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Mike Leahy's Diary

Day 22: Speed and Melt of Glacier

Calculating the speed of the glacier Kathy, J and I are going to go up the glacier. This time, rather than walking, we will be taken in a helicopter. Our aim is to work out how far the glacier moves in one day. At first this sounds easy, but it most definitely is not. The glacier, like a river, is likely to move fastest in the middle so we plan to measure its speed there. But where can we measure it from? The rest of the glacier is moving. There are no fixed points like trees close to the glacier, and even the rocks can move so we will have to make our own reference points. In theory we may be able to stretch a wire across the glacier, make a mark below it in the ice and return next day to see how far the ice has moved beneath the wire. However simple this sounds, the glacier is too big, too rugged and there is no way that we could fix and tension the wire. I consider cheating, and using my new GPS, but it isn't accurate enough, and anyway it finds locating satellites very difficult from the Franz Glacier Valley. The only real option is to take a lesson from nature:

Mike, Jonathan and Kathy building toolsWe judge distances all the time by using our eyes. If we had one eye it would be very difficult to work out distances unless we used perspective (the fact that distant objects look smaller than less distant objects). This is very difficult (try touching something randomly with your finger using only one eye to guide it, or riding your bike through a narrow gap, again with only one eye - don't cheat by looking at it with two eyes first because your brain will guide your finger by memory). We find picking up tea cups (or beer glasses) easy. It's second nature because we use both eyes to judge distances. This works because the view from each eye is slightly different. Using the different views (different angles) our brain works out how far away an object might be regardless of size. The same principle can be used to determine the position of random objects mathematically. If we use two observation points a known distance apart, but positioned away from the glacial ice on solid ground, we can calculate the position of a stake driven into the ice in the centre of the glacier. Each observation point represents one of our eyes but our brains will need some help in the form of either an accurate scale model, trig calculations (triangulation) or both. We decide to drive a stake into the glacier and measure the angle to the stake from each end of a baseline. If we take the first measurements tomorrow (day 2) and repeat them (day 3) we should be able to work out how far the glacier has moved. That's the theory, but in the meantime we need tools.

MikeI'm no carpenter, and unlike Jonathan the tools I make are rough and ready. Even so, by the end of the day we have two tripods which can support the huge protractors that J plans to build (based on the principle that larger scales lead to improved accuracy). We also have to work on hand warmers and I set about making an ice lens. This isn't as easy at it sounds, because all the gases dissolved in the water have to be removed. I do this by boiling some water for a few minutes. It is then placed in an air-tight bottle. I plan to use an enamel dish in which water can be frozen on the glacier at night. Kathy has a cool idea. A lens can be made by putting water in a balloon with a springy ring in it. Once the water has frozen, the balloon can be peeled off, revealing a lens shaped piece of ice. J is making the protractors. They look cool.

I'm still having trouble with woodwork and start thinking. Ellen gets all the biology because she is a botanist. It's a shame that I get none; after all I have a degree in biology and environmental biology as well as my DPhil in Virology. Virology is biology too. Sometimes people forget that. On the other hand I have never been trained in carpentry. I do know how to use the tools, which is one up on some of the others though.

We leave the sawmill at about six, have a meeting at the Glacier Guiding Company at six thirty, and then have to get back to the huts for seven ready for evening filming. It's a cool job but the hours are long. Sometimes it's hard to find time for a shower, let alone to phone home.

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Photo: Mike Leahy
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