Global nitrogen cycle modeling within the Earth System (M/F)
Application Deadline : 09 October 2024 23:59:00 Paris time
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General information
Offer title : Global nitrogen cycle modeling within the Earth System (M/F) (H/F)
Reference : FR636-ALERUB-053
Number of position : 1
Workplace : GIF SUR YVETTE
Date of publication : 18 September 2024
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 November 2024
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Section(s) CN : Earth System: superficial envelopes
Description of the thesis topic
Nitrogen fertilizers play an essential role in the productivity of cultivated ecosystems. This supply of nitrogen induces the accumulation of reactive nitrogen in the form of multiple compounds and the increase in nitrogen fluxes associated with the numerous reactions in which these compounds are involved. This is what Galloway et al. (2003) defined under the term of “nitrogen cascade”. Thus, nitrogen compounds (NH3, NOx, N2O), mainly emitted by the agricultural sector, are also important components for atmospheric chemistry and, directly or indirectly, for the climate. Ammonia (NH3) can react with sulfuric acid or nitric acid to form fine particles (PM2.5) which have consequences on the climate (through their radiative effects) and on health. N2O, as a greenhouse gas, has an impact on the radiative budget, and NOx, precursors of tropospheric ozone, contribute to deteriorating air quality. In return, atmospheric deposition of nitrogen in reduced (NHx) and oxidized (NOx) form enhances the productivity of terrestrial and oceanic ecosystems, by acting as fertilizer.
Several studies have recently highlighted the major disturbance of the nitrogen cycle by human activities within the different reservoirs of the Earth system (Erisman et al., 2013; Tian et al., 2020). Studies based on modeling approaches are essentially carried out at the scale of a single reservoir (atmosphere, continental surfaces, or oceans) with data from inventories or from other modeling as constraints at the boundaries of the studied system. This type of work originating from an assembly of “single-component” studies can be sources of inconsistency and does not allow studying interactively feedbacks between large reservoirs in a disturbed environment, with climate change and increased use of nitrogen fertilizers. As part of the proposed thesis, we therefore expect to take off this limitation by developing an interactive modeling of the nitrogen cycle at global scale in an Earth system model and thus open up new fields of applications.
The objective of this thesis will be to quantify nitrogen exchanges between the atmosphere, the land surface and the oceans through an integrated modeling. This work will be done for the historical period as well as for different future scenarios of socio-economic development, in particular of the agricultural sector. To do this, we will rely on the numerical modeling tool developed at IPSL (Boucher et al., 2020) and in particular on recent developments leading to an interactive modeling of ammonia emissions between the “land surface” component (ORCHIDEE model) and the “atmospheric chemistry” component (INCA model) of the IPSL Earth system model (Beaudor, 2023; Beaudor et al., 2023). The thesis will aim at extending this interactive modeling to NOx emissions and atmospheric nitrogen deposition on lands and oceans (PISCES model for the ocean). The nitrogen flows simulated by this interactive modeling for the different large reservoirs will be compared to the most recent estimates for the last decades (2000-2020). Using factorial simulations for which interactions between reservoirs will be activated/deactivated, the strength of the feedbacks between atmosphere, land and ocean, concerning the nitrogen cycle, over the historical period (since 1850) and for the near future until by 2100 will be quantified. Through the development of these modeling tools and associated simulations, the thesis work will advance our knowledge of the importance of the disturbance of the nitrogen cycle and in particular of the interactions between reservoirs.
Work Context
The selected student will be supported the supervisory team, and will also be assigned a mentor, a privileged contact for more informal discussions (general progress of the thesis, professional project, help in difficult situations, etc.). Many events are regularly organized at the LSCE (weekly seminars, monthly animations of the laboratory's themes, sessions of presentations by doctoral students, etc.) in which the student will have the opportunity to get involved. This work will be carried out at the Laboratory of Climate and Environmental Sciences (LSCE), a joint CEA-CNRS-UVSQ research unit dedicated to the measurement and modeling of climate change and biogeochemical cycles. The LSCE is also part of the Pierre-Simon Laplace Institute, which brings together several laboratories in the Ile de France region focused on environmental sciences, which are co-constructing the IPSL Earth system model in particular. The LSCE is located in Saclay, 30 km south of Paris, connected to Paris by the RER B and inter-company shuttles. Teleworking is possible in agreement with the supervisors, with a maximum of 2 days per week. This thesis work is also part of the European project "Earth system models for the future" (ESM2025, https://www.esm2025.eu/).
Additional Information
The position is allocated at Gif-Sur-Yvette
