bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of mesoscale eddies on the transport of low-salinity water from the Bay of Bengal into the Arabian Sea during winter
Authors: Zhu Jiechao , Zhang Yuhong , Cheng Xuhua , Wang Xiangpeng , Sun Qiwei , Du Yan
Published: February 2023

Abstract: The distribution of sea surface salinity (SSS) in the Arabian Sea (AS) and Bay of Bengal (BoB) is in contrast due to differences in air-sea freshwater fluxes and river runoff inputs.The monsoon-induced inter-basin water exchange plays an important role in regional salinity balance and atmosphere-ocean feedback in the North Indian Ocean. The satellite SSS dataset reveals that significant intraseasonal variability of SSS occurs in the region south of the Indian Peninsula with the strongest amplitude in winter. A case study in autumn-winter of 2016 showed that the Northeast Monsoon Current (NMC) and mesoscale eddies play a dominant role in the intraseasonal variability of the SSS in the region south of the Indian peninsula. In November, the East India Coastal Current (EICC) transports the low-salinity water southward to the region east of Sri Lanka. Meanwhile, a cyclonic eddy develops and propagates westward south of the NMC. Both NMC and the cyclonic eddy advects the low-salinity water westward to the region south of the Indian Peninsula. Then, an anticyclonic eddy generates in the north of the NMC. Thus, an eddy pair forms for more than one and a half months, which develops and propagates westward, transporting low-salinity water westward. The perturbation of mesoscale eddies and SSS gradient leads to the significant intraseasonal variability of SSS there.Key words: Sea Surface Salinity; intraseasonal variability; mesoscale eddies; North Indian Ocean
Estimating sediment carbon stocks in the environment of Taiwan's coastal blue carbon system
Authors: Tang Zih-Wei , Chen Huei-Fen
Published: February 2023

The blue carbon system generally refers to the carbon sink environment that can be stored in the ocean system, and these environments are mainly mangroves, seagrass beds and salt marshes. This study investigates the second-largest seagrass bed in Kenting in Southern Taiwan. In addition to the advantages of high ecological diversity, seagrass beds are also considered to be a high carbon storage environment, which is more capable of sequestering carbon in the atmosphere than green carbon systems. In risk assessment, green carbon system may have fire risks, causing the sequestered carbon in plants to be released back into the atmosphere. Therefore, we believe that research on coastal blue carbon systems and carbon sequestration issues are better development goal and direction. To understand how much total organic carbon can be sequestered in seagrass bed sediments under natural growth, and to estimate how many tons of carbon equivalent (CO2e) in the atmosphere the carbon sequestered in this area are our ultimate goal. In the choice of sampling sites, we collected two seagrass bed sediment cores about 40 cm long, namely core A (BH2-SG)(coring in the seagrass area), and core B (BH1-NSG)(coring in the bare area on the seagrass bed). The analysis results showed that the organic carbon content of sediment core A was 0.184-0.298 wt%, with an average content of 0.237 wt%, and that of sediment core B was 0.188-0.401 wt%, with an average content of 0.318 wt%. After plugging in the organic carbon accumulation content formula (MgC *ha-1= (TOC(%)*depth(cm)*BD(g/cm3)), we can get the organic carbon accumulation values of sediment core A (13.539 MgC*ha-1) and sediment core B (18.405 MgC*ha-1). For now, we can only evaluate the carbon accumulation of the upper 40 cm seagrass bed sediments in this area. The average accumulated carbon content of the two cores is multiplied by the total area of the Kenting seagrass bed (about 4.38 ha), and then multiplied by the carbon dioxide equivalent coefficient 3.67 represents its carbon dioxide equivalent (CO2e) (the content value is 256.49 CO2e). At last, we consider that the area is a major factor affecting the amount of carbon storage. If we can increase seagrass area, more carbon can be stored in the sediment. Keywords: Kenting, Taiwan, blue carbon system, seagrass bed, organic carbon content (TOC%), carbon dioxide equivalent (CO2e)
Increasing cryospheric hazards and sediment supply threaten water quality and hydropower systems in high mountain areas
Authors: Li Dongfeng , Lu Xixi , Walling Desmond , Zhang Ting , Steiner Jakob , Wasson Robert , Stephan Harrison , Nepal Santosh , Nie Yong , Immerzeel Walter , Shugar Dan , Koppes Michèle , Lane Stuart , Bolch Tobias
Published: February 2023

