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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-165
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-165
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 23 May 2019

Submitted as: research article | 23 May 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Biogeosciences (BG).

A multi-year observation of nitrous oxide at the Boknis Eck Time-Series Station in the Eckernförde Bay (southwestern Baltic Sea)

Xiao Ma1, Sinikka T. Lennartz1,a, and Hermann W. Bange1 Xiao Ma et al.
  • 1GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
  • anow at: ICBM, University of Oldenburg, Oldenburg, Germany

Abstract. Nitrous oxide (N2O) is a potent greenhouse gas and it is involved in stratospheric ozone depletion. Its oceanic production is mainly influenced by dissolved nutrient and oxygen (O2) concentrations in the water column. Here we examined the seasonal and annual variations of dissolved N2O at the Boknis Eck (BE) Time-Series Station located in Eckernförde Bay (southwestern Baltic Sea). Monthly measurements of N2O started in July 2005. We found a pronounced seasonal pattern for N2O with high concentrations (supersaturations) in winter/early spring and low concentrations (undersaturations) in autumn when hypoxic/anoxic conditions prevail. Unusually low N2O concentrations were observed during October 2016–April 2017, which was presumably a result of prolonged anoxia and the subsequent nutrient deficiency. Unusually high N2O concentrations were found in November 2017 and this event was linked to the occurrence of upwelling which interrupted N2O consumption via denitrification and potentially promoted ammonium oxidation (nitrification) at the oxic/anoxic interface. Nutrient concentrations (such as nitrate, nitrite and phosphate) at BE are decreasing since 1980s, but oxygen concentrations in the water column are still decreasing. Our results indicate a close coupling of N2O anomalies to O2 concentration, nutrients and stratification. Given the long-term trends of declining nutrient and oxygen concentrations at BE, a decrease in N2O concentration, and thus emissions, seems likely due to an increasing number of events with low N2O concentrations.

Xiao Ma et al.
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Status: final response (author comments only)
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Xiao Ma et al.
Xiao Ma et al.
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Short summary
Monthly measurements of nitrous oxide (N2O), a potent greenhouse gas and ozone depletion agent, were conducted at Boknis Eck (BE), a time-series station in southwestern Baltic Sea, since July 2005. Low N2O concentrations were observed in autumn and high in winter/early spring. Dissolved nutrients and oxygen played important roles in N2O distribution. Although we did not observe a significant N2O trend, a decrease in N2O concentration and emission seems likely in future.
Monthly measurements of nitrous oxide (N2O), a potent greenhouse gas and ozone depletion agent,...
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