bluuebunny/crossref_metadata_2025 huggingface dataset:
Glaucophane plasticity and scale-dependent yield strength from nanoindentation experiments
Authors: Kotowski Alissa , Kirkpatrick James , Thom Christopher A. , Alidokht Sima A. , Chromik Richard
Published: March 2022

Subduction interface shear zones localize deformation and sustain plate-boundary weakness on million-year timescales, as well as host a variety of enigmatic seismicity and slow slip transients. A physical understanding of the steady-state and transient mechanics of subduction shear zones requires quantitative constraints of the plastic yield strength and deformation mechanism(s) of metamorphic rocks and minerals that occupy the plate interface. However, very little is known about the rheology of many hydrous minerals that occupy the plate interface, such as glaucophane (end-member sodic amphibole). This is partly because conventional deformation experiments meet technical challenges when trying to measure plasticity in the laboratory due to the stability field of glaucophane, the confining pressure needed to suppress fracture, and the limited range of trade-off between temperature and strain rate in experiments.

 

Here, we present preliminary results from room-temperature nanoindentation experiments on thin sections of glaucophane-rich rocks that produced crystal plasticity by dislocation glide under high-stress conditions. Nanoindentation produces in-situ confining pressure that typically inhibits brittle fracture during loading in favor of plastic deformation. Since the volume of deformation beneath the tips is very small compared to the grain size, each indent is essentially a single-grain mechanical test (i.e., effects of grain boundaries can be ignored). We convert load-depth data from two spheroconical tips of different radii to stress-strain curves to quantify the elastic-plastic transition and characterize post-yield behavior. We measure yield stress as a function of grain orientation. Both post-yield weakening and post-yield hardening occur, which likely reflect brittle fracture along micro-faults/cleavage planes, and dislocation bursts and pile-ups, respectively. Glaucophane hardness decreases with increasing length scale of deformation (i.e., indentation radius), capturing a “size effect” that may reflect an effective decrease in dislocation density as the volume of plastic deformation increases beneath the indent tip. This effect is well-constrained for many metals and some geologic materials, including olivine.

 

The mechanical tests provide a basis for interpreting microstructures of naturally-deformed blueschists, which suggest that glaucophane exhibits recovery-limited dislocation glide and dynamic recrystallization. Low-temperature plasticity may provide a micro-physical framework for long-term strain localization and transient brittle shear when meta-mafic rocks are deformed to high strain.
Co-designing climate services for drought management in the Guadalquivir River Basin 
Authors: Pesquer Lluís , Domingo-Marimon Cristina , Broekman Annelies , De Stefano Lucia , Ninyerola Miquel
Published: March 2022

Water availability is a limiting factor for many human activities and for the maintenance of ecosystems. Monitoring of water resources, as well as the impacts of water scarcity on human activities and natural ecosystems, is key for building adequate water management strategies. With this aim, different European and Worldwide organisations provide several datasets and services. However, do these services fit to the user needs and requirements?

This work focusses on the refinement of existing drought indexes for fitting users’ needs. We review the specifications and characteristics of drought related databases obtained from Copernicus, such as the European Drought Observatory (EDO) and the Global Drought Observatory (GDO) at Copernicus Emergency Management Service, tools produced by the United Nations - UNCCD Drought Toolbox- and other datasets provided by research centres such as CSIC or the Global SPEI database.

Climate services are obtained by tailoring the datasets to the needs and recommendations expressed by selected stakeholders representing different relevant sectors: agriculture, livestock, forestry, biodiversity, etc. and different professional profiles: decisions makers on water management strategies, managers of protected areas, farmers, etc. Thanks to innovative settings, such as living lab frameworks, stakeholders are enabled to co-design the new drought services proposed, as well as helping to improve the indexes through sharing the evaluation of their usability and impact when implemented in real-life decision taking processes.

The new drought related information products and services obtained through co-production, contribute to improve

the spatial resolution requirements of the involved climate variables (mainly temperature and precipitation) by remote sensing products (i.e. land surface temperature, vegetation indexes, etc.)  through downscaling techniques of the existing drought databases

the coherence between these derived remote sensing products and the existing in-situ observations

the usability of climate services for decision making

The living lab framework underpinning this study is located in the Guadalquivir River Basin, in the northern part of the region of Andalusia, Spain, particularly vulnerable to drought impacts. Results will help improving mitigation and adaptation measures to reduce the vulnerability to different drought scenarios forecasted for the upper and middle parts of the Basin.
Revisiting risk in a multi-hazard setting: the case of Cyclone Amphan occurring within the COVID-19 pandemic in the Indian Sundarbans
Authors: Banerjee Sumana , Shekhar Himanshu , Cotti Davide , Sparkes Edward , Werners Saskia , Hagenlocher Michael
Published: March 2022

