There is significant research activity within the UK concerning methane hydrates and the contemporary methane cycle. NERC funded a three-year Methane Network to build on this activity by increasing collaboration between research groups and also with relevant Living With Environmental Change (LWEC) and industry partners.
Background & objectives
The Earth system contains a multitude of interacting processes, which leads to the potential for abrupt changes with potentially severe impacts for human-wellbeing.
The potential destabilisation of the vast methane hydrates reservoirs as a tipping point for global climate change is a specific challenge. Methane hydrates are also of interest to the energy industry as a potential energy reservoir and as a hazard during drilling. These hydrate reservoirs (methane/water ice-like structures) are only stable within a specific temperature and pressure range, and hence increases in temperature (due to global warming) or decreases in pressure (eg submarine landslides) clearly have the potential to destabilise these reservoirs, leading to large scale methane release.
Methane is currently the second most important greenhouse gas after carbon dioxide (CO2), with a much higher global warming potential than CO2, hence an increase in methane release rates can lead to warming, further destabilisation of methane and hence to further warming: a positive feedback cycle. There is evidence that a process like this occurred in the past.
Predictions of the future risk of methane hydrates' destabilisation are uncertain because of a lack of fundamental understanding of their distribution, magnitude and stability. There are major methane hydrate reservoirs in the deep ocean, which are thought to be relatively stable to climate change, and in permafrost where they are potentially unstable, although probably on a rather long time scale. There are smaller (but still substantial) methane hydrate reservoirs in shelf systems that are potentially the most unstable in the face of likely climate change. In some cases it is predicted that if destabilised, the methane will migrate upward and then re-stabilise within the sediments or remain in place, although thermodynamically unstable.
There are a further range of important issues relating to methane in addition to those of methane hydrates. It is the second most important greenhouse gas and levels have increased in the industrial era, but its rate of increase decreased considerably in the 1990s for reasons that are not understood. In part this reflects quite intense cycling and oxidation of methane within sediments and the water column so that methane release to the atmosphere is a small component of a larger cycle. Globally wetlands are a large, uncertain and climate sensitive source, and change in wetlands may have played a role in driving glacial-interglacial methane concentrations and climate change, but the mechanisms and impacts of the various complex interactions between temperature and water supply in this process are not understood.
Understanding the methane cycle is also important because of its role as an hydroxyl radical sink in the atmosphere, which in turn influences ozone cycling and raises issues about the long term trends in atmospheric oxidising capacity. Ozone is a greenhouse gas and also influences human, animal and plant health.
The outputs of this network should be of direct relevance to LWEC partners in assisting with policy options for the management of greenhouse gases. The outcomes of this better coordinated activity should lead to some exciting new scientific insights into the contemporary, paleo and future global methane cycle and encourage the participants to consider the issues within a long-term and large-scale Earth system science perspective.
Reports & key findings
The Methane Network report below has details of its work.