Ice and Medicine at the end of the earth

33. Why do you have to work on the ice core in a freezer when it’s already below freezing?

That’s a question I’ve asked myself more than once, Dyneon.  Who goes outside to the middle of the Antarctic ice sheet to warm up?

The reason we work in a freezer is to keep the quality of the ice core high.  We try to keep the ice core close to the average temperature, which is -30 C.  But the summer temperature is closer to -10 C so we have to work in a freezer.

The colder the temperature that the ice is kept at, the less the gases in the air bubbles and the isotopes in the ice diffuse.  What is diffusion? Well, think about spraying some air freshener in a room.  At first, the smell is very intense where you sprayed it, but across the room, you can’t smell anything.  But after a minute or so, the smell is pretty equal no matter where you are in the room.  A similar process happens in the ice, and diffusion happens faster at higher temperatures (the higher temperature means there is more energy to speed the process of diffusion along).

The reason we drill an ice core is look at how climate (for instance temperature and carbon dioxide concentration) have varied in the past.  If lots of diffusion occurred in the ice core, then the gases and isotopes would become the same along the ice core – just like the air freshener in the room. So to slow diffusion and lock those variations in place, we keep the ice very cold.

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