FEASIBILITY OF ACOUSTIC WIDE AREA METHANE BUBBLE PLUME MAPPING IN THE ARCTIC OCEAN PERMAFROST

Emissions of methane, a greenhouse gas more potent than carbon dioxide, have roughly doubled over the last century [1] and become a major cause of global warming [2]. Methane hydrate under the wide subsea permafrost region in the Arctic sea is critically important because an excessive amount of methane gas can be released as the hydrate structure destabilizes [3]. Although several dense methane gas plumes were observed in this area [4], the wide areal distribution of these natural ocean methane seepages remain speculative. This is mainly due to the limitation of current sensing systems. The latest downward looking acoustic imaging technology [5] severely under-samples methane seepage distribution in both space and time because of the platform's sparse track and limited speed. Remotely Operated Vehicle (ROV) based optical imaging systems [6] are designed to monitor an individual methane seepage, and are thus not suitable for wide area surveys because of the severe light absorption underwater. Satellite [7] and ground network based sensing systems [8] measure the spatial distribution of atmospheric methane in global scale; however, these technologies are not capable of directly imaging underwater methane emission sources.