Propagation of Thermohaline Anomalies and Their Predictive Potential along the Atlantic Water Pathway
We assess to what extent seven state-of-the-art dynamical prediction systems can retrospectively predict winter sea surface temperature (SST) in the subpolar North Atlantic and the Nordic seas in the period 1970-2005. We focus on the region where warm water flows poleward (i.e., the Atlantic water pathway to the Arctic) and on interannual-to-decadal time scales. Observational studies demonstrate predictability several years in advance in this region, but we find that SST skill is low with significant skill only at a lead time of 1-2 years. To better understand why the prediction systems have predictive skill or lack thereof, we assess the skill of the systems to reproduce a spatiotemporal SST pattern based on observations. The physical mechanism underlying this pattern is a propagation of oceanic anomalies from low to high latitudes along the major currents, the North Atlantic Current and the Norwegian Atlantic Current. We find that the prediction systems have difficulties in reproducing this pattern. To identify whether the misrepresentation is due to incorrect model physics, we assess the respective uninitialized historical simulations. These simulations also tend to misrepresent the spatiotemporal SST pattern, indicating that the physical mechanism is not properly simulated. However, the representation of the pattern is slightly degraded in the predictions compared to historical runs, which could be a result of initialization shocks and forecast drift effects. Ways to enhance predictions could include improved initialization and better simulation of poleward circulation of anomalies. This might require model resolutions in which flow over complex bathymetry and the physics of mesoscale ocean eddies and their interactions with the atmosphere are resolved.
(Journal of Climate. vol. 35, n° 0894-8755, pp. 2111-2131, 17/06/2026)
NERSC, BCCR, BIO / UiB, UiB, BSC-CNS, GFI / BiU, UiB, MPI-M, LOCEAN-VARCLIM, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, DMI, NCAR, CMCC, ISAC, CNR, UNIBO
Primary drivers of multidecadal spatial and temporal patterns of shoreline change derived from optical satellite imagery
Understanding and predicting shoreline change along sandy coasts requires continuous (in both time and space) long-term (decades) shoreline data at good spatial (e.g. 100 s of metres) and temporal (e.g. months) resolution. Publicly available satellite imagery can now provide such time series. However, satellite-derived shorelines (SDS) are associated with uncertainties, particularly at high-energy meso-macrotidal coasts, which challenge the assessment of long-term trends and interannual variability. In this paper we address the 1984–2020 time- and space-evolution of 269 km of high-energy meso-macrotidal sandy coast in southwest France using uncertain (no tide and runup correction) SDS data. The shoreline trends are validated with field data collected over the period 2008–2019. Over 1984–2020, the shoreline eroded by 0.55 m/yr with maximum erosion (accretion) reaching 15.61 m/yr (6.94 m/yr), with the largest changes observed along coasts adjacent to the inlet and estuary mouths. We show that, away from the presence of ebb-tide deltas and swash bars affecting offshore wave transformation and nearshore circulation, the long-term shoreline trend is well explained by the gradients in longshore drift computed from a regional wave hindcast and an empirical longshore transport formula. By averaging the yearly SDS along the entire coastline, we find that interannual shoreline variability is well correlated with the winter West Europe Pressure Anomaly (WEPA), which outscores the other conventional teleconnection pattern indices. WEPA even explains >80 % of the space-averaged shoreline variability over the recent period 2014–2020 when more and higher quality satellite images are available. A more local assessment of the links between climate indices and shoreline response shows that correlation with all climate indices dramatically drops downdrift of the large-scale estuary mouths and inlets. This suggests that along this 10–20 km stretch of downdrift coast, shoreline response is controlled factors internal to the estuary mouth/inlet system. The rest of the coast is mostly controlled by factors external to the system, which are primarily the variability in winter-mean wave height correlated to winter WEPA index. Overall, we demonstrate that an adapted space-averaging of uncorrected (noisy) SDS dataset can allow addressing the time- and space variability of shoreline change and their primary drivers including large-scale climate patterns of atmospheric variability. We also advocate that such SDS analysis can be performed along any coastline in the world in order to guide future model development and application.
