Scientific axes – The PISCES Community

1. Marine biogeochemistry at the ocean-atmosphere interface

PI : Roland Séférian (CNRM) Here, the role of marine biogeochemistry at the ocean-atmosphere interface is investigated focusing on the following scientific questions:

How do biogeochemical and ecological emissions of non-CO₂ GHG greenhouse gases (GHG) and aerosols (AER) processes interact with complex ocean physics?
How do biogeochemical and ecological processes for non-CO₂ GHG and AER emissions interact in response to external material input from the atmosphere across different regions?
What are the feedback mechanisms between ocean non-CO₂ GHG and AER emissions and climate change?

The work produced in this axis is supported by the participation in international initiatives such as the Global Carbon Budget (GCB), the Coupled Model Intercomparison Project phase 6 (CMIP6) or the Ocean Carbon Cycle Model Intercomparison Project phase 6 (OCMIP6) aside to the H2020 European project CRESCENDO, which will all contribute to the outreach of this axis by using its simulation results in various scientific intercomparison publications. Additionally, this project fits the SOLAS science plan and implementation strategy, especially within the Core themes 1 and 2 of the current SOLAS action plan. Its strong connection with the SOLAS science plan will enable this work to reach a broader community.

2. The cycles of trace elements and isotopes

PI : Laurent Bopp (PSL) and Alessandro Tagliabue (University of Liverpool) The objective here is to consolidate the existing modeling work with PISCES on TEIs (Trace Elements and Isotopes), investigate the response of some TEIs distribution to past climate variability and explore the controls of the distribution of new TEIs, such as trace metals (Zn, Co). The following scientific questions will be explored:

What are the main controls on the distribution of key trace metals (Zn, Co, Cu in addition to Fe) and how these trace metals may affect primary productivity and its changes?
What are the main controls on the distribution of some key isotopes of stable elements (¹³C, ¹⁵N, ¹⁸O of dissolved O₂) and how can these elements be used to trace back past variations of both ocean circulation and marine productivity?
What are the main controls on the distribution of key TEIs (²³⁰Th, ²³⁴Th) and how these distributions may help constraining some biogeochemical fluxes in the ocean?

The work conducted in this axis is conducted in the context of the GEOTRACES modeling activities, and as such, will be integrated in modeling intercomparison projects such as FeMIP (SCOR WG, PI: A. Tagliabue). It is also supported by on-going projects, such as ERC-BYONIC (PI: A. Tagliabue) on co-limitations by trace metals and ANR MERTOX (PI: D. Point) for its workpackage on ocean ¹³C.

3. The marine ecosystems up to the upper trophic levels

PI : Olivier Maury (MARBEC) PISCES has been coupled to the model APECOSM which represents the dynamics of three trait-based High Trophic Level (HTL) communities (epipelagic, migratory and mesopelagic) with mechanistic spatially explicit size-spectra. The coupling is mass conservative at the scale of the two models, both of which are embedded in NEMO to form the NPA (NEMO-PISCES-APECOSM) integrated model (Aumont et al., 2018). In the present project, we will undertake new developments to address the following three scientific questions:

What are the impacts of global fisheries on marine biogeochemistry and the carbon cycle?
What are the conditions for large-scale shifts from typical diatoms-mesozooplankton-fish food chains to nanophytoplankton-microzooplankton-jellyfish food chains? What would be the impacts on biogeochemistry, the biological carbon pump and the carbon cycle?
How are the dynamics of carbon and nitrogen isotopes (¹³C and ¹⁵N) simulated in PISCES transferred in HTLs? Can we use NPA with isotopes to study trophic interactions?

4. Major future developments of PISCES

PI: Laurent Mémery (IUEM)

The PISCES community is taking on incorporating new developments following a double target: to improve PISCES in adding processes that are known to be important and that can be constrained by data (validation); To explore new mechanisms that are considered important, for which validation is not straightforward, but that could be included in the next generation of PISCES (sensitivity analyses). Moreover, the new developments foreseen are directly linked to scientific questions raised by the PISCES community itself, which allows effective and targeted initiatives built on actual involved individuals.

These generic scientific questions are:

What is the impact of the microbial `biodiversity’ on the biogeochemical cycles?
What are the main processes to consider to accurately represent the C export and the attenuation of the C flux in the mesopelagic zone (mostly zooplankton behavior)?
How to take into account the fluxes between the water column and the benthic layer in order to simulate the sources/sinks of carbon and nutrients in sediments?