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Abstract The western Arctic Ocean (WAO) has experienced increased heat transport into the region, sea-ice reduction, and changes to the WAO nitrous oxide (N₂O) cycles from greenhouse gases. We investigated WAO N₂O dynamics through an intensive and precise N₂O 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 N₂O. 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 N₂O production (i.e., through nitrification), with N₂O over-saturation. During summer 2017, the southern region acted as a source of atmospheric N₂O (mean: + 2.3 ± 2.7 μmol N₂O m⁻²day⁻¹), whereas the northern region acted as a sink (mean − 1.3 ± 1.5 μmol N₂O m⁻²day⁻¹). If Arctic environmental changes continue to accelerate and consequently drive the productivity of the Arctic Ocean, the WAO may become a N₂O “hot spot”, and therefore, a key region requiring continued observations to both understand N₂O dynamics and possibly predict their future changes. 

Abstract Widespread ice shelf thinning has been recorded in the Amundsen Sea in recent decades, driven by basal melting and intrusions of relatively warm Circumpolar Deep Water (CDW) onto the continental shelf. The Dotson Ice Shelf (DIS) is located to the south of the Amundsen Sea polynya, and has a high basal melting rate because modified CDW (mCDW) fills the Dotson‐Getz Trough (DGT) and reaches the base of the ice shelf. Here, hydrographic data in the DGT obtained during seven oceanographic surveys from 2007 to 2018 were used to study the interannual variation in mCDW volume and properties and their causes. Although mCDW volume showed relatively weak interannual variations at the continental shelf break, these variations intensified southward and reached a maximum in front of the DIS. There, the mCDW volume was ∼8,000 km³in 2007, rapidly decreased to 4,700 km³in 2014 before rebounding to 7,300 km³in 2018. We find that such interannual variability is coherent with local Ekman pumping integrated along the DGT modulated by the presence of sea ice, and complementing earlier theories involving shelf break winds only. The interannual variability in strength of the dominant south‐southeast coastal wind modulates the amplitude of Ekman upwelling along the eastern boundary of the Amundsen Sea polynya during the austral summers of the surveyed years, apparently leading to change in the volume of mCDW along the DGT. We note a strong correlation between the wind variability and the longitudinal location of the Amundsen Sea Low.