A Heat Shield for the Most Important Ice on Earth

On a clear morning in late March, in rural St. Elmo, Minnesota, I followed two materials scientists, Tony Manzara and Doug Johnson, as they tromped down a wintry hill behind Manzara’s house. The temperature was in the high thirties; a foot of snow covered the ground and sparkled almost unbearably in the sunlight. Both men

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On a clear morning in late March, in rural St. Elmo, Minnesota, I followed two materials scientists, Tony Manzara and Doug Johnson, as they tromped down a wintry hill behind Manzara’s house. The temperature was in the high thirties; a foot of snow covered the ground and sparkled almost unbearably in the sunlight. Both men wore dark shades. “You don’t need a parka,” Johnson told me. “But you need sunglasses—snow blindness, you know?” At the bottom of the hill, after passing some turkey tracks, we reached a round, frozen pond, about a hundred feet across. Manzara, a gregarious man with bushy eyebrows, and Johnson, a wiry cross-country skier with a quiet voice, stepped confidently onto the ice.

Manzara and Johnson wanted me to see the place where, in a series of experiments, they had shown that it was possible to slow the pond’s yearly thaw. Starting in the winter of 2src12, working with a colleague named Leslie Field, they had covered some of the ice with glass microspheres, or tiny, hollow bubbles. Through the course of several winters, they demonstrated that the coated ice melted much more slowly than bare ice. An array of scientific instruments explained why: the spheres increase the ice’s albedo, or the portion of the sun’s light that the ice bounces back toward the sky. (Bright surfaces tend to reflect light; we take advantage of albedo, which is Latin for “whiteness,” when we wear white clothes in summer.)

At the edge of the pond, Manzara and Johnson started to reminisce. Originally, they had applied glass bubbles to a few square sections of the frozen pond, expecting that the brightest ice would last longest. But they found that, beneath the pond’s frozen surface, water was still circulating, erasing any temperature differences between the test and control sections. In subsequent years, they sank walls of plastic sheeting beneath the pond’s surface, and the coated ice started to last longer. At first, Johnson manually measured the ice thickness by donning a wetsuit and snowshoes, tying a rope around his waist, and walking onto the frozen surface with a drill and a measuring rod; he was relieved when they figured out how to take sonar measurements instead. Manzara directed my gaze to two trees on opposite shores. “This is where we set up the flying albedometer,” he said. An albedometer measures reflected radiation; theirs “flew” over the lake by way of a rope strung between two pulleys. By this point, I had been staring at the ice and snow for almost an hour, and my vision started to turn purple-pink. I blinked hard as we headed inside.

Manzara, Johnson, and Field want to prove that a thin coating of reflective materials, in the right places, could help to save some of the world’s most important ice. Climate scientists report that polar ice is shrinking, thinning, and weakening year by year. Models predict that the Arctic Ocean could be ice-free in summer by the year 2src35. The melting ice wouldn’t just be a victim of climate change—it would drive further warming. The physics seem almost sinister: compared with bright ice, which serves as a cool topcoat that insulates the ocean from solar radiation, a dark, ice-free ocean would absorb far more heat. All of this happens underneath the Arctic summer’s twenty-four-hour sun. But the fragility of the Arctic cuts both ways: as much as the region needs help, its ecosystems are sensitive enough that large-scale interventions could have unintended consequences.

That afternoon, Field arrived at Manzara’s house from California, where she runs a microtechnology-consulting company and teaches a Stanford course on climate change, engineering, and entrepreneurship. Like an old friend, she let herself in and called out hello. Field has let her shoulder-length hair go completely silver, “in solidarity with the Arctic,” she joked; when we sat down together, it was obvious that all three scientists relished engineering challenges, from applying the glass bubbles (shake them out of giant cannisters? spray them from a pressure pot?) to measuring their effects. They are an inventive bunch. Both Johnson and Manzara were senior scientists at 3M: Johnson, a physicist, worked on advanced materials such as a high-capacity transmission cable, to stabilize electrical grids; Manzara, an organic chemist, focussed on energetic materials, making ingredients for flares and rocket propellants. Field holds more than sixty patents; Johnson around twenty; Manzara around twelve.

