bluuebunny/crossref_metadata_2025 huggingface dataset:
Deep-mixing and deep-cooling events in Lake Garda: Simulation and Mechanisms
Authors: Biemond Bouke , Amadori Marina , Toffolon Marco , Piccolroaz Sebastiano , van Haren Hans , Dijkstra Henk
Published: March 2021

A calibrated three-dimensional numerical model (Delft3D) and in-situ observations are used to study the relation between deep water temperature and mixing in Lake Garda (Italy). A model-observation comparison indicates that the model is able to adequately capture the production of turbulent kinetic energy in the surface layer and its vertical propagation during unstratified conditions. Here, the model is used as a support to identify the main processes causing deep water cooling and deep mixing in the lake. The analysis indicated that two processes cause mixing over the entire depth. The first process is thermocline tilting due to strong and persistent winds. This is found to generate a temporary disappearance of stratification followed by vertical mixing over the entire depth. The second process is turbulent cooling, which arises as a combination of negative-buoyancy produced by surface cooling and turbulence injection from strong winds. Turbulent cooling acts when vertical temperature gradients are absent over the whole depth and cools and mixes the lake over its entire vertical. The third identified process is associated to differential cooling between the shallow southern part and the deep northern trunk. This generates the advection of cold water from the southern, colder and well-mixed basin to the norther trunk along the sloping bottom of the lake. Such differential cooling is found to be a consequence of the turbulent cooling and is not associated with mixing over the entire depth in the northern trunk. Available observations indicate that the three processes identified from the model indeed occur in Lake Garda. Long- term simulations of deep water temperature and related deep mixing appear to be very sensitive to the atmospheric forcing, whose accurate reproduction is essential for the prediction of the future occurrence of deep mixing events.
Ocean Heat Transport’s Response to Future Climate Projections
Authors: Mecking Jennifer , Drijfhout Sybren
Published: March 2021

This study investigates the response of the meridional Ocean Heat Transports (OHT) to future climate projections in both CMIP5 and CMIP6 models.  Globally the OHT transport is declining/becoming more southward across all latitudes in the Northern Hemisphere, while at latitudes south of 10°S the OHT is icreasing/becoming more northward.  These changes in OHT are much stronger in CMIP6 models relative to CMIP5, especially for the rcp2.6/ssp126 scenario relative to the rcp85/ssp585 scenario.   Throughout the entire Atlantic basin the northward heat transport is reduced and can be tied to the velocity driven overturning (Atlantic Meridional Overturning Circulation (AMOC)) contribution to the OHT.  While the temperature driven changes in the Atlantic basin dampen the changes in the OHT.  In the Indo-Pacific basin the OHT transport north of the equator does not change much since the temperature and velocity driven changes balance each other.   However, south of the equator the increase in northward heat transport is caused by the overturning velocity driven changes and again dampened by temperature driven changes.  These changes in the Indo-Pacific basin can be tied to changes in wind driven subtropical overturning cells.
Changes in surface level NO2 in the UK during the COVID-19 pandemic compared to predicted 2020 concentrations and the impact on O3.
Authors: Evans Rhianna , Lee James , Drysdale Will
Published: March 2021

Governments worldwide have used non pharmaceutical interventions known as lockdowns to contain the spread of the coronavirus pandemic, leading to a mass reduction in road traffic and international travel as working from home becomes the new normal. As a result, primary emissions of nitrogen oxides are expected to have largely decreased. A study of the UK’s first lockdown (Lee et al. 2020) used historical averages, taken between 2015 and 2019, as a baseline for comparison. This method is simplistic however does not fully account for the year to year meteorological variation. The UK’s first national lockdown was announced on 23rd March 2020 extending to 31st May 2020 and by mid-April traffic was reduced by 70% compared to normal according to the Department for Transport. We examined NO2 and O3, measured by the UK’s Automatic Urban and Rural Network for the year 2020 consisting of 65 urban traffic and 61 urban background sites, for the lockdown period from 2000 to 2020. Between 2000 and 2019 NO2 decreased by an average of 0.88 and 0.49 μg m-3 per year at urban traffic and urban background sites respectively. In 2020, the lockdown caused a 20 μg m-3 decrease in NO2 at urban traffic sites, an equivalent of 26 years at the previous rate.

To improve on the previous method, we have constructed random forest models to simulate business as usual NO2 and O3 concentrations at AURN sites in 9 cities, allowing changes in meteorology to be fully accounted for. These simulations were then compared to lockdown measurements in 2020. We observed an average 55% decrease in NO2 however O3 concentrations were elevated with an average 29% increase. The total oxidant, Ox, (sum of NO2 and O3) experienced marginal change (< 1%) indicating the changes in NO2 and O3 were largely due to photochemical repartitioning. This has highlighted the importance of O3 in urban locations in a future low NOx environment in the UK when electric vehicle fleets are adopted. 

