Polar Geoengineering Experiments Bet Big on Freezing Arctic Ice

Scientific American

16-05-2025

Refreezing the melting sea ice in the Arctic is more complicated than you would think. The U.K. is funding geoengineering experiments like this one to curb the effects of climate change.
By , Alec Luhn, Fonda Mwangi, Alex Sugiura & Jeffery DelViscio
This story was produced in partnership with the Pulitzer Center's Ocean Reporting Network.
Rachel Feltman: For Scientific American 's Science Quickly, I'm Rachel Feltman.
You don't have to pay much attention to the news to know that climate change is causing Arctic sea ice to melt—and to understand that this is a huge problem. Ice reflects sunlight, which helps keep cold places cold. Warmer weather means less ice, but less ice means more heat from the sun, which means it gets warmer, which means there's less ice—and the sea level keeps rising and rising.
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It would be great if we could cut this problem off at the source by dropping our greenhouse gas emissions, but we're not exactly making great progress on that front. In the meantime what if we could just make more ice?
It might sound silly, but some folks in the polar geoengineering space are making a very serious attempt to do just that.
To get the inside scoop I'm handing the reins over to Pulitzer Center ocean reporting fellow Alec Luhn. He's the author of a feature on the subject in Scientific American 's June issue, and today he's going to take us along on a trip to the Arctic.
[CLIP: Snowmobile engine starting.]
Alec Luhn: I'm snowmobiling out onto the sea ice from the Inuit village of Cambridge Bay in Canada's Arctic Archipelago. It's –26 degrees Celsius. That's –15 degrees in Fahrenheit. The blasting wind makes it feel far colder. My goggles are freezing over, and my thumb is getting numb on the throttle. But this is actually warm for Cambridge Bay in February. It's been the warmest winter in 75 years, and the temperature at the North Pole even briefly went above freezing.
In front of me a local Inuit guide is towing a sled full of team members from the U.K. company Real Ice to a point about seven kilometers [roughly 4.3 miles] from town.
Scientists say as early as the 2030s the Arctic ice cap could start melting away completely in the summertime, raising temperatures around the globe. Real Ice hopes to stop that by artificially freezing more sea ice. It's one of several geoengineering projects trying to save the world's glaciers, ice sheets and sea ice.
Some scientists think it's ridiculous or even dangerous, but Real Ice co-founder Cían Sherwin says we no longer have any option but to try.
Cían Sherwin: So right now we're about to start drilling the—that 10-inch [25.4-centimeter] auger hole for the pump.
[CLIP: Cían Sherwin drills into the sea ice.]
Luhn: Cían was part of a student group at Bangor University in Wales that built a 'reicing machine' after they saw a TV documentary about the melting Arctic. In 2022 he co-founded Real Ice to try it on a larger scale.
The ice outside Cambridge Bay is more than a meter [approximately 3.3 feet] thick. Cían drills a hole in it with a long battery-powered auger. If you've ever been ice fishing, you've seen this kind of tool. It looks kind of like a jackhammer, only with a giant rotating screw rather than a chisel at the end.
Inuit guide David Kavanna widens the edges of the hole with an ice saw, and the team puts a wooden box around it. Cían lowers an industrial pump with a long hose through the hole. He plugs a cable into a battery pack, and seawater starts pouring out of the hose, creating a brilliant blue pool on the sea ice.
Sherwin: Where that flow rate isn't as strong, the ice—or the water acts almost like lava, becoming thicker in viscosity, and ice formation starts to begin almost instantly.
Luhn: Sea ice freezes from below, where there's water that's just under zero degrees C [32 degrees F]. But once the first layer of ice forms it partially insulates that water from the freezing air above, which can be as cold as –50 degrees C [–58 degrees F]. So the thicker the ice gets, the slower it grows. Real Ice is trying to bring the water up to the cold air by pumping it on top of the sea ice.
After about three hours the team comes back to take the pump out. The pool of water has congealed into an electric blue slush, like a gas station Slurpee.
Sherwin: So by the time we return here now, tomorrow morning, this will already be frozen.
Luhn (tape): New sea ice?
Sherwin: New sea ice—or a new layer on top of the sea ice.
Luhn: Releasing small particles to block sunlight is probably the most common geoengineering idea. It's also highly controversial because it could affect weather, like rainfall. Mexico banned solar geoengineering after an American firm released balloons full of sulfur dioxide there. A city in California recently halted an experiment spraying sea-salt particles into the air.
In May the U.K. allocated about $75 million to geoengineering research, becoming one of the first countries to fund outdoor experiments in this field. One experiment will launch balloons to test mineral dust that could someday be released into the atmosphere to block sunlight. Another two will develop nozzles to spray sea-salt particles, including potentially over Australia's Great Barrier Reef.