Amidst a period of complete lockdown due  to COVID-19, the severe cyclonic storm Amphan made landfall in the Indian Sundarbans on 20 May 2020. The occurrence of a cyclone during  the pandemic warranted investigation of interconnected risks and impacts in this climate hotspot and eco-critical region. Based on a desk study, field observations, key informant interviews and expert consultations, this research focussed on better understanding direct and cascading risks and the associated impacts from the concurrence of the two hazards occurring simultaneously. Our analysis reveals that although the region has not experienced a high number of COVID-cases between March and August 2020, the presence of underlying vulnerabilities exposed the population to cascading effects caused by the pandemic-induced lockdown along with the compounding effect of the Cyclone Amphan. In the Indian Sundarbans, COVID-19 acted as an exogenous shock, but its interplay with interconnected vulnerabilities resulted in the emergence of disruptions of a systemic nature. This was particularly the case in the economic domain, with cascading impacts observed across the welfare, education, and employment sectors.  Cyclone Amphan, led to additional cascading impacts on these sectors, and affected other sectors such as health and infrastructure as well as biodiversity. Interventions such as introduction of new social protection schemes and community participation in cyclone preparedness measures have helped the system from facing a total collapse. However, some interventions that were implemented to mitigate impacts of these two concurring hazards somewhat counteracted one another. For example, while stringent COVID-19 interventions stressed on safety norms (including social distancing and stay at home orders), the hazard response protocol for Cyclone Amphan directed communities to evacuate their homes and move to communal shelters which were being used as quarantine units for returning migrant workers till before the cyclone. This caused concerns among the evacuated population, thus undermining the efficacy of the response effort. This case study underpins the need for moving from hazard-by-hazard approaches of understanding and managing risks towards integrated approaches that consider interconnected vulnerabilities, risks and impacts based on a systems perspective. Further, it also provides lessons for risk management in a multi-hazard and multi-risk setting besides sharing recommendations for better risk management in the Indian Sundarbans.
AlterEco: Annual shelf sea net production from a fleet of autonomous gliders 
Authors: Hull Tom , Greenwood Naomi , Loveday Ben , Symth Tim , Palmer Mathew , Williams Charlotte , Kaiser Jan
Published: March 2022

The coastal shelf seas are a vitally important human resource for numerous ecosystem services, including food, carbon
storage, biodiversity, energy, and livelihoods. These highly dynamic regions are under a wide range of stresses, and
as such future management requires appropriate monitoring measures.  

A key metric to understanding and predicting future ecosystem change are the rates of biological production. Assessing
the variability in production at appropriate temporal and spatial scales is essential to accurately determine the fate
of carbon, and ecosystem health in these regions.  

Using high frequency data from a fleet of instrumented submersible gliders, we calculate oxygen based net community
production for an 18-month period in the central North Sea; a productivity hotspot and challenging environment for
long term monitoring with autonomous vehicles.
From these data we determine an annual depth integrated carbon budget, and we observe both the interannual and
seasonal changes in production.  

We compare these net community production estimates to the PAR and chlorophyll fluorescence based net primary
production estimates using the same glider fleet and supported by satellite earth observations. 

These observations and analysis are part of the AlterEco project, which seeks to demonstrate a novel monitoring
framework to deliver improved understanding of key shelf sea ecosystem drivers. 
Assessing hydrodynamic processes of nearshore coral reefs: numerical modeling and field observations around the island of Curaçao
Authors: Bertoncelj Vesna , Stocchi Paolo , Holzhauser Caitlin , Sánchez Barranco Virginia , Alcantar Esmeralda , Candy Adam , Haas Andi , Mienis Furu , de Nooijer Lennart , van Sebille Erik , Vermeij Mark
Published: March 2022

The state of coral reef ecosystems is highly dependent on the availability and ratio of essential resources such as oxygen, minerals and nutrients, and the presence of pollutants, pathogens and other possible stressors. The distribution of these inputs is dynamic and depends on many factors, including the nearshore hydrodynamic processes. These are unique processes, consisting of tidal pumping, nearshore circulation, and wave action. Furthermore, these processes are highly influenced by complex reef bathymetry and the physical roughness of the reef. The latter has a crucial role in the boundary layer characteristics, which influences uptake by reef organisms at smaller spatial scales.

The understanding of distribution and transport of particulate and dissolved substances is challenging as field surveys are difficult to perform and there is a large variety of coral shapes. However, assessing the hydrodynamic processes is a necessary first step in order to link the sources and sinks of substances with the coral health and growth. Within the interdisciplinary research program SEALINK, we aim to assess the distribution and pathways of substances around the island of Curaçao. Field observations on selected sites along the coast of Curaçao include current and wave measurements with Acoustic Doppler Current Profilers and flow visualization with fluorescent dye.

