Assimilation of Ocean‐Color Plankton Functional Types to Improve Marine Ecosystem Simulations

• Published in: Journal of geophysical research. Oceans Vol. 123; no. 2; pp. 834 - 854
• Main Authors: Ciavatta, S., Brewin, R. J. W., Skákala, J., Polimene, L., de Mora, L., Artioli, Y., Allen, J. I.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-02-2018
• Subjects: Assimilation; Biogeochemistry; carbon fluxes; Chlorophyll; Chlorophylls; Community structure; Computer simulation; data assimilation; Diatoms; Dinoflagellates; ecosystem model; Ecosystem models; Ecosystems; emergent properties; Environment models; Estimation; Fluxes; Geophysics; Indicators; Kalman filters; Marine ecosystems; Ocean color; Ocean colour; Oceans; Phosphates; Phytoplankton; Picoplankton; Plankton; plankton functional types; Simulation; Statistical methods; Temperature (air-sea); Uptake
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1002/2017JC013490

We assimilated phytoplankton functional types (PFTs) derived from ocean color into a marine ecosystem model, to improve the simulation of biogeochemical indicators and emerging properties in a shelf sea. Error‐characterized chlorophyll concentrations of four PFTs (diatoms, dinoflagellates, nanoplankton, and picoplankton), as well as total chlorophyll for comparison, were assimilated into a physical‐biogeochemical model of the North East Atlantic, applying a localized Ensemble Kalman filter. The reanalysis simulations spanned the years 1998–2003. The skill of the reference and reanalysis simulations in estimating ocean color and in situ biogeochemical data were compared by using robust statistics. The reanalysis outperformed both the reference and the assimilation of total chlorophyll in estimating the ocean‐color PFTs (except nanoplankton), as well as the not‐assimilated total chlorophyll, leading the model to simulate better the plankton community structure. Crucially, the reanalysis improved the estimates of not‐assimilated in situ data of PFTs, as well as of phosphate and pCO2, impacting the simulation of the air‐sea carbon flux. However, the reanalysis increased further the model overestimation of nitrate, in spite of increases in plankton nitrate uptake. The method proposed here is easily adaptable for use with other ecosystem models that simulate PFTs, for, e.g., reanalysis of carbon fluxes in the global ocean and for operational forecasts of biogeochemical indicators in shelf‐sea ecosystems.
Key Points
Assimilation of phytoplankton functional types improved the simulation of the plankton community structure
The simulation of CO2 partial pressure was improved, impacting the estimate of the air‐sea carbon flux
Assimilation of phytoplankton functional types outperformed that of total chlorophyll