bluuebunny/crossref_metadata_2025 huggingface dataset:
Reconstructing 20th century burned area by combining global fire model input, satellite observations and machine learning
Authors: Lampe Seppe , Gudmundsson Lukas , Humphrey Vincent , Vanderkelen Inne , Le Saux Bertrand , Thiery Wim
Published: March 2024

The temporal coverage (∼2000 to present) of global burned area satellite observations limits many aspects of fire research e.g., long-term trend analysis, disentangling the effect of various drivers on fire behaviour and detection and attribution of changes to climate change. As a result, global fire models are more frequently being called upon to answer questions about past and future fire behaviour. Unfortunately, the limited temporal coverage of the observations also hinders the development and evaluation of these fire models. The current generation of global fire models from ISIMIP are able to simulate well some characteristics of regional fire behaviour such as mean state and seasonality. However, the performance of these models differs greatly from region to region, and aspects such as extreme fire behaviour are not well represented yet. Here, we explore the possibility of using machine learning algorithms to model burned area from the same input parameters that are passed to global climate models. Once trained, this data-driven model can be evaluated against regional proxies for past fire behaviour e.g., tree rings and charcoal records. Hopefully, this data-driven reconstruction can provide valuable insights on the 20th century burned area, and can help improve and evaluate fire models.
Evolution of marine ice sheets with bed sedimentation
Authors: Hewitt Ian , Herpain Emilie
Published: March 2024

Marine ice sheets terminate in the ocean where they form floating ice shelves or calve icebergs.  They can significantly influence sea level because of the potential for rapid transfer of grounded ice (with thickness greater than floatation) to floating ice shelves or icebergs.  Most models of marine ice sheet evolution assume that the bed elevation stays constant, or responds isostatically to the weight of the ice sheet.  However, it is known that there is sediment deformation beneath the ice sheet (which is in part what enables the ice to move), and that deposition of this sediment in the vicinity of the grounding line can result in the formation of a grounding-zone wedge.  Although it is widely recognised that such a wedge can influence the evolution of the grounding line (where the ice becomes afloat), there is incomplete knowledge about the interaction of the ice and sediment/bed dynamics.In this study, we build on idealised two-dimensional (flow-line) models of a marine ice sheet to investigate the influence of a deforming sediment layer at the bed.  We examine how different conditions lead to the development of a grounding zone wedge, and how this impacts the possible steady states of the model under given climate forcing, and under different assumptions about the sediment dynamics.  We then examine how the sediment dynamics, and the presence of the grounding-zone wedge, influence the stability of the system.
Study about perception of soil compaction in grasslands: what can be learnt to foster sustainability and policy intervention?
Authors: Puff Manjana , Garcia-Santos Glenda , Bohner Andreas
Published: March 2024

The study of the sustainable strategies at regional level complies with the current European Green deal to monitor soil compaction. However, recent studies showed that the implementation of sustainable practices by farmers that are useful for an ecological transition can be slow down by development and technology transfer capacity and or an attitude of resistance of farmers themselves to innovations.In the context of soil compaction in grasslands, we studied the influence of different management strategies (use of cattle and machinery) and the farmers’ perception of soil compaction. The studied bio-physical indicators in the top soil were organic carbon, plant indicators, bulk density, soil texture, plant indicators, infiltration capacity, water repellence, water content and electrical conductivity at the surface level of permanent grasslands in a total of 16 grasslands in the time period 2022-24 within Görtschitztal and Magdalensberg in south Austria (Carinthia).First results showed correlation between the use of cattle and number of entries in the field with heavy machinery and the increase of the bulk density, though always within low levels of compaction and at the surface. We also found cases of mismatch perception of soil compaction, which may hinder sustainable practices in the future. The results of this study may serve to increase understanding about the theoretical factors influencing the farmer’s perception of soil compaction problems, providing a valuable addition to the available literature. In terms of policy implications, a clear picture of the factors underlying the dynamics of farmer’s perception can be useful in the future to better targeting policy measures tailored to encourage sustainable practices and innovations in the agricultural sector. We show possible directions affecting perceptions at farmer-based level.
The VirES service as a platform for accessing and analysing geomagnetic data
Authors: Smith Ashley , Pačes Martin , Santillan Daniel ,   ESA & Swarm DISC
Published: March 2024

VirES is an ESA service which was been developed to support the goals of the Swarm mission, providing a number of mechanisms for accessing and working with Swarm products. It has since been extended to cover other LEO datasets under the Swarm umbrella: calibrated platform magnetometer data from Cryosat-2, GRACE, GRACE-FO, GOCE, as well as INTERMAGNET ground observatory data, with plans for more. We provide a graphical web interface (currently only supporting Swarm data) [1], API-based access via both the OGC standards and the HAPI specification [2], a Python client [3], and a Jupyter-powered cloud environment (so-called Virtual Research Environment - VRE) and associated notebook collection [4]. Through these connected approaches, we provide a variety of pathways for interaction with the data and models (see also: the Swarm data handbook [5]).Swarm activities are shifting to toolboxes and on-demand processing (to interactively deliver higher-level products), more open-source software, and more connection with other datasets and data providers. We provide some of these Python tools preinstalled in the VRE alongside other thematic libraries, and are developing SwarmPAL [6] in collaboration with the Swarm community.These works contain contributions from EOX IT Services and many people across ESA, Swarm DISC, and the wider community.[1] https://vires.services[2] https://vires.services/hapi[3] https://viresclient.readthedocs.io[4] https://notebooks.vires.services[5] https://swarmhandbook.earth.esa.int[6] https://swarmpal.readthedocs.io
Automatic detection of cold-temperate transition surface in polythermal glaciers using GPR and machine learning
Authors: Letamendia Unai , Ramírez Iván , Navarro Francisco , Benjumea Beatriz , Schiavi Emanuel
Published: March 2024

