Next generation ocean prediction systems

Oceans 2025 Theme 9

Numerical models are a vital tool for developing our understanding of the Earth system and how it responds to natural and anthropogenic change. Such models must be able to efficiently represent the marine environment from the global ocean to shelf seas and estuaries, linking hydrodynamics and ecosystem processes with the accuracy to provide reliable short and long term predictions. Theme 9 will deliver the state-of-the-art models needed for the next decade of UK marine science.

The work at POL for theme 9 focuses on the development, integration and analysis of shelf sea modelling systems. We are primarily involved in the physics (hydrodynamics, waves and turbulence) but also working with coupled ecosystem and sediment models.

POL has been developing numerical models of shelf-seas for over three decades. Early work focused on the development of 2D models for storm surge predication (Flather and Davies, 1977) and simple models of the dynamics of shelf sea fronts (James, 1986). This baroclinic B-grid model (POL3DB) has been developed into a fully three-dimensional s- coordinate model, which can utilise realistic forcing from atmospheric and deep ocean models. This forms the basis for the POLCOMS modelling system: the primary shelf sea model for operational and research use in the UK today.

Despite their small size shelf seas are a disproportionately important component of the marine environment:

• They are regions of exceptionally high biological productivity fuelled by rapid biogeochemical cycling.
• They mediate the transport and transformation of material (carbon, nutrients, pollutants, freshwater) from the land to the open ocean and hence are the region of the marine environment under most direct human impact, and of which our society has most direct experience.

The important role of models arises because:

• They provide complete description of the system (including its fluxes).
• They allow the interaction of processes from a wide range of disciplines to be investigated simulateously.
• They can make predictions.

However, numerical models are always limited by their accuracy and exploring this is a key part of modelling work.

The aims of Theme 9 at POL are:

1. To identify, quantify and reduce uncertainties in coastal-ocean modelling systems through the inter- comparison of a range of models, model data-synthesis and data assimilation techniques.
2. To develop the unstructured and structured grid shelf sea modelling capability available to ourselves and the stakeholders.
3. To conduct and validate key model experiments in conjunction with other Themes.

While we work with a wide range of models we focus our effort in model development on:

• POLCOMS. A structured grid multi-disciplinary model of the hydrodynamics-ecosystem-sediment system.
• ICOM an unstructured finite element 3D adaptive model.
• NEMO a structured grid deep ocean model.

Residual surface currents from the ~1.8km High-Resolution Continental Shelf application of POLCOMS. Only ever 8th grid cell is shown

Useful links

The National Centre for Ocean Forecasting (NCOF)
Global Coastal-Ocean Modelling System (GCOMS)
MERSEA INTEGRATED PROJECT
Centre for observation of Air-Sea Interactions & fluXes (CASIX)
Surface Ocean - Lower Atmosphere Study