bluuebunny/crossref_metadata_2025 huggingface dataset:
How much is too much? The effect of embolism on drought survival and recovery of an evergreen broadleaf
Authors: Wagner Yael , Volkov Mila , Hochberg Uri , Klein Tamir
Published: March 2024

Xylem embolism impairs hydraulic conductivity in trees and drives drought-induced mortality. Research shows that trees can endure high levels of embolism, but quantifying the amount of embolism which kills a tree is difficult. Specifically, re-sprouting woody species, pose a challenge, since even determining mortality is not straight forward. This calls for a long-term monitoring of post-drought recovery, and raises the question – while trees can prevail with high levels of embolism, how is their recovery affected?
 
To answer these questions, we exposed Carob saplings (Ceratonia siliqua), a species with high resistance to embolism, to different levels of drought, and monitored them at the peak of drought as well as during one and six months of recovery. The saplings were scanned using a micro-computed tomography (μCT) and embolism levels, as well as its radial distribution within the xylem, were analyzed. Physiological recovery was examined by monitoring stomatal conductance (gs); number of leaves and their vitality; number of bud-bursts and stem growth.
 
Almost half of the saplings died during the experiment (88 out of 200). The ‘lethal dose’ (LD50; the level of embolism that killed 50% of the trees) was 38% for the stem xylem. LD50 was significantly lower for the outer, younger part of the xylem (i.e. closer to the cambium; 25%) compared to the inner, older part (i.e. further away from the cambium; 38%), with no significant difference between LD50 of the outer and the whole xylem. Physiological parameters were strongly reduced by embolism levels measured at the peak of drought for at least six months following rehydration.
 
Our results show that high resistance to embolism doesn’t necessarily mean high tolerance, and perhaps even the opposite. We found that embolism level sustained during drought is a better predictor than Ψx for the ability of plants to recovery physiological activity once drought has ended. The similarity between LD50 of the whole xylem and the one of the inner xylem, (i.e. furthest from the cambium) suggests that the proximity of embolism to the cambium doesn’t affect its lethality. Meaning, an embolism in an inner, older conduit seems to be just as deadly as an embolism in a younger one, and while trees that died had higher embolism levels in inner- compared to outer-xylem, it did not drive the whole-xylem LD50. Finally, trees that had survived drought were not able to fully recover, even six months into rehydration, raising a question of drought legacy and their ability to prevail the next drought episode. Understanding the physiological implication of drought-induced embolism is necessary in order to preserve and restore forests in a hotter, drier world.
Geothermal Reservoir Deformation Monitoring Based on Coda Wave Interferometry
Authors: Wang Yunliang , Azzola Jérôme , Zigone Dimitri , Lengliné Olivier , Magnenet Vincent , Vergne Jérôme , Schmittbuhl Jean
Published: March 2024

Monitoring of geothermal reservoir deformation is essential for the normal development of the Enhanced geothermal system (EGS). Coda wave interferometry (CWI) with ambient noise is regarded as an effective and low-cost monitoring technique and draws more and more attentions. But the connection between the obtained CWI measurements and the undergoing physical changes of deep reservoir is still not so clear. In this study, we take Rittershoffen geothermal system (France) as a case study and conduct a series of forward simulations regarding the propagation of scattered wavefield through the deformed model considering acoustic-elastic effect based on Code_ASTER (mechanical loading) and SPECFEM2D (wave propagation). The simulations are based on a two dimensional numerical model with a scale of 12km (width)×20km (height), in which the upper reservoir model contains 8 layers to mimic Rittershoffen geothermal reservoir, the lower sub model with multiple circular inclusions is set to scatter the waves emitted from point source at bottom and produce scattered wavefield; two seismic stations are located at the top of the model. The model is first verified by reproducing the seasonal variation of relative wave velocity changes obtained from ambient noise cross-correlation functions (ANCCF) induced by the underground water table elevation changes. Based on the validated model, we study the effect of in-situ reservoir deformation on CWI measurements by modelling the hydraulic pressure increases on an open hole and the aseismic slip of an embedded fault which is based on the case of hydraulic injection of GRT-1 well, Rittershoffen. The result indicates the induced small reservoir deformation in both situations can be detected by CWI measurements, which helps us to have a better understanding about the connection between the obtained CWI measurements and the undergoing deformation of deep geothermal reservoir.
A New Model for Predicting Hydraulic Conductivity of Soil during Freeze-thaw Processes that Accounts for Both Capillary and Adsorption Forces
Authors: Qiao Shufeng
Published: March 2024

