Chapter 4 - Introduction to the Last Deglaciation climate
This chapter briefly describes the long-term climate evolution, as well as, the superimposed abrupt climate shifts that have punctuated the Last Deglaciation, that is, the pre-Heinrich Stadial 1 and the Heinrich Stadial 1, the Bølling–Allerød Interstadial and the Younger Dryas Stadial. A short description of the impact of these abrupt changes in the North Atlantic, Greenland and Europe is also provided as a prelude to the following chapters.
(pp. 33-36, 01/01/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Chapter 7 - The Younger Dryas Stadial
The Younger Dryas (YD) stadial is the last extreme cold event detected in the northern hemisphere during the last deglaciation. Many theories have been proposed to explain the causes of this event. Currently, the most accepted one is that the increased meltwater discharges into the North Atlantic or Arctic Sea produced a series of changes in ocean circulation and sea ice cover that triggered substantial shifts in the atmospheric circulation patterns. The impact of these changes is marked by a series of climate shifts within the YD stadial with a complex spatial distribution of hydroclimate in Europe in each phase.
(pp. 51-57, 01/01/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Trajectories of nutrients concentrations and ratios in the French coastal ecosystems: 20 years of changes in relation with large-scale and local drivers
used to determine ecosystem trajectories as well as typologies of ecosystem trajectories. It appeared that most of the French coastal ecosystems exhibited trajectories towards a decrease in nutrients concentrations. Differences in trajectories mainly depended on continental and human influences, as well as on climatic regimes. One single ecosystem exhibited very different trajectories, the Arcachon Bay with an increase in nutrients concentrations. Ecosystem trajectories based on ordination techniques were proven to be useful tools to monitor ecosystem changes. This study highlighted the importance of local environments and the need to couple uni-and multi-ecosystem studies. Although the studied ecosystems were influenced by both local and large-scale climate, by anthropogenic activities loads, and that their trajectories were mostly similar based on their continental influence, non-negligible variations resulted from their internal functioning.
(Science of the Total Environment. vol. 857, n° 0048-9697, pp. 159619, 01/01/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, AD2M, SU, CNRS, SBR, SU, CNRS, LOMIC, INSU - CNRS, SU, CNRS, OOB, SU, CNRS
New Southern Ocean transfer function for subsurface temperature prediction using radiolarian assemblages
(Marine Micropaleontology. vol. 178, n° 0377-8398, pp. 102198, 01/01/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Seasonal, Diurnal, and Tidal Variations of Dissolved Inorganic Carbon and pCO2 in Surface Waters of a Temperate Coastal Lagoon (Arcachon, SW France)
We report on diurnal, tidal, and seasonal variations of dissolved inorganic carbon (DIC), water partial pressure of CO2 (pCO2), and associated water–air CO2 fluxes in a tidal creek of a temperate coastal lagoon with 70% of intertidal flats, during eight tidal/diurnal cycles and two consecutive years covering all seasons. Surface waters of the lagoon were always slightly oversaturated in CO2 with respect to the atmosphere with an average pCO2 value of 496 ± 36 ppmv. Seasonally, subsurface water pCO2 values were controlled by both temperature and biological/tidal advection effects that compensated each other and resulted in weak annual variations. High-resolution temporal pCO2 records reveal that the highest fluctuations (192 ppmv) occurred at the tidal/diurnal scale as a result of biological activity, advection from the tidal flat, and porewater pumping that all contributed to water pCO2 and carbonate chemistry variations. Total alkalinity (TA) versus salinity plots suggest a net production of alkalinity in the lagoon attributed to benthic carbonate dissolution and/or anaerobic degradation of organic matter. We specifically highlighted that for the same salinity range, during flooding, daytime pCO2 were generally lower than nighttime pCO2 values because of photosynthesis, whereas during ebbing, daytime pCO2 were higher than nighttime pCO2 values because of heating. Waters in the lagoon were a relatively weak CO2 source to the atmosphere over the year compared to other estuarine and lagoon waters elsewhere, and to sediment-air fluxes measured simultaneously by atmospheric Eddy Covariance (EC) in the Arcachon lagoon. Because of low values and small variations of the air-sea pCO2 gradient, the variability of fluxes calculated using the piston velocity parameterization was greatly controlled by the wind speed at the diurnal and, to a lesser extent, seasonal time scales. During the emersion, the comparison of these pCO2 data in the tidal creek with EC fluxes measured 1.8 km away on the tidal flat suggests high heterogeneity in air-sea CO2 fluxes, both spatially and at short time scales according to the inundation cycle and the wind speed. In addition to tidal pumping when the flat becomes emerged, our data suggest that lateral water movement during the emersion of the flat generates strong spatial heterogeneity in water–air CO2 flux.
