A tentative reconstruction of the last interglacial and glacial inception in Greenland based on new gas measurements in the Greenland Ice Core Project (GRIP) ice core
The disturbed stratigraphy of the ice in the lowest 10% of the Greenland GRIP ice core prevents direct access to climatic information older than 110 kyr. This is especially regretful since this period covers the previous interglacial corresponding to marine isotopic stage 5e (MIS 5e, 130-120 kyr B.P.). Here we present a tentative reconstruction of the disturbed GRIP chronology based on the succession of globally well mixed gas parameters. The GRIP d 18 O ice chronological sequence is obtained by comparing a new set of d 18 O of atmospheric O 2 and CH 4 measurements from the bottom section of the GRIP core with their counterpart in the Vostok Antarctic profiles. This comparison clearly identifies ice from the penultimate glacial maximum (MIS 6, 190-130 kyr B.P.) in the GRIP core. Further it allows rough reconstruction of the last interglacial period and of the last glacial inception in Greenland which appears to lay its Antarctic counterpart. Our data suggest that while Antarctica is already entering into a glaciation, Greenland is still experiencing a warm maximum during MIS 5e.
(Journal of Geophysical Research. vol. 108, n° 0148-0227, 21/02/2026)
LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GLACCIOS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LGGE, OSUG, UJF, Grenoble INP, INSU - CNRS, IRSTEA, USMB [Université de Savoie] [Université de Chambéry], CNRS, INSU - CNRS, CNRS, ICOS-RAMCES, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CEP, UNIBE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UCPH
Bacterial diversity of epilithic biofilm assemblages of an anthropised river section, assessed by DGGE analysis of a 16S rDNA fragment
(Aquatic Microbial Ecology. vol. 33, n° 0948-3055, pp. 217-224, 21/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Organic-rich sediments in ventilated deep-sea environments: Relationship to climate, sea level, and trophic changes
Sediments on the Namibian Margin in the SE Atlantic between water depths of ∼1000 and ∼3600 m are highly enriched in hydrocarbon-prone organic matter. Such sedimentation has occurred for more than 2 million years and is geographically distributed over hundreds of kilometers along the margin, so that the sediments of this region contain a huge concentrated stock of organic carbon. It is shown here that most of the variability in organic content is due to relative dilution by buried carbonates. This reflects both export productivity and diagenetic dissolution, not differences in either water column or bottom water anoxia and related enhanced preservation of organic matter. These observations offer a new mechanism for the formation of potential source rocks in a well-ventilated open ocean, in this case the South Atlantic. The organic richness is discussed in terms of a suite of probable controls including local wind-driven productivity (upwelling), trophic conditions, transfer efficiency, diagenetic processes, and climate-related sea level and deep circulation. The probability of past occurrences of such organic-rich facies in equivalent oceanographic settings at the edge of large oceanic basins should be carefully considered in deep offshore exploration.
(Journal of Geophysical Research. vol. 108, n° 0148-0227, pp. 3045, 21/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UBC EOAS, UBC, ISTO, INSU - CNRS, UO, CNRS, PBDS, INSU - CNRS, CNRS, IFPEN, LODYC, IRD, UPMC, CNRS, LMMNHN, MNHN, CNRS
Interpretation of the nitrogen isotopic signal variations in the Mauritanian upwelling with a 2D physical-biogeochemical model
A physical-biogeochemical model is used to simulate the evolution of the δ15N signal during the last glacial-interglacial transition in sedimentary cores offshore from the Mauritanian upwelling. The biological model is a classical nitrogen-based trophic chain model, which also computes the nitrogen isotope fractionation. The 2D physical primitive equation model simulates the coastal upwelling circulation and is applied for different sea level scenarios. The effect of the sea level rise, inducing the shelf immersion, seems to be a main factor explaining the organic nitrogen flux and isotopic signal variations along the last deglaciation. This effect is modulated by an upwelling seasonality that may have been much longer at the Last Glacial Maximum, around 10-11 months instead of 4-5 months at present. Between 15 and 5.5 kyr ago, 60% of the sedimentary δ15N variations could be explained by this local shelf immersion effect. This reconstruction also reproduces the strong isotopic fall occurring between 5.5 kyr and the present.
