bluuebunny/crossref_metadata_2025 huggingface dataset:
Ejection of marine microplastics by raindrops: a computational and experimental study
Authors: Lehmann Moritz , Oehlschlägel Lisa Marie , Häusl Fabian , Held Andreas , Gekle Stephan
Published: March 2022

Raindrops impacting water surfaces such as lakes or oceans produce myriads of tiny droplets which are ejected into the atmosphere at very high speeds. Here we combine computer simulations and experimental measurements to investigate whether these droplets can serve as transport vehicles for the transition of microplastic particles with diameters of a few tens of μm from ocean water to the atmosphere. Using the Volume-of-Fluid lattice Boltzmann method, extended by the immersed-boundary method, we performed more than 1600 raindrop impact simulations and provide a detailed statistical analysis on the ejected droplets. Using typical sizes and velocities of real-world raindrops – parameter ranges that are very challenging for 3D simulations – we simulate straight impacts with various raindrop diameters as well as oblique impacts. We find that a 4 mm diameter raindrop impact on average ejects more than 167 droplets. We show that these droplets indeed contain microplastic concentrations similar to the ocean water within a few millimeters below the surface. To further assess the plausibility of our simulation results, we conduct a series of laboratory experiments, where we find that microplastic particles are indeed contained in the spray. Based on our results and known data – assuming an average microplastic particle concentration of 2.9 particles per liter at the ocean surface – we estimate that, during rainfall, about 4800 microplastic particles transition into the atmosphere per square kilometer per hour for a typical rain rate of 10 mm/h and vertical updraft velocity of 0.5 m/s.
A Campaign of Scientific Drilling for Monsoon Exploration in the Asian Marginal Seas
Authors: Clift Peter , Betzler Christian , Clemens Steven , Christensen Beth , Eberli Gregor , France-Lanord Christian , Gallagher Stephen , Holbourn Ann , Kuhnt Wolfgang , Murray Richard , Rosenthal Yair , Tada Ryuji , Wan Shiming
Published: March 2022

International Ocean Discovery Program (IODP) conducted a series of expeditions between 2014 and 2016 that were designed to address the development of monsoon climate systems in Asia and Australia. Significant progress was made in recovering Neogene sections spanning the region from the Arabian Sea to the Japan Sea and south to western Australia. High recovery by advanced piston core (APC) technology has provided a host of semi-continuous sections that have been used to examine monsoonal evolution. Use of half APC was successful in sampling sand-rich sediment in Indian Ocean submarine fans. The records show that humidity and seasonality developed diachronously across the region, although most regions show drying since the middle Miocene and especially since ~4 Ma, likely linked to global cooling. The transition from C3 to C4 vegetation often accompanied the drying, but may be more linked to global cooling. Western Australia, and possibly southern China diverge from the general trend in becoming wetter during the late Miocene, with the Australian monsoon being more affected by the Indonesian Throughflow, while the Asian Monsoon is tied more to the rising Himalaya in South Asia and to the Tibetan Plateau in East Asia. The monsoon shows sensitivity to orbital forcing, with many regions having a weaker summer monsoon during times of Northern Hemispheric Glaciation. Stronger monsoons are associated with faster continental erosion, but not weathering intensity, which either shows no trend or decreasing strength since the middle Miocene in Asia. Marine productivity proxies and terrestrial environmental proxies are often seen to diverge. Future work on the almost unknown Paleogene is highlighted, as well as the potential of carbonate platforms as archives of paleoceanographic conditions.
Toward a Local Climate Zone-based drag and mixing length parametrization for the urban environment
Authors: Nagel Tim , Schoetter Robert , Bourgin Victor , Masson Valéry , Onofri Emma
Published: March 2022

To prepare future urban climate modelling and numerical weather prediction at the hectometer scale in cities with heterogeneous morphology and high-rise buildings, urban climate models have to be coupled at multiple levels with atmospheric models. Vertical profiles of the building drag coefficient and the urban mixing length need to be specified to parametrize the effect of the buildings on the flow. Building-resolving micro-scale simulations can be employed to derive these quantities.

In the present contribution, micro-scale large-eddy simulations of eleven Local Climate Zone (LCZ) based urban morphologies with various building plan and frontal density are used to provide velocity, sectional drag coefficient and mixing length reference vertical profiles for the urban environment. The micro-scale simulations, which are of 1-m resolution in both horizontal and vertical directions, are performed with the MesoNH meteorological research model. This model represents explicitly the obstacles with the Immersed Boundary Method and accounts for the impact of the large-scale turbulence structures on the urban canopy thanks to dynamical downscaling and embedded numerical domains using the grid nesting method. The micro-scale results show that, contrary to traditional assumptions, the velocity profile is generally not exponential and the mixing length is not constant in the urban canopy. This is in agreement with more recent research. The results also show that the building frontal density seems to be a key parameter for the shape of the velocity profile, within and directly above the urban canopy.