Understanding the change of soil hydraulic conductivity with temperature is a key to predicting the groundwater flow and solute transport in permafrost and seasonally frozen area. The most commonly used models for hydraulic conductivity during freeze-thaw cycles only consider the flow of capillary water in the soil and neglect water flowing along thin films around the particle surface. This paper proposed a new hydraulic conductivity model of frozen soil via Clausius-Clapeyron equation based on an unsaturated soil hydraulic conductivity model over the entire moisture range using analogy between freeze-thaw and dry-wet process in soils. The new model used a simple single equation to describe the conductivity behaviors resulting from both capillary and adsorption forces, thus accounting for effect of both capillary water and thin liquid film around soil. By comparing with other existing models, the results demonstrated that the new model is applicable to various types of soils and the predicted hydraulic conductivity is in the highest agreement with the observed data. Finally, our new model was validated with a thermal-hydrological benchmark problem and a laboratory experiment result, and the benchmark results indicated that the advective heat transfer was more significant and the phase change completed earlier when considering both capillary and adsorption forces than that only considering capillary forces. Further, the coupled flow-heat model with the FXW-frozen-M2 replicate well the results from a laboratory column experiment.
Identifying the source areas of subsurface stormflow through the analysis of depth profiles of water-soluble organic matter
Authors: Chifflard Peter , Fasching Christina , Schadewell Yvonne , Leese Florian
Published: March 2024

The hydrological dynamics of hillslopes, particularly subsurface stormflow (SSF), exhibit intricate variability in space and time. Existing studies are often confined to single slopes or limited storm events, resulting in uncertainties when applying findings to other slopes or catchments. To address this, a comprehensive understanding of hillslope hydrological dynamics and factors influencing spatial and temporal SSF patterns is essential for upscaling and model validation. Linked to hillslope hydrology is the export of organic carbon to streams, yet spatial carbon sources remain unclear due to limited knowledge of SSF flow paths within slopes.We propose a hydro-biogeochemical approach, measuring water-soluble organic matter (WSOM; concentration, absorbance, and fluorescence) at 480 locations across 100 hillslopes in four contrasting catchments (Sauerland, Ore Mountains, Black Forest, Alps). This approach aims to establish empirical relationships between landforms, bedrock, and soil properties, quantifying spatial variability and stability of subsurface hydrological processes (e.g., flow directions, transit times, hydrochemical and biochemical composition).Distributed sampling of WSOM along soil profiles (6 samples per profile) will assess vertical and lateral subsurface flow paths in unsaturated and saturated zones, aiding spatial discretization of SSF source areas.Preliminary results will provide depth profiles of WSOM in the four catchments spanning low to high mountain ranges (Sauerland, Ore Mountains, Black Forest, Alps), facilitating the detection of SSF source areas.
Triple sulfur isotope constraints on the sulfur cycling in Lake Sevan, Armenia
Authors: Kamyshny Alexey , Avetisyan Khoren , Mirzoyan Natella , Payne Rayford
Published: March 2024

Lake Sevan is a meso-eutrophic water body, which was severely impacted by anthropogenic level decrease, pollution and eutrophication during the last century. Starting in the 1970s, a decrease in the water level and an increase in dissolved inorganic nitrogen concentrations resulted in oxygen depletion in the hypolimnion of the lake during summer–autumn thermal stratification of the water column. Our work shows that in October 2019, the redox conditions in the hypolimnion progressed not only to full depletion of oxygen and nitrate, but to the formation of a hydrogen sulfide-rich deep-water layer, which covers 66% of lake’s bottom and accounts for 19% of its water volume. Concentrations of hydrogen sulfide in the hypolimnion of Major and Minor Sevan in October were as high as 9 and 39 μM, respectively.Triple sulfur isotope composition of sulfate and hydrogen sulfide in the water column of the lake provides further constraints on the biogeochemical processes which result in the formation of hydrogen-sulfide hypolimnion. Values of δ34S for hypolimnetic sulfide are lower by only 7–12 ‰ compared to epilimnetic sulfate, while δ33S values of sulfide are similar to the δ33S values of sulfate. These isotopic fingerprints are not consistent either with microbial sulfate reduction in the water column or with its combination with re-oxidative sulfur cycle as the sources of hydrogen sulfide in the hypolimnion. We attribute the formation of a sulfidic deep-water layer to a combination of microbial sulfate reduction in the water column and diffusion of hydrogen sulfide from the sediments.
Imaging the Crustal structure of Oman and the United Arab Emirates using  Seismic Noise Autocorrelation functions
Authors: Yaqoob Muhammad , Pillia Simone
Published: March 2024

