Ask NASA Climate | February 8, 2016, 20:46 PST

The real ice sheets of Antarctica

By Laura Faye Tenenbaum

The terminus of Taylor Glacier as seen from the helicopter. Photo by P. Neff.

The terminus of Taylor Glacier as seen from the helicopter. Photo by P. Neff.

“I’m looking at 10 glaciers and I’m sitting on one,” said Dr. Heidi Roop of the University of Rochester over satellite phone. “I’m looking at a landscape that’s been here for millions of years unaltered by people.” Roop had called me from Taylor Glacier, an outflow of the East Antarctic Ice Sheet, which flows down through Antarctica’s McMurdo Dry Valleys. I’m looking at a mountain that no human has ever touched, ever. This is a landscape where it feels like humans shouldn’t be. There are no animal trails, no trees. There’s rock and ice and us.”

Roop and the rest of the eight-person team, which included one driller, two scientists, three Ph.D. candidates and a camp cook/manager, had come to drill for ice cores at Taylor Glacier because of its unique configuration. Drilling ice cores is a technique climate scientists use to collect samples of trace gases such as carbon dioxide, methane and carbon monoxide that have been trapped in air bubbles in the layers of polar ice.

A large diameter blue ice drill extracting ice cores at Taylor Glacier. Credit: H. Roop.
A large diameter Blue Ice Drill (BID) extracting ice cores at Taylor Glacier. Credit: H. Roop.
Air bubbles make up 10 percent of glacier ice. That may sound incredible, but it's true. In fact, teams of scientists spend entire careers studying these ice cores to learn about Earth’s atmosphere. In a traditional ice core, the ice is horizontally layered. The surface layer is the youngest, made of recent snow with modern atmosphere filling tiny spaces between snowflakes. Ice core science teams drill vertically down through time. The deeper you drill, the further back in time you go. (The deepest borehole, at Vostok, Antarctica, is more than 3,600 meters deep.) According to Dr. Peter Neff, a glaciologist who was also on the call, “We now have a very good understanding of past greenhouse gas concentrations because there’s been so much research since the 1990s, especially methane, for example. The signal of methane concentration is globally representative and we know from these ice cores the heartbeat of methane through the past 800,000 years with high accuracy.”

Scientists drilling for ice cores head to Antarctica because it’s the cleanest place on the planet. (There’s so much more pollution and dust in the Northern Hemisphere.) “We’re not studying Antarctica itself, although Antarctica is a huge player in the global climate system," Neff said. "But rather we’re learning things about global climate that we can learn only in Antarctica. It’s so far away, yet it holds clues that inform our understanding of the rest of the world.”

Traveling back in time

Taylor Glacier is an unusual place on a continent that’s full of the unusual, which is why this group of scientists traveled there. The glacier flow has essentially tipped ice layers on their sides, so to travel back in time the team can simply walk across the glacier instead of having to drill deep down. Time is stretched out north to south, so “as you walk northward you’re going forward in time, from ice that’s 80,000 years old, past the coldest part of the last glacial period 20,000 years ago (when it was so cold and dry there was less vegetation, so the atmosphere was dusty), all the way to ice that’s only 8,000 years old,” Neff explained. The team also took their Ski-Doo down the glacier about 10 kilometers to a site where they previously found 125,000 to 130,000 year old ice, which formed during the last interglacial period—the last time global climate was close to today’s warm temperatures. Other ice core records suggest that this time period was actually several degrees warmer than today, making it our best analogue for the warm conditions we’re headed towards.

The view from the helicopter looking up Taylor Glacier. Taylor Glacier Camp is located about 15 km (about 9 miles) from the terminus, or end, of Taylor Glacier. Photo Credit: H. Roop.
The view from the helicopter looking up Taylor Glacier. Taylor Glacier Camp is located about 15 km (about 9 miles) from the terminus, or end, of Taylor Glacier. Photo Credit: H. Roop.
Because the twists and folds of Taylor Glacier bring old ice to the surface, scientists only need to drill a few meters deep to collect very large samples from specific time periods. The team can core down into, say, the transition at the end of the last glacial period 20,000 years ago, when the climate system shifted back towards warmer temperatures—with some rapid climate change “speed bumps” along the way. The team hopes that gathering large enough samples of gases from this time period will help us understand what drives large climate shifts, what the real rates of change are and if we’re headed towards any tipping points. “We can ask more specific questions because we can get much bigger samples, which gives us room to unlock minute details in the chemistry of gases trapped in the ice,” Neff said. “For some work, we’re literally chain-sawing a meter down into the ice and breaking it out with a big metal bar and taking out samples that are a meter long by 30 centimeters wide that weigh like 250 pounds,” Roop added. “You should see my biceps right now.”

24 hours of daylight

Although there is 24 hours of daylight during the summer in Antarctica, the drill team wakes up in the middle of the night when the sun moves behind a mountain range and creates a shadow for about five hours. “The sun just does a big circle around us, but the shadow makes it a lot colder, which keeps the drill from freezing into the glacier,” Neff explained. Then Roop added, “When the sun goes behind the mountain, the glacier crackles and pops—loud pops like gunshots—because of the temperature drop.”

Once they collect the ice cores, some are put into a pressure chamber under vacuum to remove all the modern air and are then melted. The gas from the ancient bubbles is released as the ice cores melt, and then gets carefully pulled into sample canisters, which are about the size of a SCUBA tank.

V. Petrenko and P. Neff cutting a BID core on the bandsaw. One section will be melted to extract ancient gases, and one section will be subsampled and sent back for analysis at the University of Rochester Petrenko Lab. Credit: H. Roop.
Near the end of this field campaign, the team will pull everything out to waiting helicopters using a big pink sled towed behind their Ski-Doo. The team will fly the ancient gases extracted from the ice cores to McMurdo Station before heading back to the University of Rochester Petrenko Lab, the Scripps Institute of Oceanography Severinghaus Laboratory, and the Oregon State University Ice Core and Quarternary Geochemistry Lab. The Ski-Doo will eventually hitch a ride from the helicopter as well, in a sling load dangling from a big wire cable tethered to the bottom of the helicopter. “Antarctica is a really emotional place," Roop said. "It’s a rare, rare, rare, rare opportunity to go where people don’t live, where people can’t live. This is the edge of where humans should be. There’s no trash, no animal tracks, no power lines, not even a bird; nothing to give you scale. It’s like the exhilaration of breaking a rule, poking a boundary. And there’s something thrilling about that.”

The National Science Foundation has a Presidential mandate to manage the U.S. Antarctic Program, under which it supports researchers, coordinates all U.S. science on the southernmost continent and in the surrounding ocean, and provides the infrastructure and logistical support needed to make the science possible.

Find out more about the University of Rochester Ice Core Expedition here.

Thank you for reading.