(Geomorphology. vol. 413, n° 0169-555X, pp. 108360, 17/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, OCNA, BRGM
Local oceanic CO2 outgassing triggered by terrestrial carbon fluxes during deglacial flooding
Exchange of carbon between the ocean and the atmosphere is a key process that influences past climates via glacial–interglacial variations of the CO2 concentration. The melting of ice sheets during deglaciations induces a sea level rise which leads to the flooding of coastal land areas, resulting in the transfer of terrestrial organic matter to the ocean. However, the consequences of such fluxes on the ocean biogeochemical cycle and on the uptake and release of CO2 are poorly constrained. Moreover, this potentially important exchange of carbon at the land–sea interface is not represented in most Earth system models. We present here the implementation of terrestrial organic matter fluxes into the ocean at the transiently changing land–sea interface in the Max Planck Institute for Meteorology Earth System Model (MPI-ESM) and investigate their effect on the biogeochemistry during the last deglaciation. Our results show that during the deglaciation, most of the terrestrial organic matter inputs to the ocean occurs during Meltwater Pulse 1a (between 15–14 ka) which leads to the transfer of 21.2 Gt C of terrestrial carbon (mostly originating from wood and humus) to the ocean. Although this additional organic matter input is relatively small in comparison to the global ocean inventory (0.06 %) and thus does not have an impact on the global CO2 flux, the terrestrial organic matter fluxes initiate oceanic outgassing in regional hotspots like in Indonesia for a few hundred years. Finally, sensitivity experiments highlight that terrestrial organic matter fluxes are the drivers of oceanic outgassing in flooded coastal regions during Meltwater Pulse 1a. Furthermore, the magnitude of outgassing is rather insensitive to higher carbon-to-nutrient ratios of the terrestrial organic matter. Our results provide a first estimate of the importance of terrestrial organic matter fluxes in a transient deglaciation simulation. Moreover, our model development is an important step towards a fully coupled carbon cycle in an Earth system model applicable to simulations at glacial–interglacial cycles.
(Climate of the Past. vol. 18, n° 1814-9324, pp. 273-292, 17/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MPI-M
Evaluating seasonal sea-ice cover over the Southern Ocean at the Last Glacial Maximum
Southern hemispheric sea-ice impacts ocean circulation and the carbon exchange between the atmosphere and the ocean. Sea-ice is therefore one of the key processes in past and future climate change and variability. As climate models are the only tool available to project future climate change, it is important to assess their performance against observations for a range of different climate states. The Last Glacial Maximum (LGM, ∼21 000 years ago) represents an interesting target as it is a relatively well-documented period with climatic conditions very different from preindustrial conditions. Here, we analyze the LGM seasonal Southern Ocean sea-ice cover as simulated in numerical simulations as part of the Paleoclimate Modelling Intercomparison Project (PMIP) phases 3 and 4. We compare the model outputs to a recently updated compilation of LGM seasonal Southern Ocean sea-ice cover and summer sea surface temperature (SST) to assess the most likely LGM Southern Ocean state. Simulations and paleo-proxy records suggest a fairly well-constrained glacial winter sea-ice edge between 50.5 and 51° S. However, the spread in simulated glacial summer sea-ice is wide, ranging from almost ice-free conditions to a sea-ice edge reaching 53° S. Combining model outputs and proxy data, we estimate a likely LGM summer sea-ice edge between 61 and 62° S and a mean summer sea-ice extent of 14-15×106 km2, which is ∼20 %-30 % larger than previous estimates. These estimates point to a higher seasonality of southern hemispheric sea-ice during the LGM than today. We also analyze the main processes defining the summer sea-ice edge within each of the models. We find that summer sea-ice cover is mainly defined by thermodynamic effects in some models, while the sea-ice edge is defined by the position of Southern Ocean upwelling in others. For models included in both PMIP3 and PMIP4, this thermodynamic or dynamic control on sea-ice is consistent across both experiments. Finally, we find that the impact of changes in large-scale ocean circulation on summer sea-ice within a single model is smaller than the natural range of summer sea-ice cover across the models considered here. This indicates that care must be taken when using a single model to reconstruct past climate regimes.
(Climate of the Past. vol. 18, n° 1814-9324, pp. 845-862, 17/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Multiple phytoplankton community responses to environmental change in a temperate coastal system: A trait-based approach
The effect of environmental change in structuring the phytoplankton communities of the coastal waters of the Eastern English Channel was investigated by applying a trait-based approach on two decades (1996-2019) of monitoring on diatoms and Phaeocystis . We show that phytoplankton species richness in an unbalanced nutrient supply context was influenced by wind-driven processes, ecological specialization for dissolved inorganic phosphorous, temporal niche differentiation, and a competition-defense and/or a growth-defense trade-off, a coexistence mechanism where weak competitors (i.e., slower growing) are better protected against predation. Under the influence of both environmental perturbations (e.g., wind-driven processes, freshwater influence, unbalanced nutrient levels) and biotic interactions (e.g., competition, predation, facilitation), phytoplankton species exhibited specific survival strategies such as investment on growth, adaptation and tolerance of species to environmental stresses, silicification and resource specialization. These strategies have led to more speciose communities, higher productivity, functional redundancy and stability in the last decade. Our results revealed that the unbalanced nutrient reduction facilitated Phaeocystis blooms and that anthropogenic climate warming and nitrate reduction may threaten the diatom communities of the eastern English Channel in a near future. Our results provide strong support for biogeographical historical and niche-based processes in structuring the phytoplankton community in this temperate region. The variety of species responses that we characterized in this region may help to better understand future changes in pelagic ecosystems, and can serve as a basis to consider functional approaches for future ecosystem management.