Ground-penetrating radar (GPR) has been shown to be an effective tool to infer the hydrothermal structure of polythermal glaciers. Knowledge of this structure is fundamental to the study of their dynamics. The cold-temperate transition surface (CTS) is the englacial boundary between cold and temperate ice. It can be identified by GPR because of the contrast in permittivity between dry cold ice and water-rich temperate ice. However, the interpretation of the CTS using GPR has traditionally been a very time-consuming and manual process. Here we show a procedure based on machine learning for detecting CTS automatically. The data used for training a convolutional neural network were collected in both Svalbard, in the Arctic (radar with central frequency of 25 MHz), and the South Shetland Islands in the Antarctic Peninsula region (200 MHz central frequency). Various metrics revealed success rates in the classification in the order of 90%. The size of the training dataset is limited, so current work is focused on enlarging its size by using random variations of synthetic radargrams generated by forward modelling with gprMax.
Long-term changes of the geomagnetic field: recent progress, challenges and applications 
Authors: Panovska Sanja
Published: March 2024

The Earth's magnetic field provides protection against highly energetic particles from the Sun and outer space. Throughout geological epochs, the time-varying geomagnetic field exhibited periods of dramatic changes, both in intensity and direction. Recent data compilations of paleomagnetic records enable us to model the long-term, global evolution of the geomagnetic field and better understand the internal dynamics and underlying phenomena. Until now, global reconstructions of the geomagnetic field cover the past 100,000 years and the Matuyama-Brunhes reversal. A few models are available for the Laschamps excursion 41,000 years ago, a period marked by globally low intensity and a complex, multipolar field structure. These models enable the identification of robust characteristics of the geomagnetic field's behavior during this extreme event.The spatial and temporal changes influence the shielding and cosmogenic nuclide production rates. In general, the higher the field intensity, the larger the shielding and the fewer cosmogenic nuclides are produced in the atmosphere. Variations in the production rates of cosmogenic radionuclides reconstructed from ice cores and sediments provide an independent proxy of paleointensity variations. On the one hand, models constrained by paleomagnetic data can be validated through comparison with actual measurements from ice and marine cores. On the other hand, the cosmogenic radionuclide data can be jointly inverted with the paleomagnetic data to build multi-proxy models of the geomagnetic field. Cosmogenic radionuclide records also serve as a proxy for solar variability and extreme solar events. Global geomagnetic field reconstructions are used to assess the space weather effects during an extreme solar storm event over the past millennia.
Crustal Structure across the Northern Scandinavian margin along the Senja OBS Profile 
Authors: Alemdar Rafet Ender , Kahraman Metin , Shulgin Alexey , Breivik Asbjorn , Artemieva Irina , Thybo Hans
Published: March 2024

The Senja onshore-offshore seismic profile is located in the northwestern part of Fennoscandia, extending from onshore Norway into the North Atlantic Ocean. The Fennoscandian lithosphere has been formed by the amalgamation of terranes and microcontinents to an Archean core, primarily during the Palaeoproterozoic. The later Sveconorwegian (Grenvillian) and Caledonian orogenies had strong effect on the western part of Fennoscandia. The Scandia Mountain range extends along the west coast with elevation up to 2500 m, mainly coinciding with the surface outcrops of Caledonian deformed crust. Its location far from any active plate boundary makes this mountain range enigmatic. The offshore continental part of Fennoscandia experienced a long post-Caledonian extensional period for more than 200 My, and it now forms a continental shelf below sea level extending to the continent to ocean transition.We present a crustal-scale seismic profile along the NW-SE striking Senja OBS Profile in northern Scandinavia between 12°E and 20°E. This profile covers both offshore and onshore domains over a total distance of ~300 km across the Norwegian shelf in the North Atlantic Ocean, Senja Island, and mainland Norway. Airgun shots from the vessel Hakon Mosby were used as sourced for the refraction/wide-angle reflection survey. The dataset includes recordings on 5 ocean bottom seismometers (OBS) on the shelf, slope, and oceanic environment, complemented by 68 onshore stations at 1.3-kilometre intervals. We present a seismic p-wave velocity model derived by ray-tracing modelling of P-wave arrivals along the profile.The model includes a deep sedimentary basin extending to ~10 kilometres depth with velocities between ca. 2 km/s and 5.10 km/s, which gradually thickens from the coast to its maximum thickness of 10 km about 25 km from the coast. This deep sedimentary basin is very wide (approximately 8 km). Further offshore the sedimentary cover of the shelf and oceanic environment is relatively thin. The upper crustal velocity below the sedimentary sequence has velocities of ~ 6.0 km/s. 
How temperature-induced density and viscosity differences affect the flow distribution through well screens and may influence heat recovery of HT-ATES systems
Authors: Beernink Stijn , Hartog Niels , Vardon Philip J. , Bloemendal Martin
Published: March 2024

