Deep ice core samples reveal Earth’s climate history

Study of ice core samples deposited over millennia reveal that climate change can be very rapid, happening in a matter of decades

ice core room
Ice core storage facility at the NICL

By Jenney Coberly

Deep in the frozen vault of the National Ice Core Laboratory in Lakewood, Colorado, pieces of ice up to nearly a half a million years old are helping researchers unravel the mysteries of climate change. The ice samples were collected in Antarctica and Greenland. They are part of one of the world’s largest collections of ice cores in a program funded by the National Science Foundation and the U.S. Geological Survey.

Antarctica and Greenland have layers of snow and ice preserved in thick glaciers over hundreds of thousands of years. Through studies of the ice cores extracted by drilling thousands of meters into these glaciers, scientists can create mathematical models of Earth’s climate history. They’ve discovered extreme climate swings in Earth’s past, some of which occurred very rapidly, in less than a decade.

Ice core samples provide information on atmospheric composition, temperature and other climate data in a very long and continuous record, making them one of the most important tools for climate researchers.

“It’s very important in climate change research to know just what time is represented by a particular thickness in an ice core,” said former ice core lab director and USGS climate scientist Todd Hinkley. “It doesn’t really do you much good to say, ‘Well, we went in pretty deep, so this must be old’. You’ve got to be precise about it, and the ice cores do allow this. This is their strength as a scientific research tool.”

ice core canister
Ice core canister in the NICL.

Geoffrey Hargreaves, the lab’s curator, recently returned from a stint at the remote West Antarctic Ice Sheet Divide Project in Antarctica, where researchers just finished retrieving ice core samples at depths up to 3331 meters (over 10,000 feet). The WAIS divide is extremely remote, some 800 miles from the main Antarctic research station at McMurdo. The latest shipment of samples from the site are set to arrive at the lab this week.

So how do these samples get from a remote ice drilling outpost in Antarctica to the ice vault in Lakewood?

As the samples came up from the depths of the glacier via the giant drilling apparatus, they were cut into one-meter pieces, bagged in heavy plastic, placed in metal canisters, and then packed into insulated shipping containers. The containers were loaded onto airplane pallets and flown back to McMurdo Station for temporary storage. At season’s end, a cargo ship with special redundant refrigeration units transported the samples to Port Hueneme, California, where they arrived March 10. They were then loaded onto flatbed trucks for the journey to Colorado, and are expected at the Ice Core Lab March 15.

“We will offload them one by one, and load everything into the freezer. I’m getting 42 skids of ice, which will literally fill my freezer front to back down one aisle,” Hargreaves said.

Starting in June, the samples will be processed for study. The ice cores are pulled out and opened up, and small slabs are cut down the sides to be used for isotope and chemical analysis. The samples are packaged and shipped out to the principal investigators. The main core will get run through an electro-conductivity machine, which provides a strip-chart documenting the temperature history of the ice layers in the core.

The conductivity of the ice provides valuable information about the temperatures when the ice was deposited.

“Volcanic events are helpful because we know when a lot of the volcanoes went off, and when we come across one, we can use that to help pinpoint our timelines,” Hargreaves said.

ice core layers
Ice core samples, with the layers clearly visible

The core processing line is in the “warm room”, which is kept at minus 11 degrees. The ice vault where the cores are stored, however, is kept at minus 33 degrees.

I got a chance to sample just how cold that is during the March 10th tour of the ice core lab.

Here’s a 3-minute video excerpt of the tour, including some shivery time in the very impressive ice core vault. The samples are stacked from floor to ceiling in row after row, and it’s rather surreal walking down the narrow rows in that amazing cold, wondering what new information about our climate is stored in those frigid cylinders.


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