bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved cosmogenic Ne measurements using ThermoFisher ARGUS VI
Authors: Di Nicola Luigia , Györe Domokos , Hamilton Doug , Stuart Finlay
Published: March 2022

Cosmogenic Ne is used to record timing and rates of surface processes on the Earth and Moon and the time of meteorite release from parent bodies. Precise determination of neon isotopes in rocks and minerals has improved in the last ten years largely as a consequence of developments in mass spectrometry and associated electronics.  In this presentation we will report the performance of an ARGUS VI mass spectrometer tuned for cosmogenic Ne determinations from both extra-terrestrial and terrestrial material. The instrument is connected to an automated laser gas extraction and purification system and has several advantages over off-the-shelf instrumentation. The remote operation of sample heating, gas purification, separation and isotope analysis increases sample throughput, and the exact repetition of the procedures and overnight determination of calibrations and blank measurements improves data quality, facilitates determination of isobaric interferences and eases trouble shooting. The low static volume results in high sensitivity, while the stable electronics and multi-collection allows high precision Ne isotope determinations in terrestrial and extra-terrestrial samples that are significantly smaller than typically analysed to date.

Two analytical protocols are applied depending on sample Ne concentration. Multi-collection Faraday mode is used for extra-terrestrial material. This yields a 4-fold improvement in the overall uncertainty of the Ne isotope ratios (0.5%) compared to that obtained using 5-10x larger samples in peak-jumping mode on our workhorse instrument. Cosmogenic Ne determinations in 20-30 mg of terrestrial material are made using the compact discrete dynode detector in peak-jumping.  Replicate analysis of CREU-1 quartz yields reproducibility of ±3.7% (1σ), comparable to the data quality for 5-10x more material.  In addition to instrument performance characterisation, we will summarise data from studies of terrestrial and extra-terrestrial material that demonstrate routine capability.
Identification and analysis of channel connectivity in rivers and estuaries
Authors: Hiatt Matthew , Kleinhans Maarten , Addink Elisabeth , van Dijk Wout , Sonke Willem , Speckmann Bettina
Published: March 2022

The channel patterns in rivers and estuaries range from meandering single-thread channels to complex channel networks comprising looping, branching, and offshoot structures through which water, resediment, and nutrients are transported. Representing channelized systems as networks provides a mathematical framework for analyzing transport and has become increasingly common in hydrology and geomorphology. However, several challenges remain: 1) the automatic extraction of multi-channel networks from topography has historically been a major challenge; 2) the relative importance of individual channels in the identified network; and 3) the issue of transport direction in channel networks, especially where bi-directional flows dominate in estuarine environments. This presentation discusses recent work addressing these three challenges with the introduction of a novel algorithm for extracting topology and geometry from digital elevation models of braided rivers and estuaries and by quantifying structural and dynamical connectivity in two flow directions for estuaries around the world. In both efforts, networks are constructed with network links representing channels and networks nodes representing channel confluences, bifurcations, inlets, and outlets. Across estuaries and braided rivers, scale asymmetry iis detected n links downstream of bifurcations, indicating geometric asymmetry which point to bifurcation stability. Estuaries tend to organize around a deep main channel whereas the channel networks of braided rivers are more evenly distributed across channel size. Analyses of flow direction in estuaries reveal that flood direction fluxes are more broadly distributed across the channel network, while ebb direction fluxes are more localized to the individual channels. The estuaries studied contain signatures of mutually evasive flood and ebb channels that are typical of alluvial estuaries, but also exhibit characteristics of branching or converging patterns typical of deltas and tidal networks, respectively. Finally, this presentation will offer perspectives on the state of the science for network analyses of channelized environments and present challenges for future research.
On-ice seismicity of a rapidly-rising jökulhlaup cycle at the A.P. Olsen Ice Cap, NE-Greenland
Authors: BInder Daniel , Mertl Stefan , Citterio Michele , Hillerup-Larsen Signe , Langley Kirsty , Walter Fabian , Eibl Eva P. S.
Published: March 2022

Rapidly-rising jökulhlaups, or glacial outburst floods, are a phenomenon with a high potential for damage. The initiation and propagation processes of a rapidly-rising jökulhlaup are still not fully understood. Seismic monitoring can contribute to an improved process understanding, but comprehensive long-term seismic monitoring campaigns capturing the dynamics of a rapidly-rising jökulhlaup are rare. In 2012, we installed a seismic network at the marginal, ice-dammed lake of the A.P. Olsen Ice Cap in NE-Greenland. Episodic outbursts from the lake cause flood waves in the Zackenberg river, characterized by a rapid discharge increase within a few hours. We deployed industrial geophones (4.5 Hz) for the five on-ice stations. Two stations were designed as mini-arryas with three vertical sensors, and the remaining were equipped with three-component sensors. All sensors were sunk about 3 m into the ice. Our 6 months long seismic dataset comprises the whole fill-and-drain cycle of the ice-dammed lake in 2012 and includes one of the most destructive floods recorded so far for the Zackenberg river. Seismic event detection reveals periods of high seismicity during enhanced surface melting prior to the outburst flood. During the outburst itself the number of detected events dropped due to the elevated seismic noise level. Furthermore, different beamforming methods were tested to infer back azimuth changes during periods of elevated seismicity. We propose that the changes of back azimuth are related to the subglacial infiltration of water and evaluate the role of the ice-dammed lake within this context.
Contribution of the Atlantic Ocean to European Heat Extremes
Authors: Hellmich Lara , Matei Daniela , Suarez-Gutierrez Laura , Müller Wolfgang A.
Published: March 2022

