bluuebunny/crossref_metadata_2025 huggingface dataset:
Compact filter system for mitigating phosphorus losses from agricultural drainage discharge
Authors: Heckrath Goswin , Pugliese Lorenzo
Published: March 2022

Phosphorus (P) losses from artificially drained agricultural land can locally contribute to surface water eutrophication. These losses are a function of hydrological processes and long-term P accumulation in soils due fertilization practices, which is why agronomic mitigation options tend to be ineffective. However, as subsurface drainage systems concentrate water flow spatially, drainage filter technologies represent a potentially cost-effective end-of-pipe mitigation practice for P losses. The aim of this study was to test such a compact, full-scale P filter system under field conditions.

The system is located in the Fensholt catchment, Denmark, and has two main compartments: a sediment filter for retaining particulate P and a porous reactive filter consisting of iron-coated sand (ICS) for dissolved P. A pump feeds drainage water from an adjacent ditch into the filter system at flow rates of typically 1-1.5 l s-1. Hydraulic loading of the system and drainage water composition were monitored continuously on a daily basis to evaluate system performance. Measurements of total P (TP), total dissolved P (TDP) and turbidity (NTU) were done. Suspended sediment was estimated in all water samples from turbidity measurements.

During the runoff season October 2020 to June 2021 the hydraulic load to the filter system was 18000 m3 corresponding to an average hydraulic retention time (HRT) for the sediment filter of 92 minutes. Total P concentrations in drainage water at the system inlet varied substantially between 0.03 and 2.47 mg P l-1, while TDP varied between 0.04 and 0.84 mg P l-1. On average TDP represented 60% of TP. The sediment filter retained 71% and 64% of the estimated sediment and PP load, respectively. However, occasionally TDP was remobilized from the sediment filter in late spring due to chemical and biological processes. The TDP retention in the ICS filter averaged 51% for the drainage season. On a monthly basis TP retention in the filter system varied between -33% and 88% averaging 61% in 2020/21. This compares positively with other end-of-pipe solutions such as constructed wetlands which tend to have lower TP retention efficiencies under Danish conditions. However, the effective storage capacity of the compact P filter system has to be better understood including the mechanisms of potential P release processes and the required frequency of filter cleaning.
Seasonal variability and magnitude of soil CO2 fluxes in a warming experiment in a secondary subtropical forest in Hong Kong
Authors: Lou Duo , Liang Naishen , Lai Derrick Yuk Fo
Published: March 2022

The increase of CO2 in the atmosphere has led to warming of the Earth’s surface and other climate changes. As heterotrophic respiration has great potential to increase atmospheric CO2 concentrations, it is important to quantify the variation in soil CO2 emission and to find its control factors under climate change. Though there are numerous studies about the warming effect on soil CO2 fluxes, the duration and variation of the effect remains unclear in subtropical forests. Here, we conducted a soil warming experiment with a multichannel automated chamber system in a secondary subtropical broad-leaved evergreen forest in Hong Kong. 15 chambers were set up in forest and were divided into 3 treatments, including a control, a root trenching, and an infrared-warming with root trenching chamber to determine the effect of warming on soil heterotrophic respiration in forest.

So far, after 3-year warming, soil temperature at 5 cm depth was increased by 2.47 °C, compared with the control chambers. Soil CO2 fluxes in experimental warming chambers have been significantly stimulated by 33.06%. There is significant relationship between soil temperature and soil CO2 fluxes in all the treatments, while in heating chambers, the relationship was weaker. The warming effect on soil CO2 emission was high in hot and humid summer, indicating that summer precipitation and the resulting soil moisture level also strongly influenced the soil warming effect in this forest. A moderately strong relationship was only found between soil moisture and temperature-normalized CO2 flux data in trenched chambers in 2020, when annual precipitation was the highest among 3 years. We found a significant reduction in the warming effect on soil respiration and highest Q10 values for soil respiration and its components in 2021, when annual precipitation was the lowest. Experimental warming significantly decreased Q10 value for heterotrophic respiration, which may be due to the reduction of soil moisture. Cross-correlation analysis showed that there was evident diel hysteresis between CO2 and soil temperature, while no significant seasonal hysteresis was observed. Longer-term monitoring on soil respiration under warming conditions is still needed to confirm if the reduction of warming effect is caused by microbial acclimation in our site.
Dynamic topographic observations of Antarctica and its fringing oceanic basins
Authors: Dunn Aisling , White Nicky , Holdt Megan , Larter Robert
Published: March 2022