Global warming-induced melting and thawing of the cryosphere are rapidly changing hydrogeomorphic processes and cryospheric hazards in high mountain areas worldwide. These processes and hazards include glacial retreat and collapses, permafrost thaw and associated landslides, rock-ice avalanches, debris flows, and outburst floods from glacier lakes and landslide-dammed lakes. The changing slope instability and extreme flood have accelerated landscape erosion and increased fluvial sediment loads. For example, the rivers in High Mountain Asia are becoming muddier due to increased suspended particulate matters from melting glaciers and thawing permafrost, likely degrading water quality as fine-grained sediment are easily bonded with organic carbon, phosphorus and most heavy metals (e.g., mercury, chromium, arsenic and lead). Importantly, numerous hydropower dams and reservoirs are under construction or planning in high-mountain areas worldwide such as in the Himalaya and Andes. The increasing amounts of mobilized sediment can fill up reservoirs, cause dam failure, and degrade power turbines, threatening the short-term safety and longer-term sustainability of these hydropower systems.In the future, we recommend forward-looking design and maintenance solutions that can help transition towards climate change-resilient high-quality water supply and hydropower systems in high-mountain areas. The specific suggestions include: (i) monitor the climate, glaciers and permafrost, glacial lakes, unstable slopes, discharge and sediment yields to better understand the cascading links between climate change, glacier retreat and hazards; (ii) predict future fluvial sediment loads, water quality and reservoir sedimentation in a changing climate and develop sustainable sediment management solutions; (iii) establish real-time early warning systems and enhance social awareness and drills, especially for in-construction dams to minimize human and infrastructure losses; (iv) enhance transboundary cooperation by establishing data-sharing schemes and adopting joint-operation strategies to better cope with hazards and optimise sediment flushing; and (v) promote the inclusion of indigenous and local knowledge in policy, governance, and management for water quality assessment and dam and reservoir construction.The major results of this study have been published online: Li, D., Lu, X., Walling, D. E., Zhang, T., Steiner, J. F., Wasson, R. J., ... & Bolch, T. (2022). High Mountain Asia hydropower systems threatened by climate-driven landscape instability. Nature Geoscience, 15(7), 520-530. https://doi.org/10.1038/s41561-022-00953-y
Data filtering methods for broadband spectral electrical impedance tomography (sEIT) measurements to reduce electromagnetic coupling effects
Authors: Wang Haoran , Huisman Johan Alexander , Zimmermann Egon , Vereecken Harry
Published: February 2023

Spectral electrical impedance tomography (sEIT) is a non-invasive geophysical method to image the complex resistivity distribution of subsurface materials in a broad frequency range. Laboratory studies of spectral induced polarization (SIP) have prompted the application of sEIT at the field scale in recent years. However, electromagnetic (EM) coupling effects including both inductive and capacitive coupling can affect the accuracy of sEIT measurements, especially at higher frequencies. With the development of advanced measurement equipment and the use of shielded cables, EM coupling effects can be reduced to a large extent and the remaining EM coupling is mainly due to the use of long cables. The aim of this work is to develop filters to remove sEIT measurements with large inductive and capacitive coupling effects and to conduct inversion without correction of the data. Inductive coupling is independent of soil properties and can be quantified by the mutual inductance determined from known cable positions. It is the most important source of EM coupling in conductive environments. Previous work proposed correction methods for inductive coupling in sEIT measurements. To achieve inversion without correction, we propose an index called inductive coupling strength (ICS) to evaluate the inductive coupling for a given measurement configuration. Capacitive coupling is more complicated to correct and avoid, and it is the dominant source of EM coupling in resistive environments. Previous studies showed promising correction results by integrating the capacitances in the forward modelling. However, the proposed correction method was not sufficiently accurate for high frequencies in resistive environments. To achieve inversion without correction, we propose an index called capacitive coupling strength (CCS) based on sEIT modelling with capacitances and leakage currents to quantify the influence of capacitive coupling on each measurement configuration. To evaluate the use of ICS and CCS for data filtering, we use two field sEIT datasets. The first dataset was acquired in a conductive environment and the second dataset was acquired in a resistive environment. We found that reliable inversion results over a broad frequency range up to kHz can be obtained without correction for EM coupling effects by using a 5% threshold value for ICS and CCS to filter out measurements with significant EM coupling effects. 
Dispersion of particle-reactive elements caused by the phase transitions in scavenging
Authors: Kim Kyeong Ok , Maderich ﻿Vladimir , Brovchenko ﻿Igor , Jung ﻿Kyung Tae , Kivva ﻿Sergey , Kovalets ﻿Katherine , Kim ﻿Haejin
Published: February 2023

A generalized model of scavenging of the reactive radionuclide 239,240Pu was developed, in which the sorption-desorption processes of oxidized and reduced forms on multifraction suspended particulate matter are described by first-order kinetics. One-dimensional transport-diffusion-reaction equations were solved analytically and numerically. In the idealized case of instantaneous release of 239,240Pu on the ocean surface, the profile of concentrations asymptotically tends to the symmetric spreading bulge in the form of a Gaussian moving downward with constant velocity. The corresponding diffusion coefficient is the sum of the physical diffusivity and the apparent diffusivity caused by the reversible phase transitions between the dissolved and particulate states. Using the method of moments, we analytically obtained formulas for both the velocity of the center mass and apparent diffusivity. It was found that in ocean waters that have oxygen present at great depths, we can consider in the first approximation a simplified problem for a mixture of forms with a single effective distribution coefficient, as opposed to considering the complete problem. This conclusion was confirmed by the modeling results for the well-ventilated Eastern Mediterranean. In agreement with the measurements, the calculations demonstrate the presence of a maximum that is slowly descending for all forms of concentration. The ratio of the reduced form to the oxidized form was approximately 0.22-0.24. At the same time, 239,240Pu scavenging calculations for the anoxic Black Sea deep water reproduced the transition from the oxidized to reduced form of 239,240Pu with depth in accordance with the measurement data.
Why do our models underestimate regional groundwater trends?
Authors: Lischeid Gunnar , Steidl Jörg
Published: February 2023

