So, Greenland was a much smaller ice cake than East Antarctica, but it was not insignificant. If it melted off (and it was a remnant of the previous ice age’s giant ice cap, located very far south for current conditions), it would mean another seven meters’ rise. That would ruin the adjusted new coastline civilization, so painfully fought for.

As with all ice sheets, it did not just melt; it slid in glaciers down into the sea, speeded by the lubrication of meltwater running under the ice, lifting the glaciers off their rock beds. It was the same in Antarctica, but while Antarctica’s ice slid down into the sea all the way round its circumference, so that there was nothing they could do about stopping it, Greenland was different. Its ice was mostly trapped within a high tub of encircling mountain ranges, and it could only slide down into the Atlantic through a few narrow gaps in the rock, like breaks in the edge of a bathtub. Through these gaps the lubricated glaciers poured at a speed of many meters a day, down U-valleys already smoothed for millennia, and when they hit the rising ocean, their snouts floated out over the terminal lips that often lay at the mouth of fjords, thus launching icebergs to sea more smoothly and swiftly than ever.

Early in the history of glaciology, researchers had noticed that one fast glacier in West Antarctica had suddenly slowed to a crawl. Investigations had found that the lubricating water underneath the ice had broken into some new channel and gone away, so that the immense weight of the glacier had thumped back onto the rock, causing it to stall. That now gave people ideas, and they were attempting to do something similar in Greenland by artificial means. They were testing several methods at one of the narrowest and fastest of the Greenland glaciers, the Helheim.

The western coast of Greenland was rather reassuringly icy, Swan thought, given all that one heard about the big melt. Under their helicopter lay a skim of winter sea ice, breaking up into giant polygonal sheets of white on a black sea. There was a polar bear park on the north shores of Greenland and Ellesmere Island, she was told, where tabular bergs floated on the natural eddy or got herded there by long flexible booms pushed by solar-powered propellers. So the Arctic ice was not entirely gone, and it was really quite beautiful to see it below her, and also to see how black the ocean was, as unlike the blues of tropic seas as could be imagined. Black ocean, white ice. All the blues were in the sky and in melt ponds strewn everywhere on the exposed ice of the Greenland ice cap, held three kilometers above the ocean by jagged black ridgelines—the coastal range, the chewed edge of the bathtub, holding in place the inland plateau of ice. The whole situation was as clear as could be, viewed from a helicopter flying five kilometers up.

“Is that our glacier?” Swan asked.

“Yes.”

The pilot headed down toward a little red X marking a flat spot of rock on a ridge overlooking the glacier, several kilometers upstream from where it calved into the ocean. The flat spot as they descended turned out to be about twenty hectares, with room for the whole camp; the red X was giant. As they made their last descent the whole scene lay below them, a fantastic prospect of black spiny spires, white ice, blue sky, black sunbeaten water in the fjord.

Outside the helo it was stunningly cold. It made Swan gasp, and a bolt of fear shocked her: if one felt this kind of cold in space, it would mean a breakdown and imminent death. But here people were greeting her and laughing at her expression.

Around their plateau, black lichenous spikes shattered in their thrust at the sky. Below them in the great U-valley the rock of the side walls had been ice-carved to curves like muscled flesh, scored by horizontal lines where boulders had been scraped across the granite hard enough to dig right into it—when one thought about it, quite an astonishing pressure.

The glacier itself was mostly a broken white surface, nobbled blue in certain patches. Though crevasse fields disrupted it frequently, the ice plain was fairly level across to the black ridge on its far side. Swan took off her sunglasses to look, then blinked and sniffed as a stunning white flash hit her like a blow to the head. She had to laugh—snorted—through her squint spotted Zasha approaching, and reached out an arm for a hug. “I’m glad I came! I feel better already!”

“I knew you would like it.”

The camp’s plateau made a perfect location for what was really a little hodgepodge of a town. After showing her the galley and getting her stuff stowed in the dorm, Zasha took her out to the edge that overlooked the glacier. Directly below the camp the ice was shattered all the way across to the other wall of the glacier. This apparently was the result of injecting liquid nitrogen between the ice and the bedrock. A certain amount of ice had been tacked down, but the ice over that had sheared off and continued on its way, shattered and slower, but still moving.

Downstream from that jumble there curved a deep gap in the ice. “That’s their latest experiment,” Zasha said, pointing. “They’re going to melt a gap all the way across, and keep melting the ice as it comes down. The ice downstream will slide away, and having cleared a space, they’re going to build a dam in the empty air, and when it’s done let the upstream ice come down to it.”

“Won’t the ice just flow over the dam?” Swan asked.

“It would, but they plan to build it so high that it will match the height of the interior ice cap. So ice will flow here until it rises up as high as the rest of Greenland, and then there won’t be any downward flow.”

“Wow,” Swan said, startled. “So, like a new ridge of the mountain range, filling this gap? Created while the ice is flowing down at it?”

“That’s right.”

“But won’t the ice up on the plateau just flow down other glaciers?”

“Sure, but if it works here, they plan to do it all the way around Greenland, except at the very north end of the island, where they’re trying to keep the sea ice park supplied anyway. They’ll corral what slides in up there, and slow the outfall, and that will keep the Greenland cap substantially in place, or at least really slow the melting down. Because it’s the sliding into the sea that makes it all happen so fast. So—we’ll stop up every break on the island! Can you believe it?”

“No.” Swan laughed. “Talk about terraforming! This must be a U.S. Army Corps of Engineers idea.”

“It sounds like it, but these are Scandinavians here. Plus the local Inuit. Apparently they like the idea. They regard it as a temporary measure, they said.” Zasha laughed. “The Inuit are great. Very cheerful tough people. You would like them.” A quick glance. “You could learn from them.”

“Shut up with that. I want to go down there and see what the bedrock looks like.”

“I figured you would.”

They went back to the galley, and over big mugs of hot chocolate some of the engineers in the camp sat with them and described their work to Swan. The dam was going to be made of a carbon nanofilament weave, somewhat similar to space elevator material, and it was even now being spun over foundation pilings drilled deep into the bedrock. The dam would rise from the ground, spun in place by spiderbots rolling back and forth and passing each other like shuttles on a loom. The dam, when completed, would be thirty kilometers wide, two kilometers tall, and yet only a meter thick at its thickest point. The structuring of the dam’s material was another biomimetic, the carbon fibers shaped like spiderweb strands but woven like seashells.

Downstream from the dam a short new glacial valley would be exposed. This would revegetate just as the other little green parts of Greenland had at the end of the ice age, ten thousand years before. Swan knew just how the U-valley would turn from bare gray rock into a fellfield biome, having induced it to happen in many an alpine or polar terrarium. Without assistance it would take about a thousand years, but with some gardening the process could be shortened a hundredfold: just add bacteria, then moss and lichen, grasses and sedges, and after that the fellfield flowers and ground-hugging shrubs. She had done it; she had loved it. From now on things here would every summer be exfoliating, flowering, casting seed; every winter it all would tuck into its subnivean world happily, and then struggle through the thaw and melt of a new spring, the really dangerous time. The ones that didn’t make it through the tough spring would provide food and soil for the ones that came after them, and on it would go. The Inuit could garden that if they wanted to, or let it go its own way. Maybe try different things in different fjords. How Swan would love to do that. “All right, maybe I need to become an Inuit,” she muttered at Z, staring at the map spread before them. She saw that Greenland itself was a whole world, and her kind of world—empty—therefore no one mad at her.