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Cassini CAPS‐ELS Observations of Low‐Energy Electron Beams Within Enceladus Mid‐Latitude Flux Tubes
No full textInternational audienceAbstract The electrodynamic interaction between Saturn's magnetosphere and Enceladus accelerates electrons along magnetic field lines. These electrons propagate inside magnetic flux tubes connecting the moon to the giant planet, generating distinctive auroral hiss and auroral footprint signatures, both previously observed by the Cassini spacecraft. In this study, we analyze low‐energy electron measurements made during multiple mid‐latitude crossings of magnetic flux tubes connected to Enceladus' wake. We show that the properties of the observed electrons are consistent with those of electrons inducing Enceladus' auroral hiss, and discuss the physical processes responsible for their pitch‐angle distributions and acceleration. Field‐aligned electron beams have very different properties from those triggering the Enceladus ultraviolet footprint, with a much lower characteristic energy and energy flux. Observations of electron beams resulting from the moon‐magnetosphere interactions up to 30° downstream of the moon reveal that the coupling system between Enceladus and Saturn is significantly more extended than previously anticipated
Using line-by-line Monte Carlo to compute the Earth’s outgoing longwave radiation and CO2’s radiative forcing
No full textInternational audienceThe Earth’s radiation budget is a crucial part of climate and its evolution. Being part of this budget, the outgoing longwave radiation (OLR) has been extensively studied, especially in the context of climate-change and anthropogenic greenhouse gases emissions modifying the Earth’s radiative equilibrium.In this study we present a new line-by-line radiative code RadForcE, we have developed to compute the global OLR and radiative forcing over a 10-year period. Based on a backward longwave Monte Carlo method, RadForcE uses line-by-line spectroscopic data for several molecular gases (CO2, H2O, CH4 and O3) from high-resolution databases GEISA and HITRAN, as well as different continua. The clouds’ vertical distributions are taken into account with a vertical overlap subgrid parameterization that is sampled "on the fly" for each optical path along vertical atmospheric profiles. Those profiles are sampled over a 10-year period all over the globe, either from GCM outputs or from ERA5 reanalysis, to compute the unbiased global OLR at a very small computational cost (~10 minutes on a laptop).We this new method we are also able to directly compute any greenhouse gas radiative forcing, and present estimates of the radiative forcing for a doubling of CO2. The Monte Carlo approach allows us to identify, for each outgoing optical path at the top of the atmosphere, the emitting species as well as the altitude of emission. By doing so, we can visualize the profile of altitude of emission for each species, as well as how some gases can screen other species’ emission or the surface’s emission. We can also visualize, for a doubling of CO2, the increase of stratospheric emission by CO2, and its screening of the surface’s emission and water vapor tropospheric emission
Harmonised boundary layer wind profile dataset from six ground-based Doppler wind lidars in a transect across Paris, France
No full textInternational audienceDoppler wind lidars (DWL) offer high-resolution wind profile measurements that are valuable for understanding atmospheric boundary layer (ABL) dynamics. Here six ground-based DWL, deployed in a multi-institutional effort along a 40 km transect through the centre of Paris (France), are used to retrieve horizontal wind speed and direction through the ABL at 18–25 m vertical and 1–60 min temporal resolution. Data are available for June 2022–March 2024 (three DWL) and two Intensive Observation Periods (six DWL) across 9 weeks in September 2023–December 2023. Data from all sensors are harmonised in terms of quality control, file format, as well as temporal and vertical resolutions. The quality of this DWL dataset is evaluated against in-situ measurements at the Eiffel Tower and radiosonde profiles. This unique, spatially dense, open dataset will allow urban boundary layer dynamics to be explored in process-studies, and is further valuable for the evaluation of high-resolution weather, climate, inverse and air pollution models that resolve city-scale processes. The dataset is available at https://doi.org/10.5281/zenodo.14761503 (Morrison et al., 2025)
Controls of the global overturning circulation of the ocean
No full textInternational audienceAbstract The global overturning circulation (GOC) is the largest scale component of the ocean circulation, associated with a global redistribution of key tracers such as heat and carbon. The GOC generates decadal to millennial climate variability, and will determine much of the long-term response to anthropogenic climate perturbations. This review aims at providing an overview of the main controls of the GOC. By controls, we mean processes affecting the overturning structure and variability. We distinguish three main controls: mechanical mixing, convection, and wind pumping. Geography provides an additional control on geological timescales. An important emphasis of this review is to present how the different controls interact with each other to produce an overturning flow, making this review relevant to the study of past, present and future climates as well as to exoplanets’ oceans
At‐sea intercomparison of a membrane‐based p CO<sub>2</sub> sensor and a traditional showerhead equilibrator system on a Ship‐of‐Opportunity
No full textInternational audienceAbstract The seawater partial pressure of carbon dioxide ( p CO 2 ) is an essential ocean variable needed to calculate air‐sea gas exchange and to identify marine carbon sinks and sources. Recent technological developments support autonomous p CO 2 measurements with sensors that are smaller and cheaper. In July 2021, these differences were highlighted during the Integrated Carbon Observation System—Ocean Thematic Centre laboratory intercomparison exercise. A key message from the intercomparison was the need for further field comparisons. Here we present the results from a field test of two generations of ‐4H‐Jena HydroC CO2‐FT membrane‐based sensors alongside a General Oceanics equilibrator system. The intercomparisons were done onboard a ship‐of‐opportunity regularly traveling between Europe and South America. The first phase of the experiment took place in 2021, when the difference between the two instruments was within ± 10 μ atm during 53% of the intercomparison time. For the second phase, improvements were made, including the addition of an automated cleaning routine for the membrane‐based sensor, the installation of a new sensor prototype with the ability to measure a reference gas, and an updated data processing method. These changes improved the performance and, during the last 2023 journey, the mean difference decreased to 2.0 ± 5.0 μ atm, and was within ± 10 μ atm during 97% of the deployment time. This experiment revealed that with a suitable deployment approach considering biofouling and reference gas measurements, membrane‐based sensors can measure seawater p CO 2 within the Global Ocean Acidification Observing Network weather goal of 2.5% relative uncertainty on autonomous installations
Seasonal and interannual variability of the oxygen minimum zone in the Gulf of California entrance: Insights from high-resolution coupled physical-biogeochemical modelling
No full textInternational audienceThe oxygen minimum zone (OMZ) in the Gulf of California entrance (GCE) is a crucial feature of the northeastern tropical Pacific, significantly influencing regional biogeochemical cycles and marine ecosystems. This study investigates the seasonal and interannual variability of the OMZ upper boundaries using a high-resolution physical-biogeochemical coupled model. The model results are evaluated against satellite observations, Argo profiles, and in situ data, demonstrating its capability to capture key dynamical processes, including mesoscale eddies, poleward undercurrents, and coastal-trapped waves (CTWs). The high-resolution CROCO-PISCES model reveals two alternating periods of shoaling and deepening of the OMZ upper boundary in the Gulf of California Entrance, modulated by seasonal mesoscale dynamics and coastal-trapped wave (CTW) propagation. This study provides novel insights into the interannual influence of El Niño Southern Oscillation (ENSO) events on OMZ dynamics, with El Niño driving significant deepening and contraction of the OMZ, and La Niña promoting shoaling and expansion. These variations are linked to changes in mesoscale dynamics, particularly the modulation of anticyclonic circulation at the Gulf’s entrance by equatorially forced CTWs associated with ENSO. The study highlights the complex interplay between local and remote oceanographic processes in determining the OMZ variability in the GCE. This research provides insights into the mechanisms driving OMZ dynamics in the Gulf of California and underscores the need for integrated observational and modeling approaches to predict the response of OMZs to ongoing climate variability
Adjusting for abiraterone-prednisone cross-over in de novo metastatic castration-sensitive prostate cancer: a post-hoc analysis of the PEACE-1 trial
No full textInternational audienceIntroduction: PEACE-1 is a 2x2 factorial phase III trial evaluating the impact of abiraterone-prednisone and prostate radiotherapy in patients with de novo metastatic castration-sensitive prostate cancer (mCSPC). Abiraterone-prednisone significantly improved overall survival (OS) (hazard ratio (HR)=0.82 [95%CI, 0.69-0.98]). In the control arm, men often received an androgen receptor pathway inhibitor (ARPI) -either abiraterone-prednisone or enzalutamide -after progression to castration-resistant disease. The use of active drug beyond progression may improve post-progression survival and thereby attenuate the estimated benefit of early use of this drug in intention-to-treat analyses. Methods: This post-hoc analysis applied three statistical methods to estimate an adjusted HR accounting for