bluuebunny/crossref_metadata_2025 huggingface dataset:
Pressure balance at the subsolar magnetopause: Statistical study
Authors: Grygorov Kostiantyn , Nemecek Zdenek , Safrankova Jana , Simunek Jiri
Published: March 2022

The magnetopause would be located at a point where the total pressure on the solar wind/magnetosheath side is equal to its magnetospheric counterpart. The upstream pressure is a sum of plasma thermal pressure and magnetic pressure whereas the magnetic pressure would strongly dominate on the magnetospheric side because the density of magnetospheric plasma is typically very low. Statistics of over ten years of THEMIS subsolar magnetopause (YGSM<5 RE) observations reveals that about 2 % of magnetopause crossings exhibit notably higher magnetic field in the magnetosheath than within the magnetosphere and thus the pressure balance is apparently violated. On the other hand, long series of multiple crossings suggest that the magnetopause is close to its equilibrium position and upstream and downstream pressures should be about equal. Interestingly, such crossings were found under both polarities of IMF BZ. In the paper, we study possible sources and mechanisms keeping the pressure balance. We discuss namely the upstream solar wind conditions and state of the outer magnetosphere. Comparison of these unusual magnetopause crossings with the rest of them shows that the cold plasma population coming to the magnetopause from the plasmasphere during periods of geomagnetic storms plays an important role in setting the pressure balance in the magnetopause region.
Enhancing anticipatory actions for disaster preparedness considering physical and social factors
Authors: Block Paul , Lala Jonathan , Bazo Juan
Published: March 2022

Climate and weather-related disasters are increasingly expensive and deadly. Hydrologic catastrophes are especially devastating, accounting for over half of all disasters and global disaster victims. Novel approaches are desperately needed for vulnerable communities subject to hydrologic and water-related crises. Post-disaster assistance is a crucial component of disaster relief, however the potential for reducing humanitarian impacts through anticipatory, pre-disaster planning and actions cannot be overstated.  Short-term early warning systems are common, yet hydrologic forecasts at monthly or seasonal scales are relatively underused to guide preparatory actions, despite their potential value. Empirical evidence suggests that pre-disaster actions can reduce loss of life and property and result in cost savings for relief and governmental organizations. Such interventions often flow through water management systems, highlighting the central role of water resources decision-making in hazard resilience.

Various humanitarian relief agencies have recently developed operational early action protocols, conditioned on forecasts and risk analysis, outlining trigger criteria and identifying early actions. Concurrently, an extensive number of subseasonal-to-seasonal climate forecast products are now available to derive hydrologic forecasts. Thus there exists significant potential to tailor subseasonal-to-seasonal hydrologic forecast products to appropriately trigger a suite of preparedness actions and decisions across multiple lead times.  Various frameworks exist to understand pareto trade-offs in actions and financing, including community-based constraints and preferences.  These approaches respond to the strong demand for large-scale, multi-sectoral hydrologic forecast and management tools to enable early preparedness for anticipated drought and flood extremes.
A multi-method and multi-model approach for predicting spatio-temporal patterns of sap flow, xylem isotopic composition, and water ages in the critical zone
Authors: Klaus Julian , Chun Kwok Pan , Fabiani Ginevra , Fresne Maëlle , Hrachowitz Markus , McGuire Kevin , Moussa Adnan , Penna Daniele , Pfister Laurent , Rodriguez Nicolas , Schoppach Remy , Sulis Mauro , Zehe Erwin
Published: March 2022

Vegetation exhibits critical feedback with runoff generation. Trees show distinct water uptake patterns relying on soil water from different depths and groundwater with a mixture of water sources that is commonly very different from runoff in terms of age distribution and isotopic composition. Here we present a multi-method and multi-model approach to study the spatio-temporal patterns of sap flow and age distribution of tree water uptake and streamflow in a headwater catchment (mixed forest, 43 ha). For this, we monitored sap flow spatially distributed at >30 trees over two years, sampled 2H and 18O bi-weekly and spatially distributed in xylem for two years and in streamflow sub-daily for four years. This was supplemented by tritium sampling in streamflow over two years for different flow stages. We used statistical modeling to determine spatio-temporal patterns of transpiration and isotopic composition of xylem water and their drivers. We used a multi-model approach to derive catchment travel times through (i) composite Storage Selection (SAS) functions, (ii) conceptual hydrological modeling, and (iii) coupled land surface-subsurface modeling (ParflowCLM) combined with particle tracking. Statistical data analysis revealed that tree species, tree diameter, and topographic wetness index at the tree location were the main driver of spatial variability of sap flow, while soil water was the main source of xylem water with little groundwater influence. The travel time modeling showed a strong seasonal and event-based variability of travel times and allowed to include information on vegetation behavior with different complexity. Last, our detailed sampling of vegetation offers a blueprint for a sampling strategy of isotopes in xylem water for travel time studies. Our data revealed that approximately 20 sampled trees are sufficient to capture the mean isotopic value of xylem water of a species at our study site, while we needed around 100 samples to detect landscape influence on the xylem isotopes needed for considering spatial patterns in the travel time analysis. Our results underline the feedbacks between vegetation and runoff generation and show their relevance for better simulating catchment travel times.
Mapping Blue-Green infrastructure to evaluate conditions in the Estonian coastal zone 
Authors: Kaskevich Volha , Villoslada Peciña Miguel , Ward Raymond , Sepp Kalev
Published: March 2022

