[A-OS17] Chemical and Biological Oceanography

[AOS17-03] Improvements of ocean biogeochemical simulation of the North Pacific Ocean due to an enhanced horizontal resolution of an ocean model

*Hiroyuki Tsujino¹, Toyama Katsuya¹, Hideyuki Nakano¹, Shiro Nishikawa², Toru Sugiyama², Haruka Nishikawa², Yoichi Ishikawa² (1.Japan Meteorological Agency / Meteorological Research Institute, 2.Japan Agency for Marine-Earth Science and Technology)

Keywords:ocean biogeochemical model, ocean carbon circulation

The earth system model used by MRI for a series of CMIP6 experiments adopted a low-resolution ocean component whose grid size is around 100 km. Considering a possibility of using higher ocean model resolution in future projection experiments, we embedded a 10-km resolution North Pacific Ocean model into the global ocean model used for CMIP6 and conducted an ocean biogeochemical simulation following OMIP protocols to evaluate its overall performance. Changes of the simulated biogeochemical fields in the North Pacific Ocean due to the enhanced horizontal resolution are studied by comparing between high and low resolution simulations. Enhancing the model horizontal resolution in the North Pacific Ocean does not make major impacts on globally integrated surface carbon flux budgets, but it brings about improvements in local distributions of dissolved inorganic carbon and surface fluxes. Specifically, more anthropogenic carbon is stored in the Kuroshio recirculation gyre as inferred from observations, insufficient outgassing in annual mean surface carbon flux is improved in the subpolar and the eastern tropical coastal regions. Primary productivity is enhanced in the subtropics presumably owing to the presence of mesoscale eddies. Most of these improvements are caused by those of physical fields. The present assessment would motivate use of high resolution models in the future projection experiments of ocean biogeochemical fields in the North Pacific Ocean.