High Temperature Aquifer Thermal Energy Storage (HT-ATES) allows the large scale seasonal storage of sustainable heat available in summer, enabling its utilization in winter, hence reducing GHG emissions. The feasibility and potential of HT-ATES systems is largely determined by its recovery efficiency. The stored groundwater, at 40 to 80 °C higher temperature than the ambient groundwater, has a relatively low density and viscosity. The differences in density and viscosity between the stored and ambient groundwater create the potential for buoyancy-driven flow to the top of the aquifer during storage, which may lead to increased heat losses during recovery as commonly observed in earlier HT-ATES studies. Conventionally, these studies assume an uniform in- and outflow distribution of water through the well screen during injection and extraction. However, as density and viscosity changes also affect the pressure state in the well and influence the flow resistance of the aquifer, the flow distribution through the well screen is potentially impacted by these changes of density an viscosity, especially at higher storage temperatures. Therefore, this study addresses the effect of density and viscosity differences on the flow distribution through HT-ATES screens during injection and extraction for relevant storage conditions, and further assesses its impact on heat recovery compared to simulations including uniform well flow distribution. Results show that, due to both density and viscosity changes at high storage temperature, the flow distribution through the well screen may be significantly changed depending on mainly the hydrogeological and well operating conditions. Compared to HT-ATES simulations with uniform flow distribution, increased thermal recovery efficiencies are observed ranging from 0 – 8% in the 5th year of operation for the varied conditions in this study.
Tropical mountain ice core  : A Goldilocks indicator for global temperature change
Authors: Liu Zhengyu , Bao Yuntao , Thompson Lonnie , Mosley-Thompson Ellen , Tabor Clay , Zhang Guang , Yan Mi , Lofverstrom Marcus , Montanez Isabel , Oster Jessica
Published: March 2024

 Tropical mountain ice core : A Goldilocks indicator for global temperature change   Zhengyu Liu1,2,3, , Yuntao Bao1, Lonnie G. Thompson3,4, Ellen Mosley-Thompson1,3,  Tabor Clay5, Guang J. Zhang6, Mi Yan2, Marcus Lofverstrom7, Isabel Montanez8,  Jessica Oster9  1.      Department of Geography, The Ohio State University, Columbus, OH 2.      School of Geography Science, Nanjing Normal University, Nanjing, China. 3.      Byrd Polar and Climate Research Center, The Ohio State University, Columbus, OH 4.      School of Earth Sciences, The Ohio State University, Columbus, OH 5.      Department of Earth Sciences, University of Connecticut, Storrs, CT 6.      Scripps Institute of Oceanography, University of California San Diego, San Diego, CADepartment of Geosciences, University of Arizona, Tucson, AZ
Department of Earth and Planetary Sciences, University of California–Davis, Davis, CA
Department of Earth and Environmental Sciences, Vanderbilt University, Nashville, TN
 Very high tropical alpine ice coresprovide a distinct paleoclimate record for climate changes in the middle and upper troposphere. However, the climatic interpretation of a key proxy, the stable water oxygen isotopic ratio in ice cores (), remains an outstanding problem. Here, combining proxy records with climate models, modern satellite measurements and radiative-convective equilibrium theory, we show that the tropical  is an indicator of the temperature of the middle and upper troposphere, with a glacial cooling of -7.35+-1.1oC (66% CI). Moreover, it severs as a “Goldilocks-type” indicator of global mean surface temperature change, providing the first estimate of glacial stage cooling that is independent of marine proxies as -5.9+-1.2oC. Combined with all estimations available gives the maximum likelihood estimate of glacial cooling as -5.85+10.51oC .  
Global warming increases population exposure to wildfires 
Authors: Galizia Luiz , Castet Christelle , Voulgarakis Apostolos
Published: March 2024

Wildfires are expected to increase under warmer and drier conditions, yet little is known about their potential effects on population at global scale. Here, we developed a novel framework based on statistical wildfire model and spatial demographic data to better understand how global warming alters population exposure to wildfires throughout the world. We sought to model annual burn rate with relevant explanatory variables, such as climate, land cover, and topography to simulate historical and future wildfire frequency at global scale. To do so, we used a Generalized Additive Model combined with historical climate data and an ensemble of CMIP6 climate projections under the SSP5-8.5 scenario. We then analysed population exposure to wildfires combining population count across the wildland–urban interfaces with the simulated historical and future wildfire frequency. Our results indicate that in the present day the highest population exposure to wildfires is in southeast Asia, parts of South America and Africa, due to the large number of people living in wildland–urban interfaces with a high wildfire frequency. All other things being equal, global warming was found to increase population exposure, with an expansion of the regions with high wildfire frequency in east and south Europe, southeastern Asia, parts of North and South America. The estimated increase in population exposure may also imply potential impacts on the built environment and human health in the absence of mitigation or adaptation measures.
Rheological structure beneath the southern Sumatra constrained from postseismic deformation of the 2007 Mw8.4 Sumatra earthquake
Authors: Yang Siyuan , Yan Hu
Published: March 2024

