NO dynamics in the western Arctic Ocean during the summer of 2017.

The western Arctic Ocean (WAO) has experienced increased heat transport into the region, sea-ice reduction, and changes to the WAO nitrous oxide (NO) cycles from greenhouse gases. We investigated WAO NO dynamics through an intensive and precise NO survey during the open-water season of summer 2017. The effects of physical processes (i.e., solubility and advection) were dominant in both the surface (0-50 m) and deep layers (200-2200 m) of the northern Chukchi Sea with an under-saturation of NO. By contrast, both the surface layer (0-50 m) of the southern Chukchi Sea and the intermediate (50-200 m) layer of the northern Chukchi Sea were significantly influenced by biogeochemically derived NO production (i.e., through nitrification), with NO over-saturation. During summer 2017, the southern region acted as a source of atmospheric NO (mean: + 2.3 ± 2.7 μmol NO m day), whereas the northern region acted as a sink (mean - 1.3 ± 1.5 μmol NO m day). If Arctic environmental changes continue to accelerate and consequently drive the productivity of the Arctic Ocean, the WAO may become a NO "hot spot", and therefore, a key region requiring continued observations to both understand NO dynamics and possibly predict their future changes.