We will present preliminary results from the field campaign showing velocity fields and wave transformation on different stations along the cross-shore transects on the reef platform. Using a combination of field observations and 3D non-hydrostatic Computational Fluid Dynamics models, we investigate the mixing mechanisms and local energy balance at scales of O(10 m) on the selected reef quadrants. This serves as a basis for a further analysis with Lagrangian Particle Tracking methods to track the selected substances identified with other field campaigns within the SEALINK program.
Saturated buffer zones as novel drainage mitigation measure in Denmark
Authors: Zak Dominik , Maagaard Astrid , Kronvang Brian , Hoffmann Carl , Audet Joachim , Petersen Rasmus
Published: March 2022

Vegetated buffer strips have been introduced in some European countries since the 1980s to mitigate the deterioration of watercourses by surface runoff from intensively managed agricultural land. However, the effectiveness was proven to be less for the retention of dissolved nutrients than expected, as agricultural drainage water was directly charging streams via tile drainage pipes. Therefore, a new drainage mitigation measures was introduced in Denmark to lower the nutrient load of freshwater and eventually marine systems, called saturated buffer zone (SBZ). Drainage pipes are disconnected at the sloping field margin and to the riparian zone by diverting drainage water to a buried, lateral distribution pipe running parallel to the stream. Results of a 2-year monitoring study unravel a high performance of the investigated SBZ as nitrate and phosphate removal efficiency was as high as 87% and 76 %, respectively. However, these high efficiencies must still be interpreted with caution since subsurface water flows was rather heterogenous varying by two orders of magnitude within the investigated transects. None the less, SBZs are a promising mitigation measure for removing nutrients from farmland.
Quartz Rotation Sensor
Authors: Venkateswara Krishna , Paros Jerome , Bodin Paul , Wilcock William , Tobin Harold J.
Published: March 2022

A new high-precision ground- or platform-rotation sensor called the Quartz Rotation Sensor (QRS) has been developed and tested. The QRS is a mechanical angular accelerometer that senses rotational torque with an inherently digital, load-sensitive resonant quartz crystal. It is a portable broadband sensor with a noise floor measured to be ∼45 pico-radian/root (Hz) near 1 Hz, and a resonant period of ~10 s. The noise floor of the sensor near 0.1 Hz is more than two orders of magnitude lower than other similarly sized instruments enabling a dramatic improvement in ability to measure rotational teleseismic signals and tilt contamination in horizontal seismometers. We will present details of the sensor and measurements of rotational components of teleseismic waves recorded with the sensor at a vault. The QRS is useful for rotational seismology and for improving low-frequency seismic isolation in demanding applications such as the Laser Interferometer Gravitational-Wave Observatories.
Exploring the Influence of the Duration of Aerosol Perturbations on Cloud Responses
Authors: Feingold Graham , Prabhakaran Prasanth , Zhang Jianhao , Zhou Xiaoli , Hoffmann Fabian
Published: March 2022

High-resolution modeling of aerosol-cloud interactions typically applies aerosol perturbations for the duration of the simulation, which may be anywhere from a few hours to a few days.

In reality, however, natural and anthropogenic aerosol perturbations have characteristic durations, along with concomitant changes in meteorology and associated cloud conditions. In this talk we will explore the effect of the duration of aerosol perturbations on the cloud radiative responses using idealized large eddy simulations. We will also consider observed seasonal cycles in meteorology, clouds, and aerosol, and how they affect cloud albedo responses. These exercises will help to assess the radiative effect of aerosol-cloud interactions.
Measurements of ice-nucleating particle concentration and size at Storm Peak Laboratory
Authors: Lacher Larissa , Froyd Karl , Hallar Gannet , McCubbin Ian , Jacquot Justin , Dameto de  Espana Carmen , Shen Xiaoli , Schill Gregory , Baker Darin , Leisner Thomas , Möhler Ottmar , Cziczo Dan
Published: March 2022

The presence of ice in mixed-phase clouds has a vital impact on their radiative properties, lifetime, and  ability to precipitate. Ice crystal formation is initially induced by a rare subset of ambient aerosol  particles called ice-nucleating particles (INPs). Despite the importance of INPs on aerosol-cloud interactions and century-long research efforts, the knowledge about their nature and atmospheric  abundance still needs improvement. Recent instrument developments allow more automated and  continuous INP measurements with a high time resolution, to gain a better understanding of the natural variability of INPs in different locations, and to investigate the identity and source regions of them. 

Here we present long-term observations of INPs at Storm Peak Laboratory (SPL) located in the Rocky Mountains of Colorado. SPL is at an altitude of 3200 m a.s.l. within the lower free troposphere, and in winter it is a location where mixed-phase clouds frequently occur. Therefore, the present aerosol particles are directly relevant for ice formation in such clouds. The ongoing INP measurements started in October 2021, and are conducted with the Portable Ice Nucleation Experiment (PINE) at conditions resembling the formation of mixed-phase clouds at temperatures between -22°C and -32°C. Results on the short-term and inter-seasonal variability will be presented, with a focus on parallel measurements of aerosol particle properties and meteorology. During the winter months of January and February 2022, we characterized the size of the INPs by selecting ice crystal residuals downstream of PINE using a pumped-counterflow virtual impactor and a novel optical particle counter. As this setup operates continuously, it is capable to investigate INP properties for longer time periods and to improve sampling statistics. In the future, it will be used with other diagnostic instruments, such as a single particle mass spectrometer, giving insights into the size and chemical composition of INPs, and thus allows to have a direct measure of the nature of INPs in ambient air.
Mineralogy, structure and tectonic significance of quartz veins from the northern Saih Hatat Dome (eastern Oman Mountains)
Authors: Scharf Andreas , Mattern Frank , Pracejus Bernhard , Callegari Ivan , Bolhar Robert , Nasir Sobhi , Al-Wahaibi Saja , Al-Battashi Laila , Al-Hadhrami Marwa , Al-Harthi Thuraiya , Al-Suqri Safiya
Published: March 2022

The rocks of the Saih Hatat Dome (SHD) formed during and after two major geological events shaping Arabia: 1) Subduction of continental rocks in the course of the Late Cretaceous Semail Ophiolite obduction onto the Arabian Plate and 2) Exhumation of >16 km and high deformation/folding in the northeastern part of the SHD. The latter resulted in a ~20 km wide recumbent fold (Saih Hatat Fold Nappe). The sub-horizontal fold axis of this fold trends NNE in the northern SHD. The core of the SHD and the recumbent fold consist of dark Neoproterozoic meta-shales and meta-sandstones, while its margin (and upper/lower limbs of the recumbent fold) consist of Permian cliff-forming carbonates.

Within the northern SHD, numerous milky quartz veins occur. We structurally and mineralogical analyzed >500 of these veins, covering an area of ~200 km2. The veins vary in width from one centimeter to a few meters, while the length ranges between several decimeters to several decameters. Associated with the predominant milky quartz, are calcite, siderite, chlorite, albite, anorthite, actinolite, rutile, hematite, goethite, and pyrrhotite. Rare molybdenite aggregates seem to replace carbonate, in which it occurs exclusively. Quartz microstructures include bulging (BLG) recrystallization, sub-grain rotation (SGR) recrystallization, and undulose extinction. Sub-grains and triple junctions in quartz are common. The mineralogy and quartz microstructures indicate maximum peak temperature conditions of ~400-500°C.

At least two sets of veins can be distinguished. Both vein sets occur mostly in clusters and partly form vein swarms. The mineralogy and quartz microstructure of both vein sets is similar. The older set 1 has been folded by the Saih Hatat Fold Nappe. Thus, vein formation predates 76-70 Ma. Furthermore, veins of set 1 are often sub-parallelly oriented to the main foliation of the host rocks, and they may be boudinaged. They may form complicated vein structures. We assume that this vein set initially formed during the Permian Pangean/Tethys rifting. The second vein set is abundant, sub-vertically and strikes consistently E/W to ESE/WNW. These veins cut the overall moderately NW-dipping bedding surfaces of the ambient rocks. Set 2 veins either formed during exhumation of the dome (Late Cretaceous to early Eocene and late Eocene to Oligocene) or they are part of the NW-striking sinistral Hajar Shear Zone, which affected the entire eastern Oman Mountains during the Oligocene to early Miocene. Ongoing U-Pb dating of carbonates and further field survey will further contribute to the understanding of their age and tectonic setting.
Decoding bedrock channel morphology using high-resolution topographic data
Authors: Hodge Rebecca , Beer Alex , Asher Ben
Published: March 2022

The 3D morphology of a river channel is a key control on the resistance experienced by the flow, affecting the channel hydraulics, sediment transport and in-stream habitats. In bedrock channels, the morphology is a combination of multiple components including exposed bedrock, overlying sediment cover, and boulders. Furthermore, the morphology of exposed bedrock is expected to depend on the lithology, rock structure and the dominant erosion processes. In order to improve predictions of flow resistance in bedrock channels, we first need to understand how these different components contribute to the overall bed morphology. Here, we present high-resolution (cm-scale) topographic data collected using terrestrial laser scanning from multiple bedrock channel sections on different lithologies. We compare how roughness varies between these channels, and at different spatial scales. We identify the dominant wavelengths at which roughness occurs, and consider how they correspond to the different channel components. We also consider the extent to which lithology and sediment grain size appears to affect channel morphology and roughness.
Observation-based estimates of volume, heat and freshwater exchanges between the subpolar North Atlantic interior and its boundary currents
Authors: Jones Sam , Cunningham Stuart , Fraser Neil , Inall Mark , Fox Alan
Published: March 2022

The Atlantic Meridional Overturning Circulation (AMOC) transports heat and salt between the tropical Atlantic and Arctic oceans. The interior of the North Atlantic Subpolar Gyre is responsible for the much of the water mass transformation in the AMOC, and the export of this water to intensified boundary currents is crucial for projecting air-sea interaction onto the strength of the AMOC. However, dynamical drivers of exchange between the gyre interior and the boundary remains unclear. 

We present a novel climatology of the Subpolar Gyre boundary using quality controlled CTD and Argo hydrography tracking the 1000 m isobath north of 47° N. The net geostrophic transport into the SPG perpendicular to this boundary section is only around 2.3 Sv.  Surface Ekman flow drives net transport out of the Subpolar Gyre in all seasons and shows pronounced seasonality, varying between 2.45 Sv in the summer and 7.70 Sv in the winter. Bottom Ekman transport associated with the boundary currents flows into the Subpolar gyre and is between 2.8 and 4 Sv.  