The 2007 Mw8.4 southern Sumatra earthquake provides an opportunity to understand the rheological properties in the southern Sumatra, particularly in the Mentawai gap. In this study, we have derived the first 3-year GPS postseismic observations to study deformation processes based on a three-dimensional viscoelastic finite element model. In the model, a 2-km-thick shear zone attached to the fault is used to simulate the time-dependent and stress-driven afterslip. Model results indicate that a model with a heterogenous shear zone better fits the horizontal GPS observations than a model with a uniform shear zone. This heterogenous shear zone is divided into the southern shear zone and northern shear zone (Mentawai gap), which is separated by the southern edge of the Mentawai gap. The southern shear zone is further divided into an upper (depths of ≤ 20 km) and lower shear zone (depths of > 20 km). The viscosities in these three shear zones are determined to be 5 x 1017 Pa s, 1016 Pa s and 1018 Pa s, respectively. Model results indicate that a weakened mantle wedge is required to better explain the observed uplift in vicinities of the rupture area.
Recovering North Atlantic meridional transport variability from bottom pressure anomalies – a revisit
Authors: Liu Le , Schindelegger Michael
Published: March 2024

Significant resources have been and are continuing to be devoted to monitor variability in the North Atlantic Meridional Overturning Circulation (AMOC), an essential component of the climate system. Transport mooring arrays are one means of choice, but given their confinement to individual latitudes, complementary large-scale observations are desirable. Here we follow lines of previous research and explore whether ocean bottom pressure (OBP) estimates from present and future satellite gravimetry missions can add useful constraints on interannual AMOC variability between 25°N and 55°N. Central to these considerations are OBP signals along the continental slope of the basin’s western boundary, which—in principle—allow for recovery of geostrophic AMOC variability above 1000 m, between 1000–3000 m, and in some latitudes also below 3000 m. We apply the geostrophic calculation to latest GRACE (Gravity Recovery and Climate Experiment) monthly OBP solutions, in part to document current system capabilities and highlight known shortcomings (e.g., coarse horizontal resolution and data noise). Despite these issues, there are tentative signs of robust and meridionally connected transport variations at latitudes of the New England continental slope (between 35°N and 42°N), including a positive anomaly of ~2 Sverdrup between 2006 and 2012 below 1000 m. We further assess the feasibility of recovering AMOC variability from boundary pressures in high-resolution coupled climate models. These datasets provide useful information on the variance of the involved quantities as well as locations (i.e., depths and latitudes) where accurate knowledge of OBP changes is most important. Insights gained here will be used in upcoming closed-loop orbit simulations that will make special allowance for mass change recovery on the continental slope through dedicated parameterizations in the gravity field estimation.
Downscaling ESA CCI Soil Moisture: From 0.25° to 0.01° using a two-step machine learning approach
Authors: Himmer Thomas , Damm Carolina , Zappa Luca , Dorigo Wouter
Published: March 2024

Soil moisture (SM) is a key component of the Earth system and a key factor in climatological and hydrological processes as it regulates water, carbon and energy fluxes between land and atmosphere. For various applications – including monitoring and forecasting of hydro-climatic extremes (floods, droughts), forest fires, and crop yield estimation – high-resolution SM information is required. Currently, the ESA CCI (Climate Change Initiative) product provides a long-term, global record of SM with daily temporal resolution and a spatial resolution of 25km (0.25°). This coarse resolution can limit its usefulness in some of the mentioned fields of application.This study aims to improve the spatial resolution of the ESA CCI SM product to 1km (0.01°) through machine learning, incorporating dynamic and static ancillary variables influencing the spatial organization of SM at this finer scale. This procedure consists of two steps, in which the coarse resolution data is first downscaled to 0.05° and then further to 0.01°. Currently, the ancillary variables used in the downscaling process consist of land cover information from the Copernicus Global Land Service (CGLS) including soil properties, land cover types, the Normalized Difference Vegetation Index (NDVI) and a digital elevation model. Recent assessments against in-situ measurements from the International Soil Moisture Network (ISMN) across Europe reveal that the downscaled SM offers a more detailed portrayal of the spatial distribution of SM compared to the original ESA CCI product while retaining the high temporal accuracy. However, these investigations also show that the impact of the NDVI on the model prediction is small.In future iterations of the downscaling model, the goal is to explore possibilities for incorporating more influential variables that achieve greater information gain (e.g. Land surface temperature) and to examine other machine learning approaches in addition to the currently used random forest regressor to further improve the downscaling accuracy.
Using single-grain multiple elevated temperature luminescence to understand fluvial sediment transport at the system scale
Authors: Spano Tessa , Rhodes Edward , Hodge Rebecca
Published: March 2024

