Browsing by Author "Honkanen, Martti"

Carbon dioxide is a key compound both in climate change and marine biological productivity. In the oceans, the sea-air exchange of carbon dioxide is driven by large-scale currents and changes in solubility, whereas in coastal seas, such as the Baltic Sea, biological activity has a significant effect on the aquatic carbonate system. However, direct measurements of the sea-air exchange of carbon dioxide are difficult to carry out due to the small magnitude of the fluxes, waves, sea ice and sea spray that influence sensitive instruments. Eddy covariance method is a widely used direct method for measuring the fluxes of carbon dioxide. The sea-air fluxes of carbon dioxide are also commonly calculated using a parametrization based on wind speed. Finnish Marine Institute in collaboration with Finnish Environment Institute began to construct a new atmospheric and marine research station on Utö in the Archipelago Sea in 2012. The objective of this study is to determine the suitability of the new station to measure air-sea exchange of carbon dioxide and aquatic carbonate system. The air-sea fluxes of carbon dioxide were measured with three infrared gas analyzer set-ups during October-December 2016, and the fluxes were also calculated using a parametrization of gas transfer velocity. The aquatic carbonate system of the surface water during July-October 2016 was studied using dissolved carbon dioxide concentration and pH of the seawater measured in a flow-through pumping system. The dissolved carbon dioxide concentration was measured by using an equilibration chamber together with an infrared gas analyzer. The micrometeorological tower erected on the shore can be applied for measuring the sea-air fluxes of carbon dioxide in an open sea wind sector, which was determined based on the roughness length. The closed-path infrared gas analyzer (Licor LI-7000) works well in the hard coastal conditions, whereas an open-path analyzer (Licor LI-7500) had difficulties in measuring fluxes during showers and high relative humidity. The Pearson correlation coefficient between the fluxes measured with two closed-path gas analyzer set-ups was 0.91. The flux calculated using a parametrization of gas transfer velocity showed only a small correlation with the measured flux, with a Pearson correlation coefficient of 0.13. The flow-through pumping system can be used to calculate the components of the aquatic inorganic carbonate system. The measured pH was linked to the dissolved carbon dioxide concentration of the sea water. Additionally, it was discovered that the LI-7000 is sensitive to changes in instrument temperature.