bluuebunny/crossref_metadata_2025 huggingface dataset:
At the bottom of ice streams: unraveling the physics of sliding onset through a glacier-scale field experiment
Authors: Mantelli Elisa , Drews Reinhard , Eisen Olaf , Farinotti Daniel , Luethi Martin , Mingo Laurent , Schroeder Dustin , Vieli Andreas
Published: February 2023

Fast ice stream flow at speeds of hundreds to thousands of meters per year is sustained by sliding at the ice sheet base, whereas slow flow outside of ice streams is characterized by limited-to-no basal sliding. In this sense, the transition from no sliding to significant sliding exerts a key control on ice stream flow. The detailed physical processes that enable the onset of basal sliding are somewhat debated, but laboratory experiments, recent theoretical work, and a handful of direct observations support the notion of sliding initiating below the melting point as a result of regelation and premelting. In this contribution we describe a recently funded glacier-scale field experiment that has been designed to advance the understanding of sliding onset physics by testing the hypothesis that sliding starts below the melting point. The experiment will take place at the Grenzgletscher (Swiss Alps), which is known to have a cold-based accumulation region and a temperate-based ablation region. Our work will involve extensive surface geophysics (radio echo sounding, terrestrial radar interferometry, radar thermal tomography) aimed at identifying the sliding onset region. This work will guide the site selection for a subsequent borehole study of englacial deformation that is meant illuminate the relation between sliding velocity and basal temperature. The borehole work will allow us to test systematically the hypothesis that sliding starts below the melting point through an extended region of temperature-dependent sliding, and possibly to advance the formulation of temperature-dependent friction laws that are used to describe the onset of sliding in ice flow models.The focus of this contribution will be specifically on the experimental design - how it is informed by existing theory and observations, and how it will support theoretical and ice flow modeling advances, at the glacier scale and beyond.
The sensitivity of urban surface water flood modelling to the temporal structure of rainfall
Authors: Asher Molly , Trigg Mark , Birch Cathryn , Böing Steven , Villalobos-Herrera Roberto
Published: February 2023

The risk posed globally by surface water flooding to people and properties is growing due to rapid urbanisation and the intensification of rainfall due to climate change. Whilst tools to model urban flood risk have also been rapidly developing, there remains a knowledge gap around the sensitivity of urban hydraulic modelling methods to the temporal structure of rainfall. In the UK, the industry standard process considers rainfall events to always be symmetrical, and with a singular peak in intensity. Previous studies of observed UK extreme rainfall events suggests that loading of rainfall towards the start or end of events is in fact more common. In this study, the sensitivity of an urban catchment in the north of England is tested using fifteen realistic rainfall profiles derived from these observed extremes. Additionally, idealized systematic variations are made to the industry standard profile to shift the single peak towards the start or end of the event, and to split the rainfall volume over multiple peaks. We demonstrate that the positioning of the peak, as well as its magnitude, influences the severity, timing and nature of the associated flooding. The profile with the peak nearest the end of the event is associated with an 18% larger flooded area than the early peaking profile which is associated with the smallest flooded area.
WRF modeling of the UTLS region of the July 29 2016 summer monsoon storms in China and comparison with aircraft and satellite observations
Authors: Wang Pao K. , Chou Yen-Liang , Lindsey Dan
Published: February 2023

Deep convective storms represent the fastest vertical transport mechanism of both momentum and chemical species from the surface to the middle atmosphere, and these transports may potentially impact strongly the global atmospheric and climate processes. For example, the water vapor transported through the tropopause into LS may exert substantial radiative forcing due to its strong capability in intercepting terrestrial IR. Due to the difficulty in the in situ observation in the storm top region, most previous studies rely on remote sensing data whose interpretation can be ambiguous. Consequently, many details of the transport process remain unclear. On July 29, 2016, we encountered a line of convective storms along the coast of China from about Lat 35°N to Lat 22°N during a flight onboard of a commercial aircraft and made many photographic records of the storm tops that exhibited strong internal gravity wave (IGW) features. The visible satellite images of these coastal storms were retrieved from Himawari-8 archive and made into a loop. The simultaneous availability of both aircraft and satellite observations makes this episode a rare case for improving our understanding of the UTLS dynamics.We performed WRF simulation of this case with a domain as illustrated in Fig. 1(a) and the results compare favorably with the satellite observations. We are analyzing the results to understand especially the vertical structure and the IGW, thermodynamics and mass transfer processes in the UTLS region (Fig. 1(b)). We will use the aircraft and satellite observations to substantiate the model interpretation of the storm top processes. The animations of model results and satellite loops provide a clear picture of deep convection dynamics in UTLS. We will also discuss the potential global impact of these processes.
Microplastics in sediment deposited along the Seine River after a major flood event (February 2021)
Authors: Bouzid Nadia , Bizeul Remi , Foucher Anthony , Ayrault Sophie , Evrard Olivier , Dris Rachid , Tassin Bruno , Gasperi Jonnhy
Published: February 2023