 

Lee et al., Atmos. Chem. Phys., 2020, 20, 15743 – 15759
Stable isotope profiles of soil organic carbon in forested and grassland landscapes in the Lake Alaotra catchment (Madagascar): insights in past vegetation changes.
Authors: Razanamahandry Vao Fenotiana , Dewaele Marjolein , Govers Gerard , Brosens Liesa , Campforts Benjamin , Jacobs Liesbet , Razafimbelo Tantely , Rafolisy Tovonarivo , Bouillon Steven
Published: March 2021

Madagascar is an island characterized by a sharp vegetation gradients in landscape and the extent to which the central highlands were once covered by forest is still under debate. Stable carbon isotope ratios have been an important tracer to understand vegetation shifts in a landscape over time because forest plants (following the C3 photosynthetic pathway) and grasses (following the C4 pathway for the majority of tropical and subtropical species) show a different degree of isotope fractionation. The main aim of this study is to provide insight into the past vegetation history of the grasslands in the Lake Alaotra region (central Madagascar). This region is under high anthropogenic pressure as it is the most important rice-producing region in Madagascar. While much of the Lake Aloatra catchment consists of grassland-covered hills, with a high density of lavaka (large erosional features), pristine forests are located just east of the lake and these form the most western part of a larger rainforest-covered region extending up to the east coast of the island. Soil profiles were sampled along the hillslope gradient at both forested and grassland sites, whereby carbon stocks were quantified and δ13C values of soil organic carbon (OC) were measured to find evidence for past forest vegetation in the grassland sites. The soil organic carbon content of grassland soil profile was extremely low, from 0.4 to 1.8% in the top layer and rapidly decreasing to 0.2 % below 100 cm depth. The current vegetation predominantly consists of C4 grasses (δ13C ~-13 ‰), yet soil δ13C-OC ranges between -25.9 and -16.6‰, and most profiles show a decrease in δ13C-OC with depth, in contrast to observations in the (C3-dominated) forest profiles, which show a typical enrichment in 13C with depth. δ13C values in grassland and forest profiles converge to similar values (within 2.1 ±1.8 ‰) at depths below ~80cm, suggesting that the grasslands in the Lake Alaotra region have developed on formerly forested soils. Moreover, the soil OC stock of grasslands was ~55.6% lower than along the forested hillslopes for the upper 30 cm layer. Our results are consistent with the hypothesis that a vegetation change has occurred in the lake Alaotra region, and offer a promising avenue to expand this approach on a wider scale to help understand the vegetation cover change in the central highland of Madagascar.
The Influence of Input Data on Flood Risk Estimates
Authors: Sieg Tobias , Thieken Annegret
Published: March 2021

The management of risks arising from natural hazards requires a reliable estimation of the hazards’ impact on exposed objects. The data sets used for this estimation have improved during the recent years reflecting an increasing amount of detail with regard to spatial, temporal or process information. Yet, the influence of the choice of data and the degree of detail on the estimated risk is rarely assessed.

We estimated flood damage to private households and companies for a flood event in 2013 in Germany using two different approaches to describe the hazard, the exposed objects and their vulnerability towards the hazard with varying levels of detail. One flood map is based on local flood maps computed by the European Joint Research Center not including embankments, while the other flood map was derived especially for this particular flood event. Exposed elements are mapped using the land use based data set BEAM (Basic European Asset Map) and with an object-based approach using OpenStreetMap data. The vulnerability is described by ordinary Stage-Damage-Functions and by tree-based models including additional damage-driving variables. The estimations are validated with reported damage numbers per federal state and compared to each other to quantify the influence of the different data sets at various spatial scales.

The results suggest that a stronger focus on exposed elements could improve the reliability of impact estimations considerably. The individual assessment of the influence of the different components on the overall risk points out promising next steps for further investigations.
Fracture network connectivity devolution monitoring using transdimensional data assimilation
Authors: Somogyvári Márk , Jalali Mohammadreza , Engelhardt Irina , Reich Sebastian
Published: March 2021

In fractured aquifers, the permeability of open fractures could change over time due to precipitation effects and hydrothermal mineral growth. These processes could lead to the clogging of individual fractures and to the complete rearrangement of flow and transport pathways. Existing fractured rock characterization techniques often neglect this dynamicity and treat the reconstruction as a static inversion problem. The dynamic changes then later added to the model as an independent forward modeling task. In this research we provide a new data assimilation-based methodology to monitor and predict the dynamic changes of fractured aquifers due to mineralization in a quasi-real-time manner.

We formulate the inverse problem as a dynamic ‘hidden Markov process’ where the underlying model dynamicity is just partly known. Data assimilation methods are specifically designed to model such systems with strong uncertainties. A typical example for such problems is weather forecasting, where the combination of nonlinear processes and the partial observations make the forecasting challenging. To handle the strong random behavior, data assimilation approaches use stochastic algorithms. In this study we combine DFN-based stochastic aquifer reconstruction techniques with data assimilation algorithms to provide a dynamic inverse modelling framework for fractured reservoirs. We use the transdimensional DFN inversion of (Somogyvári et al., 2017) to initialize the data assimilation. This method uses a transdimensional MCMC approach to identify the most probable DFN geometries given the observations. Because the method is transdimensional it can adjust the number of model parameters, the number of fractures within the DFN. We developed this idea further by enhancing a particle filter algorithm with transdimensional model updates, allowing us to infer DFN models with changing fracture numbers.