We estimate heat and freshwater fluxes into and out of the Subpolar gyre interior and compute the magnitude of water mass transformation (overturning) within the gyre. Heat advected into the Subpolar Gyre is between 0.10 PW and 0.19 PW. Freshwater exported from the gyre is between 0.06 Sv and 0.13 Sv. These estimates approximately balance the surface heat and freshwater fluxes into the region. Overturning varies between 6.20 Sv in the autumn and 10.17 Sv in the spring, meaning that approximately 40 % of the observed overturning in the subtropics can be attributed to water mass transformation in the interior of the SPG.
Peatlands of Amazonia
Authors: Wheeler Charlotte , Hergoualc’h Kristell
Published: March 2022

Substantial peat deposits are known to exist across Amazonia. The peatlands of the Pastaza-Marañon Foreland Basin in Northern Peru have received increasing attention from researchers in the past decade, however, peatlands found in other Amazonian countries remain relatively unstudied. Most notably the peatlands of Brazil and Venezuela, which are predicted to cover 260,000 km2 and 39,000 km2, respectively. Peatlands are known to be the most carbon dense terrestrial ecosystem, once soil carbon is accounted for, and due to the remote and inaccessible location of many Amazonian peatlands most of them are believed to remain relatively intact. Thus, these ecosystems are likely to harbour large stocks of carbon, which need to be protected. We review the current state of knowledge of Amazonian peatlands to test the current predictions of peat distribution and extent, assess the ecological and social importance of these ecosystems, determine the potential threats to peatlands and evaluate the existing policy and regulatory frameworks and how they may help or hinder peatland protection. Finally, we highlight key areas where further research is needed and make recommendations for policy makers, to help improve our knowledge of this important ecosystem.
Rapid intensification of Somali Jet kinetic energy prior to monsoon onset
Authors: Masiwal Rajat , Dixit Vishal , Seshadri Ashwin K
Published: March 2022

The onset of the South Asian summer monsoon is characterized by low-level cross-equatorial flow in the western Indian ocean. This flow turns eastward and becomes a zonally oriented jet off the East African coast at around 10°N, which is called the Somali Jet. The Somali jet is an important factor in the monsoon onset over the Indian region and transports moisture from the Arabian sea, playing a key role in South Asian summer monsoon rainfall. The kinetic energy (KE) of the jet has an increase that is much more rapid (a few days) than the evolution of solar insolation forcing (over a month). With the help of high-resolution reanalysis data, we explore the factors responsible for this rapid increase in kinetic energy. Using calculations of the KE budget we find that KE generation, from the scalar product of geopotential gradient and horizontal winds, has a high correlation with KE itself, and furthermore shows a rapid increase at the time of jet onset. The major contribution of this KE generation comes from the meridional component (-v∂Φ/∂y) , and is confirmed by a decomposition of generation based on EOF analysis. We demonstrate that a dominant balance between the KE generation and KE advection exists, suggesting that the boundary layer at the location of the highest KE generation is advective in nature. Furthermore, we observe that high KE generation occurs in the regime where the local Rossby number is close to 1. The meridional wind (v) is, to a good approximation, linearly proportional to the meridional component of geopotential gradient (∂Φ/∂y), and the latitude at which this relationship between v and ∂Φ/∂y is the strongest coincides with the location of the jet strength maximum (around 10°N). This strong relationship and consequent abrupt increase of the KE generation diminishes as we ascend the troposphere. Together these findings give rise to an unconventional boundary layer dynamics view of the Somali jet.
Water and vegetation in a changing environment: optimal adaptation, feedbacks and key trade-offs
Authors: Schymanski Stanislaus J. , Nijzink Remko C. , Thakur Gitanjali , Osuebi-Iyke Emmanuella , Krieger Louis , Ceolin Samuele
Published: March 2022

Vegetation responds to environmental change in many ways and at various time scales. For example, increasing atmospheric CO2 concentrations can reduce stomatal conductance and, hence, transpiration at an hourly scale, whereas adjustments in leaf area, photosynthetic capacity and root distributions follow at the daily to seasonal scale. Evidence for root growth plasticity and adaptation to soil moisture conditions can be found in field and experimental data. However, the time scales at which roots respond to a sudden change in soil moisture are not well documented, and the dynamics of root allocation in response to soil moisture changes at daily time scales is not well understood. In addition, when looking at even longer time scales, shifts in tree density and species composition may happen over decades or centuries only. These responses give rise to feedbacks with soil water resources and atmospheric conditions, affecting the entire soil-vegetation-atmosphere system on a large range of spatio-temporal scales.

Reliable projections of long-term ecosystem response to environmental change require adequate understanding and quantitative representation of the physical processes and biological trade-offs related to vegetation-environment interactions. This includes answering the following questions:

1) What is the trade-off between canopy CO2 uptake and water loss under given atmospheric conditions?

