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FROZEN HEAT
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Establishing the importance of methane from gas hydrates
in ongoing and future climate change remains a challenge.
Part of the challenge is the considerable uncertainty about
the total amount of methane involved, as well as the timing
and nature of gas hydrates’ response to future change (Kerr
2010). To establish quantifiable connections between gas hy-
drates, ongoing climate change, and future climate change,
four main questions must be answered:
How much warming will there be, and where?
Surface tem-
perature changes must be linked to global processes, such as
fluctuations in ocean circulation, sea level, and glacier mass
balance, in order to provide information about temperature
changes at the sea floor or in coastal permafrost regions. Pre-
dictive models of heat transfer through sediment can then be
applied to forecast the temperature evolution for the buried
gas hydrates themselves.
How much gas hydrate breakdown will result from that
warming?
Answering this question requires knowing the
spatial distribution and concentration of gas hydrates in rela-
tion to regions of enhanced warming, as well as verifying the
depth of hydrate occurrence in these locations to determine
whether a given surface temperature change will cause any
or all of the buried gas hydrates to break down.
How long will the warming take to destabilize those gas hy-
drates?
Heat transfer down through sediment can be slow.
The process is further slowed by the heat absorbed in thaw-
ing overlying permafrost or dissociating gas hydrates them-
selves. There can be delays of 3 000 years or more between
ground-surface or sea-floor warming and the ensuing gas
hydrate dissociation at depth (Ruppel 2011).
How much of the methane released from the destabilized gas
hydrates will be transferred to the atmosphere?
To increase at-
mospheric methane concentrations, methane liberated from
gas hydrates must migrate through the sediment and/or water
column without being consumed or dissolved. Consumption
rates are not well-constrained and vary by location.
3.3
KEY ISSUES FOR LINKING
GAS HYDRATE WITH CLIMATE CHANGE