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)

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).

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).

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)

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

Aeiu field with the Visbeck scheme after 5 years integration.

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.

ClimatologicalSix hourly windsAssimilation runs

Core strategic Modelling Infrastructure

• 66 vertical levels• High frequency surface fluxes• KPP mixed layer• Isopycnic mixing• Variable bottom box• Sea ice