The Atlantic Ocean surface microlayer from 50°N to 50°S is ubiquitously enriched in surfactants at wind speeds up to 13 m s−1

We report the first measurements of surfactant activity (SA) in the sea surface microlayer (SML) and in sub-surface waters (SSW) at the ocean basin scale, for two Atlantic Meridional Transects (AMT) from 50°N to 50°S during 2014 and 2015. Northern hemisphere (NH) SA was significantly higher than southern hemisphere (SH) SA in the SML and in the SSW. SA enrichment factors (EF = SASML/SASSW) were also higher in the NH, for wind speeds up to ~13 m s-1, questioning a prior assertion that Atlantic Ocean wind speeds > 12 m s-1 poleward of 30°N and 30°S would preclude high EFs and showing the SML to be self-sustaining with respect to SA. Our results imply that surfactants exert a control on air-sea CO2 exchange across the whole North Atlantic CO2 sink region and that the contribution made by high wind, high latitude oceans to air-sea gas exchange globally should be re-examined.