Coastal Upwelling Enhances Winter Arctic Ocean Methane Emission

As sea ice becomes thinner and more fragile, it may affect the Arctic Ocean methane budgets in winter. Using satellite, in situ and reanalysis data, the oceanic emissions of methane over the Chukchi Sea coast from 2003 to 2023 are investigated. In total, 196 methane ventilation days were recorded, contributing to atmospheric methane increases by 15.7 ppb d⁻¹. Methane ventilation is dominated by sea ice opening and is greatly enhanced by coastal upwelling-induced mixing. The methane concentration increases by 5.5[3.3, 7.8] ppb d⁻¹ with every 10% decrease in ice concentration. The average contribution of upwelling is 0.84[−1.1, 2.7] ppb d⁻¹, with the greatest contribution from warm Atlantic Water (AW). One such AW event can lead to an increase of methane up to 10[−2, 22] ppb. With further ice retreat, upwelling-induced oceanic methane emissions may occur widely and should be fully considered.