NOCS: NEMO activities in 2006

1. NOCS: NEMO activities in 2006 • Preliminary tests of a full “LOBSTER” biogechemical model within the • ORCA1 configuration. (6 extra passive tracers). • Developed “on-the-fly” interpolation of CORE forcing fields. • Installed AGRIF capabilities. Configured an ORCA1 model with 1/4o N.A. • and 1/12 degree Flemish Cap region. • Agreed common 64 level vertical grid with A.M. Treguier • (replaces 66 level option) • Obtained and tried the ORCA025 configuration. • Attempted topographic and Straits modifications to improve inter-basin exchanges • Tested Chris Harris’ (UKMO) implementation of Griffies’ skew-flux formulation of eddy induced transport. • Preparing to test ORCA1 with DRAKKAR-compatible physical parameters and options in longer tests (DFS3 forcing)

2. OCEANS 2025: Themes and selected scientific objectives Theme 9: Next Generation Ocean Prediction Systems: • How sensitive are climate models to the manner in which sea ice is coupled? • Can nested models be trusted to give accurate results? • Can an ocean model be made energetically self-consistent? • What is the most appropriate level of complexity of biogeochemical models in climate studies? Approaches and methodologies: • Develop NEMO as the core OGCM for use by the scientific community in the UK, at resolutions of 1°, ¼°and 1/12°, and with nested grids (WP 9.10). • Develop an ocean model testbed permitting objective intercomparison and validation of a range of ecosystem models, with a view to embedding the most promising in OGCMs (WP 9.11).

3. OCEANS 2025: Themes and selected scientific objectives Theme 2: Marine Biogeochemical Cycles • To determine the sensitivity to future climate change of the mechanisms sustaining total nutrient supply to the photic zone over the three major biomes of the North Atlantic. Approaches and methodologies: • Quantify the magnitude and sensitivity of nutrient fluxes associated with winter overturning and Ekman pumping. For overturning, this will be achieved using time-series stations, Argo floats and mooring data together with previous studies and basin-scale simulations (NEMO both at ¼º and with a smaller scale nested component at 1/12º in the North Atlantic).

4. OCEANS 2025: Themes and selected scientific objectives Theme 1: Climate, Ocean Circulation, and Sea Level • Model simulations of climate change in the ocean • Identifying the causes of recent climate change in the ocean • Physical-biogeochemical budgets and mixing in the Southern Ocean (DIMES) Research plan and deliverables: • 2008: Completed simulation of changes in the ocean over the period 1950 - 2006 obtained by running NEMO globally at 1/4° resolution (and with a nested 1/12° North Atlantic grid) using NCEP/NCAR (and possibly ECMWF) derived surface flux fields (WP 1.1b)

5. For comparison, a typical aeiu field using the H&L (default) scheme:

6. Aeiu field with the Visbeck scheme after 5 years integration.

7. Extra Physics in MOM4/OCCAM • Horizontal K11 term isn't truncated. This models horizontal diapycnal diffusivity in the ML • Extra tapering near the surface (the sine taper) of all terms except K11.Prevents too-strong surface-intensified GM velocities and allows smooth change from isopycnal to horizontal diffusion. • Linear variation of the GM streamfunction between the ML base and surface to spread the GM flux through the ML. Otherwise, the steep-slope tapering brings the GM streamfunction to zero somewhere just above the ML base, and hence the GM flux is concentrated at the ML base • Option to limit GM streamfunction at KGMSmax instead of tapering it to zero for slopes exceeding Smax. Allows more restratification.

8. Core strategic Modelling Infrastructure Climatological Six hourly winds Assimilation runs OCCAM • 66 vertical levels • High frequency surface • fluxes • KPP mixed layer • Isopycnic mixing • Variable bottom box • Sea ice