bluuebunny/crossref_metadata_2025 huggingface dataset:
Organic amendment addition distinctly influences phosphorus solubility in tropical volcanic soils with different mineralogical properties
Authors: Mendez Juan Carlos , Vargas Edgar
Published: March 2024

The abundance of short-range order (SRO) iron and aluminum minerals with high phosphorus (P) binding capacity makes this essential nutrient a major limiting factor for agriculture in tropical volcanic soils. These reactive minerals also possess a significant capacity to form organo-mineral associations, thereby contributing to stabilizing soil organic carbon. Adding organic amendments can enhance P use efficiency in volcanic soils due to the competitive effect of organic ligands with P for the adsorption on the surfaces of SRO minerals. Here, using two tropical volcanic soils from Costa Rica with low (LR) and high (HR) mineral reactivity, we assessed the effect of short-term incubations with compost at various rates (0%, 5%, and 20% m/m) on the solubility of different P fractions (measured as P-Olsen and P-CaCl2). Additionally, we determined P adsorption isotherms to evaluate changes in the adsorption behavior of this nutrient. Furthermore, in a bioassay using Sorghum bicolor as a model plant, we investigated the potential influence of compost addition on the agronomic efficiency of P fertilizers in these volcanic soils.The results of the incubation experiment showed that the addition of organic matter mostly affected the desorption of the P pool related to the capacity (Q) factor of soils (measured as P-Olsen), whereas the P intensity factor (I) (measured as P-CaCl2) remained mostly unchanged. The I factor was significantly increased only at the highest rate of compost addition in the LR soil. Description of the adsorption isotherms using the Langmuir equation revealed changes in the adsorption behavior of P due to the addition of compost. The maximum P adsorption capacity (Qmax) of the soils decreased as the amount of added organic amendment increased, particularly in the HR soil. The binding affinity of P (KL) to the mineral surfaces was also reduced due to the compost addition, and this effect was more pronounced in the HR soil. Lastly, higher agronomic efficiencies of P fertilizers were measured when compost was incubated in the HR soil, whereas in the LR soil the agronomic efficiencies of P fertilizers were unaffected by the compost addition. This study contributes to unraveling how the competitive interaction between organic ligands and P is modulated by the mineralogical properties of volcanic soils, particularly due to the reactivity of SRO minerals. Overall, our results indicate that the addition of organic amendments can be an effective alternative to improve P availability in soils with abundance of SRO minerals. From a broader perspective, adding organic amendments to soils with high P binding capacity would result in a “win-win” situation that contributes to improving the use efficiency of this limited resource while promoting the C storage in soils.
Data Assimilation Informed model Structure Improvement (DAISI) to improve prediction under climate change
Authors: Lerat Julien , Chiew Francis , Robertson David , Andreassian Vazken , Zheng Hongxing
Published: March 2024

Estimation of future streamflows is generally done using rainfall-runoff models to generate streamflow projections based on future climate inputs. Unfortunately, the performance of these models degrades significantly when predicting values outside of their calibration range, which undermines the credibility of projected scenarios. This abstract presents a method to analyze and improve the equations constituting a rainfall-runoff model structure in the context of climate change scenario modelling demonstrated with an application to the GR2M model and 201 catchments in South-East Australia. The method, termed "Data Assimilation Informed model Structure Improvement" (DAISI), enhances a rainfall-runoff model by combining data assimilation with polynomial updates of the state equations. The method is generic and modular, and consistently improves model performance across various metrics, including KGE, NSE on log-transformed flow, and flow duration curve bias. The updated model exhibits higher elasticity of runoff to rainfall, indicating potential significance for climate change simulations. The DAISI diagnostic identifies a reduced number of update configurations in the GR2M structure, with distinct regional patterns in three sub-regions (Western Victoria, central region, and Northern New South Wales). We suggest potential improvements for DAISI, such as incorporating additional observed variables like actual evapotranspiration to better constrain internal model fluxes.
Tracking shifts of mountain forest ecotones in aerial imagery with deep learning
Authors: Maroschek Michael , Seidl Rupert , Senf Cornelius , Rammer Werner
Published: March 2024