The United Arab Emirates (UAE) and Oman are primarily characterized by an orogenic belt housing the well-known obduted Semail ophiolite and a number of foreland basins. The thickness of the sedimentary basins in the region remains elusive and challenging to determine, given the substantial sedimentary cover that potentially exceeds 10 km. This thickness limits traditional techniques, hindering their ability to reach greater depths. Constraining the depth of the Semail ophiolite is an additional challenge because the high velocities of oceanic lithospheric units prevent geophysical techniques from imagining the base of the ophiolite with clarity.
Seismic noise autocorrelation proves to be an effective method for imaging subsurface structures owing to its independence from active seismic sources and its potential to reach greater depths. We used continuous seismic noise records from regional networks. Data were collected from 110 stations deployed across the mountain belt and adjacent sedimentary basins. Each station consisted of an average of one year of continuous records of passive seismic data. Data processing to obtain autocorrelation functions includes bandpass filtering and noise reduction to isolate the appropriate frequency range that is essential for imaging subsurface structures. Autocorrelation was performed on hourly files, and the phase-weighted stacking technique was applied to extract coherent signals from background seismic noise. We subsequently removed the common source function, which provides a final autocorrelation function over the two-way travel time. A 3-D velocity model of the region based on ambient noise tomography was used to convert the autocorrelations to a depth reflectivity profile beneath each station. The results were integrated with existing geophysical, geological, and well data and interpreted in terms of sedimentary basin and ophiolite thickness.
Global natural catchment classification based on hydrological similarity
Authors: Xu Huan , Wang Hao , Liu Pan , Liu Weibo , Zhou Chutian
Published: March 2024

Catchments are important in hydrology, and a catchment classification framework helps to understand the catchment hydrological behaviors, explain the differences between catchments, and predict in ungauged catchments. However, no research has yet established a global catchment classification framework.We selected a group of hydrological signatures to represent catchment hydrological behaviors, and used the fuzzy clustering method to classify natural catchments. To explain the classification rules and the catchment attributes dominating the classification, we used decision tree and random forests, respectively. The results show that: the global natural catchments are divided into six classes by the fuzzy clustering method, most of the classes are extreme in at least one hydrological behavior, and the selected hydrological signatures can distinguish the catchment groups; The decision tree gives explicit classification rules, with an accuracy rate of over 93%, which reasonably explains the fuzzy clustering results and facilitates the judgment of catchment classes; The precipitation characteristics, aridity index and the lowest altitude of catchments are considered to be the dominant catchment attributes for catchment classification, among which the average daily precipitation is the most important; Compared with physiography, land cover, soil and geological factors, the relative importance of climate factors in catchment classification exceeds 50%; The global catchment classification pattern output by random forests is a comprehensive reflection of hydrological signatures and can better reflect the hierarchical differences in hydrological behavior among catchments in contrast to climate classification.The validity of the proposed global classification pattern is supported by its consistency with regional studies conducted in Europe, the United States, and Australia. Furthermore, about 64.1% classification accuracy of catchment class and 62.0% simultaneous hit rates of eight hydrological signatures can be achieved by the random forests model, demonstrating the ability of proposed catchment classification in estimating the hydrological behavior of ungauged catchments. As the first step towards global catchment classification, this study developed a natural catchment classification method based on hydrological similarity using data-driven approaches, obtained a global distribution map, and laid the foundation for establishing a generally accepted global catchment classification framework.
Global to regional Holocene climate changes and events recorded in a near-slope deep sea brine-pool sediments of the NE Red Sea
Authors: Petrovic Alexander , Lakrani Prabodah , Vahrenkamp Volker
Published: March 2024

Marine climate archives in Red Sea sediments have the great potential to improve our understanding of mankind’s dispersal out of Africa. However, cores from deep sea sediments are often greatly disturbed by bioturbation reducing the resolution of recorded climate events. We report geochemical and geophysical data from a 244 cm long sediment core collected from a recently discovered deep sea brine pool near the Arabian slope and the Al Wajh carbonate platform. The analysis of the high-resolution climate archive preserved in the undisturbed sediments of the brine pool provide excellent correlations to numerous known historical events in the last 6.5 ka, and indicate the great potential of brine pool sediments to provide further insights into climate changes and human civilization development within the African-Arabian dessert belt.The recovered marine sediment core from a brine pool was therefore investigated to test its reliability for in-depth Holocene climate studies. The brine-filled depression (>190 PSU; 25 m thick) is located 25 km south of the Al Wajh carbonate platform in 640 m water depths. It is bounded by a salt extrusion in the northwest and a steep shallow water reef in the east. The undisturbed dark-olive coloured sediment succession are carbonate-dominated, devoid of bioturbation, and rich in TOC indicating an anoxic environment. The established stratigraphy via five radiocarbon dates of (planktic foraminifera. T.sacculifer and O. universa) resulted in high sedimentation rates ranging from 30.22 to 50.6 cm/ka. The integration of geochemical (e.g., isotope data, XRF) and geophysical data (e.g., magnetic susceptibility, spectrophotometer reflectance) revealed the recording of dozens of prominent climate periods (e.g., Roman Climate Optimum, Little Ice Age), changes (e.g., Mid-Holocene Highstand), and historical events (e.g., collapse of Late Uruk and Akkadian Empire) since the Mid-Holocene. In addition, the data analyses suggest that even periods of increased ENSO activity are recorded within the brine pool sediments of the Red Sea.The outcome of this study highlights the potential of anoxic brine pool sediments as a unique and important high-resolution climate archive and the urgent need to further in-depth studies.
Morphometry of the Aspidolithus group in the lower Campanian at the Loibichl section (Austrian Eastern Alps). Comparison with palaeoenvironmental proxies.
Authors: Granero Ordóñez Paula , Wierzbicki Adam , Wagreich Michael
Published: March 2024

