A Colorado freezer is out of space to store ice samples up to 4.5 million years old

A minus-40-degree vault concealed in a federal government warehouse west of Denver holds the climate science equivalent of gold: the United States’ growing collection of ice from around a warming planet, half a million cylindrical cores up to 4.5 million years old.

The ice can reveal climate history and its safekeeping has become a global priority as scientists race to calculate what humanity faces.

Climate scientists seeking clues in the ice head to the U.S. Geological Survey’s regional headquarters, where they bundle up and pass through massive swinging doors into the 8,000-square-foot walk-in freezer —  the largest ice repository in the world. Outside at a loading dock, trucks arrive delivering new ice extracted from Antarctica, Greenland and high mountain glaciers.

But the freezer is outdated and full, and a long-planned replacement won’t be constructed for two years. This has forced Ice Core Facility curator Curtis La Bombard to begin a culling process to decide which ice cores stay, which must go, and what to do with surplus ice.

“There’s always a way to figure stuff out,” La Bombard said.

The ice preserved here became the basis for establishing the timeline of the Earth’s climate history, including the human impact since industrialization around 1870. Government-backed researchers began extracting ice cores during the Cold War. They discovered layers, each holding bubbles of trapped air, which can be dated and analyzed to determine past atmospheric concentrations of heat-trapping gases, such as carbon dioxide and methane.

The current concentration of those heat-trapping greenhouse gases — measured by the National Oceanic and Atmospheric Administration at an average of around 420 parts per million — is higher than at any point in a continuous record stretching back 800,000 years. “We are in uncharted territory,”  USGS program coordinator Lindsay Powers said.

Scientists are still collecting polar ice at a cost of more than $10,000 per yard as they push to fill in their record of climate history extending back millions of years. The work begins with industrial-scale drilling to penetrate as deep as 11,171 feet beneath polar surfaces.  Researchers move the six-inch-diameter cores from remote locations using airplanes, then transfer them to specialized containers for shipping to the USGS warehouse at the Denver Federal Center.

What scientists learn from the ice they can combine with current observations to better understand what is happening today.

“This can help us understand how the earth may change very quickly,” said geologist Tyler Jones, a University of Colorado professor based at CU’s Institute for Arctic and Alpine Research (INSTAAR), who has focused on ice in western Antarctica during the relatively warm Eemian period about 125,000 years ago. The question is whether Antarctic ice sheets stayed in place.

“We need to understand how that ice sheet behaved in the past. If that ice tended to want to disintegrate and go back into the sea back then, we should take more action to prevent that now,” Jones said. “If we don’t, we will probably lose vast areas of coastal cities over the next hundred years.”

Earlier this year, INSTAAR geologist Brad Markle went to the freezer as part of a project to help determine whether dust storms may increase around the planet as temperatures rise. Dust particles can be detected in old ice and measured. His initial investigations concluded that warming may not lead to worse dust storms because “the Earth is much dustier when it is colder,” Markle said. “The atmosphere is so much drier when it is cold — leading to way more dust on average.”

“These ice cores are useful in trying to understand the patterns of temperature change as we increase CO2,” Markle said. “They are a good way for testing out our ideas of the physics of how that process works.”

But the freezer is overloaded and badly in need of replacement, according to USGS officials, who manage the facility for the National Science Foundation.

La Bombard has labored to keep the freezer operating and make sure no ice melts, maintaining redundancy systems that include emergency generators. The freezer runs on the outdated coolant R22 (Freon), a chemical the U.S. Environmental Protection Agency is phasing out because it degrades the atmosphere.

The new replacement freezer, designed with a rolling rack system to give a 30% increased storage capacity, won’t be ready until 2026.

This compelled the culling. Some ice cores have degraded. There are duplicate cores from some regions. Some cores already have been sliced repeatedly for the removal of ancient air bubbles for analysis.

First, La Bombard issued a notice in climate science circles, encouraging scientists who had a use for culled ice to claim it soon. Otherwise, unclaimed ice could be set out in the USGS parking lot as part of a melting ceremony, La Bombard suggested half-jokingly.

“This was tactical on my part,” he now confides.

The notice alarmed scientists. Jones at INSTAAR grew “really concerned,” he said. “I was feeling this foreboding sense of loss like this ice would be lost permanently after this weird melting ceremony in the parking lot. I just didn’t want that to happen.”

He and colleagues hastily proposed to rescue surplus cores they could preserve in a smaller INSTAAR freezer.

Culled cores also have been made available to artists, who have used them for photographic and other projects exploring the beauty of ice. Members of the public also may be able to submit applications to obtain surplus ancient ice for beneficial projects, La Bombard said.

Meanwhile, the latest large shipment from Greenland, including ice from areas that are melting, will arrive here by March to be stored, he said.

“We are going to make this work.”

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