[ESAC Seminar] Timur Cinay

“Marine nitrous oxide outgassing as an El Niño wanes”

Nitrous oxide (N2O) is a long-lived, potent greenhouse gas with a large effective radiative forcing and is a dominant ozone-depleting substance in the stratosphere. Since the first synthesis of a global N2O budget in the initial Intergovernmental Panel on Climate Change report, the net marine efflux has been uncertain, and estimates have varied widely. Marine emissions of N2O are additionally thought to be strongly modulated by the El Niño Southern Oscillation. Yet, the timing and magnitude of emissions from low-oxygen hotspots, such as the Eastern Tropical South Pacific (ETSP), remain poorly constrained due to sparse historical sampling. We use Bayesian inverse modeling to estimate regional marine efflux during and after the strong 2023–2024 El Niño. By assimilating new continuous atmospheric N2O observations in the Galapagos, we find peak El Niño conditions suppress ETSP emissions by one-third to one-half relative to the historical average. As the El Niño subsided, an enhancement in N2O effluxes and surface concentrations emerged, driven by upwelling of subsurface waters enriched in N2O accumulated during El Niño, revealing a novel two-stage emissions pattern. Low effluxes during peak El Niño, followed by a pulse as the event relaxes, may partially offset the typically suppressed N2O emissions associated with El Niño, offering a new perspective on N2O dynamics in oxygen minimum zones. These measurements provide the first direct observational quantification of El Niño’s impact on N2O outgassing from the ETSP and highlight the value of combining high-frequency atmospheric observations with inverse modeling to refine estimates of marine N2O effluxes.

ESAC Early-Career Seminar Series —

A forum for students and postdocs to share recent research, hone presentation skills, and build community among peers, sponsored by the EAPS Student Advisory Committee. Open to current EAPS graduate and undergraduate students and postdocs. Typically hosted on Thursdays during the semester, including pizza lunch.

Contact: esac.officers@gmail.com