Forest ecosystems are sensitive to global change; especially at the ecotones we expect high sensitivity to changes in climate, disturbance regimes or land use. For instance, the treeline ecotone is expected to move upward in elevation with global warming. The advent of machine learning, specifically computer vision, provides powerful tools for monitoring ecotones across large spatial scales using remote sensing data. In this study, we focused on the spatiotemporal development of ecotones bracketing the subalpine forest belt (i.e., the upper boundary, formed by the treeline, and the ecotone to montane forests as the lower boundary) in a protected forest landscape in the European Alps. Our objectives were threefold: First, we aimed to identify trees and shrubs on historic and recent orthophotos using deep learning, with special attention to integrating multiple sensor types into one computer vision framework. Second, based on the computer vision inference, we sought to map the a) treeline and b) montane-subalpine ecotone. Third, we aimed to describe the spatiotemporal changes occurring in both ecotones.We based our analysis on historic and recent aerial images of Berchtesgaden National Park in the Northern Alps, covering roughly 210 km² in nine time steps from 1953 to 2020. The images were captured through both analog (panchromatic and color infrared) and digital (color infrared, RGB) sensors. To generate training data for deep learning, we manually interpreted randomly distributed 0.5 ha segments across all time steps, resulting in over 110,000 annotations of coniferous and broadleaved trees, shrubs, and standing dead trees. We tested different instance segmentation frameworks and selected the best performing model architecture to create wall-to-wall tree maps for each time step. Using structure and composition of the tree maps, we spatially delineated the ecotones and tracked their changes over time.We did not find a spatially consistent pattern of ecotones shifting upwards, however we were able to identify areas of change and stability linked to climate, topography, disturbances and land use. We observed remarkable local upward shifts in ecotones, particularly of the montane-subalpine ecotone, which shifted up to five times faster than the treeline. In general, we found that subalpine forests, situated between the two ecotones, decreased in area because of an upward shift of its lower boundary, and exhibited an increase in crown cover over time.Changes in these ecotones and related vegetation zones pose challenges to conservation, restoration and management. Our approach can help to address these challenges, e.g., in the combination with habitat modelling.
Resilience for Landslide Geohazards and Promoting Strategies in the Three Gorges Reservoir Area
Authors: Huang Yuanyue , Guo Haixiang , Yu Jing
Published: March 2024

Resilience is increasingly used as a concept for understanding natural disaster systems. Some countries have developed resilient city plans based on theoretical research and applied practice. Landslide is one of the most frequent geohazards in the Three Gorges Reservoir Area (TGRA). However, it is difficult to measure local disaster resilience, because of the special geographical location. Current approaches to disaster resilience evaluation are usually limited either by the qualitative method or properties of different disaster. Therefore, there is a great need to explore effective disaster resilience measurement methodologies. In this study, we developed an indicator system to evaluate landslides’ disaster resilience in the TGRE at the county level. It includes two properties of inherent geological stress and external social response, which are summarized into physical stress (Ps) and social forces (Sf). The evaluated disaster resilience can be simulated for promoting strategies with fuzzy cognitive map (FCM). The results show that: (1) The overall disaster resilience in the Three Gorges Reservoir Area was relatively low. (2) The resilience of the TGRA has spatial auto-correlation, that is, the areas with similar resilience are gathered in geographical location. (3) Proper policy guideline is essential to promote the disaster resilience. Policy promotes the system from all aspects in the TGRA.
Millennial-aged organic matter sequestration and preservation in anoxic and sulfidic mangrove soils: insights from isotopic and molecular analyses
Authors: Robin Sarah , Baudin François , Le Milbeau Claude , Marchand Cyril
Published: March 2024

A buried layer rich in organic matter (OM) has been identified in the mangrove soils along the West coast of New Caledonia (South Pacific), resulting from a long period of stable sea levels during the Holocene. This study aims to characterize this OM-enriched layer isotopically, molecularly (lignin and neutral carbohydrates), and using Rock-Eval pyrolysis, while identifying the decomposition and preservation processes in these anoxic and sulfidic conditions. The study site is a mangrove forest of the West coast of New Caledonia, with a vegetation typical of this semi-arid area. The species Rhizophora stylosa develops in monospecific stand seaward and the species Avicennia marina landward. Multiple parameters such as the high total organic carbon content (10%) indicate the presence of this enriched layer below 30 cm depth beneath the A. marina stand. Stable isotopic ratios indicate that the roots of R. stylosa are the primary source of OM in this layer. Degradation mechanisms include dehydrogenation and the loss of major neutral sugars (glucose, xylose, galactose), while preservation processes involving arabinose, vanillin, and p-hydroxyacetophenone contribute to the stabilization of OM. The presence of well-preserved root material associated with pyrite observed using a scanning electron microscope, along with high Sorg/C ratio provide tangible evidence of interactions between OM and minerals and OM sulfurization, reinforcing preservation in anoxic and sulfidic environments. Through radiocarbon dating, the OM-enriched layer is placed in the historical context of a period characterized by stable sea levels approximately 4,000 years ago, emphasizing the profound impact of prolonged stability on OM accumulation and preservation in mangrove soils.
Observations of deep near-inertial internal waves in the Eurasian Basin.
Authors: Bracamontes Ramírez Joel , Walter Maren
Published: March 2024

