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A GLOBAL OUTLOOK ON METHANE GAS HYDRATES
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Even in response to present-day warming rates, the vast ma-
jority of the world’s gas hydrates will not contribute methane
to the atmosphere over the next century (Archer, 2007). The
roughly 3.5 per cent of the world’s gas hydrates existing at the
feather-edge of stability on the upper continental slope could
break down over the next 100 years, but the released methane
would likely be consumed in the sediment or water column
before entering the atmosphere. Only the approximately 0.25
per cent of the world’s gas hydrates located in flooded perma-
frost environments (Ruppel, 2011), which have been subjected
to warming over the past 7 000 to 15 000 years, are likely to re-
lease, or are releasing, methane that can reach the atmosphere.
Because a significant increase in atmospheric methane con-
centrations can result from transferring even a very small
fraction of the methane in gas hydrates to the atmosphere,
quantifying the climatic impact of gas hydrate breakdown
will require reducing substantial uncertainties in estimates
of methane transfer to the atmosphere. Three key research
goals are:
1. Constrain the gas hydrate volumes that currently exist in
the most sensitive environments through in situ sampling,
remote sensing and modelling;
2. Establish water-column methane-consumption rates to
constrain estimates of how much methane from gas hy-
drates could transfer directly to the atmosphere. Since
water-column methane oxidation consumes oxygen as well
as methane, quantifying methane oxidation rates is also
necessary for establishing the biologic repercussions of re-
duced oxygen levels in marine systems; and,
3. Identify or fingerprint methane entering the atmosphere
from gas hydrates in order to distinguish gas hydrates
from other active methane sources. The release rates and
the volume scales of methane from the decomposition of
organic material or from deeper hydrocarbon reservoirs
can be quite different from the methane-release patterns
associated with gas hydrates.
So far, contemporary anthropogenic climate change does
not appear to have triggered significant gas hydrate disso-
ciation. However, the potential climate and environmental
impact of even a limited dissociation of the world’s gas hy-
drates continues to fuel multidisciplinary research in this
area (see Text Boxes 3.1 and 3.2). In addition to the climatic
impact of methane release to the atmosphere, methane re-
lease can affect other aspects of the environment. Methane
oxidation within the ocean contributes to ocean acidification
and will also affect the budget of dissolved oxygen, carbon
dioxide, and other compounds in the ocean (as discussed in
Volume 1, Chapter 2).
3.7
CONCLUSIONS