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Emerging evidence of abrupt changes in the Antarctic environment
No full textInternational audienceHuman-caused climate change worsens with every increment of additional warming, although some impacts can develop abruptly. The potential for abrupt changes is far less understood in the Antarctic compared with the Arctic, but evidence is emerging for rapid, interacting and sometimes self-perpetuating changes in the Antarctic environment. A regime shift has reduced Antarctic sea-ice extent far below its natural variability of past centuries, and in some respects is more abrupt, non-linear and potentially irreversible than Arctic sea-ice loss. A marked slowdown in Antarctic Overturning Circulation is expected to intensify this century and may be faster than the anticipated Atlantic Meridional Overturning Circulation slowdown. The tipping point for unstoppable ice loss from the West Antarctic Ice Sheet could be exceeded even under best-case CO2 emission reduction pathways, potentially initiating global tipping cascades. Regime shifts are occurring in Antarctic and Southern Ocean biological systems through habitat transformation or exceedance of physiological thresholds, and compounding breeding failures are increasing extinction risk. Amplifying feedbacks are common between these abrupt changes in the Antarctic environment, and stabilizing Earth’s climate with minimal overshoot of 1.5 °C will be imperative alongside global adaptation measures to minimise and prepare for the far-reaching impacts of Antarctic and Southern Ocean abrupt changes
Parameter Estimation in Land Surface Models: Challenges and Opportunities With Data Assimilation and Machine Learning
No full textInternational audienceAccurately predicting terrestrial ecosystem responses to climate change over long‐timescales is crucial for addressing global challenges. This relies on mechanistic modeling of ecosystem processes through land surface models (LSMs). Despite their importance, LSMs face significant uncertainties due to poorly constrained parameters, especially in carbon cycle predictions. This paper reviews the progress made in using data assimilation (DA) for LSM parameter optimization, focusing on carbon‐water‐vegetation interactions, as well as discussing the technical challenges faced by the community. These challenges include identifying sensitive model parameters and their prior distributions, characterizing errors due to observation biases and model‐data inconsistencies, developing observation operators to interface between the model and the observations, tackling spatial and temporal heterogeneity as well as dealing with large and multiple data sets, and including the spin‐up and historical period in the assimilation window. We outline how machine learning (ML) can help address these issues, proposing different avenues for future work that integrate ML and DA to reduce uncertainties in LSMs. We conclude by highlighting future priorities, including the need for international collaborations, to fully leverage the wealth of available Earth observation data sets, harness ML advances, and enhance the predictive capabilities of LSMs
A closer look into copepod’s morphology: in situ imaging reveals links with environment and marine heat waves
No full textInternational audienceWithin marine mesozooplankton communities, copepods are a key group both in terms of abundance and biomass, hence contributing to central ecological functions of aquatic ecosystems. Analyzing their morphological traits can provide valuable insight into ecosystem processes and relation with the environment that might otherwise go unnoticed. Imaging techniques are an increasingly used tool to sample the traits of mesozooplankton, and especially of copepods. In this study, we use in situ imaging from the Underwater Vision Profiler (UVP) to explore the relationship between copepod’s morphology and environmental conditions in the upwelling of the California Current Ecosystem (CCE). Over 4 years, from 2008 to 2016, morphological traits such as size, complexity, and transparency were measured from copepod’s images captured by the UVP deployed as part of the CCE-Long-Term Ecosystem Research. Our findings reveal that copepod’s size is linked with environmental seasonal variations, with larger copepods in fall, smaller in summer/spring and even smaller during a summer marine heatwave. Change of transparency also occurs during seasons, especially between spring and fall showing a significant relationship between copepod transparency and seasonal productivity. Interestingly, our results indicate more transparent copepods in the CCE are associated with higher carbon flux. By uncovering these morphological-environmental patterns, our study contributes to a better understanding of copepods’ roles in aquatic ecosystem functioning and consequences of environmental change on this group
Avis du conseil scientifique du comité de bassin Seine-Normandie sur la sobriété en eau
