From Source to Sea Surface: Untangling the Drivers of Oceanic N₂O Emissions

Ocean is among the major sources of nitrous oxide (N₂O) to the atmosphere which boosts global warming and ozone depletion. The Indian Ocean is a hotspot for N₂O emissions, but the relationship between N₂O production and emission, as well as how it may change in the future, remains uncertain. A recent study using advanced ocean biogeochemical modelling reveals that about three quarters of N₂O emitted to the atmosphere in the northern Indian Ocean is produced in the subsurface by either nitrification or denitrification and transported to the surface layer in regions of vigorous vertical exchange before its release to the atmosphere (see Figure). This study highlights the decoupling between N₂O production and emission. It calls for accurate constraints on environmental factors that influence N₂O production (e.g., oxygen level, primary production), but also on ocean circulation that governs N₂O release to the atmosphere. Understanding the response of both environmental factors and ocean circulation to climate change is essential to evaluate future changes in global ocean N₂O emissions and their potential feedback on climate change.

Reference: Zhao, Y., Resplandy, L., Wan, X. S., et al. (2025). Decoupling of N₂O production and emissions in the northern Indian Ocean. Global Biogeochem. Cycles, 39(4), e2024GB008481. https://doi.org/10.1029/2024GB008481