Variations and significance of Mg/Sr and 87Sr/86Sr in a karst cave system in southwest China
The geochemical compositions of cave drip water and speleothems such as Mg, Sr, Mg/Ca, Sr/Ca, and ⁸⁷Sr/⁸⁶Sr are considered to be responsive to changes in the local climate and hydrological conditions. Systematic monitoring was performed on the Mg and Sr contents, Mg/Sr ratio and ⁸⁷Sr/⁸⁶Sr of soil, soil water, cave drip water, and the active speleothems (AS) in Furong Cave in Chongqing, southwest China, during 2009–2018 (A.D). The results were interpreted in conjunction with the changes in the ⁸⁷Sr/⁸⁶Sr ratios to explore the main sources and controlling factors of Sr and other trace elements in drip water. (1) Due to the decrease in winter and spring rainfall, the residence time of water in the soil was prolonged, which resulted in increasing of Mg and Sr concentrations and ⁸⁷Sr/⁸⁶Sr ratios in soil water. It indicates that the trace element contents of soil water reflect seasonal changes of the rainfall. (2) The Mg and Sr contents were higher in drip water than in the soil water, as well as the ⁸⁷Sr/⁸⁶Sr of the cave drip-water was closer to that of the bedrock, which indicates that the overlying bedrock was the main source of the trace elements in the drip water and the speleothems in Furong Cave. (3) Mg contents and Mg/Sr ratios in drip water and AS showed decreasing trend, which may be affected by the shorter water-rock contact time due to the increasing annual rainfall in the monitoring period. (4) The Sr contents in AS might be affected by the growth rate of AS because of the similar increasing trend. (5) The Mg and Sr contents and the Mg/Sr ratios of the drip water and AS did not exhibit seasonal variations due to the mixing of the fissure water and complex hydrology condition of the overlying bedrock, however, the geochemical indexes (Mg and Mg/Sr ratio) showed an opposite trend to the annual rainfall variation. In short, this study highlights the responses of the changes of Mg, Sr and Mg/Sr ratios of drip water and AS to the rainfall on the multi-year timescale, which contributes critical insights into the paleoclimate interpretation of proxies of speleothems in the cave with hundreds of meters’ thick bedrock.
(Journal of Hydrology. vol. 596, n° 0022-1694, pp. 126140, 01/05/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Tidal turbines in the estuarine environment: from identifying optimal location to environmental impact
Estuaries that feature large tidal ranges (macrotidal) have recently received attention for their potential to generate energy by tidal stream turbines. As estuaries are delicate ecosystems and often have large human populations residing on their shores, determining where to place the turbines and how they will impact the hydrodynamics and sediment transport of these systems is vital to their successful implementation. The aim of this study is to provide a framework for assessing an estuary for turbine placement, including determining how the turbines will impact the environment (focusing on the physics), and examining other items that could peripherally affect the tidal turbine farm location or impact. This work was carried out using the Gironde Estuary as a case study and included a combination of in-situ data collection and numerical modeling. In terms of the turbine farm impact on the hydrodynamics and Suspended Sediment Concentration (SSC), results showed that the inclusion of a farm reduced currents up to 10% and decreased SSC up to 15 mg/l. The decrease in SSC was due to the attenuated current velocities decreasing friction velocity and thus near bottom generated turbulence that suspends bottom sediment. Over time, the decreased SSC will lead to sediment accumulation and new bottom features.
(Renewable Energy. vol. 169, n° 0960-1481, pp. 700-713, 01/05/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Molecular Impacts of Dietary Exposure to Nanoplastics Combined or Not with Arsenic in the Caribbean Mangrove Oysters (Isognomon alatus)
Nanoplastics (NPs) are anthropogenic contaminants that raise concern, as they cross biological barriers. Metals’ adsorption on NPs’ surface also carries ecotoxicological risks to aquatic organisms. This study focuses on the impacts of three distinct NPs on the Caribbean oyster Isognomon alatus through dietary exposure. As such, marine microalgae Tisochrysis lutea were exposed to environmentally weathered mixed NPs from Guadeloupe (NPG), crushed pristine polystyrene nanoparticles (PSC), and carboxylated polystyrene nanoparticles of latex (PSL). Oysters were fed with NP-T. lutea at 10 and 100 µg L−1, concentrations considered environmentally relevant, combined or not with 1 mg L−1 pentoxide arsenic (As) in water. We investigated key gene expression in I. alatus’ gills and visceral mass. NP treatments revealed significant induction of cat and sod1 in gills and gapdh and sod1 in visceral mass. As treatment significantly induced sod1 expression in gills, but once combined with any of the NPs at both concentrations, basal mRNA levels were observed. Similarly, PSL treatment at 100 µg L−1 that significantly induced cat expression in gills or sod1 in visceral mass showed repressed mRNA levels when combined with As (reduction of 2222% and 34%, respectively, compared to the control). This study suggested a protective effect of the interaction between NPs and As, possibly by decreasing both contaminants’ surface reactivity.
