bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of cloud droplet formation and growth under turbulent conditions in LACIS-T
Authors: Melnik Svetlana , Schmalfuß Silvio , Stratmann Frank , Pöhlker Mira , Niedermeier Dennis
Published: March 2024

The study of cloud formation is a crucial aspect of understanding the Earth's weather and climate system. Cloud droplet formation, growth, and the resulting size distributions are influenced by various atmospheric conditions. Despite extensive research, the impact of turbulence on droplet formation and growth remains incompletely understood.
To address this knowledge gap, we investigated the effect of turbulent saturation fluctuations on these mentioned processes. The respective study was conducted using the turbulent Leipzig Aerosol Cloud Interaction Simulator (LACIS-T, Niedermeier et al., 2020) which is a closed-loop, moist-air wind tunnel. LACIS-T is an ideal facility for pursuing mechanistic understanding of these processes and interactions under well-defined and reproducible laboratory conditions.
In LACIS-T, by mixing of three conditioned air streams (i.e. two particle-free air streams, and one aerosol stream), it is possible to precisely adjust temperature and water vapor fields so as to achieve various (super)saturation levels. A passive or active grid are used to introduce turbulence.
In our study, we examined the growth of size-selected monodisperse NaCl particles under various conditions of saturation and temperature at different turbulence patterns. Results of the study provide new experimental insights into the effect of turbulence on cloud droplet formation, growth, and consequently, the shape of cloud droplet size distributions.
Niedermeier et al. (2020), Atmos. Meas. Tech., 13, 2015-2033, https://doi.org/10.5194/amt-13-2015-2020.
Keywords: Cloud droplet growth, Droplet size distribution, Turbulence, Saturation fluctuations
The pattern effect: How radiative feedbacks depend on surface warming patterns and influence near-term projections 
Authors: Rugenstein Maria
Published: March 2024

Recent research has highlighted that radiative feedbacks — and thus climate sensitivity — are not constant in time but depend sensitively on sea surface temperature patterns. I will discuss three implications of this realization.First, I will show how coupled climate models fail to reproduce observed surface warming patterns and global mean top of the atmosphere (TOA) radiation trends. I use large initial condition ensembles to compare observations to account for internal variability and model mean-state biases. For certain periods, not a single ensemble member can reproduce observed values of surface temperature trends and TOA radiation trends. Models which more greatly underestimate the observed local sensitivity of surface and TOA, and models with a weak variability in the Equatorial Pacific surface temperatures tend to have a higher equilibrium climate sensitivity. Despite these astonishing observation-model discrepancies their global-mean temperatures are simulated well which points to a common model problem in surface heat fluxes and ocean heat uptake.Second, I will discuss the relevance of the pattern effect for climate change projections. Given that problems coupled models have in reproducing observed warming patterns, we should doubt their pattern evolution in projections. I will introduce “surface warming pattern storylines” starting from the observations and bridging to simulated future patterns in standard scenarios. I show that (CMIP) coupled climate models used ubiquitously for climate change projections underestimate the uncertainty of possible global-mean temperature evolutions due to their surface warming patterns throughout the 21st century.Third, I will introduce how a feed-forward convolutional neural network (CNN) can be trained to learn the pattern effect and predict global-mean TOA radiation from surface warming patterns. I use explainable artificial intelligence methods to visualize and quantify that the CNN draws its predictive skill for physically meaningful reasons. Remarkably and different from traditional approaches, I can predict radiation under strong climate change from training the CNN on internal variability alone. This out-of-sample application works only when feedbacks are allowed to be non-linear or equivalent, changing in time, which is another, independent manifestation of the relevance of the pattern effect.
Active triangle zones within the two orogens convergence zone, central Caucasus, Georgia
Authors: Shikhashvili Tamar , Mariam Bekurashvili Mariam , Giorgadze Anzor , Razmadze Aleksander , Enukidze Onise , Alania Victor
Published: March 2024

