| Summary: | Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 124(7), (2019): 4605-4617, doi:10.1029/2018JC014928. We report the significant impact of near‐inertial waves (NIWs) on vertical mixing and air‐sea carbon dioxide (CO2) fluxes in the Southern Ocean using a biogeochemical model coupled to an eddy‐rich ocean circulation model. The effects of high‐frequency processes are quantified by comparing the fully coupled solution (ONLINE) to two offline simulations based on 5‐day‐averaged output of the ONLINE simulation: one that uses vertical mixing archived from the ONLINE model (CTRL) and another in which vertical mixing is recomputed from the 5‐day average hydrodynamic fields (5dAVG). In this latter simulation, processes with temporal variabilities of a few days including NIWs are excluded in the biogeochemical simulation. Suppression of these processes reduces vertical shear and vertical mixing in the upper ocean, leading to decreased supply of carbon‐rich water from below, less CO2 outgassing in austral winter, and more uptake in summer. The net change amounts up to one third of the seasonal variability in Southern Ocean CO2 flux. Our results clearly demonstrate the importance of resolving high‐frequency processes such as NIWs to better estimate the carbon cycle in numerical model simulations. The MITgcm can be obtained from http://mitgcm.org website. Resources supporting this work were provided by the NASA High‐End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center with the Award SMD‐15‐5752. H. S., J. M., and D. J. M. were supported by the NSF MOBY project (OCE‐1048926 and OCE‐1048897). H. S. acknowledges the support by National Research Foundation of Korea (NRF) grant (NRF‐2019R1C1C1003663) and Yonsei University Research Fund of 2018‐22‐0053. D. J. M. also gratefully ...
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