Underway concentration measurements and air-sea flux estimates of benzene and toluene in the Canadian Arctic marginal sea ice zone during boreal summer are shown in Figure . Underway and 5 m discrete measurements agreed well within measurement uncertainty. Mean seawater concentrations were two times for benzene (37 ± 24 pmol dm -3 ) and three times for toluene (46 ± 24 pmol dm -3 ) higher than those in the Southern Ocean cruise. This could be due to either higher biological activity (it was earlier in the productive season) or larger anthropogenic influence and thus higher contribution of anthropogenic benzene and toluene to observed seawater concentrations. Due to the short residence times of benzene and toluene in unpolluted seawater (less than 1 day (42)), we expect any anthropogenic influence to be due to local sources. Similar to the cruise in the Southern Ocean, concentrations displayed a wide range from near the LOD to up to 131 pmol dm -3 and 139 pmol dm -3 for benzene and toluene respectively. Also, similar to the Southern Ocean, the median benzene concentration (30 pmol dm -3 ) was lower than the mean, though in contrast, toluene median concentration was the same as the mean. Skewed data distribution of peak concentrations amongst an apparently constant background is typical for biologically produced compounds. There was no significant correlation between Chl a and benzene (0<R<0.01; P=0.53; N=219) or toluene (0<R<0.02; P=0.058; N=223). The depth profiles suggest that the lack of a correlation with Chl a is probably because much of the biological activity and production of benzene and toluene occurred at depths below 5 m while the underway measurements were taken at 3-4 m. Benzene and toluene also did not correlate with isoprene or sea ice cover. In contrast to the Southern Ocean, here there was a weak yet significant correlation between benzene and toluene (R=0.21; P<0.001; N=245). Both benzene and toluene correlated positively with seawater DMS (R=0.18; P<0.001; N=239; and R=0.10; P<0.001; N=239, respectively).