Ribas-Ribas, Mariana and Helleis, Frank and Rahlff, Janina and Wurl, Oliver (2018) Air-sea CO2-exchange in a large annular wind-wave tank and the effects of surfactants. Frontiers in Marine Science, 5. p. 457. ISSN 2296-7745

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Official URL: http://dx.doi.org/10.3389/fmars.2018.00457


Wind, chemical enhancement, phytoplankton activity, and surfactants are potential factors driving the air-sea gas exchange of carbon dioxide (CO2). We investigated their effects on the gas transfer velocity of CO2 in a large annular wind-wave tank filled with natural seawater from the North Atlantic Ocean. Experiments were run under 11 different wind speed conditions (ranging from1.5ms−1 to 22.8ms−1), and we increased the water pCO2 concentration twice by more than 950μatm for two of the seven experimental days. We develop a conceptual box model that incorporated the thermodynamics of the marine CO2 system. Surfactant concentrations in the sea surface microlayer (SML) ranged from 301 to 1015 μgL−1 (as Triton X-100 equivalents) with enrichments ranged from 1.0 to 5.7 in comparison to the samples from the underlying bulk water. With wind speeds up to 8.5 ms−1, surfactants in the SML can reduce the gas transfer velocity by 54%. Wind-wave tank experiments in combination with modeling are useful tools for obtaining a better understanding of the gas transfer velocities of CO2 across the air-sea boundary. The tank allowed for measuring the gas exchange velocity under extreme low and high wind speeds; in contrast, most previous parametrizations have fallen short becausemeasurements of gas exchange velocities in the field are challenging, especially at low wind conditions. High variability in the CO2 transfer velocities suggests that gas exchange is a complex process not solely controlled by wind forces, especially in low wind conditions.

Item Type: Article
Additional Information: Publiziert mit Hilfe des DFG-geförderten Open Access-Publikationsfonds der Carl von Ossietzky Universität Oldenburg.
Uncontrolled Keywords: sea-surface microlayer, gas exchange, gas transfer velocity, low wind speed, surfactants, chemical enhancement
Subjects: Science and mathematics > Life sciences, biology
Divisions: Faculty of Mathematics and Science > Institute for Chemistry and Biology of the Marine Environment (ICBM)
Date Deposited: 12 Sep 2019 11:39
Last Modified: 15 Oct 2019 08:00
URI: https://oops.uni-oldenburg.de/id/eprint/4167
URN: urn:nbn:de:gbv:715-oops-42488
DOI: doi:10.3389/fmars.2018.00457

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