MOM4_L40 is a global oceanic general circulation model (OGCM) with a tripolar grid of Murray (1996). The horizontal resolution is 1° longitude by 1/3° latitude between 10°S and 10°N ranged to 1° at 30°S, 30°N polarward, and there are 40 z-levels in the vertical. The two northern poles of the curvilinear grid are shifted to land areas over North America and Eurasia, respectively. The first 20 levels are placed between the surface and the 200-m depth of the upper ocean. MOM4_L40 is originated from the Z-coordinate Modular Ocean Model version 4 (MOM4) developed by the Geophysical Fluid Dynamics Laboratory (GFDL). It adopts some mature parameterization schemes used in MOM4 (Griffies et al. 2005), including Sweby’s tracer-based third-order advection scheme, isopycnal tracer mixing and diffusion scheme, Laplace horizontal friction scheme, KPP vertical mixing scheme, complete convection scheme, overflow scheme of topographic processing of sea bottom boundary/ steep slopes, and shortwave penetration schemes based on spatial distribution of chlorophyll concentration.

The biogeochemistry module to simulate the ocean carbon cycle in MOM4_L40 is based on the protocols from the Ocean Carbon Cycle Model Intercomparison Project–Phase 2 (OCMIP2, http://www.ipsl.jussieu.fr/OCMIP/ phase2/). The reasonable simulations have gained for large scale temperature, salt distribution, main circulations, seasonal and inter-annual variability. Meanwhile, there are some deficiencies in tropical regions and the seasonal variability in tropical eastern Pacific.

In recent years, we have modified MOM4_L40 which based on the GFDL’s MOM4. The main modifications are resolution and topography, introduction of carbon cycle module and wave model, increase of model output variables.