Mechanisms explaining the internal variability of mean summer temperatures have been

found on seasonal to sub- and multi-decadal timescales, but their contribution to variability

in extreme temperatures is not fully established. Here, we investigate the sub-decadal (5-

10yr) variability of European summer heat extremes and their potential drivers. By using

reanalyses (ERA5/ORA-20C) and the Max Planck Institute Grand Ensemble (MPI-GE), we

identify dominant timescales of temperature extremes variability over Europe. We are able

to link heat extremes over Central Europe with a southward development of a meridional

ocean heat transport anomaly over the North Atlantic (NA), starting about 6 years prior an

extreme event. This connection is reinforced by other variables such as ocean heat content

and atmospheric sea level pressure and jet stream displacement. The results indicate the

important role of the inertia of the NA for the occurrence of heat extremes over Europe, and

possibly help to improve their predictability several years ahead.
Climate Change and Spatio-temporal Trend Analysis of Climate Extremes in the Homogeneous Climatic Zones of Pakistan During 1962-2019
Authors: Khan Firdos
Published: March 2022

Different statistical methods and techniques are applied on observed station data to assess changes in temperature, precipitation and spatio-temporal trends analysis of climatic extremes over Pakistan during 1962-2019. The Mann-Kendal test demonstrates increasing precipitation (during DJF) and decreasing maximum and minimum temperatures (during JJA) at the meteorological stations located in the Karakoram region during 1962-1990. The decadal analysis, on the other hand, shows a decrease in precipitation from 1991 to 2019, as well as an increase in temperature (maximum and minimum) during 2010 to 2019, which is consistent with the recently observed slight mass loss of glaciers related to the Karakoram Anomaly. These changes are highly significant at 5% level of significance at most of the stations. In case of temperature extremes, summer days (SU25) increased except in zone 4, TX10p (cold days) decreased across the country during 1962-1990, with the exception of zones 1 and 2. TX90p (warm days) increased between 1991-2019, with the exception of zone 5, and decreases from 1962 to 1990, with the exception of zones 2 and 5. The spatio-temporal trend of consecutive dry days (CDD) indicates a rising tendency from 1991 to 2019, with the exception of zone 4, which shows a decreasing trend. PRCPTOT (annual total wet-day precipitation), R10 (number of heavy precipitation days), R20 (number of very heavy precipitation days), and R25mm (very heavy precipitation days) are considerably decreased (increasing) in North Pakistan during1962-1990 (1991-2019).

Keywords: Climate change, Climate extremes, Ground data, Mann-Kendal test, Karakoram anomaly.
Elucidating soil pore N2O production and consumption processes using isotope and microbial gene analysis: A depth profile approach
Authors: Minich Luisa I. , Barthel Matti , F. Conz Rafaela , Hüppi Roman , Wilde Benjamin C. , Werner Roland A. , Kuhn Thomas , Lehmann Moritz F. , Hagedorn Frank , Hartmann Martin , Scholten Thomas , Six Johan
Published: March 2022

N2O is a stratospheric ozone depleting substance and a potent greenhouse gas which significantly contributes to global warming. Although soils are the largest source of N2O emissions, knowledge gaps in the understanding of N2O production and reduction processes in soils still exist. Here, we investigated N2O production and consumption processes along soil depth profiles in a mesocosm experiment using natural-abundance N2O and NO3- isotopic signatures as well as abundances of soil microbial genes associated with N2O production (nirK, nirS) and reduction (nosZ). Soil columns either displayed undisturbed soil stratification (control treatments), or contained an artificial clay layer at 35 cm depth (clay treatment), which acted as a diffusion barrier and thus induced O2-limited conditions in deeper strata. We collected soil pore gas, soil solution and soil samples at five depths of the soil columns over the course of four weeks. In addition, we continuously monitored N2O fluxes at the soil surface and soil environmental parameters (oxygen, moisture, temperature) along the soil depth profiles. Microbial gene analysis in soil samples revealed similar abundances of nirK, nirS and nosZ in the two treatments across the entire soil depth profiles. The distribution of the functional genes was thus not indicative of enhanced N2O production and/or reduction in O2-limited conditions. However, lowest O2 concentrations below the clay layer were associated with highest 15N and 18O enrichments in both NO3- and N2O, indicating N2O production by denitrification and fractional N2O reduction. In addition, we found higher N2O concentrations and surface fluxes for the clay treatment. Our observations imply a dominance of N2O production over N2O reduction, even under conditions most favorable for complete denitrification.
r.survey: a tool to assess whether elements of specific sizes can be visually detected during field surveys
Authors: Marchesini Ivan , Bornaetxea Txomin
Published: March 2022

The concept of terrain visibility is vast and hard to summarise in a single definition. It can be generically said that it is a property that measures how observable a territory is from a single or multiple points of view. 