Blue-Green Infrastructure (BGI) is a framing concept concerning the connectivity of ecosystems, founded on nature-based solutions and a multi-functionality approach, which includes contributions by nature to disaster risk reduction, infrastructure resilience, erosion control, land formation, and other ecosystem services (World Risk Report, 2012). The study reviews the potential of areas of BGI to mitigate climate change (EEA Report, 2009) and produces maps showing fragmentation areas along the Estonian coast using UAVs and satellite imagery. This allows a more detailed and objective evaluation of the indicators of the conservation state and potential improvement of future connectivity between BGI elements, ensuring coverage of appropriate protection status for coastal habitats. Reliable estimation and understanding of the ecological integrity of habitats and species on the effectiveness of the Natura 2000 network, including analysis of valuable coastal areas to define missing indicators and formulate essential markers for its resilience in Estonia. A disconnected series of inefficiently managed natural components produce far fewer public benefits than they have the potential for.

A comprehensive study of the Estonian coastal zone is based on Estonian legislation, Integrated Coastal Zone Management, the CORINE Land Cover (CLC) system, natural protected areas (NPA), the Estonian Green Network, Agricultural Registers, and Information Board (ARIB), Natura 2000, and benthic habitats datasets that apply to land use regulation in the development planning process to identify the appropriate intensity of land-use and conflicts of interest to be resolved. National BGI strategies, either independently or integrated into broader national policies, identify blue and green assets, corridors, and areas of particular importance outside protected areas that would help the policy instruments. Estonia has been actively planning a blue-green infrastructure approach since 1983, at least in the ecological network sense on a national level, and elaborates the model into a comprehensive plan and implementation program.

 
Inter-annual Variability in the Subpolar Overturning Circulation: A Sensitivity Analysis
Authors: Khatri Hemant , Williams Richard , Woollings Tim , Smith Doug
Published: March 2022

We employ multi-ensemble Met Office Decadal Prediction System hindcasts to analyse the impact of atmospheric winds and North Atlantic Oscillation (NAO) phases on the overturning circulation in the North Atlantic Ocean. A positive NAO phase is generally associated with an anomalously strong and/or northward shifted jet stream in the North Atlantic, and the vice-versa is true for a negative NAO phase. As a consequence of relatively strong winds, oceans tend to lose more heat to the atmosphere in winter in many parts of the subpolar North Atlantic Ocean. This process is expected to create negative anomalies in sea surface temperature and generate more dense water on the ocean surface at high latitudes resulting in a strengthening in the overturning circulation. Here, we examine the sensitivity of the overturning circulation to NAO phases in multi-ensemble decadal hindcasts to understand how the interior ocean responds to different NAO phases. For this purpose, we analyse the changes in east-west density contrasts, upper ocean heat content, mixed-layer depth, meridional heat and salt transport in different oceanic regions, i.e. Labrador Sea, Irminger Sea and Nordic Seas. In particular, we perform a linear regression analysis for the above-mentioned diagnostics and NAO indices to assess how sensitive the upper ocean is to changes in the atmospheric state. We further compare our results against reanalysis data and in-situ observations.
Detection of Time Variable Gravity Signals using Terrestrial Clock Networks
Authors: Vincent Asha , Mueller Juergen , Wu Hu
Published: March 2022

Local gravity potential variations can be determined from the frequency differences of high-performance optical clocks at different locations. Case studies for three regions affected by different mass change processes - Himalaya, Amazon and Greenland - provide promising results. Time-varying gravity signals can be observed with clocks that achieve fractional frequency uncertainties of 10-18 corresponding to 0.1 m2/s2 in gravity potential variation. As the clocks rest on the deformable earth surface, clock observations do not only include potential variations due to mass changes but also associated variations due to the vertical deformation of the land. For the simulations, vertical displacements were derived from real GNSS measurements, and mass variations were computed from GRACE solutions. In the Himalayan region, seasonal variations with a maximum range of [-0.2 0.2] m2/s2 were obtained. There, early and long-lasting precipitation patterns in North East India and the gradual spreading towards the West can be potentially observed by a dedicated clock network. In the case study for the Amazon region, seasonal variations with a maximum range of [-0.5 0.5] m2/s2 to be observed by clocks also reveals the Amazon’s seasonal secrets of annual rainfall variability at the north and south of the equator. The rainy season in the north of the equator is during the summer season from June to August, but from November to April in the south of the equator. The long-term trend of the ice mass loss in Greenland between 2004 and 2015 causes signals of potential variations of 1 m2/s2 that again can be observed by clock measurements. Especially, the higher rates of potential mass variations in the west and south parts of Greenland can well be observed. These examples illustrate impressively that terrestrial clock networks can be used as a modern tool for detecting various time-variable gravity signals for understanding the local patterns of the variations and for providing complementary information.    

