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Nitrous oxide water column distribution during the transition from anoxic to oxic conditions in the Baltic Sea
1Forschungsbereich Marine Biogeochemie, IFM-GEOMAR, Leibniz-Institut für Meereswissenschaften, Düsternbrooker Weg 20, 24 105 Kiel, Germany
2Leibniz-Institut f ¨ ur Ostseeforschung, Warnemünde, Germany
Abstract. In January 2003, a major inflow of cold and oxygen-rich North Sea Water in the Baltic Sea terminated an ongoing stagnation period in parts of the central Baltic Sea. In order to investigate the role of North Sea Water inflow to the Baltic Sea with regard to the production of nitrous oxide (N2O), we measured dissolved and atmospheric N2O at 26 stations in the southern and central Baltic Sea in October 2003.
At the time of our cruise, water renewal had proceeded to the eastern
Gotland Basin, whereas the western Gotland Basin was still unaffected by the
inflow. The deep water renewal was detectable in the distributions of
temperature, salinity, and oxygen concentrations as well as in the
distribution of the N2O concentrations: Shallow stations in the Kiel
Bight and Pomeranian Bight were well-ventilated with uniform N2O
concentrations near equilibrium throughout the water column. In contrast,
stations in the deep basins, such as the Bornholm and the Gotland Deep,
showed a clear stratification with deep water affected by North Sea Water.
Inflowing North Sea Water led to changed environmental conditions,
especially enhanced oxygen (O2) or declining hydrogen sulfide
(H2S) concentrations, thus, affecting the conditions for the production
of N2O. Pattern of N2O profiles and correlations with parameters
like oxygen and nitrate differed between the basins. The dominant production
pathway seems to be nitrification rather than denitrification.
No indications for advection of N2O by North Sea Water were found. A
rough budget revealed a significant surplus of in situ produced N2O
after the inflow. However, due to the permanent halocline, it can be assumed
that the formed N2O does not reach the atmosphere. Hydrographic aspects
therefore are decisive factors determining the final release of produced
N2O to the atmosphere.
Discussion Paper (PDF, 1997 KB) Interactive Discussion (Closed, 7 Comments) Final Revised Paper (BG)
Citation: Walter, S., Breitenbach, U., Bange, H. W., Nausch, G., and Wallace, D. W. R.: Nitrous oxide water column distribution during the transition from anoxic to oxic conditions in the Baltic Sea, Biogeosciences Discuss., 3, 729-764, 2006. Bibtex EndNote Reference Manager
