Testing Snow Strength
Two expeditions and thousands of miles on the Greenland ice sheet have provided valuable information to CH2M HILL Polar Services logisticians and engineers as they work to optimize an overland traverse to access NEEM and Summit stations by ground instead of air. During the most recent traverse (completed this spring), the traverse team tested the snow strength along the way, collecting data that will help the team understand why the Greenland Inland Traverse (GrIT) is not achieving the same performance from the traverse equipment that traverse teams in Antarctica do, said Allen Cornelison, GrIT manager for Polar Field Services (a partner in Ch2M HILL Polar Services).
“The tests will also help us to understand what aspects of our equipment we need to improve to get better performance out of our tractors and the sleds,” Cornelison said.
Lightening the Load, Reducing Resistance
In addition, this year’s traverse team tested sled and load configurations that improved towing performance. Specifically, they discovered that longer sleds—as opposed to wider ones—pull better. The extra length allows the snow/sled interface to warm up slightly more to create a thin film of water, reducing friction and resulting in less pulling resistance.
“This is a huge ordeal (pulling resistance) we are trying to overcome,” said Cornelison. “The [Antarctic traverse] can pull more than we can—by 25 percent. This is because the Greenlandic ice sheet gets a lot more snow, and that snow is stratified and not as solid and ‘work hardened’ (by the wind and time) as the snow in Antarctica.”
To overcome this problem, the GrIT either needs to invest in expensive larger tractors, haul lighter loads (which would be inefficient), or figure out how to get the lowest pulling forces with the highest weighted loads.
New Sleds Improve Towing
This year the team also used a product called Durabase as a cargo sled to haul solid equipment The Durabase replaced the HMW plastic fuel bladder sleds used in 2008 that “tacoed” when the cargo traps were tightened. This contributed to towing problems and the team determined the fuel bladder sleds are too compliant for solid cargo.
However, the Durabase “worked out really well in that it is made of HMW plastic, so it is slippery, but it is also semi-rigid,” said Cornelison.
“This rigidity allowed us to secure hard items to the Durabase nicely,” he said. “But the challenge with the Durabase is that it is quite heavy, and we are constantly trying to reduce weight and make sleds more slippery.”
Advantages of a Traverse
CH2M HILL Polar Services (CPS) has completed two traverses, and anticipates integrating an overland traverse into annual operations. Traveling by ground can save money and result in fewer emissions and can complement air deliveries to the remote stations CPS supports.
The team has identified the ideal route for the traverse, though the first 70 miles may alter each year depending on where crevasses open, said Cornelison. And, given the melt rate of the ice sheet, the route may require reevaluation at some point “if our ice ramp turns into mountains and canyons,” Cornelison said.
To prepare for future traverses, PFS has purchased three new tractors and will haul more fuel and cargo in spring 2011 to NEEM and Summit. The team is also working with the Cold Regions Research and Engineering Laboratory (CRREL) on concept air cargo sleds that will be provided to the Antarctic traverse to test this year.
“Looking to the future, I see the traverse supporting many more operations on the Greenland ice sheet,” said Cornelison. “I am guessing as well that science groups will recognize a benefit to the new route and road that has opened up the ice sheet. I wouldn’t be surprised, for example, to see more drilling camps, more environmental, and more glacial research happening in the future once we get the GrIT more established and mitigate some of our challenges.” —Rachel Walker
The Greenland Inland Traverse is funded by the National Science Foundation (NSF). CH2M HILL Polar Services and Cold Regions Research and Engineering Laboratories are working together with the NSF to develop the traverse infrastructure and route. For more field notes coverage of GrIT, click here.GrIT contact: Allen Cornelison, Polar Field Services, CH2M HILL Polar Services GrIT project manager allen at polarfield.com