Acknowledgment: 

This study has been funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy EXC 2123 Quantum Frontiers - Project-ID 90837967 and the SFB 1464 TerraQ - Project-ID 434617780 within project C02. 
Large biases in hydrography and circulation of the Arctic Ocean in CMIP6 models
Authors: Heuzé Céline , Zanowski Hannah , Karam Salar , Muilwijk Morven
Published: March 2022

Climate models are our best tools to quantify ongoing changes caused by the climate crisis, but they are not perfect. The Arctic Ocean is particularly challenging to simulate: complex circulation flowing through narrow gateways and around tortuous bathymetry, dense water cascading off the steep shelf break, slow exchanges in canyons, along with known biases in sea ice and neighbouring seas.

We investigate the Arctic Ocean in the historical run of 14 distinct models that participated to the latest Climate Model Intercomparison Project phase 6 (CMIP6) and find large biases in temperature, salinity, density, and depth of critical water masses, both on the shelves and in the deep basins. The biases are consistent throughout the water column and throughout the Arctic, with correlations often exceeding 0.9. However, no significant trend is observed in these biases, suggesting that the deep basins of the Arctic are not correctly ventilated already at the level of the Atlantic Water.

Using the subset of models that submitted the age of water output, we confirm this absence of ventilation by dense water overflows: the overflows occur at too few locations and are diluted at shallow depths.   

Work is ongoing to relate these biases to the relevant processes, the upper water column, and fluxes through the various Arctic Ocean gateways.
Connecting the North Atlantic subpolar gyre and the northern European shelf seas: a satellite-based Lagrangian perspective
Authors: Eisbrenner Ezra , Chafik Léon , Döös Kristofer
Published: March 2022

Understanding the impact of oceanic climate variability on shelf seas requires knowledge of their water-mass origins and associated pathways. Furthermore, identifying the dominant driving mechanisms responsible for water-mass variability is an important step towards better predictability of shelf sea properties. To determine the link between the large-scale circulation of the subpolar North Atlantic and the North Sea, we adopt a Lagrangian approach based on satellite altimetry. Utilizing the derived velocities, we are able to isolate the changes of water-mass pathways in response to decadal large-scale oceanic variability. In particular, during phases of a strong subpolar gyre we find that water-masses which are transported into the North Sea follow a comparatively direct path along the subpolar gyre, as well as being faster.  Subsequently, northern North Sea water-masses originate from further west in the southern and central subpolar North Atlantic. Supportive analysis on high resolution reanalysis data suggests that not only strong gyre regimes but also the transient phase into them are connected to pronounced along-shelf advection. In contrast, phases of a weak subpolar gyre lead to increased water-mass residence times in the north-eastern North Atlantic, prior to entering the North Sea. We conclude that the subpolar gyre strength is a key predictor of inter-annual variability of North Sea water-mass pathways, origin, and properties.
When does structural connectivity measure hydrologic connectivity in semi-arid vegetated landscapes?   
Authors: Crompton Octavia , Katul Gabriel
Published: March 2022

In dryland ecosystems, connectivity of bare soil patches is recognized as a key pattern attribute controlling resource conservation and structure-function relationships.  Runoff redistribution from bare to vegetated patches concentrates water, enhancing vegetation growth and biomass. Conversely, a reduction in vegetation patches can lead to highly connected bare patches, triggering a threshold-like response with a large increase in hillslope runoff.  Patterns of dryland vegetation are often used as indicators of landscape vulnerability, and there is increasing interest in using vegetation indices to predict connectivity-mediated abrupt shifts.  One of the challenges to this goal lies in relating structural measures of connectivity – e.g., Flowlength – to functional measures, such as the source-to-sink path length of flow or the contributing source area.  To address this challenge, a series of virtual runoff experiments on a patchily vegetated hillslope is presented with varying length scales and spatial configurations of vegetation, and rainfall intensity and duration.  Particle tracer methods are used to relate (i) the runoff coefficient to the contributing source area, and  (ii) Flowlength as a measure of structural connectivity to source-sink path lengths, as a measure of functional connectivity.  The results suggest a power-law relation between runoff coefficient and contributing source area that is stable across storm and vegetation characteristics.  The relation between Flowlength and functional connectivity varies between storm intensities and durations, and is strongest for low-intensity storms.   The results have practical implications for tracer studies, and support incorporating rainfall intensity into the use of vegetation patterns to predict landscape stability thresholds. 

