Carbon microcycle: CO2 gradients in the ocean surface (CµC)
Final Report Abstract
The carbonate system has a pivotal role in marine biogeochemical cycles. It is central to the exchange of CO2 between the ocean and atmosphere, and determines its impact on atmospheric and oceanic processes, e.g. the extent of ocean acidification. However, research of the carbonate system has ignored the upper 5 m of the ocean’s water column, including the sea-surface microlayer i.e. the uppermost top of the oceans. This is because interferences from research vessels and rosette samplers do not allow sampling of this zone without disturbing its integrity. I investigated the carbonate system and pCO2 gradients in the surface ocean (upper 5 meters), and how they are driven by biological and physical processes. I focused on the microlayer, which is in direct contact with the atmosphere, and hypothesize that partial pressures of CO2 in the microlayer determine “real” air-sea fluxes, i.e. compared to fluxes based on data from 5 meter or below. I adapted a state-of the-art research catamaran to measure parameters of the carbonate system in situ in the surface ocean and in the microlayer at high resolution. In controlled tank experiments, I assessed uncertainties of established sampling techniques for measurements of gases in the microlayer. With the modified catamaran and an autonomous floating chamber measuring in situ CO2 fluxes, I participated in an expedition to the South Pacific to collect field data and to investigate the formation of near-surface pCO2 gradients. With data at high resolutions, I am able to provide a mechanistic understanding on the formation of surface gradients and determine the main underlying environmental forces: mainly thermal effects and chemical enhancements. Results have provided air-sea CO2 fluxes based on near-surface aqueous pCO2 values, and biases by computing fluxes from ship-based data at depths of 5 meter. Overall, this project will support future assessment of global air-sea fluxes of climate-relevant gases. The scientific surprises were to identify some very well defined gradients on the inorganic carbonate chemistry in the near surface ocean.
Publications
- 2020. Global reduction of in situ CO2 transfer velocity by natural surfactants in the sea-surface microlayer. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 476, 20190763
Mustaffa, N.I.H., Ribas-Ribas, M., Banko-Kubis, H.M., Wurl, O.
(See online at https://doi.org/10.1098/rspa.2019.0763) - 2020. The MILAN Campaign: Studying Diel Light Effects on the Air–Sea Interface. Bulletin of the American Meteorological Society, 101, E146-E166
Stolle, C., Ribas-Ribas, M., Badewien, T.H., Barnes, J., Carpenter, L.J., Chance, R., Damgaard, L.R., Quesada, A.M.D., Engel, A., Frka, S., Galgani, L., Gašparović, B., Gerriets, M., Mustaffa, N.I.H., Herrmann, H., Kallajoki, L., Pereira, R., Radach, F., Revsbech, N.P., Rickard, P., Saint, A., Salter, M., Striebel, M., Triesch, N., Uher, G., Upstill-Goddard, R.C., Pinxteren, M.v., Zäncker, B., Zieger, P., Wurl, O.
(See online at https://doi.org/10.1175/BAMS-D-17-0329.1) - 2021. Effects of Natural and Artificial Surfactants on Diffusive Boundary Dynamics and Oxygen Exchanges across the Air–Water Interface. Oceans, 2, 752-771
Adenaya, A., Haack, M., Stolle, C., Wurl, O., Ribas-Ribas, M.
(See online at https://doi.org/10.3390/oceans2040043) - 2021. Technologies for observing the near sea surface. In E.S. Kappel, S.K. Juniper, S. Seeyave, E. Smith, M. Visbeck (Eds.), Frontiers in Ocean Observing: Documenting Ecosystems, Understanding Environmental Changes, Forecasting Hazards, Vol. 34 (pp. 88-89): A Supplement to Oceanography
Ribas-Ribas, M., Zappa, C.J., Wurl, O.
(See online at https://doi.org/10.7916/p52v-m162)