The estimation or calculation of visibility indices has been used in multiple fields, including architecture, archaeology, communications, tourism, land planning, and military applications. Recently (Meinhardt et al., 2015, Bornaetxea et al., 2018, Knevels et al., 2020, ) the concept of viewshed, i.e. the geographical area that is visible from one or more points of view, has been called into play for applications involving geomorphology.  In particular, it has been used to identify the portions of territory in which existing landslide inventories, carried out through field surveys, can be considered valuable for the calculation of landslide susceptibility. The aim is to delineate the Effective Surveyed Area, i.e. the area that has actually been observed by the operators in the field. 

However, this purely geometric approach cannot guarantee that objects are actually visible just because they are in a direct line-of-sight relationship with the observer. Due to their size and/or orientation in space, they may be (i) poorly or not at all detectable and/or (ii) observable from only a few viewpoints.    

For this reason we have developed r.survey (Bornaetxea & Marchesini, 2021), a plugin (Python script) for GRASS GIS, which allows to simulate (i) from how many observation points each point of the territory is visible, (ii) from which point of observation each point of the territory is most effectively visible, (iii) whether an object of a specific size can be detected. Concerning, in particular, the last element, r.survey calculates the solid angle subtended by a circle of equivalent dimensions to those of the object to be surveyed and assumed to be lying on the territory, oriented according to the slope and aspect derived from a digital terrain model. The solid angle provides a continuous measure of the visibility of the object sought, which can be compared with typical values of a human visual acuity. What happens then is that the concept of 'Effective Surveyed Area' can be reworked into the more accurate 'Size-specific Effective Surveyed Area' (SsESA). The new concept makes it possible to identify those portions of territory in which, during fieldwork, it is possible to observe objects of equal or greater size than those of interest, also considering their orientation in space with respect to the observer. 

The code of r.survey, which is based on the libraries and modules of GRASS GIS and was written to exploit multi-core processing, is open source and available for downloading (https://doi.org/10.5281/zenodo.3993140) together with a manual and some example data.
Unraveling the hydrology of water bodies in the African Sahel Region using continental scale remote sensing
Authors: Donauer Tabea , Ragettli Silvan , Molnar Peter , Delnoije Ron , Siegfried Tobias
Published: March 2022

Water resources in the African Sahel Region are under increasing pressure due to climatic changes, population growth and land degradation. Often, societies rely on surface water from lakes and rivers to sustain their lives and livelihoods. It is therefore essential to monitor and understand the dynamics of these water bodies to assess past, present, and future water resource changes.

Here we use satellite imagery and altimetry to determine water level and storage changes in small water bodies across the African Sahel. The method consists of detecting the ever-shifting edge of lakes and rivers in Landsat and Sentinel-2 optical imagery and assigning heights to shoreline points using altimetric data from ICESat-2satellite. This so-called “waterline method” assumes that the water-land boundary can be regarded as a contour line that connects points of equal elevation. We present novel extension of the waterline method which also allows to identify bathymetry changes over time from shoreline position observations. By tracking the temporal changes of surface water contour shapes, we can quantitatively analyse erosion and deposition processes. Past reservoir capacity changes and water storage variations are thus retrieved from optical remote sensing data, which are available over much longer periods of time and at higher revisiting frequenciesthan altimetry data.

The operational implementation of the method offers access to the water levels and storage variations of more than 300 water bodies in 10 Sahelian countries over the period 2000-2021. The identified spatio-temporal trends reveal fascinatingly heterogeneous patterns of drying and wetting across the Sahelian zone. Wet-season water level data reveal increasing trends over the last 20 years from West to East. Dry-season water availability then depends to a large degree on storage capacity.

Finally, we use the method for a detailed attribution analysis to identify drivers of change at Lac Wégnia, a designated RAMSAR site in Mali. The lake is characterized by an alarming decrease of dry-season surface water extent over the last 20 years. We recognize silting at the tributaries to the lake, but overall, erosion processes are dominant and threaten the persistence of the lake because of continuous backward erosion at the outlet of the lake. This explains the decreasing trend in water levels even for the wet-season, in spite of positive rainfall patterns.
Glacial erosion: controls and global distribution
Authors: Norris Sophie , Gosse John , Millan Romain , Mouginot Jeremie , Rabatel Antoine , Morlighem Mathieu , Bolton Matthew , Fast Julia , Alley Richard
Published: March 2022

