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.
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