Influence of onshore-offshore surfactant gradients on air-sea gas exchange
Zusammenfassung der Projektergebnisse
A spatio-temporal data set of the transfer velocity in seawater samples of the coastal North Sea, together with measurements of surfactant activity (SA), coloured dissolved organic matter (CDOM), and fluorescence of the surface microlayer (SML) and underlying water (ULW), shows that the SA significantly affects the transfer velocity. Observed changes in kw during the seasonal cycle are up to 70 % and stress the significance of surface-active organic matter for air–sea gas transfer. Although the data have scatter, an exponential relation between SA and kw could be fitted. Data for low SA < 0.2 mg l−1 T-X-100 are also compatible with a linear decrease, similar to the trend in the ∆σ to k660 relation reported by Schmidt and Schneider (2011). The time series measurements which were started within this project will be continued for the foreseeable future in order to acquire a high-quality data set with multiple seasonal cycles. This will be a crucial step towards understanding the influence of surfactants on air–sea gas exchange within the natural system. In order to gain a better understanding of the important substances of natural surface films and their respective concentrations, a “model SML” with the most abundant substances measured in natural SML was compiled. With this model, the natural suppression of kw could be reproduced. Measurements of this model SML in a large circular wind-wave facility, the Aeolotron, investigated the effect of nature-identical surface films under natural conditions with wind-induced turbulence.
Projektbezogene Publikationen (Auswahl)
- Comparison of storage strategies of sea surface microlayer samples. Biogeosciences, 10(7):4927–4936, 2013
Schneider-Zapp, K., Salter, M. E., Mann, P. J., and Upstill-Goddard, R. C. Technical Note
(Siehe online unter https://doi.org/10.5194/bg-10-4927-2013) - An automated gas exchange tank for determining gas transfer velocities in natural seawater samples. Ocean Science, Vol. 10.2014, issue 4, pp. 587-600.
Schneider-Zapp K., Salter M. E., and Upstill-Goddard, R. C.:
(Siehe online unter https://doi.org/10.5194/os-10-587-2014) - Surfactant control of gas transfer velocity along an offshore coastal transect: results from a laboratory gas exchange tank.
Biogeosciences, Vol. 13. 2016, Issue 13, pp. 3981-3989.
R. Pereira, K. Schneider-Zapp, R.C. Upstill-Goddard
(Siehe online unter https://doi.org/10.5194/bg-13-3981-2016)
