Sylvain Pichat

• PhD Habil. (HDR)
• Professor (Associate) at École Normale Supérieure de Lyon

Plain Language Summary Mineral dust in the atmosphere is mostly sourced from arid regions like the Sahara desert. The amount and geographical spread of this dust in the atmosphere is sensitive to environmental conditions such as drought. Paleoclimate records show that rapid cooling events centered on the North Atlantic during the last ice‐age also...

There is compelling evidence that millennial climate variability of the last glacial period was associated with significant changes in the Atlantic Meridional Overturning Circulation (AMOC). Several North Atlantic sedimentary Pa/Th records indicate a consistent and large Pa/Th increase across millennial-scale events, which has been interpreted as c...

Understanding the ocean circulation changes associated with abrupt climate events is key to better assessing climate variability and understanding its different natural modes. Sedimentary Pa/Th, benthic δ13C and Δ14C are common proxies used to reconstruct past circulation flow rate and ventilation. To overcome the limitations of each proxy taken se...

Radiocarbon ( ¹⁴ C) can be used to build absolute chronologies and reconstruct ocean ventilation over the last 40 ka. Sample size requirements have restricted ¹⁴ C measurements in marine cores with low foraminifer content, impeding ¹⁴ C-based studies focused on abrupt climate events. Recent developments have demonstrated that small-sized foraminife...

Th normalization is a valuable paleoceanographic tool for reconstructing high‐resolution sediment fluxes during the late Pleistocene (last ~500,000 years). As its application has expanded to ever more diverse marine environments, the nuances of ²³⁰Th systematics, with regard to particle type, particle size, lateral advective/diffusive redistributio...

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 r...

Understanding the ocean circulation changes associated with last glacial abrupt climate events is key to better assess climate variability and understand its different natural modes. Sedimentary Pa / Th, benthic δ¹³C and Δ¹⁴C are common proxies used to reconstruct past circulation flow rate and ventilation. To overcome the limitations of each proxy...

Background: Recreational scuba diving has been authorized for type 1 diabetics over 18 years old - the age of majority in France - since 2004, but it remained forbidden for younger diabetics by the French underwater federation (FFESSM). Here, we present a study to evaluate: - the conditions under which diving could be authorized for 14- to 18 year...

Thanks to its optimal location on the northern Brazilian margin, core MD09-3257 records both ocean circulation and atmospheric changes. The latter occur locally in the form of increased rainfall on the adjacent continent during the cold intervals recorded in Greenland ice and northern North Atlantic sediment cores (i.e., Greenland stadials). These...

Excess 231Pa and 230Th (231Paxs and 230Thxs) can be used to reconstruct past oceanic sedimentation (230Th-normalized flux) and circulation changes ((231Pa/230Th)xs,0, hereafter Pa/Th). These quantities are determined by computing the detrital and authigenic contributions from bulk sediment measurement. The method relies on the use of a chosen const...

Thanks to its optimal location on the North Brazilian margin, core MD09-3257 records both ocean circulation and atmospheric changes. The latter occur locally in the form of increased rainfall on the adjacent continent during the cold intervals recorded in Greenland ice and northern North Atlantic sediment cores (i.e. Greenland stadials). These rain...

Copper isotopic composition is altered in cancerous compared to healthy tissues. However, the rationale for this difference is yet unknown. As a model of Cu isotopic fractionation, we monitored Cu uptake in Saccharomyces cerevisiae, whose Cu import is similar to human. Wild type cells are enriched in 63Cu relative to 65Cu. Likewise, 63Cu isotope en...

The supplementary information includes: Table S1. Calculated average relative Cu concentrations and Cu isotopic compositions Table S2. Isotopic composition measurement of the same S. cerevisiae sample aliquot during four runs over the time course of 3 months Fig. S1. Evolution of Cu concentrations at a given time over Cu initial concentration and i...

We reconstruct the geometry and strength of the Atlantic meridional overturning circulation during the Heinrich stadial 2 and three Greenland interstadials of the 20-50 ka period based on the comparison of new and published sedimentary ²³¹Pa/²³⁰Th data with simulated sedimentary ²³¹Pa/²³⁰Th. We show that the deep Atlantic circulation during these i...

Hepatocellular carcinoma (HCC) is the most frequent type of primary liver cancer, with increasing incidence worldwide. The unrestrained proliferation of tumour cells leads to tumour hypoxia which in turn promotes cancer aggressiveness. While changes in the concentration of copper (Cu) have long been observed upon cancerization, we have recently rep...

We reconstruct the geometry and strength of the Atlantic Meridional Overturning Circulation during Heinrich Stadial 2 and three Greenland interstadials of the 20–50 ka period based on the comparison of new and published sedimentary 231Pa/230Th data with simulated sedimentary 231Pa/230Th. We show that the deep Atlantic circulation during these inter...

