One year of continuous measurements constraining methane emissions from the Baltic Sea to the atmosphere using a ship of opportunity.

Gülzow, W., Rehder, Gregor, Schneider von Deimling, Jens, Seifert, S. and Tóth, Z. (2013) One year of continuous measurements constraining methane emissions from the Baltic Sea to the atmosphere using a ship of opportunity. Open Access Biogeosciences (BG), 10 . pp. 81-99. DOI 10.5194/bg-10-81-2013.

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Abstract

Methane and carbon dioxide were measured with
an autonomous and continuous running system on a ferry line crossing the Baltic Sea on a 2–3 day interval from the Mecklenburg Bight to the Gulf of Finland in 2010. Surface methane saturations show great seasonal differences in shallow regions like the Mecklenburg Bight (103–507 %) compared to deeper regions like the Gotland Basin (96–161 %).
The influence of controlling parameters like temperature, wind, mixing depth and processes like upwelling, mixing of the water column and sedimentary methane emissions on methane oversaturation and emission to the atmosphere are investigated. Upwelling was found to influence methane surface concentrations in the area of Gotland significantly during
the summer period. In February 2010, an event of elevated methane concentrations in the surface water and water column of the Arkona Basin was observed, which could be linked to a wind-derived water level change as a potential
triggering mechanism. The Baltic Sea is a source of methane to the atmosphere throughout the year, with highest fluxes occurring during the winter season. Stratification was found
to promote the formation of a methane reservoir in deeper regions like Gulf of Finland or Bornholm Basin, which leads to long lasting elevated methane concentrations and enhanced
methane fluxes, when mixed to the surface during mixed layer deepening in autumn and winter. Methane concentrations and fluxes from shallow regions like the Mecklenburg
Bight are predominantly controlled by sedimentary production and consumption of methane, wind events and the change in temperature-dependent solubility of methane in the surface water. Methane fluxes vary significantly in shallow regions (e.g. Mecklenburg Bight) and regions with a temporal
stratification (e.g. Bornholm Basin, Gulf of Finland).
On the contrary, areas with a permanent stratification like the Gotland Basin show only small seasonal fluctuations in methane fluxes.

Document Type: Article
Keywords: Methane; Baltic Sea; emission; atmosphere; POSEIDON; POS392; Heincke; Alkor; AL06; Maria S. Merian; MSM16/1
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/bg-10-81-2013
ISSN: 1726-4170
Expeditions/Models/Experiments:
Date Deposited: 28 Nov 2012 14:11
Last Modified: 23 Sep 2015 10:35
URI: http://oceanrep.geomar.de/id/eprint/19356

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