2) How much carbon do the plants need to invest into their root system, as well as water transport and storage tissues in order to achieve a certain water and nutrient supply for the canopy?

3) How quickly can root systems respond to changing conditions?

4) What are the trade-offs between carbon investments into foliage, stems and roots and returns in terms of carbon uptake by photosynthesis?

5) Do plants adapt to the environment in an optimal way in order to maximise their net carbon profit, i.e. the carbon uptake minus carbon invested into tissues needed for its uptake?

6) And finally, can vegetation behaviour be predicted by assuming a community-scale optimal adaptation for maximum net carbon profit?

Here we present promising results related to Question 6) based on the Vegetation Optimality Model (VOM), which was recently applied and tested along a precipitation gradient in Australia. We also explain the benefits of quantitative answers to Questions 1-4 and point to targeted experiments needed to address these questions, some of which will be presented separately.
 Interaction between graminoids and shrubs modify responses of these plants to warming and nitrogen addition in a boreal bog
Authors: Le Ba Thuong , Wu Jianghua
Published: March 2022

The warmer and/or nitrogen-enriched conditions may significantly affect boreal bog vascular plants. These environmental changes may also alter the vascular plant interaction that can modify the responses of the plants to the ecological changes. Here, we combined vegetation removal treatments with warming and nitrogen addition experiments to investigate the effects of the abiotic and biotic changes on the above and below-ground growth of graminoids and shrubs at a Canadian boreal bog. We found that graminoids positively responded to nitrogen addition with the increases in leaf growth, cover, and decreases in root biomass. Warming did not affect the cover and root biomass of graminoids; however, this treatment enhanced graminoid root distribution in the deeper peat layer. Shrub removal had no effect on leaf growth, cover, and root biomass of graminoids, while the removal of shrubs modified the effects of nitrogen addition and warming on graminoid root biomass and root distribution. Our results also reveal that nitrogen addition and warming stimulated the above-ground growth of boreal bog shrubs. Meanwhile, the cover of shrubs was enhanced by warming and not affected by nitrogen addition. Graminoid removal significantly affected the cover, above and below the growth of shrubs in the boreal bog. These findings highlight the significant role of graminoid and shrub interaction that regulates the responses of these plants to warming and nitrogen addition. Our results suggest an increasing trend of boreal bog vascular plants under future warmer, nitrogen-enriched conditions. The dynamics of vegetation may significantly alter the vital services of boreal bogs.
Tuning in to drought chatter: Detecting deviation from expectation
Authors: Smith Kelly Helm
Published: March 2022

Drought has a strong subjective component, incorporating an expectation about how much water there “should” be. Impacts of drought are the downstream effects of a phenomenon that is difficult to bound in space and time, but that propagates through sectors and ecosystems. Data on drought losses with a monetary value, such as commodity crops or energy production, are most readily available. Data on changes to ecosystems and other less coordinated economic activities are harder to find. The Drought Impacts Toolkit (droughtimpacts.unl.edu) curates many sources of drought-impact information. Tools hosted on the site focus on gathering and mapping what people are saying about drought via news stories, social media, crowdsourcing and citizen science. These map layers are independently informative and collectively contribute to a convergence of evidence approach to assessing drought impacts. Each represents a channel of information that captures different sets of motivations and describes drought’s effects at different temporal and spatial resolutions. Quantifying the volume of information on each channel over time -- “chatter” -- provides insight into rising and falling levels of awareness or concern about drought. Analysis of and familiarity with the relationships between what is being said on different channels and at what rates, and how they do and don’t coincide with physical phenomena, is a useful diagnostic approach. It may provide early warning of emerging drought or drought impacts, insights into how people experience the effects of drought from one place to another, underlying vulnerabilities, and potential solutions.
Effects of the Nature-Based Solutions on the ecosystem services; an evaluation of the Piave River catchment (Italy) in a 2050 scenario
Authors: Di Grazia Francesco , Galgani Luisa , Gumiero Bruna , Troiani Elena , Loiselle Steven A.
Published: March 2022

Sustainable river management should consider potential impacts on ecosystem services in decision-making with respect to mitigating future climate impacts. In this respect, there is a clear need to better understand how nature-based solutions (NBS) can benefit specific ecosystem services, in particular within the complex spatial and temporal dynamics that characterize most river catchments. To capture these changes, ecosystem models require spatially explicit data that are often difficult to obtain for model development and validation. Citizen science allows for the participation of trained citizen volunteers in research or regulatory activities, resulting in increased data collection and increased participation of the general public in resource management.

In the present study, we examined the temporal and spatial drivers in nutrient and sediment delivery, carbon storage and sequestration and water yield in a major Italian river catchment and under different NBS scenarios. Information on climate, land use, soil and river conditions, as well as future climate scenarios, were used to explore future (2050) benefits of NBS on local and catchment scales, followed the national and European directives related to water quality (Directive 2000/60/EC) and habitat (Directive 92/43/EEC). We estimate the benefits of individual and combined NBS approaches related to river restoration and catchment reforestation.
Constraining Soil Freezing Models using Observed Soil Freezing Characteristic Curves
Authors: Devoie Élise , Gruber Stephan , McKenzie Jeffrey
Published: March 2022

Objective: Estimate Soil Freezing Characteristic Curves (SFCCs) and uncertainty bounds based on a compilation of existing measured SFCCs.

