CSIRO global coupled ocean-atmosphere-sea-ice model (CSIRO coupled)
 
The coupled model is best described by Gordon and O'Farrell (1997).
The version used here includes the GM ocean mixing scheme described by
Hirst et al (1996).
The CSIRO coupled model involves global atmospheric, oceanic, sea-ice and
biospheric sub-models (Hirst et al., 1996). The atmospheric, biospheric
and sea-ice sub-models are the same as those used in the CSIRO Mark 2 GCM.
There is a diagnostic cloud scheme. The model is fully flux corrected.
Atmospheric and oceanic components use a spectral R21 horizontal grid (each
gridbox measuring about 625 km by 350 km) with 9 vertical levels in the
atmosphere and 21 levels in the ocean. The ocean model has a heat transport
scheme which significantly reduces problems associated with excessive mixing
in the Southern Ocean. On a CRAY YMP computer, climate variables for one
model day take 60 seconds to evaluate, so a 10 year run takes 61 hours.
 
Coupling the atmosphere to the ocean is technically challenging because the
ocean has a much longer timescale of variability than the atmosphere. The
coupled model requires adjustments to the fluxes of heat, salinity and wind
stress which link the atmospheric and oceanic components. Adjusting the heat
fluxes at the ocean/atmosphere/ice interface is performed by running the
ocean and atmosphere models independently and computing (i) the fluxes
required by the ocean model when driven by observed SST, sea-surface surface
salinity (SSS) and wind stress, and (ii) the heat fluxes generated by the
atmosphere/ice model with observed SST and SSS. The flux adjustment is the
difference between (i) and (ii). These adjustments were used in the fully
coupled model which generates its own SST, SSS and wind stress.
 
When flux adjustments are applied in the coupled experiment with present
levels of CO2, small errors in the ocean model remain. These errors lead to
a drift in climate rather than equilibrium. Additional adjustments were made
to the model-generated SST to reduce climatic drift and this resulted in
negligible drift in global average SST in the control run. The same flux
adjustments are applied to the transient CO2 run, which places an artificial
constraint on the variability of sea-surface temperature as the climate
changes. This limitation may have important implications for ocean behaviour
and atmospheric circulation patterns.

References

Charlson, R. J., J. Langner, H. Rohde, C. B. Leovy, and S. G. Warren,
1991: Perturbation of the Northern Hemisphere radiative balance by
backscattering from anthropogenic sulfate aerosols. Tellus, 43AB,
152-163. 

Gordon, H. B., and S. P. O'Farrell, 1997: Transient climate change in
the CSIRO coupled model with dynamic sea ice. Mon. Wea. Rev., 125,
875- 907. 

Hirst, A. C., H. B. Gordon, and S. P. O'Farrell, 1996: Global warming
in a coupled climate model including oceanic eddy-induced advection.
Geophys. Res. Lett., 23, 3361-3364. 

Kiehl, J. T., and B. P. Briegleb, 1993: The relative roles of sulfate
aerosols and greenhouse gases in climate forcing. Science, 260,
311-314. 

Mitchell, J. F. B., and T. C. Johns, 1997: On modification of global
warming by sulfate aerosols. J. Climate, 10, 245-267.