# Moving the South Pole

A. S. Whitt, Dec. 26, 1993

Well, it's Boxing Day here at South Pole Station. It's also Sunday so the ASA staff has the day off, and we're fending for ourselves on the food front.

The weather has been utterly beautiful. Yesterday was -25 F but still not bad for short walks. Today there's some breeze, and it's amazing how much colder that makes it feel!

At 2:00 this afternoon the official South Pole was placed in its carefully calculated spot.

Cathleen McDermott and Dale Benson of the USGS (United States Geological Service) brought the pole with them on the plane trip to the Pole. The geographical marker on the pole moves about 9.91 meters per year with the flowing ice. They used two methods to find the new spot.

One is called the Shadow Tip Method. If you stand where the pole is and look, you can see the straight line of poles stretching off toward the distance. The Shadow Tip method involves putting a tripod on top of the old marker and sticking an eight foot rod vertically on the tripod.

Of course all directions at the South Pole are technically "north". For that reason we have to define another type of north, called "grid north," which points along the longitude line called the Prime Meridian. If you were to follow this line of longitude north eventually you would reach Greenwich, England. Other directions at the South Pole are then defined with respect to grid north and are expressed as angles of azimuth. Zero degrees azimuth is in the direction of grid north. Other azimuths angles are then described as west(turning to the left) or east(turning to the right) of grid north. For example, if you faced exactly grid north and then put your left hand straight out to your side it would be pointing to ninety degrees west azimuth.

When the sun gets to azimuth 40 degrees west of grid north, it is lined up with the other markers, and the tip of the shadow of the eight foot pole marks where the new pole should go. (The first of these pole markers was places with the sun at that azimuth.) And an eight foot rod is used on top of a six foot tripod, because together they cast a shadow that is the right length for the rate that the ice is moving each year. At this time of the year the Sun is near its maximum elevation of 23.5 degrees. This method is approximate, but is an easy way to find where the pole should be based upon what we know about the direction and rate of the flow of the ice.

The other method used the Global Positioning system (GPS). A satellite network was used to determine the exact spot where 90 degrees south latitude is on planet Earth. The GPS reading is a few inches off from the shadow-tip reading, so that there is an official South Pole at the shadow tip and a little pipe at the GPS spot.

The South Pole marker is about twelve feet long, but about two-thirds gets pounded into the ground (ice). There were about 30 - 35 people out in the blowing snow (the sky clouded over at about 10:30 this morning, the temperature was -9 F, wind chill -46 F: colder than yesterday!)

Dale explained how the position of the pole was determined. He said that it has been 350 days since the last pole was placed (Jan. 8 of this year). Cathy put the pole on the spot and Dave Fischer got to take the first whack at pounding it in, with the special neon orange mallet.

Then each of us got to take a turn pounding it in. Tom Devine (sled pilot extraordinaire and electrical technician) took my picture, since I had forgotten the camera, and don't know how accurate it is anyway.

The pole has a decorative plaque on top, which was protected from our pounding by some bubble wrap and a small block of wood held on with rubber bands.

After everyone had had their picture taken pounding on the pole, somebody finished pounding it in the rest of the way, and the protective wood was removed. The plaque has a little dome on it that looks like the station dome. When I have time, and the wind dies down, I will go look more carefully at the others.

It was lots of fun, but the wind was so cold we went back in for hot chocolate right away. And the REAL POLE is set for another year.