(Global Biogeochemical Cycles. vol. 17, n° 0886-6236, 21/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, TBL, UT3, Comue de Toulouse, CNRS
Morphodynamique d'une dune, couplage avec l'écoulement
(21/02/2026)
LEGI, UJF, Grenoble INP, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Seasonal and interannual variability of benthic foraminiferal faunas at 550 m depth in the Bay of Biscay
Live benthic foraminiferal faunas were sampled 10 times between October 1997 and April 2000 at a 550 m depth open-slope station in the Bay of Biscay. Duplicate cores for 5 samplings allow distinguishing between spatial and temporal variability of the foraminiferal faunas. Although spatial patchiness of the foraminiferal faunas is substantial, especially in the 63-150 μm fraction, the temporal variability appears to be larger. The foraminiferal patterns are compared with surface water primary production as assessed by the study of available SeaWIFS satellite images. In the study area, the primary production regime is marked by a pulselike and prolonged spring bloom and possibly a short fall bloom. Such periods of elevated chlorophyll- a concentration are followed, after a delay of about 4-6 weeks, by a strong frequency increase of the most opportunistic taxa of benthic foraminifera. Surprisingly, no change of bottom and interstitial water oxygenation and of redox conditions within the sediment is recorded. The small taxa Epistominella exigua, Reophax guttiferus, Bolivina spathulata, Cassidulina carinata and Nuttallides pusillus appear to respond first to a labile organic matter input, by a reproductive event marked by a strong patchy spatial distribution hypothetically resulting of the spatial heterogeneity of organic matter deposits. Uvigerina peregrina and Uvigerina mediterranea, the most opportunistic larger taxa, strongly dominate the >150 μm fraction during eutrophic periods (spring and fall blooms). Intermediate and deep infaunal taxa seem to depend less on fresh organic matter input, even if a small frequency increases are recorded in the >150 μm fraction during the most productive periods; Globobulimina affinis and Melonis barleeanus show reproductive events in rather shallow sediment layers in the more oligotrophic periods of the year. A conceptual model explains the increasing delay in the response to important phytoplankton bloom periods for the successive benthic ecosystem compartments.
(Deep Sea Research Part I: Oceanographic Research Papers. vol. 50, n° 0967-0637, pp. 457-494, 21/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Annual dissolved fluxes from Central Nepal rivers: budget of chemical erosion in the Himalayas
Annual dissolved element fluxes of Himalayan rivers from Central Nepal are calculated using published river discharge and a new set chemical data of rivers including monsoon sampling. These are used to study the control on chemical erosion of carbonate and silicate over the whole basin. Chemical erosion of carbonate is mainly controlled by the river runoff but it can be limited by the availability of carbonate in limestone free basin. Chemical erosion of silicate is well correlated to the runoff. However differences between High Himalayan and Lesser Himalayan basins suggest that physical erosion may also play and important control on silicate weathering.
(Comptes Rendus. Géoscience. vol. 335, n° 1631-0713, pp. 1131-1140, 21/02/2026)
CRPG, INSU - CNRS, UL, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CGS, INSU - CNRS, CNRS
Deep organic sedimentation along the atlantic south eastern margin as a paleoclimatic indicator for last glacial-interglacial studies.
The Atlantic South-eastern margin is influenced by the presence of broad upwelling cells associated with the Benguela Current System. Sedimentary records of cores taken along 2500 km from North to South show extraordinarily high organic carbon contents for this deep and oxygenated sedimentation environment. Thus this margin is different from classically known models of organic matter preservation by the bottom water anoxia.
(pp. Vol.5, 09785, 21/02/2026)
MNHN, UPMC, CNRS, ISTO, INSU - CNRS, UO, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LMMNHN, MNHN, CNRS
Current map and bathymetry from p band sar images : preliminary results
Microwave remote sensing at very long wavelength is already used and validated for coastal zone regions and regions covered by ice (Antarctica) using airborne systems. For many other applications, a high potential exists and the PYLA 2001 experiment allowed the acquisition of data for fields still under preliminary tests. The experiment was carried on a Transall aircraft (French army/DGA) and used the SAR sensor RAMSES (multifrequency/multipolarization) from ONERA by P. Paillou et al. (2001). For the experiment, the acquisition was performed in P band (435 MHz). The aim was to explore potentials of the low frequency domain for sub-surface moisture detection (Pyla sand dune), biomass evaluation (Nezer forest), mapping of the ocean bathymetry and salinity (Arcachon inlet, estuary of the river Gironde), and archaeology (St Germain d'Esteuil, Dignac, Moulin du Fa). A dedicated P-band calibration site was set up in order to fully exploit the polarimetric information. This part of the study consists of analyzing SAR images from RAMSES (P band) in order to be able to take into account the effect of longer surface waves, winds and currents on the surface roughness in the Arcachon inlet. Tidal currents associated with long oceanic waves recorded at the mouth of the inlet, including the northern channel and sand banks of the ebb tidal delta. The analysis provides tools allowing the production of current maps, which are in turn compared to in-situ measurements by GPS on surface drifting buoys and to current velocity fields provided by a 2DH numerical model, MARS-2D. The evaluation of the ability of a 1D hydrodynamical model applied to SAR images in order to reproduce currents in the area presented. Multipolarization images can be used in order to separate the information associated with the ocean surface (tilt) modulation, which is different for each polarimetric image, from the hydrodynamic modulation, similar for each image. The tilt modulation is representative of a Real Aperture Radar-like (RAR) image. The data being available quite late, we just performed correlations between each set of data by using polarimetric coefficient. We obtain good answers on the information associated with the motion of the scatterers.
(. vol. 2, pp. 960-962, 21/02/2026)
TAMCIC, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFREMER
Bias in the paleoceanographic time series: Tests with a numerical model of U, C org , and Al burial
(Paleoceanography. vol. 17, n° 0883-8305, pp. 6-1-6-11, 01/09/2002)
CEREGE, IRD, INRA, AMU, CdF (institution), INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CNRS, CEREGE, IRD, AMU, CdF (institution), INSU - CNRS, CNRS, INRAE