No full textThere is often a confusion between sufficiency, efficiency, recycling, and substitution. One response to water shortages during droughts is often to mobilize other water resources, ranging from interconnecting drinking water networks to reusing unconventional water, including storage and inter-basin transfers. These responses do not lead to a reduction in dependencies. Water savings are mainly achieved through technical means (increased efficiency). This is a minimal adaptation of production and consumption patterns (Barles, 2024), which can have negative externalities, exacerbated by trends related to climate change and resource depletion. sufficiency differs from reduction/economy in principle: it involves organizing collectively and culturally to adapt production and water consumption patterns to meet needs within the limits of planetary resources. sufficiency increases resilience to inevitable shocks, reduces costs and enhances competitiveness (by avoiding waste and unnecessary investment in infrastructure), and facilitates the achievement of objectives in terms of reducing greenhouse gas emissions and pollution, and safeguarding biodiversity. Achieving sufficiency requires: o training and information; o involvement from all sectors, particularly energy production, raw material extraction, and agricultural production; o participatory governance and long-term planning: the unfair nature of certain sharing decisions leads to unsustainable practices; o local consultation on the allocation of extractable volumes involving all relevant stakeholders.La confusion est très fréquente entre sobriété, efficacité, recyclage et substitution. Une réponse aux pénuries d’eau lors des sécheresses est souvent la mobilisation d’autres ressources en eau, ce qui va de l’interconnexion des réseaux d’eau potable, à la réutilisation d’eaux non conventionnelles, en passant par le stockage, jusqu’aux transferts interbassins. Ces réponses ne conduisent pas à une réduction des dépendances. Les économies d’eau sont principalement obtenues par des moyens techniques (augmentation de l’efficacité). Il s’agit là d’une adaptation a minima des modes de production et de consommation (Barles, 2024), qui peuvent avoir des externalités négatives, aggravées par des tendances liées au changement climatique et à l’épuisement des ressources. La sobriété se distingue de la réduction/l’économie, dans son principe : il s’agit de s’organiser collectivement et culturellement pour adapter les modes de production et la consommation en eau à la satisfaction des besoins dans les limites des ressources planétaires. La sobriété permet d’augmenter la résilience aux chocs inévitables, de réduire les coûts et renforcer la compétitivité (en évitant le gaspillage et les investissements inutiles dans des infrastructures), de faciliter l’atteinte des objectifs en termes de réduction des émissions de gaz à effet de serre, des pollutions, et de sauvegarde de la biodiversité. Atteindre la sobriété nécessite : o de la formation et de l’information ;o une implication de tous les secteurs, en particulier la production d'énergie ; l’extraction de matières premières et la production agricole ; o des gouvernances participatives et une planification à long terme : le caractère inéquitable de certaines décisions de partage conduit à des pratiques non sobres ;o une concertation locale sur l’allocation des volumes prélevables impliquant l’ensemble des acteurs concernés
Parchment preservation state of the Prayer book of Mary of Guelders
No full textInternational audienceIlluminated medieval manuscripts are of outstanding value and their preservation is of great importance, not only because of their beauty but also because of the information they contain about medieval society. This work focuses on the evaluation of the parchment state of preservation of the Prayer book of Mary of Guelders, which comprises about 600 folios. The knowledge gained should support the decision-making process regarding suitable conservation measures. An assessment of the preservation state of the parchment was performed from the macro- down to the microscale. Optical observations of cracks in the parchment and colour measurements preceded chemical analyses. The hydrothermal stability of the fibres was evaluated by means of observations using a micro hot table (MHT). The chemical state of preservation of parchment was evaluated using Laboratory-based Fourier transform (FT) Infrared (IR) analysis in reflection mode as well as synchrotron FTIR imaging in transmission mode at the IRIS beamline at BESSY II/ HZB in Berlin. The study allowed the conclusion that the parchment of the Prayer book of Mary of Guelders was in good state of preservation and indicated that the parchment changes were mainly caused by mechanical stress on the folios due to tight binding of the book and not by chemical processes
Isomer specific photochemistry in Titan’s atmosphere
No full textInternational audienceTitan’s atmosphere is an active organic laboratory instigated by the photolysis of its main components, N2 and CH4, and terminating with the formation of photochemical hazes (Hörst et al. 2017, Coustenis et al. 2021). Its complex chemical inventory has been characterized through observations with multiple space-born and ground-based observatories and with dedicated space missions such as Cassini-Huygens (NASA-ESA-ASI) that explored the Saturnian system from 2004 to 2017 providing an unprecedented view of Titan’s complexity. The characterization of the neutral inventory has revealed a plethora of hydrocarbons with up to 6 carbons atoms as well as multiple nitrile species (Nixon 2024). The corresponding ion characterization has revealed multiple ions up to mass of 100 Da as well as larger macromolecules up to 10 000 Da/q that are considered the embryos of haze formation (Waite et al. 2007). To interpret this