On the influence of the parameterization of lateral boundary layers on the thermohaline circulation in coarse-resolution ocean models

Because of the first order geostrophic balance in the ocean interior, the parameterization of lateral boundary layers has more influence than the parameterization of viscosity on the thermohaline overturning and the deep water properties in coarse-resolution ocean circulation models. Different formulations of momentum dissipation and associated boundary conditions are implemented within a planetary-geostrophic ocean circulation model for a Cartesian coordinate, flat-bottomed, β-plane, with restoring boundary conditions for the surface density and zero wind stress. Traditional Laplacian friction with a no-slip boundary condition produces an interior circulation in good agreement with geostrophy and the Sverdrup balance, but generates very large vertical (diapycnal) transports at lateral boundaries, especially upwelling in the western boundary current and downwelling in the northeast corner. The meridional and zonal overturning are thus enhanced, but drive to depth surface waters that are not as cold as the ones in the deep convection regions. Rayleigh friction with various frictional closures for the alongshore velocities within a no-normal-flow boundary condition framework efficiently reduces the diapycnal vertical transports along the boundaries, by allowing horizontal recirculation of geostrophic currents impinging into coasts. Hence, these parameterizations induce weaker overturnings, with colder deep water and a sharper thermocline resulting in higher poleward heat transports. We suggest that the upwelling along the boundaries is a consequence of the coarse-resolution dynamics and not only horizontal diffusion (termed the Veronis effect, horizontal diffusion produces large diapycnal fluxes once the isopycnals are tilted by coastal upwellings). Alternative parameterizations for the lateral boundary layers reduce this effect without the need for rotating the mixing tensor along isopycnals. This model comparison proves the need to clearly assess the extent of the diapycnal upwelling in the western boundary currents and to develop physically-based parameterizations of lateral boundary layers in order to improve coarse-resolution OGCMs.

[1]  P. Delecluse,et al.  The Deep Interior Downwelling, the Veronis Effect, and Mesoscale Tracer Transport Parameterizations in an OGCM , 1999 .

[2]  R. Samelson,et al.  Large-scale circulation with small diapycnal diffusion: The two-thermocline limit , 1997 .

[3]  Andrew J. Weaver,et al.  On the Numerical Implementation of Advection Schemes for Use in Conjunction with Various Mixing Parameterizations in the GFDL Ocean Model , 1997 .

[4]  P. Gent,et al.  Eliassen–Palm Fluxes and the Momentum Equation in Non-Eddy-Resolving Ocean Circulation Models , 1996 .

[5]  Jiayan Yang,et al.  Deep-Water Upwelling in the Frictional Western Boundary Layer , 1996 .

[6]  D. Seidov.  An intermediate model for large-scale ocean circulation studies , 1996 .

[7]  J. Verron,et al.  The no-slip condition and separation of western boundary currents , 1996 .

[8]  Anthony C. Hirst,et al.  Deep-Water Properties and Surface Buoyancy Flux as Simulated by a Z-Coordinate Model Including Eddy-Induced Advection , 1996 .

[9]  D. Straub.  An inconsistency between two classical models of the ocean buoyancy driven circulation , 1996 .

[10]  C. Garrett,et al.  On a Recent Parameterization of Mesoscale Eddies , 1996 .

[11]  Gokhan Danabasoglu,et al.  Sensitivity of the global ocean circulation to parameterizations of mesoscale tracer transports , 1995 .

[12]  Andrew J. Weaver,et al.  Validation of sub‐grid‐scale mixing schemes using CFCs in a global ocean model , 1995 .

[13]  J. Marshall,et al.  Integral Effects of Deep Convection , 1995 .

[14]  P. Gent,et al.  Parameterizing eddy-induced tracer transports in ocean circulation models , 1995 .

[15]  Frank O. Bryan,et al.  An Overlooked Problem in Model Simulations of the Thermohaline Circulation and Heat Transport in the Atlantic Ocean , 1995 .

[16]  William J. Welch,et al.  Parameter space exploration of an ocean general circulation model using an isopycnal mixing parameterization , 1994 .

