Upper-ocean gas dynamics from radon profiles in the Eastern Tropical South Pacific

• Published in: Deep-sea research. Part I, Oceanographic research papers Oceanographic research papers, 2015-05, Vol.99, p.35-45
• Main Authors: Yeung, Laurence Y., Berelson, William M., Hammond, Douglas E., Prokopenko, Maria G., Wolfe, Christa, Rollins, Nick
• Format: Article
• Language: English
• Subjects: Biogeochemistry; Dynamics; Eddy diffusivity; Gas dynamics; Gas exchange; Gases; Geochemistry; Marine; Ocean biogeochemistry; Oceanography; Oceans; Parametrization; Radon; Radon deficit; Stations; Thermocline; Upwelling; Ventilation
• ISSN: 0967-0637; 1879-0119
• DOI: 10.1016/j.dsr.2015.01.008

Uncertainties in the dynamics of dissolved gases limit the accuracy of geochemical primary-productivity estimates. Mixed-layer ventilation, entrainment, and upwelling all affect the interpretation of geochemical data, yet they are rarely measured together. We report upper-ocean dissolved-gas dynamics in the Eastern Tropical South Pacific (10–20°S, 80–100°W) obtained from 222Rn distributions from a research cruise in February 2010. Radon-222-based surface ventilation measurements at seven stations were compared with gas transfer velocities calculated using empirical wind-speed parameterizations. Good agreement between the two methods was observed across different wind data products (ASCAT scatterometer and NCEP/NCAR meterological reanalysis) and grid scales (0.5°×0.5°, 1°×1°, and 2°×2°). Average wind speeds in the region were 5–8ms−1, corresponding to in situ gas transfer velocities of 1–3md−1. Averaged over the region, most recent gas exchange parameterizations performed similarly, and the results are robust with respect to both wind data products and grid scales. Non-steady-state conditions were observed at one station, possibly caused by a recent internal wave. These results suggest that 222Rn could be used to support measurements of biogeochemical O2 and CO2 fluxes in the upper ocean. •Upper-ocean radon depth profiles were measured in the Eastern Tropical South Pacific.•In situ radon-based estimates of gas exchange agree with wind speed parameterizations.•Recent (post-1992) wind speed-gas transfer parameterizations performed similarly.•Wind speed parameterizations showed little dependence on spatial grid size.•Radon data identified/characterized non-steady-state gas dynamics at one station.