11 September, 2009

Ted And The Arctic Slushie Machine

If you don't think the Earth is warming, then you might use this article to argue that it's all about small cycles causing panic, because the glaciers are slowing down again.  You'd use that article to claim that for every warming/panic-inducing cycle that the panic merchants are using to stop you making a healthy billion dollars from exploiting freely available resources.

I'm all in favour of perhaps not being quite so hasty.  I'm all in favour of panicking - right now - because of a few things I observed as a child, as a student, and as an adult.  That is, that things happen in cycles, yes - but those cycles are often self-reinforcing and accelerating.

Ice is a strange material, and if it weren't for the decidedly strange properties of water and ice, life on Earth would have been much more difficult, if not impossible.  Quick recap of basic school science:  All materials on Earth have properties that go a bit like this:
  • Solid state is the coldest state of the material, it is at its most dense (atoms packed closest together) and the particles are generally locked together and do not move much relative to one another.
  • Liquid state is reached as the material is warmed up, and the particles have limited movement relative to one another, allowing the material to flow.
  • Gaseous state is reached if the material is heated even further, and at this point the particles move freely about.
Water doesn't quite work like that.  In its solid state it is less dense than in its liquid state, which is why icebergs float. And that property is one of the freaks of nature that we can blame life on...

Imagine a world where water behaved like all the other materials.  During the night, in a cold spot, the ice would form - and then sink to the bottom of the water, where the sun can't warm it up again.  Normal thermal circulation would ensure that the warmer water would stay on top, and cold liquid water would sink to lite above the ice.  The following night, a bit more water freezes and plunges to the depths, never to be seen again...  You can see that in a very short time, only about an inch of liquid water would be accessible and all else would be ice.

That's in part why life as we know it (and as we're stuck with, it's worth noting) was able to evolve.

Now we come to some observations made as a kid, when defrosting the fridge was one of my duties.  I sometimes used pans of warm water to heat up the freezer box, and one of the things I saw was that water and ice do behave cyclically.  The heat would create a film of water between the ice and the freezer floor, and the ice would start to flow.  Then, as the ice moved and melted, cold water ran down into the gap between ice and freezer, it would slow down a bit, then the heat would build up and there would be another flow, followed by another slowdown.

That cycle would repeat, but the bottom line was that eventually, every time, the ice layer would break up and fall out like a sheet of slushie...  I know this model doesn't take into account that I've turned the source of cold off, but it's still very close to what is observed.  We're turning the fridge to a defrost cycle and letting the slowly warming ocean currents and warmer air slush the polar ice.

In that article, the researchers say that warmer water flows upstream between the glaciers and the ground at times.  If the water is warmer than normal, I would imagine that initially there would be a much faster movement of the glacier ice, until enough cold ice and water had been brought down to counter the effects of the warmer water.  Then the process would obviously slow down again, until the warmer water flows back up under the ice sheets and the temperature of the water layer starts to rise again.

To me the thing isn't that the glaciers are slowing down a bit, because I'd expect that.  To me, the question is - how soon will the warmer layer win again? - And is this the time that the ice drops off in one big line of Arctic slushie? - Or are there a few oscillations left in the system?


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