Fire and Ice -- The Risk
Fire from ice. Intriguing. What do we know about this strange strange substance that goes by the name methane clathrate? Wikipedia tells us:
Methane clathrate, also called methane hydrate or methane ice, is a form of water ice that contains a large amount of methane within its crystal structure (a clathrate hydrate). Originally thought to occur only in the outer regions of the solar system where temperatures are low and water ice is common, extremely large deposits of methane clathrate have been found under sediments on the ocean floors of Earth.
"Extremely large deposits?" So is that, like, good news or bad? Not surprisingly, it can be either, depending on who you ask. Let's talk about the bad news first. As shown in the picture, this ice can catch fire and burn or, like regular ice, it can simply warm up and melt. When methane clathrate burns, it's the methane that 's burning. From an environmental standpoint, burning the stuff is not so bad. Burning methane does release some CO2 (a greenhouse gas) into the atmosphere, but quite a bit less than any other fossil fuel. On the other hand, if you melt methane clathrate rather than burning it, you release methane gas itself into the atmosphere. Methane is also a greenhouse gas, but it's about 20 times as efficient as CO2 at heating up the atmosphere.
In other words, if you want global warming, methane will get you there a lot faster than CO2 emissions. (Not to disparage CO2 in this regard; it can be highly effective.
So, what happens if these "extremely large deposits" of methane clathrate frozen on the ocean floor begin to melt? There are two possible answers:
- Potentially cataclysmic change in climate
The first scenario represents the normal course of things. Methane clathrate melts all the time, usually in small quantities that bubble up towards the ocean's surface. Before the bubbles can reach the surface, the methane is re-dissolved into the ocean where it benignly floats around until (presumably) it freezes back into clathrate.
The second scenario is obviously more dramatic; indirect evidence potentially supporting such a scenario has only recently been confirmed to occur.
Remarkable and unexpected support for this idea occurred when divers and scientists from UC Santa Barbara observed and videotaped a massive blowout of methane from the ocean floor. It happened in an area of gas and oil seepage coming out of small volcanoes in the ocean floor of the Santa Barbara channel -- called Shane Seep -- near an area known as the Coal Oil Point seep field. The blowout sounded like a freight train, according to the divers.
Aside from underwater measurements, a nearby meteorological station measured the methane "cloud" that emerged as being approximately 5,000 cubic feet, or equal to the volume of the entire first floor of a two-bedroom house. The research team also had a small plane in place, flown by the California Department of Conservation, shooting video of the event from the air.
[Marine Science Institute researcher Ira] Leifer explained that when this type of blowout event occurs, virtually all the gas from the seeps escapes into the atmosphere, unlike the emission of small bubbles from the ocean floor, which partially, or mostly, dissolve in the ocean water.
Large quantities of methane suddenly released into the atmosphere could have quite an impact on global climate. Granted, we would need to be talking about a much larger quantity of the gas than was observed in this particular blow-out, but there could be bigger blowouts or more of them could occur, or the methane might come from sources other than volcanic, leading us back to our fire-ice:
Over geologic time scales, global climate has cycled between warmer, interglacial periods and cooler, glacial periods. Many aspects of the forces underlying these dramatic changes remain unknown. Looking at past changes is highly relevant to understanding future climate changes, particularly given the large increase in atmospheric greenhouse gas concentrations in the atmosphere due to historically recent human activities such as burning fossil fuels.
One hypothesis, called the "Clathrate Gun" hypothesis, developed by James Kennett, professor of geological sciences at UCSB, proposes that past shifts from glacial to interglacial periods were caused by a massive decomposition of the marine methane hydrate deposits.
So if our planet is currently warmer than normal either because of human acitivty or because of where we happen to be in the climate cycle or through some unholy combination of those two factors, this would seem to be a particularly bad time for any massive decomposition of methane clathrate to occur. Unfortunately, the warmer the planet gets, the greater the risk may become.
Sounds pretty scary, potentially. It would seem that we're sitting on a time bomb. Or maybe there's another way of looking at it...