But the largest grant in the British program, about $13 million, went to a research group that includes Real Ice. It also includes the Dutch company Arctic Reflections, which has been testing giant pumping platforms to thicken sea ice in Svalbard [Norway] and Newfoundland, Canada.
Polar geoengineering trials have been moving forward in other places, too. A U.S. nonprofit has been scattering tiny white clay granules to reflect more sunlight away from glaciers in Iceland and the Himalayas. And a Scandinavian project has been testing materials for huge underwater curtains to try and stop warm water from reaching the underside of Antarctic glaciers and melting and collapsing them.
If it works, polar geoengineering like sea-ice thickening could affect the entire Earth. Arctic sea ice is like a big mirror, reflecting up to 90 percent of the sun's radiation back into space when it's covered in snow. But ocean water absorbs 90 percent of sunlight. The more ice melts, the more ocean water warms. That heats up the planet—and melts even more ice.
The thick sea ice that lasts year round has shrunk about 40 percent in the last four decades. If it starts melting away completely in the summertime, global temperatures could rise an extra 0.19 degrees C [roughly 0.34 degrees F] by 2050.
Last winter real ice thickened about 250,000 square meters [almost 2.7 million square feet] of sea ice. In the winter of 2027–28 the company plans to thicken 100 square kilometers [about 38.6 square miles] as a demonstration. If that works, the team hopes it could scale up to eventually keep Arctic sea ice from disappearing in the summer.
Sherwin: Targeting an area roughly a million square kilometers [about 386,100 square miles]across the entire Arctic region could be enough to help prevent the loss of sea ice.
Luhn: On the one hand that's small: it's one fifth of how much ice is currently left in the summertime. On the other hand it's enormous: the size of Texas and New Mexico combined. Real Ice says it could be possible. All they'd need is half a million underwater drones.
Real Ice has been working with the Sant'Anna School of Advanced Studies in Italy to develop a two-meter-long [about 5.6-feet-long] automated drone. In a computer rendering the drone has a pipe that folds out like a pocket knife. The pipe would be heated so it could melt through the sea ice from below and then pump water on top of it. Real Ice hopes to test a prototype by the end of the year.
The idea is that something like 20,000 technicians will be working on onshore and offshore platforms, swapping out batteries so the 500,000 drones can keep thickening sea ice. The old batteries would have to be recharged with wind power or green ammonia or hydrogen. That would have to be brought in by ship, since the Nunavut region's grid is all diesel.
Andrea Ceccolini: Half a million drones might seem like a large figure.
Luhn: That's Andrea Ceccolini, a wealthy tech investor who is co-CEO of Real Ice.
Ceccolini: We produce, globally, over 90 million cars every year. We also produce more than 40 million e-bikes.
Luhn: But only about a few dozen underwater drones have ever been deployed under polar ice, such as the U.K.'s $1.3 million Boaty McBoatface. The closest equivalent to what Real Ice is proposing would probably be the 3,800 Argo floats deployed around the ocean. And these floats only need enough power to measure temperature and salinity as they drift with the ocean currents.
Craig Lee is a University of Washington oceanographer who helped develop low-power Seaglider drones that operate under polar ice. I spoke with him on video call after I got back from Cambridge Bay. He says it wouldn't be feasible to swap out thousands and thousands of batteries every day in one of the harshest environments on Earth.
Craig Lee: You'd need a revolution in how the vehicles are powered. That's not gonna happen on any battery that we currently use today.
Luhn: He says keeping that many remote drones in good repair would also be impractical. Right now the only way to deliver equipment to Arctic communities like Cambridge Bay is on a ship that comes through once a summer when the ice melts or by propeller plane.
The village lies in the heart of the Northwest Passage, the infamous sea route between Europe and Asia that took sailors 400 years to successfully navigate. The first thing I saw when I landed at the one-room airport was a stuffed musk ox, which looks like a bison with shaggy black fur, and a plaque about the doomed 1845 expedition of John Franklin.
One of Franklin's two captains was confident they could get through the passage in less than a year. Instead their ships became trapped for a year and a half in the polar ice that surges down the channel toward Cambridge Bay. The men abandoned the vessels, and eventually all 129 of them died of cold, starvation or disease. Some resorted to cannibalism.
With sea-ice thickening Real Ice is also entering uncharted territory. I wondered if abandoned ice making drones would someday join Franklin's ships at the bottom of the passage.
