Methane gas emissions of the Black Sea—mapping from the Crimean continental margin to the Kerch Peninsula slope.

This study focuses on gas bubble emissions across ~ 1800 km2 of the southeastern continental slope of the Crimean Peninsula in the Eastern Black Sea basin. In total, about 3500 gas emissions were mapped as so-called flares in single- and multibeam echosounder imaginary. Flares generally emanate from the seafloor, with a few exceptions, where water depths are less than 700 m, which represents the upper limit of the gas hydrate stability zone in this region. Methane in shallow sediments below 700 m is transferred to methane hydrate, and the migration of free gas into the water column is therefore inhibited in most cases. This study illustrates further that flare occurrence is linked to morpho-structural margin characteristics. Two morphologically different margin segments are distinguished, and flare distributions were found to relate to differing morphological structures along these segments. In the western province, where the upper continental margin is steep and incised by gullies, flares occur mainly along downslope-oriented ridge crests. In the eastern province, representing a part of the Don-Kuban paleo-fan, the slope is influenced by extensive mass wasting. Gas emissions in this area were mainly detected aligned along scarps of submarine landslides and related to sediment failures. Almost all flares disappear in the acoustic records of the water column below a water depth of ~ 100 m suggesting that the gas bubbles dissolve within the water body of the Black Sea and contribute to its methane inventory and the anoxic water column. [ABSTRACT FROM AUTHOR]