A morphometric analysis of the Aspidolithus group was carried out on samples from the lower Campanian of Loibichl (Rhenodanubian Flysch Zone in the Austrian Eastern Alps). Semi-quantitative analysis of the nannofossil assemblages was used to calculate palaeoenvironmental indexes. In addition, 1021 specimens of the Aspidolithus group with a good state of preservation were considered for measurement of different key parameters: (1) the maximum length of the coccolith (L); (2) the maximum width of the coccolith (W); (3) the width of the outer rim versus the small diameter of the central area (b/a); and (4) the number and arrangement of perforations in the central area. The aim of this study is to observe if there are significant differences between Aspidolithus morphotypes and to explore if there are any relationships that may control the size variation of this group. Furthermore, we analyzed the CaCO3 composition and the stable isotope ratios of δ13C and δ18O in order to assist in the interpretation of stratigraphy and palaeoecology. This study revealed the presence of five morphotypes: A. enormis subsp. 1, A. enormis subsp. 2, A. parcus expansus, A. parcus parcus, and A. parcus constrictus. The morphometric analysis provided evidence of a significant taxonomic differentiation between "small" morphotypes (with a length of < 8–8.5µm; identified as A. enormis or "small" A. parcus according to Gardin et al. (2001)) and the "large" A. parcus group (with a length of ≥ 8–8.5µm). The observations revealed a slight increase in the overall dimensions, a decrease in the size of the central area, and a general reduction in the number of perforations. Nevertheless, our research did not uncover clear patterns that facilitate the natural categorization of "subspecies" (parcus expansus, parcus parcus, and parcus constrictus) within the A. parcus group. Our statistical study indicates a possible correlation between the size variation of the Aspidolithus group and the different paleoenvironmental proxies, suggesting that they may reflect palaeoecological changes.Additional research is required to confirm the impact of size variation. This can be achieved through a comparative analysis that includes more material from the Santonian–Campanian boundary. An in-depth investigation of the impact of global vs. regional environmental elements is essential for comprehending these results.Gardin, S., et al. 2001. Developments in Palaeontology and Stratigraphy 19, 745–757.
Regional differences in thunderstorm intensity driven by monsoon and westerlies over the Tibetan Plateau
Authors: Wei Lei , Qie Xiushu , Sun Zhuling , Xu Chen
Published: March 2024

Thunderstorms are weak but frequent, and exhibit unique charge structures over the Tibetan Plateau (TP) where the average elevation is higher than 4 km. In this study, all detected thunderstorms over the TP between 1998 and 2013 by TRMM were divided into four intensity categories: weak, median, severe and extreme. This classification was based on the 75%, 90%, and 99% values of flash rate, maximum 40 dBZ height, minimum 85 GHz polarization-corrected temperature (PCT), and minimum 37 GHz PCT, respectively. The monthly distributions of thunderstorm intensity show that all categories mostly occur in summer over most regions of the TP, and in spring near the Himalayas. Although the peaks of thunderstorms occur during 1300-1600 LT, the thunderstorms occurring in the early morning and evening have a high probability of developing into severe and extreme thunderstorms. This is distinct from the thunderstorms over the Sichuan Basin, the surrounding areas, and the middle and lower reaches of the Yangtze River at the same latitude. On the basis of westerlies- and monsoon-dominated regions, as well as the altitude, the TP was divided into four regions: the eastern, northern, southern and western regions of the TP (namely ETP, NTP, STP and WTP, respectively). The ETP and STP are primarily influenced by the monsoon, with the ETP at a lower altitude than the STP. Conversely, the WTP and NTP are affected by the westerlies, with the WTP situated at a higher altitude than the NTP. Thunderstorms over the ETP are more likely to be severe and extreme than those over the NTP. The percentage of weak thunderstorms is highest over the WTP. It is found that the maximum top height, development depth, horizontal development area, and development volume at 20 dBZ, 30 dBZ, and 40 dBZ echoes are largest over the ETP, followed by the NTP and STP, while being smallest over the WTP. The results imply that thunderstorms influenced by the monsoon are larger and more likely to be severe and extreme than those influenced by the westerlies.
Diagnosis of Nitrogen Nutrition in Summer Maize based on Simulated Multispectral Data
Authors: liu lu
Published: March 2024

