Arctic amplification–driven warming of Atlantic inflow intensifies oxygen loss across the Arctic Ocean

Dissolved oxygen is a key indicator of ocean health and is being altered by climate-driven warming. The Arctic–subarctic system is warming at an exceptional pace due to Arctic amplification, but how this rapid warming translates into basin-wide oxygen change is still not well constrained. Using observations of Atlantic Water (AW) pathways, we find that the Atlantic inflow exerts a leading control on recent deoxygenation in the Arctic Ocean. Oxygen declines are detected in the upper eastern Arctic and in the intermediate layers of the western Arctic at rates of −0.41 ± 0.17 to −0.47 ± 0.07 μmol kg−1 yr−1, approximately six times the global mean. We identify amplified warming in Arctic gateway regions as the dominant driver, primarily through a strong reduction in oxygen solubility. The resulting low-oxygen signal is then propagated into the interior Arctic by rapid subduction and circulation of AW, extending the impact to deeper layers and increasing risks to Arctic marine ecosystems. These results emphasize that warming Atlantic inflow is central to shaping Arctic oxygen dynamics; continued temperature rise is therefore expected to sustain and potentially strengthen ongoing deoxygenation, calling for heightened attention and broader monitoring across the Arctic.