We went out onto the sea ice on Thursday for our safety training. It was the first time I’ve been very far out of the sheltering hills that surround McMurdo, and it demonstrated just how much I have to learn about staying warm in Antarctic conditions. Wearing two layers of thermal pants, two layers of thermal shirts, wind pants, two pairs of gloves (with a set of chemical handwarmers), and my “Big Red” Antarctic parka, I still got cold. In particular, it took just a few minutes to stop being able to feel my fingers; I had to borrow a pair of mittens to get them working again. I’m not sure what the temperature was, exactly, but the wind was well upwards of twenty miles an hour.
The lesson in sea ice safety was quite interesting, though. The basic goal of sea ice safety is, of course, to avoid falling through the sea ice into the 28F/-2C seawater below. Thus the procedure is more or less as follows (DISCLAIMER: I am not a professional sea ice safety trainer. Should you find yourself with occasion to drive over sea ice, please consult someone who knows what they’re doing, first!)
1. Look for cracks in the surface. These can be quite thin, or mostly covered with snow, but it’s usually possible to spot them if you stay alert.
2. Shovel the snow off of the sea ice in a channel extending a couple of feet from the crack. Note that there are several levels of sea ice in this particular crack. This happens because the sea ice that formed when the crack opened and re-froze hasn’t had a chance to get as thick as the older sea ice.
3. Drill some holes to check the ice thickness. The standard drill bit used for this is one meter long, so it doubles as a convenient measuring stick.
4. The ice must be at least 30″ thick to be considered safe. The edges of this crack are too far apart to drive over, and the central ice is too thin to drive on, so in this case we’ll have to find another place to cross.
If the crack is narrow enough, however–less than 1/3 of your tread length–then you can just drive over it.
(That’s my artistic rendering of a Pisten Bully.) As of Saturday morning, I know how to drive one. WHEE!)