Constraining the dynamic topography of Antarctica and its surrounding seas is required in order to gauge the pattern of mantle convection beneath this continent. However, such studies are limited by this continent’s geographical remoteness, by the lack of bedrock exposure and by extensive glaciation. Oceanic residual depth measurements provide a well-established proxy for offshore dynamic topography. Here, over 400 seismic reflection profiles have been interpreted to calculate residual depth measurements throughout the oceans that surround Antarctica. These measurements have been carefully corrected for sedimentary loading and, where possible, for crustal thickness variations. When combined with previous global compilations, these new residual depths significantly improve spatial resolution across the region, providing excellent constraints on dynamic topographic basins and swells. In the continental realm, an improved understanding of dynamic topography will help to quantify temporal and spatial variations in ice sheet stability. Volcanism and slow shear wave velocity anomalies beneath the continent indicate dynamic support.  By mapping offshore dynamic topography to a higher resolution, greater context is provided for future onshore studies.
Modeling the impacts of bottom trawling on the sediment and particulate organic carbon distribution of the North Sea
Authors: Porz Lucas , Yilmaz Rumeysa , Kossack Jan , Zhang Wenyan , Schrum Corinna
Published: March 2022

Bottom trawling, a fishing practice that entails the dragging of heavy fishing gear along the seafloor, is one of the most direct human interferences with the marine environment. Bottom trawling is known to resuspend a large amount of sediment, thereby releasing nutrients, organic carbon and contaminants to the water column. However, the large-scale effects of bottom trawling on sediment and carbon fluxes have remained difficult to quantify. We aim to quantify these fluxes through numerical modeling of bottom trawling activity in the North Sea. A particular focus is put on muddy areas rich in organic carbon, as chronic bottom trawling could inhibit their function as carbon sinks. By combining a three-dimensional, coupled hydrodynamics and sediment transport model with data of trawling effort in the study area, we parametrize the resuspension caused by bottom trawling on the basis of individual vessels and the subsequent transport of resuspended material by ocean currents. Results show that bottom trawling has potentially large impacts on the inventories and fluxes of suspended matter and organic carbon of the North Sea. The results may be useful in determining areas worthy of protection in the context of marine spatial planning.
Mechanical properties of shale following saturation with CO2 and CO2-based fluids: experimental and modeling study
Authors: Xie Bingbin , Lyu Qiao , Tan Jingqiang , Wood David
Published: March 2022

Impacts of saturation with CO2 and CO2-based liquids are vital for understanding shale's mechanical properties associated with supercritical-CO2 optimized shale gas extraction and geological capture and storage of CO2 in shale reservoirs. A sequence of triaxial compression tests is performed to examine the impact of subcritical CO2, supercritical CO2, subcritical CO2-water, supercritical CO2-water, subcritical CO2-NaCl, and supercritical CO2-NaCl saturation on shale strength. A statistical damage constitutive model of shale after CO2, CO2-water, and CO2-NaCl saturation is established to describe shale's stress-strain relationships under various immersion conditions.

The laboratory findings indicate that the change of the axial stress, Young's modulus, and axial strain of shale after immersion verifies the physical and chemical reactions that occur between shale and the soaking fluids. Mechanical properties of shale show the greatest variations after CO2-water saturation. The variation in mechanical properties of shale after CO2-NaCl saturation is smaller than those of shale under CO2-water saturation owing to the precipitation of NaCl crystals. Pure CO2 saturation has the smallest influence on shale's mechanical properties among the three types of liquids assessed. CO2 in a supercritical state shows a stronger impact on shale than the subcritical state for the same sort of fluids. Also, following saturation, all the shales display a mixed tensile-shear failure mode. The cohesion force of shale increments following pure CO2 saturation, whereas it diminishes following CO2-water and CO2-NaCl saturation. Decreases in the internal friction angles are observed for all the soaked shales. The anisotropy of shale leads to a slight difference between the actual failure angle and the failure angle measured by the Mohr-Coulomb criterion.

The stress-strain relationship of shale under different confining pressures is effectively described by the Weibull probability distribution and the principle of strain equivalence. This establishes statistical damage constitutive equations of shale under different soaking conditions. The values of key modeling parameters, including F0 and m, are highly dependent on the brittleness and strength of shale associated with various soaking conditions.
Laboratory simulations of Martian Southern Spring : the outcome of CO2 cold jets
Authors: Cesar Camila , Pommerol Antoine , Thomas Nicolas , Portyankina Ganna , Hansen Candice J.
Published: March 2022

Orbital data from the Colour and Stereo Surface Imaging System (CaSSIS) onboard the ExoMars Trace Gas Orbiter showed interesting images of the circumpolar areas during spring. The winter-formed dusty CO2 ice cap goes under self-cleaning processes producing a translucent slab. With grazing spring sunlight, it starts to sublimate at the base and from overpressure, cold jets erupt leaving erosion marks in the underlying substrate and dust/sand deposits at the surface. This model, proposed by Kieffer, is commonly accepted to explain dark spots and fans deposits as well as spiders.