Collision and subsequent convergence of Arabia and Eurasian plates during the late Alpine time caused extensive intracontinental deformation in the Caucasus region (e.g., Cavazza et al., 2023). Inversion of back-arc basins, exhumation, and crustal thickening took place in the far-field zone, forming two orogens, and leading to a convergence between the Lesser Caucasus (LC) and Greater Caucasus (GC). Continuous convergence between the LC and GC caused incremental deformation of the Kura foreland basin (Alania et al., 2023). Our study area is located within the LC-GC convergence zone in the western Kura foreland basin and is represented by the lenticular-shaped compressional basin formed by northward and southward-directed thrusting. 2D seismic reflection profiles revealed the presence of triangle zones at the frontal part of the LC retro-wedge and GC pro-wedge. According to analog, seismic, and sequential kinematic modeling results, the frontal part of the GC is represented by a double wedge-dominated triangle zone and is characterized by the presence of passive, active wedges and passive-forethrust. In the frontal part of the LC orogen, the syn-kinematic (Middle-late Miocene) strata have been deformed and uplifted by passive-back thrusting at the triangle zone. Seismic reﬂection proﬁles show north-vergent duplex and structural wedge at the triangle zone beneath the thrust front monocline and is represented by Cretaceous-Paleogene strata. Western part of the triangle zone of the Kavtiskhevi-Akhalkalaki area is introduced by south-vergent imbricated fan (passive-back thrusts). The imbricated fan is characterized by fault-propagation folding. The kinematic evolution of south-vergent fault-propagation folds is related to northward propagating duplex. Recent and historical earthquakes and paleoseismic data indicate that the frontal part of LC and GC is tectonically active (e.g., Stahl et al., 2022; Tsereteli et al., 2016). ReferenceAlania, V., et al. (2023). Interpretation and analysis of seismic and analog modeling data of triangle zone: a case study from the frontal part of western Kura foreland fold-and-thrust belt, Georgia. Frontiers in Earth Sciences 11, 1195767.Cavazza, W., et al. (2023). Two-step exhumation of Caucasian intraplate rifts: a proxy of sequential plate-margin collisional orogenies, Geoscience Frontiers 15, 101737.Stahl, T. A., et al. (2022). Recent Surface Rupturing Earthquakes along the South Flank of the Greater Caucasus near Tbilisi, Georgia. Bull. Seism. Soc. Am. XX, 1–19.Tsereteli, N., et al. (2016). Active tectonics of central-western Caucasus, Georgia. Tectonophysics 691, 328-344.
Consistent Mean Sea Surface and sea level change estimation in the Era of Climate Change – application to SWOT processing. 
Authors: Andersen Ole Baltazar , Nerem Steve , Nielsson Bjarke
Published: March 2024

Since the beginning of the precision satellite altimeter era in the early 1990s, efforts have been focused on computing the mean height of the ocean surface for use in various geodetic and oceanographic studies. With 30 years of satellite measurements now available, it is time to rethink how we model the mean sea surface (MSS) in the era of climate change.There are linear changes in the height of the ocean surface due to melting ice and increasing ocean heat content that will not average to zero when computing the mean. Today, there are places in the ocean that are 15 cm higher than they were at the start of the altimetric era some 30 years ago. Today, conventional MSS models like CLS15/22 or DTU15/21 are roughly 5 cm lower than what is observed by present-day satellites like Sentinel6-MF.We propose that linear sea level changes are estimated simultaneously and consistently with the mean sea surface computation and added to the definition of the MSS, which is tied to a particular date in time. This is possible because the MSS are tied to the 2003.01.01 period for the DTU MSS models. We also investigated the acceleration of sea surface height but found these small and still unstable [Nerem et al., 2018]. We also found that these are still somewhat dependent on the Side A correction of the TOPEX mission. We conclude that a longer time series is needed before a stable map of the accelerations can be computed and applied.There is considerable evidence that using a 30-year trend pattern in sea surface height is stable and is driven by the “forced response” of Greenhouse gases and aerosols. These patterns will be reasonably persistent as we move forward in time.Testing a new DTU23MSS mean surface tailored to the year 2023 to our processing of the recently available 2023 SWOT data, we find this new DTU23MSS reduces the spatial variability of the SWOT data which is important to the processing and particularly the roll-error correction applied to the 2D SWOT sea surface height data. Applying the new DtU21MSS to conventional satellites like Sentinel-3A/B and 6 reduces both offset and spatial variability of the data indicating that the new MSS is actually very close to a “present-day mean” 
P-wave anisotropic tomography unveils the crustal structure of Etna volcano (Italy)
Authors: Lo Bue Rosalia , Rappisi Francesco , Firetto Carlino Marco , Giampiccolo Elisabetta , Cocina Ornella , Vanderbeek Brandon , Faccenda Manuele
Published: March 2024

