Collaged illustration of an ice core drill with an inset portrait of Willi Dansgaard holding an ice core sample.

Brian Williamson | VOA

Chapter 1

Drilling for Answers

Scientists are drilling through more than two-and-a-half kilometers of ice, searching for clues about the causes and consequences of climate change.

East GRIP is a research station on the move. Every day, the entire site slides about 10 centimeters northeast.

The camp sits atop the Northeast Greenland Ice Stream, a relatively fast-moving strip of ice within the ice sheet. The stream feeds three glaciers that spill ice into the Greenland Sea, one of the Nordic Seas.

Scientists need to know more about what makes the ice stream move, because how fast those glaciers discharge their contents into the Nordic Seas may have more of an impact on sea level rising than the steady drip of melting ice.

“We can understand melting. It’s a nice and linear thing. The warmer it gets, the more it melts,” said University of Copenhagen glaciologist Jørgen Peder Steffensen, who oversees the project.

“The trouble is, if something odd is going on at the base of these ice streams … then it can upset the entire apple cart,” he said. “All of a sudden you (could) have an unstable ice sheet that might break away, not over several centuries, but over a couple of decades. And that would be disastrous.”

What happens in Greenland may also be happening with Antarctica’s ice streams. And the southern continent contains much more ice than Greenland.

So the East GRIP team is drilling to the bedrock seeking clues as to what makes the ice stream beneath them move. Is meltwater lubricating the bottom of the ice sheet? Is there something special about the ground on which the stream is sliding? Or is it moving because of forces at work in the middle of the ice? Those forces may reveal themselves in how the borehole bends as the drill cuts through.

Four decades on ice

With thinning hair, a sandy beard and a predilection for a pipe, Steffensen is in his fourth decade drilling holes in polar ice.

His first trip to Greenland, in 1980, came on short notice.

It was a July afternoon shortly after Steffensen graduated from college. The head of an ice-drilling mission called to offer him a job.

It was a Friday. The eight-week expedition was leaving Tuesday. The caller gave Steffensen a half-hour to cancel any plans he had for the summer.

Steffensen did. Because the caller was Willi Dansgaard, the Danish scientist who essentially invented ice-core drilling as a way to study past climates.

In the early 1950s, Dansgaard discovered that rain carries a record of the temperature at which it fell encoded in its chemical makeup. He figured that he could read temperatures deep into the past if he could find a supply of “old water.”

“Where do you find old water? In glacier ice. And where do you find old glacier ice? In Greenland,” he wrote in a 2005 memoir (PDF).

The snow that falls on central Greenland rarely melts. For roughly 100,000 years, snowstorm after snowstorm piled up the snow, forming an ice sheet more than 3 kilometers thick in spots.

That ice contains an encyclopedic record of the climate in which it formed.

Temperature data is just the beginning. Frozen inside the cores are tiny bubbles of ancient air that can reveal concentrations of greenhouse gases from the distant past. Trapped dust particles tell of the force and frequency of storms that blew particles onto Greenland’s snowy face from far away. Volcanic eruptions left their mark in acidic ash.

Ice cores have provided some of the most valuable data about past climates to scientists seeking answers about the causes and impacts of today’s global warming.

Fragile ice

But these icy records are extremely fragile.

Hundreds of meters below the surface, the ice is under pressure 60 times greater than at the surface. The temperature is minus 30 degrees Celsius.

But in the underground snow cave at East GRIP, it’s only minus 10.

When the core comes up to the surface, the trapped air expands. You can hear the ice crack, Steffensen said. Gases escape. Contaminants get in.

“It’s really, really terrible as a glaciologist to watch this perfect core disintegrate before your eyes,” he added.

Researchers can’t do much about the pressure. But they can control the temperature.

“It sounds completely ridiculous and backwards, but actually, we mounted a freezer unit in a snow cave inside the Greenland ice sheet,” Steffensen said.

The ice cores spend a year in East GRIP’s subterranean freezer above the Arctic Circle, relaxing at minus 30 C. That has kept them from cracking.

“People say, ‘It must be cold up there,’” he added. “Yes, but it’s not cold enough.”

Why they drill

The snow that falls on central Greenland rarely melts. For roughly 100,000 years, snowstorm after snowstorm has piled up, forming an ice sheet more than three kilometers thick in spots.

17th-18th Century: Little Ice Age in Europe. Temperatures in the Northern Hemisphere were roughly 0.5-1 degree C colder than today. The Baltic Sea froze over.

100 meters

The ice in the cores contains a huge amount of information about the climate in which it formed. With careful analysis, scientists can capture data about temperature, elevation, greenhouse gas composition and more.

500 m

Each drop of water contains a clue about its past. By analyzing oxygen isotope ratios, scientists can tell the temperature of the cloud from which it fell. Heavier isotopes condense at lower temperatures.


Seasonal shifts in isotope ratios give a year-by-year record of past climates.

9,000-4,000 years ago: Changes in the Earth's orbit warm the planet. Human civilizations begin. Greenland was up to 2 degrees warmer during this period.


This is a key target of the East GRIP team. Scientists want to know how much greenhouse gas the Arctic tundra released as it thawed. As the planet warms up again, these natural releases could complicate human efforts to fight climate change.

1000 m

1500 m

12,000 years ago: As the last Ice Age ends, ice core records show Greenland was about 15 degrees C colder than today.

Annual bands in the ice form from seasonal changes in snowfall and dust accumulation (though these get harder to see deeper in the core).

2000 m

Volcanic dust from well-known eruptions — like the one that buried Pompeii — serve as signposts in the historical record.

When they hit bedrock, the East GRIP team hopes to find clues as to why this section of the ice sheet is sliding toward the sea. The speed of sea level rise will depend largely on how fast ice streams like this one move.

2500 m