We reconstruct the geometry and strength of the Atlantic Meridional Overturning Circulation during Heinrich Stadial 2 and three Greenland interstadials of the 20-50 ka period based on the comparison of new and published sedimentary 231Pa/230Th data with simulated sedimentary 231Pa/230Th. We show that the deep Atlantic circulation during these inter...

During the last glacial period, Greenland's climate shifted between cold (stadial) and warm (interstadial) phases that were accompanied by ocean circulation changes characterized by reduced Atlantic Meridional Overturning Circulation (AMOC) during stadials. Here, we present new data from the western tropical Atlantic demonstrating that AMOC slowdow...

In this report, we provide new results for the evolution of blood glucose for type 1 diabetic recreational scuba divers breathing Nitrox 32. In addition, during this study, continuous glucose monitoring was performed on 4 diabetics. We conclude that the use of Nitrox 32 has no influence on the variations of blood glucose compared to breathing compr...

The influence of atmospheric dust on climate and biogeochemical cycles in the oceans is well understood but poorly quantified. Glacial atmospheric dust loads were generally greater than those during the Holocene, as shown, for example, by the covariation of dust fluxes in the Equatorial Pacific and Antarctic ice cores. Nevertheless, it remains uncl...

We investigate the time scales of magma genesis, melt evolution, crystal growth rates and magma degassing in the Erebus volcano magmatic system using measurements of U-238-Th-230-Ra-226-Pb-210-Po-210, Th-232-Ra-228-Th-228 and U-235-Pa-231-Ac-227. These are the first measurements of Pa-231-Ac-227 in volcanic samples and represent the first set of da...

The strength and geometry of the Atlantic meridional overturning circulation is tightly coupled to climate on glacial-interglacial and millennial timescales, but has proved difficult to reconstruct, particularly for the Last Glacial Maximum. Today, the return flow from the northern North Atlantic to lower latitudes associated with the Atlantic meri...

The δ66Zn (permil deviation of the 66Zn/64Zn ratio from a terrestrial standard) values for a suite of 20 non-Antarctic HED (howardite–eucrite–diogenite) meteorites and one mesosiderite, and for eight Antarctic eucrites and diogenites, were measured in order to determine the role of volatization in the formation of their presumed parent body, the as...

Infiltration basins are stormwater management techniques that are widely used. The settling of stormwater particles leads to a contaminated sediment layer. Wild plants can colonize these basins. They can play a role on the fate of heavy metals either directly by uptake or indirectly by modifying the forms of the metal in the sediment. Plant interac...

The strength and geometry of the Atlantic meridional overturning circulation is tightly coupled to climate on glacial-interglacial and millennial timescales, but has proved difficult to reconstruct, particularly for the Last Glacial Maximum. Today, the return flow from the northern North Atlantic to lower latitudes associated with the Atlantic meri...

We have investigated the uptake and translocation of three essential micronutrients (Fe, Zn and Cu) in four plant species using both concentrations and isotopic compositions. The goals were (1) to document the evolution of isotopic compositions in the soil and the shoots over a year, (2) to test the effect of senescence on the translocation of the...

Organo-mineral associations form one of the most important reservoirs of organic matter in soil [e.g., 1]. They play an important role in major environmental processes such as atmospheric-CO2 control and soil degradation via erosion. They are also the most fragile soil constituents and react rapidly in response to changes in temperature and water c...

Zn isotope fractionation may provide new insights into Zn uptake, transport and storage mechanisms in plants. It was investigated here in the Zn hyperaccumulator Arabidopsis halleri and the nonaccumulator A. petraea. Plant growth on hydroponic solution allowed us to measure the isotope fractionation between source Zn (with Zn(2+) as dominant form),...

The Atlantic Meridional Overturning Circulation (AMOC) is a key feature of the climate system. However, its role during climate change is still poorly constrained particularly during an Interglacial to Glacial climate transition and the associated global cooling. We present here the first reconstruction of the evolution of the vertical structure of...

Knowledge of the copper cycle in the plant–soil–water system is needed in order to better constrain proper plant micronutrient nutrition, control pollution, and determine sustainable soil management practices. Here, we report the Cu isotopic compositions of different components (seeds, germinated seeds, leaves, and stems) of the dicot, lentil (Lens...

The Atlantic Meridional Overturning Circulation (AMOC) is a key feature of the climate system. However, its role during climate change is still poorly constrained particularly during an Interglacial to Glacial climate transition and the associated global cooling. We present here the first reconstruction of the evolution of the vertical structure of...