complexity, photochemical models include hundreds of chemical species involved in chemical networks of ion-neutral processes containing thousands of reactions (Vuitton et al. 2019, Loison et al. 2019, Willacy et al. 2022). However, despite this profound complexity these networks contain limited information on the different isomers that could be formed for a given stoichiometric structure. For small hydrocarbons up to two carbon atoms isomerization is not a major issue but the possible number of structural forms rapidly increases from three carbon atoms and above. While observations have identified the main isomers for small mass hydrocarbons, an understanding for the abundance of minor isomers is useful for exploring their possible detection in Titan’s atmosphere. Moreover, isomers not typically considered in photochemical models can partake in chemical processes that lead to rapid chemical growth and foster different pathways of chemical evolution (Thomas et al. 2019). This is particularly important given recent advance in spectroscopic observations sensitivity that allow observational constraints on the less abundant isomers, unlocking the potential for powerful constraints on the chemical schemes. In this work we explore the photochemistry of isomers in Titan’s atmosphere. We first investigate isomers of C3Hx stoichiometry (Fig. 1) as for those there are observational constraints. We then progressively expand the investigation to larger molecules. Our simulations demonstrate two main mechanisms controlling the formation of the different isomers from neutral processes. Forward mechanisms lead to the growth of isomers by the chemical reaction of smaller molecules/radicals and is drastically limited by the low temperature conditions in Titan’s atmosphere. Backward mechanisms due to the photodissociation of larger molecules that allows for the formation of isomers that are not accessible through molecular collisions alone. A third mechanism involves reactions with ions or ion recombination for the formation of different isomers. Information for these mechanisms is not always available. Particularly, details for the photodissociation channels and yields for different isomers from either experimental or theoretical studies becomes sparser with increasing molecular mass. We will present the dominant mechanisms for different isomers and discuss the current assumptions/limitations in the estimation of their abundances. Figure 1. Simulated mole fractions of different isomers of hydrocarbons with 3 carbon atoms in Titan’s atmosphere. ReferencesCoustenis 2021. The atmosphere of Titan. Oxford Research Encyclopedias. Hörst et al. 2017. Titan’s atmosphere and climate, JGR:Planets, 122, 432 Loison et al. 2019. The photochemical production of aromatics in Titan’s atmosphere. Icarus, 329, 55-71. Nixon 2024. The composition and chemistry of Titan’s atmosphere. ACS Earth Space Chem., 8, 406 Thomas et al. 2019. Combined Experimental and Computational Study on the Reaction Dynamics of the 1‐Propynyl (CH3CC)−1,3-Butadiene (CH2CHCHCH2) System and the Formation of Toluene under Single Collision Conditions. J. Phys. Chem. A, 123, 4104 Vuitton et al. 2019. Simulating the density of organic species in the atmosphere of Titan with a coupled ion-neutral photochemical model. Icarus,324,120 Waite et al. 2007. The Process of Tholin Formation in Titan’s Upper Atmosphere. Science,316,870 Willacy et al. 2022. Vertical distribution of cyclopropenylidene and propadiene in the atmosphere of Titan. Ap.J. 933:23
Factors associated with teacher attrition: longitudinal findings from the CONSTANCES cohort
No full textInternational audienceAbstract Background While teacher attrition is a growing concern worldwide, data on its risk factors are limited by cross-sectional designs, focusing on intent rather than actual departure, failing to distinguish between leaving the sector and changing job within in, and overlooking the interplay of work, personal, social, and health factors. We aimed to fill the gap in studying, among teachers, factors prospectively associated with respectively: 1/changing jobs while remaining in education (switching) and 2/leaving teaching to work in another sector (leaving). Methods Longitudinal analysis of 15,185 teachers enrolled from 2012 in the French population-based CONSTANCES cohort. Using Cox proportional hazards models, we estimated the risk up to 2022 of switching/leaving in association with various socio-demographic, health, socio-economic, and psychosocial risk factors. Results During follow-up, 275 teachers switched and 286 left. Males were more likely than women to both switch and leave. Factors associated with switching included age≥35, teaching in primary school, low depressive symptoms, full-time work, frequent (not constant) strained relationships at work, past financial difficulties, and organizational constraints. Factors associated with leaving included age<35, living alone without children, presence of depressive symptoms, part-time work, constant strained relationships at work, and current financial difficulties. Effort-reward imbalance, perceived health, and commute time were not significantly associated with either outcome in multivariate analyses. Conclusions Switching and leaving are prospectively related to quite different sets of risk factors, supporting distinct subjacent contexts and motivations, namely: switching as career progression, leaving due to adverse conditions. Preventing strained relationships at school, addressing teachers’ economic realities, and providing mental health support represent promising avenues to limit job attrition among teachers. Key messages • Two different processes, switching and leaving, contributes to teacher attrition. • To limit it, promising avenues include mental health support, school violence prevention and financial enhancement
