring stations are scarce and knowledge on how and when wood is transported remains far from complete.

In order to quantify a river’s instream wood transport regime, we are developing a video-based wood tracking system that counts the number of pieces that pass a certain point and estimates their sizes. We use a DeepSORT algorithm that uses machine learning to identify individual pieces of instream wood and draws a bounding box around every piece. Subsequently, it uses a Kalman filter to estimate the piece’s trajectory. To prevent counting the same pieces multiple times, the projected trajectory is compared to the detections in the subsequent frame. The system is designed so that it can be applied to different datasets and will be available to the increasing wood monitoring efforts around the world. For a more detailed look into the large wood regime at one of our main study sites (Vallon de Nant, Switzerland), and to calibrate our video-based wood tracking system, we have installed RFID tags into all pieces of large wood (approximately 1000 pieces) over a stretch of 3 km. A stationary RFID antenna registers the tagged pieces that pass by, of which the size and origin are known.

First results show that the custom trained DeepSORT algorithm can not only identify pieces of instream wood, but also largely follow the pieces in subsequent frames. The approach seems to outperform current computer vision solutions. In our ongoing research, we aim to make the system more robust and expand the observation network to other rivers. With an expanding dataset, containing (manually) labelled training samples from different locations, and the low-cost measurement set-up, the system promises to aid successfully to an intercomparison of river systems in the context of the wood management debate.

This work is supported by the SNSF Eccellenza project PCEFP2-186963 and the University of Lausanne.
Multicomponent transport and geochemical reactions under evaporative conditions at the soil/atmosphere interface
Authors: Ahmadi Navid , Muniruzzaman Muhammad , Battistel Maria , Rolle Massimo
Published: March 2022

The reactive transport of gas components in the subsurface significantly influences key biogeochemical processes. For instance, reactive transport of oxygen in soil influences mineral dissolution/precipitation and control pore water chemistry. The dynamics of such processes is affected by land-atmosphere interactions and controlled by the exchange processes occurring at the soil/atmosphere interface. One notable example is soil water evaporation that is driven by the exchange of water vapor and energy across the soil/atmosphere interface. This process creates a two-phase system in soil pores and induces a non-linear and complex distribution of the fluid phases (i.e., liquid and gaseous phase) and gas components in the individual phases. The spatiotemporal evolution of the fluid phases and the transport of gas components with and across the phases, in turn, exert important controls on key subsurface biogeochemical processes.

In this study, we explore the impact of evaporation on reactive transport of oxygen in soil using well-controlled laboratory experiments and numerical simulations. We performed a set of evaporation experiments in which an initially water saturated, anoxic soil column containing a layer of pyrite is exposed to a low-humidity atmospheric condition. This resulted in the formation of a partially saturated zone, the invasion of a drying front, and the penetration of oxygen into the porous medium, leading to oxidative dissolution of pyrite. In parallel, we also performed similar experiments under fully water-saturated conditions in order to compare the extent of mineral dissolution with and without evaporation. The spatiotemporal distribution of oxygen was measured using a non-invasive optode technique during the experiments and the concentration of dissolved reaction products (i.e., sulfate, iron and pH) was quantified at the end of the experiments. We developed a non-isothermal multiphase and multicomponent reactive transport model and applied the model to quantitatively interpret the experimental datasets and to understand the coupling between fluid displacement, component transport and geochemical processes.
Computing wildfire Susceptibility Maps at the national level in Italy: a Machine Learning approach
Authors: Trucchia Andrea , Meschi Giorgio , Tonini Marj , Fiorucci Paolo
Published: March 2022

Wildfires are a serious social and environmental issue in the Mediterranean basin, menacing human lives, infrastructures and ecosystems. Italy, due to land cover, orography  and climate, expresses a complex wildfire regime that is worth investigating. Static maps, such as susceptibility, hazard and risk maps, are valid allies for wildfire management and land use planning. In particular, the wildfire susceptibility is defined as the spatially distributed probability of experiencing wildfire at a certain point, depending only on  the intrinsic characteristics of the territory. In the presented work, a Machine Learning  (ML) model  is built following a similar approach of [1], to produce different National Scale susceptibility maps for Italy. The adopted algorithm is Random Forest, an ensemble ML method.

Since Italy exhibits two different wildfire seasons, the summer and the winter one, two maps are produced, to identify the different regimes. The presented analysis at the national scale allows the experts and the decision makers to have a deep understanding on the wildfire regimes, and may constitute a solid paradigm for wildfire risk management. The Random Forest associated  a data-set of geographic (orography, land cover), anthropic (distance from crops, roads and urban features) and climatic information (mean precipitation and temperature) to the database of ground-retrieved burned area polygons.  The classifier is then employed to evaluate each pixel of the study area, producing the susceptibility map. The performance of the adopted frameworks are evaluated via spatial cross validation and the evaluation of mean squared error and Area Under the RoC curve  on a test dataset.  A subsequent analysis of the importance of each input factor through the Gini impurity method allows to spot the most important variables, paving the way for further improvements in the dataset.