The Arctic Ocean has a less energetic internal wave climate than other oceans, mainly due to the thick sea ice cover which inhibits wind interaction with the surface. With the continued decrease in summer sea ice extent and the increase in seasonal ice-free areas, wind-driven internal waves, especially in the near-inertial range, are becoming more energetic. Coupled with the fact that most of the Arctic Ocean lies north of the critical latitude for semi-diurnal tides, the shift in ice dynamics implies an increase in the importance of near-inertial waves (NIW) for the internal wave climate. In particular, increased NIW amplitude and kinetic energy in the Canadian Basin and enhanced wind-driven vertical heat fluxes and dissipation rates in the Eurasian Basin have already been observed in the upper column. In the deep ocean beyond the critical latitude, NIWs are expected to drive mixing in the interior, but it is unclear to what extent. Here, we present innovative and unprecedented deep current observations from a mooring in the Gakkel Ridge in the Eurasian Basin at 82.53°N. The presence of barotropic diurnal and semi-diurnal tides and semi-diurnal harmonics enriches the complex interplay of internal waves. By comparing the observed downward and upward NIW kinetic energy with wind speed, sea ice properties and numerical simulations, we discuss the likely surface origin of the NIW. In particular, there is a lagged correlation of
Enlarging disparity of VPD between dry and wet lands due to divergent warming-induced atmospheric moistening
Authors: Jin Zheng , You Qinglong , Zuo Zhiyan , Wu Peili
Published: March 2024

    With warming of the atmosphere, the saturation limit for water vapor pressure is enhanced, thus more water vapor can stay in the atmosphere. However, the increase of water vapor pressure will not exactly equate to the increase of saturated water vapor pressure, thereby it will result in a change in vapor pressure deficit (VPD) of the atmosphere. Thus, how large is the increment of atmospheric water vapor and how the VPD changes could be interesting questions to be explored. Given that the VPD has significant influences on terrestrial ecosystems, here we choose to study the water vapor and VPD changes in the near-surface atmosphere over the non-desert lands. By generalizing the empirical Magnus expression of the Clausius-Clapeyron equation, we partitioned the VPD anomaly into contributions from warming and water vapor changes in the recent 42 years (1981-2022). Results showed the VPD gap between wet and dry regions is widened, and this widening gap is dominated by the uneven warming-induced atmospheric hydrating. 
Mechanisms of model bias impacting responses of the Atlantic cold tongue to greenhouse warming
Authors: Yang Yun , Cheng Xi , Wu Lixin , Cai Wenju , Chen Yuhu
Published: March 2024

The Atlantic cold tongue, typically peaking in boreal summer, exerts pronounced regional and global impacts on climate and socio-economy. Projected future changes in the Atlantic cold tongue feature great uncertainty, mainly arising from model bias in simulating its mean state, with less biased models projecting a stronger weakening in amplitude. However, the underlying mechanisms remain unknown. Here, we find model bias exerts its influence through modulating atmospheric thermal damping and upwelling of subsurface warming induced by the weakened Atlantic Meridional Overturning Circulation (AMOC). In less biased models, the Atlantic cold tongue, compared to the western equatorial Atlantic, featuring a cooler mean climate sea surface temperature (SST), is subjected to a smaller thermal damping induced by mean climate evaporation and consequently a faster SST warming. Moreover, an equatorial subsurface Atlantic warming associated with a reduced AMOC is advected to surface via mean climate upwelling, enhancing faster SST warming in the east, a feedback stronger in less biased models that produce greater climatological upwelling. The above asymmetric SST warming would be amplified by the Bjerknes feedback, leading to the weakened Atlantic cold tongue. These findings may help to predict the future change of Atlantic cold tongue and its influences.
Past climate conditions predict the influence ofnitrogen enrichment on the temperature sensitivityof soil respiration
Authors: Tian Peng
Published: March 2024

The response of soil carbon release to global warming is largely determined by the temperature sensitivity of soil respiration, yet how this relationship will be affected by increasing atmospheric nitrogen deposition is unclear. Here, we present a global synthesis of 686 observations from 168 field studies to investigate the relationship between nitrogen enrichment and the temperature sensitivity of soil respiration. We find that the temperature sensitivity of total and heterotrophic soil respiration increased with latitude. In addition, for total and autotrophic respiration, the temperature sensitivity responded more strongly to nitrogen enrichment with increasing latitude. Temperature and precipitation during the Last Glacial Maximum were better predictors of how the temperature sensitivity of soil respiration responds to nitrogen enrichment than contemporary climate variables. The tentative legacy effects of paleoclimate variables regulate the response through shaping soil organic carbon and nitrogen content. We suggest that careful consideration of past climate conditions is necessary when projecting soil carbon dynamics under future global change.
Functional diagnosis of industrial soils: from a cognitive model to in situ implementation
Authors: Dalquier Caroline , Séré Geoffroy , Hellal Jennifer , Legay Nicolas , Santoni Laure , Herbelin Pascaline
Published: March 2024