The first big question is salt. When seawater freezes, the salt in it is ejected, and pockets of brine form on the ice's surface. Salt lowers the melting point of ice, which is why trucks spread salt on the roads in winter. If pumping seawater means that more salt remains on the ice during the summer, it could accelerate the melt and make the ice thickening largely pointless.
So far that doesn't appear to be happening. Out on the ice Simon Woods, a London software entrepreneur who co-founded Real Ice with Cían, attaches a long red barrel to a drill and bores into the ice. He pulls out an ice core as long and thick as his arm and holds it up to the low sun.
Simon Woods: Can you see them?
Luhn (tape): Yeah, those kinda little—just little lines in the ice.
Woods: Yeah, those are brine channels.
Luhn: The brine appears to be eating through the ice, returning the salt to the ocean.
Snow is another wild card. The water pumped by Real Ice floods the crusty snow that covers the sea ice, freezing it solid. Have you ever wondered how Inuit people were able to live in igloos? That's because snow is actually a really good insulator.
Simon drills through the ice and drops in a measuring tape with foldout brass arms to measure its thickness. The team has added 20 to 30 centimeters [about 7.9 to 11.8 inches] of ice by pumping water and freezing the snow. But that's not the end of the story.
Woods: But what we're hoping to see later in the season is that that exposing [of] the surface so that there's less, less snow cover means that it's less insulated, improves the conductivity of the whole stack so we get ice growth from below. That's the really efficient part of the process.
Luhn: At the same time snow is a better mirror than ice. Bare ice reflects about half as much solar radiation back into space as ice covered in snow. Real Ice needs the snow to accumulate again in the spring or the company's process could increase the melt rate.
The animals living on the ice also need that snow to come back. Brendan Kelly, a marine biologist at the University of Alaska Fairbanks, used to be a polar science adviser to the Obama administration. Now he's advising Real Ice on possible consequences its plans could have for the ecosystem.
With Brendan I walk along a low ridge where two massive pieces of ice are pushing together. We see a patch of yellow snow—you know what that means. A few meters further is a dry green turd. Then we come to a small pit dug in the snow. These are traces of an Arctic fox, the fluffy white cousin of the red fox most of us know.
[CLIP: Brendan Kelly's and Alec Luhn's footsteps crunch in the snow.]
Brendan Kelly: The fox has come in, marked and dug. He thought something was there.
Luhn: That something might've been a ringed seal. These animals dig layers under snow drifts to protect their fuzzy white pups from predators. The mother seal leaves her pup in the lair while she dives for fish and crustaceans. Arctic foxes and polar bears often try to root out the pups for dinner.
Brendan is trying to understand how flooding the snow for sea ice thickening could impact seal reproduction.
Kelly: Birthing won't happen until April. So it's just a question: If you came into an area and you flooded it, say, in February, would enough snow accumulate again by birthing time for them to maintain lairs?
Luhn: Foxes and polar bears dig snow dens, too, so they could also be affected if there isn't enough snow buildup. But the alternative doesn't look great either, given that the sea ice they live on is melting. The Arctic is warming about four times faster than the planet as a whole.
Kelly: We've done some modeling, my colleagues and myself, and project that about 70 percent of the suitable habitat in terms of snow cover in the Arctic will be gone by the end of the century, so massive loss of habitat.
Luhn: The Inuit residents of Cambridge Bay also rely on the sea ice for their survival. There's no highway here, only the ice. People depend on it to go hunting and fishing. Only about one third of the food they eat is store-bought.
When the ice recedes in the summer the Inuit fish the arctic char that run into the bay from lakes and streams. When the ice returns in the fall they hunt the caribou that cross it on their annual migration. They also hunt ringed seals and musk ox. Some Inuit residents think sea-ice thickening could improve hunting. Others aren't so sure.
On weekday afternoons community members gather at the heritage center in the high school library to sew fur boots and mittens and speak the local language. I came by to drink tea and ask about sea-ice thickening.
Luhn (tape): What's the word for sea ice in Inuktitut?
Eva Komak: Just hiku, hiku.
Community members: Hiku.
Luhn: The sea ice has been forming later in the fall, which means locals have to wait longer to start hunting their food. A few have even fallen through the ice on their snowmobiles. Hundreds of caribou have fallen through, too. Ice loss has slashed the local herd by 90 percent. That's a big deal for Cambridge Bay.
David Hanak: The sea ice, it's really important because we have to get to our destination to get our food sources out, out on the land.
Luhn: That's David Hanak, a hunter who has occasionally worked as a guide for Real Ice. We were eating pieces of candied arctic char, which was the color of salmon and tasted sweet and smoky at the same time.
