The Sahelian agro-ecosystem vulnerability to an acceleration of ice-sheet melting during the 21st century
During the 20th century, Sahelian drought episodes like those between 1972 and 1982 showed the vulnerability of the Sahelian agro-ecosystem provoking significant intraregional southward human migrations, to or near the coast. According to the latest IPCC report, the Sahel could become increasingly impacted by climate change during the 21st century because of a lagged and shorter rainfall season having the potential to induce a drastic destabilization of the Sahelian agro-ecosystem and to heavily impact the population. Such effects could be further amplified by a net increase of the Sahelian population. Drastic climate changes over tropical areas also occurred in the past: weakening of the West African Monsoon and megadrought Sahelian episodes have been reported with a close correspondence between the large rainfall decrease and the massive freshwater discharges following ice-sheet melting or iceberg surges. During the last decades a continuous acceleration of ice-sheet mass loss has been observed and post IPCC-AR5 studies suggest the ice-sheet contribution to future sea-level rise could be revised upward due partly to the lack of an accurate representation of ice-ocean interactions. The release of freshwater discharge in response to ice-sheet instability could have large consequences on the most vulnerable regions, such as the tropical areas. To investigate the impacts of large ice-sheet instability during the 21st century, we first explore the climatic signature of Greenland or Antarctic ice-sheet collapse scenarios corresponding to 0.5 to 1.5 meter of sea-level rise, superimposed to the RCP8.5 scenario. We show that a freshwater discharge coming from Greenland melting induces a significant decrease of summer monsoon rainfall, that may lead to changes in agricultural practices. Combined with increasing demography, this has the potential to induce important human migration flows. Without adaptation measures, we estimate that tens to hundreds million people could be forced to leave the Sahel by the end of the 21st century, not accounting for the direct migratory impact of sea-level rise over coastal areas.
(. vol. 18, pp. 7977, 22/06/2026)
LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PARVATI, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEARC, UVSQ, UCM
Dynamics of particulate organic matter in a coastal system characterized by the occurrence of marine mucilage – A stable isotope study
In coastal systems, particulate organic matter (POM) originates from various autochthonous and allochthonous organic matter sources. Also, some coastal systems are characterized by the occurrence of large amounts of mucilaginous material of biologic origin (i.e. phytoplankton, bacteria), which aggregates and potentially traps other organisms and particles present in the water column. This study focuses on POM origin and spatio-temporal dynamics in the South-East coast of the Bay of Biscay, an area subject to mucilage occurrence. In order to investigate POM quantitative and qualitative (C and N elemental and isotopic ratios) characteristics, sampling was performed over an annual cycle at two sites experiencing different mucilage occurrence and river influence. Contribution of phytoplankton, terrestrial POM and anthropogenic POM to coastal-POM composition was calculated using a three-sources mixing model. Overall, phytoplankton dominated the coastal-POM composition at all seasons, sites and most of the depths (71.6 ± 24.2%). Terrestrial-POM contribution was moderate (22.7 ± 21.8%) and anthropogenic-POM contribution was usually negligible (5.7 ± 7.4%). Both sites mainly exhibited similar vertical and temporal variations in terms of POM origin and dynamics: terrestrial-POM contribution increased with depth and was higher in winter at all depths and in autumn in bottom waters, compared to other seasons. The main differences between both sites were related to the vertical dynamics of the terrestrial contribution to the coastal POM. Horizontal, vertical and temporal variation of POM composition was linked to processes driving the sedimentary hydrodynamics: the river flow, the direction of the river plume and events of sediment resuspension/deposition. During the study period, the mucilage occurred only as flocs (small aggregates). The mucilage was of autochthonous origin and did not trap detectable amount of allochthonous material. © 2016 Elsevier B.V.
