Satellite-derived equilibrium shoreline modelling at a high-energy meso-macrotidal beach
Modelling and predicting the future of sandy shorelines is a key challenge in coastal research and is critical for sustainable coastal management. However, currently the most skillful shoreline models strongly rely on data to calibrate the free parameters, and are thus restricted to a few well monitored sites in the world. Here we address the challenges and opportunities offered by optical satellite imagery to provide useful information for equilibrium shoreline model calibration on cross-shore transport dominated sites. We focus on Truc Vert beach, southwest France, where previous work showed good equilibrium model skill to reproduce shoreline change from the time scales of hours (storms) to decades. Satellite derived waterlines are extracted over 11 years (2009–2020) and further transformed into satellite derived shorelines (SDS) with different water level corrections (e.g. tide and/or run up) and varying alongshore averaging lengths, and thus different uncertainties, in order to test model performance. Successively the timeseries duration and sampling frequency required for model calibration were also investigated. The model calibrated using the SDS data showed similar skill as the model calibrated using in-situ alongshore averaged shoreline positions, even for the uncorrected SDS dataset which Root Mean Square Error (RMSE) are approximately 30 m. Alongshore averaging was found to be the only necessary processing of the SDS data while any other site-specific corrections did not significantly improve model skill. Finally to further investigate the effect of sampling frequency and noise in the dataset we performed an analysis using a synthetic shoreline. Our results suggest that the effect of noise is negligible as long as the sampling frequency remains high (dt 30 days). Pending further validation, results show the strong potential of using uncorrected SDS dataset for shoreline model calibration at cross-shore transport dominated sandy coasts.
(Coastal Engineering, n° 0378-3839, pp. 104536, 07/05/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM
Reactivity and bioconcentration of stable cesium in a hyperturbid fluvial-estuarine continuum: A combination of field observations and geochemical modeling
Effective, post-accidental management needs an accurate understanding of the biogeochemical behavior of radionuclides in surface environments at a regional scale. Studies on stable isotopes (element homologs) can improve this knowledge. This work focuses on the biogeochemical behavior of stable cesium (Cs) along a major European fluvial-estuarine system, the Gironde Estuary (SW France). We present results obtained from (i) a long-term monitoring (2014–2017) of dissolved (Csd) and particulate (Csp) Cs concentrations at five sites along the freshwater continuum of the Garonne watershed, (ii) Csd and Csp concentrations during four oceanographic campaigns at contrasting hydrological conditions along longitudinal profiles of the estuarine system, (iii) a 24 h cycle of Csp at the estuary mouth, and (iv) a historical trend of Cs bioconcentration in wild oysters at the estuary mouth (RNO/ROCCH, 1984–2017). In addition, we model the partitioning of Cs within the estuarine environment for clay mineral interactions via PhreeqC. At fluvial sites, we observe a geogenic dependence of the Csp and a seasonal variability of Csd, with a downstream increase of the solid-liquid partitioning (log10 Kd values from 3.64 to 6.75 L kg−1) for suspended particulate matter (SPM) < 200 mg L−1. Along the estuarine salinity gradients, Cs shows a non-conservative behavior where fresh SPM (defined as Cs-depleted particles recently put in contact with Csd) act as a Cs sink during both flood and low discharge (drought) conditions. This sorption behavior was explained by the geochemical model, highlighting the relevance of ionic strength, water and SPM residence times. However, at high salinities, the overall log10 Kd value decreases from 6.02 to 5.20 for SPM ∼300–350 mg L−1 due to the Csd oceanic endmember. Despite wild oysters showing low bioconcentration factors (∼1220 L kg−1) at the estuary mouth, they are sensitive organisms to Cs fluxes.
(Chemosphere. vol. 359, n° 0045-6535, pp. 142266, 05/05/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, KIT, GR, UR, INSU - CNRS, CNRS, IRSN/PSE-ENV/STAAR/LRTA, IRSN/PSE-ENV/STAAR, IRSN, CCEM, IFREMER
Active biomonitoring of river pollution using an ex-situ exposure system with model species
(05/05/2024)
UR EABX, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, RiverLy, INRAE
Exploring embryonic responses of a migratory fish to spawning grounds water quality in a population decline context
(05/05/2024)
UR EABX, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, RiverLy, INRAE
Beyond biostratigraphy: Conodont matters in evolving planetary scenarios
(Marine Micropaleontology. vol. 189, n° 0377-8398, pp. 102364, 01/05/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A New High Spatial Resolution Interferometric Radiometer for L-Band Earth Observation
This paper reports on the main results of SMOS-HR instrument technical study, a new interferometric radiometer dedicated to Soil Moisture and Ocean Salinity measurement from space. The instrument aims at providing enhanced spatial resolution with respect to SMOS and integrating robust RFI (RF Interference) mitigation technique. The instrument key performance requirements and the architecture features and trade-offs are exposed in this paper.
