Thursday, April 27, 2006

Actually getting out on a glacier! `

Well, it wasn't the Kongsvagen, which is my principle objective in Svalbard, but today we actually got out on a glacier and made some measurements. Since the Kongsvagen is proving so difficult to get to, today we decided to take the neutron probe up to Midre Lovenbreen, a glacier very near Ny-Alesund. Since the route was on the north side of the mountains, it was far less slushy and we were able to get up on the glacier with little trouble. We went all the way up the glacier right near the head, in the accumulation area. The weather was beautiful, as was the view!

We started by making some radar measurements, then drilled a shallow borehole and set up the neutron logging system.

The neutron logging system, up and running on Midre Levenbreen!

The neutrom probe measures snow and ice density. It contains a radioactive source of fast neutrons and a detector for slow neutrons. The fast neutrons emitted form the source shoot out into the snow, and scatter off the water in the snow. In the process, they slow down, and, having been scattered several times, end up back at the detector. The rate of slow neutrons arriving at the detector is thus proportional to the density of the snow.

Since the emission of neutrons is a random process, data needs to be collected for a long time in order to get a statistically significant sample and get quality data. So, the neutron probe runs very slowly up the borehole- about 5cm every minute. Here's a little math exercise- what's that in miles per hour? well, I'll jsut tell you. It's 2x10^-3, sometimes written as 0.002, miles per hour. How slow is that really? When I first started the winch for the log, I was worried I'd broken something because I thought it wasn't moving. It's that slow.

In any case, slow or not, by the end of the day we had 2 density profiles. It's sure nice to have some success!


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