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Non-Stationary Discs and Instabilities
No full textInternational audienceWe review our current knowledge of thermal and viscous instabilities in accretion discs around compact objects. We begin with classical disc models based on analytic viscosity prescriptions, discussing physical uncertainties and exploring time-dependent solutions of disc evolution. We also review the ionization instability responsible for outbursting dwarf nova and X-ray binary systems, including some detailed comparisons between alpha-based models and the observed characteristics of these systems. We then review modern theoretical work based on ideas around angular momentum transport mediated by magnetic fields, focusing in particular on knowledge gained through local and global computer simulations of MHD processes in discs. We discuss how MHD may alter our understanding of outbursts in white dwarf and X-ray binary systems. Finally, we turn to the putative thermal/viscous instabilities that were predicted to exist in the inner, radiation pressure-dominated regions of black hole and neutron star discs, in apparent contradiction to the observed stability of the high/soft state in black hole X-ray binaries
Observation‐Based Estimate of Net Community Production in Antarctic Sea Ice
No full textInternational audienceAbstract Antarctic sea ice is one of the largest biomes on Earth providing a critical habitat for ice algae. Measurements of primary production in Antarctic sea ice remain scarce and an observation‐based estimate of primary production has not been revisited in over 30 years. We fill this knowledge gap by presenting a newly compiled circumpolar data set of particulate and dissolved organic carbon from 362 ice cores, sampled between 1989 and 2019, to estimate sea‐ice net community production using a carbon biomass accumulation approach. Our estimate of 26.8–32.9 Tg C yr −1 accounts for at least 15%–18% of the total primary production in the Antarctic sea‐ice zone, less than a previous observation‐based estimate (63–70 Tg C yr −1 ) and consistent with recent modeled estimates. The results underpin the ecological significance of sea‐ice algae as an early season resource for pelagic food webs
Dynamics of the subtidal transport through the Guafo Mouth connecting the open ocean and the Chilean Inland Sea in southern Chile
No full textInternational audienceThe Chilean Inland Sea (CIS) and the fjords region in Southern Chile host human activities such as salmon aquaculture. During the productive austral summer, the CIS exchanges heat, salt, dissolved oxygen, and nutrients with the Southern Pacific Ocean via the Guafo Mouth, a very shallow strait. Tides influence the productivity of the CIS, a high-frequency forcing typically not considered in circulation models when estimating exchange fluxes. In this work, the inflow, outflow, net, mass, and nutrient fluxes through the Guafo Mouth are evaluated using a high-resolution regional model forced by tides. Model output (temperature, salinity, and currents) is compared to hydrodynamic data. The impact of tidal forcing on summer-mean currents and transports is quantified. These findings are compared with results from a lower-resolution, commonly used, general circulation model. A Lagrangian modeling approach highlights that the water masses transiting from the open ocean through the Guafo Mouth mainly originate from the region south of the mouth
Estimation of electric vehicle lithium-ion battery scrap towards recycling facilities in the EU
No full textInternational audienceThe increasing demand for electric vehicles (EVs) in Europe, coupled with legislative efforts to reduce combustion engine vehicles, has significantly spurred the manufacturing of lithium-ion batteries (LIBs). However, this growth has led to a rapid rise in EV-LIB scrap, from both retired batteries and manufacturing processes, a factor insufficiently addressed in prior research. Our study tackles this issue by assessing the harmonisation of industry projects and examining the recycling facilities' readiness to handle these dual waste streams. We methodically estimate the registrations of new EVs and their anticipated scrap volume, and then project future LIB manufacturing scrap in the EU. Therefore, we assess current and future recycling capacities and evaluate the balance between scrap influx and recycling readiness by 2030. Our findings indicate that the EU is facing a significant recycling challenge. By 2030, about 930 kilotonnes of scrap from the EV-LIB industry will need recycling under the baseline scenario. Although current capacities can handle today's scrap volumes, the disparity between rapidly expanding manufacturing and lagging recycling facilities will result in a shortfall in a few years. Current plans suggest EU recycling facilities will have a capacity of about 785 kilotonnes annually by 2030, which falls short of the dual scrap streams. This research underscores the need for a strategic approach to scale up recycling infrastructure and technology, to emphasise the importance of responsible manufacturing, and to align with the EU's sustainability goals and the growing demands of the EV industry
The Interplay of Clay Behavior and Particle Structuring: A Multiscale Investigation
No full textInternational audienceThe effects of different particle associations on the mechanical behavior of kaolinite are investigated by coupling the experimental mechanical results with microscopic analyses. Two types of particle structures are generated through sedimentation tests conducted in solutions with different pH values, in which flocculation and dispersion of particles take place. It is shown that the compressibility of flocculated samples with an edge-to-face particle structure is higher than that of dispersed samples with a face-to-face particle structure. The particle associations are strongly influenced by the pH of the surrounding fluid. Mercury Intrusion Porosimetry (MIP) results showed that the dominant pore size of flocculated samples is higher than that of dispersed samples. Scanning Electron Microscope (SEM) observations on the vertical plane of clay samples provided a visualization of the particle arrangement after mechanical load
The role of mantle inheritance and refertilization during breakup at magma-poor rifted margins: What can we learn from the SW-Australia margin?
