Missions

In the context of climate change, there is considerable interest in quantifying the size and stability of natural sinks and understanding their operation. Currently this information is supplied via the Global Carbon Budget (GCB, Friedlingstein et al., 2022), which uses a set of activities known as the ocean carbon value chain to produce an annual estimate of global ocean CO2 uptake to the Conference of the Parties (COP) each year. The analysis is based on combined sea surface observations of CO2 partial pressure observations and models estimate. Unfortunately, the model and data-based estimates of ocean C uptake differ from each other by around 30% with the size of this discrepancy currently being approximately equal to the CO2 emissions of the 27 countries in the EU. Analyses suggest that it may be largely due to under sampling of the ocean, particularly the Southern Ocean (Hauck et al., 2023), implying a need for a substantial increase in observing capacity.
However, obtaining widespread estimates of surface Ocean CO2 levels in the Southern Ocean is challenging. The main goal of this postdoc position is to examine critically how the float observations from the OneArgo international programme can contribute to strengthen our understanding of the Southern Ocean carbon sink.

Activités

A number of different autonomous float platforms contributing to the Core-Argo and BGC-Argo missions of the OneArgo international programmes can be used to estimate pCO2 with an accuracy that depends on available sensors. pCO2 can be computed from the relatively expensive BGC-Argo floats carrying CTD, pH, and O2 sensors, or with the significantly cheaper O2-Argo floats carrying only CTD and O2 sensors, though with lower accuracy (Sauzède et al., 2017; Bittig et al., 2018; Carter et al., 2018). The goal in this project is twofold: (i) to assess the added value in terms of assessing CO2 flux of adding to these two types of autonomous floats an acoustic wind sensor; (ii) to document what would be the optimal float network to reduce uncertainty in estimates of CO2 flux between a denser network of small O2/wind floats, or a sparser network of large O2/pH/wind floats which are five time more expensive but deliver pCO2 with better accuracy. These assessments (i-ii) will be done by subsampling existing hindcast models of the global carbon budget, and by confronting to the modelled CO2 flux, the reconstructed CO2 flux obtained with different assumptions of observation system strategy (with versus without acoustically derived wind estimates; sparse but more accurate versus dense but less accurate pCO2 sampling; e.g. Denvil-Sommer et al., 2021).

Compétences

We are seeking a highly motivated candidate with the following background:
PhD in climate science, physical oceanography, atmospheric science, or a related field.
Ideally with experience in ocean carbon analysis
Strong programming skills (e.g., Python, Fortran, R) for data analysis and simulation handling.
Knowledge of polar climate systems, oceanography, carbon cycle

Contexte de travail

The postdoctoral researcher will be based at LOCEAN-IPSL (Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques) in Paris, France. LOCEAN is a joint research unit of Sorbonne University, CNRS, IRD, and MNHN, located in the heart of Paris on the historic Jussieu campus. The laboratory is internationally recognized for its expertise in ocean dynamics, biogeochemistry, and climate studies. As part of the Institut Pierre Simon Laplace (IPSL), LOCEAN offers access to state-of-the-art computational resources and a vibrant scientific community studying Earth's climate system. The successful candidate will benefit from collaborations with experts in ocean biogeochemistry, physical oceanography, and climate modeling, as well as interactions with the international OneArgo programme partners. The position will be part of the Horizon Europe project TRICUSO (Three Research Infrastructures together: Carbon Uptake Southern Ocean), gathering world renown internation experts from 18 institutional partners within Europe. The successful candidate will benefit from this vibrant environment.