Mount Etna (Italy), renowned for its persistent eruptive activity, is a hazardous volcano shaped by the intricate interplay between magma uprising and a complex tectonic and geodynamic context. Despite extensive monitoring, seismic tomography encounters challenges in accurately depicting the shallow-intermediate P-wave velocity structures, primarily due to the common assumption of isotropy. This study discards such simplification, employing a novel methodology (Vanderbeek and Faccenda, 2021) to simultaneously invert for perturbations to P-wave isotropic velocity and three additional anisotropic parameters (i.e., magnitude of hexagonal anisotropy, azimuth, and dip of the symmetry axis).By analysing the seismicity recorded in the Mt. Etna area from 2006 to 2016, we constructed 3D anisotropic P-wave tomography models to better constrain the crustal structure of Etna volcano within the framework of its local tectonic setting. The revealed anisotropy patterns are consistent with the structural trends of Etna, unveiling the depth extent of fault segments. We identify a high-velocity volume, deepening towards northwest, recognized as the collision-related subducting foreland units (i.e. Hyblean foreland carbonate slab; Firetto Carlino et al., 2022) that appear to confine a low velocity anomaly, hypothesized to be the expression of a deep magmatic reservoir. A likely tectonic-origin discontinuity affects the subducting units, facilitating the transfer of magma from depth to the surface. This geological setting may explain the presence of such a very active basaltic strato-volcano within an atypical collisional geodynamic context. This research improves our understanding of the dynamics governing magma and fluid ascent beneath the volcanic edifice and emphasises the importance of considering anisotropy in seismic investigations. It contributes to our framework for understanding volcanic processes and mitigating associated risks. VanderBeek, B. P., & Faccenda, M. (2021). Imaging upper mantle anisotropy with teleseismic P-wave delays: insights from tomographic reconstructions of subduction simulations. Geophysical Journal International, 225(3), 2097-2119.Firetto Carlino, M., Scarfì, L., Cannavò, F., Barberi, G., Patanè, D., & Coltelli, M. (2022). Frequency-magnitude distribution of earthquakes at Etna volcano unravels critical stress changes along magma pathways. Communications Earth & Environment, 3(1), 68.
Imaging the crustal structure of the Central Pyrenees using Seismic Interferometry
Authors: Soto Ruth , Andrés Juvenal , Gabàs Anna , Bellmunt Fabián , Macau Albert , Clariana Pilar , Rey-Moral Carmen , Rubio Félix , Izquierdo-Llavall Esther , Mochales Tania , Pueyo Emilio L. , Ayala Conxi
Published: March 2024

The Pyrenees constitute a natural laboratory where hundreds of geological and geophysical data have been acquired during the last decades. It represents a roughly E-W oriented doubly vergent orogen formed during the Alpine Orogeny. Deep seismic reflection data obtained during the 80s revealed its crustal architecture that resulted from the subduction of the Iberian plate under the European lithosphere at its central part.In this work we applied seismic interferometry to the same passive dataset through two different techniques aiming to construct two independent images of the Central Pyrenean lithosphere, to enhance the current knowledge of the area. The main objectives are to compare them and correlate the obtained results with previous data. Data were acquired within the IMAGYN project along a NE-SW 70 km-long profile extending from the Southern Pyrenees (Pedraforca and Cadí Units, northern Iberia) to the northern part of the Axial Zone, close to Ax-les-Thermes (France). Data came from three to five months of continuous recording from an almost linear array of 43 seismic stations (being 17 and 26 broadband and short-period stations, respectively). The two applied techniques are (1) the global-phase seismic interferometry (GloPSI), using continuous recordings of teleseismic (30⁰ < epicentral distance < 95⁰) and global earthquakes (> 120⁰ epicentral distance), and (2) the use of continuous ambient seismic noise recordings through autocorrelation. Despite both methods rely on different energy sources, they are complementary and use static receivers. In the first method (GloPSI), we extracted global phases (PKP, PKiKP and PKIKP) and their reverberations within the lithosphere. The selected phases were autocorrelated and stacked to construct a high-resolution pseudo zero-offset reflection image. The second approach provided an approximation to the zero-offset reflection response of a single station. Results reveal features that can be correlated in both reflection images. The crust-mantle boundary is mapped as a relative flat interface at approximately 35-40 km depth. Crustal interfaces detected at 15 and 25 km depth can be related to the Conrad discontinuity and other compositional changes within the crust.(This work is part of the project “High-resolution imaging of the crustal-scale structure of the Central Pyrenees and role of Variscan inheritance on its geodynamic evolution” (IMAGYN), PID2020-114273GB-C22 funded by MCIN/AEI/10.13039/501100011033)
Role of Sub-Cloud Rain Evaporation on Boundary Layer Decoupling over Barbados Island
Authors: Sarkar Mampi , Zheng Youtong , Vogel Raphaela
Published: March 2024

This study investigates the influence of sub-cloud rain evaporation on the decoupling of sub-tropical marine cumulus-topped raining boundary layers. Using 24-hour wind lidar and Ka-band radar observations on February 9, 2020 from the Barbados Cloud Observatory (BCO), along with in-situ rain microphysical observations from the ATR aircraft during the EUREC4A field campaign, we extract rain microphysical parameters - raindrop number concentration (N0) and geometric mean diameter (Dg). These parameters, alongside surface relative humidity measurements, serve as inputs to initialize a single-column rain evaporation model, allowing us to derive vertical profiles of rain evaporation fluxes and evaporation cooling rates. Our analysis identifies 'top-heavy' profiles characterized by maximum evaporative cooling near the cloud base, featuring smaller Dg and larger N0. Conversely, 'bottom-heavy' profiles exhibit larger Dg and smaller N0, with maximum evaporative cooling closer to the surface. Notably, our findings reveal that top-heavy profiles, especially when cloud bases are higher, tend to be more decoupled than bottom-heavy profiles. The higher decoupling of the top-heavy profiles is attributed to the stable configuration of the evaporatively-cooled moisture layer just below the warmer cloud layer, hindering moisture transport to the cloud. In contrast, for a bottom-heavy profile where the evaporatively-cooled moisture layer is accumulated closer to the surface over a warmer sea surface, surface-driven mixing promotes moisture transport to cloud bases, resulting in less decoupling. The decoupling index, independently estimated from the difference between ceilometer-based cloud base height and empirically determined lifting condensation level, enhances the robustness of our results. While emphasizing the significant influence of sub-cloud rain evaporation on the decoupling of cumulus-topped raining boundary layers, our study has not explored other factors like surface and radiative fluxes, which could also contribute to the boundary layer decoupling.
Variability and budgets of Dissolved Inorganic Carbon and Alkalinity over the north Indian Ocean using a high-resolution model 
Authors: Madkaiker Kunal , Rao Ambarukhana Devendra
Published: March 2024

