Variability in the Northern North Atlantic and Arctic Oceans Across the Last Two Millennia: A Review
The climate of the last two millennia was characterized by decadal to multicentennial variations, which were recorded in terrestrial records and had important societal impacts. The cause of these climatic events is still under debate, but changes in the North Atlantic circulation have often been proposed to play an important role. In this review we compile available high-resolution paleoceanographic data sets from the northern North Atlantic and Nordic Seas. The records are grouped into regions related to modern ocean conditions, and their variability is discussed. We additionally discuss our current knowledge from modeling studies, with a specific focus on the dynamical changes that are not well inferred from the proxy records. An illustration is provided through the analysis of two climate model ensembles and an individual simulation of the last millennium. This review thereby provides an up-to-date paleoperspective on the North Atlantic multidecadal to multicentennial ocean variability across the last two millennia.
(Paleoceanography and Paleoclimatology. vol. 34, n° 2572-4525, pp. 1399-1436, 01/08/2019)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Field data-based evaluation of methods for recovering surface wave elevation from pressure measurements
(Coastal Engineering. vol. 150, n° 0378-3839, pp. 147-159, 01/08/2019)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IMB, UB, Bordeaux INP, CNRS
Climate variability of the last 2700 years in the Southern Adriatic Sea: Coccolithophore evidences
New information on palaeoenvironmental conditions over the past ~2700 years in the Central Mediterranean Sea have been acquired through the high-resolution study of calcareous nannofossils preserved in the sediment core SW104-ND14Q recovered in the Southern Adriatic Sea (SAS) at 1013-m water depth. The surface water properties at this open SAS site are sensitive to atmospheric forcing (acting both at local and regional scale) and the North Ionian Sea driven inflowing waters. Our data show a relationship between reworked coccolith abundances, flood frequency across the Southern Alps and the North Atlantic Oscillation (NAO) confirming their value as indicator of runoff/precipitation. Changes in the abundance of the opportunistic (r-strategist) species Emiliania huxleyi and deep dweller taxa Florisphaera profunda were used to reconstruct the upper water column stratification and associated changes in coccolithophorid productivity. The negative correlation between reworked coccoliths and the N-Ratio (r = −0.44; p = 6−7) suggest that fresh water induced stratification is a controlling factor of the SAS coccolithophorid production. High coccolithophorid productivity levels occurred during dry periods and/or time intervals of inflowing salty and nutrient-rich Levantine Intermediate Waters favouring convection while lower levels took place during high freshwater discharge, mainly during the ‘Little Ice Age’ and two centennial scale intervals of weakest NAO around 200 BCE and 500 CE.
(The Holocene. vol. 30, n° 0959-6836, pp. 53-64, 31/07/2019)
INGV, ISMAR-CNR, ISMAR, CNR, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, PSL, UVSQ, CEA, INSU - CNRS, X, IP Paris, CNES, SU, CNRS, UPCité, LOCEAN-VOG, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, ISMAR, CNR, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Improving North Atlantic Marine Core Chronologies Using 230Th Normalization
Producing independent and accurate chronologies for marine sediments is a prerequisite to understand the sequence of millennial‐scale events and reveal potential temporal offsets between marine and continental records, or between different marine records, possibly from different regions. The last 40 ky is a generally well‐constrained period since radiocarbon (14C) can be used as an absolute dating tool. However, in the northern North Atlantic, calendar ages cannot be directly derived from 14C ages, due to temporal and spatial variations of surface reservoir ages. Alternatively, chronologies can be derived by aligning Greenland ice‐core time series with marine surface records. Yet this approach suffers from the lack of clearly defined climatic events between 14.7 and 23.3 cal ky BP (hereafter ka), a crucial period encompassing Heinrich Stadial 1 and the onset of the last deglaciation. In this study, (i) we assess the benefits of 230Th normalization to refine the sedimentation history between surface temperature alignment tie points and (ii) revisit the chronologies of three North Atlantic marine records. Our study supports the contention that the marked increase in the Greenland Ca2+ record at 17.48 ka ± 0.21 ky (1σ) occurred withindating uncertainty of sea surface temperature cooling in the North Atlantic at the onset of Heinrich Stadial 1. This sharp feature might be useful for future chronostratigraphic alignments to remedy the lack of chronological constraint between 14.7 and 23.3 ka for North Atlantic marine records that are subject to large changes in 14C surface reservoir age.