Depending on hydrodynamic conditions, river sediments act as a sinks or a sources of microplastics through deposition and remobilisation processes. During flood events, the increase of river flow leads to an increase in the resuspension of bottom sediments and bank erosion processes and favoring the microplastic transportation. Previous work conduced in the Seine river catchment in 2018 has shown that floods, which occur for only 15% of the annual time, contributed to 40% of the total microplastic flux. Therefore, at the end of a flood period, with the decreasing in water level, some flow regimes allow the deposition of contaminated sediments carried by the river on the banks.This study presents the characterization and quantification of microplastics in ten samples lag deposits collected along the Seine river after the February 2021 flood event. Microplastics from 10 to 500 µm were analysed in replicate samples using two methods (FTIR microspectroscopy and Pyr-GC/MS). In order to characterize the origin of the sampled sedimentary deposits a fingerprinting approach based on the measurement of radionuclides activity (137Cs, 210Pbex and 7Be) was carried out. A mixing model was applied to discriminate old and recent sediments and their origin from the surface (e.g. soil erosion) or subsurface (e.g. bank erosion). High concentration levels of microplastics, ranging from 8,000 to 50,000 items/kg, were observed mainly characterised by FTIR microspectroscopy as PP, PE, PS and PVC. All the samples analysed show a similar size distribution with a majority of particles below 100 µm. PP is the most abundant polymer found. The quantification by Pyr-GC/MS provided masses consistent with microspectroscopy results ranging from 200 to 14,000 µg PP/kg of dry sediment.  An increase in microplastic contamination between the upstream and the downstream part of the Paris area was observed. In this study, the relationships between sediment characteristics and microplastic contamination could not be demonstrated. Further work is needed to verify whether a more marked relationship can be observed in major events where a clearer variation in sediment sources is observed between the upper and lower parts of the Paris area.
Comparisons and possible combinations of time-wise and space-wise approaches for satellite gravity missions data processing
Authors: Vitti Alfonso , Tesolin Francesca , Reguzzoni Mirko , Rossi Lorenzo , Koç Öykü , Batsukh Khulan , Albertella Alberta , Migliaccio Federica
Published: February 2023

Dedicated satellite gravity missions, such as GOCE, GRACE and GRACE-FO, have been providing essential data for many geodetic and geophysical studies and applications. In the next future, new missions exploiting technological advances and innovative observation principles will be proposed, thus requiring numerical simulations to assess their performances in recovering information on the Earth gravity field. This is typically done by simulating the satellite orbits and propagating the instrumental noise to the error covariance matrix of the spherical harmonic coefficients. Of course, this propagation also depends on the processing techniques. Among them, approaches based on time-wise strategies are devised to directly map the time series of observations to spherical harmonic coefficients, while the approaches based on space-wise strategies are focused on the location of observations estimating the coefficients by some local analysis. In this work we compare a time-wise approach with a space-wise approach for the data analysis of possible future gradiometry missions, for example those based on quantum technology and based on the satellite tracking concept (pair or double pair of satellites, such as NGGM/MAGIC). The time-wise approach basically works in the Fourier transform domain, thus making the simulation very efficient from the computational point of view at the cost of some simplifications, e.g., in the data regularity and in the orbit repetition period. The time-wise approach permits a formal error propagation of realistic instrumental noise power spectral densities. On the other hand, the space-wise approach is focused on projecting the observed gravity information onto a spherical grid and then solving the boundary value problem to estimate the spherical harmonic coefficients. In estimating the grid values, the space-wise approach directly works in the space domain where a collocation method on local patches of data can be exploited for adapting the estimation to the local/regional characteristics of the gravity field. Differently from the time-wise approach, a formal error propagation from the instrumental noise power spectral densities is not feasible, e.g., for the limitations in modelling the error cross-correlation of grid nodes estimated from different data patches. Therefore, the overall error assessment relies on a Monte Carlo simulation. In this study, several numerical simulations are presented to emphasize the pros and cons of the two methods, as well as possible combination strategies to be exploited in studies of the time-variable models of the Earth gravity field.
Towards monitoring volcanic hydrothermal alteration using geophysical approaches
Authors: Caudron Corentin , Lecocq Thomas , Yates Alexander , Dempsey David , Ardid Alberto , Hermans Thomas , Vanhooren Lore , Fontaine Olivier , Bultreys Tom , Girona Társilo
Published: February 2023

Most volcanoes on Earth host a volcano-hydrothermal system. Lying between the surface and magma reservoirs, they exert a dramatic influence on volcano dynamics. Understanding their behavior is however challenging because of the complex interplay between gas, liquid, and rocks. Volcanic gas can, for example, be completely scrubbed through interactions with groundwater whereas the kinetics of these reactions are controlled by thermodynamic conditions that are poorly constrained. While fluid circulation gives rise to a range of geophysical signals such as ground vibrations, self-potential, or variable resistivity observable at the surface, their complex dynamics complicate the isolation of pre-eruptive signals and the interpretation of the observed volcanic activity. Indeed, some volcanoes remain on alert for months or years without experiencing any eruption. Such situations severely affect the credibility of the agencies in charge of monitoring volcano activities.In this contribution, we will focus on multi-disciplinary efforts to better characterise the time evolution of these complicated systems. Our ultimate goal is to deconvolve the contribution of dynamic processes occurring in such systems (temperature, gas saturation, alteration, precipitation) to possibly facilitate real-time monitoring efforts. Our examples come from different parts of the world, in both hemispheres.
GIS-based morphotectonic and geomorphometric assessment for the Moroccan High Atlas mountain ranges, Morocco.
Authors: Argyriou Athanasios V. , Skikra Hamza , Amrouch Khalid , Soulaimani Abderrahmane
Published: February 2023

The geomorphological and tectonic processes being responsible for the control of the mountain ranges geometry is feasible to be assessed through geomorphological and morphotectonic indices. Those indices are dependent on tectonic or erosional processes and other factors influencing the development of the landforms. Tectonic geomorphology applications using satellite-based remotely sensed data, such as Digital Elevation Models (DEMs), can highlight specific geomorphic features capable to provide useful information and knowledge towards the evaluation of the regional tectonic activity in mountain ranges. This study examines the Moroccan High Atlas mountain range by using morphotectonic and geomorphometric indices such as the channel steepness index, amplitude of relief index, stream length gradient index, swath profiles, local relief and hillslope mapping to determine the distribution of the tectonic activity variations. Through those indices the evaluation of the geomorphic responses to tectonics takes place by highlighting the relationships between tectonic activity, rock resistance, stream channel slope, active or recent vertical displacements. The outcomes of the geomorphometric and morphotectonic investigation highlight the presence of considerable geomorphic variations across the main fault zones featuring the orogen’s anatomy, while tectonic activity seems to be a major factor controlling and shaping the Moroccan High Atlas mountain range landscape. The methodological framework of this study could be developed into a low-cost technique for assessing seismic hazard, offering a valuable tool towards assessing disaster risk reduction activities, whereas in conjunction with other factors the georesources exploration.  AcknowledgementsThe corresponding author acknowledges the 'EXCELSIOR': ERATOSTHENES: Excellence Research Centre for Earth Surveillance and Space-Based Monitoring of the Environment H2020 Widespread Teaming project (www.excelsior2020.eu). The 'EXCELSIOR' project has received funding from the European Union's Horizon 2020 research and innovation programme under Grant Agreement No 857510, from the Government of the Republic of Cyprus through the Directorate General for the European Programmes, Coordination and Development and the Cyprus University of Technology.
Reaching SDGs 6.1 and 6.2 in Kazakhstan: State - society relations
Authors: Tussupova Kamshat , Zhupankhan Aibek
Published: February 2023

Science - policy - society Nexus is important in achieving Sustainable Development Goals (SDG). The current scientific knowledge is sufficient to allow us to implement the best of knowledge to cover the basic needs such as access to safe water and sanitation; however, the implementation rate is slow. Thus, this work looks at state-society relations in reaching SDGs 6.1. and 6.2. in Kazakhstan.The survey asssessed available 176 water-related functions in the Government of Kazakhstan using the Integrated water resources  management tool-box. Additionaly, the questionnaire of about 1300 villagers was conducted in all the villages (which are 153 in total) of Atyrau region, Kazakhstan during September-November 2022, to assess the access to drinking water and sanitation services and the needs for improvement.The findings show that in the “Policy” area the functions for adaptation to climate change are poorly expressed, especially climate resilient WASH systems; the role of customary law in the field of both the use of water resources and access to drinking water and sanitation is barely reflected in the legislation. In the "Organization" area there is a lack of functions in operation and monitoring of decentralized water supply and sanitation services; the organization of civil society is not formally expressed; training of water management specialists is not reflected as a responsibility.  In the field of using various tools of Integrated Water Resources Management, the weakest function of the government is communication with society and their reflection in public policy, in particular, the introduction of the concept of virtual water, water footprint, public awareness and education; economic instruments and effective demand management are little reflected in the functions of the state.More than half of rural citizens use water from decentralized sources and mainly use pit latrines. The field survey has showed the high level of responsibility of the local villagers for decentralized sanitation and drinking water supply services, with high request to be educated on how to maintain those systems in a more sustainable way. It might be concluded that people do have relatively high rate of responsibility to maintain the water supply and sanitation systems. However, the policy and the govenmental functions do lack meeting these societal needs for education and, in a broder context, integrating people into water projects. "The science" or Reserchers could play an important role bridging State and Society to increase the feasibility of water and sanitation state-run programs.   
Seasonality and regionality of the vertical structure of the water column in the Arctic Ocean.
Authors: Gutierrez-Loza Lucia , Lauvset Siv K.
Published: February 2023

The Arctic Ocean is rapidly changing in response to high temperatures and increased atmospheric greenhouse gas concentrations.  As part of these changing conditions, sea-ice loss and increased freshwater inputs are expected to impact the mixing processes and the characteristics of water column in the Arctic region, directly modulating the nutrient availability and primary productivity in the surface water.Here, we investigate the spatial and temporal variations of the vertical structure of the water column using high-resolution model outputs for the period 2000-2099. We focus on the Atlantic sector of the Arctic, an increasingly temperature-stratified region, where we evaluate the changes on nutrient availability and carbonate chemistry in the upper ocean. Changes in the regionality and seasonality under a medium- to high-end emission scenario (SSP3-7.0), transitioning towards a sea-ice free Arctic, will be used to further understand the upper ocean mixing processes and their impacts on the local and regional biogeochemistry.
Roles of peroxy radicals and Criegee intermediates in β-pinene ozonolysis at different temperatures
Authors: Gong Yiwei , Saathoff Harald , Jiang Feng , Li Yanxia , Leisner Thomas
Published: February 2023

Organic peroxy radicals (RO2) and stabilized Criegee intermediates (SCIs), as important reactive species in the atmosphere, are critical in oxidation processes and secondary organic aerosol (SOA) formation. However, the influence of temperature on these reactive intermediates and the corresponding reaction mechanisms in SOA formation is still not well defined. In this study, through utilizing SCIs scavengers and regulating [HO2]/[RO2] from ~0.3 to ~1.9, the roles of RO2 and SCIs in SOA formation were investigated at 298 K, 273 K, and 248 K, respectively, particularly for dimers formation in β-pinene ozonolysis. It was found that the dependence of the SOA yields on temperature was not monotonic. With the temperature decreasing from 298 K to 273 K, the SOA formation was promoted by the gas-particle partitioning of semi- and low-volatility products. However, when the temperature further decreased to 248 K, the SOA yields were lower due to the temperature effect on chemical reactions. The addition of SCIs scavengers showed that SCIs reactions accounted for more than 40% of both dimers and aerosol formation under all temperature conditions. The SCIs reactions predominantly contributed to the formation of C18 and C19 dimers. Increasing the [HO2]/[RO2] ratio suppressed SOA and dimers formation at all temperatures, indicating that in β-pinene ozonolysis RO2+RO2 reactions generate products of lower volatility, while RO2+HO2 reactions tend to form products of higher volatility. The lower RO2 concentrations and suppressed RO2+RO2 reactions could partly explain the reduced SOA yield at 248 K. Additionally, it was found that the sensitivity of dimers formation on [HO2]/[RO2] was higher at lower temperatures. Even though the impact of temperature on the reaction coefficients of peroxy radicals was considered, the dimers formation at different [HO2]/[RO2] ratios could not be explained well at 273 K and 248 K. This suggests that SCIs reactions with RO2 radicals may become more important at lower temperatures due to slower isomerization and decomposition of SCIs.
Compositional and textural tephra characteristics of the 1970 eruption at Deception Island (Antarctica): Implications for volcanic hazards
Authors: Hopfenblatt Joaquin , Geyer Adelina , Aulinas Meritxell , Polo-Sánchez Antonio , Pedrazzi Dario , Álvarez-Valero Antonio M. , Vilanova Oriol , Pallàs Raimón , Casas Josep M.
Published: February 2023

Deception Island is the most active volcano in the South Shetland Islands (Antarctica) with more than 20 explosive eruptive events registered over the past few centuries. The most recent eruption (August 1970) was severely violent with a volcanic explosivity index (VEI) of 3. The column height reached 10 km at its maximum, the estimated bulk eruptive volume was > 0.1 km3 and tephra fallout was reported as far as in King George Island (> 150 km distance). In this work, we perform a compositional and textural analysis of the 1970 tephra layers found at Livingston Island’s glaciers (between 25 and 40 km distance from Deception IsIand). Results obtained are then compared to the in situ pyroclastic deposits of the diverse vents active during this eruption. The objective is to establish a correlation between the eruptive phases occurred during the 1970 event and the physicochemical features observed in the tephra deposits. This will be used as a starting point for future studies of tephra layers found in glaciers and marine/lacustrine sediment cores outside the island, improving our capacity to reconstruct the eruptive dynamics of past eruptions. These results are fundamental to: (i) determine the size and explosiveness of past eruptive events; (ii) assess the extent of their related hazards (e.g., ash fall out); (iii) complete the eruption record of the island; and (iv) consequently, perform more accurate hazard assessments at the island. This is of special concern, since the South Shetland Islands are an important tourist destination and host numerous year-round and seasonal scientific stations and base camps. This work is part of the CSIC Interdisciplinary Thematic Platform (PTI) Polar zone Observatory (PTI-POLARCSIC) activities. This research was partially funded by the MINECO VOLCLIMA (CGL2015-72629-EXP) and HYDROCAL (PID2020-114876GB-I00) MCIN/AEI/10.13039/501100011033 research projects. Sampling was founded by CICYT (ANT91-1270, ANT93-0852 and ANT96-0734).
Strengths and limitations of using radiogenic isotope signatures of marine sediments from Baffin Bay for the reconstruction of ice dynamics and paleoenvironments in the Canadian Arctic and Greenland
Authors: Hingst Johanna , Lucassen Friedrich , Hillaire-Marcel Claude , Kasemann Simone
Published: February 2023

