PhD position (M/F): Oxygen-17 systematics in modern carbonates and waters

Job Description

Thesis Subject

The isotopic composition of oxygen in a carbonate mineral reflects both the temperature and the process responsible for its formation, as well as the isotopic composition of the water in which the mineral crystallized. This is why oxygen-18 in natural carbonates provides crucial information on the history and functioning of terrestrial environments, but this information often remains difficult to interpret quantitatively without additional constraints that allow the respective effects of temperature, source water, and isotopic disequilibria to be deconvolved. In this context, one possible solution is to also measure the oxygen-17 of these carbonates ("triple oxygen isotopes"), using novel analytical approaches. The aim of the thesis will be to characterize, on the one hand, the modern natural variability of oxygen-17 in seawater, river water, and glacier meltwater, and on the other hand, the fractionation laws linking the triple isotopic composition of different types of carbonates to that of their source waters. This work will focus on modern water samples and various types of (bio)carbonates with a priori known formation conditions, and will rely on instrumentation that is unique in the world (VCOF-CRDS laser spectrometry) offering excellent analytical performance.

Required skills and qualities: Collaborative work – Ability to perform excellent analytical work – Compliance with experimental safety rules – Organization, rigor, and traceability of experiments – Care and precision in sampling – Good documentation of work carried out – Ability to learn the necessary mathematical and computational tools (Python in particular) – Aptitude for synthesis (literature review, analysis results) and for sharing results both orally and in writing – Intellectual rigor and clarity of written expression – Good command of the English language.

Your Work Environment

The work will take place at the Laboratoire des Sciences du Climat et de l'Environnement (LSCE), a joint research unit (UMR 8212) of the Commissariat à l'Énergie Atomique et aux énergies alternatives (CEA), the Centre National de la Recherche Scientifique (CNRS), and the Université de Versailles Saint-Quentin en Yvelines (UVSQ), located at the CEA site of Orme des Merisiers on the Paris-Saclay University campus. It is part of the Institut Pierre-Simon Laplace (IPSL). LSCE, which brings together more than 350 researchers, PhD students, engineers, technicians, and administrative staff, studies the past, present, and future mechanisms of climate change and the evolution of the Earth's external environment, using observations and modeling exercises.

The PhD student will be welcomed into the Paleocean team, one of whose specialties is the development of new paleoclimatic tracers (carbonate isotopes, clumped isotopes "Δ47", trace elements). The thesis is funded by the ERC project TONIC (Triple Oxygen Fingerprinting of Ice Sheets), which aims to combine triple oxygen isotopes and isotopic clumping in marine biocarbonates to shed light on the history of the planet's ice sheets. This thesis work is part of existing collaborations with the Laboratoire d'Ecogéochimie des Environnements Benthiques (LECOB, UMR 8222) and the Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques (LOCEAN, UMR 7159).

Constraints and risks

No particular constraints. Risks: handling (under secure conditions) of phosphoric acid, a blowtorch, and liquid nitrogen.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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