FROZEN HEAT | Volume 1

3.7 CONCLUSIONS

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).

A GLOBAL OUTLOOK ON METHANE GAS HYDRATES 71