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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.