(Journal of Sea Research (JSR). vol. 116, n° 1385-1101, pp. 12--22, 22/06/2026)
LPCNO, INSA Toulouse, INSA, Comue de Toulouse, ICT, IRD, UT3, Comue de Toulouse, INC-CNRS, CNRS, Toulouse INP, Comue de Toulouse, IRSAMC, UT3, Comue de Toulouse, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IPREM, UPPA, INC-CNRS, CNRS, VUB
Potential of Video Cameras in Assessing Event and Seasonal Coastline Behaviour: Grand Popo, Benin (Gulf of Guinea)
In this study, we explore the potential of a nearshore video system to obtain a long-term estimation of coastal variables (shoreline, beach slope, sea level elevation and wave forcing) at Grand Popo beach, Benin, West Africa, from March 2013 to February 2015. We first present a validation of the video system with field data over a 10-day experiment conducted on Grand Popo beach in 2014. Secondly, 2-years daily and monthly timeseries are extracted and their variability is described as a function of regional forcing and climatic modes. All variables show large monthly variability. The longshore sediment transport estimated locally from video is in agreement with that derived from Era-Interim wave data re-analyses. Results show that the shoreline responds predominantly to tides at the event scale and to waves. Overall, this study suggests that video stations are efficient tools to monitor coastal processes over the long term, in complement with other conventional approaches. Although no clear conclusions can be drawn on inter-annual variability, the results show that it is important to build up extended coastal observation networks to address coastline changes over a wide range of scales.
(Journal of Coastal Research, n° 0749-0208, pp. 442-446, 22/06/2026)
ECOLA, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, OLVAC, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, CICESE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, AOS Program, GFDL, NOAA, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS
Comment réduire l'impact des rejets urbains d'une agglomération sur le milieu récepteur ? Retours sur les résultats du programme Etiage et sur la prise en compte progressive de la qualité dans le mode de gestion de Bordeaux Métropole
Pour répondre aux ambitions de Bordeaux Métropole et l'accompagner dans la reconquête d'un état écologique acceptable de l'estuaire, un consortium s'est formé autour du programme Etiage. Ce programme a permis d'expliciter les facteurs responsables de la qualité biogéochimique de la Gironde.
(TSM. Techniques Sciences Méthodes, n° 0299-7258, pp. 79-97, 22/06/2026)
IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EABX, IRSTEA, IRSTEA
Carbon emission along a eutrophication gradient in temperate riverine wetlands: effect of primary productivity and plant community composition
1. Eutrophication increases primary productivity and favours the predominance of floating vegetation in wetlands. Carbon (C) fluxes in wetlands are strongly driven by primary productivity and can differ by vegetation type. However, to the best of our knowledge, the role of eutrophication in C fluxes has rarely been assessed. 2. Consequently, we aimed to measure the seasonal variation in carbon dioxide (CO2) and methane (CH4) fluxes at six aquatic sites in four temperate wetlands, ranging along a gradient of sediment total phosphorus content, and determine whether C fluxes correlate with above-ground net primary productivity (ANPP) and plant community composition along this eutrophication gradient. 3. Daytime CO2 emissions were significantly and negatively correlated with wetland net primary productivity as a result of the greater C fixation by photosynthesis during the peak of production. Conversely, CH4 emissions were significantly and positively correlated with wetland ANPP, possibly due to higher litter production and anaerobic decomposition. 4. The highest CH4 emissions were observed above floating vegetation, which favoured hypoxic conditions in the water column. CH4 emissions including ebullition were higher above macroalgal belts than above vascular plants with floating leaves. CH4 emissions without ebullition (i.e. resulting from plant transport and diffusion) better correlated with the abundance of macroalgae than with the abundance of vascular plants with floating leaves. 5. Our results suggest that eutrophication may greatly modify CO2 and CH4 emissions from wetlands through changes in vegetation type and productivity.
