To mix, or not to mix, that is the question: analysis of heat and carbon uptake across different resolutions in GFDL's OMIP and OMIP-BGC simulations

Ocean model physics and resolution play an important role in determining heat and carbon uptake. Heat uptake varied considerably among the previous generation of CORE-forced ocean models (Griffies et al. 2009) while carbon uptake in both ocean-only (Le Quéré et al. 2017) and coupled (Frölicher 2015) frameworks was more consistent. In support of CMIP6, NOAA-GFDL developed a new ocean model, MOM6, configured in both an eddy-permitting 0.25° horizontal resolution and a 0.5° resolution reliant on mesoscale mixing parameterizations. Here we examine oceanic heat and carbon uptake under CORE interannual forcing using both ocean-only model configurations and compare them with a third 0.5° ocean-only simulation with the mesoscale eddy parameterization turned off. We find that is possible to configure the mesoscale and sub-mesoscale mixing in the 0.5° configuration such that both horizontal resolutions produce a similar global volume-mean heat uptake that is also small relative to the range of previous generation OMIP simulations. The 0.5° configuration with parameterized mesoscale mixing is subject to a warm drift in the thermocline region that is balanced by a cold drift in the sub-thermocline and abyssal regions and this general pattern is amplified when the mesoscale mixing parameterization is turned off. The magnitude of these depth-dependent drifts patterns are greatly reduced, however, in the eddy-permitting 0.25° configuration. The simulations include a reduced biogeochemistry model, BLING, and the 0.5° configurations also simulate abiotic carbon and ¹⁴C. The effects of resolution and mesoscale eddy parameterizations on ventilation as well as on the carbon uptake will also be discussed.