Developing technology for monitoring nitrogen in the canopy of summer maize, particularly selecting sensitive monitoring wavelengths and establishing appropriate monitoring models, is beneficial for promoting the application of non-destructive monitoring of nitrogen concentration and accurate management of water and fertilizer based on hyperspectral technology in large-scale areas. The study was carried out in Daxing Experimental Research Base of Beijing Engineering and Technology Research Center of State Water-Saving Irrigation from June to September in 2017 and 2018. It focused on summer maize and involved small-scale lysimeter experiments and field plot trials. In view of the fact that the hand-held ground spectrometer can only observe the hyperspectral reflectance of crops within a small area over a certain period of time, this study used measured hyperspectral information of summer maize canopy to simulate the spectral reflectance of Landsat 8-OLI and GF-1 satellite sensors using sensor spectral response functions for large-scale observations. Based on sensitive wide-band and multi-band spectral indices, a model for estimating canopy nitrogen content was constructed, providing a theoretical basis for using satellite multispectral data for nitrogen diagnosis in summer maize. The results suggest that the prediction models constructed based on the reciprocal of simulated spectral reflectance in the red light band (1/R) and the reflectance at the center wavelength of 864 nm in the near-infrared band are suitable for estimating the canopy nitrogen content of summer maize throughout the growing season, and the determination coefficients of the models reach 0.621 and 0.613, respectively. A fitting model was constructed based on principal component analysis using 10 multi-band spectral indices calculated from simulated multispectral reflectance of summer maize throughout the growing season and the model achieved a determination coefficient of 0.692, indicating a high level of simulation accuracy.
Seasonal Prediction of China's Overall Ozone Pollution
Authors: Chen Yuan , Zhang Yongwen
Published: March 2024

Ozone pollution is gradually emerging as the biggest obstacle to improving air quality in China, causing severe harm to human health and the natural environment. However, the future trend of China's overall ozone pollution remains poorly understood and the impact of global sea surface temperature anomalies (SSTA) on the long-term predictability of surface ozone in China remains a challenge. In this study, we use eigenanalysis emerges to effectively characterize dominant surface ozone pattern in China and establish cross-correlations between it and global SSTA time series. In summer, the daily maximum 8-hour average (MDA8) ozone anomaly in June-July-August (JJA) is mainly regulated by the West Pacific Subtropical High and the North Pacific High. In winter, the climate patterns related to the MDA8 ozone anomaly in December-January-February (DJF) are affected by the North Atlantic Oscillation ， the Madden-Julian Oscillation and others. We propose a multivariate regression model capable of predicting surface ozone patterns at least three months in advance. Our model's evaluation, using a testing dataset, shows an R-squared value of around 0.5 between predicted and observed data, surpassing the statistical significance threshold. This suggests the feasibility and potential applicability of our predictive model for forecasting and mitigating surface ozone in China.
Record-breaking marine heatwave in northern Yellow Sea during summer 2018: characteristics, drivers and ecological impact
Authors: Li Yan , Mu Lin , Niu Qianru
Published: March 2024

Globally, marine heatwaves (MHWs) are becoming more common, more intense, and longer-lasting. They could have a large ecological and societal impact when compounded by low oxygen concentrations or high acidity. Here, using a high-resolution satellite product and reanalysis datasets, we investigated the characteristics of the MHW at northern Yellow Sea (NYS) during mid-summer 2018 and the driving mechanisms of large-scale atmospheric circulations. Results showed that the MHW in mid-summer 2018 (lasting from 26 July to 18 August 2018) had been the most intense since 1982, reaching an anomaly peak of 5.15 °C. For the 2018 MHW, the onset rate was 0.49 °C/day, indicating that the reaction window was relatively short and hard to take mitigation measures, while the decline rate was 0.19 °C/day, meaning the coping window was long and easy to push an already stressed system. The synergy of the two large-scale dynamic systems, i.e., the northward-shifted western north Pacific subtropical high (WNPSH) and the northeastward-expanded South Asia high (SAH), was likely responsible for establishment and maintenance of the hot-weather conditions. These high-pressure systems could result in stronger descending motion, less cloud cover, more solar radiation, and smaller wind speeds which in combination aggravated the MHW. We further found that the unprecedented MHW was actually also impacted by terrestrial heatwave. From 14 July to 15 August 2018, Northeast China was affected by an exceptionally long and intense atmospheric heat wave (AHW). The AHW had impacted on the MHW through warm advection transportation and may significantly contribute to the record-breaking intensity of the MHW, in addition to the impact of abnormal atmospheric circulations. Finally, we showed that a mass mortality of sea cucumbers in the study region during mid-summer 2018 was highly likely caused by the MHW through severe heat stress.
Intensification of the water cycle in northern catchments: Long-term isotopic and hydrometric evidence and consequences   
Authors: Laudon Hjalmar
Published: March 2024