Multiple elevated temperature infra-red stimulated luminescence (MET-IRSL) has great potential to provide detailed information on the movement of sediment grains through time and space. MET-IRSL stimulates grains using infra-red light at a series of elevated temperatures to access multiple charge populations with different bleaching behaviours. Length of past light exposure and duration of storage events can be determined by the relative difference between multiple signals, or ages, for a single grain. With more signals, we can see deeper into the history of an individual grain.Single-grain measurements paint a fine-resolution picture of how a system operates, often masked by multiple grain average measurements. The power of single-grain measurement is underpinned by three basic principles: 1) A single grain has a single transport-storage history (Rhodes and Leathard, 2022), 2) Populations of >200 grains per sample allows for quantitative estimation of the most likely, or ‘dominant’ history for a given sample, 3) It is possible to isolate different grain populations, with different histories or provenance within a single sample.Using samples collected from the active channel of the Allt Dubhaig in Scotland, we present results from a bleach recovery experiment to illustrate an optimal method for quantifying most likely length of past light exposure using single grains, and a gaussian mixture model approach to isolating different grain populations within a single sample. Combined with a numerical model of single-grain bleaching and burial, we apply these approaches to elucidate past and present fluvial sediment transport information for the Allt Dubhaig, Scotland, and the Santa Clara River, southern California.
Using Multitemporal Sentinel-1 imagery for wet snow dynamics characterization in Mediterranean mountain catchments: a case study in Sierra Nevada, Spain
Authors: Torralbo Muñoz Pedro , Pimentel Leiva Rafael , Polo Gómez María José , Notarnicola Claudia
Published: March 2024

Monitoring snowmelt dynamics in mountainous catchments  is essential for comprehending downstream water release, streamflow response and consequently, for a better management of water resources at the catchment scale.  In a consolidated snowpack when external inputs become positive, the snow turns into wet snow and the melting phase begins. This change modifies the dielectric constant of the snowpack which can be detected remotely using information in the microwave region of the electromagnetic spectrum. Sentinel-1 (S-1) synthetic-aperture radar (SAR) has emerged as a widely utilized technique for this purpose due to its frequent acquisitions and all-weather capability. This study seeks to, first, explore the capabilities of C-band S-1 SAR imagery, which has been demonstrated in previous studies in other regions such as the Alps, in capturing multi-seasonal snowmelt dynamics and, second to linked these wet-dynamics to changes in streamflow response over Mediterranean mountain areas . The study was carried out at two scales: plot and catchment: At the plot scale, the Refugio Poqueira experimental site, which is located at 2500 m a.s.l. was chosen. At the catchment scale, the headwaters of the Poqueria River, which is a  snow-driven catchment  located in the southern face of Sierra Nevada, was selected. Four hydrological years with high hydroclimatic variability, from 2016-2017 to 2019-2020, were used in the study to capture the heterogeneity of the area. The general change detection approach for identifying wet snow was adapted for these regions, utilizing the average S-1 SAR image from the preceding summer as  reference imagery and employing a threshold of −3.00 dB for discriminating wet snow. This adaptation was validated using Landsat images as a reference dataset, yielding a general accuracy of 0.79. The local scale analysis demonstrates that S-1 SAR imagery was  able to capture four types of melting cycles including the well-known main melting event during the spring season. The other three melting cycles are linked to the Mediterranean mountains climate and can occur throughout the hydrological year. When applied at the catchment scale, distributed melting-runoff onset maps were developed to enhance understanding of the spatiotemporal evolution of melting dynamics. Finally, a linear correlation between melting dynamics and streamflow was established for prolonged melting cycles, with a determination coefficient (R2) ranging from 0.62 to 0.83 and an average delay of approximately 21 days between melting onset and streamflow peak.Acknowledgments: This work has been funded by the project PID2021-12323SNB-I00, HYPOMED—“Incorporating hydrological uncertainty and risk analysis to the operation of hydropower facilities in Mediterranean mountain watersheds”.
Investigating a local windstorm using measurements and large-eddy simulations
Authors: Krieger Nicolai , Kühnlein Christian , Sprenger Michael , Wernli Heini , Bättig Philipp , Hervo Maxime , Krieger Ulrich
Published: March 2024

During a winter storm in January 2007, a train derailed due to strong winds in a narrow valley in northeastern Switzerland. The accident was attributed to the Laseyer, a local windstorm characterized by flow reversal that manifests as easterly to southeasterly winds at the valley floor during strong prevailing northwesterly winds above. We analyze case studies of the local windstorm using sonic anemometer and Doppler lidar measurements. The data reveal a highly turbulent flow in the narrow valley and extreme wind speeds exceeding 45 m/s during Laseyer conditions.Additionally, we use a newly developed large-eddy simulation (LES) atmospheric model to improve our understanding of the local windstorm. The model is implemented in a Python environment with the GT4Py (GridTools for Python) domain-specific library to enable performance portability.  Robust and efficient solution of the nonhydrostatic compressible equations is achieved using a finite-volume semi-implicit discretization following ECMWF’s IFS-FVM. LESs are performed above the highly complex terrain of northeastern Switzerland, which leads to extremely steep slopes exceeding 70°. With these LESs, we identify the mechanism behind the local windstorm, study its sensitivity to ambient flow conditions, and characterize the flow conditions in the narrow valley.
Machine-learning-based analysis and reconstruction of high-resolution sea-surface temperatures for the North Sea and Baltic Sea
Authors: Kruschke Tim , Kadow Christopher , Meuer Johannes , Hinrichs Claudia
Published: March 2024