(Nanomaterials. vol. 11, n° 2079-4991, 01/05/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Antarctic Polar Front migrations in the Kerguelen Plateau region, Southern Ocean, over the past 360 kyrs
(Global and Planetary Change, n° 0921-8181, pp. 103526, 01/05/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CLIMAG, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Evaluating the impact of Mediterranean overflow on the large-scale Atlantic Ocean circulation using neodymium isotopic composition
(Palaeogeography, Palaeoclimatology, Palaeoecology. vol. 570, n° 0031-0182, pp. 110359, 01/05/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GEOPS, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CLIM, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Wave-Filtered Surf Zone Circulation under High-Energy Waves Derived from Video-Based Optical Systems
This paper examines the potential of an optical flow video-based technique to estimate wave-filtered surface currents in the nearshore where wave-breaking induced foam is present. This approach uses the drifting foam, left after the passage of breaking waves, as a quasi-passive tracer and tracks it to estimate the surface water flow. The optical signature associated with sea-swell waves is first removed from the image sequence to avoid capturing propagating waves instead of the desired foam motion. Waves are removed by applying a temporal Fourier low-pass filter to each pixel of the image. The low-pass filtered images are then fed into an optical flow algorithm to estimate the foam displacement and to produce mean velocity fields (i.e., wave-filtered surface currents). We use one week of consecutive 1-Hz sampled frames collected during daylight hours from a single fixed camera located at La Petite Chambre d’Amour beach (Anglet, SW France) under high-energy conditions with significant wave height ranging from 0.8 to 3.3 m. Optical flow-computed velocities are compared against time-averaged in situ measurements retrieved from one current profiler installed on a submerged reef. The computed circulation patterns are also compared against surf-zone drifter trajectories under different field conditions. Optical flow time-averaged velocities show a good agreement with current profiler measurements: coefficient of determination (r2)= 0.5–0.8; root mean square error (RMSE) = 0.12–0.24 m/s; mean error (bias) =−0.09 to −0.17 m/s; regression slope =1±0.15; coherence2 = 0.4–0.6. Despite an underestimation of offshore-directed velocities under persistent wave breaking across the reef, the optical flow was able to correctly reproduce the mean flow patterns depicted by drifter trajectories. Such patterns include rip-cell circulation, dominant onshore-directed surface flow and energetic longshore current. Our study suggests that open-source optical flow algorithms are a promising technique for coastal imaging applications, particularly under high-energy wave conditions when in situ instrument deployment can be challenging.
(Remote Sensing. vol. 13, n° 2072-4292, pp. 1874, 01/05/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SIAME, UPPA
Role of Atmospheric Indices in Describing Inshore Directional Wave Climate in the United Kingdom and Ireland
Improved understanding of how our coasts will evolve over a range of time scales (years-decades) is critical for effective and sustainable management of coastal infrastructure. A robust knowledge of the spatial, directional and temporal variability of the inshore wave climate is required to predict future coastal evolution and hence vulnerability. However, the variability of the inshore directional wave climate has received little attention, and an improved understanding could drive development of skillful seasonal or decadal forecasts of coastal response. We examine inshore wave climate at 63 locations throughout the United Kingdom and Ireland (1980–2017) and show that 73% are directionally bimodal. We find that winter-averaged expressions of six leading atmospheric indices are strongly correlated (r = 0.60–0.87) with both total and directional winter wave power (peak spectral wave direction) at all studied sites. Regional inshore wave climate classification through hierarchical cluster analysis and stepwise multi-linear regression of directional wave correlations with atmospheric indices defined four spatially coherent regions. We show that combinations of indices have significant skill in predicting directional wave climates (R2 = 0.45–0.8; p < 0.05). We demonstrate for the first time the significant explanatory power of leading winter-averaged atmospheric indices for directional wave climates, and show that leading seasonal forecasts of the NAO skillfully predict wave climate in some regions.