We demonstrate the applicability of this new approach on outcrop-based synthetic fractured aquifer models. To create a dynamic DFN example, we simulate solute transport in a 2-D fracture network model using an advection-dispersion algorithm. We simulate fracture sealing in a stochastic way: we define a limit concentration above which the fractures could seal with a predefined probability at any timestep. At the initial timestep, a hydraulic tomography experiment is performed to capture the initial aquifer structure, which is then reconstructed by the transdimensional DFN inversion. At predefined timesteps hydraulic tests are performed at different parts of the aquifer, to obtain information about new state of the synthetic model. These observations are then processed by the data assimilation algorithm, which updates the underlying DFN models to better fit to the observations.
Modelling moving force of tectonic plates with the use of length of day variation
Authors: Fodor Csilla , Varga Péter
Published: March 2021

The nature, the age and probably first of all the magnitude of driving forces of plate motion since long are a subject of scientific debates and it cannot be regarded as clarified even today.

The physical basis of recent plate tectonics is characterized by interaction between plates by viscous coupling to a convecting mantle.  Authors are going to demonstrate that changes in the Earth's axial rotation can affect the movement of tectonic plates, and the phenomenon of tidal friction is able to shift the lithospheric plates.

The tidal friction regulates the length of day (LOD)and consequently also the rotational energy of the Earth. It can be investigated with the use of total tidal energy, which can be determined as a sum of three energies (energy of axial rotation of the Earth, Moon’s orbital energy around the common centre of mass and the mutual potential energy). It was found that during the last 3 Ga the Earth lost 33% of its rotational energy. The LOD 0.5Ga BP (before present) was ~21 h. This means that the rotational energy loss rate was 4.1 times higher during the Pz (Phanerozoic, from 560 Ma BP to our age) than earlier in the Arch (Archean, 4 to 2.5 Ga BP) and Ptz (Proterozoic 2.5 to0.56 Ga BP). The low-velocity zone (LVZ) at 100-200 km depth interval, close to the boundary between the lithosphere and the asthenosphere characterized by a negative anomaly of shear wave velocities. Consequently, the LVZ can result in a decoupling effect. Tidal friction brakes the lithosphere and the part of the Earth below the asthenosphere with different forces. By model calculation, we show that this force difference is sufficient to move the tectonic plates along the Earth’s surface.  

Reference: Varga P., Fodor Cs., 2021. About the energy and age of the plate tectonics, Terra Nova. (in print) https://doi.org/10.1111/ter.12518
On the connection between spectral bandwidth and dynamic properties of breaking waves
Authors: Cao Rui , Callaghan Adrian
Published: March 2021

An experimental investigation on dispersively focused 2-D deep-water breaking wave groups with JONSWAP type spectra is presented. Specifically, this paper describes the role of spectral bandwidth (as determined by the peak enhancement factor of the spectra, γ) on several properties of breaking wave groups such as the evolution of spectral energy magnitude and distribution, changes in bandwidth, energy dissipation and its rate, and the breaking strength parameter b. These parameters are examined in the context of two definitions of wave group spectral slope (or just slope),  Ss and Sp. The first, Ss, incorporates the role of spectral bandwidth in its definition, where Sp does not consider any explicit bandwidth effect.

Our results show that the spectrally-distributed magnitude of energy loss due to breaking, relative to the peak frequency of the underlying wave group, is broader for broad banded breakers, than for narrow banded breakers, where the energy loss is more concentrated around the peak frequency. In terms of changes to bandwidth post-breaking, it is found that the bandwidth of narrower banded wave groups is more likely to be widened as a result of breaking. For a given wave slope definition, the breaking onset is affected by the spectral bandwidth - broad banded wave groups break at relatively lower values of wave slope, and result in a higher fractional loss at a given value of wave slope.

The laboratory results indicate that the absolute energy loss and its rate are linearly related to wave slope, and that data scatter is reduced when the bandwidth is explicitly incorporated into the definition of wave slope (Ss). In addition, we find that scatter in the fractional wave energy loss as a function of wave slope is also reduced when Ss  is used compared to Sp, again indicating the important role of bandwidth in the breaking process. Furthermore, the collapse of the data from breaking wave groups with different bandwidths can be further improved by accounted for the breaking onset in the definition of wave slope. Finally, a quasi-linear dependence of b on bandwidth-dependent wave slope is found, in general agreement with the numerical work of Derakhti and Kirby (2016).
Variability in rainfall information derived from collocated microwave links
Authors: Špačková Anna , Bareš Vojtěch , Fencl Martin
Published: March 2021

In the field of hydrology, there is a significant demand for high spatial-temporal resolution of rainfall information that can be met by commercial microwave links (CMLs). CMLs are commonly used as a backhaul of telecommunications network with favourable spatial coverage especially in urbanized areas. CMLs are point-to-point radio connections operating at frequencies where attenuation of electromagnetic waves can be related to the rainfall intensity.

The ability of CMLs to assess rainfall intensity is determined by hardware parameters and path lengths of CMLs. The CML operates at various frequencies with horizontal or vertical polarization, moreover, link paths have lengths ranging from hundreds of meters up to kilometres. The characteristics of the rainfall needs to be reflected as they have impact on the errors (de Vos et al., 2019). Even collocated CMLs can detect considerably dissimilar rainfall information. To increase effectivity of rainfall information retrieval it is crucial to understand uncertainties arising from diversity of CML characteristics.

This study evaluates collocated CMLs that are assumed to be affected by the same weather condition. Having identical CML characteristics (as well as the propagations of the signals), it is expected to observe the same response patterns in the attenuated signals. Any disagreement could be caused by random error, sensitivity to the rainfall intensities, and/or hardware reaction to the condition (e.g. sensitivity of the antenna radome to the rainfall splash). Therefore, the role of arrangement of the direction of rainfall field advection and position of the collocated link paths is considered. The magnitude of disagreement between different groups of collocated links could be specified based on their characteristics. Oppositely, for collocated links under the same conditions but with different characteristics, the attributes of the individual CMLs are suspected for the disagreement.

 

References

de Vos, L. W., Overeem, A., Leijnse, H., and Uijlenhoet, R. (2019). Rainfall Estimation Accuracy of a Nationwide Instantaneously Sampling Commercial Microwave Link Network: Error Dependency on Known Characteristics. Journal of Atmospheric and Oceanic Technology 36, 7, 1267-1283. https://doi.org/10.1175/JTECH-D-18-0197.1

 

This study was supported by the project SpraiLINK 20-14151J of the Czech Science Foundation.
Assessing the future occurrence of severe thunderstorm environments in Europe: frequency, hotspots and impacts
Authors: Pons Flavio , Faranda Davide
Published: March 2021

We study the future frequency of atmospheric environments leading to severe thunderstorms over Europe under different climate change scenarios in CMIP5 models. Our method is founded on dynamical system theory, which makes it possible to detect future atmospheric configurations that are close analogues of past events in the class of interest.

We rely on the EM-DAT and the European Severe Weather Database to select an ensemble of past events leading to significant damage or disruption, including severe thunderstorms, hail storms, derechos and tornadoes, between 1950 and 2020. We consider the geopotential height field at 500 hPa in ERA5 data as a dynamical proxy of the corresponding configurations. Then, we leverage extreme value theory to detect close dynamic analogues in the output of CMIP5 climate projection models under two emission scenarios, namely RCP4.5 and RCP8.5.

First of all, we assess possible differences between the trends in severe weather frequency due to different radiative forcing. Then, we study the spatial structure of such trends, highlighting regions where the occurrence of such phenomena could see a sharp increase or decrease. Finally, we estimate potential future impact of such phenomena where the information about economic damage is available in EM-DAT.

 
Soil apparent electrical conductivity and must carbon isotope ratio provide indication of plant water status in wine grape vineyards 
Authors: Kurtural Sahap , Yu Runze , Zaccaria Daniele
Published: March 2021

Proximal sensing is being integrated into vineyard management as it provides rapid assessments of spatial variability of soils’ and plants’ features. The electromagnetic induction (EMI) technology is used to measure soil apparent electrical conductivity (ECa) with proximal sensing and enables to appraise soil characteristics and their possible effects on plant physiological responses. This study was conducted in a micro irrigated Cabernet Sauvignon (Vitis vinifera L.) vineyard to investigate the technical feasibility of appraising plant water status and its spatial variability using soil ECa and must carbon isotope ratio analysis (δ13C). Soil temperature and soil water content were monitored in-situ using time domain reflectometry (TDR) sensors. Soil ECa was measured with EMI at two depths [0 – 1.5 m (deep ECa) and 0 – 0.75 m (shallow ECa)] over the course of the crop season to capture the temporal dynamics and changes. At the study site, the main physical and chemical soil characteristics, i.e. soil texture, gravel, pore water electrical conductivity (ECe), organic carbon, and soil water content at field capacity, were determined from samples collected auguring the soil at equidistant points that were identified using a regular grid. Midday stem water potential (Ψstem) and leaf gas exchange, including stomatal conductance (gs), net carbon assimilation (An), and intrinsic water use efficiency (WUEi) were measured periodically in the vineyard. The δ13C of produced musts was measured at harvest. The results indicated that soil water content (relative importance = 24 %) and texture (silt: relative importance = 22.4 % and clay: relative importance = 18.2 %) were contributing the most towards soil ECa. Deep soil ECa was directly related to Ψstem (r2 = 0.7214) and gs (r2 = 0.5007). Likewise, δ13C of must was directly related to Ψstem (r2 = 0.9127), gs (r2 = 0.6985), and An (r2 = 0.5693). Results from this work provided relevant information on the possibility of using spatial soil ECa sensing and δ13C analysis to infer plant water status and leaf gas exchange in micro irrigated vineyards.
Ground-truth Reference Dataset of 1001 Rocket Launches for Space Missions and their Infrasonic Signatures
Authors: Hupe Patrick , Pilger Christoph , Gaebler Peter , Ceranna Lars
Published: March 2021

The infrasound technique is applied to monitor atmospheric explosions in the context of the Comprehensive Nuclear-Test-Ban Treaty and, among other purposes, to characterize large meteoroids entering Earth's atmosphere. Anyhow, for both types of sources, the exact location and time are initially unknown and sometimes difficult to precisely estimate. In contrast, rocket launches are well-defined ground-truth events generating strong infrasonic signatures. In this study, we analyse infrasound signatures of 1001 rocket launches for space missions recorded at stations of the International Monitoring System between 2009 and mid-2020. We include all surface- or ocean-based launches within this period with known launch time, location, rocket type, and mission name; whereas launches of sounding rockets and ballistic missiles for scientific and military purposes, respectively, are excluded from our study. We characterize the infrasonic signatures of over 70 different types of rockets launched at 27 different globally distributed spaceports and are able to identify infrasound signatures from up to 73% of the launches considered. We use this unique dataset to estimate the global detectability of such events and to characterize rocket infrasound. We provide the results as a DOI-assigned ground-truth reference dataset for supporting its further use in geophysical and atmospheric research.
Assessing the contribution of natural and anthropogenic processes on sediment dynamics in the Rio Santa (Peru) through sediment fingerprinting
Authors: Kitch Jessica , Clason Caroline , Rangecroft Sally , Morera Sergio , Blake Will
Published: March 2021

The combination of a changing climate and growing population poses a contemporary challenge for the water-food-energy security nexus in mountain regions, especially in glacier-fed catchments such as the Rio Santa in the Peruvian Andes. Soil erosion due to both natural processes and anthropogenic activities can exacerbate this challenge, with increased levels of sediment in river systems endangering crucial river functions, such as crop irrigation, drinking water, and hydroelectricity. Furthermore, sediment can act as a transport pathway for contaminants, in addition to being a source of contamination itself. Previous studies have suggested that soil erosion related to human activity vastly exceeds the rate of natural soil production in many Andean catchments, where research to date has primarily focused on larger eastern catchments. Smaller western catchments, however, are important for many major Andean cities reliant upon upstream water supplies. It is thus, important to identify sediment sources and better understand sediment dynamics to manage the threats to water supply.

Sediment fingerprinting approaches are one technique that can contribute to improved understanding of sediment sources and dynamics and the impact of soil erosion in a catchment, and thus contribute to water resource management at the catchment level. Taking a distributed approach along the Rio Santa, this study aims to improve understanding of natural and anthropogenic contributions to sediment production in this Andean system. Key sediment sources explored are glacial sediment potentially enhanced by retreat, agricultural land, forestry operations, land under natural vegetation, and mining. The distributed approach permits quantification of their dynamics throughout the catchment. All source and mixture samples were analysed using Wavelength Dispersive X-ray Fluorescence (WD XRF) to develop geochemical fingerprints and the MixSIAR mixing model was used to apportion sediment sources. While sediment sampling presents a number of challenges when working in remote, mountainous regions such as the Rio Santa catchment, sediment fingerprinting has the potential to help reduce environmental degradation when used to guide local resource management decisions.
Combining gliders and models to understand mesoscale biogeochemical patterns at the Angola-Benguela front
Authors: Lovecchio Elisa , Henson Stephanie , Carvalho Filipa , Briggs Nathan
Published: March 2021

The Angola-Benguela frontal region represents an extremely dynamic portion of the ocean located along the south-western African coast, at the northern edge of the South Atlantic gyre. At this boundary, the northern warm and saline waters of the Angola Basin mix with the southern colder and fresher waters carried by the Benguela current through a combination of processes that span a wide range of spatio-temporal scales. This study combines the use of underwater glider data collected between February and June 2018 with a high resolution 3D physical-biogeochemical model to investigate how these lateral exchanges impact the oxygen and organic carbon distributions in the proximity of the front. From the glider data, we identify a set of salinity, oxygen and organic carbon anomalies impacting the first 500 m of the water column during February-June 2018. Using satellite images of physical and biological data and an eddy identification algorithm, we discuss these anomalies in the context of the surrounding physical and biological setting at the time of measurement and identify key processes that may be responsible for the observed tracer patterns. We employ the Regional Ocean Modeling System (ROMS) coupled with the Biogeochemistry Ecosystem Circulation model (BEC) to further explain and upscale our findings. We study the dynamics of cross-frontal exchanges of oxygen and organic carbon in the first 500 m depth. We show how the coupling between long filaments and intense anticyclonic eddies forming at the front generates a complex pattern of recirculation of Angola Basin-derived saline and low-oxygen waters into the oxygenated Benguela region. Finally, we quantify the oxygen lateral transport coupled with these dynamics, and discuss the implications for the biological activity in the region.
How scale matters in joint knowledge production for nature-based solutions. Dynamic proximity among stakeholders in climate adaptive water management for brook catchment Aa, the Netherlands
Authors: Brok Ermy , Floor Judith , van Lamoen Frank , Lansu Angelique
Published: March 2021

The question ‘how scale matters’ from experienced policy makers in adaptive water management motivated us to explore the issue. In search for climate resilience of brook catchments stakeholders collaborate. Those collaborations involve dynamic proximity, giving rise to innovative, creative solutions using natural hydrological and landscape processes. Dynamic proximity is known from innovation research in the field of high-tech regional economic development. The question is whether dynamic proximity among stakeholders influences success of joint knowledge production (JKP) processes as well. We focus on a more nature-tech context of regional economic development: creating nature-based solutions (NbS) to support climate resilience. The conceptual model to study the creative process of JKP combines the four dimensions of JKP with four forms of dynamic proximity. Along this matrix quotes of stakeholders were analysed from seven semi-structured interviews. At least one stakeholder in the process for the brook-restoration of the Aa (the Netherlands) was selected from industry, academia, government and non-profit organizations (following the ‘quadruple helix model’). Findings show that stakeholders who are versatile in using various forms of social, cognitive, institutional and geographical dynamic proximity in the process of JKP experience the process as more successful. Moreover, stakeholders overdoing the institutional or geographical aspects of proximity run into adverse effects, a mechanism recognized in economic geography as the proximity paradox. Furthermore, stakeholders are better supported when they use knowledge instruments, but only when keeping in mind the balance of forms of dynamic proximity. Findings were validated against two stakeholders’ experiences in another process for the Aa of Weerijs (the Netherlands). We suggest refining the model by adding two forms of dynamic proximity relating to interests and to resources, enabling a sharper focus on knowledge production under the heading of cognitive proximity. So, scale matters in such rural, natural processes. The perspective on proximity helps innovation, if proximity among stakeholders does not become too proximate. We have summarised findings in the form of a proximity tool, which is useful for optimizing the science-policy interface in regional adaptive water management.
Intra-ice and intra-sediment cryopeg brine occurrence in permafrost near Utqiaġvik (Barrow)
Authors: Iwahana Go , Cooper Zachary , Carpenter Shelly , Deming Jody , Eicken Hajo
Published: March 2021

Cryopeg is a volume of permafrost with a significant amount of cryotic unfrozen water as a result of freezing-point depression by dissolved salt content. Cryopeg and saline permafrost have been reported for coastal areas of the Arctic seas, and their current distribution and future changes are a great concern for the warming Arctic, as the state of permafrost controls ground stability and the functioning of ice cellars in Arctic villages. To describe the distribution and segregation of cryopeg lenses, and to explore the origin and development of the cryopeg and associated brines found near Utqiaġvik, we conducted extensive sampling campaigns in the Barrow Permafrost Tunnel during May of 2017 and 2018.

We found two types of cryopeg brines based on their distinctive spatial occurrences: (1) intra-ice brine (IiB), entirely bounded by massive ice; and (2) intra-sediment brine (IsB), found in unfrozen sediment lenses within permafrost. While two examples of IiB have been reported previously, they were each found within ice layers below ice-sealed lakes in the McMurdo Dry Valleys of Antarctica, geological settings very different from ours. In our study, the IiBs were at roughly atmospheric pressure and situated in small pockets of ellipsoidal or more complex shape (dimensions of up to about 30 cm wide and 3 cm height) within 17–41 cm above the underlying sediment layer. Several individual IiB pockets may have been connected by porous ice of low permeability. Radiocarbon dating suggests that, at the earliest, the IiB was segregated about 11 ka BP from IsB-bearing cryopeg underneath. IsB lenses were interpreted as having developed through repeated evaporation and cryoconcentration of seawater in a lagoonal environment, then isolated at the latest when the surrounding sediment froze up and became covered by an upper sediment unit around 40 ka BP or earlier.

Considering the common characteristics among the cryopeg brines accessed from the tunnel and those found in brine-bearing marine sediment around Utqiaġvik, all occurrences of cryopeg brine in the region may have experienced analogous development despite potentially contrasting salinities and estimated ages. An increase in permafrost temperature invariably will result in expansion of cryopeg lenses and may change movement of liquids within the permafrost, which potentially become threats to Arctic coasts, infrastructure, and food security.
Remediation of intrinsic preferential flow pathways in water repellent soils' profile using surfactant
Authors: Ogunmokun Felix Abayomi , Wallach Rony
Published: March 2021

Preferential flow pathways and uneven soil water and chemical distribution are intrinsic phenomena in water repellent soils. These uneven water and chemical distribution reduce water uptake by the plant roots on one hand and enhance deep percolation and chemical leaching, on the other hand, thereby enhancing soil and groundwater pollution. The results of attempts to remediate soil water repellency and heterogeneous spatial distribution of soil moisture and chemicals within the root zone by surfactant application will be addressed.  

This study was conducted in a commercial citrus orchard in central Israel that is irrigated with treated wastewater. Previous studies have revealed that prolonged irrigation using treated wastewater renders the soil water repellent with its associated adverse effects. The soil water distribution within the soil profile was monitored by frequent electrical resistance tomography (ERT) scans. The spatial distribution of different chemicals within the soil profile was obtained by chemical analysis of disturbed soil samples taken manually along a line transects. Two methods of surfactant application were used and compared: 1) on soil surface spraying (area source), 2) via drippers application (point source).

Surfactant spraying onto the water repellent soil's surface succeeded in turning the soil wettable, diminishing the preferential flow pathways, and renders the soil water and dissolved chemicals uniformly distributed. In contrast, drip applied surfactant exacerbated the incidence of preferential flow pathways and the leaching of solutes from the soil. Moreover, the overall average water content in the 0-40 cm soil layer significantly increased with surfactant spraying than with drip application even though both were higher than the control plots. These results substantiate previous laboratory-scale studies in which surfactant was applied to water repellent soils packed in a transparent flow chamber by these two methods. Additionally, the yield from the on-surface surfactant sprayed plots show a slight continuous increase compared to the untreated plots.
Risk of increased hydrological alteration due to penetration of intermittent renewable energy generation
Authors: Gonzalez Jose M. , Tomlinson James , Martínez-Ceseña Eduardo A. , Obuobie Emmanuel , Panteli Mathaios , Harou Julien
Published: March 2021

The penetration of intermittent renewable energy sources (RES) such as solar PV and wind is rapidly growing in many countries. Due to the RES intermittency, it is becoming increasingly difficult to manage the balance between energy generation and demand at any time. In this context, it is necessary to use other energy generation technologies, such as hydropower, a controllable renewable source that may already be available as a means to provide energy balance. Hydropower, through hydropeaking, is considered a flexible solution to this challenge as it can quickly help manage the fluctuations in the generation-demand balance due to the highly RES intermittency. Hydropeaking plants usually supply energy at maximum capacity during on-peak periods, whereas they run at low power output during off-peak periods. However, this operating scheme leads to heavy hydrological alteration downstream of the hydropower plants because of short-term fluctuations in turbined flows motivated by the integration of intermittent RES. In this work, an integrated and spatially distributed river-basin and energy system co-simulation model is used to evaluate the hydrological alteration produced by varying penetration levels of intermittent RES in Ghana's national power system. Results show that the spatial and temporal distribution of hydrological alteration, correlated with intermittent RES penetration levels, varies according to the hydropower plants' location within the power system and the intermittent renewable resources seasonality throughout the year.
Marine records of Holocene glacier variability in the Kerguelen Islands (South Indian Ocean): sedimentology, chronology, and paleoclimatic drivers
Authors: Chassiot Léo , Chapron Emmanuel , Michel Elisabeth , Favier Vincent , Jomelli Vincent , Charton Joanna , Verfaillie Deborah , Crosta Xavier
Published: March 2021

The strength and the location of Southern Hemisphere winds (SHW) define an annular mode (SAM), a major component of interannual climatic variability in the Southern Hemisphere. SAM has a significant impact on mid-latitude westerly winds, but also acts on the meridional moisture transport over the Southern Ocean (for example, in the case of atmospheric rivers), with dramatic consequences on the cryosphere at high latitudes. Assessment of past, present and future changes in the SAM is essential for understanding climate variations and impacts at high latitudes. To date, Holocene proxy-based reconstructions of SAM are limited to South America, Australia/New Zealand, and Antarctica. In opposite, the paucity of SAM-related records for the Southern Indian Ocean presently limits our understanding of the spatial and temporal extent of SHW behavior in this region.

To this aim, we present a series of 30-m long marine records retrieved from a fjord fed by glacial melt of the Ampere glacier belonging to the Cook Ice Cap in the Kerguelen Archipelago (49˚20’S, 69˚20’E). A new chronological framework, based on Bayesian modelling of 50 radiocarbon ages along with 137Cs and 210Pb measures, allows reconstructing 4 kyrs of sediment discharge related to glacier variability. Sedimentological and geochemical analyses from XRF and GEOTEK core scanners highlight (i) a regional tephra at 950 cal BP; (ii) regular occurrences of floods during the LIA; and (iii) a background sedimentation related to glacial flour inputs through hypo- and hyperpycnal flows favoring very high sedimentation rates (1-2 cm.a-1) in the fjord. Phases of glacier advances and retreats linked to moisture transport by SHW are reflected by fluctuations in sedimentological and geochemical signals, and correlated with moraines dating on land. Over the past 4 kyrs, four cycles of glacier advances/retreats can be evidenced, reflecting wet/dry periods in response to shifts in the position and changes in magnitude of the SHW, associated with moisture transport and precipitation in the Southern Indian Ocean. On centennial timescales, wet/dry periods inferred from Kerguelen are in-phase with Holocene SAM-related records from South America and Tasmania over the last 2 kyrs, suggesting the long-term glacier dynamic at Kerguelen is also related to a centennial expression of SAM.

