Climate change is a decidedly complex process, with many processes involved directly affecting others, often enhancing each other. For example, the warming of the oceans drives the release of methane, a powerful greenhouse gas, from its frozen, submerged prisons. And now, by following bubbles of released gas, new research from the University of Washington has managed to directly track this phenomenon.
As described in Geochemistry, Geophysics, Geosystems, out of 168 bubble plumes observed off the coast of Washington and Oregon in the past 10 years, a disproportionate number of them were seen at the depths frozen methane – methane hydrate – is known to be stored.
“We see an unusually high number of bubble plumes at the depth where methane hydrate would decompose if seawater has warmed," said lead author H. Paul Johnson, a UW professor of oceanography, in a statement. "So it is not likely to be just emitted from the sediments; this appears to be coming from the decomposition of methane that has been frozen for thousands of years.”
Methane clathrates, also known as methane hydrates, are spectacularly dangerous stores of methane, one of the three most potent greenhouse gases. Greenhouse gases, with regards to their warming potential, are ranked by climatologists by both their ability to keep heat within the Earth’s atmosphere and by the time they typically spend there. Although methane doesn’t spend as long in the atmosphere as carbon dioxide, while it is there, it is able to trap far more thermal radiation in the Earth’s atmosphere, making it a significant hazard in the medium-term.
Methane as a gas is emitted by both man-made and natural processes all the time, but a large volume of the gas is stored as clathrates beneath great expanses of snow in tundra climates and beneath the world’s oceans. These clathrates are kept from the climate by a cap of permafrost or a low temperature marine environment, respectively. As humans continuously pump inordinate amounts of carbon dioxide into the atmosphere, the world warms; simultaneously, some of these carbon emissions dissolve in water, forming carbonic acid. The warming atmosphere is already melting the permafrost caps on the clathrates, threatening to unleash them into the air. In addition, the warming and increasingly acidic oceanic waters is causing a dangerous leak of methane into the environment, as this study demonstrably shows.
If the storage regions of these vast preserves of icy methane are significantly destabilized, the resulting global warming effect could be profound, and perhaps irreversible. If enough methane is released, and global temperatures rapidly rise, the oceans will become warmer and more acidic, the permafrost will melt faster, and more and more methane will be unleashed. This is known as the clathrate gun hypothesis – in that once the “gun” has been fired, the runaway process cannot be stopped.
There have been potential historical examples of this, most notably the Paleocene-Eocene Thermal Maximum (PETM), a sudden and catastrophic warming event that occurred 56 million years ago and lasted for approximately 170,000 years. The world’s temperature increased by 5-8°C (9 to 15°F) in just 20,000 years. Although several causes have been cited, it seems likely that a massive release of destabilized oceanic methane clathrates was to blame.