MP-20.04—Predictive Model Combining Clinical and MRI Data for Detecting Clinically Significant Prostate Cancer Using Elastic Fusion Registration
No full textInternational audienceIntroduction and Objectives: Prostate cancer (PCa) is the most commonly diagnosed malignancy in men and a leading cause of cancer-related death worldwide. Given the rising global incidence (1.4 million cases in 2020 and an estimated 2.9 million by 2040), it is crucial to improve risk assessment tools to reduce unnecessary biopsies. Tools based solely on clinical data, such as the Prostate Cancer Prevention Trial (PCPT) risk calculator, offer mediocre accuracy (AUC: 0.56–0.72), while early attempts to incorporate MRI suffered from limited datasets and imprecise targeting methods. Objective: To use clinical and MRI data from a large cohort of biopsies obtained by elastic fusion registration (EFR) to develop a model predicting clinically significant prostate cancer (csPCa), defined as ISUP grade ≥ 2.Materials and Methods: A cohort of 1,550 patients who underwent biopsy without a prior diagnosis (January 2018–March 2023) was analyzed. Variables included: age, PSA level (ng/mL), family history of prostate cancer (yes/no), history of negative biopsy, prostate volume, and the maximum PI-RADS score. Data were split into a training set (80%) and a test set (20%). The primary outcome was the presence of cancer on biopsy.Results: The model demonstrated excellent discriminative performance: AUC: 0.81, sensitivity: 61.4%, specificity: 87.1%, accuracy: 73.6%, PPV: 84.0%, and NPV: 67.0%. In the validation cohort of 310 patients, it would have avoided 100 unnecessary biopsies (32.3%) while still detecting 128 (87.1%) of the 147 cancers identified through EFR.Conclusions: The model showed strong discriminatory power in predicting csPCa risk. Combining clinical variables and MRI data (PI-RADS score, prostate volume) facilitated risk stratification. We propose this validated tool as a means to reduce unnecessary procedures through accurate risk stratification
Winter sea ice edge shaped by Antarctic Circumpolar Current pathways
No full textInternational audienceThe Antarctic Circumpolar Current (ACC) is often considered a natural barrier for the northward expansion of the Antarctic sea ice, but the underlying processes remain little explored. Here, we focus on the main fronts of the ACC – as a measure of the current system's path – to study how they influence the mean state of sea ice. We find that the latitude of all ACC fronts as a function of longitude shows a correlation above 0.85 with the climatological mean latitude of the winter sea ice edge, indicating a strong link across all sectors of the Southern Ocean. Among the ACC fronts, the Polar Front is identified as the best indicator for studying the ACC's influence on sea ice, as it marks a distinct transition in upper-ocean water mass properties and is consistently found north of the sea ice edge. The distance between the Polar Front and the sea ice edge decreases when the Polar Front lies farther south, due to the presence of warmer waters at higher latitudes. These warmer waters enable efficient heat transport toward the ice edge and constitute a barrier to sea ice expansion, via two main mechanisms. First, the ocean carries heat from the Polar Front toward the pole, in particular through the contribution of mesoscale ocean eddies formed downstream of major underwater topographic features. Second, warmer oceanic surface waters near the front heat the atmosphere above, which then carries this heat poleward towards the ice, especially in regions with more southward-directed winds. Since the Polar Front's path is largely shaped by topographic barriers, these results indicate why the position of the winter sea ice edge is strongly constrained, under current conditions, by bathymetry
ESA Sea Surface Salinity Climate Change Initiative (Sea_Surface_Salinity_cci): Weekly and monthly sea surface salinity products from L-band, v5.5
No full textWeekly and monthly sea surface salinity fields derived from satellite observations (L-Band radiometry) - version 5.5The European Space Agency (ESA) Sea Surface Salinity Climate Change Initiative (CCI) consortium has produced global, level 4, multi-sensor Sea Surface Salinity maps covering the 2010-2023 period. This dataset collection contains Sea Surface Salinity (SSS) v5.5 data at a spatial resolution of 50km and a time resolution of 1 week. It has been spatially sampled on a regular 0.25° grid and 1 day of time sampling. This product is also available on polar 25 km EASE-2 (Equal Area Scalable Earth) grid. A monthly product is also available, at a spatial resolution of 50 km and a time resolution of 1 month. It is spatially sampled on a 0.25° grid and 15 days of time sampling. This product is also available on polar 25km EASE-2 grid. In addition to salinity, information on uncertainties are provided. For more information, see the user guide and product documentation available on the Sea Surface Salinity CCI web pag