Field Update: Nov. 2, 2010

After three weeks of training and preparing for the first ANDRILL traverse to Coulman High, we departed from McMurdo Station at 8:15 AM on Tuesday morning (November 2nd) in Pisten Bully (PB) 310, which was equipped with a 15 foot-long boom that could be lifted up off the ice with a cable and winch mounted on the front of the PB for turning in close spaces.

All of the riders in the vehicle had attended GPR training the previous week and we had gone on test drives around Ross Island on the Castle Rock Loop to test out the system and optimize the setup for the traverse.

We enclosed the front passenger seat with black plastic bags to lower the ambient light and thereby allow the operator of the GPR to see the computer screen. Claude Laird, a scientist from CReSIS was the primary operator of the GPR. He was assisted by our FSTP mountaineer, Susan Detweiler, who used her considerable talents with ropes and knots to rig up a “floating” table for the GPR hanging in front of the operator in the passenger seat of the PB. I was the driver, but I felt partially blind because the plastic bags hid the view on the right side of the vehicle, so I could only look to the left or straight ahead. We practiced navigating around town with Claude looking out from under the plastic bag to say “all clear” as we drove to get fuel and pick up our final supplies before leaving town.

In addition to myself as the driver of the PB and Claude and Suz as the GPR operators, we had Dar Gibson, who was coming along to operate the mobile hot water drill if we needed to mitigate any crevasses by drilling shot holes and using explosives (which thankfully we didn’t have to do). Dar was also going to “flag” our route while riding the ANDRILL skidoo – a journey of 60 miles from the Shear Zone to Coulman High (CH). With Dar and Suz riding in the back cab of the PB and Claude monitoring the radar we departed McMurdo and drove over the hill to Scott Base where we proceeded across the transition zone, paralleling the pressure ridges on our right, to head out onto the ice shelf on a northeasterly course. Next stop was the Shear Zone, which is the name given to a zone of ice that is highly crevassed located about 30 miles from McMurdo Station on the South Pole Traverse route, at the boundary between the McMurdo Ice Shelf and the Ross Ice Shelf to the east. Of the four of us, only Suz had been there before, so we were anxious to see what we would find and learn what lay beyond this known section of the route on our way to CH.

The speed of the PB while we were operating the GPR was limited to about 7 miles per hour in order to get the correct readings using the 400 MHz GPR antenna, which was mounted inside an inner tube strapped to the end of the boom to keep a constant orientation facing down and to cushion the antenna as we drove over the rough surface of the ice.

We had to drive around the airfield on our way past the Long Duration Balloon (LDB) site in order to encounter the flagged route heading past Black Island and continuing to the northeast of White Island on our way to the Shear Zone. The weather was somewhat overcast, but we were on our way and happy to be finally getting out in the field.

The 30 mile drive to the Shear Zone took about 5 hours, with the PB stopping every mile or so to download the GPR data file to a flash card and set up for the next segment. I fell into a routine of driving, hearing Claude call “STOP”, waiting a minute or two, and then hearing “GO” again and stepping on the accelerator. We were able to follow the flags along the route and waited to see what we would find when we got to the Shear Zone. We had talked to the people from the Cold Regions Research and Engineering Laboratory (CRREL) who had been surveying the Shear Zone along with the operators for the South Pole Traverse (SPT) and knew to look for a small container located just in front of the entry to the route across the Shear Zone.

There was a long line of red flags spread in front of us and we paused for a while on the perimeter to determine where we were supposed to go next.

After staring at the scene for a few minutes we determined that there was a single wooden post and then a long line of green flags heading off to the left, (northeast). The line of green flags had periodic wooden posts and black flags marking crevasses that had been located, probed, and then mitigated with explosives to collapse the ice bridges. These crevasses had been filled in to a safe depth (and width), which provided a route that we could use to drive across. We had been warned to stay close to the flags and not depart from the marked route and we were determined to follow this good advice.

We hadn’t seen any of the rest of the USAP (U.S. Antarctic Program) traverse team, which included four Case-International Harvester Quadtrack tractors pulling from 3 to 5 ANDRILL 20’-long containers each, as well as two Caterpillar Challenger tractors that were similarly loaded. They were following behind us, having started out a few hours after we departed due to their higher speed, but we thought we would have seen them before now.

We proceeded across, following the flags and reading some of the names written on each wooden post, such as “Mongo”, with each location measured from Grid A West (GAW) at the entrance to the zone. The route sloped down a gully and twisted back and forth until we came out the other side and reached the staging area where some of the ANDRILL containers had been brought across earlier in the week (on Friday). We were across the Shear Zone and one third of the way to our Coulman High destination!!

A few minutes later we heard a low rumble and then out of the mist and the snow came a line of tractors being led by Stephen Zellerhoff, the lead driver for the local traverse team accompanying us to Coulman High.

Steve was followed by the rest of his team, including Christie, Tom, Dean, Julian, and Wayne, who were driving their own tractors, which all came to a halt with containers and sledges in rows all around us.

We gathered together to welcome the rest of the team and began to make plans to set up the camp for the night before going the rest of the way to CH.

We determined that the best approach was for the PB to go out about 10-15 kilometers to see if there are any crevasses to the northeast using the GPR.

While the rest of the team circled the wagons, so to speak, we prepared to drive off into virgin territory to see what we would find, perhaps going a bit slower than we had gone up to that point. It was windy and overcast, but we set out and got back into the routine of stopping and going again as we saved the GPR files and used the global positioning system (GPS) to find the way.

We didn’t see anything of interest in the radar, so after about an hour we decided to turn back. We found ourselves low on fuel and had to use one of the Jerry cans mounted on the back of the PB to give us enough fuel to get back to camp. We calculated that the PB was using about 3 liters of diesel fuel for every mile that we drove – not very good fuel efficiency, but we’re able to cross some pretty inhospitable terrain without any problems.

We arrived back in camp to find some hot soup being cooked in the galley container, which was hooked up to a portable generator and was being heated, so all ten of us gathered inside for a meal and reflected on the first leg of our journey to Coulman High. It felt good to stop after seven hours in the PB and we were sure that sleep would find us in short order. We had passed the first test, crossing the Shear Zone and had the majority of our gear now staged and ready to go. The morning would come soon enough, so we crawled into the sleep modules and drifted off to sleep listening to the wind blowing past the containers, wondering what tomorrow would bring.

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