In the course of climate change serious effects on groundwater resources are expected. Future groundwater recharge is usually assessed via hydrological models. Various studies have shown that most models fail in depicting pronounced trends observed in groundwater monitoring data at regional scales. Likewise, global hydrological models seem to systematically underestimate the low-frequency dynamics of regional water storages in the GRACE mission data (Scanlon et al. 2018) or long-lasting memory effects in terms of discharge (Fowler et al. 2022). Thus groundwater recharge modelling appears to have some fundamental problems that go far beyond the usual model uncertainties in each individual case.This was systematically investigated. The empirical basis was given by the analysis of groundwater data of the authorities’ monitoring networks in Northeast Germany, covering an area of more than 50,000 km2. About 240 long-term time series of groundwater head and lake water level were studied. It could be shown that at weekly or monthly time scales lake water level dynamics very closely mimicked that of the adjacent groundwater body.A very close correlation between the direction and strength of the trends and the degree of damping of the signal of groundwater recharge was found. The probability of long-term trends systematically increased with the thickness of the vadose zone. This indicates the crucial role of long-term accumulation of soil moisture deficits in the deeper unsaturated zone.In contrast, models of groundwater recharge generally consider only the uppermost soil layers. In addition, modellers usually assume initial steady-state equilibrium conditions and thus ignore long-term memory effects in the subsurface. Simulations with different models clearly showed that this resulted in a systematic underestimation of long-term trends. Finally, it was found that model parameterizations which had been optimized with respect to discharge or topsoil moisture dynamics were not necessarily optimal for the simulation of groundwater recharge. Based on these findings clear recommendations for monitoring and model-based assessment of groundwater recharge will be given. References:Scanlon et al. (2018), PNAS, http://ww.pnas.org/cgi/doi/10.1073/pnas.1704665115Fowler et al. (2022), WRR, https://doi.org/10.1029/2021WR031210Lischeid et al. (2021), JHyd, https://doi.org/10.1016/j.jhydrol.2021.12609
Experimental studies on the role of bacteriophages in the formation of carbonates and sulphides
Authors: Działak Paweł , Borkowski Andrzej
Published: February 2023

Bacteriophages are abundant in all environments on the Earth. However, their impact on mineral formation remains undiscovered. In our experimental approach, two distinctly different bacteriophages (Pseudomonas phage Φ6 and Escherichia phage P1) were used to assess their influence on mineral formation. Here, we focus on the formation of carbonates and sulfides.Bacteriophages are supposed to influence carbonate precipitation. We demonstrated that bacteriophages induce the formation of regular ‘viral-like’ mineral particles. These particles were strongly aggregated, while such phenomena did not occur in the control sample. Moreover, bacteriophages induced the formation of vaterite (an unstable form of calcium carbonate), which remained stable for a longer time. The origin of framboidal pyrite is an important issue from the point of view of the precipitation of sulfide minerals. It is assumed that ions present in the solution can be bound by bacteriophages and thus influence mineral precipitation. We postulated that bacteriophages might be one of the factors that induce the precipitation of finer mineral particles, which can then be formed into framboid-like structures. It seems that bacteriophages may play a crucial role in the precipitation of various minerals. In our research, for both minerals, similar phenomena occurred: (i) change in the shape of mineral particles; (ii) occurrence of aggregation/agglomeration in the presence of bacteriophages; (iii) change in the size of agglomerates/aggregates. Moreover, XRD patterns were different for carbonates precipitated in the presence of bacteriophages. However, such differences were not visible for sulfides, probably due to the strong oxidation caused by the difficulties in maintaining the samples.
Zinc nanoparticles combat boscalid-resistance in Alternaria alternata
Authors: Malandrakis Anastasios , Kavroulakis Nektarios , Chrysikopoulos Constantinos
Published: February 2023

The potential of ZnO nanoparticles (NPs) to control Alternaria alternata isolates resistant to the succinate dehydrogenase inhibitor (SDHI) boscalid was evaluated both in vitro and in vivo. ZnONPs could effectively inhibit mycelial growth and suppress disease symptoms in both boscalid sensitive (BOSC-S) and resistant (BOSC-R) isolates. A high synergistic effect against BOSC-S and BOSC-R isolates was observed when ZnO-NPs was combined with boscalid both in vitro and when applied in artificially inoculated tomato fruit. The positive correlation between nanoparticles and their ionic counterpart ZnSO4 and the neutralization of the ZnO-NPs fungitoxic action in the presence of EDTA suggested that zinc ion release is the most probable fungitoxic mechanism of ZnO-NPs. The disruption of cellular ion homeostasis mechanisms by zinc NPs could account for the enhanced effectiveness of ZnO-NPs against A. alternata  compared to ZnSO4. ATP-dependent ion efflux and ROS production could contribute to the fungitoxic action of ZnO-NPs as indicated by bioassays with ATP- and antioxidant-inhibitors. Boscalid acting as a “capping” agent for ZnO-NPs, significantly reducing NPs mean size, probably accounted for the synergy observed against BOSC-S and BOSC-R isolates. Concluding, ZnO-NPs are effective against A. alternata both alone or in mixtures with boscalid, and can be used as an effective, eco-compatible anti-resistance tool for reducing the environmental footprint of synthetic fungicides.
Dissolved organic matter characteristics and composition of small saline lakes in the Badain Jaran Desert, China
Authors: Zhang Qiang , Wang Yinghui , Zhang Xiaolang , Li Hailong , Jiao Jiu Jimmy , Fu Qinglong , Wang Junjian
Published: February 2023