Glacial erosion has often been parameterized as proportional to glacier sliding velocity, while the role played by local geology, hydrology and climate remain largely unquantified. As a result, our understanding of the links between global climate, tectonics and glacial erosion is limited. To address this shortcoming, we present a comprehensive synthesis of previously published Quaternary glacial erosion rates from six different measurement techniques integrated over 10-2 to 106 years: (i) instrumental measurements beneath active glaciers, (ii) sediment fluxes derived from meltwater streams or (iii) ice-marginal deposits, (iv) terrestrial cosmogenic nuclide dating (TCN), (vi) luminescence thermochronometry, and (v) relief generation of chronologically constrained surfaces. Our synthesis includes 1065 empirical data points and 465 erosion rates from ice sheets, ice caps, and topographically confined glaciers that range over six orders of magnitude, between 10-4 and 100 mm yr-1. Using a filtered dataset of contemporary erosion rates, we apply machine learning tools, using available environmental, glaciological, and geological datasets to assess the dominant controls on subgroups of nominal data categories.  On a global scale, while glacial sliding velocity is an important control, we also discover equally strong or stronger correlations between other glaciological, environmental, and lithological parameters and glacial erosion rate, some of which have not been previously documented. 

 
Magnetopause and bow shock models with machine learning
Authors: Ghisalberti Ambre , Aunai Nicolas , Michotte de Welle Bayane
Published: March 2022

The magnetopause (MP) and the bow shock (BS) are the two boundaries bounding the magnetosheath, the region between the magnetosphere and the solar wind. Their position and shape depend on the upstream solar wind and interplanetary magnetic field conditions.

Predicting their shape and position is the starting point of many subsequent studies of processes controlling the coupling between the Earth’s magnetosphere and its interplanetary environment. We now have at our disposal an important amount of data from a multitude of spacecraft missions allowing for good spatial coverage, as well as algorithms based on statistical learning to automatically detect the two boundaries. From the data of 9 satellites over 20 years, we identified around 19000 crossings of the BS and 36000 crossings of the MP. They were used, together with their associated upstream conditions, to train a regression model to predict the shape and position of the boundaries. 

Preliminary results indicate that the obtained models outperform analytical models without making simplifying assumptions on the geometry and the dependency over control parameters.
Antarctica ice sheet basal melting enhanced by high mantle heat
Authors: Artemieva Irina M.
Published: March 2022

Antarctica is losing ice mass by basal melting associated with processes in deep Earth and reflected in geothermal heat flux. The latter is poorly known and existing models based on disputed assumptions are controversial. Here I demonstrate that the rate of Antarctica ice basal melting is significantly underestimated: the area with high heat flux is double in size and the amplitude of the high heat flux anomalies is 20-30% higher than in previous results. Extremely high heat flux (>100 mW/m2) in almost all of West Antarctica, continuing to the South Pole region, and beneath the Lake Vostok region in East Antarctica requires a thin (<70 km) lithosphere and shallow mantle melting, caused by recent geodynamic activity. This high heat flux may promote sliding lubrication and result in dramatic reduction of ice mass. The results form basis for re-evaluation of the Antarctica ice-sheet dynamics models with consequences for global environmental changes. [Artemieva, I.M., 2022, Earth-Science Reviews]
New insights on avalanche release mechanics based on large-scale elastoplastic simulations 
Authors: Trottet Bertil , Simenhois Ron , Bobillier Grégoire , van Herwijnen Alec , Gaume Johan
Published: March 2022

The release of snow slab avalanches starts with the failure of highly porous weak snow layer buried beneath a cohesive snow slab leading to mixed-mode crack propagation along the slope. The first modelling attempt of the process date back to 1979 with a pure shear weak layer fracture assumption proposed by McClung. Later, Heierli extended the concept of anticrack, to account for weak layer volumetric collapse and subsequent slab bending. Recent advances reconciled these different approaches and have shown the existence of a supershear crack propagation regime leading to intersonic crack propagation speeds in the up and down-slope directions.
    
    In this work, based on the Material Point Method, finite strain elastoplasticy and critical state theory, we report a transition from sub-Rayleigh anticrack to supershear crack propagation involving the Burridge--Andrews mechanism. The existence of this transition is further confirmed by full-scale avalanche analyses. By accounting for slab fracture, we highlight that soft slabs can prevent supershear transitions to occur. In addition, it is shown that crack branching in the slab can either occur from top to bottom in the case of slow propagating anticracks or from bottom to top for supershear cracks. Through a sensitivity analysis, we investigate the conditions for crack arrest or for the so-called 'en échelon' slab fracture mechanism. Finally, full 3D simulations reveal interesting propagation and release patterns related to the interplay between cross-slope and down/up-slope propagation as well as slab tensile failure. This enables to analyse slab fracture modes at crown, flanks and staunchwall of the avalanche. These new findings allow us to reach a next step in our understanding of the avalanche release mechanics in order to predict both avalanche release shapes and sizes.
Compensating the absent or incomplete data required in vulnerability analyses via GIS. A case study on the surface geology and building stock of Iași City, Romania
Authors: Albulescu Andra-Cosmina , Necula Nicușor , Niculiță Mihai , Grozavu Adrian , Larion Daniela
Published: March 2022

Access to comprehensive and updated statistical and spatial databases represents a prerequisite of sound risk, hazard, vulnerability and resilience analyses, which have been advancing in terms of complexity and efficiency for the last 50 years, alongside the development of GIS techniques. Without adequate quantitative and qualitative datasets, research is sensitive to inaccurate and imprecise results, failing to meet the requirements for which it was designed and having zero input to the scientific progress.

