Abrupt climate change is defined as a large-scale change in the climate system that takes place over a few decades or less, persists (or is anticipated to persist) for at least a few decades, and causes substantial disruptions in human and natural systems.
Examples of components susceptible to such abrupt change are clathrate methane release, tropical and boreal forest dieback, disappearance of summer sea ice in the Arctic Ocean, long-term drought and monsoonal circulation.
Deposits of methane clathrates below the sea floor are susceptible to destabilization via ocean warming.
Anthropogenic warming will very likely lead to enhanced methane emissions from both terrestrial and
oceanic clathrates.
Extracts from:
- Intergovenmental Panel on Climate Change (IPCC), AR5 Workgroup 1, Technical Summary
What can cause Abrupt Climate Change?
Warming caused by people's emissions can trigger abrupt destabilization of clathrates and of methane held in the form of free gas in sediments. This can occcur in a number of ways that can combine to cause catastrophic developments:
- Global warming heats up the oceans, and heat can penetrate sediments through cracks and fractures, as well as through conduits formed by earlier methane releases; when sufficient heat reaches a clathrate, this will trigger methane release; in the process, methane expands some 160 times in volume, which can trigger further destabilization of the hydrate.
- Even where methane rising up through the sediment does not enter the atmosphere, it can expand the conduit, making it easier for subsequent methane to rise further and faster; year by year, clathrates can thus become more prone to cause large releases to enter the atmosphere.
- As terrestrial snow and ice cover melts, weight is taken off the land as the meltwater runs off. The weight difference can contribute to the occurence of earthquakes and landslides. Even where such events take place far away from the location of clathrates, tremors and shockwaves can travel over long distances, especially when earthquakes occur at greater depth.
- As the weight is lifted from land, as described above, isostatic rebound can occur that can suck up methane from clathrates held in melting permafrost.
Related posts
For more background, see posts at the Arctic-news blog and the methane-hydrates blog, such as:
- Methane release caused by earthquakes
http://arctic-news.blogspot.com/2013/09/methane-release-caused-by-earthquakes.html
- Abrupt Climate Change
http://arctic-news.blogspot.com/2013/10/abrupt-climate-change.html
