The dataset comprises high-resolution (1-min) measurements of dissolved nitrous oxide in surface waters of the Eastern Tropical Indian Ocean. The observations were conducted during the expedition SO-304 on board R/V SONNE (February-April 2024). Seawater was drawn on board by means of a submersible pump installed at 6 m depth, and measurements of equilibrated headspace were carried out as described in Arévalo-Martínez et al. (2013): https://doi.org/10.5194/os-9-1071-2013.

OA-ICOS Analyzer coupled to shower head equilibrator as in Arévalo-Martínez et al. (2013): https://doi.org/10.5194/os-9-1071-2013. Equilibration temperature measured with a FLUKE 1524 reference thermometer (+/-0.01°C). Sea surface temperature (SST) and salinity derived from discrete in-situ measurements with a Seabird SBE45 (Temperature: +/-0.002°C; Conductivity: ± 0.0003 S/m). The gaps in SST caused by logger malfunction were filled based on the linear correlation with equilibration temperature (sst=1.0202*equ_temp - 4,408).Atmospheric mixing ratio obtained by adding the monthly mean at Mahe Island-Seychelles Station (Latitude: 4.6824° South, Longitude: 55.5325° East, Elevation: 2.00 masl) for February 2023, to the annual increase in atmospheric N2O mixing ratio (xn2o_atm=337.104 nmol/mol + 1.12 nmol/mol). Data was obtained from NOAA's Atmospheric Cooperative Sampling Network (upon usage, citation should be: Lan, X., J.W. Mund, A.M. Crotwell, K.W. Thoning, E. Moglia, M. Madronich, K. Baugh, G. Petron, M.J. Crotwell, D. Neff, S. Wolter, T. Mefford and S. DeVogel (2024), Atmospheric Nitrous Oxide Dry Air Mole Fractions from the NOAA GML Carbon Cycle Cooperative Global Air Sampling Network, 1997-2023, Version: 2024-07-30, https://doi.org/10.15138/53g1-x417). Partial pressures and concentrations of N2O in the atmosphere were estimated as explained in Arévalo-Martínez et al. (2013): https://doi.org/10.5194/os-9-1071-2013 and references therein.