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Abstract Analysis of dissolved oxygen (O₂) in the Arctic's surface ocean provides insights into gas transfer between the atmosphere‐ice‐ocean system, water mass dynamics, and biogeochemical processes. In the Arctic Ocean's Canada Basin mixed layer, higher O₂concentrations are generally observed under sea ice compared to open water regions. Annual cycles of O₂and O₂saturation, increasing from summer through spring and then sharply declining to late summer, are tightly linked to sea ice cover. The primary fluxes that influence seasonal variability of O₂are modeled and compared to Ice‐Tethered Profiler O₂observations to understand the relative role of each flux in the annual cycle. Findings suggest that sea ice melt/growth dominates seasonal variations in mixed layer O₂, with minor contributions from vertical entrainment and atmospheric exchange. While the influence of biological activity on O₂variability cannot be directly assessed, indirect evidence suggests relatively minor contributions, although with significant uncertainty. Past studies show that O₂molecules are expelled from sea ice during brine rejection; sea ice cover can then inhibit air‐sea gas exchange resulting in winter mixed layers that are super‐saturated. Decreasing mixed layer O₂concentrations and saturation levels are observed during winter months between 2007 and 2019 in the Canada Basin. Only a minor portion of the decreasing trend in wintertime O₂can be attributed to decreased solubility. This suggests the O₂decline may be linked to more efficient air‐sea exchange associated with increased open water areas in the winter sea ice pack that are not necessarily detectable via satellite observations. 

Abstract Analysis of dissolved oxygen (O₂) in the Arctic's surface ocean provides insights into gas transfer between the atmosphere‐ice‐ocean system, water mass dynamics, and biogeochemical processes. In the Arctic Ocean's Canada Basin mixed layer, higher O₂concentrations are generally observed under sea ice compared to open water regions. Annual cycles of O₂and O₂saturation, increasing from summer through spring and then sharply declining to late summer, are tightly linked to sea ice cover. The primary fluxes that influence seasonal variability of O₂are modeled and compared to Ice‐Tethered Profiler O₂observations to understand the relative role of each flux in the annual cycle. Findings suggest that sea ice melt/growth dominates seasonal variations in mixed layer O₂, with minor contributions from vertical entrainment and atmospheric exchange. While the influence of biological activity on O₂variability cannot be directly assessed, indirect evidence suggests relatively minor contributions, although with significant uncertainty. Past studies show that O₂molecules are expelled from sea ice during brine rejection; sea ice cover can then inhibit air‐sea gas exchange resulting in winter mixed layers that are super‐saturated. Decreasing mixed layer O₂concentrations and saturation levels are observed during winter months between 2007 and 2019 in the Canada Basin. Only a minor portion of the decreasing trend in wintertime O₂can be attributed to decreased solubility. This suggests the O₂decline may be linked to more efficient air‐sea exchange associated with increased open water areas in the winter sea ice pack that are not necessarily detectable via satellite observations.