Deep Sea Bottom Methane Hydrate Investigations Aboard Fisheries Training Ship

Abstract

Since 2013, we have been investigating the presence of methane hydrate in the sea bottom of the Joetsu Basin at depth of 560-580 m via observations mainly taken aboard the fisheries training ship “Nagasaka-maru” which is operated by Nagasaki University. The four cruises were conducted around the middle of May, during the years 2014-2017. The “Nagasaki-maru” and the crew have excellent skills for the usage of the quantitative echo sounder, for fixing the ship's position relative to the sea bottom and for dredging and core sampling. During our cruises, we observed methane plume echoes at precise seafloor locations using the echo sounder and obtained methane hydrate core samples from the seafloor. In 12th of May 2018, following the retirement of the third ship of that name, we conducted our fifth observation cruise aboard the newly commissioned “Nagasaki-maru”, which was launched in October 2017, and have obtained even more detailed information from our targeted methane hydrate areas.