Elucidating the characteristics and molecular composition of dissolved organic matter (DOM) is critical to understanding carbon cycling in increasingly saline lakes in arid and hyper-arid areas; however, the ages and molecular signatures of DOM in these widely distributed saline lakes remain poorly understood. Here, variations in DOM ages and other characteristics with salinity were investigated across 10 small saline lakes within the Badain Jaran Desert based on 14C-isotopic analysis, absorption and fluorescence spectroscopy, in addition to Fourier transform ion cyclotron resonance mass spectrometry. The results showed that brine lakes had dissolved organic carbon (DOC) levels 3-fold higher than brackish lakes, and the 14C age of DOC in brine lakes was twice as old. Compared to brackish lake DOM, brine lake DOM had more significant signatures of microbial contributions, as indicated by the higher fluorescence index values and greater relative abundances of microbial humic-like fluorescent components, in addition to sulfur-containing compounds. Moreover, brine lakes showed lower relative abundances of aromatic lignin-like components, as well as higher relative abundances of lipid- and condensed-aromatics-like components. Regarding halogen-containing DOM, the brine lakes showed higher abundances of halogen-containing lignin- and lipid-like components, supporting the preferential transformation of aromatic compounds into halogenated lignin- and lipid-like components. This study demonstrates the strong impacts of salinization on DOM aging, accumulation, and halogenation in inland saline lakes and highlights the critical role of brine lakes as a persistent carbon pool.
Undifferenced and uncombined GNSS approach for absolute and relative POD of LEO satellites in formation flying
Authors: El-Mowafy Prof  Ahmed
Published: February 2023

Low Earth orbit (LEO) satellites are widely used in space missions such as satellite gravimetry, radio occultation, Earth monitoring, and in formation flying. Precise orbit determination (POD), in either absolute or relative modes, is an essential prerequisite for these missions. The onboard collected signals of the global navigation satellite system (GNSS) are used for the POD of LEO satellites. Typically, the Ionosphere-free (IF) combination of these signals is used in the absolute LEO POD, which has some disadvantages. Firstly, the observation information is wasted in constructing IF observation. Secondly, although different IF combinations can be constructed in multi-frequency scenarios, they may be correlated. Thirdly, integer ambiguity resolution (IAR) based on the IF observations can only be achieved with precise external products, which has limited availability in space. Concerning relative POD, the most classical method is the double-differenced (DD) model with IAR, which also has drawbacks. Firstly, strict common-view GNSS satellites are needed, which is not guaranteed in the complex space environment with the high dynamic of the satellites. Secondly, the opportunity to impose dynamic constraints on the eliminated parameters is lost during differencing. Therefore, in this contribution, we focus on the use of undifferenced uncombined (UDUC) observations and propose a new POD model. The UDUC POD model has several advantages. Firstly, the common-view GNSS satellites are only used to form the DD ambiguities for IAR; therefore, there is no need for the external satellite phase bias (SPB) products. Secondly, the model shows flexibility in multi-frequency scenarios. Thirdly, and more importantly, as precise GNSS orbits and clocks products are used, the model can be used for both absolute and relative LEO POD. Based on onboard GPS observations of a formation flying mission, comprising two closely spaced LEO satellites working in a formation, we explored the performance improvement of the proposed model over traditional models. Two conclusions can be drawn. Firstly, the proposed model's performance in absolute POD is improved by more than 20% compared with the classical IF POD method, when computing their differences with reference orbits. Secondly, for relative POD, it is proposed that the consistency between the model and the reference orbit is within 1.5 mm, proving that the method can serve for formation flying missions. The above results show that the proposed UDUC POD method can achieve higher POD accuracy than the traditional methods.
Erosive rainfall clustering across Austria's agricultural areas
Authors: Vasquez Cristina , Klik Andreas , Stumpp Christine , Strauß Peter , Laaha Gregor , Özcelik Nur Banu , Georg Pistotnik , Dostal Tomas , Yin Shuiqing , Strohmeier Stefan
Published: February 2023

A few low-frequent but extreme rainfall events generate substantial erosion amounts and, as a result, land degradation negatively affects soil health and agricultural productivity. Determining rainfall erosivity (from small to extreme events) that drive soil erosion will improve our knowledge and understanding of extreme erosion processes and our ability to develop and adapt adequate soil protection strategies. This study aims to analyze rainfall erosivity characteristics across Austria‘s main agricultural production zones using long-term (from 27 to 82 years) with high-resolution (5-minutes) rainfall data from 27 rain gauges. Erosive rainfall characteristics such as rainfall amount, event duration, and the maximum 30-minute intensity were investigated, and typical rainfall types were assessed through a clustering approach based on the k-means algorithm. Results identified three dominant types (clusters) of erosive rainfalls across Austria's agricultural areas. Seasonal distribution analysis showed that the predominant erosive events, characterized by short duration and high intensities, occur during the summer months from June to August. In contrast, the long-duration and low rainfall-intensity events are evenly distributed throughout the year. The spatial distribution of rainfalls related to the largest rainfall erosivities showed a pronounced occurrence in the southeastern pre-alpine areas. Knowledge of the occurrence of erosive rainfall events in space and time eventually supports the implementation of locally adapted Soil Conservation (SC) practices in Austria.
Reconstructing climate fields with terrestrial climate archives, isotope-enabled GCMs and Data Assimilation
Authors: Choblet Mathurin A. , Bühler Janica C. , Steiger Nathan J. , Novello Valdir F. , Rehfeld Kira
Published: February 2023

Data Assimilation in paleoclimatology (PaleoDA) is a method that has been used in several climate reconstructions for the last millennium. By fusing information from both climate proxies and general circulation models (GCMs), PaleoDA provides statistical estimates of climate fields that are dynamically consistent. However, existing reconstructions mostly rely on calibrated tree ring data and assimilate proxy records on a single, annual time scale. Ice cores and speleothems, which record past variations in the oxygen isotope ratio of precipitation, often have a lower and irregular time resolution, but reliably record climate variations on decadal to centennial time scales. 

Here, we implemented a computationally efficient DA algorithm that enables the assimilation of proxy records on multiple timescales. The algorithm has been applied to speleothem and ice core records from the SISALv2 and Iso2k database and five isotope-enabled GCMs. Reconstructions of global mean temperature changes during the last millennium compare well in both amplitude and uncertainty to recent studies. The potential of incorporating speleothems is shown with a reconstruction of hydroclimatic changes in tropical South America, where speleothems represent the most abundant type of hydroclimate archive. The experiments performed suggest an increased reconstructed decadal to centennial variability by using proxy records on multiple timescales. Making use of different climate models shows the influence of model biases on the reconstructions. Future PaleoDA reconstructions could be improved from more proxy records and the multiple time scale approach to provide a globally complete picture of past climate changes. 
Global ground heat flux from remote sensing data: preliminary results and evaluation
Authors: Cuesta-Valero Francisco José , Peng Jian
Published: February 2023

Ground heat flux constitutes the conductive component of the surface energy budget. Quantifying this energy component is important to close the surface energy balance and to understand the energy exchanges between the lower atmosphere and the shallow subsurface. Furthermore, ground heat storage accounts for approximately 90 % of the continental heat storage, and 4-5 % of the total Earth heat storage. Therefore, monitoring changes in ground heat flux at global scale is of critical importance to quantify and understand the evolution of the Earth heat inventory, and thus climate change. However, the main sources of information about past and present ground heat flux are measurements of subsurface temperature profiles and micrometeorological observations, which are incomplete records biased towards northern extratropical latitudes.Here, we present preliminary estimates of global ground heat flux derived from remote sensing products from the European Space Agency (ESA) Climate Change Initiative (CCI). Estimates from four land surface temperature (LST) products (MODIS-Terra, MODIS-Aqua, ENVISAT-AATSR, and SSMI-SSMIS) are evaluated against FLUXNET observations, obtaining a range of root mean squared errors from 3.8 to 5.2 W m-2 at monthly resolution. Nevertheless, there are some spatial inconsistencies among estimates from different LST products, as well as in long-term trends during the period 2003-2013. Several factors affecting the estimated ground heat flux are analyzed, with soil water and land cover having the largest effect on the retrieved values. These results suggest that land surface temperature from satellite observations may be able to provide global long-term ground heat flux estimates, although some issues still need to be solved.
Assimilation of range-and-depth-averaged sound speed in Fram Strait
Authors: Geyer Florian , Gopalakrishnan Ganesh , Sagen Hanne , Cornuelle Bruce , Mazloff Matt , Challet Francois
Published: February 2023

Acoustic thermometry measurements of ocean sound speed were used to improve state estimates of ocean temperature in Fram Strait. This is the first time that large-scale acoustic measurements have been assimilated into an ocean model in the Arctic. From September 2010 to July 2012 the Acoustic Technology for Observing the Interior of the Arctic Ocean (ACOBAR) experiment measured acoustic travel times between Greenland and Spitsbergen. These acoustic tomography measurements were taken along 167-301 km long sections between 3 bottom-mounted moorings. The measurements were inverted to yield time series of range-and-depth-averaged ocean sound speed for 0-1000 m ocean depth.The ocean sound speed time series was assimilated into a regional numerical ocean model using the Massachusetts Institute of Technology General Circulation Model-Estimating the Circulation and Climate of the Ocean four-dimensional variational (MITgcm-ECCO 4DVAR) assimilation system. The data assimilation improved the range-and-depth-averaged ocean temperatures at the independent 78°50’N oceanographic mooring section in Fram Strait (0-1000 m depth). The RMS error of the ocean state estimate (0.21°C) was comparable to the uncertainty of the interpolated mooring section (0.23°C). The lack of depth information in the assimilated ocean sound speed measurements caused an increased temperature bias at shallow depths (0-200 m). The temporal correlations with the mooring section were not improved because short-term variations in the mooring measurements and the ocean state estimate did not coincide in time. This was likely due to the small-scale eddying and non-linearity of the ocean circulation in Fram Strait. Furthermore, the horizontal resolution of the state estimate (4.5 km) was eddy-permitting, rather than eddy resolving. Therefore, the state estimate could not represent the full ocean dynamics of the region. This study demonstrates the usefulness of large-scale acoustic measurements for improving ocean state estimates at high latitudes.
Synced deformation of the Talesh-Alborz-Kopet Dagh belt and formation of the Iranian Plateau
Authors: Chu Yang , Wan Bo , Chen Ling , Lin Wei , Talebian Morteza , Liang Xiaofeng , Zhao Liang
Published: February 2023

Plate convergence has continued for over 25 Myr after the Arabia initially collided with the Eurasia, causing vast intracontinental deformation within the Central Iran Block at the southern margin of the Eurasia. During the same period, the Iranian Plateau grew as tectonic stress from continental collision propagated northwards, accompanied by strong deformation, crustal shortening and rapid rock exhumation, but the process of the plateau formation remains less discussed. From west to east, the Talesh-Alborz-Kopet Dagh (TAK) situates at the northern front of the Iranian Plateau and suffers intense folding and thrusting that creates the highest mountain range in Iran, so its tectonic evolution history carries important clues for the building of the current plateau.To better constrain the spatial and temporal patterns of deformation and exhumation, we carried out comprehensive structural analysis and new geochronology-thermochronology dating for the TAK. As a first order feature of the collision zone, the TAK records an immediate response to the initial collision. Oligocene deformation is well documented but unevenly exhumed different segments of the belt along-strike. The Talesh and westernmost Alborz preserves late Neoproterozoic basement rocks (~570 Ma) and old, Mesozoic zircon U-Th/He ages (150-90 Ma), acting as a relatively rigid part resistant to Oligocene deformation. In contrast, the main part of Alborz was remarkedly shortened by folds and thrusts and exhumed rapidly, while the Kopet Dagh shows a simply folded belt dominated by box folds in deca-kilometer scale. All the TAK experienced enhanced exhumation since 20 Ma, peaked at the Late Miocene, suggesting the deformation was synced around 7 Ma when the internal tectonic organization along the belt and within the Central Iran Block had been much reduced. This Late Miocene switch reflects a reorganization of Arabia-Eurasia plate convergence. The causes could include that elevation increased to a level at which the Iranian Plateau was built and resisted further thickening, or internal heterogeneity was decreased and the whole region began to evolve as a single tectonic unit, causing deformation to be accommodated in other regions. The growth model of Iranian Plateau can also enlighten us on how Tibetan Plateau developed and expanded at its early stage.
CO2-driven granular flows as erosional forces on present-day Mars
Authors: Roelofs Lonneke , Merrison Jonathan , Conway Susan , de Haas Tjallng
Published: February 2023

Martian gullies are alcove-channel-fan systems which have been hypothesized to be formed by the action of liquid water and brines, the effects of sublimating CO2 ice or a combination of these processes. Recent activity and new flow deposits in these systems have shifted the leading hypothesis from water-based flows to CO2-driven flows. This shift in thinking is supported by the low availability of atmospheric water under present Martian conditions and the observation that gully activity occurs at times when CO2 ice is present. We recently performed novel experiments that have shown that this hypothesis holds; sediment can be mobilized and fluidized by sublimating CO2 ice under Martian atmospheric pressure. However, if these flows are able to erode the underlying surface and can explain the formation of Martian gully systems over the long term remains unknown. Therefore, we present an additional series of experiments that test the capacity of CO2-driven granular flows under Martian atmospheric conditions to erode sediment. These experiments were conducted in a 4 m long flume in the Aarhus Mars Simulation Wind Tunnel. Our experiments show that CO2-driven granular flows can erode loose sediment under a range of different slopes and CO2-ice fractions. The results also show that incorporation of warmer sediment increases fluidization of the mixture, reflected by an increase in gas pore pressure in the flow. These results thus prove that morphological evolution in the gully systems on Mars can be explained by CO2-driven granular flows.
Sometimes size matters – new insights into the physical disintegration of biochar
Authors: Sigmund Gabriel , Schmid Andrea , Schmidt Hans-Peter , Hagemann Nikolas , Bucheli Thomas D. , Hofmann Thilo
Published: February 2023

