Gas bubble emissions at continental margins: Detection, mapping, and quantification

The significance of gas bubble emissions at deep-water hydrocarbon seeps on the global carbon cycle is poorly constrained. Methane is, however, an important component regarding past and future climate change scenarios. One of the main motivations of this study was to obtain a better understanding of the sources and transport pathways of gas bubbles in order to evaluate their input to the atmospheric methane inventory. Three areas were investigated, which are located in different geological settings. Gas emissions were found in all three areas, indicating that this is a common phenomenon at different types of hydrocarbon seeps also in deep-water environments. The case studies show that the gas bubble emissions represent an effective pathway to transport methane into the water column. The fate of the gas bubbles while rising through the water column is strongly influenced by hydrate formation around the bubbles. Nevertheless, it was generally observed that the emitted gas bubbles ultimately remain in the ocean interior and thus do not contribute to the atmospheric methane inventory