To test different aspects of this model, we combine observational data from CaSSIS with experimental work for which Martian temperature and pressure at high latitudes could be reached in a simulation chamber. Preliminary results on sinking analogous dust material (MGS-1) on a CO2 ice slab have been promising. We aim to quantify in better details the sinking ratio, colour variations and frost (H2O and/or CO2) depositions on CO2/MGS-1 samples under various setup conditions (illumination, material distribution). Using a hyperspectral device, we can measure the reflectance and simulate the CaSSIS signal in the different filters (PAN, NIR, RED, BLU) to compare to actual images that have been acquired during southern spring. 
Experimental deformation of talc at near-seismic deformation rates
Authors: Horn Charis , Skemer Philip
Published: March 2022

Talc is a hydrous magnesium silicate with an extremely low coefficient of friction.  In recent years, the recognition that talc is present in many fault systems has led to the suggestion that talc strongly influences the strength of faults.  To understand the role of talc in the seismic cycle, we conducted high pressure and temperature torsional deformation experiments on specimens of natural talc at shear strain rates relevant to slow-slip earthquakes (~10-4 s-1).  Scanning transmission electron microscopy revealed decreasing talc grain sizes (from ~3-5 mm to <100 nm), alongside delamination and kinking of individual talc grains.  This microstructural evolution with progressive strain greatly increases the density of planar defects (including grain-boundaries), and is consistent both with observations of natural, talc-rich faults, and prior experimental work.  Nanoindentation tests at room temperature were performed on deformed specimens to assess precisely whether the observed microstructural changes also affect rheology. At these conditions, nanoindentation is assumed to produce deformation predominantly by intercrystalline frictional slip.  However, bulk hardness data determined from nanoindentation show that there is no change in indentation hardness with increasing strain or defect density, both for indents made parallel to and perpendicular to the shear plane.  Although the talc grains become increasingly damaged with strain, the overall strength of deformed talc does not change.  This suggests that accumulated slip on talc-bearing faults does not change their mechanical response or hazard potential.
Seasonal forecast skill of upper-ocean heat content in coupled high-resolution systems
Authors: McAdam Ronan , Masina Simona , Balmaseda Magdalena Alonso , Gualdi Silvio , Senan Retish , Mayer Michael
Published: March 2022

Seasonal forecasts of marine variables are not used nor validated to the same level that atmospheric variables are, despite their great potential for the planning of maritime activities. Ocean heat content (OHC) anomalies, for example, typically persist for several months, making this variable a vital component of seasonal predictability in both the ocean and the atmosphere. However, the ability of seasonal forecasting systems to predict OHC remains largely untested. Here, we present a global assessment of OHC predictability in two state-of-the-art and fully-coupled seasonal forecasting systems. Overall, we find that dynamical systems make skilful seasonal predictions of OHC in the upper 300m across a range of forecast start times, seasons and dynamical environments. Predictions of OHC are typically as skilful as predictions of sea surface temperature (SST), providing further proof that accurate representation of subsurface heat contributes to accurate surface predictions. We also compare dynamical systems to a simple anomaly persistence model to identify where dynamical systems provide added value over cheaper forecasts; this largely occurs in the equatorial regions and the tropics, and to a greater extent in the latter part of the forecast period. Regions where system performance is inadequate include the sub-polar regions and areas dominated by sharp fronts, which should be the focus of future improvements of climate forecasting systems.

Lastly, we describe efforts to encourage the use of marine variables in operational seasonal forecasting, as part of the European Union Horizon 2020 EuroSea project. We present encouraging results on the predictability of marine heat waves using OHC, which marks the first step of our strategy to provide forecasts of stakeholder-defined indicators.
Overflow Water Pathways in the North Atlantic: New Observations from the OSNAP Program 
Authors: Lozier Susan , Bower Amy , Furey Heather , Drouin Kimberley , Xu Xiaobiao , Zou Sijia
Published: March 2022

As part of the international Overturning in the Subpolar North Atlantic Program (OSNAP), 135 acoustically-tracked deep floats were deployed from 2014 to 2016 to track the spreading pathways of Iceland-Scotland Overflow Water (ISOW) and Denmark Strait Overflow Water (DSOW). These water masses, which originate in the Nordic Seas, compose the deepest branch of the Atlantic Meridional Overturning Circulation. The OSNAP floats provide the first directly observed, comprehensive Lagrangian view of ISOW and DSOW spreading pathways throughout the subpolar North Atlantic. Contrary to a decades-long expectation for how these deep water masses move equatorward, the collection of OSNAP float trajectories, complemented by model simulations, conclusively reveals that their pathways are (a) not restricted to western boundary currents, and (b) remarkably different from each other in character. The spread of DSOW from the Irminger Sea is primarily via the swift deep boundary currents of the Irminger and Labrador Seas, whereas the spread of ISOW out of the Iceland Basin is slower, more diffusive, and along multiple export pathways. The characterization of these overflow water pathways has important implications for our understanding of the Atlantic Meridional Overturning Circulation (AMOC) and its variability. Finally, reconstructions of AMOC variability from proxy data, involving either the strength of boundary currents and/or the property variability of deep waters, should account for the myriad pathways of DSOW and ISOW, but particularly so for the latter.