(Earth's Future. vol. 9, n° 2328-4277, pp. e2020EF001625, 01/05/2021)
SBMS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOPS, IRD, IFREMER, INSU - CNRS, UBO EPE, CNRS, EMPS
How to turn kilos of mud into megabytes of data? 10 years of efforts in curating lake sediment cores and their associated results
Here we present a series of connected efforts aiming at curating sediment cores and their related data. Far to be isolated, these efforts were conducted within national structured projects and led to the development of digital solutions and good practices in-line with international standards and practices.Our efforts aimed at ensuring FAIR-compatible practices (Plomp, 2020; Wilkinson et al., 2016) throughout the life cycle of sediment cores, from fieldwork to published data. We adopted a step-by-step, bottom-up strategy to formalize a dataflow, mirroring our workflow. We hence created a fieldwork mobile application (CoreBook) to gather information during coring operations and inject them toward the French national virtual core repository “Cyber-Carothèque Nationale” (CCN). At this stage, the allocation of an international persistent unique identifier was crucial and we naturally chose the IGSN.Beyond the traceability of samples, the curation of analysis data remains challenging. Most international repository (e.g. NOAA palaeo-data, PANGAEA) have taken the problem from the top by offering facilities to display published dataset with persistant unique identifier (DOI). Yet, those data are only a fraction of the gross amount of acquired data. Moreover, those repositories have very low requirements when it comes to the preservation and display of metadata, in particular analytical parameters, but also fieldwork data which are essential for data reusability. Finally, these repositories do not permit to get a synoptic view on the several strata of analyses that have been conducted on the same core through different research programs and publications. A partial solution is proposed by the eLTER metadata standard DEIMS, which offers a discovery interface of rich metadata. In order to bridge the gap between generalist data repositories and samples display systems (such as CCN, but also IMLGS, to cite an international system), we developed a data repository and visualizer dedicated to the re-use of lake sediment cores, samples and sampling locations (ROZA Retro-Observatory of the Zone Atelier). This system is still a prototype but opens yet interesting perspectives.Finally, the digital evolution of science allows the worldwide diffusion of data processing freewares. In that framework, we developed “Serac” an open-source R package to establish radionuclide-based age models following the most common sedimentation hypotheses (serac,). By implementing within this R package the input of a rich metadata file that gathers links to IGSN and other quality metadata, we are linking fieldwork metadata, the physical storage of the core and the analytical metadata. Indeed, Serac also stores data processing procedure in a standardized way.. We hence think that the development of such softwares could help in the spreading of good practices in data curation and favour the use of unique identifiers.By tackling all aspects of data creation and curation throughout a lake sediment core life cycle, we are now able to propose a theoretical model of data curation for this particular type of sample that could serve as the sole for further developments of integrated data curation systems.https://doi.org/10.5194/egusphere-egu21-15037
(pp. https://meetingorganizer.copernicus.org/EGU21/EGU21-15037.html, 29/04/2021)
EDYTEM, USMB [Université de Savoie] [Université de Chambéry], CNRS, Fédération OSUG, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, DTI, INSU - CNRS, CNRS, CARRTEL, USMB [Université de Savoie] [Université de Chambéry], INRAE, Fédération OSUG, LETG, UNICAEN, NU, UA, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN, LETG - Brest, LETG, UNICAEN, NU, UA, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN
Sea Surface Temperatures in the Indian Sub‐Antarctic Southern Ocean for the Last Four Interglacial Periods
(Geophysical Research Letters. vol. 48, n° 0094-8276, 28/04/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Earth, Our Living Planet
Earth is, to our knowledge, the only life-bearing body in the Solar System. This extraordinary characteristic dates back almost 4 billion years. How to explain that Earth is teeming with organisms and that this has lasted for so long? What makes Earth different from its sister planets Mars and Venus? The habitability of a planet is its capacity to allow the emergence of organisms. What astronomical and geological conditions concurred to make Earth habitable 4 billion years ago, and how has it remained habitable since? What have been the respective roles of non-biological and biological characteristics in maintaining the habitability of Earth? This unique book answers the above questions by considering the roles of organisms and ecosystems in the Earth System, which is made of the non-living and living components of the planet. Organisms have progressively occupied all the habitats of the planet, diversifying into countless life forms and developing enormous biomassesover the past 3.6 billion years. In this way, organisms and ecosystems "took over" the Earth System, and thus became major agents in its regulation and global evolution. There was co-evolution of the different components of the Earth System, leading to a number of feedback mechanisms that regulated long-term Earth conditions. For millennia, and especially since the Industrial Revolution nearly 300 years ago, humans have gradually transformed the Earth System. Technological developments combined with the large increase in human population have led, in recent decades, to major changes in the Earth's climate, soils, biodiversity and quality of air and water. After some successes in the 20th century at preventing internationally environmental disasters, human societies are now facing major challenges arising from climate change. Some of these challenges are short-term and others concern the thousand-year evolution of the Earth's climate. Humans should become the stewards of Earth.
(pp. 572, 22/04/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOV, INSU - CNRS, SU, CNRS, IMEV, INSU - CNRS, SU, CNRS