 

References

 

[1] Tonini, M.; D’Andrea, M.; Biondi, G.; Degli Esposti, S.; Trucchia, A.; Fiorucci, P. A Machine Learning-Based Approach for Wildfire Susceptibility Mapping. The Case Study of the Liguria Region in Italy. Geosciences 2020, 10, 105. https://doi.org/10.3390/geosciences10030105 
Global sea state variability from new multivariate multi-mission satellite altimeter products, reanalyses and wave buoys
Authors: Timmermans Ben , Gommenginger Christine , Shaw Andrew
Published: March 2022

Accurate knowledge and understanding of the sea state and its variability is crucial to numerous oceanic and coastal engineering applications, but also to climate change and related impacts including coastal inundation from extreme weather and ice-shelf break-up. An increasing duration of multi-decadal altimeter observations of the sea state motivates a range of global analyses, including the examination of changes in ocean climate. For ocean surface waves in particular, the recent development and release of products providing observations of altimeter-derived significant wave height make long term analyses fairly straightforward. In addition, advances in imaging SAR processing for some missions have made available multivariate observations of sea state including wave period and sea state partition information such as swell wave height. Records containing multivariate information from both Envisat and Sentinel-1 are included in the version 3 release of the European Space Agency Climate Change Initiative (CCI) for Sea State data product.

 

In this study, long term trends and variability in significant wave height spanning the continuous satellite record are intercompared across high-quality global datasets using a consistent methodology. We make use of products presented by Ribal et al. (2019), and the recently released products developed through Sea State CCI. In particular, making use of long term and continuous time series from moored data buoys, we demonstrate the impact of steadily increasing altimeter sample density on trend estimation. In addition to wave height, global climatologies for wave period are also intercompared between the recent Sea State CCI product, ERA 5 reanalysis and in situ observations. Results reveal good performance of the CCI products but also raise questions over methodological approach to multivariate sea state analysis. For example, differences in computational approach to the derivation of higher order summaries of wave period, such as the zero-crossing period, lead to apparent discrepancy between satellite products and reanalysis and modelled data. It is clear that the broadening diversity of reliable sea state observations from satellite, such as provided by the Sea State CCI project, thus motivates new intercomparisons and analyses, and in turn elucidates inconsistencies that have been previously overlooked.

 

We discuss these results in the context of both the current state of knowledge of the changing wave climate, and the on-going development of CCI Sea State altimetry and imaging SAR products.
Response of shallow gas charged Holocene deposits in the Yangtze Delta to erosion induced by diminished sediment supply: Increasing greenhouse gas emission
Authors: Chen Yufeng , Deng Bing , Zhang Weiguo , Gao Shu
Published: March 2022

River deltas have long been considered as important carbon sinks. However, the presence of shallow gas (mainly composed of methane) and the processes of delta erosion caused by diminished sediment supply bring complexities to the present situation. This study investigates the response of the gas charged deposits in the Yangtze subaqueous delta to erosion process based on historical bathymetric data and the dataset obtained from a seismic survey. Both seismic and bathymetric data reveal a prominent erosion belt at water depth ranging from 5-20 m, extending from the southwest to the northeast in the nearshore area of the Yangtze subaqueous delta. Erosion is severe in the south while slight in the north area due to the differences in hydrodynamic condition, sediment erodibility and sensitivity to sediment reduction. Seabed erosion reduces the thickness of cap bed, as well as overburden pressure at gas front, making it easier for gas to seep through the sediment column and bypass the process of anerobic oxidation of methane within the SMT (an important methane filter). The spatial coincidence between the shallower gas front and pockmarks also indicates that sea bed erosion accelerates gas seeping activities. It expected more greenhouse gas would be expelled into atmosphere under the impact of bed erosion induced by ongoing decline of riverine sediment supply.
Influence of planetary space weather on the shapes of Venus plasma boundaries
Authors: Signoles Claire , Persson Moa , Wolff Alexander , Martinez Nicolas , Lindwall Viktor , Futaana Yoshifumi , Rojas-Mata Sebastian , Zhang Tielong , André Nicolas , Aizawa Sae , Fedorov Andrei
Published: March 2022

As Venus does not have an intrinsic magnetic field, the solar wind interacts directly with the Venusian atmosphere, altering its structure and composition, for example through atmospheric ion escape to space. In particular, the interaction will result in the formation of plasma boundaries, which separate regions of different plasma populations around Venus. Knowing how space weather influences the shape of these boundaries is one of the key pieces to understanding the current state of the Venusian atmosphere.

