In total, we have conducted three simulation cases (Table ), coined the noBT, avgBT, and maxBT cases. The noBT case contains no oceanic emissions of benzene and toluene; the avgBT case includes the average oceanic emission fluxes of benzene and toluene for both polar oceans (all oceanic regions > 60 ºN and < -55 ºS) taken from the cruise measurements; the maxBT case applies the maximum oceanic fluxes for the polar oceans (i.e. the highest hourly measured/calculated oceanic outgassing flux). The difference in the atmospheric compositions (benzene and toluene mole fractions, OH, and SOA) between avgBT and noBT cases represent the effects of the average oceanic flux of benzene and toluene in the atmosphere. The difference between maxBT and noBT illustrates the impact of the maximum fluxes. Note that all modelling results have been averaged by sampling CAM-Chem grid points at the exact location and time (month) of each cruise. By designing these cases, we attempt to capture the most probable effects of the additional oceanic aromatic emissions (noBT v.s. avgBT) as well as the possible range of such effects (noBT v.s. maxBT). The CAM-Chem simulation results are described in the section "Atmopsheric effects of oceanic benzene and toluene emissions". Table Modelling results showing the impact of benzene and toluene emissions on atmospheric benzene, toluene and OH mole fractions in the polar regions. Sampling months were Feb-Mar 2019 for the Southern Ocean and Jul-Aug 2017 for the Arctic. Three model runs were; "no BT" = no ocean benzene/toluene fluxes, "avg BT" = mean benzene/toluene ocean fluxes, "max BT" = highest measured benzene/toluene fluxes (See Supplement S2). "absdiff" = absolute difference, "reldiff" = relative difference or relative change. the underway inlet are slightly higher than those measured from the underway inlet. In this manuscript, we display measurements from both sampling techniques which show no obvious bias. It is possible that mean underway concentrations are slightly higher as they by chance capture episodes of higher concentrations during this cruise. We note that for the Antarctic cruise, benzene and toluene seawater measurements did not appear to be affected by photochemical production within the SFCE.