Scientists look at how Antarctic landscape changes over time
Posted June 17, 2011
Much of the research in Antarctica these days is directed at how quickly the continent’s ice sheets and glaciers may respond to climate change.
But Jaakko Putkonen is interested in how the 2 percent of Antarctica not covered by ice reacts to a different kind of environmental change.
An assistant professor at the University of North Dakota , Putkonen studies landscape evolution — how natural forces erode and shape the exposed rock surfaces. In Antarctica, that means traveling to dry and cold glacial valleys far from any research station to set up experiments and collect samples for analysis back in the laboratory.
“We’re interested in how the landscape is changing over time,” explained Putkonen shortly before jumping into a ski-equipped Twin Otter with his young team for a stunningly beautiful site called Moraine Canyon at Amundsen Glacier.
The researchers were eager to return to their fieldwork after several days of weather delays at a large field camp in the central Transantarctic Mountains where they and scores of other scientists were based for the 2010-11 austral season. [See series main page: CTAM 2010-11 main page.]
They had previously spent several weeks at a site called Ong Valley at Nimrod Glacier where they had buried soil traps at the surface to capture loose sediments and installed repeat-photography sites at ground level to estimate how much sediment is moving in the area. A climate station left in the field will monitor daily local wind and temperature conditions throughout the year that may reveal clues for the reasons the sediment is moving.
The team also collected rock and soil samples that will be used to determine how long the surfaces have been exposed through a technique called cosmogenic nuclide dating.
Terrestrial rocks are pelted by secondary subatomic particles created when cosmic rays, or charged particles from outer space, hit the Earth’s atmosphere. The dating method is based on the build-up of cosmic-ray-produced isotopes, such as beryllium-10, which has a long half-life. For example, Be-10 production occurs at a steady rate. By counting the number of Be-10 atoms, scientists can determine the length the rock has been exposed at the surface.
“We use the cosmogenics to understand the erosion of those landscapes,” Putkonen said.
All of the low-tech and high-tech data crunching will help the researchers understand how quickly the landscape erodes on time scales of a few years to millions of years. Computer models will help explain what drives the landscape evolution. Water is usually a culprit — but not in frozen Antarctica. Putkonen said the wind plays a primary role in punishing rock and pushing soil.
One thing is certain: The landscape does change. Based on previous work in the McMurdo Dry Valleys by Putkonen and co-principal investigator Greg Balco at the Berkeley Geochronology Center , loose soil erodes about 1.5 meters every million years.
“That’s much more than anybody expected,” Putkonen said, though in relation to erosion rates elsewhere in the world, it’s extremely slow. “This [project] is trying to build basic understanding of how these processes operate — and what are the important processes.”
Still, the finding has implications for researchers interested in examining these valleys for other purposes. For example, fossils, microbial life, or other materials that might be expected to exist near the surface based on stratigraphic dating of the region could have been eroded away.
“You’re not going to see anything that was there millions of years ago because that surface is gone,” Putkonen said. “It’s giving us a new perspective of what kind of things might be out there and how the system is changing.”
Amazingly, there may be microscopic life “out there” among the rocks. Or, more accurately, within the rocks. In the past, Putkonen has found cryptoendolithic organisms in his samples.
“There is life growing inside the rocks, so some of the rock samples we got may show some bacteria or lichen growing in these valleys,” explained Holly Westad, a University of North Dakota biology and geology undergraduate. “It’s a small biological aspect, but there really hasn’t been much research in the bacteria and lichens in these remote valleys of Antarctica.”
The landscape research is also important to studies of places far from Earth, like Mars, which often draws comparisons to Antarctica’s landscape.
“There is a renewed interest in these kinds of environments mostly because of the work being done on Mars. The environment on Mars is very similar to the valleys here,” Putkonen said.
It seems doubtful that there is a valley on Mars as breathtaking as Moraine Canyon, about an hour-and-a-half scenic flight south of the CTAM field camp. The plane passes crevassed glaciers that look like rumpled sheets and steep icefalls that pour down sheer rock walls like melted frosting.
The Twin Otter that carries several members of the field team and additional equipment for the group’s extended stay makes a sweep through the steep walls of the canyon, some blanketed in snow and others nearly bare. The landing on an ice field feels like driving on a road of rumble strips.
The team, including graduate and undergraduate students from the University of North Dakota, would end up spending about two weeks at the site, hiking to the ice-free areas of the valleys to set up their experiments and fill canvas bags with rocks. The scientists will return to both Ong Valley and Moraine Canyon in 2011-12 to retrieve their equipment.
Putkonen prefers extended stays at these deep-field locations. Not only does it make life simpler in terms of logistics — when weather could ground a helicopter for a week — but also it helps with interpreting the data.
“You learn a new language by immersion. You learn the landscape by immersion,” Putkonen said.CTAM 2010-11 main page.