Most developing countries - including Romania, face the problem of incomplete, inaccurate or outdated data in many fields of research, including geology-related fields and statistics about the building stock and transport infrastructure. These types of data are fundamental for vulnerability assessments of urban spaces to seismic or landslide hazards. This paper aims to provide a GIS-based methodology for acquiring datasets of the geological surface deposits and of the building stock at the scale of urban settlements, focusing on Iași City in the NE of Romania, respectively on the Țicău area of this city.

The mapping of geological surface deposits relies on automatic image analysis and landforms extraction algorithms that identify and delineate geological deposits based on slope and curvature, using High-resolution DEMs, as well as on cluster analysis. Slope deposits are delineated via watershed segmentation performed by Vision with Generic Algorithms (ViGRA), whereas the Schmidt-Hewitt classification is used to delineate floodplain and ridge deposits. The building stock is extracted from LiDAR point clouds with densities of 4 to 6 points per square meter using various approaches: neural network and deep learning for classification, and bounding rectangles for building boundary extraction. While LiDAR data is not available, high resolution imagery provided by the Copernicus programme can be used in conjunction with classification and edge detection algorithms to delineate building objects. The results are promising and show how the already available tools can be used to fill in the gaps of the “no-data problem” and overcome such a challenging issue. 

The obtained spatial data, namely surface deposits and building stock, become a major asset for the further vulnerability assessments that integrate geotechnical and physical aspects. This may help identify what local scale elements contribute to disaster resilience or, on the contrary, what fuels vulnerability.
Arctic summer sea-ice loss will accelerate in coming decades
Authors: Poltronieri Anna , Bochow Nils , Rypdal Martin
Published: March 2022

Every year, the area of the Arctic sea-ice decreases in the boreal spring and summer and reaches its yearly minimum in the early autumn. The continuous satellite-based time series shows that the September area has decreased from 4.5 x 106 km2 in 1979, to 2.8 x 106 km2 in 2020. The decline has been approximately linear in global mean surface temperature, with a rate of loss of 2.7 x 106 km2 per degree C of global warming.

In the CMIP6 ensemble, however, we find that the majority of the models that reach an Arctic sea-ice free state in the SSP585 runs show an accelerated loss of sea-ice for the last degree of warming compared to the second last degree of warming, which implies an increased sensitivity of the sea-ice to temperature changes. 

Both in the observational and CMIP6 data, we find that the decline in September sea-ice area is approximately proportional to the area north of which the zonal average temperature in spring and summer is lower than a critical threshold Tc. The Arctic amplification implies that the zonally averaged temperatures increase relative to the global temperatures, and with rates increasing with latitude. Linear extrapolation of the zonally averaged temperatures predicts that, with further warming, the September sea-ice area will depend non-linearly on global temperature, the sensitivity will increase and the September sea-ice area may become less that 1 x 106 km2 for global warming between 0.5 and 1.4oC above the current temperature. 

As a result of accelerated sea-ice loss, the average evolution of the sea-ice area among the CMIP6 models before the complete loss of the summer sea-ice shows an increase in the year-to-year fluctuations in minimum ice cover in the next decade. This implies exceptional accumulation of extreme events with very low or no sea-ice at all even before the final loss of the sea-ice. Likewise, an apparent short-term recovery of the sea-ice loss might be observable due to the increasing fluctuations. 
European Coastal Flood Awareness System (ECFAS): forecasting extreme coastal water-levels at European scale
Authors: Irazoqui Apecechea Maialen , Melet Angélique , Armaroli Clara , Ciavola Paolo , Fernandez Montblanc Tomas
Published: March 2022

European coasts are often exposed to severe storms that trigger extreme water-level conditions, leading to coastal flooding and erosion. With the objective to provide useful and timely information on coastal flood risk from extreme sea level events at European scale, a proof-of-concept for a European Coastal Flood Awareness System (ECFAS) is being developed as part of a European Union’s Horizon 2020 project. ECFAS could contribute to the evolution of the Copernicus Emergency Management Service.

ECFAS uses state-of-the-art coastal monitoring and forecasting technologies and datasets suited to regional-to-local scale assessments. For its early-warning component, ECFAS capitalizes on the ocean forecasting systems operated by the Copernicus Marine Service (CMEMS). Such forecasts are combined with a coastal-stretch-specific, pre-computed flood catalog to provide a mapping of the inundation depth and extent. Consecutively, the ECFAS-Rapid and Risk and Recovery Mapping component is activated which allows an operational assessment of the socio-economic impact of marine storms.