(. vol. 129, pp. 4222-4225, 01/05/2024)
LAPLACE, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse, ADS, IRESNE, CEA, CNES, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, (U 726), UPD7, INSERM, CESBIO, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, INRAE, CERFACS
Multi-proxy paleoenvironmental reconstruction of Robertson Bay, East Antarctica, since the last glacial period
Antarctic fjords and coastal bays are excellent traps for sediment and represent key areas for high-resolution investigation of past environmental conditions. Robertson Bay is an understudied coastal area located at the confluence of the Ross Sea and the Southern Ocean. Recently obtained seafloor morphology data indicate the presence of a cross-shelf elongated valley, composed of three minor basins separated by sills and seabed ridges with an arcuate shape. Several cores were collected within the basins, and investigated using a multiproxy approach including sedimentological, chemical, geochemical, and micropaleontological characterization to reconstruct the paleoenvironmental evolution from the last glacial period to present. The ages of two of these cores are constrained using ramped pyrolysis oxidation radiocarbon dating. Four sedimentary facies were recognised from which we developed a sedimentary model covering the last 21,000 years (21 ka BP). Our record provide evidence for a covering ice shelf cover from 21 to 16.5 ka BP, which gradually receded between 16,5 and 11 ka BP due to the progressive intrusion of modified Circumpolar Deep Water, thereby promoting the formation of Ice Shelf Water and High Salinity Shelf Water. From 11 to 5,8 ka BP, the ice shelf continued shrinking and nutrient-rich of modified Circumpolar Deep Water penetration onto the continental shelf progressively favoured diatom blooms and a general increase in primary productivity until 5.8 ka BP. The Late Holocene is characterised by an alternation of prolonged sea ice cover with stratified water column and strong bottom current with prolonged sea-ice free season with the intrusion of modified Circumpolar Deep Water and very slow energy bottom current.
(Quaternary Science Reviews. vol. 332, n° 0277-3791, pp. 108629, 01/05/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impact of volcanic eruptions on CMIP6 decadal predictions: a multi-model analysis
Abstract. In recent decades, three major volcanic eruptions of different intensity have occurred (Mount Agung in 1963, El Chichón in 1982 and Mount Pinatubo in 1991), with reported climate impacts on seasonal to decadal timescales that could have been potentially predicted with accurate and timely estimates of the associated stratospheric aerosol loads. The Decadal Climate Prediction Project component C (DCPP-C) includes a protocol to investigate the impact of volcanic aerosols on the climate experienced during the years that followed those eruptions through the use of decadal predictions. The interest of conducting this exercise with climate predictions is that, thanks to the initialisation, they start from the observed climate conditions at the time of the eruptions, which helps to disentangle the climatic changes due to the initial conditions and internal variability from the volcanic forcing. The protocol consists of repeating the retrospective predictions that are initialised just before the last three major volcanic eruptions but without the inclusion of their volcanic forcing, which are then compared with the baseline predictions to disentangle the simulated volcanic effects upon climate. We present the results from six Coupled Model Intercomparison Project Phase 6 (CMIP6) decadal prediction systems. These systems show strong agreement in predicting the well-known post-volcanic radiative effects following the three eruptions, which induce a long-lasting cooling in the ocean. Furthermore, the multi-model multi-eruption composite is consistent with previous work reporting an acceleration of the Northern Hemisphere polar vortex and the development of El Niño conditions the first year after the eruption, followed by a strengthening of the Atlantic Meridional Overturning Circulation the subsequent years. Our analysis reveals that all these dynamical responses are both model- and eruption-dependent. A novel aspect of this study is that we also assess whether the volcanic forcing improves the realism of the predictions. Comparing the predicted surface temperature anomalies in the two sets of hindcasts (with and without volcanic forcing) with observations we show that, overall, including the volcanic forcing results in better predictions. The volcanic forcing is found to be particularly relevant for reproducing the observed sea surface temperature (SST) variability in the North Atlantic Ocean following the 1991 eruption of Pinatubo.
(Earth System Dynamics. vol. 15, n° 2190-4979, pp. 501-525, 26/04/2024)
BSC-CNS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CMCC, DMI, ICREA, ECCC, LOCEAN-VARCLIM, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, BSC, UNISTRA, CNRS, AOS Program, GFDL, NOAA, NCAR
Hybrid modeling of karstic springs: Error correction of conceptual reservoir models with machine learning
ABSTRACT Accurate spring discharge modeling and prediction is crucial for water management, helping authorities optimize use, manage variability, and prepare for droughts. Developing reliable simulation and forecasting tools is essential for effective management of groundwater resources from karstic springs. Although hybrid modeling approaches have been explored in hydrology, their application to spring discharge modeling is underexplored. Previous studies have focused on conceptual/distributed or data-driven models separately, missing the potential advantages of combining them. This creates a research gap in exploring the benefits of hybrid models for spring discharge. This study developed a hybrid model combining a conceptual GR5J model with Random Forests to simulate spring discharge from Bordeaux's largest karst aquifer. Model performance was assessed through comparison with the individual GR5J, RF, and benchmark models (weekly average of observed values). The hybrid model outperformed all models. Evaluation using actual meteorological data found the hybrid model achieved the highest accuracy by reducing GR5J simulation errors by 22%. When considering meteorological uncertainty, the hybrid model outperformed the individual GR5J, RF and benchmark models by 11, 30 and 47% respectively. The study findings suggest combining conceptual and machine learning approaches can improve spring discharge simulations, opening promising opportunities for enhanced forecasting in karst aquifers.
(Water Supply. vol. 24, pp. 1559-1573, 26/04/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Editorial: Advances in the environmental distribution of less studied elements
This Research Topic focused on the advancements in our understanding of the environmental processes governing the transport and fate of several elements within natural biogeochemical cycles. The target elements were a group characterized by potential environmental impacts, including emerging contaminants (e.g., critical elements) and radionuclides.
(Frontiers in Marine Science. vol. 11, n° 2296-7745, pp. 1413033, 25/04/2024)
FSU, KIT, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, FSU, IRSN/PSE-ENV/STAAR/LRTA, IRSN/PSE-ENV/STAAR, IRSN