He hopes that sea-ice thickening could someday help rejuvenate hunting and fishing around Cambridge Bay.
Hanak: But I would say, yeah, it's a pretty—a good idea to take out the water from the ocean and put it right on top the ice to make it thicker and thicker.
Luhn: But some of the elders here have their doubts. Annie Atighioyak was born in 1940 in an igloo on the sea ice. Speaking through an interpreter she raised questions about the potential consequences.
[CLIP: Annie Atighioyak speaks in Inuinnaqtun.]
Komak (translating for Atighioyak): They have mixed feelings, too. We all do.
Luhn: Real Ice isn't sure where it will try to do its 100-square-kilometer demonstration. But if it's in the strait near Cambridge Bay, Annie says she'd be concerned about the underwater drones disturbing wildlife.
[CLIP: Atighioyak speaks in Inuinnaqtun.]
Interpreter (translating for Atighioyak): Doing that under the water, we're gonna get no more fish, no more seal, no more.
Luhn: Inuit activists have accused other geoengineering projects of colonial thinking. Iñupiaq people in Alaska said a field trial that scattered tiny silica beads on a lake there failed to obtain their free, prior and informed consent. Sarah Olsvig, the international chair of the Inuit Circumpolar Council, has spoken out against a proposed seabed curtain test in her native Greenland.
Sarah Olsvig: I would say, when somebody approaches the Arctic and our homelands as Indigenous peoples and say, 'We need your piece of land in the name of a greater good,' that's exactly what happened when we were colonized.
Luhn: She says geoengineering, which exists in a legal gray area, needs to be better regulated.
Real Ice obtained permits from the regional Inuit government and the Cambridge Bay hunters and trappers organization. The company says it would do an environmental and social impact assessment to make sure the larger demonstration it plans wouldn't cause other significant harm.
Let's say Real Ice continues to scale up and achieve its dream of thickening one million square kilometers of sea ice. If that ice could be preserved for one additional summer month, the company says it would cool the planet as much as removing 930 million metric tons of carbon dioxide from the atmosphere for 20 years.
It sounds like a lot, but humanity emits about that much CO 2 every eight days. In other words, sea-ice thickening won't be worth much if we don't start reducing emissions. Andrea, the Real Ice Co-CEO, calls it a Band-Aid that would give humans time to actually heal the planet.
The next question is: Who's gonna pay for it? Real Ice's directors have committed $5 million to research, plus part of the $13 million from the U.K. government. But thickening one million square kilometers of ice would cost an estimated $10 billion annually.
Real Ice hopes to eventually get more funding from governments, like the Amazon Fund to save the rainforest has—although the Amazon fund has only raised about $780 million. So the company also wants to sell cooling credits, a kind of carbon offset. Companies that want to reach net-zero targets would pay Real Ice to do a certain amount of planetary cooling on their behalf.
Critics say all this money would be better spent on decarbonization efforts like investing in solar and wind energy. In a preprint journal article 42 top glaciologists argued that sea-ice thickening and other polar geoengineering techniques are infeasible and dangerous. The scientists say these approaches could hurt ecosystems as well as our sense of urgency to tackle climate change.
Brendan, the marine biologist, is worried geoengineering could become an excuse to continue business as usual.
Kelly: Even if we got the technology and the science right, will we get the, the social contract, the social—the governance correct? That's really hard to imagine—you know, that we won't get hijacked.
Luhn: But he's even more worried about the geoengineering he says we're already doing by pumping billions of tons of CO 2 into the atmosphere.
Kelly: In, you know, an optimistic scenario a lot of things have to line up for thickening sea ice to be a net positive for the planet, right? All the issues of scale and, you know, feasibility and engineering and impacts on biota and timeliness. But we're somewhat desperate as a planet, I'd say.
Luhn: Even if we stop emitting CO 2 tomorrow, some research suggests it may be too late to save summertime sea ice. That's why Real Ice says that at the very least we need to see if sea-ice thickening works, if it might actually be able to refreeze the Arctic.
Feltman: That's all for today's Friday Fascination. We'll be back on Monday with our science news roundup. Don't forget to fill out our listener survey if you haven't already done so! You can find it at ScienceQuickly.com/survey.
Science Quickly is produced by me, Rachel Feltman, along with Fonda Mwangi, Kelso Harper, Naeem Amarsy and Jeff DelViscio. This episode was reported and co-hosted by Alec Luhn and edited by Alex Sugiura. Shayna Posses and Aaron Shattuck fact-check our show. Our theme music was composed by Dominic Smith. Subscribe to Scientific American for more up-to-date and in-depth science news.
For Scientific American, this is Rachel Feltman. Have a great weekend!