Here is a brief description for users of the meaning of new ocean parameters, from the NEMO model, that are now stored as output from the IFS (HRES and ENS) using "level type" = surface.

• Sea-ice thickness: The gridbox mean value. Incorporates sea ice concentration in computing the mean - i.e. the proportion of the gridbox diagnosed to be covered by sea ice.
• Mixed layer depth: Based on a standard water-density-based oceanographic convention. This depth is the first depth, going down, at which the density (sigma-theta) difference, compared to density at 10m depth, reaches 0.01 kg/m³.
• Sea-surface height: This is the difference, from the geoid, of ocean height. Neither tides nor surges are not accounted for.
• Sea water practical salinity: Salinity in the top level of the ocean model. In psu (practical salinity units; g/kg).
• Average salinity in the upper 300m: Self explanatory, in psu. A missing data indicator is used wherever the model's ocean depth is less than 300m.
• Average potential temperature in the upper 300m: Self explanatory. A missing data indicator is used wherever the model's ocean depth is less than 300m.
• Depth of 20C isotherm: The depth at which, scanning downwards from the ocean surface, the 20C isotherm is first reached (temperature ordinarily reduces with depth). If the top level ocean temperature is below 20C, the value is zero, but if 20C is never reached, the value is the modelled ocean depth.