Radiogenic Sr, Nd, and Pb isotope compositions in marine sediments are widely used as provenance tracers delivering valuable information about past environmental conditions. Over the last ten years, several studies performing radiogenic isotope analysis on marine sediment records from Baffin Bay and Labrador Sea highlighted the strength of this method in shedding light upon past glacier dynamics and related environmental changes in Greenland and the Canadian Arctic. The main outcomes of our studies include precise information on the opening of Arctic gateways and the setting of oceanic connection from the Arctic Ocean to the Atlantic through Baffin Bay. At a more regional scale, these tracers document the late glacial to Holocene dynamics of Baffin Island glaciers, helping to understand how climate and oceanic conditions impacted glacier margin fluctuations. As importantly, our study also highlighted limitations in the sensitivity of radiogenic isotopes from Baffin Bay marine sediments as tracers. Most important for interpreting radiogenic isotope compositions is the availability of a sufficiently dense cover of their properties in bedrock and reference isotope signatures from such remote areas to better resolve potential sediment sources. Another challenge for sediment records obtained from core sites at near-proximity to ice margins is the effect of glacier dynamics on the sediment composition. Intense meltwater discharge can lead to grain size and mineral sorting, which could bias the radiogenic isotope composition of the sediment. Nonetheless, radiogenic isotopes present a significant advantage over lesser availability tracers, such as biological proxies, which can be restricted due to the harsh climate conditions. In several cases, radiogenic isotope analysis also reveals more information about sediment provenance than mineralogical assemblages. All in all, in combination with sedimentological and mineralogical features, the radiogenic Sr, Nd, and Pb isotope compositions of Arctic marine sequences can be used as reliable tracers for changes in sediment provenance.
Patterns and cyclicity of Quaternary sedimentation above a subducting seamount at Rock Garden (central Hikurangi Margin, New Zealand)
Authors: Schwarze Cornelius , Frenzel Peter , Kukowski Nina
Published: February 2023

Rock Garden (RG), located east off the North Island of New Zealand, is part of an accretionary ridge that is influenced by seamount subduction. Two ∼37m long sediment cores, drilled with the seafloor drill rig (MeBo200) from RG, provide a continuous sedimentary record of the period between 1.95-0.4 Ma. This period, the Early-Middle Pleistocene transition (EMPT), was marked by a progressive increase in the amplitude of climate oscillations and a shift of Milanković cycles from 41 ka towards a quasi-100 ka frequency in the absence of any significant change in orbital forcing. From the recovered core material of cores GeoB20824-4 and GeoB20846-1, we determined sediment physical properties, oxygen isotope (δ18O) values, and element concentrations based on X-ray fluorescence (XRF) measurements. The element ratios were used as proxies for sediment composition and as paleoenvironmental indices. In sediment physical properties, δ18O values, and geochemical properties, evidence for glacial and interglacial cycles and cyclicities of 405 ka, 100 ka, 41 ka were found. A shift of the cyclicity from 41 to 100 ka took place in sediment cores during (1.4-0.4 Ma). Numerical ages obtained from tephra layers included in the sedimentary record enabled to estimate sedimentation rates from both cores. Although both drill sites are only 1800 m away from each other, sedimentation rates of 2.15-2.96 cmka−1 (GeoB20824-4) and 5.49-6.77 cmka−1 (GeoB20846-1), respectively, differ by a factor of two. This may be the reason why two facies-units were identified in core GeoB20824-4, whereas sediments of core GeoB20846-1 all belonged to the same facies. A change of lithofacies in core GeoB20824-4 between Unit I and Unit II in ∼20 mbsf at 1.5-1.4 Ma marks the initiation of the EMPT.
Causes of uncertainty in simulated burnt area by fire-enabled DGVMs
Authors: Forrest Matthew , Burton Chantelle , Drüke Markus , Hantson Stijn , Li Fang , Melton Joe , Nieradzik Lars , Rabin Sam , Sitch Stephen , Yue Chao , Hickler Thomas
Published: February 2023

Fire-enabled dynamic global vegetation models (DGVMs) can be used to study how fire activity responds to its main drivers, including climate/weather, vegetation and human activities, at coarse spatial scales. Such models can also be used to examine the effects of fire on vegetation, and, when embedded in Earth system models, investigate the feedback of fire on the climate system. Thus they are valuable tools for studying wildfires. Accordingly, the Fire Model Intercomparison Project (FireMIP) was established to evaluate and utilise these models using consistent protocols.Here we present the second round of FireMIP simulations to focus historic wildfire drivers (1901 to present). A six-member ensemble of simulations from fire-enabled DGVMs was compared to remotely-sensed burnt area observations and to the previous round of historical FireMIP simulations. We found that the model skill when simulating spatial patterns of burnt area shows modest improvements compared to the previous FireMIP round, and that the simulations mostly reproduce the decreasing trend in global burnt area found over the last two decades. However, whilst the broad global patterns are reasonable, there are considerable discrepancies with regards to regional agreement and timing of burnt area. Furthermore, the models show diverging trends in the pre-satellite era.To investigate further and inform future model development, we explored the residuals between simulated burnt area from the FireMIP models and remotely-sensed burnt area as a function of climate, vegetation, anthropogenic and topographic variables using generalised additive models (GAMs). We found some common responses across the models, with many over-predicting fire activity in arid/low productivity areas and all models under-predicting at low road density. However, with respect to other variables, such as wind speed and cropland fraction, the models residuals showed divergent responses. It is anticipated that these results should aid further development of global fire models in terms of driving variables, process representations and model structure.
Titan's tail structure: the multi-instrument study as observed by Cassini
Authors: Kim Konstantin , Edberg Niklas , Shebanits Oleg , Wahlund Jan-Erik , Vigren Erik
Published: February 2023

Titan’s  magnetotail is formed as a result of the interaction of Saturn’s magnetospheric flow with Titan’s ionosphere. While the ionosphere is created mainly by EUV radiation and impinging magnetospheric particles on the atmosphere, the tail is more governed by plasma outflow processes, the upstream magnetospheric flow properties (density, flow velocity) and the upstream magnetic field direction. The properties of Titan’s tail has previously been studied with both numerical simulations and in-situ measurements. For instance,  the escape rate has been shown to be of the order  of order ~1024 s-1, and case studies have revealed a highly dynamic tail structure.In this work we make an attempt to combine observations of electrons and ions in Titan’s tail for all of the Cassini flybys. We use the Langmuir probe (RPWS/LP) and the Cassini Plasma Spectrometer (CAPS) ion and electron measurements. We put a spatial constraint on the tail’s geometry  and its orientation based on the measurements of electron and ion densities. The estimation of escape rate is revisited, and different sources of variability and their impact on the tail structure are discussed. Furthermore, the link between the convectional electric field E = -v×B and the electron densities distribution is studied. The interim result is that the electron density tends to have higher densities in the hemisphere of positive upstream electric field. This is observed in the altitudes below the dynamo region, which is the chemistry-dominated region. The explanation of the observed distribution tendency is discussed.
Modelling the coevolution of London's population and railway system
Authors: Capel-Timms Isabella , Levinson David , Bonetti Sara , Manoli Gabriele
Published: February 2023

As cities continue to expand it has become crucial to describe their evolution in time and space. Building on analogies with biological systems, we propose a minimalist reaction-diffusion model coupled with economic constraints and an adaptive transport network, describing the co-evolution of population density with the transport system. Using a unique dataset, we reconstruct the evolution of London (UK) over 180 years and show that after an initial phase of diffusion limited growth, population has become less centralised and more suburban in response to economic needs and an expanding railway network. The coevolution of the rail system with a growing urban population has generated a transport network with hierarchical characteristics which have remained relatively constant over time. These results show that urbanisation patterns largely depend on the evolution of transport systems and population-transport feedbacks should be carefully considered when planning and retrofitting urban areas.
Kinetic effects and their role on the entry and transport of finite-size plasma jets inside the Hermean magnetosphere
Authors: Voitcu Gabriel , Echim Marius , Teodorescu Eliza , Munteanu Costel
Published: February 2023

The dynamics of finite-size plasma irregularities/jets streaming across magnetic discontinuity regions, as the magnetopause, is a key process for better understanding the transport of mass, momentum and energy from the solar wind towards planetary magnetospheres. In this paper we investigate the kinetic effects and their role on the entry and transport of localized solar wind/magnetosheath plasma structures inside the Hermean magnetosphere under northward orientation of the interplanetary magnetic field. For this purpose, we use three-dimensional particle-in-cell simulations adapted to the interaction between plasma elements/irregularities/jets of finite spatial extent and the typical magnetic field of Mercury’s magnetosphere. Our simulations reveal the penetration of solar wind plasma across the Hermean magnetopause and transport inside the magnetosphere. The entry process is controlled by the magnetic field increase at the magnetopause. For reduced jumps of the magnetic field (i.e. for larger values of the interplanetary magnetic field), the magnetospheric penetration is enhanced. The equatorial dynamics of the plasma element is characterized by a dawn-to-dusk asymmetry, the braking being stronger in the dawn flank. More plasma penetrates into the dusk flank and advances deeper inside the magnetosphere than in the dawn flank. The simulation results are discussed in the context of the impulsive penetration mechanism.
Soil Hydraulic Conductivity Controls Soil Moisture Limitation of Transpiration Globally
Authors: Wankmüller Fabian , Delval Louis , Cecere Andrea , Lehmann Peter , Javaux Mathieu , Carminati Andrea
Published: February 2023

At a critical soil water content (θcrit), terrestrial ecosystem fluxes at the soil-vegetation-atmosphere interface transition from energy into water limitation. Understanding and predicting soil, plant and atmospheric mechanisms that control θcrit are central to interpreting and predicting impacts of drought on ecosystems, including the associated feedbacks to carbon and hydrological cycle. Thanks to the existing monitoring networks, θcrit can now be estimated globally across soils, biomes and climates. However, the mechanisms and key parameters that explain θcrit as a result of soil-, plant-, and climate-interaction remain elusive. Here, we show that the soil hydraulic conductivity function determines mean and variability of θcrit. The underlying concept to calculate θcrit assumes that soil moisture limitation of transpiration is triggered by a loss in soil hydraulic conductivity around the roots. Taking soil-specific hydraulic properties into account, our soil-plant hydraulic model predicts the observed mean and variance of θcrit as a function of soil textural classes. In coarse textured soils, θcrit is small due to the lower absolute soil hydraulic conductivity and its steeper decline with soil drying compared to fine textured soils. The increasing variability of θcrit in fine-textured soils is explained by (i) the wide range of hydraulic conductivity values for similar soil textures as a result of soil structure formation and (ii) by the higher sensitivity to plant traits and climate for soils with less steep hydraulic conductivity curves (i.e., loamy soils). The corresponding critical soil matric potential (hcrit) is also soil texture specific, and it covers a broad range of values, from values close to field capacity in sandy soils (hcrit ca. -100 hPa) to values close to the wilting point in clay soils (hcrit ca. – 1 MPa). The model implies that climate change has a smaller effect on θcrit in sandy soils, suggesting that soil texture modulates climate effects on water use and photosynthesis globally. Overall, our results prove the prominent role of soil hydraulic conductivity for water limitation of ecosystem fluxes and for plants’ potential to adjust to water limitations subject to alterations due to climate change.
NH-SWE: A new Northern Hemisphere Snow Water Equivalent dataset based on in-situ snow depth time series (1950-2022)
Authors: Fontrodona-Bach Adrià , Schaefli Bettina , Woods Ross , Teuling Ryan , Larsen Josh
Published: February 2023

Ground-based observation datasets of Snow Water Equivalent (SWE) are scarce. In contrast, numerous long-term and good quality ground observations of snow depth are available. Furthermore, an increasing number of models can accurately convert snow depth to SWE. We present a novel dataset of SWE time series over the Northern Hemisphere based on in-situ observations of snow depth. We convert snow depth to SWE using the DeltaSNOW model and we present a method to generalise the conversion model for global use. We calibrate the model over a wide range of climates with the SNOTEL dataset and we regionalise the model parameters based on climate variables. We evaluate this approach on independent datasets such as the Canadian SWE dataset and other European SWE datasets. The key strengths of the modelling approach and the SWE dataset are the excellent performance of peak SWE and timing of snowmelt season onset. The final SWE dataset contains 11,003 stations with daily SWE and snow density time series distributed across the Northern Hemisphere, including mountain regions, at the point scale, and spanning the period 1950-2022. The dataset is available and free to access. It can be used for a variety of applications including validation of remote sensing of snow, hydrological modelling, water resources assessment and climate change impact analyses.
The automatic detection of tectonic plates in 3D mantle convection models and plate motion changes
Authors: Janin Alexandre , Coltice Nicolas , Tierny Julien , Chamot-Rooke Nicolas
Published: February 2023

The rigid surface of the Earth is divided into a jigsaw puzzle of about 50 tectonic plates separated by boundaries. Nowadays, three-dimensional spherical mantle modelling manages to produce self-consistently a stiff surface fragmented into several rigid caps that exhibit a plate-like behaviour. It thus becomes possible to analyse the dynamics of these models through the prism of plate tectonics theory and compare it to plate reconstruction models for the Earth. Such an analysis requires a robust method to automatically detect plates and their boundaries from continuous geophysical fields. The method should further recognize diffuse plate boundaries, as observed on Earth and reproduced in mantle convection models. We propose here a method to automatically detect and track plates through time, based on a trans-disciplinary approach combining a geodynamical and kinematic analysis with applied mathematics and computer sciences. This analysis is performed using the free and open-source software Paraview and the open-source software platform TTK (Topology ToolKit) designed for an efficient topological analysis of scalar fields. We apply our method to a three-dimensional spherical mantle convection model generating Earth-like plate tectonics at its surface. Our results show that, as for the Earth, the motion of modelled plates is stable over million-years-long periods separated by abrupt reorganizations occurring in less than 5 Myrs. The full plate-motion analysis over 262 Myrs in the model allows us to discuss the spatial extent of kinematic changes and shows that a plate reorganization can have regional to global effects on the plate network.
Early Holocene Laurentide Ice Sheet retreat influenced summer atmospheric circulation in the North American Arctic: Evidence from precipitation isotope and temperature proxy records and a climate model
Authors: Thomas Elizabeth , Cluett Allison , Erb Michael , McKay Nicholas , Briner Jason , Castañeda Isla , Corcoran Megan , Cowling Owen , Gorbey Devon , Lindberg Kurt , Salacup Jeffrey
Published: February 2023