The Federal Maritime and Hydrographic Agency of Germany performs weekly analyses of sea surface temperatures (SST) for the North Sea and Baltic Sea on an operational basis. The analysis is based on in-situ observations and satellite retrievals. Existing procedures require manual quality control and subjective decisions on plausibility of measurements combined with simple interpolation techniques. This study presents ongoing work to develop new procedures based on a machine learning approach, designed to fill in gaps in observational data fields. The employed inpainting technique makes use of a convolutional neural network (CNN) that is trained with complete SST-fields from high-resolution (~3 km) ocean model simulations and masks derived from satellite retrievals to ignore regions covered by clouds on respective days.First validation efforts for the North Sea based on reconstructing modelled fields that were excluded from training data indicate very promising results, that is an RMSE of ~ 0.5 K or less for most regions of the North Sea. However, areas with high variance such as waters very close to the coast and the Norwegian Channel exhibit larger errors up to 1 K. Additionally, we can show that errors tend to be larger when less observational data are available, e.g. on days with lots of clouds.It will be tested if optional features of the algorithm may help to improve results in these cases. Especially the possibility to use “memory” of preceding days – potentially featuring less clouds – seems promising in this respect. Furthermore, it will be elaborated if the option of overwriting existing observational data with values better fitting the patterns learned by the CNN is suitable to improve the overall results and hence may be an alternative to external (manual) quality control and plausibility checking.The final aim of this study is to establish an approach suitable for the operational analysis of daily SSTs with a horizontal resolution of approx. 5 km and the production of an SST reanalysis of North Sea and Baltic Sea SSTs starting in 1990.
Spectral ratioing of Afρ to constrain the particle size distributions of comets
Authors: Haslebacher Nico , Thomas Nicolas , Marschall Raphael
Published: March 2024

Introduction: Afρ is a measure for the brightness of a cometary coma [1]. In the past, Afρ has been commonly used as a proxy for the activity of comets [2]. In later studies it was found that the brightness of a coma (Afρ) is dominated by the particle size distribution [3] and that Afρ on its own is a poor predictor for the activity of a comet [4]. In this work we use a numerical model of cometary dust environments to get a better understanding of the relationship of Afρ and the particle size distribution and show how spectral ratioing of Afρ could provide constraints for the particle size distributions of comets.
Methods: A numerical dust model is used to calculate the expected Afρ at two different wavelengths for a wide range of different parameters. Specifically, we calculate the ratio Afρ (425 nm) / Afρ (900 nm) in dependence to the power-law index of the particle size distribution. It is implicitly assumed that the particle size distribution follows a simple power-law. We use particles sizes in the range of 0.01 µm to 10 cm and choose  logarithmic particle size bins that are small enough to have a converging result. The scattering properties of each particle size are calculated for three different dust compositions. We use water ice to model bright particles, enstatite to model silicate particles and amorphous carbon to model dark particles. The scattering properties are calculated based on Mie-theory. Further, we studied day-night asymmetries, parameters related to the outflow velocity of the dust and phase angle effects.
Results: We show that the spectral ratio of Afρ modelled at 425 nm and 900 nm correlate with the power-law index of the particle size distribution. Large particle dominated comas can be distinguished from small particle dominated comas. For small particle dominated coma the specral ratio of Afρ can be used to further constrain the power-law index.
Acknowledgments: This work has been carried out within the framework of the National Centre of Competence in Research PlanetS supported by the Swiss National Science Foundation under grants 51NF40_182901 and 51NF40_205606. Additional financial support from the European Space Agency is also acknowledged.
References: [1] A’Hearn, M. F. et. al. (1984), AJ, 89, 579 [2] Weiler, M. et. Al. (2003), A&A, 403, 313 [3] Fink, U. and Rubin, M. (2012), Icarus, 221, 721 [4] Marschall, R. et. al. (2022), A&A, 666, A151
 
Lake SkyWater - a portable optical buoy for easily measuring water-leaving radiance in lakes based on the skylight-blocked approach (SBA)
Authors: Coqué Arthur , Peroux Tiphaine , Morin Guillaume , Tormos Thierry
Published: March 2024