 
Dynamics of deep-submarine explosive eruptions
Authors: Newland Eric , Mingotti Nicola , Woods Andrew
Published: March 2022

Deposits from explosive submarine eruptions have been found in several deep-sea locations, with both flow and fall deposits of small clasts, 1-3mm, extending 1000’s m over the seafloor. Here we propose that after mixing with seawater, the erupting fragmented material typically forms a negatively buoyant fountain. To explore their dynamics, we present a simple numerical model to describe the evolution of the eruption column and series of laboratory experiments of turbulent particle-laden fountains rising through a stratified water column.  Our experiments show that at the top of the fountain, some of the erupted material collapses to the seafloor to form a pyroclastic flow. However, some of the buoyant water in the fountain may separate from the top of the fountain, to form a buoyant plume which can carry particles higher into the water column. Eventually this mixture will be arrested by the ambient stratification and intrudes into the water column. Subsequently, the particles settle from this intrusion to form a fall-type deposit. Quantification of the controls on the concurrent fall and flow deposits, and comparison with field observations, including from the 2012 eruption of Havre Volcano in the South Pacific, open the way to new understanding of submarine eruptions.
Developing a data-driven ocean forecast system
Authors: Furner Rachel , Haynes Peter , Jones Dan , Munday Dave , Paige Brooks , Shuckburgh Emily
Published: March 2022

The recent boom in machine learning and data science has led to a number of new opportunities in the environmental sciences. In particular, process-based weather and climate models (simulators) represent the best tools we have to predict, understand and potentially mitigate the impacts of climate change and extreme weather. However, these models are incredibly complex and require huge amounts of High Performance Computing resources. Machine learning offers opportunities to greatly improve the computational efficiency of these models by developing data-driven emulators.

Here I discuss recent work to develop a data-driven model of the ocean, an integral part of the weather and climate system. Much recent progress has been made with developing data-driven forecast systems of atmospheric weather, highlighting the promise of these systems. These techniques can also be applied to the ocean, however modelling of the ocean poses some fundamental differences and challenges in comparison to modelling the atmosphere, for example, oceanic flow is bathymetrically constrained across a wide range of spatial and temporal scales.

We train a neural network on the output from an expensive process-based simulator of an idealised channel configuration of oceanic flow. We show the model is able to learn well the complex dynamics of the system, replicating the mean flow and details within the flow over single prediction steps. We also see that when iterating the model, predictions remain stable, and continue to match the ‘truth’ over a short-term forecast period, here around a week.

 
Seismic evidence for a 1000-km mantle discontinuity under the Pacific
Authors: Zhang Zhendong , Irving Jessica , Simons Frederik , Alkhalifah Tariq
Published: March 2022

Seismic discontinuities in the mantle are indicators of its thermo-chemical state and offer clues
to its dynamics. Ray-based imaging methods, though limited by the approximations made, have
mapped mantle transition zone (MTZ) discontinuities in detail, but have yet to offer definitive
conclusions on the presence and nature of mid-mantle discontinuities. We use a waveequation-
based imaging method to image both MTZ and mid-mantle discontinuities, and
interpret their physical nature. We focus on precursors to the surface-reflected seismic phases
PP, SS, PS, and SP to produce images of deep reflectors using reverse-time migration (RTM),
employing the full-waveform tomographic model GLAD-M25 for wavefield extrapolation. Our
adjoint-based inverse modeling accounts for more of the physics of wave propagation than raybased
stacking methods, which leads to improved accuracy and realistic precision of the
obtained images. The relative amplitude and location of the imaged reflectors are indeed well
resolved, but an interpretation of absolute amplitudes in terms of reflection coefficients
remains elusive. We observe a thinned mantle transition zone southeast of Mauna Loa, Hawaii,
and a reduction in impedance contrast around 410 km depth in the same area. These
observations coincide with anomalously low S-wavespeeds in the background tomographic
model, suggesting a hotter-than-average mantle in the region. Our new images furthermore
reveal a 4000—5000 km-wide reflector in the mid mantle below the central Pacific, at 950—
1050 km depth. This discontinuity displays strong topography and is marked by a polarity
opposite to that of the 660-km discontinuity, implying an impedance reversal near 1000 km.
We speculate that this mid-mantle discontinuity is linked to the mantle plumes rising from the
large low shear-velocity province (LLSVP) at the base of the mantle below this region. Some
seismic tomography models are in support of this interpretation, while others remain at odds---
a discrepancy that our observations may help resolve.
Fluid-rock interactions at high-pressure metamorphic conditions: An analysis of atoll-garnets preserved in eclogitic breccias from the Zermatt-Saas zone, Italian Alps.
Authors: Lecacheur Kilian , Fabbri Olivier , Hertgen Solenn , Leclere Henri
Published: March 2022

In the Piemonte-Liguria ophiolites of the western Alps, the Zermatt-Saas unit is characterized by a widespread eclogite facies metamorphism. Eclogitic rocks are derived from basaltic or gabbroic protoliths. Peak metamorphic conditions are indicated by omphacite, almandine-rich garnet, rutile and Fe-poor epidote assemblages, which allow to infer temperatures between 550 and 600°C and pressures up to 2.5 GPa.
This aim of this contribution is to report the results of a petrologic analysis of an eclogitic breccia exposed in the Zermatt-Saas unit in the Monte Avic area, Aosta valley. The fragments consist of eclogitic gabbro, while the matrix is made of omphacite locally retromorphosed into blueschist to greenschist facies assemblages. Clasts are characterized by abundant atoll-shaped garnets. Two types of atoll-shaped garnets are distinguished: type I garnets consist of an almandine-rich unzoned core, a finely oscillatory zoned rim with alternating grossular-rich and almandine-rich overgrowths, and omphacite between core and rim. Type II garnets are similar to type I garnets, the only difference being titanite (+/- epidote) between core and rim. The atoll-shaped garnets result from two episodes of fluid-mineral interactions. For type I garnets, these interactions took place under high-pressure conditions (stability of omphacite), and under medium-pressure conditions (stability of titanite) for type II garnets.
Brecciation is characterized by pervasive fracturing. The two types of atoll-shaped garnets are fractured. The fractures are sealed by omphacite. This shows that brecciation took place after the formation atoll-shaped garnets. On-going investigations aim at identifying the chemical signature of the reacting fluids and estimating precise pressure and temperature conditions of fluid-mineral interactions.
Does impact climate change the Peruvian upwelling system?
Authors: Yari Sadegh , Mohrholz Volker
Published: March 2022

The Peruvian upwelling system (PUS) is the most productive marine ecosystem among the Eastern Boundary upwelling Systems (EBUS). The trade wind system of the South Pacific drives a nearly continuous upwelling which is subjected to variations on a wide range of times scales. The intensity and variability of upwelling control crucially the nutrient supply to the euphotic surface layer and thus, the overall productivity of the system.

Using long-term wind data (1950-2019) and SST data from ERA5, the upwelling components were analyzed to obtain information about decadal trends in the mean state and their variability. The HYCOM model data (GOFS 3.1 expt_53.X) for the period of 1994-2015 is also analyzed to estimate the Ekman transport in the coastal area and Ekman pumping due to wind stress curl.
Besides the strong annual cycle, the wind forcing is dominated by interannual and interdecadal oscillation. The interannual fluctuations with a period of 2-5 years are related to the known events of El Niño and La Niña. The wind anomaly shows a good correlation with Oceanic Niño Index (ONI). Interdecadal variation of wind depicts a period of 15-20 years with negative anomaly for 1950-1976, slightly positive for 1977-1982, negative for  1983-1996, and strong positive anomaly for 1996-2014. These long-term variations can be attributed to the Interdecadal Pacific Oscillations (IPO). The spatial distribution of wind stress along the Peruvian coast depicts a local maximum in the Lima-Marcona area (12º-15.4º S) decreasing sharply southward and gradually northward. The wind stress anomaly and SST anomaly are highly correlated in the coastal area. The alongshore wind stress reveals a positive trend in either negative or positive phases of IPO. Moreover, there are two sharp shifts during 1996 and 2015. These can be related somehow to climate warming and climate shifts which are already addressed by various authors. 

Additionally, the characteristics of the circulation in the coastal belt off Peru are derived from HYCOM outputs. Ekman transport and Ekman pumping from both wind data and model output are in good agreement. The water masses distribution shows annual as well as inter-annual variations mainly due to El Niño and La Niña events that apply to the mixed layer depth too.
Topsoil SOC stocks in Pyrenean snowbeds
Authors: Roca Núria , Illa Estela , Pla Roser , Guinot Melissa , Ninot Josep Maria
Published: March 2022

Snowbed ecosystems in temperate mountains are threatened by surrounding chionophilous grasslands, triggered by the longer growing season and higher temperatures induced by climate change. Such vegetation shift would imply future changes in edaphic biogeochemical processes that could modify CO2 emissions. To assess the role of snowbeds in terms of carbon storage, we sampled three soil profiles along the snowmelt gradient under different vegetation types (grassland and snowbed) and species (the dwarf shrub Salix herbacea and the dominant grass at plot level) in three non-calcareous Pyrenean localities. We measured soil organic carbon (SOC), pH, bulk density and texture. The soils studied were characterized by low pH and high total soil organic carbon (TOC), which is more abundant at early snowmelting profiles and at the topsoil. Soils on shales had the highest TOC mean values and the lowest variability (10.7%±0.11 at the topsoil), although no significant differences were observed between plots under different vegetation types. SOC stock was between 18-46 MgC·ha− 1 at the first 5 cm of early snowmelting topsoil with Salix herbacea, whereas at the late snowmelting topsoil with grasses it was between 17-37 MgC·ha− 1. Our results show that TOC is mainly explained by the situation along the snowmelt gradient, soil depth, and parent material, and suggest that changes in snow cover duration will translate into higher TOC accumulation in current snowbed patches.
Experimental constraints on the nature of multiphase solid inclusions and their bearing on mantle wedge metasomatism, Bohemian Massif
Authors: Acosta Vigil Antonio , Kotková Jana , Copjaková Renata , Wirth Richard , Hermann Jörg
Published: March 2022

Fluids are the primary agents for mass transfer in subduction zones. These fluids can be captured as primary inclusions within minerals crystallizing during subduction processes. Some of these inclusions, referred to as multiphase solid inclusions (MSI), are characterized by the high proportion and variety of minerals, hence by a high concentration of solute in the trapped fluid. Kotková et al. (2021) have described primary MSI in garnets of subduction-related ultra-high pressure (UHP) peridotites (P-T of 1030-1150 ºC/3.6-4.8 GPa) of the Bohemian Massif. MSI range in size between ≈5-40 µm and are mostly composed of hornblende, the barian mica kinoshitalite, dolomite and magnesite. MSI have been interpreted as trapped residual liquids produced after partial UHP crystallization of carbonate-silicate melts that now form garnet pyroxenite veins in the peridotites. Experimental re-melting of MSI is the best procedure to investigate the precise nature of trapped fluids. We have conducted re-melting experiments of MSI present in garnets of a lherzolite, taking the inclusions to P-T around their entrapment conditions at or close to host rock peak P-T, 4-4.5 GPa and 1000-1225 ºC. The inclusions (re-)crystallized into a garnet fringe at the boundary between inclusions and host garnet, barian mica and carbonatite melt towards the center of the inclusion, and a large irregular and empty space in between the garnet fringe and the central silicate-carbonate component. Microstructures and mass balance indicate that the empty space was occupied by a Na-K-Cl-F-rich saline aqueous fluid (brine). Hence experiments did not produce a single melt at any experimental conditions, but systematically show the stability and coexistence of barian mica + carbonatite melt + brine at the entrapment conditions, and a garnet fringe indicating reaction between trapped fluids and host garnet. This suggest that growing garnet trapped a carbonatite melt and a saline aqueous fluid coexisting in the matrix, together with solid crystals of barian mica likely produced by metasomatism of the percolating fluids through the host peridotite. It is intriguing, however, that neither single mica crystals nor separate former carbonate melt and brine have been found included in garnets. Mass balance shows that carbonate melt is the main host for incompatible elements such as Ba. This presentation will discuss the bearings of the experimental results on the nature and origin of these MSI, potential links to diamond formation and their implication on mass transfer processes in subduction zones.

Kotkova et al. (2021) Lithos 398-399, 106309
A workflow to standardize collection and management of large-scale data and metadata from environmental observatories
Authors: O'Ryan Dylan , Varadharajan Charuleka , Alper Erek , Boye Kristin , Burrus Madison , Christianson Danielle , Cholia Shreyas , Crystal-Ornelas Robert , Damerow Joan , Dong Wenming , Elbashandy Hesham , Faybishenko Boris , Hendrix Valerie , Johnson Douglas , Kakalia Zarine , Versteeg Roelof , Williams Kenneth , Wong Catherine , Agarwal Deborah
Published: March 2022

The Watershed Function Scientific Focus Area (WFSFA) is a U.S. Department of Energy research project that seeks to determine how mountainous watersheds retain and release water, carbon, nutrients, and metals. The WFSFA maintains a community field observatory at its primary field site in the East River, Colorado. The WFSFA collects diverse environmental data and has developed a “Field-Data” workflow that standardizes data management across the project, from field collection to laboratory analysis to publication. This workflow enables the WFSFA to address data quality and management challenges that environmental observatories face. 

Through this workflow, the WFSFA has increased the use of the data curated from the project by (1) providing detailed metadata with unique identifiers for samples, locations, and sensors, (2) streamlining the data sharing and publication process through early sharing of data internally within the team and publication of data on the ESS-DIVE repository following curation, and (3) adopting machine-readable and FAIR community data standards (Findability, Accessibility, Interoperability, Reusability). 

We describe an example application of this workflow for geochemical data, which utilizes a community geochemical data standard for water-soil-sediment chemistry (https://github.com/ess-dive-community/essdive-water-soil-sed-chem) developed by Environmental Systems Science Data Infrastructure for a Virtual Ecosystem (ESS-DIVE). This data standard is designed to standardize geochemical data, metadata, and file-level metadata, and was applied to WFSFA geochemical data, including ICP-MS, Isotope, Ammonia-N, Anion, DIC/NPOC/TDN datasets. This ensures important metadata is contained within the data file, such as precision of data analysis, storage and sample processing information, detailed sample names, material information, and unique identifiers associated with the samples (IGSNs). This metadata is essential to understand and reuse data products, as well as enable machine-readability for future model applications. Detailed examples of the standardized geochemical data types were created and are now being used as templates by WFSFA researchers to standardize their geochemical data. The adoption of this community geochemical data standard and more broadly the Field-Data workflow will improve the findability and reusability of WFSFA datasets. 
Instantaneous fractal dimensions and stability properties of geomagnetic indices based on recurrence networks and extreme value theory
Authors: Donner Reik , Alberti Tommaso , Faranda Davide
Published: March 2022

An accurate understanding of dynamical similarities and dissimilarities in geomagnetic variability between quiet and disturbed periods has the potential to vastly improve Space Weather diagnosis. During the last years, several approaches rooted in dynamical system theory have demonstrated their great potentials for characterizing the instantaneous level of complexity in geomagnetic activity and solar wind variations, and for revealing indications of intermittent large-scale coupling and generalized synchronization phenomena in the Earth’s electromagnetic environment. In this work, we focus on two complementary approaches based on the concept of recurrences in phase space, both of which quantify subtle geometric properties of the phase space trajectory instead of taking an explicit temporal variability perspective. We first quantify the local (instantaneous) and global fractal dimensions and associated local stability properties of a suite of low (SYM-H, ASY-H) and high latitude (AE, AL, AU) geomagnetic indices and discuss similarities and dissimilarities of the obtained patterns for one year of observations during a solar activity maximum. Subsequently, we proceed with studying bivariate extensions of both approaches, and demonstrate their capability of tracing different levels of interdependency between low and high latitude geomagnetic variability during periods of magnetospheric quiescence and along with perturbations associated with geomagnetic storms and magnetospheric substorms, respectively. Ultimately, we investigate the effect of time scale on the level of dynamical organization of fluctuations by studying iterative reconstructions of the index values based on intrinsic mode functions obtained from univariate and multivariate versions of empirical mode decomposition. Our results open new perspectives on the nonlinear dynamics and (likely intermittent) mutual entanglement of different parts of the geospace electromagnetic environment, including the equatorial and westward auroral electrojets, in dependence of the overall state of the geospace system affected by temporary variations of the solar wind forcing. In addition, they contribute to a better understanding of the potentials and limitations of two contemporary approaches of nonlinear time series analysis in the field of space physics.
Methane source-sink behaviour in upland trees spanning a global climate gradient
Authors: Gauci Vincent , Pangala Sunitha , Shenkin Alexander , Barba Josep , Bastviken David , Figueiredo Viviane , Gomez Carla , Enrich-Prast Alex , Sayer Emma , Stauffer Tainá , Welch Bertie , Allen Myles , Malhi Yadvinder
Published: March 2022

Forests play an important role in the exchange of radiatively important gases with the atmosphere. Previous studies have shown that in both temperate and tropical wetland forests tree stems are significant sources of methane, yet little is known about tree stem trace greenhouse gas dynamics in drier, free-draining soils that dominate global forested areas. Here, we examine methane fluxes on tree stems spanning a climate gradient of upland forests and floodplain forest across 4 locations in the Amazon, Brazil (Cunia, Rios Negro, Solimoes and Tapajos), lowland tropical forest on free-draining soils in Panama, Central America (Barro Colorado Nature Monument), deciduous woodland in the United Kingdom (Wytham, Oxfordshire) and boreal forest in Sweden. We found that trees behaved as both methane sources (near the tree base) and sinks (higher up the tree stem) across tropical, temperate and boreal sites and are highly variable, yet we were able to identify a broad correlation between the size of tree stem methane uptake fluxes and mean annual temperature across the climate gradient. The vertical spatial patterns of flux up the individual measured trees and climate gradient temperature-methane flux relationship together with revised LiDAR derived tree surface allometry permitted global scaling of fluxes in upland forest. Results of this scaling together with the implications of this refined understanding of the global methane cycle under various scenarios are discussed.
The response of ENSO teleconnections to future dynamical and thermal changes
Authors: Tyrrell Nicholas , karpechko Alexey
Published: March 2022

Future climate change will lead to both dynamical and thermal changes to the atmosphere, and these changes will affect the transmission and impact of ENSO-related teleconnections. As the dynamical atmospheric changes are a response to the radiatively-forced temperature changes, it is difficult to separate these effects. In this study we use a novel nudging technique to separately apply the future thermal and dynamical changes from CMIP6 models to the ECHAM6 atmospheric model.

First there is a training stage where the atmospheric model is nudged to a chosen future climate, and the nudging tendencies are recorded. In the second stage the nudging tendencies for temperature and winds can be applied individually or together to replicate different aspects of the future climate. During the second stage the nudging tendencies are independent of the current model state. This means that idealised ENSO SST experiments can be performed within the constructed future climates, and the model can respond to those perturbations. The study focuses on the how ENSO teleconnections, particularly relating the northern hemisphere polar vortex, will respond to future thermal and dynamical changes.
Multivariate post-processing of temporal dependencies with autoregressive and LSTM neural networks
Authors: Tolomei Daniel , Dirksen Sjoerd , Whan Kirien , Schmeits Maurice
Published: March 2022

We consider the problem of post-processing forecasts for multiple lead times simultaneously. In particular, we focus on post-processing wind speed forecasts for consecutive lead times (0 - 48h ahead) from the deterministic HARMONIE-AROME NWP model. Given the strong temporal dependency between forecasts at consecutive lead times, it is essential to model the problem as a multivariate statistical post-processing problem in order to take this temporal correlation into account.

A standard procedure in multivariate statistical post-processing is to produce multiple probabilistic forecasts independently for each lead time and introduce the dependency between them at a later stage using an empirical copula. For our specific problem, a successful example of this approach is to use EMOS to fit truncated normal marginal distributions at each lead time and then model the joint distribution by drawing samples from these distributions and reconstructing the temporal dependencies using the Schaake Shuffle.

Our aim is to explore alternative methods that can model and exploit temporal dependencies more explicitly with the goal of improving forecast performance and moving away from sample based distribution modelling. We develop two new methods that produce multivariate truncated normal probabilistic forecasts for all lead times simultaneously, by combining elements from time series analysis and artificial neural networks.

In our first method, we exploit the autoregressive dependencies in the residuals of the NWP wind speed forecasts to deduce an explicit multivariate model. By using a neural network to determine the parameters of this model, we arrive at our first method, which we coin ARMOSnet.

In our second method, we apply Long Short-Term Memory networks, which rank among the state-of-the-art tools for the forecasting of time series. We adapt the LSTM architecture to output a multivariate density that models the temporal dependencies between the consecutive lead times.

We compare our two methods to EMOS combined with the Schaake Shuffle for post-processing wind speed forecasts from the HARMONIE-AROME NWP model. Our new methods both outperform the EMOS-Schaake Shuffle approach in terms of the logarithmic, energy, and variogram scores. Among the two new methods, ARMOSnet exhibits the best performance.

 
Airflow dynamics and sediment transport through foredune blowouts 
Authors: O Keeffe Nicholas , Delgado-Fernandez Irene , Jackson Derek , Costas Susana , Farrell Eugene , O’Neil Aneurin , Smyth Thomas
Published: March 2022

Coastal dunes are effective natural buffers against climate change-induced sea-level rise and storminess. Coastlines characterised by the presence of blowouts at the beach-dune interface may be more susceptible to coastline retreat through the enhanced landward transport of beach and foredune sediment. Blowouts are highly effective transport pathways, but the dynamics of aeolian sediment transport governing their evolution are poorly understood. Their morphological form is indicative of aeolian transport, and the propensity of their topography to modify airflow sufficiently to support transport has been extensively researched. Although there is a growing number of studies detailing blowout sediment flux, those involving synchronous measurement of flow and sediment movement from the beach into the dune field are rare.

This study examined airflow and sediment transport dynamics at the beach-dune interface of a trough blowout at Sefton Dunes, northwest England. A dense array of 3D sonic anemometers were co-located with transport sensors and deployed during an oblique onshore wind event. Instantaneous flow and transport dynamics were measured on the back beach, the adjacent upwind foredune, and within the throat of the blowout. Strong alongshore deflected airflow across the upwind foredune led to high-intensity sediment transport into the blowout throat. Inside the blowout throat, airflow and transport displayed extremely high spatial and temporal variability across the relatively confined throat area. Airflow speeded up close to the upwind blowout wall but sped ‘down’ close to the exposed (downwind) blowout wall. Transport (expressed in counts min-1 and Activity Parameter) showed low correlations with a range of wind variables such as wind speeds and TKE. Transport intensity followed a general pattern opposite wind speeds, with lower transport intensities close to the upwind blowout wall and higher transport intensities close to the downwind blowout wall area. Multiple topographically-forced flow modifications were observed (particularly at the blowout throat), and relatively minor 10-20° directional shifts led to large variations in flux intensity within the blowout. Results have provided detailed, high temporal, and spatial insights into how beach sediment is delivered to the blowout throat area and then driven landwards and reveals how foredune blowouts help facilitate beach sediment bypassing through foredunes, contributing to medium-scale coastal dune evolution behaviour.
Relative Dispersion with Finite Inertial Ranges
Authors: LaCasce Joe , Meunier Thomas
Published: March 2022

The relative dispersion of pairs of particles was first considered in a seminal article by Richardson (1926). The dispersion subsequently was subsequently linked to turbulence, and pair separation statistics can advantageously be used to deduce energy wavenumber spectra. Thus one can, for example, employ surface drifters to identify turbulent regimes at scales well below those resolved by satellite altimetry. The identification relies on knowing how dispersion evolves with a specific energy spectrum. The analytical predictions commonly used apply to infinite inertial ranges, i.e. assuming the same dispersive behavior over all scales. With finite inertial ranges, the metrics are less conclusive, and often are not even consistent with each other.

We examine this using pair separation probability density functions (PDFs), obtained by integrating a Fokker-Planck equation with different diffusivity profiles. We consider time-based metrics, such as the relative dispersion, and separation-based metrics, such as the finite scale Lyapunov exponent (FSLE). As the latter cannot be calculated from a PDF, we introduce a new measure, the Cumulative Inverse Separation Time (CIST), which can. This behaves like the FSLE, but advantageously has analytical solutions in the inertial ranges. This allows establishing consistency between the time- and space-based metrics, something which has been lacking previously.

We focus on three dispersion regimes: non-local spreading (as in a 2D enstrophy inertial range), Richardson dispersion (as in the 3D and 2D energy inertial ranges) and diffusion (for uncorrelated pair motion). The time-based metrics are more successful with non-local dispersion, as the corresponding PDF applies from the initial time. Richardson dispersion is barely observed, because the self-similar PDF applies only asymptotically in time. In contrast, the separation-based CIST correctly captures the dependencies, even with a short (one decade) inertial range, and is superior to the traditional FSLE at large scales. Furthermore, the analytical solutions permit reconciling the CIST with the other measures, something which is generally not possible with the FSLE.