Water limitation has become one of the most pressing threats to groundwater and forest resources also in the north. Despite increased precipitation in many high latitude regions, suggested by both empirical observations and climate models, large regions are on a trajectory of increasing water limitation that already caused substantial loss of forest biomass, threatening targets for biodiversity, carbon sequestration, and bioeconomy. Key to these northern challenges are how the intensification of the water cycle results in earlier snowmelt, enhanced evapotranspiration (ET) rates, lower groundwater levels during the vegetation period and declining summer runoff. In my talk, I will present 25 years of consistent water isotopic data from precipitation, groundwater and stream flow in order to disentangle critical processes that determine the availability of water for trees and streams during the growing season. I will draw my examples from the Krycklan Catchment Study (KCS) that has supported water isotope research for over tree decades. The research infrastructure is based on a 6790 ha catchment and includes a dozen gauged streams, 150 groundwater wells, 500 permanent forest inventory plots, a large radar system for tree water content measurements and a 150 meter tall tower for biosphere-atmosphere carbon and water exchange processes. The combination of long-term monitoring, shorter-term research projects, and large-scale experiments, including manipulations of the water cycle related to climate, forest management and peatland restoration. This work has contributed to our process understanding of water in the boreal landscape, while also supporting the development of better models and guidelines for research, policy, and management.
Three-dimensional influencers in the Western Baltic Sea: finite time coherent sets and their role for biological processes
Authors: Vortmeyer-Kley Rahel , Cahill Bronwyn , Berthold Maximilian , Feudel Ulrike
Published: March 2024

Describing and tracking three-dimensional flow structures in an ocean setting may explain elemental and biodiversity pattern. A possible tool can be finite time coherent sets. These sets are Lagrangian Coherent Structures characterized by minimal leakage and minimal exchange with their surrounding environment.In oceanic settings, they can be understood as separated waterbodies or eddies playing an important role for transport and mixing processes.Due to limited interaction with their surroundings, they even influence biological processes by providing competitive advantages for some species, for example, optimal temperature or nutrient conditions.In a case study of three-dimensional finite time coherent sets in the Western Baltic Sea in May and July 2018, we show some different impacts on biological processes:enhancement of phytoplankton growth in the set's surrounding,
transport of cold nutrient rich water from shallower to deeper regions, and
the formation of transient, moving dynamical niches with higher temperature inside the coherent set compared to its surrounding, prolonging the life of an existing phytoplankton bloom that is trapped during the formation of the coherent set.
Moreover, different dynamical patterns can be observed inside the finite time coherent sets during their travel and lifetime. Temporal stratification and mixing inside the coherent sets suppress or enhance growth temporally and locally.In the coherent set’s surrounding, the formation of a “sticking” manifold supports the development of a local phytoplankton bloom in the upper water column.Our case study in the Western Baltic Sea provides a first step towards understanding the impact of three-dimensional coherent sets on transport processes and phytoplankton growth in the Baltic Sea, as well as, the formation of dynamical pattern inside three-dimensional coherent sets.
Method for near-surface three-dimensional velocity modeling based on first-arrival
Authors: cheng ran
Published: March 2024

In seismic exploration, three-dimensional near-surface tomography is key to solving complex statics problem and is an important prerequisite for migration imaging. To this end, this paper starts with the principles of ray tracing theory and tomographic inversion methods. Based on a comprehensive comparative analysis of the advantages and disadvantages of traditional ray tracing methods and numerical algorithms for tomographic inversion, using the first arrival times in three-dimensional seismic data, a high-precision three-dimensional ray tracing method based on multi-retracing technology and a tomographic inversion method constrained by prior information such as small refraction and micro logging throughout the process are proposed. First, this paper use near-surface survey information such as micro logging and small refraction to constrain the establishment of an initial velocity model and constrain tomographic inversion to improve the vertical inversion accuracy of the model. Secondly, to address the loss of shallow layer information due to excessive shot-to-detector distances, this paper introduces a virtual detector point technique. By adding one or more virtual detector points between known shot points and detector points within a close offset range, the density of rays at near offsets is increased, thereby improving the lateral tomographic imaging accuracy of the near-surface. At the same time, various constraints are introduced during the inversion process, including the range of velocity restriction, inversion slowness correction size constraints, internal iteration number constraints of tomographic inversion, dual-grid inversion, velocity extrapolating and smoothing, etc., greatly improving the accuracy of inversion and the quality of tomographic imaging. Given the large computational volume of three-dimensional data and the high memory consumption of large sparse matrices, this paper employs compressed storage and tomographic matrix solving techniques, greatly saving memory space and enhancing computational efficiency. The test results on theoretical models and actual data show that the ray tracing method used in this paper provides essentially correct ray propagation paths, consistent with geological laws. The final inversion results effectively reveal the velocity and thickness of near-surface low-speed layers and deceleration layers, demonstrating the correctness and effectiveness of the inversion method proposed in this paper.Keywords: Velocity modeling, Ray tracing, Tomographic inversion, Micro logging, Small refraction
Coastal carbon sink accounting toward construction of three-dimensional ocean carbon sink field
Authors: Chen Shang , Sun Xiaoping
Published: March 2024

