An assessment of the Geophysical Fluid Dynamics Laboratory ocean model with coarse resolution: Annual‐mean climatology

The Geophysical Fluid Dynamics Laboratory Modular Ocean Model 2.2 code with coarse resolution (4° × 3°) is assessed by performing three experiments and comparing their equilibrated solutions with recent observationally based analyses (OBAs). The first experiment (E1) uses subgrid-scale horizontal diffusion and surface boundary conditions which relax surface temperature and salinity toward observations. The second (E2) replaces the physically incorrect heat and moisture flux boundary conditions of E1 by flux conditions taken from OBAs, plus a term relaxing surface temperatures toward observations. The third (E3) uses the same surface boundary conditions as E2 but replaces the horizontal diffusion by the Gent-McWilliams (GM) parameterization of isopycnal diffusion. Under the restoring surface boundary conditions (E1), the North Atlantic overturning rate is about 17 Sv, smaller than in OBAs, the maximum poleward heat transport in the Northern Hemisphere is 1.2 Petawatts (PW), also smaller than in OBAs, and in the Antarctic Circumpolar Current (ACC) region the poleward heat transport is 1.3 PW, much larger than in OBAs. Under the more realistic flux boundary condition (E2) the overturning rate increases to an unrealistically large level of 40 Sv, and the poleward heat transports are only slightly improved. When the GM parameterization is employed (E3), the overturning is reduced to 28 Sv, and the poleward heat transport in the ACC region is reduced to 0.3 PW; both results are consistent with OBAs. However, there is only a slight further improvement in the poleward heat transport in the Northern Hemisphere, which now has a peak value of 1.6 PW, still about 0.5 PW less than in OBAs. The sea surface temperature errors in E3 are consistent with the conclusion that the heat transport in the Northern Hemisphere is still being underestimated. All the experiments show strong systematic biases in the salinity field.

[1]  T. H. Haar,et al.  Estimating the Meridional Energy Transports in the Atmosphere and Ocean , 1985 .

[2]  Taikan Oki,et al.  Global atmospheric water balance and runoff from large river basins , 1995 .

[3]  J. Marotzke Ocean Models in Climate Problems , 1994 .

[4]  Robert Marsh,et al.  An Intercomparison of a Bryan–Cox-Type Ocean Model and an Isopycnic Ocean Model. Part I: The Subpolar Gyre and High-Latitude Processes , 1996 .

[5]  K. Bryan Accelerating the Convergence to Equilibrium of Ocean-Climate Models , 1984 .

[6]  M. Gregg,et al.  Diapycnal mixing in the thermocline: A review , 1987 .

[7]  Carl Wunsch,et al.  An estimate of global ocean circulation and heat fluxes , 1996, Nature.

[8]  E. Maier‐Reimer,et al.  Mixed boundary conditions in ocean general circulation models and their influence on the stability of the model's conveyor belt , 1994 .

[9]  Josef M. Oberhuber,et al.  An Atlas Based on the COADS Data Set: the Budgets of Heat Buoyancy and Turbulent Kinetic Energy at t , 1988 .

[10]  P. Bogden,et al.  Evaporation Minus Precipitation and Density Fluxes for the North Atlantic , 1989 .

[11]  L. Slørdal,et al.  Adjustment to JEBAR Forcing in a Rotating Ocean , 1996 .

[12]  James C. McWilliams,et al.  Sensitivity to Surface Forcing and Boundary Layer Mixing in a Global Ocean Model: Annual-Mean Climatology , 1997 .

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

[14]  R. Schmitt The ocean component of the global water cycle (95RG00184) , 1995 .

[15]  R. Schmitt,et al.  The Goldsbrough–Stommel Circulation of the World Oceans , 1993 .

[16]  S. Levitus Climatological Atlas of the World Ocean , 1982 .

[17]  Jane Hsiung,et al.  Estimates of Global Oceanic Meridional Heat Transport , 1985 .

[18]  R. A. Plumb,et al.  The Zonally Averaged Transport Characteristics of the GFDL General Circulation/Transport Model , 1987 .

[19]  R. Huang,et al.  Mixing and Energetics of the Oceanic Thermohaline Circulation , 1999 .

[20]  W. Large,et al.  Sensible and Latent Heat Flux Measurements over the Ocean , 1982 .

[21]  W. Munk,et al.  Abyssal recipes II: energetics of tidal and wind mixing , 1998 .

[22]  P. Delecluse,et al.  Measurements within the Pacific-Indian oceans throughflow region , 1994 .

[23]  K. Trenberth,et al.  The global heat balance: heat transports in the atmosphere and ocean , 1994 .

[24]  J. S. Godfrey,et al.  Why Does the Indonesian Throughflow Appear to Originate from the North Pacific , 1993 .

[25]  Philip B. Duffy,et al.  An extended data set of river discharges for validation of general circulation models , 1996 .

[26]  D. Randall,et al.  Cloud-radiative effects on implied oceanic energy transports as simulated by Atmospheric General Circulation Models , 1995 .

[27]  R. Schmitt,et al.  Transport of freshwater by the oceans , 1992 .

[28]  J. Toggweiler,et al.  Instability of the thermohaline circulation with respect to mixed boundary conditions: is it really a problem for realistic models? , 1994 .

[29]  J. Marshall,et al.  Inferring the Subduction Rate and Period over the North Atlantic , 1993 .

