2:00 PM - 2:15 PM
[MIS21-07] Reaction/fixation/migration of methane within the gas chimney on the Umitaka Spur, eastern margin of the Japan Sea
Keywords:gas hydrate, methane flux, Japan Sea
The methane flux oxidized at the SMI was calculated to be >600 mmol/m2/yr using the SMI depth of <1 mbsf within the gas chimney. Assuming that the methane flux has been constant and all the methane has formed hydrates of 6×108 m3 within 200×250 m gas chimney in <363 ka (data from METI coring), the methane flux directly associated with hydrate was estimated to be >1500 mmol/m2/yr. The methane flux released into the water column was calculated to be <5 mmol/m2/yr using the methane concentration in bottom water of <1500 nM and bottom water current of <10 cm/s. These numbers are still tentative because sedimentation rate within gas chimney is rather variable among sites, gaseous methane in sediment must be accounted, a part of methane hydrate has dissolved during massive accumulation of hydrate body, etc. However, recent intensive researches on the shallow gas hydrate system have provided the better understanding of total methane behavior within the gas chimney.
This study was conducted partially under the commission from AIST as a part of the methane hydrate research project funded by METI (the Ministry of Economy, Trade and Industry, Japan).