14 December, 2002

Radar

Date: 12/14/02

Latitude: 83 degrees, 30 min., 2.81 seconds South Longitude: 104 degrees 59 min., 12.73 seconds West Temperature:-27 C / -17 F

Wind speed: 30 knots

Wind Chill: -46 C/ -50 F

Wind direction: Northeast

Meters of ice collected: 203 m

By Brian Welch

The storm that started during the last 30 kilometers of yesterday's traverse is still with us today with slightly stronger winds and colder temperatures. It makes for cold conditions for the ice coring crew, atmospheric chemistry and glaciology research as well as for the mechanics doing routine maintenance on the tractors. For those of us who ran the radar systems during yesterday's traverse it's an opportunity to back up our collected data onto CD-ROMs and to do some preliminary data processing.

There are three radar systems on the traverse that operate at all times while we're traveling. Two are high-frequency systems, one to look for crevasses and another to collect near-surface data to correlate with the ice cores.

The third radar system is in the last sleds of the traverse. This is a deep-penetrating radar system run by Brian Welch. This system uses a lower radio frequency (3 MHz) to penetrate as much as 3 km of ice to the bedrock below. The system also records internal ice layers caused by volcanic deposits or changes in the ice properties such as the transition between the last glacial period and the current interglacial period. As with the shallow radar these internal layers represent isochrones, lines of constant age, in the ice sheet. The deep radar can't recover data in the upper 100 m of ice so it can't be used with the shallow ITASE cores, but it will be useful for future deep drilling efforts in West Antarctica and provides some of the first measurements of ice thickness in this region.

Being the operator of the deep radar during one of the traverse legs is an experience quite different from the rest of the ITASE crew. The system consists of two sleds: the first is 75 m behind the last sled of the second train and contains the radar receiver, essentially and amplifier, oscilloscope, and computer; the second is another 135 m behind the receiver and contains the radar transmitter and its battery. The entire system is a little longer than two football fields.

The receiver shelter is an insulated plywood box that is 6.5 ft long, 5 ft wide, and 5 ft tall. It has a small shelf for the computer, a chair on one side, and space for my sleeping bag along one wall. This is where I live during the traverse. There are three small windows that provide views of the ice (when they're not covered with frost) as well as small vents for air circulation. The door out the back of the shelter opens onto a small platform that contains the generator that powers the system.

Because the sled is so small and on such a long rope the ride can get somewhat interesting. If the snow is soft the sled can bottom out and actually stop until the rope is stretched to its full length before snapping forward. It's something like a horizontal bungee-jump experience except that it happens every 20 seconds for 20 to 30 hours! If the terrain is hard and rough the sled bounces around and I spend much of my time catching items that are falling off the shelf (pens, notebooks, the car batteries that are being charged to keep the transmitter running).

The long traverses are the most difficult as I need to stay awake for the entire trip (sometimes as long as 50 hours) in order to monitor the radar system. The rough terrain can break an antenna, the generator needs gasoline at regular intervals, the transmitter batteries need to be charged and swapped every few hours, or there may be a change in the appearance of the bedrock or ice layers that should be recorded in my notes. A few other team members have helped out when possible, but many have experienced motion sickness I can't imagine why! For some reason I can't explain I don't seem to feel the same ill effects even though I can't stand things like roller coasters. Despite the rough ride I find that after 20-30 hours of a traverse leg I will occasionally doze off in my seat without realizing it. When this happens I'm usually jolted awake by falling out of my seat as we go over a bump or when my forehead hits the computer shelf.

In the end, when we're back home looking at the data all of the rough conditions and cold weather don't seem quite so bad. While we're here in the field it's a tiring job and it's hard to get excited about each long traverse leg. For the moment I'm resting up and planning to put some foam padding on the edge of the computer shelf I'm getting a bit of a lump on my forehead!