Acknowledgments : Marion Dufresne Crew, ARTEMIS program, UGA-ARCA.
Enhanced internal tidal mixing in the Philippine Sea mesoscale environment
Authors: You Jia , Xu Zhenhua , Li Qun , Zhang Peiwen
Published: March 2021

Turbulent mixing in the ocean interior is mainly contributed by internal wave breaking; however, the mixing properties and the modulation effects of mesoscale environmental factors are not well-known. Here, the spatially inhomogeneous and seasonally variable diapycnal diffusivities in the upper Philippine Sea were estimated from ARGO float data using a strain-based finescale parameterization. Based on a coordinated analysis of multi-source data, we found that the driving processes for diapycnal diffusivities mainly included the near-inertial waves and internal tides. Mesoscale features were important in intensifying the mixing and modulating its spatial pattern. One interesting finding was that, besides near-inertial waves, internal tides also contributed significant diapycnal mixing for the upper Philippine Sea. The seasonal cycles of diapycnal diffusivities and their contributors differed zonally. In the mid-latitudes, wind-mixing dominated and was strongest in winter and weakest in summer. In contrast, tidal-mixing was more predominant in the lower-latitudes and had no apparent seasonal variability. Furthermore, we provide evidence that the mesoscale environment in the Philippine Sea played a significant role in regulating the intensity and shaping the spatial inhomogeneity of the internal tidal mixing. The magnitudes of internal tidal mixing was greatly elevated in regions of energetic mesoscale processes. The anticyclonic mesoscale features were found to enhance diapycnal mixing more significantly than did cyclonic ones.
Three dimensional simulation on the generation and propagation of internal tides and solitary waves northeast of Taiwan Island
Authors: Min Wenjia , Xu Zhenhua , Li Qun , Zhang Peiwen , Yin Baoshu
Published: March 2021

The slope area northeast of Taiwan was known as a hotspot for internal tides and internal solitary waves (ISWs), while their specific sources and generation mechanism of ISWs remain unclear. We investigate the generation and evolution processes of internal tides and ISWs with realistic configuration based on the high resolution non-hydrostatic numerical simulations. The ISWs northeastern Taiwan show a complex pattern according to the satellite image and our numerical results. ISWs propagate to various direction, and both shoreward and seaward propagating ISWs are generated on the continental slope. The ISWs observed on the continental slope-shelf region northeastern Taiwan can be generated by two ways. One is the local tide-topography interaction, and the other is the disintegration of remote internal tides generated over the I-Lan Ridge. The generated internal tides propagate northward to the Okinawa Trough, and can reach the continental slope-shelf region. During the propagation of the internal tides, the internal tides start to steepen and internal solitary waves are formed about 80 km north of I-Lan Ridge. The amplitude of the generated internal solitary waves is about 30 m. Furthermore, the Kuroshio is important to modulate the propagation and evolution of internal tides and ISWs, especially to the complexity of the ISW spatial pattern. We revealed most of the generated internal wave energy is dissipated locally over the double-canyon region, and strong mixing occur over the canyons.
Electromagnetic ion-cyclotron instability in low beta plasma with intrinsic Alfven waves
Authors: Pu GuanShan , Wang ChuanBing , Zhang PeiJin , Ye Lin
Published: March 2021

Intrinsic Alfven waves (IAWs) exist pervasively in the solar-terrestrial plasma, which can preferentially heat newborn ions in the direction perpendicular to the ambient magnetic field via non-resonant interactions when the plasma beta is low. The anisotropized newborn ion populations can excite electromagnetic ion-cyclotron (EMIC) instability. Parametric calculations indicate that the lower the plasma beta is, the higher the growth rate, while the growth rate increases with the number density of newborn ions and the intensity of IAWs. The marginal stable surface in three-dimensional parameter space is also calculated, which provides a qualitative description of parametric conditions for instability. We propose that the coupled effects of non-resonant heating by IAWs and EMIC instability could be an effective mechanism for transferring the energy from low-frequency IAWs to EMIC waves with a frequency below the gyrofrequency of the corresponding ion species. Furthermore, the temperature anisotropy of background ions with the same sense has positive effects on the growth of EMIC waves excited by newborn ions.
A Benchmark for Bivariate Causal Discovery Methods
Authors: Käding Christoph , Runge Jakob
Published: March 2021

The Earth’s climate is a highly complex and dynamical system. To better understand and robustly predict it, knowledge about its underlying dynamics and causal dependency structure is required. Since controlled experiments are infeasible in the climate system, observational data-driven approaches are needed. Observational causal inference is a very active research topic and a plethora of methods have been proposed. Each of these approaches comes with inherent strengths, weaknesses, and assumptions about the data generating process as well as further constraints.
In this work, we focus on the fundamental case of bivariate causal discovery, i.e., given two data samples X and Y the task is to detect whether X causes Y or Y causes X. We present a large-scale benchmark that represents combinations of various characteristics of data-generating processes and sample sizes. By comparing most of the current state-of-the-art methods, we aim to shed light onto the real-world performance of evaluated methods. Since we employ synthetic data, we are able to precisely control the data characteristics and can unveil the behavior of methods when their underlying assumptions are met or violated. Further, we give a comparison on a set of real-world data with known causal relations to complete our evaluation.