COVER STORY

The Ice Detectives

Columbia researchers go to the ends of the earth to crack the coldest case of all.

by Paul Hond Published Fall 2017
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Ice is slippery quarry. Always moving, never sleeping, it vanishes and reappears, grows and shrinks, advances and retreats. It builds up over periods of geological time and can crumble in the wink of a polar summer. Today, earth’s great ice sheets sprawl over Antarctica and Greenland, the vast, sliding bodies polished by the harshest conditions on the planet, layered with millennia of snowfall packed more than two miles thick in spots: a colossal architecture moving constantly under its own weight, sloping toward the sea.

Robin Bell ’89GSAS is watching. Bell, a geophysicist at Columbia’s Lamont-Doherty Earth Observatory and one of the world’s leading polar investigators, has been tracking ice for thirty years: inspecting it, measuring it, drilling it, flying over it, spying under it, peering through its layers, sleeping on it, skiing on it. She has coordinated ten expeditions to Antarctica and Greenland, which between them hold more than 99 percent of the world’s frozen fresh water.

That ice is transforming before her eyes.

“There are three lines of evidence that the ice sheets are changing,” Bell says. “One: in some places they are flowing twice as fast as they were twenty years ago — a mile a year in the last decade, two miles a year now. Two: their elevation has dropped. Three: they are losing mass, which we can tell from satellite measurements.”

Melting ice, together with the expansion of oceans due to warming (warm water is less dense), is raising sea levels faster than scientists had expected. And while the earth has a natural climate cycle of warming and cooling that repeats every hundred thousand or so years, the big difference this time is the human factor. Since the Industrial Revolution, we have pumped more than five hundred billion tons of heat-trapping carbon dioxide into the atmosphere. Scientific consensus holds this activity to be the main driver of the warming — and melting — that has drowned islands in the Pacific, caused unusual weather events across the globe, and placed coastal areas, home to hundreds of millions of people and trillions of dollars of property, under increasing threat of devastation.

So Bell has been on scientific stakeout. She and her colleagues in Lamont’s Polar Geophysics Group, including Marco Tedesco and Jonathan Kingslake, are working to decipher the nature of the planet’s ice — its makeup, its mechanics, its behavior. They are building a character profile of their subject, drilling down for clues, extracting information. The goal is to use this data to improve computer models and projections for sea-level rise, for the benefit of the engineers, city planners, insurers, ecologists, business owners, government agencies, and residents whose destinies are linked, by the ocean, to the least-known topography on earth.

How high will the water go? In 2013, the United Nations Intergovernmental Panel on Climate Change issued a worst-case estimate for sea-level rise of three feet by 2100. In 2015, NASA said it expected a minimum of three feet. And in 2017, the National Oceanic and Atmospheric Administration stated that end-of-the-century sea-level rise could reach as high as 8.2 feet, enough to engulf waterfront cities around the world.

But Bell, acknowledging that our understanding of the ice is still limited, demurs on the specifics of future sea-level rise. “My belief is that we don’t know yet,” she says. “That’s because we don’t know what’s going on underneath the ice. You might think the land underneath is flat, but it’s not: it’s a very rich environment, with mountains and lakes, and places that can funnel in warm water.

“We need to know what happens when warm water comes into contact with the ice sheet, as well as what happens as warm air creates more surface meltwater.” The only way to figure it out, Bell says, is to get “up close and personal” with the subject. This case can’t be solved from afar.

“In the last hundred years, sea level has gone up eleven inches. In the next hundred years, will it go up to your waist or over your head?

“That,” Bell says, “is what we’re trying to pin down.”

The Rosetta Code

Growing up in New Hampshire in the 1960s, Bell liked to watch the small animals in her backyard. She was captivated by their habits. For her, nature overflowed with wonders. Her favorite TV show was The Undersea World of Jacques Cousteau. As a kid she wanted to be a marine biologist.

Then, between high school and college, she took some classes and learned about physics and plate tectonics. She thought: here is the key to how the planet works.

The creatures faded from the garden of her imagination. She saw rock now. Water. Motion. Reaction. The white chalk of formulas scratched on green slate.

She gravitated to geophysics, focusing on the oceans, until her curiosity swept her toward the ice, to Antarctica, home to almost 90 percent of the earth’s frozen water — “a place on our planet yet to be explored and understood,” Bell says.

Bell made her first Antarctic expedition as a geophysics doctoral student in the late 1980s. Much has changed since then. For one thing, the planet has gotten warmer: sixteen of the seventeen hottest years on record (record-keeping began in 1880) have occurred since 2000. That’s an especially salient fact when you’re chasing ice.

For the last two years, Bell’s team has explored the Ross ice shelf, the world’s largest piece of floating ice. Ice shelves are platforms of glacial runoff that extend from the land-based ice sheet onto the water, cantilever-like, often accreting to the size of small countries. (The Ross is about the size of France.) They act as doorstops for the glaciers, restraining them from the sea. The collapse of an ice shelf doesn’t directly contribute to sea-level rise (just as melting ice cubes don’t raise the level of your drink); rather, their disintegration allows the glaciers to flow unchecked. And the Ross is the biggest doorstop of them all. In 2000, it produced, or calved, a 4,200-square-mile iceberg, the largest ever recorded.

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