Spaceborne optical sensors are a useful tool for monitoring water quality in oceans, lakes and rivers on a large scale, at high frequency and at relatively low costs. Based on water colour algorithms, many key biogeochemical parameters are operationally estimated from satellite data (e.g. chlorophyll-a concentration). Calibrating and validating these algorithms requires a huge collection of high-quality in situ radiometric data, such as the water-leaving radiance Lw (or the remote sensing reflectance Rrs), necessitating high-level expertise and expensive material.One of the most robust methods to measure Lw is the skylight-blocked approach (SBA), which allows Lw to be measured directly at the air-water interface. Compared with the conventionnal “above-water” method, the measurement is not contaminated by light reflected from the surface (including both sky- and sun-glint), thanks to the use of a cone-shaped screen attached to the downward-facing radiance sensor (which measures Lw) that fully blocks all downward radiance at the air-water interface.Our open-source system “Lake SkyWater” was designed around the idea of making in situ radiometry measurements in lakes user-friendly and affordable, while retaining the accuracy and robustness required for scientific and operational purposes. We have created a semi-autonomous buoy that implements the SBA method. Lake SkyWater is low-cost (
Mitigating greenhouse gas emissions from managed organic soils in the temperate zone by paddy rice cultivation
Authors: Widmer Alina , Tamagni Lisa , Wüst-Galley Chloé , Paul Sonja , Volpe Valerio , Jocher Markus , Giger Robin , Dötterl Sebastian , Keller Thomas , Leifeld Jens
Published: March 2024

Large areas of European peatlands have been drained for agriculture, but drained organic soils are a strong source of carbon dioxide (CO2). Reinstalling high water tables would inhibit further peat oxidation and reduce CO2 and nitrous oxide (N2O) emissions, but most cash crops do not grow in waterlogged conditions. Paddy rice cultivation could offer a new option for continuing the agricultural use of these soils under wet conditions. However, paddy rice cultivation is known to be a strong source of methane (CH4), which might cancel out the potential climate benefit from reduced CO2 and N2O emissions. The main aim of this study was, therefore, to quantify for the first time the greenhouse gas (GHG) balance of paddy rice grown on organic soil in the temperate climate zone of the Swiss Plateau.In an outdoor mesocosm experiment, we measured the greenhouse gases CO2, CH4, and N2O with manual chambers on a weekly to biweekly interval for one year. During the experiment, rice (Oryza sativa L.) was cultivated under flooded conditions with mid-season drainage on organic soil. As a reference treatment, ley was grown on drained organic soil (water table -100 cm).Preliminary results from the growing season (April - October) including planting and harvest suggest that the overall GHG balance of paddy rice cultivation on organic soil (9.3 ± 1.9 t CO2 eq. ha-1 including harvest exports) was significantly lower than of ley grown on drained organic soil (27.9 ± 5.0 t CO2 eq. ha-1 including harvest exports). This difference was mainly attributed to the strong reduction in ecosystem respiration under flooded conditions compared to ley on drained organic soil. Paddy rice cultivation was a source of methane (49.2 ± 19.7 kg CH4 ha-1), while the drained organic soil covered with ley was a CH4 sink (-0.6 ± 0.1 kg CH4 ha-1). The flooded conditions in the paddy rice mesocosms significantly lowered N2O emissions (0.7 ± 0.3 kg N2O ha-1) compared to drained grassland (4.7 ± 3.1 kg N2O ha-1). N2O and CH4 accounted for 16.0 ± 6.8 % of the total GHG balance in the rice on organic soil treatment, whereas it was only 4.9 ± 2.6 % in the ley on drained organic soil.Together, we show that paddy rice cultivation on organic soil is a valid alternative to upland agriculture in the temperate zone and offers significant GHG emission reduction potentials.
Subsurface biosphere, pore water geochemistry and mineral biosignatures along the 1 Ma sediment archive of ferruginous Lake Towuti, Indonesia
Authors: Kallmeyer Jens , Ruiz-Blas Fátima , Henny Cynthia , Russell James , Vogel Hendrik , Vuillemin Aurèle
Published: March 2024

Ferruginous conditions prevailed in the oceans through much of Earth’s history. However, past biogeochemical cycling inferred from mineral components in ancient iron formations remain poorly constrained in terms of microbial processes prior to lithification. In Lake Towuti, Indonesia, ferruginous sediments are deposited under stratified conditions that mimic the Earth’s early oceans. Over geologic time, Lake Towuti experienced dynamic redox conditions, resulting in variable ferric and organic matter fluxes feeding microbial life at the lake floor. Although environmental conditions exert control over microbial assemblages at the time of deposition, geochemical evolution of these substrates select for specific groups of microorganisms capable of maintaining metabolic activity during entombment.The 100 m long core retrieved by the ICDP Towuti Drilling Project allowed for investigations of the subsurface biosphere, pore water geochemistry and diagenesis of iron minerals. We established the abundance and phylogenetic distribution of microorganisms along the 1 Ma stratigraphic record, and created integrated environmental and geochemical datasets in order to identify the main taxa and metabolic features involved in sediment mineralization. Ferruginous conditions predominantly selected for Bathyarchaeia. Relevant metabolisms identified from metagenome-assembled genomes indicated sulfur transformation and (homo)acetogenesis, suggesting that heterotrophic dark carbon fixation and cryptic sulfur cycling linked to iron minerals may be prominent features of microbial life in this ferruginous system.Changes in environmental processes and conditions lead to variability in metal and organic substrate concentrations with depth, while sustaining different microbial processes in various depth intervals. Geochemical profiles reflect microbial activity after deposition and demonstrated mineral precipitation induced by microbial mineralization. Precipitation of magnetite (Fe3O4), millerite (NiS), siderite (FeCO3), and vivianite (Fe3[PO4]2 · 8H2O) from pore water constitute biosignatures of microbial iron and sulfate reduction, fermentation and methanogenesis. For example, oxygen, iron, and carbon isotopes measured on siderites enabled us to differentiate between depositional and diagenetic signals. Siderite δ18O signatures reflected in-lake hydrological fluctuations. Low negative δ56Fe values recorded periods of water column stratification and oxygenation events, with minor diagenetic redistribution. Negative δ13C signatures reflected incorporation of biogenic HCO3- during organic matter fermentation, whereas positive δ13C excursions indicated mass balance due to increased production of biogenic methane.
Denudation and weathering rates from meteoric 10Be/9Be: A versatile tool in mafic, carbonate or slate-dominated lithologies from the critical zone to very large catchments 
Authors: Wittmann Hella , Bouchez Julien , Deng Kai , Gaviria-Lugo Nestor , Bernhardt Anne , von Blanckenburg Friedhelm
Published: March 2024

