Nitric oxide supersaturation in the surface waters of the oligotrophic Atlantic Ocean

Abstract Atmospheric nitric oxide (NO) is a pollutant and climate‐relevant trace gas. Dissolved NO accumulates in the surface ocean and therefore the ocean is a natural source of atmospheric NO. It is generally assumed that NO in the surface ocean is produced photochemically from nitrite (NO 2 − ). Here, we present the first dissolved NO measurements in the oligotrophic North Atlantic Ocean during an east‐to‐west transect (December 2021/January 2022). NO concentrations and mean saturations ranged from 9.4 to 48.2 pM and 10,355% to 19,484%, respectively, indicating that the study site was indeed a significant source of atmospheric NO despite extremely low NO 2 − concentrations. NO concentrations correlated significantly with phytoplankton pigment concentrations, indicating that NO variability may be influenced by phytoplankton‐related processes rather than photochemical pathways alone. These findings highlight the need to further investigate the production mechanism of NO in nutrient‐poor oceanic environments.