Changes in ice sheet size and configuration impact global moisture and heat transport, but few proxy records examine these impacts. High-latitude precipitation-isotope proxy records are often interpreted to reflect temperature change, but can also reflect changes in moisture source. We present independent sub-centennial-scale records of summer temperature and summer precipitation δ2H from the same lake sediment archive on northeastern Baffin Island. We also examine published TraCE-21k transient model simulation results. These records span from 12 to 7 ka, when the Laurentide Ice Sheet underwent major retreat. The correlation structure between summer temperature and precipitation δ2H on northeastern Baffin Island changed from negative to positive around 10 ka. We interpret this change in correlation structure to indicate a shift in moisture sources to northeastern Baffin Island. TraCE-21k results suggest that moisture sources in this region are controlled by the relative strength of the high pressure systems and associated anticyclonic circulation over the Greenland and Laurentide ice sheets. We therefore interpret the proxy records as follows: when the Laurentide high dominated prior to 10 ka, northerly winds brought cold, dry Arctic air to the region, allowing 2H-enriched local sea breezes to provide most of the moisture to Baffin Island. After 10 ka, the Greenland high dominated, causing southerly flow to carry warm, moist, 2H-depleted air masses to northeastern Baffin Island. Regional centennial-scale cooling events caused by periodic freshwater inputs to the Labrador Sea throughout the Early Holocene were also associated with intervals of 2H-enriched summer precipitation. This study provides evidence that atmospheric circulation was influenced by the waning continental ice sheets. Similar ice-sheet influences are critical to consider when interpreting precipitation isotope proxy records spanning periods of dramatic ice-sheet change. These results demonstrate that precipitation isotopes can reflect changes in atmospheric circulation in the geologic record.
Testing the AROME Hybrid 3DEnVar for convective-scale NWP over Austria
Authors: Jyoti Kaushambi , Weissmann Martin , Griewank Philipp , Meier Florian
Published: February 2023

Ensemble and hybrid ensemble-variational Data Assimilation (DA) methods incorporating ensemble-based flow-dependent error statistics into state estimation have emerged in recent decades. In a hybrid DA, the background error covariances are a combination of ensemble covariances and static climatology. The ensemble component provides flow-dependency and non-linear error growth critical for convective-scale models, and the static climatology mitigates the effects of a small ensemble size. Hybrid ensemble variational DA methods were recently implemented in the convective-scale NWP model AROME at Meteo-France.We present our findings from testing Hybrid-3-Dimensional Variational Data Assimilation in convective-scale NWP model AROME over Austria. Given Austria's unique alpine orography, we investigate the impact of applying different weighting to flow-dependent covariances in hybrid DA for a summertime convection case over central Europe. In addition to the hybrid weights, we explore optimal ensemble size, the increase of ensemble size with a time-lagged approach as well as suitable localization settings. Finally, we compare our results to the 3-dimensional variational data assimilation (3DVar) operational model forecast of GeoSphere Austria and discuss the potential benefits, drawbacks, and challenges of using hybrid DA over traditional 3DVar.Keywords: summertime convection; hybrid-3DEnVar; AROME NWP model; flow dependent background error covariance
Building a Geospatial Lab – The People, The Tools, and The Process.
Authors: Kiran Amruth , Malladi Teja
Published: February 2023

What would it take to set up a center of geospatial excellence?Across academia and industry, there is a growing need to complement the exponential growth of Big Earth Observation (EO) data and the numerous possibilities for processing, rendering, visualization, and sharing geospatial data and its derivatives. The challenges that come with such opportunities include the identification of efficient tools, hiring and training of people at different skill levels, and the outreach activities that enable easier communication of scientific findings. These silos need to be broken into at each step of the process that helps sustain the growth of a lab in the long run.One such example is the Geospatial Lab (GSL) at the Indian Institute for Human Settlements (IIHS), Bangalore, India. Over the years, GSL has catered to many research, practice, and capacity-building initiatives of the institute that has helped bridge the gap and bring about a cultural change in the appreciation of the geospatial sciences. Developing a robust Research Data Infrastructure (RDI) using the foundational principles of open-source Spatial Data Infrastructure (SDI) at all levels of community engagement, has proven effective in reaching the right audience and decision-makers. Standard practices within the lab such as technical documentation, internal capacity building, extensive metadata, modern spatial/computing practices, spatial data management frameworks, and the interdisciplinarity of the team have seen greater adoption across the institution as well. These factors, coupled with excellent institutional support have been at the forefront of building a scalable, inter-operable, and distributed RDI that aims to prioritize the people over the pixel.