A model of the annual cycle of temperature in the north-west European shelf seas with stochastic wind forcing

The climatic temperature cycle of the north-west European shelf seas has been simulated by a grid of one-dimensional mixed-layer models. The computational scheme parameterized the vertical turbulent fluxes using the Mellor and Yamada (1974) level 2 turbulence closure scheme, and included meteorological fluxes at the surface and tidal stirring at the sea-bed. The meteorological forcing was supplied by harmonic functions of a 1-year period, the amplitudes and phases of which varied spatially over the grid. The wind forcing included a stochastic component to generate variability at the synoptic time-scale, high-frequency variability being required for the generation of inertial motions and the associated vertical mixing. The model results were compared with a CTD/XBT database which showed that the main features of the annual temperature cycle, including the level of stratification and the positions of frontal boundaries, were realistically simulated. The largest errors occurred in near-coastal regions influenced by freshwater inputs. Freshwater inflows are an additional heat flux that is neglected by the model and they contribute to vertical stratification and thus inhibit the vertical transfer of heat. It is likely that a fully three-dimensional model, which includes salinity, will be required for accurate temperature simulation in such regions.