This study employs a high-resolution MITgcm-DIC model at 5 km spatial resolution with climatological forcing to investigate the biogeochemical dynamics of surface dissolved inorganic carbon (DIC) and alkalinity (ALK) over the northern Indian Ocean. The physico-chemical parameters of the model are validated against available observational data to ensure its accuracy. The DIC biogeochemical module is integrated within the model framework, considering multiple DIC sources and sinks, including air-sea CO2 exchange, biological production, and carbonate mineral dissolution. To analyse the influences of various processes within our domain, we focussed on the surface DIC and ALK budgets. This investigation helps us understand the intricate interplay of drivers impacting the budgets. The DIC and ALK budgets are found to be significantly influenced by the counterbalancing effects of advective and diffusive terms. We also assessed the role of biological activity and observed that productivity causes a continuous uptake of CO2, which leads to a reduction in surface DIC. Since freshwater intrusion is an important factor governing the surface dynamics of waters in north Indian Ocean, we examined the impact of freshwater dilution on surface DIC and ALK concentrations. The surface ALK budget is predominantly governed by freshwater flux. The dilution of ALK and DIC is attributed to the influence of both precipitation and river runoff. Regions where evaporation exceeds precipitation and river runoff exhibit an increase in the concentration of these variables. The findings shed light on the regional variations along the north Indian Ocean, providing valuable insights into the dominance and interactions of these mechanisms. This study is valuable for enhancing our understanding of regional carbon cycling dynamics in our domain with implications for global carbon cycle models and climate-related predictions. The findings are relevant not only for the scientific community but also for policymakers and stakeholders concerned with oceanic and environmental health.
Trawling Impacts on Benthic Carbon Sequestration, Storage, and Processing: A Systematic Review
Authors: Felgate Stacey , Kaiser Michel , Sciberras Marija
Published: March 2024

Marine sediments are a significant sink for anthropogenic carbon dioxide (CO2)1. Bottom trawl fisheries constitute the most widespread physical disturbance to carbon-rich seabed habitats2. Recent research has sparked concern that this disturbance can turn marine sediments into a large source of CO23, but this is subject to ongoing debate4,5,6. Uncertainties exist regarding the effect of bottom trawling on carbon sequestration, remineralisation, and storage. To address this, we conducted a systematic review and meta-analysis of the existing literature to assemble a comprehensive, up-to-date database looking at how demersal mobile fishing affects: (i) the amount and type of carbon found in benthic sediments; (iii) the geochemical, biological, and physical parameters which control the fate of benthic carbon; (iii) the magnitude and direction of benthic-pelagic carbon fluxes; and (iv) the geochemical, biological, and physical parameters which control the fate of resuspended carbon. Here we present methodological details alongside preliminary findings of the resultant meta-analysis. We highlight the parameters which carry the greatest and least uncertainties and suggest key knowledge gaps to help target future field and laboratory studies to help better constrain the effect of bottom trawling on the benthic-pelagic carbon fluxes and processing.1. Atwood et al., 2020. Global patterns in marine sediment carbon stocks. Frontiers in Marine Science; 2. Hiddink et al., 2017. Global analysis of depletion and recovery of seabed biota after bottom trawling disturbance. PNAS; 3. Sala et al., 2021. Protecting the global ocean for biodiversity, food and climate. Nature; 4. Hilborn and Kaiser, 2022. A path forward for analysing the impacts of marine protected areas. Nature; 5. Hiddink et al., 2023. Quantifying the carbon benefits of ending bottom trawling. Nature; 6. Atwood et al., 2023. Reply to: Quantifying the carbon benefits of ending bottom trawling. Nature.
Numeraical twins and deep neural network to predict groundwater flow 
Authors: Gloaguen Erwan , Liang Xiao Xia , Claprood Maxime , Paradis Daniel
Published: March 2024

