A decade of methane measurements at the Boknis Eck Time Series Station in Eckernförde Bay (southwestern Baltic Sea)

[摘要] Coastal areas contribute significantly to the emissions of methane ( CH 4 ) from the ocean. In order to decipher its temporal variability in the whole water column, dissolved CH 4 was measured on a monthly basis at the Boknis Eck Time Series Station (BE) located in Eckernförde Bay (SW Baltic Sea) from 2006 to 2017. BE has a water depth of about 28 m, and dissolved CH 4 was measured at six water depths ranging from 0 to 25 m. In general, CH 4 concentrations increased with depth, indicating a sedimentary release of CH 4 . Pronounced enhancement of the CH 4 concentrations in the bottom layer (15–25 m) was found during February, May–June and October. CH 4 was not correlated with Chlorophyll  a or O 2 over the measurement period. Unusually high CH 4 concentrations (of up to 696 nM) were sporadically observed in the upper layer (0–10 m; e.g., in November 2013 and December 2014) and coincided with major Baltic inflow (MBI) events. Surface CH 4 concentrations were always supersaturated throughout the monitoring period, indicating that Eckernförde Bay is an intense but highly variable source of atmospheric CH 4 . We did not detect significant temporal trends in CH 4 concentrations or emissions, despite ongoing environmental changes such as warming and deoxygenation in Eckernförde Bay. Overall, the CH 4 variability at BE is driven by a complex interplay of various biological and physical processes.

[学科分类] 大气科学