Hey look at this ice cube.
Wait.
What?
This “ice” is actually methane hydrate -- a combination of water and methane.
It’s the methane that burns as the water melts away.
And depending on who you ask, it’s a huge potential source of natural gas, a serious
risk to our climate, or ya know both.
Usually, methane just bubbles through water.
It doesn’t dissolve much.
But under the enormous pressure and in the cold temperatures of the ocean, something
weird happens: this forms.
Here’s a methane hydrate on the molecular level: OK so these red dots are all oxygen
atoms in water molecules.
We hid the hydrogens cuz otherwise it gets to be too crazy.
And this may look like a disordered mess, but eventually, as your eyes adjust, you’ll
see these cage-like arrangements of water molecules.
And of course like any cage, there’s a space in the middle, and those spaces are where
methane molecules can get trapped.
Two things can keep this cage stable: high enough pressure from other molecules pushing
in on the cage, or temperatures low enough that the molecules don’t fly apart due to
their normal vibrations and gyrations.
If the pressure is high enough, methane hydrates can even be stable at room temperature.
Most of the methane in methane hydrates comes from deep-sea bacteria which give it off as
waste, and the ocean supplies the water.
And most methane hydrate is buried in sediment around the edges of the continents.
Now - There’s a lot of ocean, there’s a lot of bacteria in the ocean, so there are
gigatons of methane hydrates.
And one cubic meter of the stuff, when it melts, releases up to 180 cubic meters of
methane gas.
So if all of THIS melted tomorrow, we’d end up with THIS MUCH methane.
This is kind of a big range but it’s at least 3800 times the amount of methane the
US burned in all of 2016.
If it’s really cold, like in the Arctic, methane hydrates can actually form outside
of the ocean, under the Arctic permafrost.
In fact, some of the undersea methane hydrate deposits around the arctic ocean formed on
land and then got covered with ocean when sea levels rose at the end of the last ice
age.
All of this methane sitting around is pretty tempting, given our voracious appetite for
fossil fuels.
Some countries, especially Japan, are exploring ways to extract the methane and burn it for
energy.
But of course there are some risks.
Burning methane releases less CO2 than other fossil fuels, so it’s seen as cleaner, but
look, you’re still burning a fossil fuel here.
And, a while back some researchers were concerned that warming temperatures could destabilize
methane hydrates and release methane into the atmosphere -- very quickly.
That would be... not good, because methane is a far more potent greenhouse gas than carbon
dioxide -- but for more on that, check out THIS video.
Scientists now think though that, all except the shallowest methane hydrates seem pretty
stable, and most of the methane released from the seafloor would probably be eaten by oceanic
bacteria before it reached the surface.
So an extreme doomsday scenario where a bunch of undersea methane is unleashed doesn’t
seem very likely.
The most vulnerable hydrates would actually be the ones that are on land, locked up in
Arctic permafrost that could one day thaw.
Fossil fuel friend or climate change foe, burning ice is still pretty freakin’ cool.
Huge thanks to the US Geological Survey for helping us out with this video and letting
us use their methane hydrate footage.
By the way, it’s earth week, and we’re celebrating -- check out acs.org/ccew for
more.
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