Description of the offer

A researcher postdoc position is available at the Laboratoire d’Océanographie Physique et Spatiale (LOPS-UMR6523) at University of Western Brittany (UBO) in Brest, in the framework of the UE HORIZON Euro-Argo One project (see project description below). The starting date can be as soon as September 2025. The appointment is a full-time position, for 18 months. The postdoc will contribute to scientifically inform the design of the OneArgo array in the Arctic Ocean. The goal is to assess the Arctic Ocean Heat (OH) and Freshwater (FW) contents changes, and the sensitivity of the uncertainties on OH and FW contents to the observational sampling in the Arctic. To do so, the post-doc will use a comprehensive in situ database available in the Arctic and analyzes tools (such as optimal interpolation) to perform OHC and FW pan-Arctic and regional budgets, as well as model reanalysis and Argo floats simulations in an ocean forced model. The project is conducted in collaboration with scientists at national and international levels from the Euro-Argo One consortium ( https://www.euro-argo.eu/EU-Projects/Euro-Argo-ONE-2025-2027). At LOPS, the postdoc will work closely with Nicolas Kolodziejczyk (nicolas.kolodziejczyk@univ-brest.fr) and Camille Lique (camille.lique@ifremer.fr), and will be part of the group ‘Ocean and Climate’.Theywill benefit from the strong expertise existing at LOPS regarding in situ and satellite observations and their processing. The successful postdoc is expected to present their results in national and international conferences/workshops and publish papers in scientific peer-reviewed journals. The postdoc is also expected to contribute the Euro-Argo One project’s deliverables in the form of reports or progress meetings

Euro-Argo One project

Euro-Argo One Context

The OneArgo design (Roemmich et al., 2019) was defined following regional pilot experiments, which demonstrated the technological and operational readiness of Argo to extend its ocean observation capacity towards biogeochemistry, greater depth and new regions. European teams played a crucial role in these pilot studies and, in Europe, the implementation of OneArgo started swiftly. However, moving from pilot studies to the full implementation and maintenance of an array built, for its European share, of more than 1000 active floats, including about 250 BGC-Argo and 300 Deep-Argo floats, comes with challenges and requires an operational step change. The ambition of the Euro-Argo ONE project is to consolidate Euro-Argo ERIC and gear up to be able to implement its contribution to OneArgo. The OneArgo design was defined 5 years ago at global level. Euro-Argo ONE will refine several aspects of the design in line with European scientific and operational interests. Better knowledge of deep sensors’ accuracy, as well as new tools and datasets allowing to improve the spatial and temporal statistics of deep ocean variability, will guide the strategy for Deep-Argo sampling in European areas of interest (North Atlantic and Nordic Seas). Strategies for Argo sampling in the Arctic Ocean and in the European marginal seas will be drawn up. Among the six official variables of the BGC mission, O2 is of special interest: O2 has the highest technology readiness level and a wide range of applications for climate change monitoring (deoxygenation) and in ocean research, is critical for most

biogeochemical processes and can be used to infer nutrient concentrations and carbonate system parameters (Sauzède et al., 2016). It allows estimates of anthropogenic carbon storage and export (Asselot et al., 2024). Considering the added value of O2 data and the relatively low cost of O2 sensors compared to other BGC sensors, the project will investigate if the sampling strategy of the BGC mission is adequate for estimating accurate global O2

long-term trend and relevant biogeochemical

and physical processes, and propose an alternative sampling strategy. Argo data distribution relies on a well-structured data system defined by the international Argo Data Management Team (ADMT), which includes several Euro-Argo ERIC partners. This international data system, created for Core Argo more than 20 years ago, has been progressively adapted to cope with larger amounts of data and the Deep and BGC data. Nevertheless, it now requires a paradigm change to match the OneArgo needs. Today, only temperature and salinity data are provided with an associated uncertainty range. Procedures to qualify and correct BGC-mission data in delayed mode exist for most parameters; however, they need to be adapted to fit in with the local environment in specific regions (e.g. European marginal seas, Arctic Ocean). The quality of data provided to users will be improved via (a) the development and automation of existing procedures, (b) the development of procedures for new parameters, and (c) the provision of uncertainties for O2 data. OneArgo data FAIRness will be further enhanced, and the leads for the evolution towards a data system more reliable, scalable, efficient, secure and adaptable to new technological expansion will be investigated. The resilience of data provision will be upgraded through further developments of real-time data processing and cybersecurity assessment and risk analysis (integrity of data, piloting of floats). Developments and recommendations will be communicated up to international level. As a 4D observation of the evolutions of the ocean, high-quality OneArgo data will be a cornerstone of the future Digital Twin of the Ocean. Today, most Argo observations rely on a single sensor model and manufacturer for each parameter. This applies to temperature and salinity measurements at all depths and for biogeochemical parameters. The situation could lead to unexpected issues regarding data quality and/or disruption of supply chains, potentially jeopardising the long-term sustainability of OneArgo. The project will address this challenge by assessing the quality of measurements made by alternative sensor models of manufacturers against the quality requirements of OneArgo. Sensor diversification will ultimately increase the resilience and efficiency of Euro-Argo ERIC. In addition, the project aims to address environmental concerns created by Argo floats, which are usually lost at sea upon battery exhaustion. Euro-Argo ONE will develop a global strategy and guidelines for the recovery of floats and will work on the reconditioning of recovered floats. In doing so, the project will contribute to the operational efficiency and the environmental sustainability of OneArgo.

Euro-Argo One at LOPS

In the Framework of the Euro-Argo One Project, LOPS is committed to a task aiming at providing technical recommendation and scientific rationale to foster Argo float deployments, using Ice Detection Algorithm (ISA), in highly constrained sea ice covered region, Marginal Ice Zone and shelves seas over the Arctic basin. All the partners will work at providing specific needs for both vertical and horizontal sampling resolution, nominal regional coverage, technical float setting (including navigation parameters and ISA tuning), parking depth, EEZ framework, and regional deployment hotspots, as well as providing recommendations and tools for under ice trajectory reconstruction. For future Arctic Argo array design, partners will also survey the most recent float’s technologies development for under ice positioning and communication. Given the highly constrained Arctic environment, interaction, and complementarity with the Arctic observing system community will be needed for preparing this phase of Polar Argo mission.

Qualification requirements

  • Applicants must hold a PhD degree in physical oceanography, climate science or related field.
  • Programming skills (Python, Matlab or another scientific language), with demonstrated proficiency in data processing methods.
  • Strong written and oral communication skills in English, and the ability to work in a large team.
  • Previous experience on polar research would be an asset

We offer

  • A scientific professionally stimulating working environment
  • An attractive place to live (Brest) with many cultural and outdoor activities, especially sea oriented

How to apply

The application must include

  • A cover letter (statement of motivation, summarizing scientific work and research interest)
  • A detailed CV including a complete list of publications
  • Names and contact details of 2 references (name, relation to candidate, e-mail and telephone number)
  • Deadline for application: 30 June 2025
  • Please send your application to nicolas.Kolodziejczyk@univ-brest.fr