(Freshwater Biology. vol. 61, n° 0046-5070, pp. 1405–1420, 22/06/2026)
LEHNA, UCBL, ENTPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LCE, CNRS, UMLP, UBFC
Spatial and seasonal contrasts of sedimentary organic matter in floodplain lakes of the central Amazon basin
In this study, we investigated the seasonal and spatial pattern of sedimentary organic matter (SOM) in five floodplain lakes of the central Amazon basin (Cabaliana, Janauaca, Canaçari, Mirituba and Curuai) which have different morphologies, hydrodynamics and vegetation cover-ages. Surface sediments were collected in four hydrological seasons: low water (LW), rising water (RW), high water (HW) and falling water (FW) in 2009 and 2010. We investigated commonly used bulk geochemical tracers such as the C : N ratio and the stable isotopic composition of organic carbon (δ 13 C org). These results were compared with lignin phenol parameters as an indicator of vascular plant detritus and branched glycerol dialkyl glycerol tetraethers (brGDGTs) to trace the input of soil organic matter (OM) from land to the aquatic settings. We also applied the crenarchaeol as an indicator of aquatic (rivers and lakes) OM. Our data showed that during the RW and FW seasons, the surface sediments were enriched in lignin and brGDGTs in comparison to other seasons. Our study also indicated that floodplain lake sediments primarily consisted of allochthonous, C 3 plant-derived OM. However, a downstream increase in C 4 macrophyte-derived OM contribution was observed along the gradient of increasing open waters-i.e., from upstream to downstream. Accordingly , we attribute the temporal and spatial difference in SOM composition to the hydrological dynamics between the floodplain lakes and the surrounding flooded forests.
(Biogeosciences. vol. 13, n° 1726-4170, pp. 467-482, 22/06/2026)
UFF, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, NIOZ, UMR ISEM, Cirad, IRD, EPHE, PSL, UM, CNRS, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, IRD
Improving past sea surface temperature reconstructions from the Southern Hemisphere oceans using planktonic foraminiferal census data
We present an improved database of planktonic foraminiferal census counts from the Southern Hemisphere oceans (SHO) from 15°S to 64°S. The SHO database combines three existing databases. Using this SHO database, we investigated dissolution biases that might affect faunal census counts. We suggest a depth/ math formula threshold of ~3800 m/ math formula = ~ −10 to −5 µmol/kg for the Pacific and Indian Oceans and ~4000 m/ math formula = ~0 to 10 µmol/kg for the Atlantic Ocean, under which core-top assemblages can be affected by dissolution and are less reliable for paleo-sea surface temperature (SST) reconstructions. We removed all core tops beyond these thresholds from the SHO database. This database has 598 core tops and is able to reconstruct past SST variations from 2° to 25.5°C, with a root mean square error of 1.00°C, for annual temperatures. To inspect how dissolution affects SST reconstruction quality, we tested the data base with two “leave-one-out” tests, with and without the deep core tops. We used this database to reconstruct summer SST (SSST) over the last 20 ka, using the Modern Analog Technique method, on the Southeast Pacific core MD07-3100. This was compared to the SSST reconstructed using the three databases used to compile the SHO database, thus showing that the reconstruction using the SHO database is more reliable, as its dissimilarity values are the lowest. The most important aspect here is the importance of a bias-free, geographic-rich database. We leave this data set open-ended to future additions; the new core tops must be carefully selected, with their chronological frameworks, and evidence of dissolution assessed.
(Paleoceanography. vol. 31, n° 0883-8305, pp. 822-837 (IF 3,738), 22/06/2026)
LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEOPS, UP11, CNRS, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, NIWA
Groenland. Climat, Ecologie, Société
(pp. 300, 22/06/2026)
LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LCE, CNRS, UMLP, UBFC, CEFE, UPVM, INRA, Montpellier SupAgro, EPHE, PSL, UM, CNRS, IRD [Occitanie], IRD, Montpellier SupAgro, CEARC, UVSQ, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Chronostratigraphie et paléoenvironnements du Pléistocène supérieur sur la bordure sud-Atlantique du Maroc. Les séquences de l'oued supérieur.
(pp. 206-227, 22/06/2026)
UPVD, LAMPEA, AMU, CNRS, MC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEOTRAC, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, OCEANIS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Unprecedented coring performance with the upgraded Research Vessel Marion Dufresne
(Past Global Changes Magazine. vol. 24, n° 2411-605X, pp. 27, 22/06/2026)
CLIMAG, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CNRS, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS