Heidelberg 2006 – scientific programme
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UP: Umweltphysik
UP 9: Poster: Hydrosph
äre
UP 9.2: Poster
Tuesday, March 14, 2006, 14:00–16:00, C
Gas Exchange Measurements: The Chemically Enhanced Gas Transfer of Carbon Dioxide at the Water Surface. — •Kai Armin Degreif1, Joachim Kuss2, and Bernd Jähne1 — 1Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Im Neuenheimer Feld 368, D-69120 Heidelberg — 2Institut für Ostseeforschung, Seestrasse 15, D-18119 Warnemünde
The exchange of carbon dioxide between the atmosphere and the ocean is a fundamental problem in earth sciences. Despite the fact that hydrodynamics at the free water surface is poorly understood, CO2 exchange is complicated by chemical reaction of the dissolved CO2 with bicarbonate and carbonate ions present in the ocean. At low turbulence intensity at the water surface the concentration gradients can significantly be influenced by chemical reactions leading to enhanced gas transfer.
Laboratory experiments were performed using the “controlled-leakage”-technique permitting measurements of the gas transfer rates at the water surface with a temporal resolution of a few minutes. For a sensitive measurement of the chemical enhancement simultaneous gas exchange measurements were performed with CO2 and N2O.
The effect of the chemically enhanced gas transport was demonstrated under a variety of chemical and physical conditions. The experimental results are in agreement with a simple theoretical model. For clean water surfaces chemically enhanced transport occurs only at low wind speeds. If wind-waves are damped by the presence of a surfactant, chemical enhancement can be observed at wind speeds up to 6 m/s in the annular experimental facility.