[17]  G. Danabasoglu,et al.  The Role of Mesoscale Tracer Transports in the Global Ocean Circulation , 1994, Science.

[18]  E. Sarachik,et al.  Thermohaline Oscillations Induced by Strong Steady Salinity Forcing of Ocean General Circulation Models , 1993 .

[19]  K. Uehara,et al.  A reduced-gravity model of the abyssal circulation with Newtonian cooling and horizontal diffusion , 1992 .

[20]  Eric P. Chassignet,et al.  The Influence of Boundary Conditions on Midlatitude Jet Separation in Ocean Numerical Models , 1991 .

[21]  Andrew J. Weaver,et al.  Evidence for decadal variability in an ocean general circulation model: An advective mechanism 1 , 1991 .

[22]  R. Greatbatch,et al.  On Parameterizing Vertical Mixing of Momentum in Non-eddy Resolving Ocean Models , 1990 .

[23]  R. Salmon.  The thermocline as an "internal boundary layer" , 1990 .

[24]  R. W. Stewart.  The no‐slip constraint and ocean models , 1989 .

[25]  A. Verdière.  On the interaction of wind and buoyancy driven gyres , 1989 .

[26]  G. Csanady.  Energy Dissipation and Upwelling in a Western Boundary Current , 1989 .

[27]  S. Levitus,et al.  New estimates of the available potential energy in the world ocean , 1989 .

[28]  R. Chervin,et al.  A simulation of the global ocean circulation with resolved eddies , 1988 .

[29]  Frank O. Bryan,et al.  Parameter sensitivity of primitive equation ocean general circulation models , 1987 .

[30]  P. Killworth.  A two-level wind and buoyancy driven thermocline model , 1985 .

[31]  K. Bryan.  Poleward heat transport in the ocean , 1983 .

[32]  L. Talley,et al.  The subpolar mode water of the North Atlantic , 1982 .

[33]  M. Redi.  Oceanic Isopycnal Mixing by Coordinate Rotation , 1982 .

[34]  William R. Young,et al.  Homogenization of potential vorticity in planetary gyres , 1982, Journal of Fluid Mechanics.

[35]  W. R. Holland.  Ocean tracer distributions: Part I. A preliminary numerical experiment , 1971 .

[36]  R. Haney.  Surface Thermal Boundary Condition for Ocean Circulation Models , 1971 .

[37]  K. Bryan.  Measurements of meridional heat transport by ocean currents , 1962 .

[38]  B. Bolin,et al.  On the abyssal circulation of the world ocean—IV. Origin and rate of circulation of deep ocean water as determined with the aid of tracers , 1961 .

[39]  P. Welander.  An Advective Model of the Ocean Thermocline , 1959 .

[40]  A. Robinson,et al.  The Oceanic Thermocline and the Associated Thermohaline Circulation , 1959 .

[41]  Walter Munk,et al.  ON THE WIND-DRIVEN OCEAN CIRCULATION , 1950 .

[42]  H. Stommel,et al.  The westward intensification of wind‐driven ocean currents , 1948 .

[43]  R. Samelson,et al.  A Simple Friction and Diffusion Scheme for Planetary Geostrophic Basin Models , 1997 .

[44]  Stefan Rahmstorf,et al.  A fast and complete convection scheme for ocean models , 1993 .

[45]  Shengpan P. Zhang,et al.  Multi-year current time series in the eastern North Atlantic ocean , 1992 .

[46]  P. Gent,et al.  Isopycnal mixing in ocean circulation models , 1990 .

[47]  A. Semtner.  Finite-Difference Formulation of a World Ocean Model , 1986 .

[48]  K. Hasselmann.  An ocean model for climate variability studies , 1982 .

[49]  G. Veronis.  Large Scale Ocean Circulation , 1973 .

[50]  H. Stommel,et al.  On the abyssal circulation of the world ocean — II. An idealized model of the circulation pattern and amplitude in oceanic basins , 1959 .