Key Findings

Uncertainty in measured SFCCs is estimated based on measurement technique, water content, and soil disturbance

An open-source tool for estimating and constraining SFCCs is developed for use in parameterizing freeze/thaw models

Abstract

Cold-regions landscapes are undergoing rapid change due to a warming climate. This change is impacting many elements of the landscape and is often controlled by soil freeze/thaw processes. Soil freeze/thaw is governed by the Soil Freezing Characteristic Curve (SFCC) that relates the soil temperature to its unfrozen water content. This relation is needed in all physically based numerical models including soil freeze/thaw processes. A repository of all collected SFCC data and an R package for accessing and processing this data was presented in "A Repository of 100+ Years of Measured Soil Freezing Characteristic Curves".

This rich SFCC dataset is synthesized with a focus on potential sources of error due to the combination of measurement technique, data interpretation, and physical freeze-thaw process in a specific soil. Particular attention is given to combining sources of error and working with datasets given incomplete and missing metadata. A tool is developed to extract an SFCC for a soil with specified properties alongside its uncertainty bounds. This tool is intended for use in freeze/thaw models to improve freeze/thaw estimates, and better represent the ice and liquid water content of freezing soils. As phase change accounts for a vast majority of the energy budget in freezing soils, accurately representing the process is essential for realistic predictions. In addition, SFCC type curves are provided for the common sand, silt, clay, and organic soil textures when additional data is unavailable to define the SFCC more precisely.
Mars events polyphonic detection, segmentation and classification with a hybrid recurrent scattering neural network using InSight mission data
Authors: Barkaoui Salma , Rodriguez Bueno Angel , Lognonné Philippe , De Hoop Maarten , Sainton Grégory , Plasman Mathieu , kawamura Taichi
Published: March 2022

Since deployed on the Martian surface, the seismometer SEIS (Seismic Experiment for Interior Structure) and the APSS (Auxiliary Payload Sensors Suite) of the InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission have been recorded the daily Martian respectively ground acceleration and pressure. These data are essential to investigate the geophysical and atmospheric features of the red planet. So far, the InSight team were able to detect multiple Martian events. We distinguish two types: the artificial events like the lander modes or the micro-tilts known as glitches or the natural events like the pressure drops which are important to estimate the Martian subsurface and the seismic events used to study the interior structure of Mars. Despite the data complexity, the InSight team was able to catalog these events (Clinton et al 2020 for the seismic event catalog, Banﬁeld et al., 2018, 2020 for the pressure drops catalog and Scholz et al. (2020) for the glitches catalog). However, despite all this effort, we are still in front of multiple challenges. In fact,  the seismic events' detection is limited  due to the SEIS sensitivity, which is the origin of a high noise level that may contaminate the seismic events. Thus, we can miss some of them, especially in the noisy period. Besides, their detection is very challenging and require multiple preprocessing task which is time-consuming. For the pressure drops, the detection method used in Banﬁeld et al.  2020 is limited by a threshold equal to 0.3 Pa. Thus, the rest of pressure drops are not included. Plus, due to lack of energy, the pressure sensor was off for several days. As a result, many pressure drops were missed. As a result, being able to detect them directly on the SEIS data which are, in contrast,  provided continuously, is very important.

In this regard, the aim of this study is to overcome these challenges and thus improve the Martian events detection and provide an updated catalog automatically. For that, we were inspired of one of the main technics used today in data processing and analysis in a complete automatic way: it is the Machine Learning and particularly in our case is the Deep Learning. The architecture used for that is the “Hybrid Recurrent Scattering Neural Network” (Bueno et al 2021)  adapted for Mars
Dune length, width and orientation in the sand seas of Titan reveal regional properties
Authors: Radebaugh Jani , Rose Delaney , Wright Madeline , Lake Ben , Tass Shannon , Christiansen Eric , Rodriguez Sébastien , Turtle Elizabeth
Published: March 2022

