Quantifying the uncertainty of the Low and Mid-Trophic Levels hindcasts (MICRORYS) of Copernicus Marine Service catalogue

The Lower and Mid Trophic Levels (LMTL) component of the Spatial Ecosystem And POpulation DYnamic Model (SEAPODYM) estimates, at a global scale, the spatial distribution of biomass densities of meso-zooplankton and micronekton (functional group of organisms with size between 2 and 20 cm). This model is based on a system of advection-diffusion-reaction equations forced by ocean currents, temperature, and Net Primary Productivity (NPP). NPP acts as a biomass source throughout an energy transfer coefficient. Ocean currents control the transport of organisms, and the temperature affects their development and mortality.

Since mid-2019, this model has been used to produce the “Global Ocean low and mid trophic levels biomass content hindcast” product (also known as MICRORYS) of the Copernicus Marine Environment Monitoring Service (CMEMS) catalogue. This product of the green ocean is particularly relevant for studies of ecosystem and fisheries dynamics as micronekton is the food of numerous emblematic and fishery targeted species, respectively such as dolphins and tunas. The MICRORYS product is forced by the CMEMS Global Ocean Physics Reanalysis and the NPP computed from chlorophyll a of the CMEMS Global Ocean Colour multiyear product (satellite observations).

We will present an ensemble run based on different sets of physical and biogeochemical hindcast to quantify the uncertainty of the model with respect to forcings. We will focus this presentation on the micronekton functional group of organisms that perform the largest migrations, between lower meso-pelagic during daytime and epipelagic layers during nighttime, because of its influence on carbon export.