Groundwater is and will increasingly be under threat due to many anthropic stresses like climate changes, population growth in coastal cities, pollution,... It is known that realistic 3D numerical twins of aquifers allows forecasting their groundwater flow and permits to forecast their behavior in regards to different hydrogeological changes. In this project, we built an ensemble of numerical twins of an aquifer located south-east to Montreal, Qc, Canada, using a nested geostatistical workflow in order to optimize a pump and treat plant constrain by multiple environmental indicators. The ensemble permits to obtain a quantitative measure of the uncertainty for each indicator base on the optimization of the ensemble. While these models have proved to be useful operationally speaking, any changes or scenarios that must be tested requires the managers of the resources to hire qualified companies. This prevents the long term use of the numerical twins and reduce their democratisation to the resource management. This motivates the training of a deep neural graph network on the numerical twins. The trained network is able to forecast short term changes of the groundwater flow due to new pumping rates or new pumping wells in less than a minute. 
Photochemistry of the Recent Martian Atmosphere at Different Obliquities
Authors: Luo Yangcheng , Lefèvre Franck , Forget François
Published: March 2024

Due to gravitational perturbations from nearby planets, Mars has undergone large obliquity variations through its history. Modeling suggested that in the past 10 million years, the obliquity of Mars has varied by up to 20°, from 15° to 35°. During time periods of high obliquity, the polar regions of Mars received more solar insolation and became warmer, leading to more rapid sublimation of water ice and higher atmospheric water content. During periods of low obliquity, on the contrary, water vapor condensed in polar regions and the atmosphere became dry. This variation has a significant impact on the photochemistry of the Martian atmosphere, as HOx radicals, which are photolytic products of water vapor, are key catalysts to the photochemistry of the Martian atmosphere. It is then of interest to explore the photochemistry of Mars at different obliquities and its effects on the climate and surface of Mars, as part of the objectives of the “Mars Through Time” European Research Council project. In preparation for future Mars sample return missions, it is important to evaluate the preservability of potential organic matter buried in the shallow subsurface with different oxidizing capacities of the atmosphere at different obliquities.In view of the three-dimensional nature of the sublimation, transport, and condensation of water, we employ a fully coupled photochemical-radiative-dynamical model—the Mars Planetary Climate Model, developed at LMD in collaboration with other institutions—to simulate the photochemistry of the recent Martian atmosphere at obliquities between 15° and 35°. We find that at high obliquities, water content of the Martian atmosphere could exceed the present-day value by more than one order of magnitude, and the OH concentration could be higher by up to two orders of magnitude. These drastic changes result in a significantly lower CO concentration. Opposite effects are observed from low-obliquity simulations. The nonlinearity in the photochemical system, however, has led to more complex behaviors of the HO2 and H2O2 concentrations. We will explain the mechanisms behind these effects and discuss their implications in the paleoclimate of Mars and the preservation of potential biogenic organic matter in the shallow subsurface. We will also address the long-standing “CO-deficit” problem in Mars photochemical modeling, and show how the state-of-the-art 3D photochemical modeling helps to mitigate the problem.
 A laboratory model of fragmentation of a 2D membrane by waves. Analogies and differences with sea ice.
Authors: Berhanu Michael , Saddier Louis , Aksil Mathéo , Ambre Palotai , Tsamados Michel
Published: March 2024

The marginal ice zone is the transition region between the dense floating ice pack and the open ocean. In this zone, the interaction of surface waves with sea ice is highly complex. The sea ice is broken up into fragments, the floes, which can split into smaller parts and drift under the action of waves and underwater current. Although the downscaling is challenging, laboratory model experiments can contribute to a better understanding of this process coupling fluid and solid mechanics on a large range of time and space scales. We propose to study the fragmentation of a floating membrane, made up of 10 µm graphite particles arranged in a monolayer, by gravity surface waves with a wavelength of around 15 cm [1]. For a sufficiently strong wave amplitude, the raft progressively breaks up, developing cracks and producing fragments whose sizes decrease over a time scale that is long relative to the wave period. We then study the distribution of the fragments produced during the fragmentation process. The visual appearance of the size-distributed fragments surrounded by open water bears a striking resemblance to the floes produced by the fracturing of sea ice by waves. The fragmentation concepts and morphological tools developed for sea ice floes can be applied to our macroscopic analog. Although the mechanics of the two systems differ in their physical properties and in the fracture process, our experiment provides a model laboratory system for studying the fragmentation of floating 2D materials [1] Saddier, L., Palotai, A., Aksil, M., Tsamados, M., & Berhanu, M. (2023). Breaking of a floating particle raft by water waves. In arXiv preprint arXiv:2310.16188.
Comparison of global high-resolution fossil fuel CO2 emissions data products to Vulcan v4.0: sector differences, urban geographies, and methodological guidance
Authors: Gurney Kevin , Dass Pawlok , Sun Huilin , kato anna , Gawuc Lech , Nematchoua Modeste
Published: March 2024