Meteoric 10Be is a cosmogenic nuclide produced in the atmosphere and delivered to Earth’s surface by precipitation, whereas stable 9Be is a trace metal released from bedrock during weathering. The ratio (10Be(meteoric)/9Be) is set in the critical zone, where beryllium is either adsorbed to fine-grained sediment or is dissolved in water if the pH-dependent retentivity of Be is low. A prerequisite for calculating denudation and weathering rates over millennial timescales is knowledge of the flux of 10Be deposition to Earth surface and the concentration of 9Be in the unweathered parent bedrock. We provide a review of applications of the 10Be/9Be system to Earth surface studies that covers a variety of quartz-bearing rocks, lithologies largely void of quartz like mafic rocks, mixed lithologies, and, most recently, carbonate and marble lithologies. We show the versatility of this new approach in several case studies. These range from small creek-scale mafic basins in the European midlands, medium-sized (102-103 km2) catchments covered by slate and marble in the rapidly eroding Taiwan Island, pure carbonate rocks from the French Jura Mountains, to large catchments draining mixed lithologies in the Chilean Andean Cordillera and the Amazon and Ganga river basins. We find that i) across all spatial scales, the dissolved and sediment-bound 10Be/9Be ratios agree well, indicating equilibrium of phases. Approximately at medium-sized catchment scales, ii) the 9Be concentration from published databases from typical parent rocks (http://earthref.org/GERM) represents the local bedrock 9Be concentration, but for much smaller and carbonate catchments, a locally representative bedrock concentration has to be determined on a case-by-case basis; and iii) local measurements of the depositional 10Be flux from the 10Be inventory of independently-dated deposits like e.g. terrace profiles appear to yield the most reliable estimates. Under these constraints, derived denudation and weathering rates agree in all settings to within less than a factor of 2 with either decadal-scale denudation rates from combined suspended and dissolved river fluxes or with in situ-10Be-derived denudation rates where quartz is present. This close agreement shows that 10Be/9Be ratios from such rock types yield meaningful denudation rates obtained from sub gram-sized amounts of sediment, independent of the spatial scale of sampling ranging from a single soil profile to the scale of the Amazon river basin. Small sample amounts and the independence of the presence of quartz provide a benefit over the “sister” nuclide in situ 10Be that has been widely used in landscapes of felsic rocks. Now, with 10Be/9Be, the determination of rates of Earth surface change in quartz-poor lithologies opens up entirely new opportunities.
Climate Horizons: a graphic novel of key IPCC findings to reach a wider audience
Authors: Dion Iris-Amata , Henrion Xavier
Published: March 2024

For over 30 years, the Intergovernmental Panel on Climate Change (IPCC) has been synthesizing the state of scientific knowledge on global climate change and communicating it through a series of reports. These reports highlight both the responsibility of humans in triggering this rapid climate change and the direct threat it represents for living organisms including humans. However, despite being freely available to all, many still lack basic understanding of the climate system and the associated anthropogenic forcings. One explanation to this is that these reports are not made intelligible to people outside the academic world and the decision-making sphere. The graphic novel format offers the advantage to blend art and science, making it easier for non-scientific readers to access the information contained in the IPCC reports. Therefore, we proposed an alternative way of presenting the IPCC findings through the collaboration between a climate scientist and a cartoonist. We interviewed 9 authors of the three main IPCC working groups to present the content of these reports in an accessible and intelligent graphic novel named Climate Horizons. In the story, two main characters engage in a dialogue with these IPCC co-authors allowing them to discover the complexity of natural ecosystems, climate inaction and political power struggles. While explaining their field of study, each author shares a vision of what their role as geoscientists should be in the face of urgent climate and environmental issues. Over the course of the story, the main characters gradually change the way they see the world, and go through a range of emotions (shock, denial, anger, acceptance, etc.) as they become aware of the major problem of climate change.This approach by committed citizens and researchers responds to the need to be informed about possible solutions and encourages individual and collective reflection to imagine new possible horizons.