It is often assumed that the physical disintegration of biochar determines its persistence and mobility in soil. Freeze-thawing can cause physical stress on biochar, breaking it down into smaller and presumably more reactive particles. We here investigated the physical decay and subsequent mobilisation of five different biochars under "realistic worst-case scenarios" in a laboratory sand column setup, in shaking as well as in sonication experiments. Mobilisation of carbon from biochar particles (0.25 - 1 mm) was studied in a sand column (pH 6.3, with and without 80 freeze-thaw cycles). Small biochar particles did not disintegrate much after the freeze-thawing, possibly due to freezing point depression in biochar micropores. Freeze-thaw-induced physical decay of biochar is a process that is more pronounced in large biochar particles with substantial meso- and macropores, based on our results compared to literature data. Biochar with larger ash fractions disintegrated more, presumably due to the formation of unstable voids within the biochar associated with ash pockets. The physical stability of biochars produced from the same feedstock at different pyrolysis temperatures decreased with increasing aromaticity, which could be related to higher stiffness of the more aromatic structures. Soil moisture content increased carbon mobilisation from biochar more than physical stresses such as freeze-thawing. The physical disintegration of biochar and subsequent mobilisation of micro- and nanoscale carbon should therefore be considered less important and in many cases is not expected to be a decisive factor for the stability of biochar in soil.
Erosion regime controls sediment eDNA-based community reconstruction
Authors: Morlock Marina A. , Rodriguez-Martinez Saúl , Huang Doreen Yu-Tuan , Klaminder Jonatan
Published: February 2023

Environmental DNA (eDNA) analysis from lake sediments shows promise to become a great paleoecological technique. Nevertheless, our knowledge regarding catchment processes that influence the eDNA signal preserved in sediments creates uncertainties when interpreting temporal changes in reconstructed biodiversity. Are changes in species composition the result of ‘real’ changes in species abundances or simply the result of altered DNA transport processes in the catchment?In this presentation, we investigate the role of erosion for sediment eDNA-based reconstructions. We utilize sediment records from the Central Alps and compare the plant and mammal DNA pools in lake sediments of similar age but deposited under different erosion regimes: detrital event layers formed during heavy precipitation events vs. hemi-pelagic background sedimentation.We find strong differences in the reconstructed plant and mammal communities both across space and time. Temporal changes across the Holocene were the main drivers of change for reconstructed plant communities, but sediment type -and thus erosion regime- was the second most important factor of variance. Around 30% of all plant and mammal taxa were uniquely detected in event layers. Our results highlight that the two sediment types preserved their unique assembly of plant and animal DNA, suggesting that post-depositional mobility of terrestrial DNA is insignificant on Holocene timescales. However, our results also highlight the challenge when attributing changes in erosion regimes to the appearance of new species in an eDNA-based paleo-record because increased erosion will also increase the representation of taxa already present in the lake’s catchment. In our case, this mechanism was an important factor for DNA-inferred species composition and taxonomic richness recorded in the sediments.
Seasonality and distribution of Persian Gulf Water and its impact on ventilation: a high resolution view from gliders
Authors: Font Estel , Y. Queste Bastien , Swart Sebastiaan , Bruss Gerd
Published: February 2023

The decline in ocean oxygen content is one of the most alarming consequences of anthropogenic-driven climate change. A key challenge is that global climate models do not currently reproduce observed changes in deoxygenation, showing high inter-model variability and uncertainty. This uncertainty is partially due to the models’ inability to resolve features smaller than their computational grid cells resulting in large biases in ventilation. The Persian Gulf Water outflow has been pointed out by several studies as one of the sources of ventilation in the Arabian Sea Oxygen Minimum Zone (OMZ). This oxygenated water mass flows eastward along the shelf edge of the northern Omani coast at 200m depth and is fragmented by the mesoscale eddy field and rough topography, generating small “peddies”. These peddies and their relatively high oxygen concentrations have potential to ventilate the OMZ, yet this has been poorly investigated due to a lack of adequate observations. We use multi-month glider campaigns off the coast of Oman with a SeaExplorer glider equipped with an ADCP to resolve the contribution of the Persian Gulf Water outflow to oxygen supply within the Arabian Sea OMZ. We characterize its properties, seasonality, and spatial distribution and estimate mixing rates from double diffusion, salt-fingering, and shear-driven mixing to understand water mass transformations and oxygen fluxes into the OMZ.
Dust storm statistics based on the EMM camera EXI for a complete Martian Year period
Authors: Guha Bijay Kumar , Gebhardt Claus , Young Roland M. B. , Wolff Michael J.
Published: February 2023

Abstract: The Emirates eXploration Imager (EXI) onboard EMM is a multi-wavelength double lens camera suitable for observing the Martian lower atmospheric phenomena such as dust storms [3, 5]. The spacecraft’s unique orbit allows the EXI camera a full disk view of Mars at a time step of hours or less through its visible and UV channels (at ~2-4 km per pixel resolution). Therefore, we have used these unprecedented observations to characterize the dust storms for a one Martian-year period [4, 6]. Our dust storm research is directly aligned with the EMM science objective on the lower atmosphere and also with the objective of correlating the lower and upper atmosphere [1, 2]. In this study, we have prepared a one Martian year of dust storm database from EMM-EXI images. The dust storm database includes the start and end time of dust storms, their area, and the centroid latitude and longitude. Here, we also focused on characterizing the dust storms at a sub-daily time scale (which has not been emphasized before) by tracking their evolution at multiple local times. In addition, we consider the origination region, the pathway, and the morphological characteristics of dust storms. Our presentation includes accompanying simulations by a planetary climate model.References: [1] Almatroushi, H., et al. (2021). Space Science Reviews, 217(8), 1-31. [2] Amiri, H. E. S., et al. (2022). Space Science Reviews, 218, 4 (2022). [3] Gebhardt, C., et al. (2022). Geophysical Research Letters. 49, e2022GL099528. [4] Guha, B. K., et al. (2021). Planetary and Space Science, 209, 105357. [5] Jones, A.R., et al. (2021). Space Science Reviews, 217, 81. [6] Wang, H., & Richardson, M. I. (2015). Icarus, 251, 112-127.
Chemical characterization of urban waters aimed for managed aquifer recharge in the Hesbaye chalk aquifer (Liège, Belgium)
Authors: Glaude Robin , Simon Nataline , Orban Philippe , Brouyère Serge
Published: February 2023

