Speaker: Yumeng Chen (Reading)
Title: Assimilating phytoplankton carbon in marine ecosystem modelling
Abstract:
The state of the marine ecosystem can be estimated by combining numerical models and satellite observations through data assimilation (DA). Satellite products representing phytoplankton chlorophyll, derived from ocean colour observations, are widely used in operational marine ecosystem prediction as a proxy for phytoplankton biomass. However, phytoplankton carbon products, although long available, are not yet widely assimilated. A new phytoplankton carbon product from the ESA-funded BICEP project has recently been derived through an alternative processing of ocean colour, providing complementary information on phytoplankton biomass to chlorophyll alone. We therefore expect that assimilating phytoplankton carbon, especially together with chlorophyll, can provide a more balanced update to the marine ecosystem state.
In this talk, I will present the development of a global ensemble DA system based on the coupled ocean–biogeochemistry model NEMO-MEDUSA and the Parallel Data Assimilation Framework (PDAF). PDAF provides a flexible and efficient infrastructure for implementing ensemble-based DA, allowing us to assimilate new biogeochemical variables and evaluate time-dependent forecast uncertainty in a global marine ecosystem model. In addition, we will introduce a newly developed diagnostic tool that is used to quantify the uncertainties in observation and forecast errors. We will demonstrate its application to the errors of the new carbon product and their correlations with errors in the chlorophyll products. The results highlight both the potential value of phytoplankton carbon assimilation and the importance of flexible ensemble DA frameworks for developing future marine ecosystem prediction systems.