Soil preservation for the future is one of the major objectives of the present-day research. Variations of the isotopic signatures of major elements recorded in soils can bring information about the nature and behaviour of major soil constituents in response to climatic changes and human-induced pressures. We have analysed variations of the Fe isot...

Our study gives new constraints on the response of Atlantic Meridional Overturning Circulation (AMOC) export to various forcings during the Last Glacial Inception. The decay corrected excess sedimentary (231Pa/230Th) activity ratio (hereafter referred to as (Pa/Th)) has been measured over that period in two deep cores from the Western (SU90-11, 44°...

We have analyzed by MC-ICP-MS the Zn isotopic composition of different components (seeds, leaves, and rhizome, stem and leaves) of lentils (Lens culinaris) and bamboos (Phyllostachys aurea), respectively. Zn isotopes are systematically fractionated between seeds and leaves of lentil and between stem and leaves of bamboos. Leaves are enriched in lig...

In this contribution we investigate the timescales of melt evolution and crystal growth in the Mt Erebus magmatic system using measurements of 238U-230Th-226Ra-210Pb-210Po and 232Th-228Ra-228Th. Our sample suite consists of 22 historic bombs, ranging from 1972-2005; and 5 anorthoclase megacrysts separated from historic bombs for the years 1984, 198...

We report new Nd, Hf, Sr, and high-precision Pb isotopic data for 44 lava and tephra samples from Erebus volcano. The samples cover the entire compositional range from basanite to phonolite and trachyte, and represent all three phases of the volcanic evolution from 1.3 Ma to the present. Isotopic analyses of 7 samples from Mt. Morning and the Dry V...

Changes in the orgC/CaCO3 ratio in particles sinking from the surface to the deep ocean have the potential to alter the atmospheric pCO2 over the span of a glacial/interglacial cycle. Recent paleoceanographic and modern observational studies suggest that silica is a key factor in the global carbon biogeochemical cycle that can influence the flux ra...

The (231Pa/230Th)xs,0 records obtained from two cores from the western (MD97-2138; 1°25'S, 146°24'E, 1900 m) and eastern (Ocean Drilling Program Leg 138 Site 849, 0°11.59'N, 110°31.18'W, 3851 m) equatorial Pacific display similar variability over the last 85,000 years, i.e., from isotopic stages 1 to 5a, with systematically higher values during the...

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 19 (2004): PA2018, doi:10.1029/2003PA000986. The eastern equatorial Pacific (EEP) is an important center of biological producti...

The eastern equatorial Pacific (EEP) is an important center of biological productivity, generating significant organic carbon and calcite fluxes to the deep ocean. We reconstructed paleocalcite flux for the past 30,000 years in four cores collected beneath the equatorial upwelling and the South Equatorial Current (SEC) by measuring ex230Th-normaliz...

The (231Pa/230Th)xs,0 records obtained from two cores from the western (MD97-2138; 1°25'S, 146°24'E, 1900 m) and eastern (ODP Leg 138 Site 849, 0°11.59'N, 110°31.18'W, 3851 m) equatorial Pacific display similar variability over the last 85000 years, i.e. from isotopic stages 1 to 5a, with systematically higher values during the Holocene, isotopic s...

The Eastern Equatorial Pacific (EEP) plays a large role in global ocean biological productivity and the exchange of carbon dioxide between the oceans and atmosphere. Because of this, much effort has been directed to reconstructing productivity and biogenic fluxes on the glacial/interglacial timescale in this region. These reconstructions are based...

The carbonate fraction of sediment core ODP 849, leg 138, located in the eastern equatorial Pacific, mostly consisting of coccoliths, was separated and analyzed for its Zn isotopic composition. The overall variation in Zn isotopic composition, as determined by multiple-collector, magnetic-sector, inductively coupled plasma mass spectrometry, was fo...

The carbonate fraction of sediment core ODP 849, leg 138, located in the eastern equatorial Pacific, mostly consisting of coccoliths, was separated and analyzed for its Zn isotopic composition. The overall variation in Zn isotopic composition, as determined by multiple-collector, magnetic-sector, inductively coupled plasma mass spectrometry, was fo...

Zinc participates in multiple biological processes, notably as cofactor in enzymatic photosynthetic reactions. It has been argued that fractionation between light and heavy isotopes of Zn in sinking particles is stronger after biological blooms (Maréchal et al., 2000). Considering that calcareous nannofossils, principally coccolithophoridae, deposi...

Difficulties in determining the 230Th and 231Pa concentration of seawater have hindered rapid progress in the application of these unique natural tracers of particle scavenging and ocean circulation. In response, we have developed an ICP/MS analytical procedure combining a degree of sensitivity, precision and sample throughput that can facilitate t...