From granite to glacier: Rebuilding Antarctica’s Ice Age past

By Jia You

Palisades, New York — They rest side by side on a dark bench table, two coarse linen bags labeled with big, round numbers and letters. Mike Kaplan carefully unties the bag labeled “JRI-14-33” and reaches inside.

“That’s a really nice granite,” the 46-year-old geologist exclaims as soon as he sees the light gray rock, large as his palm and twice as thick. He takes off his glasses to examine it up close. Outside, cherry trees are blossoming under a clear April sky at Columbia University’s Lamont-Doherty Earth Observatory in the Palisades. But inside the dim underground lab, Kaplan is absorbed with the granite and the clues it holds to climate change.

Yes, it’s the same rock used for flooring tiles and posh kitchen countertops. Except it took Kaplan a month of hiking through Antarctica to find this piece of granite — a time capsule from the ancient past, when our planet emerged from the last Ice Age and the massive ice sheets covering much of North America and Eurasia thawed.  Human hunters and gatherers soon started growing their own food. Just like how people bury metal boxes of photos, newsreels and other artifacts for future generations to discover, a melting glacier deposited rock on an island off Antarctica’s northeastern tip some 8,000 years ago — a rock that contained secret messages depicting how the climate changed at the time. Kaplan discovered those messages.

Animation scripted by Jia You, produced by Next Media Animation

Now, it’s up to him and his colleagues at the observatory, geologists Joerg Schaefer and Gisela Winckler, to figure out what exactly happened all those centuries back. But first, Kaplan needs to pry open the time capsule he holds in his hands. And that takes some chemistry, lots of crushed rocks and, finally, thin residual powders carrying the messages from the past, to be decoded at a national laboratory on the opposite side of the country.

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Ancient climate, current crisis

In dark-rimmed glasses, a bright orange sports jacket and brown hiking shoes, Kaplan’s soft-spoken demeanor can mask the endurance it takes to hike in Antarctic conditions. The Bronx native studied geology in college, and discovered a passion for tracking glaciers and climate during a summer research trip to Greenland.

Two decades later, through a collaboration with Argentine scientists funded by the U.S. National Science Foundation, Kaplan and his colleagues turned their attention to the Antarctic Peninsula, the icy continent’s northernmost tip, just about 600 miles across the sea from Cape Horn, the southern tip of South America.

As global temperature rises in recent years, the Antarctic Peninsula has made headlines as one of the fastest warming places on earth, with its ice shelves melting and glaciers accelerating into the ocean. The collapses not only contribute incrementally to rising sea levels, but also give early warnings of alarming climate changes in the region, Kaplan says.

One change that scientists fear is a potential collapse of the massive ice sheet covering west Antarctica, which threatens to push the sea level more than 10 feet higher, says Schaefer, who works with Kaplan on the project. That would devastate millions of lives in coastal areas including New York City, Miami, and New Orleans.

“It’s probably the most vulnerable ice sheet that we have on earth,” he says.

To predict whether and when such a doomsday scenario might occur, climate scientists need to draw a baseline of how climate in the region naturally varies, unaffected by human activities — by looking at how the climate has changed in the past. Kaplan is especially interested in changes during and since the end of the last Ice Age, some 12,000 years ago, when the much larger ice sheets than those we have today collapsed as the Antarctic Peninsula warmed up.

Scientists once thought that such drastic changes occurred on the scale of thousands of years, but they learned that the collapses at the end of the Ice Age actually unfolded in a matter of decades, says Meredith Kelly, a glacial geologist at Dartmouth College who is not involved with Kaplan’s research.

“Those kinds of climate changes, I think, really alarmed scientists,” she says. “Climate changes like that in a decade would really affect people and societies today, so understanding those rapid changes has really been a focus of climate scientists.”

That rings true especially as the earth is warming more now, driven by human dependence on fossil fuels, and the past offers the clearest map for where we might be heading.

But how can scientists reconstruct climate from thousands of years ago? It turns out that glaciers are a good recorder of climate because they are sensitive to even minuscule changes in temperature. And when they start to melt, they leave a record in the rocks they drop as they retreat — time capsules such as Kaplan’s granite.