Industrial activities, such as thermal power plants, induce soil degradation on large areas (e.g. soil sealing, contamination related to fuel, coal and ash deposits, soil compaction). After the cessation of activities, landowners of such sites have a huge land heritage that could be considered to promote rehabilitation projects for new land-uses in the frame of the No Net Land Take by 2050. Therefore, there is a need to develop a robust and easy-to-use approach for landowners that could be implemented by soil techniciens/pratitioners to assess soil functions to measure their potential for future uses.First a cognitive model linking soil functions to a minimum dataset of indicators was established based on chemical, physical and biological properties of soil as well as vegetation cover. This cognitive model includes 6 soil functions (e.g. plant biomass production) and 17 sub-functions (e.g. phytoavailability of nutrients, nutrients storage) and a minimum set of indicators selected among a large list from research studies and attributed to each sub-function and function.Then two thermal power plants under closure were selected and a documentary survey was carried out for each site to identify contrasted zones in terms of soil cover, mostly based on the nature of the past activities (e.g. coal, slag or ash deposit, building foundations, fuel storage). Twelve zones considered as homogeneous in terms of vegetation and soil type and distinct from each other were selected on these two sites. In total, 12 soil profiles and 164 soil samples were analysed for various biological (plants, nematodes, microbial communities), chemical and physical parameters.Our results show contrasting situations. Despite the high vegetation cover of the three different ash deposit zones, their plant diversity indices ranged from very low to medium. The same goes for the area where building foundations were located, but they had very little vegetation cover. Also, the enrichment index (EI) and structure index (SI) of the nematode community showed that ash deposits are degraded, nutrient-poor soils and have a high C/N (>12) while the building foundation areas have a "mature and fertile" soil with optimal C/N.  Whereas some soils could be considered as natural references as they were not affected by industrial activities, others were Technosols made of 100% artefacts. However, the gradient of anthropisation was surprisingly not correlated to the level of functions that were assessed. As an example, technogenic soils developed from fly ash exhibit high soil functions ratings (e.g. carbon storage).These initial results suggest that the functioning of these soils must be evaluated according to different scales (e.g. plot scale, surface soils), points of view (biological, chemical and physical) and soil functions (e.g. storage and sequestration of GHG, biodiversity reservoir), to establish their functional profiles and suggest possible future uses.
Three tubular fossil assemblages from the terminal Ediacaran Dengying Formation in southern Shaanxi Province of South China
Authors: Chen Wei , Cai Yaoping , Wang Xiaoyang
Published: March 2024

Terminal Ediacaran fossils (ca. 550–539 Ma) contain potentially the earliest known animals. Tubular fossils represent a characteristic fraction of terminal Ediacaran fossil forms and they may have served as evolutionary ancestors of the subsequent diversification of tubular taxa in the early Cambrian. However, the paleogeographic range of previously reported terminal Ediacaran tubular taxa and those undescribed tubular forms locked in the fossil record, remains poorly documented. Our presentation illustrates three fossil assemblages from the Ediacaran Denying Formation at the Shengchangba section in southern Shaanxi Province, South China. The stratigraphically lower assemblage consists primarily of pyritized tubular fossils Conotubus and Gaojiashania in siltstone–mudstone beds, the middle assemblage is composed of calcified Cloudina and at least four tubular forms in massive limestone beds, whereas the higher assemblage is made up of silicified Cloudina, Sinotubulites, and several new tubular forms in thick-bedded dolomite. In addition to Cloudina, Sinotubulites, Conotubus, and Gaojiashania, several variety tubular forms—including densely and irregularly annulated conical tube and straight tube, unevenly undulated tube, irregularly ribbed conical tube, cylindrical tube with regularly spaced transverse ridges and single-walled conical tube with smooth outer wall—are identified in the Dengying Formation. The new occurrences of previously reported taxa broad geographic range of Cloudina, Sinotubulites, Conotubus, and Gaojiashania. Although the taxonomic affinities and phylogenetic relationships of these fossils remain problematic due to the absent and/or poor preservation of anatomical details, the several varieties unamend tubular forms add to the diversity of terminal Ediacaran tubular fossil biotas. The co-occurrence of Cloudina hartmannae with diverse tubular fossil forms plays an important role in facilitating global biostratigraphic correlation. Pyritization in the siltstone–mudstone facies, calcification in the limestone facies and silicification in the dolomite facies, responsible for the exceptional preservation of the three tubular fossil assemblages, provide revelatory clues in recovering new fossil localities.
Automated Static Magnetic Cleanliness Screening for the TRACERS Small-Satellite Mission
Authors: Dorman Cole J , Piker Chris , Miles David M
Published: March 2024

The Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) Small Explorers mission requires high-fidelity magnetic field measurements for its magnetic reconnection science objectives and for its technology demonstration payload MAGnetometers for Innovation and Capability (MAGIC). TRACERS needs to minimize the local magnetic noise through a magnetic cleanliness program such that the stray fields from the spacecraft and its instruments do not distort the local geophysical magnetic field of interest. Here we present an automated magnetic screening apparatus and procedure to enable technicians to routinely and efficiently measure the magnetic dipole moments of potential flight parts to determine whether they are suitable for spaceflight. This procedure is simple, replicable, and accurate down to a dipole moment of 1.59 × 10-3 N m T-1. It will be used to screen parts for the MAGIC instrument and other subsystems of the TRACERS satellite mission to help ensure magnetically clean measurements on-orbit.
Exploring the evolution of lava planets using planet-resolving models
Authors: Nicholls Harrison , Lichtenberg Tim , Pierrehumbert Raymond
Published: March 2024