In this presentation, we focus on the skill of the CMEMS ocean hydrodynamic models that provide the marine hazard component to the system. We apply a methodology to detect storm-driven extreme sea level events from tide-gauge records and validate the event peak representation and forecast lead time impact. For best analyses, results show satisfactory results but a general underprediction of peak magnitudes of 10% for water levels and 18% for surges across the detected storm events. In average, the models are capable of independently flagging 76% of the observed events. Forecasts show insignificant lead time impact up to a 4-day lead time, demonstrating the suitability of the systems for early warning applications. Finally, by separating the surge and tidal contributions to the extremes, we identify the source of the prediction misfits and provide recommendations for the evolution of the CMEMS forecasting models for coastal flooding applications.

The ECFAS (European Coastal Flood Awareness System) project has received funding from the EU H2020 research and innovation programme under Grant Agreement No 101004211.
Catchment-scale geomorphological modelling of leaky dams using CAESAR-Lisflood
Authors: Wolstenholme Josh
Published: March 2022

Title: Catchment-scale geomorphological modelling of leaky dams using CAESAR-Lisflood

 

Joshua Wolstenholme              j.wolstenholme-2018@hull.ac.uk          1

David Milan      d.milan@hull.ac.uk      1

Christopher Skinner    chris.skinner@environment-agency.gov.uk 2

Daniel Parsons              d.parsons@hull.ac.uk               1

 

Affiliations:

University of Hull, Energy and Environment Institute, United Kingdom of Great Britain – England, Scotland, Wales (j.wolstenholme-2018@hull.ac.uk)

Environment Agency, Flood Hydrology Improvements, United Kingdom of Great Britain – England, Scotland, Wales

 

The introduction of large wood to fluvial systems is becoming increasingly popular as a method of natural flood management commonly referred to as leaky dams. These are often installed as semi-permanent features through live felling and anchoring in-situ. Currently, most natural flood management modelling is hydrological and focuses on flood risk without accounting for geomorphology of these ‘fixed’ features. We argue that the long-term effectiveness of NFM interventions require and understanding of the nested hydrogeomorphological processes at work within river catchments, particularly those related to bed scour, sediment transport and deposition, and the associated feedbacks following implementation of leaky dams. Leaky dams that are designed to attenuate the hydrograph and ‘slow-the-flow’, may cause sediment storage as well as scour, potentially impeding the effectiveness of a leaky dam to reduce flood risk after a single storm event. Using the new ‘Working with Natural Processes’ toolbox developed for CAESAR-Lisflood, the influence of different storm scenarios on a series of leaky dams in a hypothetical catchment based on a site in North Yorkshire is assessed. The effectiveness of the model at representing the influence of the dams on hydrogeomorphology is also assessed.
Simulating extreme cold spells in France with empirical importance sampling
Authors: Cadiou Camille , Yiou Pascal
Published: March 2022

Extreme winter cold spells in Europe have huge societal impacts. Being able to simulate worst case scenarios of such events for present and future climates is hence crucial for adaptation. Rare event algorithms have been applied to simulate extreme heatwaves. They have emphasized the role of the atmospheric circulation in such extremes. The goal of this study is to test such algorithms to extreme cold spells.
We focus on cold spells that occur in France since 1950. The analysis is based on the ERA5 reanalysis. We select cold events that have occurred for different time scales (10 days, 1 month, 3 months). We identify record shattering cold events for time scales of 1 and 3 months (in 1956 and 1963). We find that, although the frequency of extreme cold spells decreases with time, their intensity is stationary.
We applied a stochastic weather generator approach with importance sampling, to simulate the worst cold spells that could occur every year since 1950, with lengths of 1 month and 3 months. We hence simulated ensembles of worst winter cold spells that are consistent with observations. Those worst cases are slightly colder than the record shattering events, and do not yield the trend that is observed on the mean temperature. The atmospheric circulation that prevails during those events is analyzed and compared to the observed circulation during the record breaking events.
Addressing tradeoffs beyond disciplinary borders: HYDROpot_integral as a tool to simultaneously assess hydropower potential and ecological potential 
Authors: Hug Peter Dorothea , Wechsler Tobias , Weingartner Rolf , Zappa Massimiliano
Published: March 2022