 
How investigating the physics of avalanche-obstacle interaction with DEM can help to calculate the avalanche impact pressure on obstacles
Authors: Kyburz Michael Lukas , Sovilla Betty , Gaume Johan , Ancey Christophe
Published: March 2022

Calculating snow avalanche impact pressure is an essential task for safe construction and hazard mapping in mountainous regions. Although avalanche-obstacle interaction crucially depends on the flow regime, practitioners mostly assume that impact pressure is similar to the dynamic pressure in inviscid fluids, that is, it is proportional to the square velocity weighted by an empirical drag coefficient. When fitting this coefficient to field measurements, one does not end up with a unique value, but with a range of possible values that cover more than one order of magnitude. In the absence of a physics-based framework, setting the right drag coefficient requires good working knowledge and experience from practitioners. Indeed, even for trained engineers it may be unclear how the impact pressure depends on the expected flow regime, on obstacle width, or on terrain configuration. To address these questions, we simulate the avalanche impact pressure on obstacles of varying geometry for four distinct avalanche flow regimes using the Discrete Element Method and a cohesive contact model. The results allow us to quantify the influence of the obstacle width and shape on the average impact pressure, as well as the detailed pressure distribution on the obstacle surface. Furthermore, we propose a novel method for estimating the drag coefficient based on simple geometrical considerations and key characteristics of avalanche flow. Our results are validated using experimental data from the Vallée de La Sionne test site, and make a step forward in the derivation of a physics-based framework for computing snow avalanche impact pressures for varied flow regimes depending on obstacle shape and dimensions.
The Estuary as a Natural Water Treatment Plant for Microplastics
Authors: Wu Nan , Spencer Kate , Grieve Stuart , Manning Andrew
Published: March 2022

Microplastics (MPs) are becoming an important component of suspended particulate matter (SPM), especially in estuaries which are hotspots of MPs pollution. Most SPM in estuarine water are removed via flocculation and further deposited. Therefore, we hypothesise that there is an efficient removal process for MPs by flocculation, which are expected to decrease the overall load of MPs in the marine environment. Here we systematically studied and quantified the influence of MPs properties (size, shape, density, polymer type and weathering condition) on flocculation behavior with suspended sediment in estuary conditions. 

We chose over 20 types of MPs with different properties for 8 size ranges from (10-300 µm for fragments and microbeads, and 10-1000 µm in length for microfibers, respectively). The MPs with different properties and suspended sediment were flocculated in artificial seawater, and the MPs in the system were observed using fluorescence microscopy to distinguish the incorporated MPs and suspended MPs. The incorporation rate (IR) is the ratio of incorporated MPs to total MPs, which is the parameter to evaluate the interaction between MPs and flocs.

The IR decreased with increasing size for fragments and microbeads, and also decreased as the diameter of microfibers rose. The IR for fragments smaller 20 µm is extremely high, from 94.8% to 100%, but gradually decreased with increasing size. For fragments larger than 200 µm, the IR of Polyethylene (PE), Polypropylene (PP) and Polystyrene (PS) are lower than 20%, while higher than 50% for Polyethylene terephthalate (PET) and Polyvinyl chloride (PVC). The IR of PE microbeads is significantly lower than those of fragments. When the diameter of microfibers are smaller than 20 µm, the IRs are always higher than 90%, and the length has no effect on IR. While the IR of microfibers decreased with the length increasing when the diameter of microfibers is larger than 30 µm. According to extensive comparisons between 20 types of MPs, we found that the IR is normally higher in the small size, elongated, angular, high density, weathered, chemically active MPs, while lower in the large size, spherical, low density, pristine and chemically inactive MPs. The size plays the most important role, followed by shape.

There is an evidence that MPs are likely to be removed from the water column and hence estuary sediments are important sinks for MPs. This process reduces overall load to marine environments, but this is selective and depends on the characteristics of MPs. This study offers a reference to predict the preferential removal behavior of MPs in the estuary.
The Role of Biofilm on the Fate of Emerging Organic Compounds: Numerical Modelling of Column Experiments
Authors: Behle Vera , Rodríguez-Escales Paula , Sanchez-Vila Xavier
Published: March 2022

Managed Aquifer Recharge (MAR) is a technology to deal with water stress and water scarcity worldwide. Depending on the origin and degree of prior treatment, the water inflow in MAR facilities contains measurable concentrations of Emerging Organic Compounds (EOCs). Understanding the processes that influence the fate of EOCs in the aquifer is therefore a key point for evaluating and predicting contaminant plumes and risk assessment. Such fate is clearly linked to the presence of biofilms that develop mainly in the first centimeters of the aquifer. Yet, the link between microorganisms, the development of biofilm and the fate of contaminants is not well understood. The spatial distribution into different redox states and thus the taking place of the different redox reactions, which significantly influence the degradation of pollutants as well as the sorption of these substances, is an important point. Sorption takes place in two different phases, the sediment and the biofilm. We have used the results of some conducted column experiments to create a numerical model, with which the processes taking place can be viewed in a differentiated manner and investigated further. The results show that biofilm plays an important role as a sorption phase and should therefore not be neglected when investigating and evaluating the fate of pollutants.
Evidence for lithospheric and sublithospheric anisotropy of the eastern Canadian Shield and its margins
Authors: Darbyshire Fiona
Published: March 2022

