How Ice Core Scientists Drill Into the Past to Study Climate Change

Ice is one of Earth's oldest natural wonders, existing long before humans ever appeared. Its properties and uses have been known to people since ancient times. Now just imagine holding a time capsule of Earth's atmosphere from nearly a million years ago. That is what ice core scientists do when they drill deep into the polar ice sheets of Antarctica and Greenland. Beneath layers of compacted snow, they find frozen records of Earth's past climate, preserved in cylinders of ancient ice.

Why Ice Cores Matter

Every snowfall that lands on a glacier becomes part of a yearly layer. Over centuries, these layers compress and turn into solid ice. As they form, they trap tiny bubbles of air, and these bubbles contain actual samples of the atmosphere from millions of years ago.

According to the British Antarctic Survey, ice cores provide direct records of past temperatures, greenhouse gases like carbon dioxide and methane, and even volcanic activity. Scientists can then compare these past conditions with today's climate, which is how they confirm that recent changes are not part of a natural cycle.

(Image credit- An Ice Core: NASA's Goddard Space Flight Center/Ludovic Brucker)

Reaching these icy time capsules is no easy task. Scientists choose remote spots in Antarctica or Greenland where the ice is undisturbed and thick enough to reach very old layers.

The Ice Drilling Program explains that they use electromechanical drills, which lower a hollow, rotating drill head into the ice. These segments are carefully stored in insulated boxes to keep them frozen during transport. They are then taken to cold labs for analysis.

How Old Is the Oldest Ice?

The oldest continuous ice core record comes from Dome C in East Antarctica. This project, known as EPICA, recovered ice that is around 800,000 years old. 

Some scientists believe even older ice might be buried deeper or in different parts of Antarctica. The challenge is drilling deep enough without disturbing the delicate layers and air bubbles, which could destroy the very data they are trying to preserve.

At the same time, in a landmark discovery from the Allan Hills region of East Antarctica, scientists have retrieved ice that is approximately 6 million years old, making it the oldest directly dated ice and trapped‑air sample on Earth. 

The analysis of the ice reveals that the region has cooled by about 12 °C over those 6 million years. Crucially, the next phase of the research will focus on measuring greenhouse‑gas concentrations and ocean heat content preserved in the bubbles of this very old ice. 

Scientists are trying to understand by studying these ancient atmospheric conditions, how natural climate systems behaved in a much warmer world and to refine how we interpret today’s rapid changes.

What Ice Tells Us About Climate Change

Ice cores show that the amount of carbon dioxide in the air today is much higher than at any time in the last 800,000 years.

The rate of this rise is especially alarming. In natural cycles, changes happened over thousands of years. The current spike has occurred in less than 200 years, lining up with the industrial era and human fossil fuel use.

This kind of physical evidence makes ice cores one of the most powerful tools in climate science. In a way, ice core scientists are like historians of the planet, except their records are buried deep under the ice and contain real samples of Earth’s past.

The Earth has changed before, but never at this pace and never in this way. According to NASA’s climate evidence, today the planet is heating up much faster than it ever did after past ice ages, and carbon dioxide from human activities is rising hundreds of times faster than from natural causes.