The steadily growing demand for energy and the simultaneous pursuit of decarbonization are increasing interest in the expansion of renewable energies worldwide. Hydropower produces around 60% of Switzerland's electricity and plays a key role in this energy transition strategy. However, habitat and ecosystem protection and climate friendly renewable energy production are sometimes at odds. While the environmental impact is usually addressed at some level, there is a lack of standardization and tools for a global assessment are still scarce. The GIS-based tool HYDROpot_integral allows the consideration of the total hydropower potential as well as the ecological potential of a region. Based on ecological and socio-economic geodata, both the current state of each river reach and the hydropower potential is assigned a rank. To record the suitability, every river reach is ranked according to their ecological, cultural and economic ecosystem services. A low rank means that a river reach is more suitable for hydropower production at low cost in terms of ecological and cultural ecosystem services; a high rank indicates high ecological and cultural ecosystem services and low economic services and is therefore more suitable for protection. As the limit between hydropower use and protection is adjustable, different scenarios can be explored. Results from five mesoscale test catchments in Switzerland show the feasibility of the present method, to provide a comprehensive and meaningful basis that can support the decision-making process. Overall, the assessment method is to be understood as a flexible tool to address tradeoffs between hydropower potential and ecological potential.
Making sense of urban DAS data with clustering of coherence-based array features
Authors: Grimm Julius , Poli Piero
Published: March 2022

Seismic noise monitoring in urban areas can yield valuable information about near-surface structures and noise sources like traffic activity. Distributed Acoustic Sensing (DAS) is ideal for this task due to its dense spatial resolution and the abundance of existing fiber-optic cables below cities.
A 15 km long dark fiber below the city of Grenoble was transformed into a dense seismic antenna by connecting it to a Febus A1-R interrogator unit. The DAS system acquired data continuosly for 11 days with a sampling frequency of 250 Hz and a channel spacing of 19.2 m, resulting in a total of 782 channels. The cable runs through the entirety of the city, crossing below streets, tram tracks and a river. Various noise sources are visible on the raw strain-rate data. A local earthquake (1.3 MLv) was also recorded during the acquisition period.
To characterize the wavefield, the data is divided into smaller sub-windows and coherence matrices at different frequency bands are computed for each sub-window. Clustering is then performed directly on the covariance matrices, with the goal of identifying repeating sub-structures in the covariance matrices (e.g. localized repeating noise sources). Finding underlying patterns in the complex dataset helps us to better understand the spatio-temporal distribution of the occurring signals.
Spatial and temporal variability of soil respiration in an irrigated olive grove in southeastern Spain
Authors: Aranda-Barranco Sergio , Serrano-Ortiz Penelope , Kowalski Andrew Stephen , Sanchez-Cañete Enrique
Published: March 2022

Olive grove management entails environmental and socio-economic repercussions for the Mediterranean region. Maintaining bare soil in alleys is the most common management in this crop, but its implications for soil respiration (Rsoil) are not well understood. Although previous studies have quantified Rsoil at specific moments, soil respiration has not yet been continuously measured in olive groves. In this study a complete year of Rsoil  measurements was taken in an irrigated olive grove in southeast of Spain. To avoid spontaneous weed growth a glyphosate-based herbicide was periodically applied. Six automated soil CO2 efflux chambers with additional sensors of soil temperature (T) and soil water content (SWC) were controled by a multichamber monitoring system (Li-8100A, Li-cor). With the aim of know the spatial variability in Rsoil and facilitate scaling up to estimate ecosystem soil respiration, 3 chambers were installed under the olive tree canopy and 3 chambers in the alleys.

Preliminary results show that Rsoil increased in the warmer months and decreased in the colder months as expected. Also, daily Rsoil values under the trees are normally several times higher than in the alleys but this ratio changed with the seasons. In warm months, daily Rsoil under the tree was 2-3 times higher than daily Rsoil in the alley, while in cold months (like January) it was 6 times higher. In the alleys, diurnal variability was detected in Rsoil except in winter. While Rsoil under the trees was practically constant throughout the day during the year except in summer when there appears to be a relationship with the decrease in the flux of photosynthates in environments with high VPD. In spring Rsoil-alleys was double at midday versus night-time. Additionally, a positive and a negative relationship was established with temperature and SWC respectively. On the other hand, we found no clear relationship for Rsoil under the tree with respect to T or SWC. These preliminary results suggest a considerable Rsoil component of total ecosystem respiration influenced by the tree which does not depend on changes in T and SWC and that should be included in the partition models.
A numerical study on the thermo-mechanical response of deformable fractured systems to advective-diffusive heat transport
Authors: De Simone Silvia , Pinier Benoit , Bour Olivier , Davy Philippe
Published: March 2022

Geothermal energy applications involve heat circulation in naturally fractured reservoirs, which are in general difficult to characterize due to the multiscale complexity of the fracture network and therefore the flow. In this context, numerical modeling is key to forecast the performance of geothermal energy applications under a number of scenarios. Numerical modeling is challenging because fractures represent the main pathway for flow and advective transport, but diffusive thermal exchange with the host rock controls the geothermal performance - the two processes occurring on very different length and time scales. Moreover, the host rock cooling provokes thermal contraction which tends to increase the fracture aperture, with direct effects on the flow and the advective transport. Quantify these processes is crucial but in general computational demanding when dealing with large reservoirs with hundreds of thousands of fractures.