Like the rising and falling tides, a glacier advances and retreats as its surroundings freeze and warm in cyclical intervals of thousands of years. As a glacier expands, it picks up rocks and sediments along the way and carries them forward. As the temperature rises and the glacier melts, it leaves behind trails of boulders and sediments on the landscape, known as glacial deposits, which can be thousands of miles away from their places of origin. These rocks are easy to spot: The light gray granite in Kaplan’s lab, for example, looks distinct from the dark, coal-like volcanic rocks that make up the island where Kaplan found it.

As these abandoned rocks lie exposed to the air, their transformation into time capsules begins through an interstellar storm of cosmic rays. Cosmic rays are high-energy subatomic particles, accelerated to near light speed when stars explode. Imagine these cosmic rays as pool balls that hurl through space and constantly bombard Earth from all directions. As they enter the earth’s atmosphere, they strike molecules in the upper atmosphere and release other pool balls — subatomic particles called neutrons. The neutrons collide into the surfaces of the rocks on the ground and change their atomic structures, creating a new substance known as Beryllium-10.

The Beryllium-10 carries the secret messages contained in the granite time capsules, the messages that Kaplan and his colleagues decode to figure out how climate changed in the ancient past. That’s because the longer the rocks have been exposed in the air, the more Beryllium-10 they accumulate. So by measuring the amount of Beryllium-10 in a rock sample, Kaplan’s team can deduce when a glacier melted and dropped the rock, and how far the glacier had advanced at that point. Rock by rock, Kaplan and his team can start to piece together a map of changes in glaciers and temperatures in the Antarctic Peninsula during the closing epoch of the Ice Age.

“He’s one of the people … really at the forefront of trying to understand glacial advances and retreats in the past,” says John Chiang, a climate scientist at the University of California, Berkeley.

Finding rocks and moss in Antarctica

Finding a time capsule like Kaplan’s granite is no easy task. The flights themselves required a feat in coordination. To bring the rock back to the lab, Kaplan flew about 5,000 miles from New York to Buenos Aires last January to meet his three Argentine collaborators: geologist Jorge Strelin of the Argentine Antarctic Institute, who planned and led the expedition, and two of his Ph.D. students. It was Kaplan’s second expedition to the island, following a previous trip in 2013.

Together, the team flew to southern Patagonia, Argentina, and waited two days for the weather to clear. Then, a special Argentine military plane used for flying to Earth’s polar regions carried them to a base camp on the Antarctic Peninsula, where the team boarded military helicopters to their field sites on James Ross Island, near the northeastern tip of the peninsula.

For Kaplan, who has explored the interior central Antarctica before, hiking 12 hours a day during the peninsula’s balmy 30-degree Fahrenheit summer can almost seem like a paradise. Survival wasn’t an issue, he says, and food was abundant: Fresh fruit lasted only about two weeks in the cold, but the snowy ground served as a natural fridge for raw meat. At the end of a day, the team would roast chickens and bake pizza in a pantry camp for dinner.

Even so, there were dreary days when wind storms hit camp at 50 miles per hour or more, forcing the team to cancel all plans for the day and secure their tents with all the rocks they could find. During the strongest gusts, they even held the tent up from the inside.

“During a strong storm, all the snow is blowing, sometimes you cannot see your hand right in front of you,” says Fernando Calabozo, a Ph.D. student in geology at the National University of Cordoba, Argentina, who worked with Kaplan. “It can be really frustrating because you got there with a few work plans, so you try to follow a schedule, and the weather is so bad you can’t go outside.”

Besides chiseling out samples from rocks that stood out from their surroundings, the team also looked for fossils on James Ross Island. Whereas the rocks indicate when glaciers expanded the farthest and just started to melt, fossils of shells and whale bones indicate warmer times when glaciers retreated from parts of the island, and seawater covered sections of the landscape. By dating these fossils, Kaplan could glimpse into windows of warm periods on the island as far back as 40,000 years ago.

For the last stop of the expedition, the team flew to the northern tip of the island specifically to find a fossil moss. About two decades ago, a team of European scientists discovered fossils of moss there and dated them as 11,000 years old. The dead plant has important implications for Kaplan’s research because moss only grows in ice-free lakes. So like any good scientist, Kaplan wanted to verify the age of the fossil moss.

“We flew all the way to the northern tip of the island for that moss, and we weren’t sure if we were going to find it,” he says.

