Watching the History Melt Away: Climate change is destroying the ice core record, but a few archives seek to preserve the frozen data

Class Project

December 10, 2020

When Lonnie Thompson first saw the Quelccaya Ice Cap in the Andes Mountains, he was blown away by the sight. Standing above the Amazon, just shy of the fourteenth parallel south of the equator in the tropics — well outside the polar regions where most scientists had been studying ice cores — the expanse of ice swept from horizon to horizon.

Now, 45 years later, Thompson has watched the glacier melt and retreat, leaving behind lakes, bare ground, and far less ice.

With climate change affecting temperature worldwide, ice caps and glaciers, especially those on mountains and on the coasts of polar landmasses like Antarctica and Greenland, are melting rapidly, and may soon disappear.

For scientists who study ice cores, the loss of these glaciers represents the impending loss of an unparalleled record of climate history and that impact may carry over into human understanding of the future and policies designed to address it.

When looking to the past, most methods of study are by proxy.

“We're recording some isotope or some measurement or something that has an indirect relationship to how something that affects climate or temperatures,” said Benjamin Hmiel, who completed his Ph.D. studying ice cores at the University of Rochester. “In the case of ice cores, it is a direct relationship for the bubbles in the ice cores. Those are the bubbles of what the gases are.”

That’s because the ice that scientists drill to gather ice cores forms over hundreds or thousands of years. When the snow falls and goes a whole season without melting, it begins to form a porous layer that scientists call firn.

When enough snow piles up, the lower sections of firn compress into ice. All the holes in the porous snow layer turn into bubbles of air, trapping little samples of the atmosphere.

Using drills, scientists can remove long cylinders of ice that show a timeline Earth’s climate, as well as particles that were floating in the air or organisms living in nearby ecosystems. Once extracted, scientists can melt, grate or sublimate samples of the ice to extract the bubbles and particulate for research.

In the case of alpine glaciers, ice cores can give a specific look at the local history of an area, said Joe McConnell, a research professor of hydrology at the Desert Research Institute.

“Ice cores from alpine regions provide you with an understanding of local precipitation, chemistry or local environmental history, if you will — much more local than the polar ice sheets,” McConnell said.

A 2019 study published in the journal Geophysical Research Letters, on which McConnell worked, used ice cores from the French Alps to study heavy metal pollution in Western Europe.

Looking at the levels of lead and antimony in the ice core from the alpine glacier, McConnell and the rest of the team were able to identify increased levels of lead pollution during the Roman empire. With this information, they were able to show the effects of increased lead mining and smelting in that period of European history.

The information within the glaciers and ice caps helps structure understanding of the past and calibrate scientific models. This is especially significant for climate data, which can help create an understanding of the current changing climate and inform policies to reduce the impact of humans.

“It's important to remember that we use those models — climate models, for instance — to predict the future and design policy decisions about the future of emissions or whatever,” McConnell said. “So in order for that to be efficient and effective, your models need to be tested and verified. And the way to do that is with data from the past.”

However, for Lonnie Thompson, research involving alpine glaciers now is largely about getting the information before it’s gone.

“I sometimes refer to it as going to see a patient in a terminal cancer facility,” Thompson said. “You know what's going to happen and you know that there's nothing you can do to prevent that.”

While the inland areas of Greenland and Antarctica tend to stay cold enough to keep the ice safe from melting, alpine glaciers are receding. When snow falls, it doesn’t stick around to compress, and the ice that is there is melting fast.

A 2017 study published in the Journal of Glaciology showed a steady loss of glacial ice from the mid-19th century to the early 21st century. The first decade of that latter century experienced an especially sharp decrease in ice mass.

While some of this melt comes from a transition out of the Little Ice Age, a period of time roughly from 1300 to 1800 when temperatures were cooler and mountain glaciers expanded, the effect is worsened by human-caused climate change.

The rising temperatures caused by carbon emissions have even affected those presumed-safe sheets of ice in Antarctica and Greenland. In 2012, during a rare warming event, 97% of the entire ice sheet indicated surface melting.

A melting Greenland ice sheet poses a danger for coastal communities worldwide — there is enough fresh water frozen there to flood many coastal areas — but for ice core scientists it also highlighted another danger of melting ice: when the ice turns to water, it compromises the record stored within the newly exposed layers.

“As soon as the ice melts, its chemistry changes because it melted … and so the record that we would normally use for environmental chemistry, for instance, just degraded a little bit,” McConnell said. “So as you get more and more melting at these high-elevation sites, even on the polar ice sheets, you're going to start to degrade the record.”

However, when the record remains intact and scientists work to get data from within, the extraction of materials and information from inside an ice core means destroying the ice. But techniques for analyzing ice core samples have evolved and grown rapidly in the past 20 years with researchers finding ways to access more detailed and more varied information in ice cores. As new techniques for analyzing ice cores develop, the data collected today may not be as complete as it will be in the future.

“20 years from now there's going to be new technology, there's going to be new questions that's going to be asked that we're not even wise enough to ask today,” Thompson said. “But if you don't have the archive, you're not going to be able to answer those questions and so keeping an archive into the future becomes very important.”

The National Science Foundation Ice Core Facility, or NSF-ICF, located in Lakewood, Colorado serves as that archive. The facility’s 55,000 cubic feet of freezer are filled with stacks of ice cores in sleek silver tubes at minus 36 degrees Celsius.

Most of the cores at the NSF-ICF come from polar sites in Antarctica and Greenland where the ice is generally at less risk of disappearing anytime soon, so the largest barrier to getting more is the cost. A recently approved expedition to the West Antarctic Ice Sheet’s Hercules Dome was funded for $3 million by the NSF. But for ice from alpine glaciers, much of it rapidly disappearing, there is no well-established large, central storage space.

For now, the archive run by the Byrd Polar and Climate Research Center at Ohio State University, where Thompson is a research scientist, is one of the best options. In 2010, When Thompson was in New Guinea on a research expedition to collect cores from the ice fields of Puncak Jaya, a local tribe tried to stop him.

“In their words, we were drilling into the skull of their god to steal their memories,” Thompson said. “And I said, 'that's exactly what we're doing, and the day will come very soon when the only memories of your God will be in a freezer at Ohio State University.’”

The Byrd Center has cores from 16 countries, and unlike the NSF-ICF most of the cores come from alpine locations rather than polar regions.

The Ice Memory Project hopes to further fill the gap. Launched in 2017, the Ice Memory Project is working to create a snow cave in Antarctica to naturally store ice cores. Their ice core sanctuary will focus on storing cores from vanishing glaciers, with the goal to transport the first cores to the Antarctic base by 2022 or 2023.

But as the climate continues to shift, glaciers will continue to melt and the record within them will become compromised and vanish entirely. As Thompson looks toward the future, he expects that within 25 or 30 years many of these glaciers will disappear.

“Maybe sometime in the future, climate will cool again, and glaciers will start to grow again, but that archive will always be lost,” Thompson said.