New global greenhouse gas emission products have emerged in recent years providing emissions estimation at increasing fine space/time scales. Furthermore, these efforts are moving away from traditional forms of proxy linear downscaling and toward the use of machine learning and integration of some forms of “bottom-up” data. In terms of application, there is interest in applying these data products to the city-scale, assisting and supporting mitigation activities in the global urban governance level. However, it is also acknowledged that developing these very high-resolution efforts at the global scale come with particular challenges associated with data availability, method limitations, and data quality variations. Here we use a very high-resolution data product developed in the United States, the Vulcan version 4.0 emissions, as a point of comparison with two of the new global very high-resolution efforts: Climate Trace, and GRACED. The ‘Vulcan Project’ is an effort to compute bottom-up CO2 emissions from fossil fuel combustion (FFCO2) and cement production for the entire USA. Vulcan v4.0 quantifies emissions from 2010 to 2021 for multiple sectors to the point, line, and polygon spatial scale. We use detailed comparison with Vulcan to illuminate and inform aspects of the global efforts that many warrant further investigation or methodological development. We upscale Vulcan to match the resolution of the global data products and aggregate as necessary to isolate sectoral matches. Using statistical analysis techniques we isolate differences that may be systematic and explainable via alternative methodologies and/or data sources. Our aim is to strengthen and improve all high-resolution efforts at multiple scales and recommend where scale limitation may exist.
Estimation of seasonal weather persistence during the Holocene from varved records
Authors: Martin-Puertas Celia , Boyall Laura , Hernandez Armand , Ojala Antti , Abrook Ash , Kosonen Emilia , Lincoln Paul , Swingedouw Didier
Published: March 2024

Global warming is leading to more persistent boreal summers in the Northern Hemisphere, characterised by a longer season with more extreme heat waves. These seasonal changes have already led to many ecological and socio-economic implications. Statistical significance between summer weather persistence and its potential drivers is weak due to the short instrumental period, in turn preventing skilful predictions. In this study, we develop a new proxy for seasonal weather persistence based on varve thickness measurements to extend observations further back in time. We used two lakes, Nautajärvi in Finland and Diss Mere in England, which provide i) a continuous, seasonally resolved varved records that cover most of the Holocene Epoch; ii) a detailed understanding of the annual depositional varve model supported by lake monitoring, demonstrating that the seasonal sedimentation responds to summer and winter-type weather conditions; and iii) a consistent varve structure over the entire study period, so data are comparable through time. In both lakes, the varve model is made of two seasonal layers, representing the limnological summer and winter. The thickness of the seasonal layers indicate either the length of the season (i.e. longer period of sedimentation) and/or occurrence of extreme events (e.g. intensification of the sedimentological process). This agrees with the definition of seasonal weather persistence, which refers to either stationarity or recurrence of characteristic surface weather or atmospheric circulation of a season. In order to estimate the relative persistence of the summer and winter season over a year, we calculate the percentage of the winter and summer layers contributing to the varve (annual) thickness in the two lakes. Our results show that the early and late Holocene annual mean climate was controlled by winter weather variability, while the mid-Holocene has a predominant summer component. The Holocene winter-summer-winter weather pattern in Europe follows the evolution of the regional latitudinal temperature gradient (LTG) supporting current hypothesis that a weakening of the LTG in response to Global Warming is the origin of more persistent summers today.
Central structure of a Mozambique Channel mesoscale eddy-ring dipole
Authors: Penven Pierrick , Ternon Jean Francois , Noyon Margaux , Herbette Steven
Published: March 2024

Located in the southwest Indian Ocean, between Madagascar and the African continent, the Mozambique Channel is a western boundary current system characterized by an intense eddy activity (Halo et al. 2014). Large anticyclonic rings, reaching up to 300 to 350 km in diameter and 2000 m of vertical extension, are structuring the marine ecosystems from phytoplankton to top predators (de Ruijter et al., 2002; Ternon et al., 2014, Weimerskirch et al., 2004). They impact the environmental conditions on the Mozambican shelves by promoting the upwelling of nutrient rich deeper waters (Lamont et al., 2010; Malauene et al, 2014). Coastal waters, generally rich in plankton and nutrients, can be also be transported offshore along the edges of the rings. The occurrence of an eddy dipole with the anticyclonic ring in the northern side of the cyclonic eddy can enhance the processes (Roberts et al., 2014). Mesoscale eddy flux is supposed to be the dominant source of nutrients for the central Mozambique Channel (José et al., 2016). The first leg of the RESILIENCE (fRonts, EddieS and marIne LIfe in the wEstern iNdian oCEan) multidisciplinary oceanographic cruise on board R/V Marion Dufresne II in April-May 2022 was focusing on the central structure of a dipole composed by a Mozambique Channel Ring and a cyclonic spiral eddy. The goals were here to observe at high resolution the mesoscale and submesoscale structures in the core of the dipole, their origins and evolution, and their potential implications for biogeochemical and ecological processes in the Mozambique Channel. To do so we crossed several times the eastern side of the dipole, towing a moving vessel profiler in addition to SADCP continuous observations and multidisciplinary stations and trawls at regular intervals. The dipole event commenced on 24 April 2022 and endured for 24 days. Existence of strong currents, reaching speeds of 150 cm/s, leads to the prevalence of horizontal stirring as the dominant process. This results in an efficient and fast transport of material from the shelf to the central Mozambique Channel. The Omega equation was used to show the dominance of a smaller scale meander for the vertical velocities. Layering is evident in the frontal structure. This first documentation of the in-situ central structure of a dipole, formed by the convergence of a Mozambique Channel Ring and a spiral eddy, lays the foundation for subsequent ecological investigations.
Measuring river surface velocity using UAS-borne Doppler radar
Authors: Zhou Zhen , Riis-Klinkvort Laura , Ahrnkiel Jørgensen Emilie , Coppo Frías Monica , Bauer-Gottwein Peter , Rietz Vesterhauge Alexander , Haugård Olesen Daniel , Dobrovolskiy Alexey , Kadek Alexey , Orlic Niksa , Grubesa Tomislav , Grosen Henrik , Nielsen Sune , Wennerberg Daniel , Fagerström Viktor , Axén Jenny , Gustafsson David
Published: March 2024