Managed Aquifer Recharge (MAR) is a viable method that has gained recognition for storing alternative waters in aquifers for subsequent recovery or environmental benefits. It has the potential to increase the supply of fresh water and protect aquifers from overexploitation and degradation, but it might also carry the risk of contaminating groundwater since the recharge water used may contain a wide range of organic and inorganic contaminants. Therefore, it is important to carefully assess the quality of these alternative sources of water (such as runoff water) used for MAR and implement appropriate treatment measures to remove or neutralize any contaminants that may be present. The purpose of this research is to conduct a preliminary feasibility study of MAR as a potential mitigation measure in the Hesbaye chalk aquifer since this major source of drinking water for the region of Liège (Belgium) is threatened both in terms of quantity and quality. In the first phase of the study, the quality of runoff waters collected from stormwater basins along national roads and in a national airport area was analysed and certain contaminants of emerging concerns were detected at concentrations close to drinking water limits or environmental safety guidelines. In particular, contaminations with PFAS compounds have been detected in stormwater basins in the airport area with maximum values reaching up 490, 330 and 250 ng/L for PFECHS, PFPeA and 6:2 FTS respectively. Other contaminants of emerging concerns such as alkylphenols and organophosphate flame retardants have been detected as well. In a second phase, estimates of expected recharge rates were determined through in-situ experimentation using a small infiltration pond with a pressure sensor and innovative active-DTS measurements with buried optical fiber cables to monitor the infiltration of water into the loess (eolian loam) sediments overlaying the Hesbaye chalk aquifer. Finally, these input data have been used to perform 1D transport modelling simulations in order to make a preliminary evaluation of the risk of groundwater deterioration in the case where these raw runoff waters are infiltrated without pre-treatment. Column infiltration tests are planned to get a better estimation of the soil attenuation capacity in the unsaturated zone. This study is unique in that i) it explores the feasibility of MAR in a country in which the method is not well-developed yet, ii) the use of airport runoff water as a potential source of recharge water is novel and has not been widely examined in previous MAR studies and iii) aquifer-soil treatment in loess sediments overlaying a chalky fractured aquifer is a unique hydrogeological setting to perform MAR operations.
Precipitation extremes in the Ukraine: dynamical aspects, large-scale circulation and moisture sources
Authors: Agayar Ellina
Published: February 2023

Abstract EGU General Meeting – April 2023 Abstract for session CL2.9: Atmospheric circulation in different spatial scales as one of the main climate variability factor Precipitation extremes in the Ukraine: dynamical aspects, large-scale circulation and moisture sources Ellina Agayar1,2, Franziska Aemisegger1, Moshe Armon1, Alexander Scherrmann1, and Heini Wernli1 1Institute for Atmospheric and Climate Science, ETH Zürich, Zürich, Switzerland2Odessa State Environmental University, Odessa, Ukraine   Changes in the occurrence of large-scale circulation regimes link with changes in the global and regional climate and affect the frequency of occurrence and intensity of weather extremes, including extreme precipitation events (EPE). Understanding such natural hazards and their drivers is essential to mitigate related risks. In specific regions of the Ukraine, especially the Ukrainian Carpathians and the Crimean Mountains, precipitation can last for several days leading to floods. In this study, we investigate the dynamics of EPEs (≥ 100 mm day-1) over the territory of Ukraine in the recent decades (1979-2019). The EPEs are identified based on precipitation observations from 215 meteorological stations and posts in Ukraine. The atmospheric parameters for the categorization of the weather types (WTs) associated with the EPEs, as well as for composite studies and trajectory calculations were taken from ERA5 reanalyses. The identification of moisture sources contributing to extreme precipitation in Ukraine is based on the computation of kinematic backward trajectories and the subsequent application of a moisture source identification scheme based in the humidity mass budget along these trajectories.By analysing the large-scale atmospheric circulation from reanalysis products, a four-class weather type (WT) classification of days with extreme precipitations in Ukraine is performed. The largest values of precipitation and greatest likelihood of EPEs occur in the WTs “Southerly cyclones and troughs” (45.1%) and “Easterly and South-Easterly cyclones and troughs” (23.2 %). The resulting WTs are assessed in terms of frequency of occurrence, seasonality, thermodynamic structure, and the spatial pattern of the large-scale flow, which allow identifying the main mechanisms for the formation of EPEs over Ukraine. Results show a clear spatial division in EPE occurrence, with summer and autumn being the seasons of highest EPE frequency in the western, south-western and eastern Ukraine. The last part of this study is dedicated to defining the origin, uptake characteristics, and transport pathways of moisture that precipitates during EPEs in Ukraine. 