The eastern Canadian Shield and its margins represent an excellent natural laboratory to study the formation and evolution of continental lithosphere, as the rocks and structures preserve approximately 4 billion years of geological history. The core of the continent is made up of several large Archean cratonic blocks and continental fragments, welded together by Paleoproterozoic mobile belts. Subsequent Proterozoic orogenesis added to the southern and eastern margins, building the Laurentian landmass, and a series of Wilson cycles established the form of the continent we see today. Laurentian lithosphere is characterized in seismic tomography by a thick, seismically fast continental keel, representing cold temperatures and a depleted composition, whereas the Phanerozoic margins have slower seismic wavespeeds and a thinner lithosphere.

Over the last several decades, numerous seismic anisotropy measurements have been used to investigate lithospheric and sublithospheric fabrics beneath the region. Shear wave splitting shows strong lateral variability in both the strength and fast-polarisation orientation of the anisotropy, and measurements at closely-spaced stations suggest a significant lithospheric component as well as a likely sublithospheric contribution. Recent regional and continental-scale surface wave tomography studies allow for some depth constraint on the azimuthal anisotropy, which appears pervasive, but varying, for different depth ranges within the lithosphere and asthenosphere.

We compare the measurements from shear wave splitting and surface wave tomography with several geological and geophysical observations that could relate to anisotropic fabric, such as surface tectonic boundaries, magnetic anomalies, absolute plate-motion directions and mantle flow patterns from global geodynamic models. We use these comparisons to investigate the relative contributions to the seismic anisotropy observed across the region from lithospheric deformation, basal shear of the North American plate, and active mantle convection.
Multi-hazard stress testing framework for quantifying climate-related Value at Risk for water utilities
Authors: Becher Olivia , Pant Raghav , Hall Jim
Published: March 2022

Water utility assets are particularly vulnerable to the impacts of climate change, from multiple climate-related hazards including droughts, floods and hurricanes. There are increasingly calls for disclosure and reporting of physical climate risks to companies, but dependable probabilistic risk estimates are challenging for companies whose asset networks extend over large areas and are subject to multiple hazards. Here we examine the financial impact of present and future (mid-century projections under RCP2.6, 4.5 and 8.5 warming scenarios) climate extremes on the national water supply utility in Jamaica. The potable water supply system is stress tested with a large set of spatially coherent hurricane, drought and pluvial and fluvial flood events, combining observed events with synthetic statistical and model-based events. The water utility’s assets (reservoirs, pumping stations, treatment works, etc.) are embedded in a system model, which also represents water usage for municipal use, loss through leakage and major storage dynamics in the supply network. For each disruptive event, the number of water users impacted is computed. The financial loss incurred by the utility is estimated as the sum of cost of disruption (cost of tankering water and lost tariffs during disruptions/periods of asset reconstruction post event) and the expected cost of asset reconstruction. An expected Value at Risk (VAR), both at present and in future scenarios, is estimated by integrating over the probabilistic event set. The calculation is an extension of the established framework for catastrophe loss modelling used by insurers. We show how climate-induced, widespread water supply disruptions translate into the VAR of a utility’s balance sheet. As water utilities are largely state-owned enterprises, these impacts impose a major burden on the fiscal budget. Therefore, the framework presented provides a basis for identifying interventions that promote both water infrastructure and fiscal resilience.
The role of crustal accretion variations in determining slab hydration at an Atlantic subduction zone 
Authors: Allen Robert , Collier Jenny , Henstock Tim
Published: March 2022

We present a 2D P-wave velocity model from across the outer rise region of the Lesser Antilles island arc, the first wide-angle seismic study of outer rise processes at an Atlantic subduction zone. The survey consists of 46 OBS receivers over a 174 km profile with velocities resolved up to 15 km below top basement. The final velocity model, produced through tomographic inversion, shows a clear decrease in the velocity of the lower crust and upper mantle of the incoming plate as it approaches the trench. We interpret this drop as due to outer rise bend-related hydration, similar to Pacific cases, but superimposed on spatial variations in hydration generated at the slow-spreading ridge axis. In thin, tectonically controlled crust formed under magma poor spreading conditions the superposition of these two sources of hydration results in compressional velocities as low as 6.5 kms-1 beneath the PmP reflector, with a slow velocity anomaly extending to ~10km below top basement. In contrast, segments of crust interpreted as having formed under magma rich conditions show velocity reductions and inferred hydrous alteration more like that observed in the Pacific. Hence, variations in the style of crustal accretion, which we observe on 50-100 km length scales both along and across isochrons, is a primary control over the distribution of water within the slab at Atlantic subduction systems, in contrast with Pacific subduction zones where the fast-intermediate spreading lithosphere being subducted is more structurally uniform. This heterogeneous pattern of water storage within the slab, which is further complicated by along strike variations in outer rise bending, subducting fracture zones and deformation at segment ends may have important implications for our understanding of long-term patterns of hazard at Atlantic subduction systems.
Decadal variability of the extratropical response to the Madden-Julian Oscillation
Authors: Skinner Daniel , Matthews Adrian , Stevens David
Published: March 2022