Last year, Johnson, Manzara, Field, and other collaborators published a paper about their work at the test pond in Earth’s Future, a journal of the American Geophysical Union. It described how they segmented the pond, applied a thin layer of glass bubbles on one side, and set up instruments to measure water temperature, ice thickness, weather, and long-wave and short-wave radiation. Albedo measurements range from zero, for perfect absorption, to one, for mirrorlike reflection; the bubbles raised the albedo of late-winter pond ice from src.1-src.2 to src.3-src.4. After a February snowfall, they wrote, it was impossible to see any difference between the sections. But in March the snow thinned to reveal two distinct regions of ice, which melted at different rates as the days warmed. When the bare ice was gone, nine inches remained under the glass bubbles.

An aerial view of the glass-bubble-covered ice, at left, and the bare ice.Photograph by Doug Johnson

These results validated the notion that the glass bubbles could withstand harsh winter weather and extend the life of ice. And although a freshwater pond in Minnesota is not a perfect analogue for Arctic sea ice, the authors argued, glass microspheres showed potential. “Ultimately, if policy decisions were to be made that it was appropriate to apply this localized ice-preserving approach on a local or regional scale, this method of surface albedo modification may serve to leverage albedo feedback loops in a low-risk, beneficial way to preserve Arctic ice,” they wrote.

The paper imagined deploying the glass bubbles in a few strategic places. The Beaufort Gyre, for instance, north of Alaska and Canada, serves as a nursery for sea ice. “The circulation patterns there would help you spread the materials around,” Field told me. First-year ice is darker and thinner, and therefore vulnerable; the glass bubbles could help it survive and grow into thicker, brighter ice. Field also envisioned applying the bubbles in the Fram Strait, east of Greenland and west of Svalbard, which traps ice floes when it freezes over, helping them to survive longer. “There’s so much ice export there. A flow restrictor would be a good thing,” Field said.

In the race to save the cryosphere, as scientists call the world’s frozen reaches, protecting icy bodies of water will not be enough: the water locked on land, in glaciers, could devastate ecosystems and lower Earth’s albedo if it melts. And so, this winter, Johnson and Manzara constructed four “glaciers” on Manzara’s property. We went to see them with Field, stopping on the way to sample sweet sap from one of Manzara’s maple trees.

Already, through the course of the day, the snow had softened: instead of crunching across the top, we sank to our shins with each step. The glaciers sat, like ten-foot-square garden beds, behind a wire fence meant to keep out turkeys and deer. Glass bubbles have proved surprisingly effective on the flat surface of the pond, Manzara explained, but are not suited to the flowing curves of glaciers. “On a sloped surface, they tend to run downhill very quickly as soon as the top layer gets to be at all liquid,” he told me. Instead, they were testing white granules commonly used in roofing, which are heavier and irregular. But would they protect the ice as well as the spheres—and would they stay in place long enough to save glaciers?

No amount of glass spheres or roofing granules will reverse climate change. Only a rapid global shift away from fossil fuels is likely to achieve that. But in a place like the Arctic, which is warming four times faster than the rest of the planet, and where the end-of-ice tipping point hangs like the Sword of Damocles, such an intervention could offer a precious lifeline: time. What kind of progress could the world make if the emergency receded by a few years? “You only need to treat a small portion of the Arctic to get a big impact on the global climate. That’s the big picture,” Johnson said, describing his group’s modelling. “You can get twenty-five years longer to keep the ice.”