Developing a low-carbon economy is an important means of implementing the United Nations 2030 Sustainable Development Goals, and mastering the carbon sequestration potential of coastal ecosystems is the foundation for implementing carbon neutrality and developing a low-carbon economy. The net sequestrated carbon by phytoplankton and macro-algae is calculated in the Yancheng coastal waters in the west Yellow Sea by subtracting the amount of carbon released through respiration from the amount of photosynthetic carbon sequestration. The annual sequestrated carbon of shellfish is calculated using the carbon content of shells. From 2019 to 2021, the sequestrated carbon of the coastal ecosystem in Yancheng was 67.5431, 72.4331, and 69.5343 million tons of carbon, with an average annual growth rate of 2.95%. The carbon sequestration in the coastal ecosystem of Yancheng is mainly provided by phytoplankton, while the carbon sequestration of macro-algae such as lavers and shellfish such as clams is relatively very low. During these three years, the sequestrated carbon of phytoplankton increased at an average annual rate of 2.96%. However, the carbon sequestration by macro-algae and clams decreased at an average annual rate of 56.08% and 21.11% respectively. The decrease in carbon sequestration by large algae and shellfish is caused by the decrease in the cultivation area of laver and clam in Yancheng in 2021. The construction of a 3-dimensional coastal carbon sink farm consisting of a suspended raft laver mariculture at the surface layer, phytoplankton in the seawater column, and benthic clam mariculture was recommended to the local government.
Generation of internal wave breathers by steady flow over an obstacle
Authors: Lamb Kevin
Published: March 2024

In certain stratifications internal wave breathers can exist. Such stratifications include symmetric double-pycnocline continuous stratifications provided the two pycnoclines are sufficiently far apart. Here the generation of breathers by steady flow over a small obstacle is investigated using a two-dimensional non-hydrostatic primitive equation numerical model under the Boussinesq approximation. The symmetric stratification consists of two thin hyperbolic tangent pycnoclines which separate the fluid into three nearly constant density layers. The two pycnoclines have the same thickness and the same density jump across them. The upper and lower constant density layers have the same thickness. Nonlinear internal waves in this type of stratification can be modelled with the modified KdV (mKdV) equation. If the pycnoclines are far enough apart the cubic coefficient in the mKdV equation is positive and weakly-nonlinear theory predicts the existence of breathers. In this numerical study a large number of simulations have been undertaken, varying the speed of the upstream flow, the amplitude and width of the obstacle and the thickness of the upper and lower layers. Multiple upstream propagating internal wave breathers are generated in a small region of parameter space. Their formation appears to arise from nonlinear-interactions in the lee wave field downstream of the obstacle. 
The Effect of Different Loss Mechanisms on Ring Current Dynamics Based on The STRIM Model 
Authors: Wei Ziming , Yu Yiqun , Ma Longxing
Published: March 2024

Charge exchange, Coulomb collisions, and field line curvature scattering (FLCS) are among the main loss mechanisms of the ring current during the recovery phase of a magnetic storm. Drifting around the Earth, ring current ions encouter charge exchange with neutral hydrogen from the geocorona, which results in the generation of high energy neutrals and low energy ions. As the energetic ring current particles pass through the thermal plasma, they are scattered due to the Coulomb collision, suffering energy loss and pitch angle diffusion. FLCS occurs when the ratio of the ion’s gyration radius to the curvature radius of the magnetic field line is large enough and chaotic scattering of the particles occurs. In this study, We propose a new method of calculating the diffusion coefficients in association with FLCS, which can be applied to a more stretched magnetic configuration. With the newly calculated diffusion coefficients, we investigate the effect of FLCS on ring current particles by using the Storm-Time Ring Current Model (STRIM) and compare its role with other ring current ion loss mechanisms like charge-exchange and Coulomb collisions. The ion lifetimes associated with these different loss mechanisms are compared to gain a deeper understanding of the impact of different mechanisms in the evolution of ring current. It is found that these mechanisms exert influences on different energies and pitch angles and their impacts also vary during different phases of the magnetic storm. 
Simple oceanographic and paleoclimate modeling highlights the same dynamical process: intrinsic variability paced by a deterministic forcing
Authors: Pierini Stefano
Published: March 2024