It is known that the Madden-Julian Oscillation (MJO) excites a response in the behaviour of many extratropical weather regimes at lag times of one to two weeks, acting as a key predictor in weather forecasting. Less well understood, however, is the robustness of these responses over long time scales. We begin by taking a statistical approach to assess the boreal winter response of a selection of key extratropical systems (e.g. North Atlantic Oscillation (NAO), Pacific North American (PNA) pattern) to the MJO, over two non-overlapping time periods (1974-1997 and 1997-2019). It is shown that there is significant change in both the magnitude and structure of the extratropical response signal, as a function of lag, between the two periods.

This is followed by a similar analysis applied to the 1100 year pre-industrial control run of the UKESM-1-0 coupled climate model. By breaking this period into separate 20 year segments and comparing the extratropical responses to the MJO in each segment, we show that although there is a predictable mean signal, it is overwhelmed by the internal variability in the system. Repeating this methodology with segments between 10 and 40 years in length allows us to assess sampling errors and identify the key timescales for the variability. A similar mean signal is seen with every segment length, justifying the current use of the MJO as a predictor in the extratropics, although the variability in segments of 30 and 40 years (common time periods used in many historical analyses) casts doubt on the reliability of these predictors for the future.

Recent process based analysis has shown that El Niño Southern Oscillation (ENSO) can act to modulate the Rossby wave source associated with the MJO. We investigate this using our statistical approach to assess the impact of ENSO on the MJO teleconnection patterns. In addition to this, we consider lower-frequency modes, for example Atlantic Multidecadal Variability (AMV) and the Pacific Decadal Oscillation (PDO). By compositing the extratropical response to the MJO over positive and negative phases of each of these modes, we see the individual impact of each low-frequency on the MJO teleconnections. Our work suggests updating the current MJO-extratropical predictors to include consideration of the decadal atmospheric and oceanic basic state.
Three-dimensional velocity variations due to ice mass changes in Greenland – Insights from a compressible glacial isostatic adjustment model
Authors: Steffen Rebekka , Steffen Holger , Huang Pingping , Tarasov Lev , Kjeldsen Kristian K. , Khan Shfaqat A.
Published: March 2022

The lithospheric thickness beneath and around Greenland varies from a few tens of kilometres in offshore regions to several tens of kilometres (up to 200 – 250 km) in land areas. But, due to different datasets and techniques applied in geophysical studies, there are large differences between the different geophysical lithosphere models. As an example, lithosphere models from seismological datasets show generally larger values (above 100 km), while models using gravity or thermal datasets tend to be thinner (values mostly below 100 km). To model the deformation associated with the melting of the Greenland Ice Sheet a detailed lithosphere model is required. Nevertheless, seismologically obtained lithosphere models are the ones usually applied in these so-called glacial isostatic adjustment (GIA) models. Besides, GIA models can be used to provide additional constraints on the lithospheric thickness.

Results from most 3D GIA models are compared to observed vertical velocities only, while horizontal velocities are known to be sensitive to the lateral variations of the Earth (e.g., lithospheric thickness). But, horizontal velocities from incompressible GIA models, which are commonly used, are not suitable due to the neglect of material parameter changes related to the dilatation. Compressible GIA models in turn can provide more accurate estimates of the horizontal and vertical viscoelastic deformations induced by ice-mass changes. Here, we use a variety of lithospheric thickness models, obtained from gravity, thermal, and seismological datasets, in a three-dimensional compressible GIA Earth model. The GIA model will be constructed using the finite-element software ABAQUS (Huang et al., under review in GJI) and applying recent ice history models Huy3 and GLAC-GR2a for Greenland in combination with the Little Ice Age deglaciation model by Kjeldsen et al. (2015). We will compare various lithosphere models, including their impact on the modelled 3D velocity field, and compare these against independent GNSS (Global Navigation Satellite System) observations.

References:

Huang, P., Steffen, R., Steffen, H., Klemann, V., van der Wal, W., Reusen, J., Wu, P., Tanaka, Y., Martinec, Z., Thomas, M. (under review in GJI): A finite element approach to modelling Glacial Isostatic Adjustment on three-dimensional compressible earth models. Geophysical Journal International. Under review.