Large linear dunes are found in great abundance across the equatorial regions of Saturn’s moon Titan. They are similar in width and spacing to the large dunes of the Saharan, Arabian and Namibian deserts, indicating atmospheric conditions, sand sizes and winds are comparable to those on Earth. An examination of their geomorphometric properties, such as length, width, spacing and distribution can reveal aspects of their relationship with wind strength and direction and controls by underlying topography. We traced long axes of about 70% of all measurable dunes, which involved over 20,000 measurements. We mapped all of the dunes in Shangri-La, Fensal, Aztlan, and half of the Belet Sand Sea. In addition, we measured 90,000 dune widths across Titan at 500 m intervals and fit a nonstationary statistical model with a Gaussian spatial process to determine correlations of dune spacings. Dune long axes are dominantly oriented E-W, a proxy for the sand flux and wind directions. Dunes range to over 400 km in length, with an average length of 40 km. The average length may reflect a rough spacing of obstacles, large-scale topographic variations, or the availability of sand. Dunes are directed slightly NE in the Belet Sand Sea, where dunes are especially abundant and wider. The longest dunes are also found here. Belet may thus represent a fully mature sand sea, where dunes are free to grow as long and large as possible. To the east is the Shangri-La sand sea, which is the location of the Dragonfly landing site. Shangri-La hosts dunes directed dramatically southward, especially near the Xanadu region margin. Dunes here are narrower and interdunes are clearly visible near the elevated rim of the Selk impact crater and other topographic obstacles. Sand collects most densely along the eastern boundary, at the margin of Xanadu, and at the downwind margins of all sand seas. This perhaps indicates that sand is transported until major boundaries are encountered that preclude sand movement. Dune width values can be divided into about 5 major (20 minor) regions globally within the sand seas, with widest groupings at the sand sea centers and isolated, narrower groupings at higher latitudes. The narrowest dunes appear to have the most obstacles or topographic control or be at the highest latitudes. However, within each cluster, dunes of any size within the 1-3 km width range can exist. These studies reveal that while local controls are impactful, dunes will ultimately grow to the extent possible under the conditions present, which on Titan are highly favorable for large linear dunes. Further examination of dune parameters can reveal details about the landscape, basement bedrock conditions, sand transport history and regional wind effects on the dunes of Titan.
The effect of irradiance on lipids of highly branched isoprenoids (HBIs) producing diatom culture of Pleurosigma intermedium: towards stable isotope proxies for the paleo sea-ice reconstructions
Authors: Gao Simin , Zhao Yu , Zhou Youping , Smik Lukas , Belt Simon , Mock Thomas , Pedentchouk Nikolai
Published: March 2022

Source-specific highly branched isoprenoids (HBIs) have been recently served as a binary or semi-quantitative biomarker to indicate the sea ice extent in the past. Since the light intensity controlled by overlying snow cover and sea ice thickness has a significant impact on the productivity of photoautotrophic organisms and environmental water is the sole source of the hydrogen for the biosynthesis of these organisms, the hydrogen isotope ratio (2H/1H) of HBIs holds the potential to reveal more characteristics of sea ice. In this study, based on the observation of natural settings underneath sea ice, diatom Pleurosigma intermedium were grown at irradiances from 20 to 300 μmol m-2 s-1 in laboratory conditions and harvested from exponential phase and stationary phase respectively to investigate the effect of light and growth phase on hydrogen isotope fractionation in HBIs. Gas chromatography-mass spectrometry (GC-MS) screening showed that a triene (C25:3) and a tetraene (C25:4) C25 HBI alkene were detected in all samples from varying irradiances. A remarkable decline of the ratio of C25:3/C25:4 from higher to lower irradiances was observed. However, there was no significant change in the concentration of C14 (myristic), C16:1 (palmitoleic) and C16 (palmitic) fatty acids with varying light intensity. In addition, terpenoids such as phytol, squalene and range of sterols were also be identified. Published studies on phytol, fatty acid and sterol from Thalassiosira pseudonana and alkenones from Emiliania huxleyi have shown dramatic changes in hydrogen isotope fractionation and concluded that the source of nicotinamide adenine dinucleotide phosphate (NADPH) and the operation of acetogenic pathway, plastidic methylerythritol phosphate (MEP) and/or cytosolic mevalonic acid (MVA) of lipids are the key factors controlling 2H/1H fractionation. The integration of molecular distribution of HBIs, fatty acids and terpenoids in Pleurosigma intermedium together with our ongoing work on their 2H/1H and 13C/12C compositions will lead to a better understanding of diatom metabolism and biochemistry under different light conditions. This knowledge will be instrumental to a more robust interpretation of stable isotope data from environmental samples and thus will contribute to further developing HBI biomarkers as a tool for estimating not only the absence/presence of sea ice but also the ice type, thickness, and snow cover.
A numerical and experimental study of Galilei-transformed nonlinear wave groups
Authors: He Yuchen , Ducrozet Guillaume , Hoffmann Norbert , Dudley John M. , Chabchoub Amin
Published: March 2022

The Galilei transformation (GT) is a universal operation connecting the fixed and translated co-ordinates of a dynamical system. When considering exact wave envelope solutions of the nonlinear Schrödinger equation (NLSE) propagating with a relative Galilei speed (GS), the GT imposes a frequency shift to satisfy the symmetry. This limits the applicability of the GT to nonlinear dispersive waves. We show that the Galilei-transformed envelope solitons and Peregrine breathers generated in a wave tank clearly deviate from their respective pure NLSE hydrodynamics. The type of discrepancies depends on the sign of the GS while these can be still quantified by the modified NLSE or solving the Euler equations. Furthermore, Galilei-transformed envelope solitons with positive GSs exhibit self-modulation. With designated GS and steepness values, such solitons can be transformed to follow the exact dynamics of higher-order solitons, which under specific circumstances are responsible for the generation of supercontinua.