Modelling the benthic methane sink in Santa Barbara basin
Document typeMaster thesis
Rights accessOpen Access
The dissociation of gas hydrates has widely suggested to be a global climate forcing since millions of years ago. The “clathrate gun hypothesis” described by Kennett et al. (2003) in Santa Barbara Basin (SBB) suggests that past increases in ocean water temperatures near the seafloor may have induced to large-scale hydrate dissociation from marine reservoir. This methane release in enough proportion may contributing to the atmospheric warming that drove abrupt millennial-scale climate change. Recent researches and geological records suggest that climate change and ocean warm- ing could destabilise marine methane hydrate releasing large amounts methane from the seafloor to the ocean-atmosphere, further amplifying anthropologically driven global warm- ing and accelerating the destabilisation of remaining hydrates. SBB is characterized as the most prolific area of seepages of methane in the world, sed- iment records in the zone have documented brief, negative light carbon isotopic excursions in the late Quaternary in planktonic and benthic foraminifera interpreted as evidence of major releases of methane from the marine hydrate reservoir. All this multiple indicators warn of the possible presence of hydrates makes SBB an ideal place to study the possibility of future methane emissions due to the dissociation of hydrates. Even marine methane hydrate destabilise, migrating methane can be consumed by a number of biogeochemical processes occurring within the sediment column, specially Anaerobic Oxidation of Methane, which are expected to mitigate methane emissions to the water column. This work will consist of modelling methane efflux in SBB due to warming-induced hydrate destabilization, using an adaptive reaction-transport model, the Biogeochemical Reaction Network Simulator (BRNS). I intend to solve several some specific scientific questions as, how efficient is the AOM bio-filter when expose to different transient methane inputs from below and by using different formulations to express the rate of methane oxidation, and therefore how much methane escapes to the water column in its dissolved or gas phase. The model results shows that, even in the worst scenario, the efflux in the sediment- water interface derived from hypothetical gas hydrate dissociation in SBB sediment, is not important enough to consider it a major problem to the global warming, even more, knowing that the released methane must cross 590m of water column, where Aerobic Oxidation of Methane are expected to consume the remain methane.
DegreeMÀSTER UNIVERSITARI EN ENGINYERIA DEL TERRENY (Pla 2015)