Atmospheric mole fractions of benzene and toluene were not measured on the Arctic cruise. To estimate air-sea flux and mean saturation, we used previous air measurements of these compounds at a similar location (western Canadian Arctic) and similar time of year (August-September) by Sjostedt et al. (13 pmol mol -1 benzene and 4 pmol mol -1 toluene). This is comparable to a more recent study by Pernov et al. , who measured 27 pmol mol -1 benzene near the coast in Northeast Greenland. Using the measurements from Sjostedt et al. , saturation and fluxes were calculated and are presented in Figure . The ocean was highly supersaturated in benzene (610 ± 386 %) and toluene (2335 ± 1175 %) and thus uncertainty in the air mole fractions should not affect the flux very much, similarly to isoprene . In the supplement Table , we show that alternative fluxes and saturations calculated with air mole fractions in the Arctic modelled by Cabrera-Perez et al. , which are higher than those of Sjostedt et al. . The results illustrate that the choice of the air mole fraction does not change the conclusion that the Arctic ocean was consistently outgassing benzene and toluene. Cruise mean fluxes were 0.023 ± 0.028 µmol m -2 d -1 for benzene and 0.034 ± 0.041 µmol m -2 d -1 for toluene. Surface ocean concentrations and supersaturations were much higher in the Arctic than in the Southern Ocean. However, the mean fluxes from the two cruises were similar. This is due to the lower estimated air-sea transfer velocities in the Arctic, which resulted from lower wind speeds as well as sea ice acting as a barrier to air-sea exchange in our calculation. Benzene and toluene fluxes displayed a lower median than mean flux (benzene median flux 0.014 µmol m -2 d -1 , toluene median flux 0.020 µmol m -2 d -1 ). Therefore, reported mean fluxes were influenced by strong outgassing episodes that coincided with above-average seawater concentrations, high winds and low sea ice cover, e.g. on 31/07 and 01/08. The highest hourly measured outgassing flux was 0.158 µmol m -2 d -1 for benzene and 0.268 µmol m -2 d -1 for toluene. Similar to the cruise in the Southern Ocean, the mean emissions of benzene and toluene from this cruise in the Arctic marginal ice zone are comparable (within 0.024 µmol m -2 d -1 ) to the isoprene flux from the same deployment .