tatjna (tatjna) wrote,
tatjna
tatjna

Hardcore

WTF is this thing?




No really, it more or less is. It's an ice core, obtained by drilling into the ice sheet over some frozen wasteland - most often Greenland or Antarctica. Well, first they dig a giant trench by hand to put the drilling equipment in, then they drill for a really long time, till they get to ice that was laid down a seriously long time ago. Like, that one above? 120,000 year old ice in that one, and it was 1855m under the surface. It's from Greenland.

As you can imagine, the ice that's that far down is pretty squished but even so, you can see bands in it. Each of those represents a year. Seriously. The light stuff is where summer melts occurred and the dark stuff shows winter ice. Thus, you can get pretty accurate dating from these things - in fact today's lecturer used to work with snow, and apparently you can find out stuff about the weather last month from digging that up.

So anyway, what they do is they test these things for the presence of various chemicals, but the most interesting ones from the perspective of climate change and global warming are the stable isotopes - these being standard atoms of the same element that have 'extra' neutrons. O18 is the one they are interested in as a component of water. Y'see, these 'extra' neutrons on the oxygen atom make 'heavy' water when part of a molecule, which has a lower vapour pressure than for the standard molecules of water, meaning that precipitation in very low temperatures (low pressure) is mainly made up of 'light' water molecules.

So when they look at the cores, they look at the ratio of 'heavy' to 'light' isotopes. Low ratios mean colder weather, high ones mean warmer weather. Thus they have a good idea of what the temperature was 120,000 years ago (and the time in between) in Greenland, and it's pretty accurate to the year.

Neat, eh?

The fun thing about the Greenland ones is that they demonstrate that at the end of the last ice age there was a short spell of warming in which the temperature increased by 12°C in three years. Just sit for a minute and imagine what that'd be like where you live. Anyway, after that it got colder again for a bit and then it increased again, this time over 60 years. Still pretty fast, eh? Ice cores taken in Antarctica have confirmed this, and also that it usually happens there first and then the north follows shortly after.

So it's been demonstrated that the climate can change really fast when certain threshholds are reached. Unfortunately, nobody's figured out what the threshholds are made up of - but it's certain that temperature and amount of atmospheric CO2 are tied together (which makes continuing to pump carbon into the atmosphere a bad plan), that climate change can happen very abruptly, and that what's happening in Antarctica is an indicator for what's likely to happen in the rest of the world, temperature wise.

So what's happening in Antarctica? Like everywhere else, it's getting warmer. Unlike everywhere else except the Arctic circle, bits of it are falling off. In the last 30ish years, 8 Antarctic ice sheets have collapsed (that's 14,000 square kilometres of ice). Western Antarctica is losing ice at a rate of 10 Gigatonnes per year - that's a fuck of a lot of ice. They're kind of worried about this, not just as an indicator of warming (which is kind of no shit sherlock because all measures say the same thing), but because they think the ice sheets are what stops the glaciers in Antarctica from pouring ice into the oceans even faster by acting as a sort of buffer. If Antarctica starts losing ice faster, we have a problem. If Antarctica loses 1% of its ice, we get 0.7m of sea level rise globally. I don't want to think about what 10% looks like but it doesn't take a mental giant to figure it out, eh?


So, um, about those carbon emissions then. We're making a poster*, what are you doing?

*The poster is about green tech and its possibilities and limitations, and will apparently be displayed at a public panel discussion on the 27th of January about which I can find nothing online. Anyway, did you know there's a guy feeding dairy effluent to whitebait? Weird, but kind of cool.

Tomorrow we're off on a field trip! I've never been on a field trip before. We are going to GNS to look at actual ice cores and be overwhelmed by the boffins being all nerdy about their machines, apparently. Can't wait. ;-)
Tags: antarctica is cool, ice, study
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