It is thought that most terrestrial planets pass through a magma ocean stage at some point in their lifetimes. This could originate from accretional energy or a giant impact, and potentially be maintained by stellar/tidal heating or a greenhouse effect. Understanding the major processes that cotemporally shape lava planet evolution is key to relating their historical conditions to currently observable states. For example, by explaining how a terrestrial planet entirely loses its atmosphere despite supplicant outgassing of volatiles from the interior.To this end, we have developed a 1D numerical code which resolves a model lava planet from its core to space. This allows feedbacks between the atmosphere and interior to be captured, as well as the processes that occur within each component of the planet (e.g. convection, radiative transfer). Subject to parameters such as the initial volatile endowment, the model planet can then be evolved over time from an entirely molten state with primordial atmosphere to a fully-solidified state with a secondary atmosphere; in some cases it may not solidify at all. Using a 1D approach allows disequilibrium processes (e.g. photochemistry) to shape planetary evolution and atmospheric composition, which will be reflected in observations made by the James Webb Space Telescope. Another advantage of a generalised planet-resolving model is that it can be applied to a wide range of cases with rocky components: Earth, Venus, the terrestrial TRAPPIST-1 planets (which may or may not currently have atmospheres), as well as sub-Neptunes and super-Earths.Our preliminary results indicate that steady-state atmospheric composition is heavily dependent on interior conditions (e.g. oxygen fugacity, nitrogen concentration), in contrast to the canonical assumption of steam-dominated atmospheres. Our chemical kinetics module indicates that these atmospheres are typically inhomogeneous, with melt-vapour equilibrium at the surface not being representative of the upper-atmosphere composition. Using the radiative-convective module of our model, we also verify recent literature which has indicated that such thick and hot atmospheres may feature a radiative layer at the surface.
Craton Formation by Underplating and Development of the MLD: Evidence from Bayesian Surface Wave Inversion 
Authors: Boyce Alistair , Bodin Thomas , Durand Stephanie , Soergel Dorian , Debayle Eric
Published: March 2024

Craton formation and evolution remains enigmatic because observations from long and short period seismic waves and geochemical data are inconsistent. For example, both internal layering and radial anisotropy are poorly constrained. By inverting cratonic Rayleigh and Love surface wave dispersion curves for shear-wave velocity and radial anisotropy using a flexible Bayesian scheme, we show that these inconsistencies can be reconciled. Our methodology does not require any vertical smoothing and only includes anisotropic layers where necessary to fit the data. Results show all cratons possess a positively radially anisotropic upper lithospheric layer that is best explained by Archean underplating. An isotropic layer lies beneath, likely indicative of two-stage craton formation. We find a variable amplitude low velocity zone (LVZ) may exist within the upper anisotropic layer of up to 9 of 12 cratons studied. This LVZ is well correlated to observed Mid-Lithospheric Discontinuities (MLDs). Our results suggest the MLD is best explained by post formation modification within cratons.
Plant establishment and plant-sand feedbacks as fundaments for dune-for-dike nature-based solutions
Authors: Taelman Charlotte , Dhondt Maaike , Batsleer Femke , Provoost Sam , Van Uytvanck Jan , Bonte Dries
Published: March 2024

Coastal foredunes serve as a natural defense against rising sea levels and storm floods, support important Natura2000 biodiversity and habitats, and offer areas for human recreational activities. Along urbanized coasts, a large proportion of dune systems have been replaced with hard infrastructures such as dikes and sea walls. Over the past decade, the limitations of these traditional grey infrastructures (their static character and high maintenance costs) were recognized. This caused scientists across many disciplines to explore coastal dunes as nature-based solutions for sustainable and cost-effective long-term coastal protection.Coastal dunes develop from ecological interactions between sand fluxes and vegetation development. Plant-sand feedbacks are the basis for the unique dynamic and self-organizing properties of coastal dunes. These properties are anticipated to make them resilient and responsive to tidal and wave conditions, and hence future climate change impacts. The construction of hybrid dune-dike systems, where dunes are built in front of the dike, emerges as a promising solution to secure coastal regions against floods and storms.To allow the design, the creation but also the natural development of such dune-dike hybrid nature-based solutions in the most optimal way, we have to understand the responses of plants to changes in environmental conditions, as well as their effects on the environment.First, to be able to predict where natural dune development is possible, I constructed an ecological niche model for embryo dune plants on the Belgian coast. These embryo dune plants are the pioneer plants responsible for the natural initiation of dune development on the high beach. They consist of (rare) annual species that lay the foundation for further dune development and are subject to both human and environmental stressors. I built a spatio-temporal regression model, based on annual sand dynamics and flooding potential, to deduce and demonstrate that the establishment of embryo dunes is feasible along the entire Belgian coast, but is mainly constrained by mechanical beach cleaning and beach management.Second, to be able to optimize the construction of dune-for-dikes through planting strategies of marram grass, I analyzed how the abundance and spatial configuration of marram grass impact the development of established pilot dune-dike hybrids along the Belgian coast. This mechanistic insight on sand burial-plant growth interactions allows for a better prediction of the outcome of different marram grass planting strategies, and the corresponding dune shape and characteristics related to storms and erosion.In conclusion, my research emphasizes the importance of understanding the ecological dynamics of coastal dunes as essential components to gain a dynamic rather than static understanding of dune-dike hybrid nature-based solutions for effective coastal and biodiversity protection.
Accretion of the lowermost oceanic crust at fast-spreading ridges: Insights from the East Pacific Rise (Hess Deep, IODP Leg 345)
Authors: Basch Valentin , Sanfilippo Alessio , Snow Jonathan , Loocke Matthew , Zanetti Alberto
Published: March 2024

