The newest arrivals at a subzero lab in Cambridge are not just some blocks of ice — they are time machines.

This month, British scientists opened white crates packed with glittering cylinders of ancient Antarctic ice. Inside them lie the oldest frozen samples ever retrieved from Earth, possibly up to 1.5 million years old. And now, in a sterile -23°C freezer at the British Antarctic Survey (BAS), researchers have begun the slow process of melting that ice — millimeter by millimeter, bubble by bubble — to reconstruct a vanished world.

What Scientists Hope to Learn by Melting the Oldest Ice

Recovered from 2.8 kilometers beneath the East Antarctic Plateau at a site called Little Dome C, the cores were painstakingly drilled over four Antarctic seasons as part of the Beyond EPICA – Oldest Ice project. The effort spanned 10 European countries and 12 scientific institutions. The ultimate goal: to nearly double the current climate record from ice cores, which stops at around 800,000 years ago.

Now, scientists hope the newly recovered samples will allow them to peer back more than 1.5 million years.

“It’s incredibly exciting to be part of this international effort to unlock the deepest secrets of Antarctica’s ice,” said Dr. Liz Thomas, who leads the ice core research team at BAS. “There is no other place on Earth that retains such a long record of the past atmosphere as Antarctica.”

Unlike sediment cores from the ocean floor, which offer indirect clues about past climate, ice cores hold direct snapshots of ancient air. Tiny bubbles trapped in the ice contain actual samples of past atmospheres — concentrations of carbon dioxide, methane, and other gases frozen in place since the day snow fell and compressed into ice.

At the heart of the project lies one of climate science’s most persistent mysteries: Why did Earth’s climate rhythms change roughly a million years ago?

For much of the planet’s recent geological history, ice ages came and went every 41,000 years. Then, during a period scientists call the Mid-Pleistocene Transition, that rhythm suddenly slowed. Glacial cycles began lasting 100,000 years instead. And the cause of this dramatic shift remains unknown.

“Our climate system has been through so many different changes that we really need to be able to go back in time to understand these different processes and different tipping points,” said Dr. Thomas.

Researchers hope that the Beyond EPICA ice cores will contain crucial clues about this change. In particular, they will analyze the cores for levels of greenhouse gases, traces of volcanic ash, sea salt, dust, and even microscopic marine organisms called diatoms.

The ice will be melted using a technique known as continuous flow analysis, which allows scientists to measure dozens of elements and isotopes at once as liquid ice flows through analytical machines. One of these, an inductively coupled plasma mass spectrometer (ICP-MS), can detect more than 20 trace metals and chemical signatures, including rare earth elements.

“Our data will yield the first continuous reconstructions of key environmental indicators—including atmospheric temperatures, wind patterns, sea ice extent, and marine productivity—spanning the past 1.5 million years,” said Dr. Thomas.

Clues to Our Future in an Icy Past

The analysis won’t happen overnight. Over the next several years, teams from laboratories across Europe will work in parallel, carefully melting, filtering, and analyzing different sections of the 2.8-kilometer-long core — roughly the height of eight Eiffel Towers stacked end to end.

For now, parts of the ice have already arrived in Germany and Switzerland, where other teams will help reconstruct this frozen history. But some of the most advanced analytical work will take place at the BAS facility in Cambridge, one of the only labs in the world equipped to perform this kind of ultra-sensitive, high-resolution chemical analysis.

The stakes are high.

There is growing evidence that during parts of the Mid-Pleistocene, greenhouse gas levels may have been as high as — or even higher than— today’s. “During that time there’s evidence to suggest that the ice sheets were actually smaller, sea levels were potentially higher, and CO₂ similar to today,” said Dr. Thomas.

That matters, because while past rises in CO₂ happened gradually over thousands of years, today’s greenhouse gas surge has occurred within just 150. The planet is now warming faster than at almost any time in geological history.

“This unprecedented ice core dataset will provide vital insights into the link between atmospheric CO₂ levels and climate during a previously uncharted period in Earth’s history,” Dr. Thomas said. In other words, it will offer valuable context for predicting future climate change.

From a Remote Plateau to a High-Tech Lab

The journey of these ancient cores began far from the fluorescent lights of Cambridge. It began at a lonely site 40 kilometers from Concordia Station, a Franco-Italian research outpost perched 3,200 meters above sea level in Antarctica.

There, teams worked in the brutal cold, extracting the ice in one-meter segments and storing them in insulated containers. Engineer James Veale, who took part in the drilling, remembered the moment he held a section of the ancient core: “To hold that in my carefully gloved hands and be very careful not to drop the sections — it was an amazing feeling,” he told the BBC.

The cores were stored in an ice cave before being shipped by boat to Europe. From there, they were transferred in refrigerated vans to the British Antarctic Survey.

Inside the lab, researchers are limited to 15 minutes at a time in the freezer room, due to the extreme cold. Warning lights flash red above the door, and there’s even an emergency tunnel escape hatch in case something goes wrong.

The process will be slow and grueling. For seven weeks, the oldest sections of the core will be melted and analyzed — one step in what could become a multi-year effort to fill in the missing chapters of Earth’s climate story.

“We really are exploring a completely unknown time in our history,” said Dr. Thomas. “What we’re hoping is we’re going to unlock all these amazing secrets.”