When your freezer breaks down, you might lose some leftovers or a box of your favorite popsicles. But when a scientist's freezer malfunctions, the world stands to lose thousands of years’ worth of stored history. That’s what happened last week, when an equipment failure at the University of Alberta (UAB) melted ancient samples of Arctic ice.

An ice core is kind of like the vertical equivalent of a tree’s rings. The gas bubbles, sediment, and chemicals trapped in each of its many layers tell a story about the world at that particular moment in time.

UAB’s Canadian Ice Core Archive holds 12 cores—nearly 1 mile of ice—representing roughly 80,000 years of our planet’s history. Some of the samples have been in storage since the 1970s. Many of them are now considerably smaller than they were a few weeks ago.

Each long, cylindrical core is stored in segments, a space-saving measure that may have been the collection’s salvation. The segments were divided between two freezers, one of which shut down over the weekend when the temperature-control system failed. In trying to correct the issue, the system made things worse, blowing hot air over the samples, turning the ancient ice back into water for the first time in millennia.

Glaciologist Martin Sharp rushed into the archive to find steaming puddles all over the floor. “It was more like a changing room in a swimming pool than a freezer,” he told The Guardian. “I’ve had better days. Let’s say that.”

The archive lost 12.8 percent of its total sample mass, including about 22,000 years’ worth from the Penny Ice Cap on Baffin Island. Some of the samples are “clearly toast,” Sharp told The Guardian, while others were barely affected.

The samples have been moved into more secure storage, and Sharp and his team plan to drill new samples to replace what they’ve lost. But the ice covering some of the original sampling sites is melting, too.

“Some of these ice caps are disappearing,” Sharp told The New York Times, “and we’re going to lose this record, in some cases sooner rather than later.”