At mid-ocean ridges, melts formed during adiabatic melting of a heterogeneous mantle migrate upwards and ultimately crystallize the oceanic crust. In this context, the lower crustal gabbros represent the first crystallization products of these melts and the processes involved in the accretion of the lowermost crust drive the chemical evolution of the magmas forming two thirds of Earth’s surface. At fast-spreading ridges, elevated melt supply leads to the formation of a ⁓6 km-thick layered oceanic crust. Here, we provide a detailed petrochemical characterization of the lowermost portion of the fast-spread oceanic crust drilled during IODP Leg 345 at the East Pacific Rise (IODP Site U1415), together with the processes involved in crustal accretion. The recovered gabbroic rocks are primitive in composition and range from olivine-rich troctolites to troctolites, olivine gabbros, olivine gabbronorites and gabbros. Although textural evidence of dissolution-precipitation processes is widespread within this gabbroic section, only the most interstitial phases record chemical compositions driven by melt-mush interaction processes during closure of the magmatic system. Yet, the occurrence of primitive orthopyroxene in most of the olivine-bearing samples indicates that reactive processes allowed for its local saturation within the percolating MORB-type melt. Comparing mineral compositions from this lower crustal section with its slow-spreading counterparts, we propose that the impact of reactive processes on the chemical evolution of the parental melts is dampened in the lowermost gabbros from magmatically productive spreading centres. Oceanic accretion thereby seems driven by in situ crystallization in the lowermost gabbroic layers, followed by upward reactive percolation of melts towards shallower sections. In addition, we here furnish a first estimate of the trace element composition of the parental melts that led to the accretion of the lower crust at Hess Deep, Atlantis Massif and Atlantis Bank; we show that the primary melts of the East Pacific Rise are more depleted in incompatible trace elements compared to those formed at slower spreading rates, as a result of higher melting degrees of the underlying mantle.
Chemical Characterization of Atmospheric Bioaerosols
Authors: Bahdanovich Palina , Axelrod Kevin , Khlystov Andrey , Samburova Vera
Published: March 2024

Bioaerosols, or aerosol particles of biological origin, have been found to represent a significant mass fraction of atmospheric particulate matter (PM) and organic carbon (OC). These particles are larger in size (up to 100 µm) than most anthropogenic aerosols but are lighter and thus can be transported over long distances, affecting atmospheric processes and cloud physics (i.e., act as cloud condensation nuclei). Moreover, climate change is expected to increase pollen number concentrations (~21%) as well as pollen season length (+21 days) across North America. So far, only a few studies have been conducted on the chemical composition of bioaerosols and their behavior under atmospheric conditions. The goal of this research was to characterize the chemical composition of bioaerosols using multiple analytical techniques, such as Proton Nuclear Magnetic Resonance Spectroscopy (1H-NMR), Gas Chromatography-Mass Spectrometry (GC-MS), and Ultra-High Performance Liquid Chromatography-Mass Spectrometry (UPLC-MS), thereby advancing atmospheric aerosol chemistry. Various common bioaerosols, including pollen, algae, fungi, and bacteria, are analyzed, and characterized under controlled laboratory conditions. All samples are analyzed for their chemical composition: saccharides with GC-MS, amino acids and fatty acids with UPLC-MS, and functional groups with 1H-NMR spectroscopy. The present research is one of the first studies of detailed chemical characterization of bioaerosols with the 1H-NMR technique, where the 1H-NMR results are also compared with GC- and UPLC-MS quantitative analyses of individual bioaerosol species.
Modelling the Impact of Ammonia Emissions on New Particle Formation in the Asian Monsoon Upper Troposphere
Authors: Xenofontos Christos , Kohl Matthias , Pozzer Andrea , Lelieveld Jos , Christoudias Theodoros
Published: March 2024