During its eight years mission, including more than 3000 orbits around Venus, Venus Express made measurements of the plasma environment, covering a wide range of upstream conditions. Using conjoint plasma and magnetic field measurements from the ASPERA-4 (Analyser of Space Plasma and Energetic Atoms) and the magnetometer instruments, we identified the locations where the spacecraft crossed the bow shock and the ion composition boundary for each orbit. Using the derived dataset, we then determined the boundary shapes with a two-parameter fit. The boundary shape fittings were done with respect to one or multiple upstream conditions.

Here we report that both boundaries are highly dependent on solar wind extreme ultraviolet (EUV) flux, expanding further from the planet at solar maximum. A likely explanation is that at solar maximum, combined heating of the exosphere ions and a higher photoionization rate lead to a higher planetary ion production. These additional ions increase the internal thermal pressure, pushing the boundaries outward.

Additionally, at solar minimum, solar wind parameters like dynamic pressure and energy flux were found to not affect the shape of the bow shock, which is consistent with previous studies. The influence of the strength and orientation of the interplanetary magnetic field, the Mach number, and potential correlations between multiple upstream parameters, are also discussed in this talk.
Linking shallow gas occurrences and deeper structure offshore western Poland (Pomeranian Bight)
Authors: Nguyen Quang , Malinowski Michal , Kramarska Regina , Kaulbarsz Dorota , Huebscher Christian
Published: March 2022

Presence of methane in the shallow sediments of the southern Baltic Sea area is a well-known phenomenon. In the Polish Exclusive Economic Zone (Polish EEZ), the observations were mostly based on hydroacoustic data, as well as sediment and water sampling. However, majority of the occurrences were reported in the eastern part of the EEZ (e.g., Gulf of Gdansk). Here we focus on the western part of the Polish EEZ (Pomeranian Bight) and combination of both hydroacoustic and seismic data to provide evidences of free gas in the shallow sediments.

Our study area is located in the inverted part of the Permo-Mesozoic Polish Basin, so called Mid-Polish Swell, with the main inversion-related fault zones: Adler-Kamień and Trzebiatów faults, rooted in the pre-Permian basement (Devonian, Carboniferous?).  Both the Permian and Paleozoic rocks are a proven hydrocarbon exploration play, with an ongoing exploration at the structural trend extending further onshore towards SE. We use seismic data acquired during the RV Maria S. Merian cruise in 2016 (cruise MSM52) with the co-located sub-bottom sediment profiler (Parasound) data.

Various signatures of shallow gas were identified across the seismic section including gas chimneys, shallow bright spots, seafloor polarity reversal and acoustic blanking. Seismic attributes were used to highlight and support interpretation of shallow gas anomalies. Anomalous zones in seismic data were observed in both the Cretaceous, Jurassic and Triassic section in the vicinity of the Adler-Kamień and Trzebiatów fault zones. Parasound data illustrated corresponding free gas accumulation in Pleistocene to Quaternary successions. Amplitude versus offset (AVO) analysis was carried out at two locations of the assumed gas chimney. The gradient analysis from angle gathers shows clearly amplitude variations with increasing offset due to existence of gas in the formation, in addition, free gas amplitude anomalies were highlight in the intercept vs gradient crossplot.

Our data indicate existence of potential fluid migration pathways from the Permian-Paleozoic reservoirs to shallow sediments below the seabed and helps in explanation of how this free gas escapes to the sea bottom.

This study was funded by the Polish National Science Centre grant no UMO-2017/27/B/ST10/02316. Cruise MSM52 has been funded by German Science Foundation DFG and Federal Ministry of Education and Research (BMBF). We thank Federal Institute for Geosciences and Natural Resources (BGR) for their support during seismic data acquisition and sharing the data.
Regridding and interpolation of climate data for impacts modelling – some cautionary notes
Authors: Chandler Richard , Barnes Clair , Brierley Chris , Alegre Raquel
Published: March 2022

Users of climate data must often confront the problem that information is not available at the precise spatial locations of interest; or the related problem that multiple sources of information provide data at different collections of locations. An example of the first situation is the use of weather station data to calibrate a hydrological or land surface model requiring inputs on a regular grid; an example of the second is the use of information from an ensemble of climate models to sample structural uncertainty, but where each model produces output on its own grid. Dealing with this spatial misalignment is a common first step in any analysis, and is usually done by some form of interpolation. In this poster, we use standard approaches to convert regional climate model (RCM) outputs from the EuroCORDEX ensemble to the common grid used in the UK national Climate Projections (UKCP). We find that although these standard approaches perform acceptably in some situations, in others they can induce surprisingly large biases and inconsistencies in the statistical properties of the resulting fields – particularly those relating to variability and extremes. For example, although the resolutions of the UKCP grid and the EuroCORDEX RCMs are all similar, it is not hard to find locations where the maximum daily precipitation within a month is systematically underestimated by 5-10% in the regridded data; and where the maximum daily precipitation over a 20-year period is systematically underestimated by 25%. These effects could have major implications for impacts studies carried out using interpolated or regridded data, if they are not recognised and dealt with appropriately. We offer some suggestions, varying in ease of implementation, for dealing with the problem.