An operational biogeochemical model of the North-East Atlantic: Model description and skill assessment

- An operational biogeochemical model of the North-East Atlantic was developed.
- Skill assessment shows that chlorophyll and nitrate dynamics are well represented.
- Characteristic bio-physico-chemical features in the region are reproduced.
- The model is run daily and the output is freely available via a dedicated server.
- The model provides boundary conditions to local models and underpins other services.

This paper presents a high resolution operational biogeochemical model of the North-East Atlantic that encompasses part of the continental shelf and adjacent deep sea and includes all of Ireland's territorial waters. The setup of the model is described, followed by its skill assessment in reproducing chlorophyll and nitrate spatio-temporal variability. Part of the model skill assessment concerns the evaluation of its usefulness in a decision-making process and is based on the application of a binary discrimination analysis. The model is one-way nested within a 1/12° Mercator Ocean PSY2V4R2 operational model that provides physical forcing at the lateral open boundaries. Nitrate fields are also proscribed at the open boundaries; the World Ocean Atlas 2009 monthly climatologies are used in the upper 500 m and at greater depths a formula that relates nitrate concentration to temperature and latitude is applied in the model. The model represents the intra-annual variability of surface chlorophyll and nitrate concentrations at monthly time scales across key oceanographic regions reasonably well; deficiencies are identified in some regions along with possible causes. The model can reproduce important characteristic bio-physicochemical features e.g. the frontal dynamics and upwelling off southwest Ireland and the properties of different water masses in the Rockall Trough. The model is deemed suitable for operational purposes, with a high probability to make correct positive and negative decisions. Operational since 2011, the output is publicly available via a dedicated THREDDS server.