[30]  F. Smith,et al.  Transport and heat flux of the Florida Current at 27°N derived from cross-stream voltages and profiling data: theory and observations , 1992, Philosophical Transactions of the Royal Society of London. Series A: Physical and Engineering Sciences.

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

[32]  W. Large,et al.  A Global Ocean Wind Stress Climatology Based on ECMWF Analyses , 1989 .

[33]  D. Caldwell,et al.  Surface Stresses Produced by Rainfall , 1971 .

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

[35]  W. Liu,et al.  Bulk Parameterization of Air-Sea Exchanges of Heat and Water Vapor Including the Molecular Constraints at the Interface , 1979 .

[36]  M. Suter,et al.  AMS radiocarbon dating and varve chronology of Lake Soppensee: 6000 to 12000 14C years BP , 1993 .

[37]  Philip B. Duffy,et al.  Effects of Subgrid-Scale Mixing Parameterizations on Simulated Distributions of Natural 14C, Temperature, and Salinity in a Three-Dimensional Ocean General Circulation Model , 1997 .

[38]  R. Dickson,et al.  The production of North Atlantic Deep Water: Sources, rates, and pathways , 1994 .

[39]  R. Peterson The boundary currents in the western Argentine Basin , 1992 .

[40]  G. Holloway,et al.  Estimating Southern Ocean eddy flux of heat and salt from satellite altimetry , 1988, Nature.

[41]  Carl Wunsch,et al.  Two transatlantic sections: meridional circulation and heat flux in the subtropical North Atlantic Ocean , 1985 .

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

[43]  A. Gordon,et al.  Geostrophic circulation of the Brazil-Falkland confluence , 1986 .

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

[45]  R. G. Johnson Climate control required a dam at the Strait of Gibraltar , 1997 .

[46]  K. Trenberth Using Atmospheric Budgets as a Constraint on Surface Fluxes , 1997 .

[47]  John K. Dukowicz,et al.  Isoneutral Diffusion in a z-Coordinate Ocean Model , 1998 .

[48]  Klaus Hasselmann,et al.  Mean Circulation of the Hamburg LSG OGCM and Its Sensitivity to the Thermohaline Surface Forcing , 1993 .

[49]  Anthony C. Hirst,et al.  Chlorofluorocarbon uptake in a world ocean model 2 , 1997 .

[50]  K. Bryan A Numerical Method for the Study of the Circulation of the World Ocean , 1997 .

[51]  Peter H. Stone,et al.  Destabilization of the thermohaline circulation by atmospheric eddy transports , 1994 .

[52]  Nelson G. Hogg,et al.  On the transport of the gulf stream between cape hatteras and the grand banks , 1992 .

[53]  M. England Representing the global-scale water masses in ocean general circulation models , 1993 .

[54]  Sol Hellerman,et al.  Normal Monthly Wind Stress Over the World Ocean with Error Estimates , 1983 .

[55]  R. Huang,et al.  Ventilation of the subtropical North Pacific , 1994 .

[56]  D. Hu Global-Scale Water Masses, Meridional Circulation, and Heat Transport Simulated with a Global Isopycnal Ocean Model* , 1997 .

[57]  J. S. Godfrey,et al.  The role of Indonesian throughflow in a global ocean GCM , 1993 .

[58]  Bruce A. Warren,et al.  A hydrographic section across the subtropical South Indian Ocean , 1993 .

[59]  A. Moore,et al.  The response of a global ocean general circulation model to climatological surface boundary conditions for temperature and salinity , 1993 .

[60]  W. Schmitz On the interbasin‐scale thermohaline circulation , 1995 .

[61]  N. P. Fofonoff,et al.  Algorithms for Computation of Fundamental Properties of Seawater. Endorsed by Unesco/SCOR/ICES/IAPSO Joint Panel on Oceanographic Tables and Standards and SCOR Working Group 51. Unesco Technical Papers in Marine Science, No. 44. , 1983 .

[62]  L. Pratt The physical oceanography of sea straits , 1990 .

[63]  J. Klinck,et al.  The physics of the Antarctic Circumpolar Current , 1986 .

[64]  M. Levine,et al.  The advective flux of heat by mean geostrophic motions in the Southern Ocean , 1981 .

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

[66]  A. E. Gill,et al.  Effects of geometry on the circulation of a three-dimensional southern-hemisphere ocean model , 1971 .

[67]  K. Aagaard,et al.  Transports through Bering Strait: Annual and interannual variability , 1988 .

[68]  Peter J. Webster,et al.  The role of hydrological processes in ocean‐atmosphere interactions , 1994 .

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

[70]  James C. McWilliams,et al.  Approach to Equilibrium in Accelerated Global Oceanic Models. , 1996 .

[71]  S. Rahmstorf Bifurcations of the Atlantic thermohaline circulation in response to changes in the hydrological cycle , 1995, Nature.

[72]  J. Marotzke,et al.  Multiple Equilibria of the Global Thermohaline Circulation , 1991 .

[73]  G. Shaffer,et al.  Role of the Bering Strait in controlling North Atlantic ocean circulation and climate , 1994, Nature.

[74]  W. Large,et al.  Oceanic vertical mixing: a review and a model with a nonlocal boundary layer parameterization , 1994 .

[75]  J. Lutjeharms,et al.  The flow field of the subtropical gyre of the South Indian Ocean , 1997 .

[76]  C. Iselin The influence of vertical and lateral turbulence on the characteristics of the waters at mid‐depths , 1939 .