The sectional drag and mixing length profiles are then used to propose a new LCZ-based parametrization for the wind dynamics in the urban environment when using the Meso-NH model at the hectometer scale. The results show that the proposed parametrization is more efficient than the current one, consisting in a constant drag coefficient and no specific modification of the turbulent mixing length scale in the urban environment. These results open new perspectives to better parametrize the dynamic effects of real urban areas at the hectometer scale.
Interpretation and Reconstruction of Depositional Environment and Petroleum Source Rock Using Outcrop Gamma-ray Log Spectrometry From the Huai Hin Lat Formation, Thailand
Authors: Phujareanchaiwon Chawisa , Chenrai Piyaphong , Laitrakull Kasira
Published: March 2022

Gamma ray logs are most useful in identifying subsurface lithology and interpreting depositional environments. This study highlights the use of outcrop gamma-ray logs along with outcrop observations and total organic carbon (TOC) analysis to provide the stratigraphic framework of the organic-rich rocks of Huai Hin Lat Formation in central Thailand. The study reveals five sedimentary facies including (1) structureless sandstone, (2) structured sandstone, (3) interbedded sandstone and siltstone, (4) interbedded mudstone and siltstone and (5) calcareous mudstone. These facies can be grouped into two facies associations; mudstone-dominated and sandstone-dominated facies associations. The depositional environment was interpreted as lacustrine basin- fill subdivided into deep lacustrine environment and sublacustrine fan associated with the turbidity currents. The total gamma-log characteristics are closely related to the lithologies controlled primarily by clay mineral compositions. Whist, the use of spectral gamma-ray can reveal more details on depositional environments and conditions. In this study, uranium (U) concentrations is proven to be useful in highlighting organic-rich rocks in low potassium (K) and thorium (Th) concentration successions due to its ability to be fixed in clay minerals and organic materials under an anoxic condition. Thus, the U spectral gamma ray is suggested to combine with conventional gamma ray log for depositional environment and recognition of organic-rich rocks.
How much can we simplify irrigation in an integrated modelling purpose? A case study in southern France
Authors: Soutif--Bellenger Myriam , Thirel Guillaume , Therond Olivier , Villerd Jean
Published: March 2022

The estimation of irrigation amounts and timings is crucial for the design of water management strategies at the regional scale. However, simplified modelling approaches are often preferred even though very complex and high-accuracy crop models or agent-based models exist. In this study, we develop a sensitivity analysis to evaluate the impacts of simplifications and hypotheses in irrigation modelling. For this, different simple modelling approaches based on the CropWat model were compared to a multi-agent based approach (Maelia), which served as a benchmark. To make an in-depth comparison between simulations, several indicators characterizing daily simulated irrigation were calculated and a decomposition of variance was carried out to measure impacts of diverse factors on irrigation. Applied over a downstream portion of the Aveyron River (southern France), the sensitivity analysis shows a high variability between simulations in function of modelling assumptions. It also shows that several simplifying approaches were able to reproduce the high-accuracy model estimation of irrigation. Decisive variation factors we identified are rules of triggering and quantification of daily irrigation, irrigation period definition and evapotranspiration estimation. Recommendations to take into account highlighted variability linked to farmers’ irrigation practices are introduced in this work, consisting in a combining a set of irrigation models. In function of advancement, a complete integrated agro-hydrologic modelling chain might be presented.
The impact of marine biogeochemistry on physics and its consequences for the modelling of North-West European shelf seas
Authors: Skakala Jozef , Bruggeman Jorn , Ford David , Ciavatta Stefano
Published: March 2022

We introduced feedback from the simulated biogeochemistry to physics in the framework of the CMEMS operational physical-biogeochemical model of the North-West European Shelf. Using this development we demonstrate that light attenuation by the biogeochemical tracers has a significant impact on ocean heating in the upper 200m of the water column. We also show that the simulated temperature is sensitive to the modelling scheme representing the underwater light attenuation, i.e in how it resolves spectra, direction and the optically active tracers. We will discuss in detail the impact of these developments on the research version of the CMEMS operational model that includes assimilation of temperature, salinity and chlorophyll.
Contribution of climate variability, land-use and Southern Ocean dynamics to changes in atmospheric CO2 concentration over the past two millennia
Authors: Goosse Hugues , Barriat Pierre-Yves , Brovkin Victor , Klein François , Meissner Katrin , Menviel Laurie , Mouchet Anne
Published: March 2022

By performing an ensemble of sensitivity experiments with the LOVECLIM model, we confirm the earlier results showing that temperature changes had a large influence on the land carbon cycle over the preindustrial Common Era. However, this process alone cannot explain the magnitude of the reconstructed atmospheric CO2 and δ13CO2 variations. In particular, even when the model is constrained to follow reconstructed temperature changes by data assimilation, and when applying relatively large values of the climate-carbon feedback parameter, it can only explain about 50% of the atmospheric CO2 decrease between the 12th and the 17th century. We find that land use changes are likely responsible for most of the observed long term atmospheric CO2 trend over the first millennium of the Common Era, and for up to 30 % of the decrease observed after 1600 CE. In addition, in our experiments, changes in southern hemisphere westerly winds induce slightly smaller changes in atmospheric CO2 concentrations than those associated with land use change, and variations in δ13CO2 of the same order of magnitude as the observed ones. Those wind changes also have a strong impact on the difference in 14C between the northern and southern hemisphere, presenting strong similarities with observed changes. Combining the effects of changes in temperature, land use and winds over the Southern Ocean provides a reasonable agreement with reconstructions for atmospheric CO2 concentrations and δ13CO2, especially for the low CO2 values observed during the 17th century. This underlines the important contribution of both land and ocean carbon processes. Nevertheless, some uncertainties remain on the origin of the relatively high CO2 concentrations reconstructed during the 11th and 16th centuries.
The YAM seep area – an active carbonate-paved gas seep field at the accretionary margin SW offshore Taiwan 
Authors: Tseng Yiting , Römer Miriam , Pape Thomas , Chen Tzu-Ting , Lin Saulwood , Berndt Christian , Bohrmann Gerhard
Published: March 2022

The YAM seep area is an active gas seep region among the widespread seep sites offshore south-western Taiwan. The seep area covers a seafloor region of 49,000 m2 at the northern crest of Four-Way Closure Ridge in 1,347 m water depth. During several research cruises (ORI-1163, SO266), shipborne and AUV-related hydro-acoustic investigations revealed that the area of seepage is well documented by high backscatter and a changing micro-bathymetry between rough and flat in the otherwise very flat seabed in the area. 
During expedition SO266, RV Sonne, gas emission sites were observed at the center and eastern flank of the area using ship-borne multi-beam data in the water column. Seawater methane concentrations above the seafloor were collected from the middle west to east of the central transect, revealing concentrations ranging 5.5-18.2 nmol/L with general higher methane concentrations at the rim of the area. Authigenic carbonate samples were collected during gravity coring and MeBo drilling. MeBo drilling was stopped below 5 mbsf because of continuous release of free gas out of the borehole. Carbon isotope measurements of the carbonates showed δ13C values between -38.25 to -52.17 ‰, indicating a mixing of biogenic and thermogenic gas in the methane-derived carbonates. Seismic investigations of the Four-Way Closure Ridge show a well-defined fault below the ridge crest which extends from below the gas hydrate stability zone to the seafloor and acts as a pathway for the methane ascent to the seafloor. 
Seafloor observation using a TV-sled showed a seafloor paved by carbonate rocks consisting of different featured crusts, slabs, and irregular build-ups. Thin-layered crusts were mainly observed at the paved area's rim, while thick-layered slabs and free-standing build-ups were the main features at the elevated region. Chemosynthetic communities, like mussels and clams, mainly were observed within certain carbonate fractures. At the same time, other animals, bacterial mats, and tube worms are presented generally along the whole survey path among the rough seep area. Hydro-acoustic data correlated with visual observation results indicate wide variation through the region of the seep area. Based on our interpretation, the YAM seep area developed over a longer time at the crest of the accretionary ridge, seepage, uplifting of the ridge, tectonic fracturing, and seafloor erosion highly influenced the seafloor manifestation.
Self-modulation of oceanic waves on an ice-covered surface
Authors: Slunyaev Alexey , Stepanyants Yury
Published: March 2022

We study the self-modulation of flexural-gravity waves on a water surface covered by a compressed ice sheet. For weakly nonlinear long perturbations of the potential flow, we derive the nonlinear Schrödinger equation and investigate the conditions when a quasi-sinusoidal wave becomes unstable with respect to the amplitude modulation. The domains of instability are presented in the planes of parameters depending on the values of the local water depth, and the coefficients of ice rigidity/elasticity and of longitudinal stress. We show that under some conditions the occurrence of the modulational instability of oceanic waves under ice looks feasible and present estimates for the real oceanic conditions. Depending on the conditions, bright envelope solitons or dark solitons can emerge on the surface.

A.S. acknowledges the support from Laboratory of Dynamical Systems and Applications NRU HSE (the Ministry of Science and Higher Education of the Russian Federation Grant No. 075-15-2019-1931) and by the Russian Foundation for Basic Research (Grant No. 21-55-15008). Y.S. acknowledges the funding provided by the grant No. FSWE-2020-0007 through the State task program in the sphere of scientific activity of the Ministry of Science and Higher Education of the Russian Federation.
Spring regional sea surface temperature precursors of European summer heat waves
Authors: Beobide-Arsuaga Goratz , Düsterhus André , Müller Wolfgang A. , Barnes Elizabeth A. , Baehr Johanna
Published: March 2022

Past case studies have proposed many different spring and early summer sea surface temperature anomalies (SSTA) over the North Atlantic as precursors of European summer heat waves. Negative SSTAs in the Subpolar Gyre and western tropical Atlantic, and positive SSTAs in North Sea and Mediterranean Sea are few of the examples suggested to precede different European summer heat waves. Any robust description of North Atlantic spring SSTA precursors is further complicated by the large spatial heterogeneity of European summer heat waves and the limited number of observed events. Here, we combine the MPI-Grand Ensemble dataset with its 100 historical simulations (1850-2006) with a Neural-Network-based Explainable Artificial Intelligence method. In this unique data set, we systematically investigate the relevance of the North Atlantic spring SSTAs in preceding different types of European summer heat waves. We find that spring European regional seas provide useful information to differentiate and anticipate different types of European summer heat waves. While positive SSTAs in western Iberian Peninsula precede western European summer heat waves, positive SSTAs in the North Sea or Mediterranean Sea precede eastern European summer heat waves. The regional spring SSTAs relate to distinct soil moisture anomaly patterns in June, which resemble the location of the heat waves. These results could potentially improve seasonal prediction of European summer heat waves.
The aerosol contribution to the rate of anthropogenic warming since 2000
Authors: Jenkins Stuart , Gettelman Andrew , Stier Philip , Grainger Don , Allen Myles
Published: March 2022

Successive IPCC reports have assessed the level of human-induced warming above preindustrial, but much less emphasis has been placed on quantifying the rate of anthropogenic warming, despite the rate of warming being a key variable for ambitious policymaking. The decadal global temperature anomaly trend can be considered a combination of the forced responses from the full range of radiatively-active pollutants, plus the additional trend introduced by natural variability over the previous decade.

The global temperature anomaly trend likely increased in the 2010s, following a temporary pause through the 2000s. Estimates of the globally averaged radiative forcing (RF) timeseries, which are used to attribute the anthropogenic contribution to this recent behaviour, suggest a 50% increase in the anthropogenic RF trend, which largely arises from aerosol RF trend changes since 2000. When these RF timeseries are used to complete a global temperature anomaly attribution (following the technique outlined in the IPCC’s Special Report on the Global Warming of 1.5°C), they suggest that the attributed anthropogenic warming rate has increased by between 50 and 100% since 2000, pushing the estimated rate of net anthropogenic warming up to around 0.3°C/decade since 2010.

We study the global observational evidence supporting the aerosol trends presented in these RF datasets, and thus aim to determine the likely anthropogenic contribution to the perceived warming acceleration behaviour since 2000. We argue that while observations do support the claim that RF trends are partly responsible for the warming trend (and importantly do support the best-estimate RF trend estimates in this ensemble), observational evidence is circumstantial, with a counterhypothesis that aerosol RFs make only a small contribution to the warming trend since 2000 consistently failing to be disproven across the full ensemble of RFs.

This occurs because observed trends in radiative fluxes and global temperatures are significantly influenced by internal variability, principally ENSO and PDO, precluding a clearer assessment of the externally forced behaviour over the short global observational records we have. In light of this uncertainty, considerable caution is required in predictions or policy judgments that depend on the precise current anthropogenic warming trend, such as the time remaining to, or the outstanding carbon budget consistent with, a warming of 1.5°C, since these may be influenced considerably by recent changes in aerosol forcing behaviour.
Metallogeny of Manto-type Copper Deposits of Iran: A Possible Link to the Evaporitic basins
Authors: Momenipour Sara , Rajabi Abdorrahman , Rezaei Somaye
Published: March 2022

Abstract

Iran is one of the most significant producers of copper in the world and hosts varieties of copper deposits, including porphyry Cu-Mo, vein-type, volcanogenic massive sulfide (VMS), sediment-hosted stratabound copper (SSC), Manto-type, and skarn.

Manto-type deposits are the second producer of copper in Iran, mostly hosted in basalt, basalt-andesite to andesite volcanic rocks. There are more than 40 Manto-type copper deposits and occurrences in Iran, such as Mari, Abbas-Abad, Vorezg, Robat, Simakan, and Sorkho, and most of them are economically deposits. Most of these deposits occur in Eocene volcanic rocks, and a small amount of them (such as KeshtMahki, Hassanabad, Khorjan, and Simakan) are hosted in the Early Cretaceous volcanic rocks that mainly concentrated in the Saveh-Yazd (in the Urumieh-Dokhtar magmatic belt), Qazvin-Zanjan, Sabzevar-Neishabour, Semnan-Shahroud volcanic zones, and eastern Iran.

The stratabound sulfide ores in these Manto-type copper deposits include chalcocite, chalcopyrite, and bornite, associated with covellite, malachite, atacamite, chrysocolla, and minor azurite in the oxidized and supergene ore zones. Sulfide mineralization usually occurs as a replacement in pyrites and feldspars, vein and veinless, and breccia, which is accompanied by carbonatization, propylitic, and minor sericite alterations. Geological and geochemical data indicate that most of these deposits formed within plate failed continental rift and back-arc extensional environments related to the subduction of the oceanic crust of neo-Tethys beneath the Iranian Plateau.

Furthermore, the temporal and spatial distribution of these deposits in terms of time shows a close relationship with evaporitic basins. This phenomenon suggests a genetic relationship between the formation of Manto-type deposits and the circulation of brines from adjacent evaporitic basins in shallow extensional tectonic environments.
Evaluation of fate and transport of macro- and micro-plastics in terrestrial-aquatic continuum of entire Japan by developing a spatio-temporally explicit eco-hydrology model
Authors: Nakayama Tadanobu , Osako Masahiro
Published: March 2022

Contamination of plastic materials in our environment has received more attention from the public, scientists, and policy makers during the last few decades. Though some of the models have succeeded to simulate the transport and fate of plastic debris in freshwater systems, a complete model is under development to elucidate the whole picture of plastic dynamics in the basin scale. One of the authors has so far developed a process-based eco-hydrology model, NICE (National Integrated Catchment-based Eco-hydrology) (Nakayama and Watanabe, 2004) and NICE-BGC (BioGeochemical Cycle) (Nakayama, 2017), and applied them to various basins from local/regional to continental/global scales. NICE-BGC can simulate iteratively nonlinear interactions between hydrologic, geomorphic, and ecological processes (water, heat, sediment, nutrient, and carbon cycles, etc.) (Nakayama, 2020). In this study, the authors extended NICE-BGC to couple with plastic debris model for freshwater systems, and applied it to all the first-class river basins in entire Japan (109 river basins). The new model included the advection, dispersion, diffusion, settling, dissolution and deterioration due to light and temperature, but assumed no interaction with suspended matter (heteroaggregation), resuspension, biofouling, and effect of wind, etc. The authors also assumed plastics as pure and totally inert polymers and spherical particles with constant size and density for model simplification. NICE-BGC simulated how mismanaged plastic waste (MPW) of about 36,000 ton/yr (Meijer et al., 2021) and point sources such as tyres, personal care products (PCPs), dust, and laundry in the entire country are transported from land to river, and finally to the ocean. The model showed the total flux of macro- and micro-plastics varies dependent on the removal efficiency of micro-plastic in wastewater treatment plants and the density of plastic. It was clear that only limited plastics discharged to land flows out into the ocean intensively during rainfall seasons, similar to plastic loading estimates in the previous study (Nihei et al., 2020). These results help to quantify the impacts of plastic waste on terrestrial and aquatic ecosystems, and find solutions and measures to reduce plastic input to the ocean.
A novel watershed scale Snow Water Equivalent (SWE) correction approach, using stream flow and remote sensing data
Authors: Whittaker Charles , Leconte Robert
Published: March 2022

Flood forecasting agencies and hydropower companies require cost effective approaches for accurate estimation of snow water equivalent (SWE) to improve spring flow forecast and to make informed decision about reservoir operation.  The lack of accurate SWE estimation at the watershed scale is an issue in northern watersheds, as snow surveys are either absent, or sparsely distributed and infrequent (monthly to bi-weekly). Remotely sensed SWE data sets retrieved from passive microwave satellites, such as GlobSnow, offers the advantage of high frequent coverage of the Northern Hemisphere at the watershed scale.  The main issue is that SWE is typically underestimated because of vegetation. Also, the signal saturates for deep snowpacks.  An approach is therefore required to correct GlobSnow which does not resort to local SWE measurements.

A correction factor approach which focuses on improving the Maximum Snow Water Equivalent (MSWE) estimate for a watershed produced by publicly available regional databases, such as GlobSnow, has been developed. The method does not require point SWE measurements and assumes that the spring runoff volume calculated from historical streamflow observations equals the total snow melt volume retrieved from GlobSnow’s MSWE, less infiltration into frozen ground. The latter is calculated from freely available hydro-meteorological information. The method presented below introduces a cost-effective approach which can bridge the temporal and spatial sparsity that is often associated with the snow survey programs.

The results from applying this approach to the regional GlobSnow database to northern watersheds in Quebec show that the Corrected GlobSnow (C-Glob) more accurately correlates to the manual snow surveys, compared to the uncorrected GlobSnow data source. The corrected database may prove especially useful for watersheds where no SWE measurements are available, may serve as a supplementary source of information to better understand what takes place over the entire watershed by filling gaps of manual surveys.
Sea water chemistry during Archean-Paleoproterozoic transition: Insight from the Aravalli Supergroup, India.
Authors: Goswami Abhisikta , Mohanty Sarada Prasad , Sarangi Shushanta
Published: March 2022

The Paleoproterozoic Aravalli Supergroup has an unconformable relationship with the Mewar Gneissic Complex (MGC) of Archean age. The MGC in the Umra area, Rajasthan, India is represented by gneisses, granite, and amphibolite, and has development of a paleosol horizon below the unconformity surface separating it from the Aravalli Supergroup. The Aravalli metasediments have undergone metamorphism up to greenschist facies and have a scattered age of about 2.3-1.8 Ga. The lower part of the Paleoproterozoic succession comprises conglomerates, volcanics, carbonates with microbial mats, and carbonaceous phyllites. These metasediments provide geochemical proxies to the seawater conditions during the Great Oxidation Event (GOE) as these happen to lie on the age range where the Archean-Proterozoic transition occurred.  

Conglomerates present in the lower part of the Aravalli Supergroup are polymictic, clast to matrix-supported, and massive. Euhedral magnetite grains scattered in the matrix indicate a suboxic-anoxic condition of deposition. The overlying carbonates of the area show both negative as well as positive δ13CV-PDB   excursions.  The positive δ13C excursion can be correlated with the Lomagundi event. This excursion indicates a warm water condition at the time of the GOE and is supported by the presence of microbial mats in the carbonate unit. On the other hand, the negative excursion may be representative of the Paleoproterozoic glaciation event. The PAAS normalized REE data of the carbonates have HREE>LREE, with a flat to positive Ce* and Eu* anomalies and no significant Y-anomaly, indicating a suboxic-anoxic condition of seawater during deposition in a shallow sea. The carbon phyllite present above the carbonate unit in the area hosts uranium mineralization which is associated with chalcopyrite and pyrite. The Δ34S data of the pyrites show a reducing environmental condition of mineralization. The studies related to the metasediments of the Aravalli Supergroup provide a clue to the seawater conditions that prevailed during the Archean-Proterozoic transition and also provide deeper insights into the Great Oxidation Event.  

 
SISAL speleothem database updates - link to modern monitoring data, additional proxies and increased accessibility
Authors: Kaushal Nikita , Lechleitner Franziska A. , Tanos Peter , Hatvani Istvan Gabor , Kern Zoltan , Wilhelm Micah , Burstyn Yuval , Baker Andy
Published: March 2022

Speleothem archives (cave carbonates) are widely distributed in terrestrial regions, and provide highly resolved records of past changes in climate and vegetation encoded in the oxygen and carbon isotope proxies. The SISALv2 database, created by the PAGES-SISAL Phase 1 Working Group, provided 700 speleothem records from 293 cave sites, 500 of which have standardized chronologies. The database provides access to records that were hitherto unavailable in the original publications and/or repositories, and has enabled regional-to-global scale analysis of climatic patterns using a variety of approaches such as data-model comparisons. 

The PAGES-SISAL Phase 2 Working Group is a continuation of the previous efforts to index speleothem datasets, focusing on the following objectives: (i) exploring ways to synthesise modern cave monitoring data to provide robust modern baselines and improve proxy interpretations, (ii) adding trace element proxies of Mg, Sr, Ba, U, and Sr isotopes to the SISAL database to increase our understanding of regional climatic variability, (iii) a database-update to incorporate ~100 identified speleothem datasets that are currently not in the database, (iv) providing a javascript web app with a user-friendly GUI to increase SISAL data accessibility.

Here, we present preliminary information on available cave monitoring metadata synthesized from the Cave Monitoring Database (product of a Cave Monitoring workshop in Innsbruck, Austria) and published speleothem trace element records, highlighting regions where overlapping stable isotope, trace element and monitoring datasets are available, and identifying gaps. We show the proposed database structures for cave monitoring and speleothem trace element data, linking them to the speleothem entities in the existing SISAL database with persistent identifiers, and introduce the Beta version of the SISAL GUI. We briefly present a synopsis of the SISAL-community level discussions on best practices for reporting trace element data, and reducing data measured with high resolution laser ablation methods. 

We welcome feedback on PAGES-SISAL Phase 2 activities listed above, and encourage participation and collaboration from interested researchers in different stages of their academic career and working in different geographical regions and allied disciplines.
Chemical characteristics of summer rainwater at an urban site in South Korea
Authors: Park Hyemin , Kim Taeyong , Yang Minjune
Published: March 2022

In this study, we investigated the chemical characteristics of rainwater and evaluated the correlation among rainwater quality factors for seven precipitation events from June 2020 to August 2020. Rainwater samples (n = 84) were collected every 50 mL at Pukyong National University, Busan, South Korea. Values of pH and electrical conductivity (EC) were measured in the field, and concentrations of water-soluble cations (Na+, Mg2+, K+, Ca2+, and NH4+) and anions (Cl-, NO3-, and SO42-) were determined using ion chromatography. For all rainwater samples, the pH ranged from 3.63 to 5.59, with mean pH = 4.78, and the measured mean EC was 30.54 µS/cm, indicating that the precipitation was acidified in Busan, South Korea. A strong negative correlation (r = -0.83) was found between the pH and EC values. The major ionic components of rainwater were SO42- > NH4+ > NO3-, which are predominantly attributed to anthropogenic forces in the study area, such as emissions from vessels and fossil fuels. Anion concentrations of rainwater samples were SO42- (average concentration: 2.15 mg/L) > NO3- (1.43 mg/L) > Cl- (1.04 mg/L) and showed a strong positive correlation with EC values (r = 0.81) and a negative correlation with pH values (r = -0.72) of rainwater samples. The average concentrations of cations (NH4+ (1.56 mg/L) > Ca2+ (1.31 mg/L) > Na+ (0.63 mg/L) > K+ (0.57 mg/L) > Mg2+(0.29 mg/L)) were relatively lower than those of anions. Cation concentrations showed no significant correlation with the values of EC (r = 0.29) and pH (r = -0.21). The result of this study indicates that acidic precipitation occurs even in summer with relatively low concentrations of air pollution and strong rainfall intensity.
Upper ocean flux of calcite produced by the Arctic planktonic foraminifera Neogloboquadrina pachyderma
Authors: Tell Franziska , Jonkers Lukas , Meilland Julie , Kucera Michal
Published: March 2022

Planktonic foraminifera, marine protists and calcifiers, are globally responsible for about one quarter of the global pelagic calcite flux, but their contribution to it in the subarctic and Arctic realm has not been fully resolved. With ongoing warming and sea ice loss, the Arctic Ocean and its marginal seas are becoming more hospitable to pelagic calcifiers like planktonic foraminifera, resulting in modifications of the regional carbonate cycle and the composition of the seafloor sediment. To quantify planktonic foraminifera Arctic calcite production and loss in the upper water layer, we compile and analyze data on the dominant planktonic foraminifera species of the Arctic realm, Neogloboquadrina pachyderma, from vertical profiles in the upper water column. Using summertime observations of shell concentrations, sizes and weights of this species across the Arctic, we calculate the base of the productive zone of N. pachyderma to be regionally highly variable, on average located at 125 m, at maximum at 300 m. The calcite flux immediately below the productive zone (production flux) is on average 8 mg CaCO3 m-2 d-1, and we observe that this flux is attenuated until at least 300 m below the base of the productive zone. Across the Arctic realm, the summer production flux of N. pachyderma calcite varies by more than two orders of magnitude and the estimated mean export flux below the twilight zone is sufficient to account for about a quarter of the total pelagic carbonate flux in the region. These results indicate that estimates of the Arctic pelagic carbonate budget will have to account for large regional differences in production flux of the major pelagic calcifiers and confirm that substantial attenuation of the production flux occurs in the twilight zone.
The Effects of Seasonal Variation on GPS Height Component
Authors: Tekin Ünlütürk Nihal , Doğan Uğur
Published: March 2022

In this study, the effects of seasonal variation on the vertical position accuracy of GPS calculated by time series analysis of continuous GPS stations were investigated. Weather changes, water vapor in the atmosphere affect the position accuracy of GPS and cause fluctuations in GPS height values. It is also known that the height component has more air passage changes. Since it is easier to interpret the effects of the height component due to its topographic features and seasonal changes are more effective than the rest of the country, four continuous GPS stations, covering the 2014-2019 date range, from the Turkish National Permanent GNSS Network (TUSAGA-Aktif) were used in the East of Turkey were chosen. The daily coordinates of the stations were obtained as a result of GAMIT/GLOBK software solution. By applying time series analysis to the daily coordinate values of the stations, statistically significant trend, periodic and stochastic components of the stations were determined. As a result of the analysis, the vertical annual velocities of the stations and the standard deviations of the velocities were determined.

For the stations determined according to the ellipsoid heights, the velocity and standard deviation values of the height component were calculated for each month, season and year. As the ellipsoid height increases, the velocity and its standard deviation values decrease. While the minimum velocity values are observed for the station with the lowest ellipsoidal height in winter, for the station with the highest ellipsoidal height in autumn, the minimum their standard deviation values are determined in winter for the station with the lowest ellipsoidal height, and in summer for the station with the highest ellipsoidal height. According to the results obtained, the coordinate displacements caused by seasonal variation may be important and their effects should be considered especially in high precision geodetic surveys.

In addition, the velocity values of the stations were calculated for different years, and a decrease was observed in the height component depending on the observation duration. As the observation duration for the height component increases, both the velocity values and their standard deviation values decrease. In order to avoid velocity estimation error completely, the data length should be more than 4.5 years.

Keywords: GPS height compenent, GPS time series, Seasonal effect, Velocity estimation
Different optimum solar activity proxies for foF2 at middle and low latitudes
Authors: Laštovička Jan
Published: March 2022

To model ionospheric climate and to study its long-term changes and trends we need solar activity proxies, because long and homogeneous data series of solar ionizing flux are not available. To select the optimum solar activity proxies, we use yearly average foF2 data of eleven ionospheric stations from middle and low/equatorial latitudes of four continents over 1976-2014 and six solar activity proxies, F10.7, sunspot numbers, F30, Mg II, He II and solar Lyman-α flux. For middle latitudes and higher low latitudes down to about 20-24oN, Mg II and F30 are found to be the optimum solar proxies, not the usually used F10.7 or sunspot numbers. At lower and particularly equatorial latitudes the situation is different; the optimum proxy for Jicamarca is sunspot number and He II, and for Vanimo He II. Solar activity describes 99% of the total variance of yearly foF2 at midlatitudes and its dependence on solar proxies is highly linear. Long-term trends in foF2 are found to depend to some extent on solar proxy used
Past Evolution of Western Europe Large-scale Circulation and Link to Extreme Precipitation Trend in the Northern French Alps
Authors: Blanc Antoine , Blanchet Juliette , Creutin Jean-Dominique
Published: March 2022

Detecting trends in regional large-scale circulation (LSC) is an important challenge as LSC is a key driver of local weather conditions. In this work, we investigate the past evolution of Western Europe LSC based on the 500 hPa geopotential height fields from 20CRv2c (1851-2010), ERA20C (1900-2010) and ERA5 (1950-2010) reanalyses. We focus on the evolution of large-scale circulation characteristics using three atmospheric descriptors that are based on analogy, by comparing daily geopotential height fields to each other. They characterize the stationarity of geopotential shape and how well a geopotential shape is reproduced in the climatology. A non-analogy descriptor is also employed to account for the intensity of the centers of action. We then combine the four atmospheric descriptors with an existing weather pattern classification over the period 1950-2019 to study the recent changes in the main atmospheric influences driving precipitation in the Northern French Alps. Even though LSC characteristics and trends are consistent among the three reanalyses after 1950, we find major differences between 20CRv2c and ERA20C from 1900 to 1950 in accordance with previous studies. Notably, ERA20C produces flatter geopotential shapes in the beginning of the 20th century and shows a reinforcement of the meridional pressure gradient that is not observed in 20CRv2c. Over the period 1950-2019, we show that winter Atlantic circulations (zonal flows) tend to be shifted northward and they become more similar to known Atlantic circulations. Mediterranean circulations tend to become more stationary, more similar to known Mediterranean circulations and associated with stronger centers of action in autumn, while an opposite behaviour is observed in winter. Finally, we discuss the responsibility of these LSC changes for extreme precipitation in the Northern French Alps. We show these changes in LSC characteristics are linked to more circulations that are likely to generate extreme precipitation in autumn.
Oblique instabilities driven by pickup ion ring-beam distributions in the outer heliosheath
Authors: Mousavi Ameneh , Liu Kaijun , Sadeghzadeh Sina
Published: March 2022

The energetic neutral atom (ENA) ribbon observed by the Interstellar Boundary Explorer (IBEX) spacecraft is believed to originate from the pickup ions in the outer heliosheath. The outer heliosheath pickup ions generally have a ring-beam velocity distribution at a certain pickup angle, α, the angle at which these ions are picked up by the interstellar magnetic field. The pickup ion ring-beam distributions can drive unstable waves of different propagation angles with respect to the background interstellar magnetic field, θ. Previous studies of the outer heliosheath pickup ion dynamics were mainly focused on ring-like pickup ion distributions with α≈90° and/or the parallel- and anti-parallel-propagating unstable waves (θ=0°and 180°). The present study carries out linear kinetic instability analysis to investigate both the parallel and oblique unstable modes (0°≤θ≤180°) driven by ring-beam pickup ion distributions of different pickup angles between 0° and 90°. Our linear analysis reveals that ring-beam pickup ions can excite mirror waves as well as oblique left-helicity waves and their harmonics. The maximum growth rate of the mirror mode increases with increasing α. On the other hand, the wavenumber and growth rate of the most unstable oblique left-helicity modes are consistent with the unstable modes of 0°and 180° examined in our earlier work.
Imbricated trains of massive coastal rock clasts (103–104 kg) on Ludao Island, Taiwan: what they can and cannot tell us about palaeotyphoons
Authors: Terry James , Lau Annie , Nguyen Kim Anh , Liou Yuei-An , Switzer Adam
Published: March 2022

Ludao Island in south eastern Taiwan regularly experiences strong Pacific typhoons.  Fieldwork was undertaken to investigate the characteristics of a boulder field comprising massive limestone and volcanic clasts (103–104 kg) on the exposed SE coast.  Old large clasts on the Holocene emerged platform provide evidence for multiple high-energy palaeowave events.  Of particular interest were clasts stacked and imbricated together to form distinct boulder trains.  Inferred minimum flow velocities of 4.3–13.8 m/s were needed for their deposition.  What can imbricated boulder trains tell us about the wave processes and geomorphic influences responsible?  One hypothesis here is that localized funnelling of water flow through narrow relict channels is able to concentrate onshore flow energy into powerful jets.  These channels represent inherited (fossil) spur-and-groove morphology, oriented perpendicular to the modern reef edge, now overdeepened by subaerial karstic solution.  Support for this idea is the location and train-of-direction of the main imbricated boulder cluster at the landward head of one such feature.  Geomorphic controls amplifying wave-breaking flow velocities across Ludao's coastal platform mean that a palaeotyphoon origin is sufficient to account for large rock clast stacking and imbrication, without recourse to a tsunami hypothesis.
Influence of ground station network distribution on orbit accuracy of low Earth orbit (LEO) satellites
Authors: He Xingchi , Hugentobler Urs , Schlicht Anja , Nie Yufeng , Duan Bingbing
Published: March 2022

Since 2010s, many companies such as SpaceX, OneWeb, Amazon and Samsung showed their interests to launch hundreds and even thousands of low Earth orbit (LEO) satellites for global internet service. Due to their unique characteristics compared to medium Earth orbit (MEO) and geostationary Earth orbit (GEO) satellites, these LEO mega-constellations soon draw much attention from the scientific community. Studies from constellation design, to applications such as positioning, ionosphere modelling and gravity recovery are investigated by many researchers.

Orbit determination is a key to many applications. Traditionally, onboard Global Navigation Satellite System (GNSS) receivers are used to determine LEO satellite orbits. However, with thousands of satellites in space in the future, an independent system without relying on GNSS is worth to be studied. Since these LEO satellites are intended for internet service, connections between the satellites and to the ground are available by nature. But how would the distribution of a station network affect the orbit accuracy? How many stations would be sufficient to determine a precise orbit? Besides observations from ground stations, inter-satellite link (ISL) is also proposed and implemented by many current GNSSs. It already showed its potential to improve the orbits. Could this technique also be applied to the orbit determination of LEO satellites?

This simulation study investigates the influence of ground station distribution to orbit determination, as well as the benefit from ISL observations. By using a constellation with 60 LEO satellites, we show that for regional station networks, a high latitude network leads to worse orbit accuracy than a middle or low latitude network. With the help of ISL observations, orbit errors reach the same level as a global station network. We further investigate the influence of different number of stations contained in the network. The results prove that although increasing the station number could improve orbits, the improvement is minimal when the global network contains more than 16 stations. While for a regional network, even with 60 stations, the orbit errors are 1.5 times larger than for a small global network with 6 stations. This proves that the ground station distribution is more important than the number of observations. Furthermore, if the ISL technique is adopted, even a regional station network with 16 stations could be sufficient to determine an accurate orbit.