Kjeldsen, K., Korsgaard, N., Bjørk, A. et al. (2015): Spatial and temporal distribution of mass loss from the Greenland Ice Sheet since AD 1900. Nature 528, 396–400, https://doi.org/10.1038/nature16183.
Correlated Magnetic Field Dropouts and Plasma Wave Activity at Switchback Boundaries as Observed by Parker Solar Probe
Authors: Rasca Anthony , Farrell William , MacDowall Robert , Bale Stuart , Kasper Justin
Published: March 2022

The first solar encounters by the Parker Solar Probe revealed the magnetic field to be dominated by short field reversals in the radial direction referred to as "switchbacks."  While radial velocity and proton temperature were shown to increase inside the switchbacks, B exhibits very brief dropouts only at the switchback boundaries.  Brief intensifications in spectral density measurements near the electron plasma frequency, fpe, have also been observed at these boundaries, indicating the presence of plasma waves triggered by electron beams.  We perform a correlative study using observations from the Parker FIELDS Radio Frequency Spectrometer (RFS) and Fluxgate Magnetometer (MAG) to compare occurrences of spectral density intensifications at the electron plasma frequency (fpe intensifications) and B dropouts at switchback boundaries during Parker's first and second solar encounters.  We find that only a small fraction of minor B dropouts are associated with fpe intensifications.  This fraction increases with B dropout size until all dropouts are associated with fpe intensifications.  This suggests that in the presence of strong B dropouts, electron currents that create the perturbation in B along the boundaries are also stimulating plasma waves such as Langmuir waves.
A Fully Kinetic Perspective on Weakly Active Comets: Symmetric versus Asymmetric Outgassing
Authors: Deca Jan , Stephenson Peter , Divin Andrey , Henri Pierre , Galand Marina
Published: March 2022

For more than two years, ESA’s Rosetta mission measured the complex and ever-evolving plasma environment surrounding comet 67P/Churyumov-Gerasimenko. In this work, we explore the structure and dynamics of the near-comet plasma environment at steady state, comparing directly the results of a spherically symmetric Haser model and an asymmetric outgassing profile based on the measurements from the ROSINA instrument onboard Rosetta during 67P’s weakly outgassing stages. Using a fully kinetic semi-implicit particle-in-cell code, we are able to characterise (1) the various ion and electron populations and their interactions, and (2) the implications to the mass-loading process caused by taking into account asymmetric outgassing. Our model complements observations by providing a full 3D picture that is directly relevant to help interpret the measurements made by the Rosetta Plasma Consortium instruments. In addition, understanding such details better is key to help disentangle the physical drivers active in the plasma environment of comets visited by future exploration missions.
How drought affects flood risk: positive / negative effects and feedbacks in different cases
Authors: Van Loon Anne , Barendrecht Marlies , Weesie Ruben , Mendoza Heidi , Matanó Alessia , Koehler Johanna , Rohse Melanie , de Ruiter Marleen , Mazzoleni Maurizio , Ward Philip , Aerts Jeroen , di Baldassarre Giuliano , Day Rosie
Published: March 2022

Droughts are long-lasting and have a range of cascading impacts on society. These impacts and their responses can influence the further development of the drought itself, but also continue into the period after the drought ended. Especially if society is hit by a next hydrological extreme event, heavy rainfall resulting in flooding, the effects of this may be increased or decreased by the preceding drought and its impacts and responses. We here present a review and a global assessment of cases of these events, based on scientific literature, NGO and governmental reports, and newspaper articles, to study the diversity of how drought affects flood risk. We find that the balance between the positive and negative effects of extreme rainfall after a long dry period is mostly dependent on the underlying vulnerability and the effect of specific responses, and is different for different countries, and for different sectors and groups in society. Based on our initial analysis of the collection of case studies, we see some emerging patterns. For example, in Europe, the USA and Australia, the highly managed water system with hard infrastructure and early-warning systems makes that in most cases the rainfall after drought are managed and adverse effects mitigated, but also lock-ins exist that can make feedbacks of either inaction or maladaptation result in increased economic losses. In Africa and Latin-America, with a fragile governance system, less hard infrastructure, and a more exposed population, extreme rainfall after drought brings relief and replenishment of water resources, but also increased impacts, conflict and displacement. Here, we hypothesise that impacts are unequally distributed in society, because of issues of power, access to land and water resources, inadequate soft infrastructures, etc. We will test this hypothesis with an in-depth qualitative study of local stakeholder knowledge of these human-water processes in selected case studies. The typology of drought-to-flood events that we developed can serve as a starting point for further research on the complexity of these cascading events.
First evidence of carbon escape through Venus magnetosheath along draped magnetic field lines
Authors: Hadid Lina ,   MSA, MIA and MEA teams
Published: March 2022

