Nitrous oxide (N₂O) is a potent greenhouse gas and an important contributor to global warming. The oceans are a major source of N₂O, yet global emission estimates remain highly uncertain due to limited observational data. In particular, the Indian Ocean is among the least studied regions with respect to N₂O cycling.
Here, we investigate N₂O dynamics in the equatorial Indian Ocean and Bay of Bengal (BoB) using water column depth profiles of N₂O, nutrients, oxygen, temperature and salinity collected during two cruises in 2024. Our results reveal pronounced spatial variability in N₂O distribution, including a distinct eastward increase in N₂O concentrations along the equator, accompanied by an enhanced N₂O production yield from nitrification. The highest N₂O concentrations were observed in the BoB, where both nitrification and denitrification contribute to N₂O production. In the BoB, sustained N₂O accumulation in subsurface waters is driven by the absence of an effective microbial sink and strong stratification that restricts sea-air exchange. This accumulated N₂O spreads laterally and contributes to elevated N₂O concentrations in deeper waters of the east equatorial Indian Ocean.

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