(Estuaries and Coasts. vol. 46, n° 1559-2723, pp. 128-148, 01/01/2023)
LERPC, COAST, IFREMER, MARE, ULiège, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFREMER, LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST, Nantes Univ, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA
Storm response and multi-annual recovery of eight coastal dunes spread along the Atlantic coast of Europe
Coastal dunes are natural barriers against coastal flooding, and represent large sources of sediment to mitigate coastal erosion, besides being a natural habitat for many living beings. Yet, these complex environments are threatened by sea level rise and possibly enhanced storminess in the future. Most of the studies on coastal dune erosion and recovery from storms are either site specific or focus on a short-time scale, from months to a couple of years. Here, airborne LiDAR data collected from 2011 to 2020 at eight diverse coastal dunes, spread from NW England to SW France, were analysed to study their response, and recovery from the most energetic extreme storms wave conditions since at least 1948. Results show that the 2013/14 winter was the first or second largest erosive event (from −14 to −290 m3/m dune volume loss) from 2011 to 2020 at all sites. The magnitude of storm-driven sand volume loss was mainly controlled by dune face slope (r = 0.84). Dunes with steeper pre-storm slopes lost the largest volumes of sand. At a dune scale, the scarping height was also well correlated to the dune face slope at sites where storm response was characterized by limited alongshore variability. Dune recovery was site specific (no recovery, partial, complete, excess), with dunes that either progressively returned to their pre-storm morphology or were reshaped while recovering. Percentage of dune sand volume recovery was well correlated to the local and long-term satellite-derived shoreline change rate computed from 1984 to 2021 (r = 0.81), suggesting that dune recovery is mainly controlled by the local coastal sediment budget. The rate of dune crest elevation increase (from 4.2 to 12 cm/year) at four of the study sites from 2011 to 2020, largely exceeded sea level rise rate over the past decade (3.3 ± 0.7 mm/year). These results provide key insight into the contrasting resilience of some of the most exposed coastal dunes along the Atlantic coast that recover at different rates following the same sequence of extreme storms
(Geomorphology. vol. 435, n° 0169-555X, pp. 108735, 11/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Image analysis and benthic ecology: Proceedings to analyze in situ long‐term image series
Long time series of underwater images have become a tool widely used within the benthic ecology research community. The development of new acquisition systems with bigger storing capacities lead researchers and scientists to deploy them for longer periods resulting in large amounts of data. This paper focuses on the first steps of analyzing large numbers of underwater images, which involves assessing the amount of valid data while assuming no technical problems. The question here addressed is how many of the in situ images can reliably be really used for benthic ecology purposes. To answer this question, we propose a method to eliminate nonvalid images and use it with four different sets of time-lapsed images acquired for long periods ranging from 73 to 371 ds in a row. The results show that elimination of between 8% and 22% of the images is possible depending on the data set. The main advantage of the method is easing and accelerating automation of subsequent analysis.
(Limnology and Oceanography: Methods. vol. 21, n° 1541-5856, pp. 169-177, 11/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IO-PAN, PAN
Holocene hydroclimate variability along the Southern Patagonian margin (Chile) reconstructed from Cueva Chica speleothems
Patagonia is ideally situated to reconstruct past migrations of the southern westerly winds (SWWs) due to itssoutherly maritime location. The SWWs are an important driver of Southern Ocean upwelling and their strengthand latitudinal position changed during the Holocene, leading thus to different responses of the vegetation topast climate changes along the Chilean continental margin. A new speleothem record from Cueva Chica (51◦S) isinvestigated to reconstruct past climatic changes throughout the Holocene in conjunction with other marine andpaleoenvironmental records of the region and better constrain the regional paleoclimatic evolutions of SWWs.Samples comprising both a flowstone core and a stalagmite were radiometrically dated (U–Th & 14C) toconstruct age-depth models for the highly-resolved proxy profiles (δ13C, δ18O, chemical composition). TheCueva Chica record provides a highly-resolved isotopic and elemental curves for the last 12 ka, albeit with ahiatus from 5.8 to 4 ka BP. The multi-proxy analysis suggests three climatic regimes throughout the Holocene inSouthern Patagonia: i) an early Holocene wet period (with the exception of two dry excursions at 10.5 ka and 8.5ka BP), ii) a mid-Holocene dry period and iii), a return to generally wet conditions over the late Holocene. Theglobal drivers for these tri-phased climatic regimes are likely related to oceanic and South polar feedbacks. Theearly Holocene was the warmest period and might be attributable to changes in global ocean circulation whichinvolved a rise in air T◦ and a strength in SWW from 50◦S, and therefore higher precipitations over landmass.After 9 ka BP, an intensified deglaciation dynamic along the Antarctic Peninsula is concordant with increasingsummer insolation in the Southern hemisphere, leading to a poleward shift of the SWWs in response to globalwarming and thus to a reduction in moisture supply from the Pacific onto the Patagonian shore. After 5 ka BP, agradual SST decline is consistent with an equatorward shift of the SWWs in response to a cooling Southernhemisphere. The SWW storm tracks extended to lower latitudes, inducing a return to wetter conditions withhighly variable moisture patterns along the Patagonian landmass. Clumped isotope (Δ 47) analyses at lowerresolution reflect the degree of kinetic isotope fractionation at the time of carbonate deposition, especially duringthe dry interval around 8.5–5.5 ka BP. Reduced kinetic isotope fractionation is observed since at least 2.6 ka BP,a period marked by (slightly) wetter conditions.
