Significant role of physical transport in the marine carbon monoxide (CO) cycle – Observations in the East Sea (Sea of Japan), the Western North Pacific, and the Bering Sea in summer

Abstract. The carbon monoxide (CO) in the marine boundary layer and in the surface waters and water column were measured along the Northwestern Pacific limb from Korean Peninsula to Alaska, U.S.A. in summer 2012. The observation allows us to estimate the CO budgets in the surface mixed layer of the three distinct regimes, the East Sea (ES), the Northwest Pacific (NP), and the Bering Sea (BS). Microbial consumption rates were 33(±22) μmol m^-2 day^-1, 23(±11) μmol m^-2 day^-1, and 77(±32) μmol m^-2 day^-1, and CO production rates were 70(±49) μmol m^-2 day^-1, 20(±11) μmol m^-2 day^-1, and 19(±7) μmol m^-2 day^-1 in ES, NP and BS, respectively, both of which are the dominant components of the CO budget in the ocean. The other two known components, air-sea gas exchange and downward mixing remain negligible (less than 2 μmol m^-2 day^-1) in all regimes. While the CO budget in the surface mixed layer of NP is in balance, the CO production surpassed the consumption in ES and vice versa in BS. The significant imbalances in the CO budget in ES and BS requires external physical transport such as lateral advection, subduction, or ventilation. Indeed, the first order increase of the CO column burden to the extent that the imbalance in the CO budget increases points to the significant play of the physical transport in the CO cycles. Our observation, for the first time, points to the potential importance of physical transport in the marine CO cycle.