Near-surface vertical mixing is parametrized partly by a Kraus-Turner mixed layer scheme for tracers Kraus and Turner 1967), and a K-theory scheme(Pacanowski and Philander 1981)for momentum. Below the upper layers the vertical diffusivity is an increasing function of depth only. Convective adjustment is nodified in the region of the Denmark Straits and Iceland-Scotland ridge better to represent down-slope ixing of the overflow water is allowed to find its proper level of neutral buoyancy rather than ixing vertically with surrounding water masses. The scheme is based on Roether et al (1994) Mediterranean water is partially mixed with Atlantic water across the Strait of Gibraltar as a simple representation of water mass exchange since the channel is not resolved in the model The sea ice model uses a simple thermodynamic scheme including leads and snow-cover. Ice is advected by the surface ocean current, with convergence prevented when the depth exceeds 4 m( Cattle and Crossley 1995) There is no explicit representation of iceberg calving, so a prescribed water flux is returned to the ocean at a rate calibrated to balance the net snowfall accumulation on the ice sheets, geographically distributed within regions where icebergs are found. In order to avoid a global average salinity drift, surface water fluxes are converted to surface salinity fluxes using a constant reference salinity of 35 PSU The model is initialized directly from the Levitus et al (1994, 1995)observed ocean state at rest, with a suitable atmospheric and sea ice state. The atmosphere and ocean exchange information once per day. Heat and water fluxes are conserved exactly in the transfer between their different grids References Cattle, H. and J. Crossley, 1995: Modelling Arctic climate change. Phil Trans R Soc London A352 201-213 Cox, P,R Betts, C. Bunton, R. Essery, P.R. Rowntree, and J. Smith, 1999: The impact of new land surface physics on the gCM simulation of climate and climate sensitivity. Climate Dynamics 15: 183-203 climatology on the hadley Centre ccm. uart j, o Meteor. Soc 124 2517-25926. simple aerosol Edwards, J M. and A. Slingo, 1996: Sudies with a flexible new radiation code. I: Choosing a configuration for a large scale model. Quart. J. Roy. Meteor. Soc. 122: 689-719 Gent, P.R. and J C. Mc Williams, 1990: Isopycnal mixing in ocean circulation models. J. Phys. Oceanogr 20:150-155 Gordon, C, C. Cooper, C.A. Senior, H. Banks, J M. Gregory, T.C. Johns, J F B. Mitchell and R.A. Wood 2000: The simulation of SST, sea ice extents and ocean heat transports in a version of the Hadley Centre coupled model without flux adjustments. Climate Dynamics 16: 147-1682 Near-surface vertical mixing is parametrized partly by a Kraus-Turner mixed layer scheme for tracers (Kraus and Turner 1967), and a K-theory scheme (Pacanowski and Philander 1981) for momentum. Below the upper layers the vertical diffusivity is an increasing function of depth only. Convective adjustment is modified in the region of the Denmark Straits and Iceland-Scotland ridge better to represent down-slope mixing of the overflow water, which is allowed to find its proper level of neutral buoyancy rather than mixing vertically with surrounding water masses. The scheme is based on Roether et al (1994). Mediterranean water is partially mixed with Atlantic water across the Strait of Gibraltar as a simple representation of water mass exchange since the channel is not resolved in the model. The sea ice model uses a simple thermodynamic scheme including leads and snow-cover. Ice is advected by the surface ocean current, with convergence prevented when the depth exceeds 4 m (Cattle and Crossley 1995). There is no explicit representation of iceberg calving, so a prescribed water flux is returned to the ocean at a rate calibrated to balance the net snowfall accumulation on the ice sheets, geographically distributed within regions where icebergs are found. In order to avoid a global average salinity drift, surface water fluxes are converted to surface salinity fluxes using a constant reference salinity of 35 PSU. The model is initialized directly from the Levitus et al (1994, 1995) observed ocean state at rest, with a suitable atmospheric and sea ice state. The atmosphere and ocean exchange information once per day. Heat and water fluxes are conserved exactly in the transfer between their different grids. References: Cattle, H. and J. Crossley, 1995: Modelling Arctic climate change. Phil Trans R Soc London A352: 201-213. Cox, P., R. Betts, C. Bunton, R. Essery, P.R. Rowntree, and J. Smith, 1999: The impact of new land surface physics on the GCM simulation of climate and climate sensitivity. Climate Dynamics 15: 183-203. Cusack S., A. Slingo, J.M. Edwards, and M. Wild, 1998: The radiative impact of a simple aerosol climatology on the Hadley Centre GCM. Quart. J. Roy. Meteor. Soc. 124: 2517-2526. Edwards, J.M. and A. Slingo, 1996: Sudies with a flexible new radiation code. I: Choosing a configuration for a large scale model. Quart. J. Roy. Meteor. Soc. 122: 689-719. Gent, P.R. and J.C. McWilliams, 1990: Isopycnal mixing in ocean circulation models. J. Phys. Oceanogr. 20: 150-155. Gordon, C., C. Cooper, C.A. Senior, H. Banks, J.M. Gregory, T.C. Johns, J.F.B. Mitchell and R.A. Wood, 2000: The simulation of SST, sea ice extents and ocean heat transports in a version of the Hadley Centre coupled model without flux adjustments. Climate Dynamics 16: 147-168