Compared to traditional river surface velocity measurement techniques such as in-situ point measurements with electromagnetic current meters, remote sensing techniques are attractive because measurements are fast, low cost and contactless. Based on Unmanned Aerial Systems (UAS) equipped with optical equipment (e.g., HD camera) and Doppler radar, surface velocity can be efficiently measured with high spatial resolution. UAS-borne Doppler radar is particularly attractive, because it is suitable for real-time velocity determination and has fewer limitations (no seeding of the flow required, no daylight required, works for both narrow and wide rivers).In this paper, videos from a UAS RGB video camera were analysed using both Particle Image Velocimetry (PIV) and Space-Time Image Velocimetry (STIV) techniques. Furthermore, we recorded full waveform signal data using a 24 GHz continuous wave Doppler radar (e.g., Geolux RSS-2-300) at multiple waypoints across the river. Different from previous processing methods, which only considered the processed velocity from Doppler radar itself, we propose an algorithm for picking the correct river surface velocity from the raw data. The algorithm fits two alternative models to the raw data average amplitude curve to derive the correct river surface velocity: a Gaussian one peak model, or a Gaussian two peaks model.Results indicate that river flow velocity and drone-induced propwash velocity can be found in the river’s lower flow velocity portions (i.e., surface velocity between 30 cm/s and 80 cm/s), while the drone-induced velocity can be neglected in fast and highly turbulent flows (i.e., surface velocity > 80 cm/s). To verify the river flow velocity derived from Doppler radar, a mean PIV value within the footprint of the Doppler radar at each waypoint was calculated. Finally, quantitative comparisons of electromagnetic velocity sensor data (OTT MF Pro) with STIV, mean PIV and Doppler radar revealed that UAS-borne Doppler radar could reliably measure the river flow velocity.
Permafrost in talus slopes: what are the main drivers of low temperatures and ice content ?
Authors: Hauck Christian , Amschwand Dominik , Gluzinski Tomasz , Hilbich Christin , Hoelzle Martin , Mathys Tamara , Mollaret Coline , Morard Sarah
Published: March 2024

Coarse-blocky landforms are assumed to be the most resilient permafrost occurrences due to low thermal conductivity and their seasonal asymmetric internal convection processes and have been addressed in many field and modelling studies. In this contribution we will put a specific focus on the most general of these landforms, the ubiquitous talus slopes, which are understudied compared to other mountain permafrost landforms such as rock glaciers. Talus slopes exist in all mountain ranges and at different elevations, including middle mountains where they give rise to specific undercooled micro-climatic conditions. In many cases, internal convection processes are the main reason that the cool micro-climatic conditions could be preserved over long time scales. The ice content can be variable, ranging from zero at low elevations to the presence of ice cores at elevations where permafrost is widespread. However, the ice content in most talus slopes is generally unknown, as boreholes are extremely scarce and standard geophysical techniques (such as Electrical Resistivity Tomography and Seismic Refraction techniques) exhibit problems in detecting medium to small ice contents in coarse blocky substrates. In this contribution we use a compilation of data from a large number of different talus slopes in Europe, the Central Andes and Central Asia to attempt to (1) quantify the influence of slope angle, substrate and thickness of the talus on the internal air circulation and its cooling effect and (2) address the application of emerging geophysical techniques to improve the quantification of ice content in these substrates.
Nitrogen Isotopic Studies in an Urban Estuary: Not Just a story of Anthropogenic Influences
Authors: Swart Peter , Saied Amel , Gidley Maribeth , Karim Aliza , Kelly Elzabeth , Silverstein Rachel , Sinigalliano Chistopher , Troxler Tiffany , Ahearn Sean
Published: March 2024

