Twin Otter Flies in Greenland

News

By Nick Mott
Summer 2011

A team of scientists and engineers stuck in an isolated, snowed-in hotel in remote Greenland. Their eyes are glued to their computer screens and they are fervently trying to analyze something. It sounds like the plot of a science fiction horror film – John Carpenter’s The Thing on the other end of the world. But on their March 15 to May 6 expedition to Greenland, the Twin Otter team was all science, no fiction.

“We were trying to determine the thickness of the ice in several of Greenland’s fastest flowing glaciers,” said Logan Smith, a graduate student in charge of on-site data processing during the mission.

Operating out of Ilulissat, Kulusuk, and Nuuk, the CReSIS team, led by Fernando Rodriguez-Morales, flew lines targeting Jakobshavn Fjord, the Helheim and South East Glaciers, and the Nuuk Glacier. On board the Twin Otter, CReSIS engineers utilized the MCoRDS ground-penetrating radar, an accumulation radar, and the Ku-band altimeter.

Greenland

Ilulisat, Greenland. Photo courtesy of Logan Smith.

“These are the most significant outlet glaciers, which are the main tributaries for getting ice from the interior of Greenland to the calving front, or out to the edges where it breaks off and eventually leads to a rise in sea level,” Smith said.

Rodriguez-Morales said that Jakobshavn, one of the fastest-moving glaciers in the world, has long been a focal point of scientific interest. The CReSIS team completed a number of radar improvements to better accomplish the tricky task of accurately sounding the bottom of the ice sheet and avoiding surface clutter. The depth sounder operated at 195 MHz, as opposed to the 150 MHz frequency of years past. The scientists and engineers on the mission also decreased the size of the antennas to accommodate a change in antenna array on the plane.

The Twin Otter operated with six elements per wing, but the size decrease allowed CReSIS engineers to rotate the elements 90 degrees. “Now they’re perpendicular,” Rodriguez-Morales said. “They used to be in the direction of travel. It helps to minimize clutter.”

Fieldwork always involves trial and error and unexpected setbacks, and it relies heavily on the ingenuity and improvisational skills of the involved scientists. With a new system operating at a new frequency, the Twin Otter team faced an unexpected source of interference: the strobe lights on the tips of the aircraft’s wings. An interfering signal masks the signal the researchers are trying to detect, which is quite weak. Normal sources of interference come from inside the plane. As researchers examine the data from each antenna, they usually see the interfering signal decrease as they move away from the plane. In this case, though, the opposite occurred: the interference was strongest next to the tip of the wing. The problem temporarily perplexed those involved, but CReSIS’ talented team quickly discovered the source of the issue. “It was nice because it was a pretty easy fix,” Smith said.

During the mission, the weather also served as a source of frustration. “This year it’s been worse than ever,” Rodriguez-Morales said. “People who have been going there for 20 years, even they said it was the worst they’d ever seen.” Often, the CReSIS team would be awake and ready to fly for the day at six or seven in the morning, only to find that the weather prevented any flights at all. “It can be frustrating at times. But that also makes it really exciting when you actually get to go out and fly,” Smith said.

The team faced the worst of weather in Kulusuk, operating out of a tiny hotel more than a mile from the nearest village. “In Nuuk we were able to do everything in three days. You can compare that to Kulusuk, where it took us three weeks,” said Daniel Gomez, a graduate student and radar engineer on the mission. “But it’s an experience we enjoyed. We had time in Kulusuk to actually develop some other software for both the Ku-band and accumulation radars.”

Smith said that though they had to trek through a mile-and-a-half of several feet of snow to reach town, the team made the journey more than once. “It’s very interesting to see new cultures,” he said. “It was one of the more unchanged forms of the native Greenlandic people, how they would’ve lived more so than some of the bigger cities where we were.”

The group dynamics of the scientists on the mission helped the team get through the often burdensome effects of the weather. “Sometimes you can get some cabin fever if the weather’s bad enough that you can’t get outside for a few days,” Smith said. “But the people that I was there with were all really great, so there was really no internal conflict within the group.”

Despite the weather, the Twin Otter team was able to get in just over a dozen flights. “It was very encouraging that we got all those flights in, given the weather conditions. I think we’ve still got a lot of work to do with the data. So it’s tough to say just yet, but it felt like we put in a lot of hard work in the field, and I hope it’s rewarded with some conclusive results,” Smith said.

Although it’s impossible to make a comparison in all cases, and some data requires advanced processing techniques, Rodriguez-Morales said that he saw a clear improvement in some of the data.

“What we’re trying to achieve is always to get better results than previous years, and there’s a lot of things that we have improved,” said Gomez.

Rodriguez-Morales said that there is always a need for new, better data and repeated paths for the sake of comparison. A return trip is scheduled for 2013. In the meantime, the CReSIS team will be working on the miniaturization of instruments to enable longer flights on smaller planes.