(Frontiers in Marine Science. vol. 9, n° 2296-7745, pp. 914475, 17/06/2026)
LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], ULCO, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, TUMSAT, OOB, SU, CNRS, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE, UCA Faculté Médecine, UniCA, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, DYNECO, IFREMER
Definition of the Last Glacial Cycle marine stages and chronology
This chapter introduces the historical definition of the Last Glacial Cycle, based on cyclostratigraphy applied to marine oxygen isotopic series derived from foraminiferal records. The division of the Last Glacial Cycle in several substages is discussed, and a chronological framework is presented with special emphasis on a clear definition(s) of the Last Glacial Maximum. Uncertainties on the definitions of the stages are also briefly considered. Sea level and ice volume estimates of each stage are discussed within the framework of the different reconstructions.
(17/06/2026)
GEO-OCEAN, UBS, IFREMER, INSU - CNRS, UBO EPE, CNRS, IPMA, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPHE, PSL, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Dinoflagellate cysts response to climate change during the MIS 12/11 transition
(17/06/2026)
HNHP, MNHN, UPVD, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Architectures 3D et hétérogénéités sédimentaires du réservoir géothermique argilo-sableux de l’Albien d’Île-de-France (Bassin de Paris)
La consommation énergétique en Ile-de-France est majoritairement associée aux besoins en chaleur des bâtiments, puis vient ensuite le secteur des transports. Plus de la moitié de la production de chaleur collective ou individuelle est produite par du combustible fossile. La stratégie énergie-climat de l’Ile-de-France prévoit d’augmenter assez significativement à l’horizon 2030 la production de chaleur par géothermie (x4 par rapport à 2015). Le rythme de développement actuel ne permettra pas d’atteindre cet objectif. Il faudrait atteindre un taux de 6 à 10 fois supérieur. Il devient nécessaire de positionner les doublets de manière optimale en proposant des solutions qui explorent le développement de nouvelles zones. Les réservoirs argilo-sableux du Crétacé inférieur deviennent une cible qu’il convient de mieux caractériser pour optimiser son développement. Récemment (2017) deux doublets géothermiques ont été mis en place dans la nappe de l’Albien sous le plateau de Saclay. Les retours d’expérience sur cette opération ont soulevé des problèmes de forte résistance à la réinjection, ne permettant pas un fonctionnement efficace et durable du système. L’hétérogénéité du réservoir en termes (1) de continuité ou d’épaisseur des niveaux sableux et/ou de niveaux argileux, (2) de minéralogie ou (3) de granulométrie est très peu documentée, ce qui complique son exploitation, et rend incertaine les opérations de ré-injection dans le réservoir. Il devient nécessaire de mieux caractériser ces hétérogénéités dans les réservoirs argilo-sableux du crétacé inférieur (Albien en particulier). Une base de données rassemblant les logs et données pétrophysiques de tous les puits d’Ile- de-France traversant les sables de l’Albien a été organisée sur le géomodelleur Petrel©. Deux cent quarante et un puits, avec diagraphies (avec au moins un Gamma Ray disponible) ou seulement carotté (forage d’Orsay), ont été sélectionnés dans un périmètre allant du nord de la Seine-Saint-Denis jusqu’au sud de l’Essonne et de la Seine et Marne. En incluant le forage carotté historique d’Orsay, ces puits ont été habillés en termes de faciès. Basé sur le rapport BRGM de 2016 (Sévenier et Lasseur, 2016), un ré-examen des faciès et séquences stratigraphiques a été réalisé d’après cette nouvelle base de données. L’étude détaillée permet de reconnaître 7 faciès. Ces faciès ont été attribués à un environnement de dépôt, estuariens à deltaïques en fonction des séquences avec (1) sables grossiers et graviers de la partie chenalisée et influencée par les marées, (2) argiles de replat de marée (mud flat), (3) sables propres de replat sableux (sand flat), (4) sables hétérolithiques de barres sableuses (heterolithic sand bars), (5) sables propres de shoreface, (6) sables argileux d’offshore supérieur et (7) argiles d’offshore inférieur. En tenant compte des concepts de stratigraphie séquentielle et d’empilement vertical des faciès, 3 séquences stratigraphiques de 2nd ordre ont été retrouvées. Douze Maximum Regressive Surfaces et treize Maximum Flooding Surfaces ont été reportées sur les puits et permettent d’illustrer 11 séquences de 3ème ordre, à l’aide de neuf coupes stratigraphiques de corrélation. Ces coupes permettent d’illustrer la géométrie du réservoir. A l’aide de méthodes géostatistiques, plusieurs réalisations numériques rendant compte de l’hétérogénéité 3D des facies ont été proposées. Elles permettent d’identifier les séquences et les localités propices au développement de ce réservoir. Le faciès de sable propre de shoreface de la 3ème séquence 4 et 5 rencontrées dans les Sables de Frécambault présentent une épaisseur d’une trentaine de mètres vers Orsay, et semble une cible idéale pour exploiter le réservoir sur ce site.
