Ice core studies to reveal Earth’s climate history
10 January 2023
It is very common to find objects and even animals trapped in the ice, but did you know that like a prehistoric fly trapped in amber during the dinosaurs’ days, airborne relics of Earth’s earlier climate (including dust, air bubbles, sea salts, volcanic ash, and soot from forest fires) can end up trapped in glacial ice for eons too?
In fact, climate scientists consider these relics very fascinating, not only because they tell a story about how our planet’s climate and atmosphere have changed over thousands of years, but also because of the impact that they can have on current worldwide civilizations and within a few future generations (especially in coastal regions).
What ice cores can reveal
According to experts, ice cores may reveal whether Antarctica’s western ice sheet melted fully the last time Earth’s climate warmed to the temperatures the planet is predicted to reach in the next two centuries. If it did, it’s likely to happen again, which would raise sea levels significantly enough to threaten many seaside cities.
“We have some evidence that this may have happened, but we aren’t sure,” says Erich Osterberg, who studies ice cores as an assistant professor in the Department of Earth Science at Dartmouth College.
Unlocking ice cores’ secrets
With the aim of making an exhaustive analysis inside an ice core, researchers in the lab may melt or crush the sample bit by bit; each deeper layer represents a slightly earlier time in the Earth’s climate history. At the end, the ice arrives in small strips, about 1-by-1 inch apiece, which are smaller slices of the roughly three-foot-long, coffee-can-wide pieces a drill pulls out of a glacier.
In many cases, researchers decide to look at actual bubbles of the early atmosphere trapped in the ice as it formed, but in order to investigate them, the sample must be crushed under a vacuum hood, which keeps other air out while they pull the newly released air into vials.
So, as you can see, it is all about a very delicate and unique process that requires time, and even every clue in the ice, whether a grain of sea salt or an air bubble, is so miniscule and the measurements must be incredibly precise that any analysis must be done in a “clean room” setting. Plus, the researchers wear body suits and multiple layers of gloves, and the room must have ultraclean filters and vents to keep the air pristine. “Even just a fingerprint from a scientist holding the core can ruin the sample,” Osterberg says.
Mystery in the melt
Each phase of this process is so important that after analyzing enough ice core slices, a researcher can look for patterns to track changes in the atmosphere’s composition and temperature, and what activity on Earth shaped them.
On the other hand, this research has allowed scientists to discover that the quantity of carbon dioxide and the global temperature have been linked for at least the last million years of Earth’s history, and Osterberg even thinks ice cores will help figure out whether Antarctica’s western ice sheet melted 125,000 years ago, the last time Earth’s climate warmed to the temperatures the planet is predicted to reach in the next two centuries.
Ice core trekkers
However, before the climate fossils can tell their stories, they must be retrieved. For that reason, rugged researchers like Osterberg and his colleagues have spent multiple summers scoping never-before-explored areas on glaciers before trekking out to collect a core.
To begin with, to pick the spot, they check the ice’s thickness and layers (the flatter the better) and put out GPS markers to track how quickly the ice is flowing and deforming (the slower the better).
After that, they have to set up their base camp and drill into the ice. A process that, in fact, may take six to eight weeks for two cores that are each 700 feet long. Some researchers, particularly in Antarctica, may drill two miles and take much longer.
“Something always goes awry,” Osterberg concludes. “You’re doing this in one of the most extreme environments you can imagine—far from help, remote, and with not a lot of spare parts.”
Therefore, it is a journey full of complications and dangers, not only because of the weather conditions but also because of the wildlife in the areas they usually explore. In short, it is a dangerous job whose fruits have benefited humanity in numerous ways.