Ammonia emissions in south-east Asia are a significant contributor to air pollution. This pollution, through convective transport by the Asian monsoon anticyclone, can initiate new particle formation events in the upper troposphere and the development of the Asian Tropopause Aerosol Layer (ATAL). Despite the acknowledged influence of ammonia emissions and particulate ammonium on upper tropospheric air pollution and cloud formation, a comprehensive understanding of the ATAL remains limited. A substantial knowledge gap persists regarding its origin, maintenance, chemical composition, and the climatic implications of these factors. We use the EMAC chemistry-climate model to study the influence of ammonia emissions on nucleation mechanisms contributing to the development of the ATAL. Through the integration of observational data with model simulations and the application of parameterisations from the CERN CLOUD experiment, we investigate the conditions sustaining the ATAL and explore its climatic implications. The findings suggest that ammonia emissions enhance nucleation rates in the ATAL, resulting in up to 70% increases in cloud condensation nuclei (CCN) concentrations. A diurnal cycle analysis reveals that these new particle formation mechanisms mostly occur during daylight after convection events uplifting precursor gases. Our findings enhance the understanding of the impact of anthropogenic emissions on CCN formation processes and their implications for climate in the regions characterised by high ammonia emissions.
Interactions of warm cloud, precipitation, and local forcings over the Great Barrier Reef: Insights from convection-permitting simulations
Authors: Zhao Wenhui , Huang Yi , Siems Steven , Manton Michael , Harrison Daniel
Published: March 2024

The important role of warm clouds in regulating the regional energy balance and ocean temperature, that are directly linked to the thermal coral bleaching events, has been increasingly recognised over the Great Barrier Reef (GBR). These shallow clouds, however, are by their nature sensitive to perturbations in both their thermodynamic environment and microphysical background. In this study, we employ the Weather Research and Forecasting (WRF) model with a convection-permitting configuration at 1 km resolution to examine the interactions between the warm clouds and different local forcings over the GBR. A range of local forcings including local aerosol loading, coastal topography, and sea surface temperature (SST) is examined.Our simulations show a strong response of cloud microphysical properties, including cloud droplet number concentration (CDNC), liquid water path (LWP), and precipitation to the changes in atmospheric aerosol population over the GBR. Higher CDNC and LWP correlated to increased aerosol number concentration leads to a rise in shortwave cloud radiative effect, though the magnitude is small, over both the mountains and upwind over the GBR. While cloud fraction shows little responses, a slight deepening of the simulated clouds is evident over the upwind region in correspondence to the increased aerosol number concentration. A downwind effect of aerosol loading on simulated cloud and precipitation properties is further noted. In consideration of the coastal topography, cloud fraction and accumulated precipitation are strongly sensitive to orographic forcing over the GBR. Orographic lifting and low-level convergence are found to be crucial in explaining the cloud and precipitation features over the coastal mountains downwind of the GBR. However, clouds over the upwind ocean are more strongly constrained by the trade wind inversion, whose properties are, in part, regulated by the coastal topography. Finally, on the scales considered in our study, the warm cloud fraction and the ensuant precipitation over the GBR show only a small response to the local SST forcing, with this response being tied to the simulated cloud type.
Sensitivity of Observationally Based Estimates of Ocean Heat Content and Thermal Expansion to Vertical Interpolation Schemes
Authors: Li Yuehua , Church John , McDougall Trevor , Barker Paul
Published: March 2024

Changes in ocean heat content are a critical element of climate change, with the oceans containing about 90% of the excess heat stored in the climate system and 60% in the upper 700 db. Estimates of these changes are sensitive to horizontal mapping of the sparse historical data and errors in eXpendable BathyThermograph data. Here we show that they are also sensitive to the vertical interpolation of sparsely sampled data through the water column. We estimate, using carefully constructed vertical interpolation methods with high-quality hydrographic (bottle and CTD) data, the observationally based upper ocean heat content increase (thermosteric sea level rise) from 1956 to 2020 is 285 Zeta Joules (0.55 mm yr −1), 14% (14%) larger than estimates relying on simple but biased linear interpolation schemes. The underestimates have a clear spatial pattern with their maximum near 15°N and 12°S, around the maxima in the curvature of the temperature-depth profile.
Drought duration and spatial dependence increase during propagation
Authors: Brunner Manuela Irene , Chartier-Rescan Corentin
Published: March 2024

As droughts propagate both in time and space, their impacts increase because of changes in drought properties. Even though drought propagation has two dimensions – a temporal and spatial one – these are mostly studied separately, which neglects that the propagation of droughts through the hydrological cycle may extend from local to spatial characteristics. Therefore, it is yet unknown how the spatial extent and connectedness of droughts change as droughts propagate from the atmosphere to and through the hydrosphere. In this study, we assess not only how local meteorological droughts propagate through the hydrological cycle to streamflow and groundwater but also how drought spatial extent and connectedness change with drought propagation. To do so, we use a large-sample dataset of 70 catchments in the Central Alps for which both observed streamflow and groundwater data are available. We show that drought propagation from the atmosphere to the hydrosphere affects both local and spatial drought characteristics and leads to longer, delayed, and fewer droughts with larger spatial extents. 75% of the precipitation droughts propagate to P-ET or further, 20% to streamflow, and only 10% to groundwater. Of the streamflow droughts, 40% propagate to groundwater but 60% do not propagate.  Drought extent and connectedness increase during drought propagation from precipitation to streamflow thanks to synchronizing effects of the land-surface such as widespread soil moisture deficits but decrease again for groundwater because of sub-surface heterogeneity. These findings have implications for drought prediction and management. They suggest a partial predictability of streamflow and groundwater droughts by atmospheric and hydrological deficits and that large scale streamflow deficits may be partly compensated by groundwater, which shows less frequent and spatially extensive droughts than streamflow.
Multi-disciplinary monitoring system for resilient management of coastal areas: the REMACO project
Authors: Randazzo Giovanni , Francesco Castelli , Franco Cavallaro , Luca Cavallaro , Sebastiano D'Amico , Valentina Lentini , Agostino Tomasello , Zammit Anthony , Lanza Stefania
Published: March 2024