On August 10, 2021, the Mercury-bound BepiColombo spacecraft flew for the second time by Venus for a Gravity-Assist Maneuver. During this second flyby of Venus, a limited number of instruments were turned on, allowing unique observations of the planet and its environment. Among these instruments, the Mass Spectrum Analyzer (MSA) that is part of the particle analyzer consortium onboard the magnetospheric orbiter (Mio) was able to acquire its first plasma composition measurements in space. As a matter of fact, during a limited time interval upon approach of the planet, substantial ion populations were recorded by MSA, with characteristic energies ranging from about 20 eV up to a few hundreds of eVs. Comparison of the measured Time-Of-Flight spectra with calibration data reveals that these populations are of planetary origin, containing both Oxygen and Carbon ions. The Oxygen observations are to some extent consistent with previous in situ measurements from mass spectrometers onboard Venus Express and Pioneer Venus Orbiter. On the other hand, the MSA data provide the first ever in situ evidences of Carbon ions in the near-Venus environment at about 6 planetary radii. We show that the abundance of C+ amounts to about ~30% of that of O+. Furthermore, the fact that photoelectrons are simultaneously observed with the low energy planetary ions indicate a magnetic connection to the dayside ionosphere from which ions are ejected under the effect of the ambipolar electrostatic field.
The Sensitivity of Simulated Streamflow to Individual Hydrologic Processes Across North America
Authors: Mai Juliane , Craig James R. , Tolson Bryan A. , Arsenault Richard
Published: March 2022

Streamflow sensitivity to different hydrologic processes varies in both space and time. In numerical modeling of streamflow, this sensitivity manifests as parameter sensitivity, which is typically model-specific.

In this study, we apply a novel analysis over more than 3000 basins across North America enabling the estimation of the process sensitivities on streamflow based on basin characteristics that can be derived from physiographic and climatologic data without needing to perform the expensive sensitivity analysis itself. This continental-scale analysis allows for high-level conclusions as to the importance of water cycle components on streamflow predictions, as the analysis considers a flexible model structure rather than an individual model. This work derives the sensitivity of streamflow simulation to entire hydrologic processes rather than only specific parameters. Process sensitivities are computed and provided for each day of the year over a wide range of physiographic and climatologic regimes, enabling future hydrologic model improvement at the continental scale.

A few highlight results are: 1) Baseflow and other sub-surface processes are of low importance across North America- especially when time points of high flows are of interest. 2) Percolation, evaporation, and infiltration show very similar patterns with increased importance in South-eastern US and west of the Rocky Mountains. 3) Up to 30% of the overall model variability can be attributed to snow melt in regions that are snow dominated (Northern Canada and Rocky mountains). Potential melt shows a similar gradient as snow melt with sensitivities of above 60% in the Province of Quebec and the Rocky Mountains. 4) Direct runoff (quickflow) is the most sensitive of all hydrologic processes- especially in South-Eastern US it is responsible for more than 80% of the model variability. 5) The derived functional relationship to estimate the process sensitivities based on basin characteristics has predictive power of at least 0.8 in Pearson correlation coefficients based on more than 1000 basins used for validation.
Groundwater vulnerability of megacity under changing climate and land use scenarios
Authors: Lakshminarayanan Balaji , Ramasamy Saravanan , Karuppanan Saravanan
Published: March 2022

Rapid urbanization and climate change pose a serious threat to the groundwater resource of urban regions in terms of contamination and excessive groundwater abstraction. To understand and protect groundwater resources from anthropogenic activities, an index-based vulnerability assessment model which integrates future climatic variables and land use (LU) is needed. This study attempts to identify the impact of climate and land use change on future groundwater vulnerability of rapidly urbanizing South Asian city, Chennai Metropolitan Area (CMA), India using DRASTIC-LU model under RCP4.5 and RCP8.5 scenarios for near (2020-2035) and far future period (2035 - 2050). The dynamic variables of the DRASTIC-LU model such as depth to groundwater - D, net recharge - R, and land use - LU were projected using regional climatic models and land change modeler. Three regional climatic models (RCMs) namely ICHEC-EC-EARTH, MIROC-MIROC5, and CNRM-CERFACS-CNRM-CM5 were compared and selected using Taylor’s diagram. The ICHEC-EC-EARTH model was found to perform better than the other two RCMs for this region and was used to project future climatic variables under RCP4.5 and RCP8.5 scenarios for two future periods (4 scenarios). Terrset land change modeler (LCM) was used to project future land use for the years 2030 and 2050. Vulnerability condition of the base period (2018) was assessed using nitrate concentration and vulnerability indices, the developed DRASTIC-LU model produces an accuracy of (AUC = 0.796). The projected groundwater vulnerability depicts an increase in vulnerability area from the base period as 21.41%, 30.09%, 20.98%, and 22.01% for scenario-1,2,3 and 4 respectively. Variation in precipitation pattern contributes to change in future net recharge and groundwater level and increased built-up region, i.e, change in land use attributes to increase in future groundwater vulnerability. Based on future vulnerability analysis, it is identified that the CMA groundwater system is in critical condition of high vulnerability for near and far future periods. 