abiraterone-prednisone use beyond progression: Two-Stage Estimation (TSE), Inverse Probability of Censoring Weighting (IPCW) and Rank-Preserving Structural Failure Time Models (RPSFTM). Results: Among 589 patients randomised to the control arm, 183 received abiraterone-prednisone after disease progression. Compared with patients who did not, these men had higher PSA at diagnosis, higher tumour burden, more bone metastases, and were more likely to have received docetaxel for mCSPC. Experiencing biochemical progression was found to be a risk factor for 2nd line abiraterone use. The HR for OS adjusted by RPSFTM, IPCW, and TSE were 0.79 [0.64-0.98], 0.75 [0.62-0.92], and 0.82 [0.67-0.98], respectively. Sensitivity analyses adjusting for ARPI cross-over (abiraterone-prednisone or enzalutamide) yielded consistent results. Conclusions: This analysis confirms the survival benefit related to upfront abiraterone-prednisone use for patients with de novo mCSPC
High‐Performance Capacitive Sensor Based on Polyphosphazene‐Modified InP Electrodes for Hydroquinone Detection
No full textInternational audienceAbstract A high‐performance capacitive sensor is presented for the determination of hydroquinone (HQ) based on n‐type indium phosphide (n‐InP) electrodes with an electrochemically deposited polyphosphazene (PPP) coating. The integration of PPP with InP electrodes offers a previously unexplored approach to chemical sensing. The polymer film is deposited evenly and well examined by X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy‐dispersive spectroscopy (EDS), which confirms the formation of a chemically stable and passivating interface. Capacitance–voltage (C–V) measurements in phosphate‐buffered saline (PBS) reveal a linear detection range of 1–100 µ m and a limit of detection (LOD) of 0.73 µ m ( n = 3), highlighting the sensitivity of the sensor. Selectivity tests indicate minimal interferences from structurally related phenolic substances such as catechol and phenol, corroborating the very high selectivity toward HQ. This capacitive sensing platform offers a promising approach for the rapid, sensitive, and selective detection of these hazardous chemicals, with vast potential for use in environmental monitoring and analytical fields
High-resolution monitoring of the pH under strong La Niña conditions in Gorgona Island, Colombian Pacific, Panama Bight
No full textInternational audienceFew studies have investigated the potential drivers of high-resolution (daily and 24-hour scales) on ocean acidification (OA) and the carbonate system in a coastal estuary during an intense La Niña event. Therefore, we conducted the first high-resolution total scale pH (pH T ) monitoring every three hours for 56 days (13 September to 7 November 2021) at the Colombian Pacific in El Muelle reef, Gorgona National Natural Park. Two moored autonomous submersible instruments (iSAMI-pH and CTD-Diver) were deployed at a depth of 2 m in an area influenced by extreme precipitation, river discharge, semi-diurnal tides, and southwest winds during La Niña 2020-2023. Total alkalinity was derived from salinity data and used alongside pH T to calculate sea surface seawater partial pressure of CO 2 (pCO 2w ; μatm), dissolved inorganic carbon (DIC; μmol kg -1 ), and omega aragonite saturation (Ω a ). The findings suggest that the observed low pH (7.93) and aragonite saturation state (Ω a = 2.22) values are likely attributed to increased precipitation. This enhanced precipitation resulted in higher river discharge, transporting naturally low-pH water to the island via mixing mechanisms (RiOMar type 2). Daily, decreasing solar radiation may reduce the seawater temperature, simultaneously elevating the pCO 2w levels and reducing pH T . In contrast, elevated precipitation may reduce surface seawater salinity through freshwater dilution. Throughout the diurnal cycle, peak pH T values were recorded during late afternoon hours, likely driven by photosynthetic activity, while minimum values coincided with early morning periods of maximal respiratory activity. These results underscore the dynamic nature of this area and emphasize the need for long-term evaluation
Evaluating the role of physical mechanisms as possible triggers for turbidity currents in a deep ocean seamount
No full textInternational audienceTurbidity currents on continental margins are often attributed to cyclic climate variability and sea-level change, while the causes of deep ocean turbidites are as yet to be tested. The Atlantic Iberian margin provides a unique setting to contrast deep ocean and continental environments, including depression features that further protect from resuspension and erosion by along-slope bottom currents. We present records of low-frequency, non-periodic, climate-independent turbidites from three deep cores covering up to 426,000 years in the Tore seamounts area. By evaluating a range of physical oceanographic mechanisms, the breaking of internal waves and mesoscale Mediterranean-eddies against unstable slopes in the seamounts area arises as the most likely triggers that precondition the recurrence pattern of the observed deep ocean turbidites