In 2srcsrc6, Field went to see Al Gore’s climate-change documentary “An Inconvenient Truth.” She remembers leaving the theatre with two feelings: panic, and the need to do something. She kept thinking of an image she had once seen—a truck barrelling toward a screaming woman who’s standing in front of a child. “That’s what I felt like—like the Mack truck was coming for my kids,” Field told me. She also thought about the idea, communicated in the film, that the Arctic Ocean had enormous leverage in the climate system. “That disappearing ice, that reflectivity that we’ve had, that’s been doing us this gigantic favor of reflecting sunlight away, it’s disappearing—and that makes this positive-feedback loop,” she said. As an engineer, she knew that a positive-feedback loop, in which a change begets more of the same change, was something special: an opportunity for a small, strategic input to have a larger impact.

Field started experimenting with albedo on her front porch. She filled buckets with water and various would-be heat shields, and rigged them with inexpensive hardware-store thermometers. Her husband, a fellow-engineer, thought the tests were overly simplistic. “I’ve learned to listen to his arguments, but not to let them stop me,” Field told me. Plastics seemed unsuitable—they’re derived from petroleum, and a stint in the oil industry had convinced her that “you just have to respect the toxicity” of petrochemicals—but she tried some anyway. She tried hay and daisies. “They were both terrible,” she said. She tried cotton pads, baking soda, diatomaceous earth, searching for a material with the right properties—something reflective and nontoxic, that didn’t absorb heat, with an open texture to allow evaporative cooling. In 2srcsrc8, she formed Ice911, a nonprofit, to fund her experiments.

Early in her research, Field learned that 3M was one of several companies that manufacture glass microspheres by the trillions. Microspheres make automotive parts lighter and reduce the density of wood composite, making it easier to nail; if you’ve driven in the dark, you’ve seen the unique way the material scatters light, in the reflective paint that’s used for lane lines. In November, 2src1src, a professional acquaintance introduced Field to Johnson, who invited her to give a talk at 3M’s Midwest headquarters, the home of Scotch Tape, Post-it, and many cleaning, building, and business supplies. On the way, she saw a rainbow and took it as an auspicious sign. During her talk on Arctic ice loss, which about twenty scientists attended, Field described a dilemma: she knew that the glass bubbles needed to be tested in the field, but she also knew that it would be difficult to get permission to conduct a scaled-up experiment. At the end of her presentation, Manzara approached her and offered a solution—they could use his pond, which is on private land.

A 3M policy allowed scientists to spend fifteen per cent of their work time on personal projects, and Johnson, Manzara, and Field soon began testing different glass bubbles on the pond. They contracted with an environmental laboratory to feed the glass bubbles to one bird species and one fish species, and the lab did not report any harmful effects. The team reasoned that the microspheres were safe because they were almost entirely silica, a mineral that is abundant in sediment, rocks, and the ocean. “It’s something we’ve evolved with,” Field argued. “If you look at your vitamins, you may find that some of them have a silica binding agent. It’s about as safe as you can get.” Microspheres also have the advantage of already existing: when tackling a problem that needs to be solved within ten or twenty years, there’s hardly time to invent and mass-produce something entirely new. “These are relatively inexpensive, and there are manufacturers,” Field told me.

In 2src15, Field gave a talk at NASA’s Ames Research Center and met its associate director, Steven Zornetzer, a former neuroscientist interested in climate protection. “Leslie’s insight was that, if we can use some kind of material to really leverage the importance of ice in the Arctic during the summer, we could prevent that additional absorption of solar radiation,” he told me. Zornetzer, a hiker and environmentalist, joined the small team at Ice911 as executive director to build up the organization’s infrastructure. Covering up to a hundred thousand square kilometres of Arctic sea ice, Zornetzer told me, would cost one to two billion dollars per year; Johnson estimated that coating Himalayan glaciers would cost anywhere from one to thirteen billion dollars per year. The group knew that their approach was not a substitute for the larger undertaking of cutting climate pollution to near-zero—but, like doctors in the early days of the coronavirus pandemic, they were raiding the medicine cabinet. They wanted to find remedies that were already out there and which might buy time for new treatments to be developed.

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