(Global and Planetary Change. vol. 222, n° 0921-8181, pp. 104050, 11/04/2026)
IDEES, UNICAEN, NU, ULH, NU, UNIROUEN, NU, CNRS, IRIHS, UNIROUEN, NU, VUB, EDYTEM, USMB [Université de Savoie] [Université de Chambéry], CNRS, Fédération OSUG, VUB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MPIC, GFZ, UBA, UMAG
Morphodynamics of wave-dominated beaches
Abstract Wave-dominated sandy beaches are highly valued by societies and are amongst the world’s most energetic and dynamic environments. On wave-dominated beaches with unlimited sand supply and limited influence of tide and geology, beach change has long been conceptualised in the morphodynamic framework of Wright and Short (1984). Such framework describes the occurrence of beach types based on wave conditions and sediment characteristics across the complete reflective–dissipative spectrum. Building on theoretical work, field/laboratory measurements and monitoring programmes, the physical mechanisms underpinning this morphodynamic framework have been progressively unravelled. Cross-shore morphological changes are primarily controlled by equilibrium and beach memory principles with below (above) average wave conditions driving down-state (up-state) transitions associated with onshore (offshore) sediment transport. Such cross-shore behaviour mostly reflects the imbalance between the onshore-directed sediment transport driven by wave nonlinearities and the offshore-directed sediment transport driven by the undertow. Self-organised morphological instabilities resulting from different positive feedback mechanisms are primarily responsible for alongshore morphological variability and the generation of rhythmic morphological features, such as crescentic bars, rip channels and beach cusps. Critically, wave climate and changes in wave regimes are key in driving the coupled cross-shore and longshore behaviour that ultimately explains modal beach state and frequency-response characteristics of beach morphological time series.
(Cambridge Prisms: Coastal Futures. vol. 1, pp. e1, 11/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Settling dynamics of cohesive sediments in a highly turbid tidal river
An optical settling column was used in the Garonne Tidal River to estimate the settling velocity of suspended matter in surface waters over a period characterized by contrasting hydrological conditions. A time and space variability of settling velocity was observed during this study. The settling velocities of surface suspended matter ranged from 0.018 to 0.268 mm.s −1 , and the median diameter of dispersed particles varied from 4.74 to 14.38 µm. The data revealed the physical processes influencing the sediment settling dynamics throughout different time scales in a highly turbid tidal river. On tidal and fortnightly time scales, resuspension, deposition and advection mechanisms were the major drivers of the settling velocity variability, while it is likely that the estuarine turbidity maxima (ETM) was responsible for seasonal variations. The findings of this work suggest that in tidal rivers, salinity is too low to promote flocculation, whereas ETM can play a key role in enhancing this process. The stronger variability in settling velocity occurs on a tidal timescale, with median values up to four times higher at the end of the ebb tide than at high water. These variations cannot be correlated to salinity or sediment concentration. On a seasonal timescale, flocculation appears to be strongly correlated with the presence of the ETM and associated fluid mud layer. A simple correlation based on tidal variations seems to be a better predictor than the relationships based on the sediment concentration.
(Marine Geology. vol. 457, n° 0025-3227, pp. 106995, 11/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IGE, IRD, INSU - CNRS, CNRS, INRAE, Fédération OSUG, UGA, Grenoble INP, UGA