The southern coast of Sicily and the islands of the archipelagos of Malta are highly exposed to risks coming from the sea. Such coasts are subjected to fast erosion due to natural and anthropic causes which involve the failure of cliffs, the triggering of localized erosion and the possibility of flooding. The REMACO project is financed by the INTERREG Italia-Malta program and it aims at creating an integrated multidisciplinary monitoring system for coastal areas. In particular, it makes use of the models for the evaluation of flooding and coastal erosion due to the storms as well as the development and implementation of monitoring of sea waves (punctual and aerial) through the use of coastal monitoring networks. In addition, it capitalizes also from the geomorphological, sedimentological, and orthophotographic monitoring of over 130 Pocket Beaches (PBs), located in Sicily and Malta.The project activities focus on cliff and PBs. The latter are small beaches limited by natural headlands, strongly jutting into the sea, free from direct sedimentary contributions that are not eroded from back-shore cliffs. Along the Maltese and Sicilian coasts are several PB, which depending on their isolation and level of exposure, preserve ecological niches of great value (Posidonia oceanica), and thus represent relic deposits, formed under different conditions from those currently experienced, suggesting a response naturally resilient to the effects of climatic changes. These beaches are prized by tourists but often suffer the impact of human pressure and trigger risks to the safety of the same users. It is proposed to map all the PB to create a remotely sensed monitoring platform, based on the identification of specific geomorphological and sedimentological indices and the evolution of beach-incident wave motion, in order to preserve this erosion-sensitive environmental niche and ensure continued tourist use. Ultimately, the REMACO project enhances the monitoring of both sandy and rocky coastlines to obtain useful information for possible alerts and to obtain data for management models. The data acquired, in the medium to long term, will allow different stakeholders who are responsible for the resilient management of the coasts, to adapt in the context of mitigating the effects of climate change and to also safeguard human life.
From turbidites to evaporites: the Messinian Salinity crisis record of the Tabernas Basin (SE Spain)
Authors: Lacerda Orita Gustavo Kenji , Pérez-Valera Fernando , Soria Jesús , Gomez-Rivas Enrique , Corbi Hugo , Sierra Ramirez Núria , Liu Jingjing , Gibert Luis
Published: March 2024

The Messinian Salinity crisis (MSC) was a major ecological crisis triggered by a combination of climatic and tectonic drivers that led to the progressive restriction of the Mediterranean, and culminated with the formation of large evaporite deposits. The Tabernas Basin (SE Spain) presents an exceptional Miocene sedimentary record, key for understanding the evolution of a turbiditic basin during the MSC. A composite stratigraphic section (>200m long) from the early Messinian to the early Pliocene shows different phases of the MSC in the Yesón Alto area (~20 km from Almeria City). Our study allows recognizing pre-evaporitic, syn-evaporitic, and post-evaporitic units. Two stratigraphic sections, one in the Yeson Alto and the other in Rambla de Lanujar were measured, sampled and documented for their petrological, geochemical and sedimentary facies characterization. Paleontological data, obtained through the analysis of foraminifera and marine macrofossils, enabled bio-stratigraphic dating. Magnetostratigraphic sampling along the pre- and post-evaporitic units was executed, although only the post-evaporitic deposits allowed the isolation of the primary Characteristic Remanent Magnetization. The preliminary results indicate that sedimentation rates during the pre-evaporitic phase were approximately four times greater than those of the correlated Abad member in the neighbouring Sorbas Basin The examined pre-evaporitic unit (90 m-thick) predominantly comprises fine-grained deposits intercalated with levels of sandstones and limestones. Abundant benthic and planktonic foraminifera, together with other marine fauna, facilitated the identification of 13 bioevents in the succession. The presence of Turborotalita quinqueloba and Orbulina taxa allows correlation with the last Messinian biozone (d) of Mediterranean biostratigraphy. Decimeter-thick beds of fossiliferous packstones/wackestones and barren mixed-siliciclastic carbonates occur toward the uppermost part of the unit, at the transition with the evaporites, indicating the initiation of evaporitic conditions preceding the deposition of the first gypsum bed. Soft-sediment deformation in these transitional beds suggests the occurrence of an important seismic event in Tabernas basins during initial stage of the MSC. The evaporitic unit in this area comprises only three cycles of massive selenitic gypsum beds intercalated with mudstones, in contrast with the Sorbas Basin, where up to 15 cycles have been described. δS analysis of these selenites reveals values expected for Miocene marine evaporites. A level with abundant marine fossils in the second inter-evaporitic level indicates at least an episode of dilution from >150gr/l to