(. vol. 82, pp. 6, 17/06/2026)
GEOPS, INSU - CNRS, CNRS, IFPEN, BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The Reading Palaeofire Database: an expanded global resource to document changes in fire regimes from sedimentary charcoal records
Sedimentary charcoal records are widely used to reconstruct regional changes in fire regimes through time in the geological past. Existing global compilations are not geographically comprehensive and do not provide consistent metadata for all sites. Furthermore, the age models provided for these records are not harmonised and many are based on older calibrations of the radiocarbon ages. These issues limit the use of existing compilations for research into past fire regimes. Here, we present an expanded database of charcoal records, accompanied by new age models based on recalibration of radiocarbon ages using IntCal20 and Bayesian age-modelling software. We document the structure and contents of the database, the construction of the age models, and the quality control measures applied. We also record the expansion of geographical coverage relative to previous charcoal compilations and the expansion of metadata that can be used to inform analyses. This first version of the Reading Palaeofire Database contains 1676 records (entities) from 1480 sites worldwide. The database (RPDv1b - Harrison et al., 2021) is available at https://doi.org/10.17864/1947.000345.
(Earth System Science Data. vol. 14, n° 1866-3508, pp. 1109-1124, 17/06/2026)
UMR ISEM, Cirad, IRD, EPHE, PSL, CNRS, UM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The abyssal giant sinkholes of the Blake Bahama Escarpment: evidence of focused deep-ocean carbonate dissolution
This study reports the discovery of abyssal giant depressions located at the toe of the Bahamian carbonate platform, along the Blake Bahama structurally-controlled Escarpment (BBE) that exhibits up to 4 km of submarine elevation above the San Salvador Abyssal Plain (SSAP). Analysis of seismic reflection and bathymetric data collected during the CARAMBAR 2 cruise revealed the presence of 29 submarine depressions; their water depths range from 4584 m to 4967 m whereas their negative reliefs are elliptical in shape, range in diameter from 255 m to 1819 m, and in depth from 30 m to 185 m. The depression alignment trends are parallel to the BBE as well as to structural lineaments of the area, exclusively between 2200 and 5000 m from its toe, and overlies a buried carbonate bench in which a high-amplitude seismic anomaly has been detected. The depression density interestingly increases where the recognized structural lineaments intersect the BBE. Based on their physical attributes (i.e. location, jagged morphologies, water depths), we interpret these depressions as collapse sinkholes rather than pockmarks or plunge pools. The aforementioned observations suggest an atypical relationship between the spatial occurrence of the giant abyssal sinkholes, the carbonate platform tectonic structures, the buried carbonate bench that underlies the hemipelagites in the SSAP and the geomorphology of the area. According to the wider literature that reports fluid seepages along submarine carbonate escarpments, we propose that the ground water entrance during low sea-level stands, the dissolution of evaporites by meteoric water, the platform-scale thermal convection and the seawater entrance at the platform edge most probably collectively act in concert to favor the circulation of brines and therefore the corrosion within the Bahamian carbonate platform. These mechanisms are particularly efficient along the structural heterogeneities (e.g. the Sunniland Fracture Zone, SFZ) which act as fluid conduits localizing the dissolution and control the physiography of the area by maintaining the location of the sedimentary pathways. The dense fluids would migrate along the faults towards the BBE free edge and are subsequently trapped into the buried carbonate bench that laterally disappears below the low-permeability deep-sea hemipelagites of the SSAP. In consequence, the trapped corrosive fluids dissolve the carbonates preferentially along the tectonic structures such as the SFZ. They are this way at the origin of the BBE curvature and generate collapse-structures in the overlying fine-grained deposits finally resulting in the formation of giant abyssal sinkholes. This structurally-directed process of dissolution seems efficient to provide a brines density head to move out down to >4.5 km of water depth and is believed to have played a major role in the BBE 5-6 km erosional retreat.
(Geomorphology. vol. 398, n° 0169-555X, 17/06/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS