The longest ice core ever extracted from a Himalayan glacier now resides in a freezer at OSU. Scientists hope to unlock its secrets before it's too late.

To most people, they're glaciers: majestic, impregnable walls of ice that tower above sea level. But to Ohio State University glaciologists Lonnie Thompson and Ellen Mosley-Thompson, they're archives: perfectly preserved records documenting the planet's history. For more than four decades, the husband-and-wife team has been hustling to extract those records and bring them home to Columbus for closer study.

It's a mission made all the more urgent by the fact that these historical records are melting. “The ice continues to disappear, and so does the archive,” says Thompson. “A lot of the ice we have in our freezer you cannot [extract] today.”

The freezer in question is in the basement of OSU's Byrd Polar and Climate Research Center, where Mosley-Thompson is the director and her husband is a senior research scientist. It preserves pieces of their precious archive—7,000 meter-long cylinders of glacial ice, packed in shiny aluminum-clad tubes and kept at a bone-chilling 30 degrees below zero. The ice cores were drilled and extracted during grueling, months-long missions to mountaintop glaciers in remote places like the Andes, Antarctica and Mount Kilimanjaro. Their research teams haul drills and equipment—as much as 6 tons of it—to the summit and bring back the ice by whatever means necessary: horses, Sherpas, yaks, even hot air balloons.

The most recent addition to the collection was pulled from deeper than any core outside the poles. In 2015, a 1,000-foot-long piece of ice was extracted in meter-long samples from the 22,000-foot-high Guliya ice cap in Tibet's western Kunlun Mountains. End to end, the samples are nearly twice as long as the LeVeque Tower is tall, and Thompson, who led the expedition, says the ice at the bottom may be as much as 600,000 years old.

Glaciers develop in layers of compressed snow and ice that record the passage of time like rings on a tree. Scientists use radiocarbon dating and other tests to establish a timeline for each core, then test the chemical qualities of the ice and the air trapped in its bubbles to develop a climate history. They enlist microbiologists, geologists and others to look at the debris, plant matter, insects, microorganisms and everything else they find in the samples.

While the glaciologists' initial interest in the ice cores was uncovering the history they contained, their more urgent mission today is documenting a specific aspect of that history: climate change, and its effects on the glaciers themselves.

Preliminary results from the Tibetan ice core are alarming, says Thompson. On Guliya, he found an average temperature increase of 2.7 degrees Fahrenheit over the past 50 years. This is especially worrisome in the Tibetan Plateau and surrounding region, where glaciers serve as a freshwater source for 1.4 billion people. As the glaciers lose more ice than they gain through precipitation and freezing, drought becomes a threat. Melt from Tibetan glaciers also plays a role in rising sea levels. And the glaciers of the region, he says, are responding more quickly to climate change than those at the earth's poles.

To say that something is moving at a glacial pace, Mosley-Thompson says, once meant that it was moving very, very slowly. “Now a glacial pace can be very quick.”

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