Luck was with them. Just 15 minutes after they settled in camp and started looking around, Kaplan, Calabozo and their other team member Juan Presta, spotted a thick brown chunk of hardened dead moss. Cautiously optimistic, Kaplan and his colleagues spent the rest of the day digging around where they found the plant, until they found it pressed between two sediment layers that were thousands of years old, concrete evidence that the moss was a fossil.

“That was a really nice finding,” Kaplan says.

At the end of the expedition, the rocks and fossils were shipped from Antarctica to Argentina and then to the Lamont-Doherty Earth Observatory, in five Fed Ex boxes weighing 200 pounds. A month later, Kaplan would open one of those boxes and take out a coarse linen bag marked “JRI-14-33.” As he reaches inside for a piece of granite, the quest to open the time capsule begins.

Cracking open a time capsule

Bringing the granite and other rocks back from Antarctica is just the first step in recreating the Antarctica’s past climate. To actually date how long ago glaciers started melting and leaving the rocks exposed to air, Kaplan and his team still needs to know how much Beryllium-10 is contained in the rocks.

To find the Beryllium-10, the secret messages contained in the time capsules, the researchers first need to isolate quartz, the hard, transparent minerals in granite that sparkle under light. That’s where the Berylllium-10 hides.

The process begins with what Kaplan calls the “dirty work” – sawing, crushing, grinding and sieving the rocks into fine particles, which are shaken in acids to obtain pure quartz. Then, lab technicians and students dissolve the pure quartz, and uses chemicals to remove other elements and isolate Beryllium-10. If the process sounds complicated, it’s because it is — it can take a skilled technician up to two months to process a batch of eight to ten samples.

At the end of the process, the researchers fill solid Beryllium-10 powders into a thumb-sized, bullet-shaped stainless steel capsule and send it across the country to the Lawrence Livermore National Laboratory in California, one of a handful labs around the world capable of measuring the exact amount of Beryllium-10 contained.

Once the lab sends the results back to Kaplan, he will conduct the detective work of deducing how long the rocks have been exposed in the air, and thus when the glaciers on James Ross Island melted and deposited the rocks, and thus what the temperature in the Antarctic Peninsula must have been at that time. One data point followed by another, he will plot out a timeline of how climate in the region changed as it emerged from the last Ice Age.

For now, Kaplan’s hands are full. It would take a few years for him to work through the five Fed Ex boxes from his last expedition, in addition to several boxes from the 2013 expedition.

Yet he’s already planning to go back. Just a few weeks ago, with other Lamont scientists, Kaplan applied for funding for yet another trip to the Antarctic Peninsula, this time to stretch his time machine even further back. On his last trip, he and his Argentine colleagues found much older glacial deposits, sandwiched between layers of volcanic rocks, and ancient residues from the sea bottom. Geologists have well-established methods for dating volcanic rocks, which would allow Kaplan to date the old glacial deposits more accurately. Already, the volcanic layers and fossil shells they found indicate that those rocks could be millions of years old.

“It’s much older than anything we’ve worked on in this present project,” he says.

There’s an old Chinese saying that history is a mirror to the future. And Kaplan sees himself as a historian. “I’m interested very much in human history, and I figured it’s probably not a coincidence that I look at time periods in the geologic past,” he says.

He opens a notebook and sketched the granite’s outline on the page. Then he draws nine dots inside the outline in a three by three matrix, and patiently measures the thickness of the rock at each spot. Nine measurements to obtain the rock’s average thickness, which is just one number used to calculate its exposure to air. Back at his office, Kaplan has a shelf of close to 40 yellow- and red-covered notebooks, his field notes over the past two decades.

In the next few months, the granite will be ground and reduced to quartz, then to white powders in a stainless steel capsule, then to an age, then to a number on a graph or in a model. And then, with hundreds of rocks like the granite, the ancient Antarctic Peninsula would come alive: glaciers expanding and retreating over centuries, reacting to dynamic changes in the environment as they are now and far into the future.

Kaplan writes down the last thickness number and closes the notebook. Another day’s work done in writing the climate history of the Antarctica.

Photo at top: A collaborative research project between Argentine and U.S. scientists in the Antarctic Peninsula traces ancient climate in the region. (Mike Kaplan/LDEO)