No full textInternational audienceThe study of mantle-melt interactions at magma-poor rifted margins, accounting for about half of the world margins, is so far limited by the access to samples. Present concepts are therefore mainly based on studies of the Western Tethys and southern North Atlantic domain, and it remains unclear if they are applicable to other magma-poor rifted margins. Here, we present a study of well-preserved peridotites dredged along the southwestern Australian margin (Diamantina Zone). Our petrological data show that two types of peridotites occur: spinel lherzolite, which represents the inherited subcontinental mantle (SCLM) before the separation of Australia and Antarctica, and plagioclase peridotite formed by syn-rift melt entrapment at low pressure in the plagioclase stability field during mantle exhumation. The observed mantle types as well as the mantle-melt processes identified in the Diamantina peridotites are very similar to those documented in the Alpine-Apennine and Iberia margins. Hence, the Alpine/Iberia model of magma-poor rifted margins may be globally applicable and does not depend on the SCLM inheritance. Remnants of mantle inheritance may be preserved in the refertilized mantle, suggesting a progressive transition from an inherited to a refertilized mantle during breakup. Finally, this study highlights the role of inheritance and refertilization as the main features controlling final rifting and breakup at magma-poor rifted margins
Time-lagged recurrence: A data-driven method to estimate the predictability of dynamical systems
No full textInternational audienceNonlinear dynamical systems are ubiquitous in nature and they are hard to forecast. Not only they may be sensitive to small perturbations in their initial conditions, but they are often composed of processes acting at multiple scales. Classical approaches based on the Lyapunov spectrum rely on the knowledge of the dynamic forward operator, or of a data-derived approximation of it. This operator is typically unknown, or the data are too noisy to derive its faithful representation. Here, we propose a data-driven approach to analyze the local predictability of dynamical systems. This method, based on the concept of recurrence, is closely linked to the well-established framework of local dynamical indices. When applied to both idealized systems and real-world datasets arising from large-scale atmospheric fields, our approach proves its effectiveness in estimating local predictability. Additionally, we discuss its relationship with other local dynamical indices, and how it reveals the scale-dependent nature of predictability. Furthermore, we explore its link to information theory, its extension that includes a weighting strategy, and its real-time application. We believe these aspects collectively demonstrate its potential as a powerful diagnostic tool for complex systems
Cities and Urban areas with Mobility based on Innovation and carbon Neutrality: CUMIN programme extension
No full textInternational audienceTo limit the global warming, the greenhouse gases (GHG) have to be reduced. In Europe the transport is one of the main contributor to GHG. Since 2010, University of Lille does regularly a carbon footprint report. The commuting represents more than 50% of its GHG. In 2016, the CUMIN (Campus of University with Mobility based on Innovation and carbon Neutrality) interdisciplinary programme of University of Lille has been developed to propose electromobility solutions to contribute to a significant reduction of the commuting GHG. This research program is now extended to "Cities and urban areas". CUMIN develops a crossdisciplinary approach combining technological, economic and social aspects. It brings together 3 research groups on sciences & technologies, 3 research groups on human & social sciences and the MEL (Métrople Européenne de Lille). The CUMIN programme is presented and first results are discussed
Statistical behavior of temporally compounding multi-peak flood events
No full textInternational audienceFloods are the most frequent natural hazard globally (2003-2023) and rank second in economic losses, according to EM-DAT, the International Disaster Database. When flood events occur in close succession, they pose significant challenges for emergency management due to limited recovery time between events. This study focuses on multi-peak (MP) floods, where peaks occur within hours to days. Using discharge data from 77 hydrometric stations in Northern Italy's Po district, we examined statistical differences between MP and single-peak (SP) flood events and analyzed their seasonal patterns and generating mechanisms across diverse river regimes. We demonstrated that SP and MP events exhibit distinct statistical behaviors. The first type of events has more skewed distributions with heavy tails, while the second displays flatter distributions with lighter tails and higher mean values. Seasonal analyses suggest that MP floods in glacial and nival-pluvial regimes are influenced by glacier and snow melting, whereas those in the Padanian regime are driven by tributary routing effects. These triggering mechanisms seem to be responsible of the lighter tails of the distribution of MP floods. By highlighting the distinct statistical behaviors and generating mechanisms of MP and SP floods, we identified recommendations for designing MP flood hydrograph, supporting flood-risk management.</div
Filtering out large-scale noise for cluster weak-lensing mass estimation
No full textInternational audienceWe present a new method for estimating galaxy cluster masses using weak-lensing magnification. The effect of weak-lensing magnification introduces a correlation between the position of foreground galaxy clusters and the density of background sources. Therefore, cluster masses can be inferred through observations of these correlations. In this work, we introduce a method that allows us to considerably reduce noise correlations between different radial bins of the cluster magnification signal via a Wiener filtering of our observed magnification field on large scales. This method can reduce the uncertainty on the estimated galaxy cluster mass and it can also be applied to cluster mass estimation for weak-lensing shear. The method was applied to Hyper-Suprime Cam galaxies and CAMIRA clusters detected within the Hyper-Suprime Cam survey (HSC). With HSC data, we find that our filtering method significantly reduces the correlation of noise between radial magnification bins. The estimated cluster mass is consistent between the filtered and unfiltered methods, with similar errors between the two methods as our current measurement errors contain significant contributions from the irreducible shot-noise. For deeper surveys, the effects of shot noise will be less important and this method will lead to greater improvements on the estimated cluster mass