Methane fluxes in the southeastern Baltic Sea |
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| Authors: | Marina Ulyanova Vadim Sivkov Timur Kanapatskij Pavel Sigalevich Nikolay Pimenov |
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| Institution: | 1. P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Atlantic Branch, 236022, Prospect Mira 1, Kaliningrad, Russia
2. Winogradsky Institute of Microbiology, Russian Academy of Sciences, 117312, Prospect 60-letiya Oktyabrya 7/2, Moscow, Russia
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| Abstract: | New data from surveys of gas-bearing mud areas in the Gdansk Deep (southeastern Baltic Sea) were collected during four research cruises in 2009–2011. These revealed the presence of seven large pockmarks apart from the three already known, and enabled significant improvement of the existing digital map of gassy mud distribution. Based on geochemical sediment analyses, calculated diffusive methane fluxes from the upper (0–5?cm) seabed layer into near-bottom waters were highest—3.3?mmol/(m2?day)—in pockmark mud, contrasting strongly with the minimum value of 0.004?mmol/(m2?day) observed in typical, background mud. However, fluxes of less than 0.1?mmol/(m2?day) were observed in all sediment types, including pockmarks. In a newer attempt to roughly estimate budgets at a more regional scale, diffusive methane venting amounts to 280?×?106?mmol/day for southeastern Baltic Sea muddy sediments. Elongated pockforms in the southern Gotland Deep, known since the end of the 1980s as pockmarks, had methane concentrations that were similar to those of gassy mud from the Gdansk Basin, and there was no geo-acoustic evidence of considerably increased gas levels. |
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