Wednesday, October 25, 2006

Iceberg B-15

Science Time!

I went to a science lecture tonight and it was fascinating. I will do my best to recap it. Iceberg B-15 had collided with one the eastern end of Ross Island (McMurdo Station is on the south-west tip). This iceberg was so large that it interferred with the normal annual ice breakup and for five years or so, McMurdo sound did not clear out of ice. In fact, the pressure caused by the berg's pressence created large crevasses in the ice that emperor penguins could not pass through. For anyone who has seen March of the Penguins, (and everyone should see it) the penguins could not complete their march as they could not cross the large crevasses, could not get out of them once they were in, and could not find a way through the jumble of ice thrown up into large pressure ridges.

However, in the fall of 2004, the berg somehow dislodged itself, and was broken apart. The reason was unknown until a group of scientist began looking into it. They had a siesmometer on the berg and through the instruments measurements, they were able to determine that the breakup was due to wave impact vibrations. They were also able to determine the origin of the waves. Turned out it was more than 13,000 km away. With another station, relatively nearby, they determined that the waves originated, again, more than 13,000 km away. They plotted they made two circles from the stations at the appropriate distances and the circles crossed at two points. One in the Himalyan mountains (no waves start there) and the other in the Gulf of Alaska. They then checked out weather data for that time and found a storm with greater than 14 meter high waves at the center. Fascinating detective work. So the biggest iceberg in the world, B-15, was broken up by a storm in Alaska.

I have to get to bed now. On flagging duty tomorrow. We're flagging the route to the Ice Shelf runway which will be used when the currently used sea ice runway is no longer think enough to support the heavy C-17 airplanes. Goodnight!

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