(Paleoceanography and Paleoclimatology. vol. 34, n° 2572-4525, pp. 1057-1073, 30/07/2019)
KU Leuven, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LGL-TPE, ENS de Lyon, UCBL, INSU - CNRS, UJM, UJM EPE, CNRS, ETHZ, ETH Zürich, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Holocene coastal changes and human adaptation at the mouth of the Gironde estuary, France (SW France)
The North Medoc Peninsula is bordered by the Atlantic Ocean to the west and the Gironde estuary to the east. The coast is formed by sandy beaches, dune barriers, estuarine marshes and intertidal mudflats. This sea-land interface experienced significant coastal changes during the Holocene. During the last three decades, intense winter storms have unearthed vestigial sedimentary deposits containing numerous archaeological remains on the Amélie beach, located on the coastal side of the Gironde estuary. While threatening those nature/culture dialectic archives, this erosional context paradoxically provides an easy access for paleoenvironment analysis. The interdisciplinary project LITAQ aimed to reconstruct the Holocene and Pleistocene environments and related human settlements in this geographical area. Now ended, this program has initiated a long-lasting collaboration between archaeologists and natural scientists through survey campaigns at the Amélie. Combination of topography, stratigraphy, and radiocarbon/relative dating of the beach and associated dune barrier sediments led to chronostratigraphic reconstructions. Thanks to sedimentological analysis, micropaleontology and geochemistry, depositional environment identification was achieved. In addition, several relative sea levels were produced, following the “sea-level index points” method. The nearly complete Holocene sequence of the Amélie was recognized, infilling the paleochannel of Soulac, a tidal inlet of the Gironde estuary, allowing paleogeographic restitutions of this coastal area. Concomitant with a sea level rise slowdown, the tidal channel infilled with marine and estuarine facies around 5000 BC. Protected by coastal dune barriers, two coastal marsh generations were recorded, between ca. 3000 BC to ca. 1500 BC and between ca. 800 BC to AD 300. Around ca. 1500 and ca. 1000 BC, an episode of marine erosion brought coastal dune ridge breach and enhanced wave penetration inside saltmarshes. From AD 300 to 700, the estuarine marsh was gradually buried by coastal dunes. Systematic spatial and stratigraphic analysis of archaeological remains generated correlations between human settlement and supporting environments. From early Neolithic to Antiquity, our research has allowed a better understanding of the human adaptation to environmental changes through time. Additional cores were performed inside the dune ridge and in the eastern marshes, located at the estuarine side of the channel. Coupled with a database of ancient drillings, this data allowed Soulac channel sequencing. The chronostratigraphic framework clarified the environments succession/expansion and erosion/aggradation phases rhythmicity controlled by interplay between marine, aeolian and fluvial processes with variable intensity within the channel. To better specify climate forcing, regional and interregional analogies were made, using indexes such as CSP, coarse grained sedimentation pulses or aeolian activity/stability phases. Moreover, the existence of high resolution marine cores collected during the program HAMOC in the Bay of Biscay, offshore of the Medoc littoral, gave the opportunity to directly correlate climate/marine changes and coastal responses.
(25/07/2019)
UBM, CNRS, LETG - Brest, LETG, UNICAEN, NU, UA, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN, GPR Human Past, PACEA, UB, CNRS, UBM, CNRS, UB, UBM, CNRS, PRODIG, UP1, IRD, EPHE, PSL, UP4, UPD7, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Polarization of Electron Density Databases of Transferable Multipolar Atoms
Polarizability is a key molecular property involved in either macroscopic (i.e., dielectric constant) and microscopic properties (i.e., interaction energies). In rigid molecules, this property only depends on the ability of the electron density (ED) to acquire electrostatic moments in response to applied electric fields. Databases of transferable electron density fragments are a cheap and efficient way to access molecular EDs. This approach is rooted in the relative conservation of the atomic ED between different molecules, termed transferability principle. The present work discusses the application of this transferability principle to the polarizability, an electron density-derived property, partitioned in atomic contributions using the Quantum Theory of Atoms In Molecules topology. The energetic consequences of accounting for in situ deformation (polarization) of database multipolar atoms are investigated in detail by using a high-quality quantum chemical benchmark.
(Journal of Physical Chemistry A. vol. 123, n° 1089-5639, pp. 7156-7170, 24/07/2019)
CRM2, UL, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Environmental changes and cultural adaptations of human populations during the Middle-to-Upper Palaeolithic transition in southwestern France between 44.000 and 35.000 BP
One of the joint issues in archaeology and paleoenvironment is the impact of climate changes on human populations and their means of adaptation. Determining the impact of climatic changes on past human populations is difficult and needs to identify possible synchronicities between a climatic event and a cultural transition. However, the identification of a concomitance is undermined by the uncertainties inherent in the chronologies of archaeological sites (dating methods) and by the resolution of environmental data. Our study focuses on improving the temporal resolution of these environmental data for southwestern France, a region that has provided abundant studies on cultural traditions since the Middle Palaeolithic. Pollen grains and spores preserved in marine sediments are good tracers of environmental changes and our study was carried out using a deep-sea core collected in the Bay of Biscay. This analysis made it possible to study at very high-resolution (100-300 years), the environmental changes in southwestern France between 44,000 and 35,000 years before the present. We then compare our results with the chronology of cultural transitions in the southwestern France, allowing us to better understand whether climate changes may have been concomitants with the development of these cultural transitions. Our very high-resolution pollen study and other climate tracers preserved in the same samples allowed us to detect several climate phases and associate them with the main climate events in the North Atlantic Ocean and Greenland, i.e. Dansgaard-Oeschger cycles and Heinrich events. In addition, we were able to observe three phases during the Heinrich 4 stadial, which were identified in very high-resolution studies of Greenland ice cores, but also in deep-sea cores from the Iberian margin.
(09/07/2019)
IRAMAT-CRP2A, IRAMAT, UTBM, UO, UBM, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EPHE, PSL, PACEA, UB, CNRS
Filtering Performances of 20 Protective Fabrics against Solid Aerosols
(Journal of Occupational and Environmental Hygiene, n° 1545-9624, 08/07/2019)
IRSST, ÉTS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Global analysis reveals climatic controls on the oxygen isotope composition of cave drip water
The oxygen isotope composition of speleothems is a widely used proxy for past climate change. Robust use of this proxy depends on understanding the relationship between precipitation and cave drip water δ 18 O. Here, we present the first global analysis, based on data from 163 drip sites, from 39 caves on five continents, showing that drip water δ 18 O is most similar to the amount-weighted precipitation δ 18 O where mean annual temperature (MAT) is < 10°C. By contrast, for seasonal climates with MAT > 10°C and < 16°C, drip water δ 18 O records the recharge-weighted δ 18 O. This implies that the δ 18 O of speleothems (formed in near isotopic equilibrium) are most likely to directly reflect meteoric precipitation in cool climates only. In warmer and drier environments, speleothems will have a seasonal bias toward the precipitation δ 18 O of recharge periods and, in some cases, the extent of evaporative fractionation of stored karst water.
(Nature Communications. vol. 10, n° 2041-1723, 05/07/2019)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
High-resolution bathymetry of the Alderney Race and its geological and sedimentological description (Raz Blanchard, northwest France)
We present a high-resolution 1:15,000 bathymetric map (Main map) of Alderney Race located offshore of northwestern France, with the strongest currents in Europe. We use this map, underwater video transects and Shipek grabs to improve geological maps previously published. We distinguished Proterozoic crystalline rocks, Paleozoic and Cretaceous sedimentary rocks on the present-day sea floor. Some structures as faults and folds are also mapped. We identified a Quaternary cover made of pebbles, boulders and blocks interpreted as corestones resulting in differential erosion and alteration of the substratum. This cover is commonly encrusted by fixed fauna, such as bryozoans and barnacles. Finally, we describe the present-day mobile sediment cover characterized by sand patches and pebble dune fields (up to 10 m in height). Our videos show the presence of mobile fine-grained sediment patches under the resolution of our map lying between the cobble and pebble cover. We summarize our interpretations on a non-exhaustive geological-sedimentary map
(Journal of Maps. vol. 15, n° 1744-5647, pp. 708-718, 03/07/2019)
LUSAC, UNICAEN, NU, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSN/PSE-ENV/SRTE/LRC, IRSN/PSE-ENV/SRTE, IRSN