Within the climate model hierarchy, simple models usually play the important role of highlighting dynamical processes that can possibly govern climate phenomena. If, in addition, their results are in significant agreement with observations, the processes thus identified are even more likely to regulate the actual phenomena. In this context, the dynamical process of intrinsic variability paced by a deterministic forcing (also called deterministic excitation, DE [1]) is highlighted here by two simple models of different degrees of complexity and set in the different contexts of paleoclimate and physical oceanography. In both cases, despite the simplicity of the models, the results show significant agreement with observations.The DE mechanism requires the system (i) to possess intrinsic nonlinear relaxation oscillations (ROs) and (ii) to be in the excitable state (i.e., ROs do not emerge spontaneously but can be excited, and therefore paced, by a suitable forcing); moreover, (iii) ROs are excited by a deterministic forcing if a given tipping point is passed.In the first case [1], the abrupt late Pleistocene glacial terminations are shown by a conceptual model to correspond to the excitation, by the astronomical forcing, of ROs describing glacial-interglacial transitions (e.g., [2]). In the second case [3], ROs describing the Kuroshio Extension low-frequency variability [4] are shown, by a primitive equation ocean model, to be excited remotely by the North Pacific Oscillation. These results show how simple modeling approaches of different complexity advance process understanding and can, therefore, provide theoretical guidelines for interpreting state-of-the-art ESM results.[1] Pierini S., 2023: The deterministic excitation paradigm and the late Pleistocene glacial terminations. Chaos, 33, 033108.[2] Gildor H. and E. Tziperman, 2001: A sea ice climate switch mechanism for the 100-kyr glacial cycles. J. Geophys. Res., 106, 9117–9133.[3] Pierini S., 2014: Kuroshio Extension bimodality and the North Pacific Oscillation: a case of intrinsic variability paced by external forcing. J. Climate, 27, 448-454.[4] Pierini S., 2006: A Kuroshio Extension System model study: decadal chaotic self-sustained oscillations. J. Phys. Oceanogr., 36, 1605-1625.
Sensitivity Analysis of Filtering Methods for Tropical Easterly Waves Classification
Authors: Valencia Betancur Maria Juliana , Yepes Johanna , Mejia John F. , Builes-Jaramillo Alejandro , Salas Hernan D.
Published: March 2024

Tropical easterly waves (TEWs) are quasi-periodic wave disturbances found within the easterly trade winds during boreal summer and autumn. They influence the synoptic-scale circulation dynamics in tropical America and contribute up to 50% of the seasonal precipitation (June to November) over northern South America. This study evaluates the sensitivity of different spectral bands in classifying TEWs based on daily vorticity at 700 hPa during the Organization of Tropical East Pacific Convection (OTREC) campaign. TEWs were identified in real-time using data from NOAA's Marine Tropical Surface Analysis. Complementarily, we refined TEWs identification by correlating it with 700 hPa filtered relative cyclonic vorticity from ERA5. To consider the uncertainties associated with the TEWs chronology selection, we employed two filtering methodologies: the Fast Fourier Transform (FFT) with periodicity bands of 3–10 days, 2.5–12 days, and 2.5–15 days, as well as the Ensemble Empirical Mode Decomposition (EEMD) with periodicity bands of 3–6 days, 4-12 days, and 3–15 days. Thirteen TEWs were initially reported by NOAA as crossing the Caribbean at 80°W. In our study, we further analyzed these waves by correlating areas characterized by westward-moving features of filtered relative cyclonic vorticity at the same longitude. Through this analysis, distinct classifications emerged using different filters, revealing the presence of 5 to 9 TEWs. The results show that TEWs classification is sensible to the filtering methods and periodicity band windows.
Conservative mixing of highly alkaline groundwater with hypersaline seawater at Shark Bay recorded by Ba isotopic compositions in stromatolitic carbonates
Authors: Hohl Simon V. , Lin Yibo , Viehmann Sebastian , Martin Ashley
Published: March 2024

Hamelin Pool in Shark Bay, Western Australia, is a natural laboratory to study in situ stromatolitic carbonate formation in a hypersaline lagoon. Stromatolitic carbonates sampled at three different tidal environments (supratidal, intertidal and subtidal; cf. Martin et al., 2023) show a gradual increase in Ba isotopic compositions (d138Ba) from -0.12 ‰ to modern open ocean values (up to 0.6 ‰) with decreasing Ba concentrations following classic Rayleigh pattern. Declining Ba/Ca ratios (0.93 to 0.32) follow conservative mixing trends with increasing Co, Li, Sr and Ni concentrations from the shore to subtidal environments. Due to the lack of riverine influx into Shark Bay, groundwater discharge is the likeliest source for two end-members mixing with seawater. We observe fingerprints of the groundwater end-member in a supratidal sample showing particular low, stable Ba isotope values (-0.12 ‰), which further corresponds with elevated Mn/Sr ratios and the lowest O isotope compositions (2.9 ‰) as an indicator for a meteoric origin. This end-member likely reflects carbonate precipitation near shore under the influence of groundwater discharge and reaction with high alkalinity fluids derived from the local Tamala Limestone aquifer (d138Ba = 0.09 to 0.24 ‰ at 0.3 to 19 PSU; cf., Mayfield et al., 2021). In contrast, the stromatolitic carbonates that form in equilibrium with a saline end-member show heavy Ba isotope compositions (0.57‰).Injection of alkaline groundwaters into the hypersaline waters of Hamelin Pool likely contributed to an enhanced rate of carbonate precipitation, possibly catalysed by nucleation within or onto extra-polymeric substances of diverse microbial mats. Interaction of benthic microbes, especially cyanobacteria, in alkaline waters may offer promising carbon sequestration pathways in the modern high pCO2 atmosphere and small-scale mitigation to the harmful impacts of the current climate crisis.References: Martin et al., 2023, GCA; Mayfield et al., 2021, Nature Communications