In this study we present a novel methodology to simulate thermo-mechanical (TM) heat transport. The method is based on the particle tracking approach in Discrete Fracture Networks (DFN) and it has been implemented in the DFN.Lab software platform. The contribution of the host rock matrix in terms of diffusive heat exchange and thermal contraction/expansion is analytically evaluated, which directly impacts the fracture aperture and therefore the advective heat transfer. The methodology enables investigating the reservoir behavior and optimizing the geothermal performance while keeping the computational effort within reasonable values. Results from simulations of cold fluid injection show that rock contraction accelerates the advective transport resulting in a faster recovery of cold fluid at the outlet. We analyze systems of fractures with different characteristics (density, aperture, geometrical patterns, ...) and we identify the parameters that mostly impact the TM response.
Spatial scales of internal variability of annual mean all-sky and clear-sky surface solar radiation: quantitative estimates using CMIP6
Authors: Chtirkova Boriana , Folini Doris , Ferreira Correa Lucas , Wild Martin
Published: March 2022

Internal variability, a natural source of uncertainty in climate projections, is important when one wants to distinguish between the forced signal and the random noise in the climate system. The downwelling surface solar radiation, a key climate variable, has been shown to exhibit unforced trends (i.e. trends exclusively due to internal variability) even on decadal timescales. These long-term unforced trends interfere with the forced signal and contribute to the decadal variations of SSR, known as global dimming and brightening. A common technique in observation analysis, which serves to reduce the contribution of internal variability and therefore give a better estimate of the forced signal, is the use of composite time series of multiple locations (averaging in space). We use annual mean data of 49 models from the pre-industrial control experiment of the Coupled Model Intercomparison Project – Phase 6 (CMIP6) to give a quantitative estimate of how much the system noise is reduced upon spatial averaging. We find that globally the standard deviation σ (which is proportional to the magnitudes of random trends) is reduced almost linearly with the horizontal grid increment Δx in the range 2 – 15 degrees. On coarser resolutions, deviations from a linear fit are observed, possibly because the patterns of ocean oscillations are not concentrated in compact forms in space. Comparing the rate of reduction of the noise with grid resolution (dσ/dΔx), we find that the noise in all-sky SSR is averaged out ~10 times faster (with increasing Δx) than the noise in clear-sky SSR. Numerical values estimated from the CMIP6 multi-model median and uncertainties estimated from the inter-model spread are dσ/dΔx = -0.11 ± 0.03 Wm-2/deg for all-sky SSR and dσ/dΔx = -0.01 ± 0.004 Wm-2/deg for clear-sky SSR. The all-sky SSR global mean σ for a 0.5 deg grid is 4.79Wm-2, while for clear-sky it is 0.66 Wm-2. Furthermore, dσ/dΔx is strongly dependent on the geographical location, being more than twice as large in China, compared to Europe for both all-sky and clear-sky SSR.
Remote sensing of trace gases as link between small and large scale pollution sources in the Ruisdael Observatory
Authors: Heimerl Katharina , Houweling Sander , Eeuwijk Lars , van der Plas Wim , Limburg Rob J. , Hensen Arjan , van den Bulk Pim , Scheeren Bert
Published: March 2022

Greenhouse gases like CO2 and CH4 play an important role in the earth’s energy budget. Both local sources and long range transport can influence their concentration in the atmosphere. Within the Ruisdael project, which aims to map and understand the atmosphere over the Netherlands in a changing climate, a trailer was fitted with a range of instruments for flexible operations within the Ruisdael Observatory measurement network, among them an EM27/SUN, on which we will focus here. This instrument is a portable Fourier transformation infrared spectrometer to measure the columnar abundance of the trace gases CO2, CH4 and CO from the spectral absorption of direct sun light. The additional CO measurements can provide valuable information for attributing CO2 and CH4 enhancements to either biological processes or fuel burning. The instrument was equipped with a custom build rain cover that is fixed to the moving sun tracker and set up for remote operation, which greatly increased data coverage. It was then installed on the roof of the Ruisdael trailer, along with several in situ instruments inside.

The EM27 was deployed in the Ruisdael trailer at the Cabauw tall tower site from May till September 2021. The RITA (Ruisdael Land-Atmosphere Interactions Intensive Trace-gas and Aerosol measurement campaign) campaign took place in and around the Cabauw tower in September 2021. During this time, additional measurements in the boundary layer by a mobile truck and an aircraft give the possibility of separating local and regional influences on the columnar trace gas abundance. Here, we present the results from the columnar trace gas measurements in the context of the large scale circulation and the in-situ measurements at the tower, with the mobile truck, and by aircraft. While the in situ measurements capture local pollution very well, only the larger pollution plumes are distinguishable in the EM27 data. The CO2 columnar abundance is mostly influenced by the large scale circulation. In the columnar abundance of CH4 and CO, larger pollution plumes are distinguishable as increases of up to several ppb. The presented measurements demonstrate how the EM27 can help to distinguish influences of local emissions and large scale transport in an urban monitoring network.