Over a twelve-month period, between June 2021 and June 2022, a study was carried out that investigated possible causes of water quality decline in northern Biscayne Bay (South Florida, USA).  During this investigation a large number of different water quality parameters were monitored at 22 sites and waterways feeding into the Bay (Miami River, Little River, Biscayne Canal, and Snake Creek) in this area. Additional samples were also collected in the central region of Biscayne Bay around Virginia Key and Key Biscayne, Coconut Grove, and Matheson Hammock. At each site water and vegetation samples were collected.  Water samples were analyzed for standard nutrient parameters (TN, TP, NO3-, NH4, chlorophyll, turbidity, salinity, and dissolved oxygen content) and vegetation samples analyzed for their δ15N and δ13C values, and CN ratios. A smaller number of additional water samples were collected for the analysis of the δ18O and δ15N values of the NO3- and sediment samples were analyzed for their dδ15N values at each site. This presentation concentrates principally on the nitrogen isotopic portion of the study. The highest δ15N values were found in algae and plants collected from the Biscayne Canal, Little River, and Miami River sites, while lower values were measured at the central Biscayne Bay sites.  The Little River sites showed a strong seasonality with δ15N values ranging from +8 ‰ in the wet season to over +13‰ at the start of the dry season, while Miami River and Biscayne Canal sites remained at values of between +9 to +13‰ throughout the year.   While elevated δ15N  values are associated with the input of anthropogenic waste, leaking from septic tanks along the canals, elevation of the d15N values in excess of typical human δ15N values is driven by fractionation during nitrification and incorporation by assimilation. We propose that nitrogen derived from septic tanks ,with elevated δ15N  values, mixes with nitrogen derived from the natural environment as well as from artificial fertilizers (both with lower δ15N values) to produce a pool of nitrogen with intermediate δ15N values.  This reservoir is then further enriched in 15N during the process of assimilation and nitrification which fractionates the δ15N  value of the residual NO3-. 
Comparing Machine Learning Methods for Dynamical Systems
Authors: Schötz Christof , White Alistair , Boers Niklas
Published: March 2024

We explore the task of learning the dynamics of a system from observed data without prior knowledge of the laws governing the system. Our extensive simulation study focuses on ordinary differential equation (ODE) problems that are specifically designed to reflect key aspects of various machine learning tasks for dynamical systems - namely, chaos, complexity, measurement uncertainty, and variability in measurement intervals. The study evaluates a variety of methods, including neural ODEs, transformers, Gaussian processes, echo state networks, and spline-based estimators. Our results show that the relative performance of the methods tested varies widely depending on the specific task, highlighting that no single method is universally superior. Although our research is predominantly in low-dimensional settings, in contrast to the high-dimensional nature of many climate science challenges, it provides insightful comparisons and understanding of how different approaches perform in learning the dynamics of complex systems.
The influence of a submarine canyon on the wind-driven downwelling circulation over the continental shelf
Authors: Saldías Gonzalo , Figueroa Pedro , Allen Susan
Published: March 2024

The response of a coastal ocean model, simulating a typical Eastern Boundary system, to downwelling-favorable winds with and without the presence of a submarine canyon is studied. Three contrasting bathymetric configurations, considering different slopes and depth shelves, are evaluated. Experiments without a submarine canyon represent the well-known downwelling circulation and cross-shore structure with a downwelling front and the development of frontal instabilities generating density anomalies from the bottom up to 50 meters. The presence of the submarine canyon drives important changes in cross-shore flows, with opposing velocities on either side of the canyon. Onshore (offshore) and downward (upward) velocities develop in the upstream side of the canyon in the time-dependent and advective phases. Instabilities developed and are modified principally downstream of the canyon. Overall, the net impact of the canyon is to enhance offshore and downward transport into the canyon. However, particle tracking experiments reveal that particles can become trapped inside the canyon in an anticyclonic circulation when the particles pass the canyon over the continental slope. This particles stay inside the canyon up to 15 days.
Improving Groundwater Recharge Estimation Using Remote Sensing Information in a Multiobjective Calibration.
Authors: Cortes Ramos Diego , Piña Fulano Adriana Patricia
Published: March 2024

This study aims to enhance groundwater spatiotemporal recharge estimation by incorporating three different sources of remote sensing information into a hydrological model. Traditional approaches for model calibration using flow rates often encounter equifinality issues, as aggregated variables may not adequately represent the spatial behavior of the watershed. To address these limitations, we hypothesized that including spatial information in the calibration process could lead to improved estimations.The TETIS model was implemented in the Lebrija river watershed, located in the Magdalena middle valley of Colombia. R and Ostrich were used to couple the model with remote sensing data in a multiobjective calibration process with the Pareto archived dynamically dimensioned search algorithm. Subsequently, four calibration scenarios were executed, with the first one as a control scenario using only flow rates. The other three scenarios progressively integrated evapotranspiration and soil moisture remote sensing information. As a validation step, GRACE information was used to calculate recharge and compared with the simulations.The inclusion of remote sensing information improved the model spatial behavior in 47.9%. And comparations with GRACE also show an improvement representation of groundwater recharge in 31.9%. In conclusion, the incorporation of remote sensing data in the calibration process significantly increased the reliability of groundwater recharge estimations in the model.