Part Ten

Phase Change

Prologue

They were pelican surfing when apprentices jumping up and down on the beach alerted them that something was wrong. They flew back in to the beach and stuck their landings on the wet sand, and got the news. An hour later they were up to the airport, and soon after that taking off in a little Skunkworks space plane called the Gollum. They headed south, and when they reached 50,000 feet they were somewhere over Panama, and the pilot tilted it up and kicked in the rockets, and they were pressed back in their big g chairs for a few minutes. The three passengers were in cockpit seats behind the pilot and copilot, and out their windows they could see the exterior skin of the plane, which looked like pewter, begin to glow, and then quickly turn a vivid glowing yellow with a touch of bronze to it, brighter and brighter until it looked as if they were Shadrach, Meshach and Abednego, sitting together in the fiery furnace and coming to no harm.

When the skin lost some of its glow, and the pilot leveled them off, they were about eighty miles above the Earth, and looking down on the Amazon, and the beautiful spinal curve of the Andes. As they flew south one of the passengers, a geologist, told the other two more about the situation.

“The West Antarctic ice sheet was resting on bedrock that is below sea level. It’s continental land, though, not ocean bottom, and under West Antarctica it’s a kind of basin and range zone, very geothermally active.”

“West Antarctica?” Fort asked, squinting.

“That’s the smaller half, with the peninsula sticking up toward South America, and the Ross ice shelf. The west ice sheet is between the mountains of the peninsula and the Transantarctic Mountains, in the middle of the continent. Here, look, I brought a globe.” He pulled from his pocket an inflatable globe, a child’s toy, and blew it up and passed it around the cockpit.

“So, the western ice sheet, there, was resting on bedrock below sea level. But the land down there is warm, and there are some under-ice volcanoes down there, and so the ice on the bottom gets melted a bit. This water mixes with sediments from the volcanoes, and forms a substance called till. It has a consistency kind of like toothpaste. Where the ice is riding over this till it moves faster than usual, so within the west ice sheet there were ice streams, like fast glaciers with their banks made of slower ice. Ice Stream B ran two meters a day, for instance, while the ice around it moved two meters a year. And B was fifty kilometers across, and a kilometer deep. So that was one hell of a river, running off with about half a dozen other ice streams into the Ross ice shelf.” He indicated these invisible streams with a fingertip.

“Now, where the ice streams and the ice sheet in general came off the bedrock, and started floating in the Ross Sea— that was called the grounding line.”

“Ah,” said one of Fort’s friends. “Global warming?”

The geologist shook his head. “Our global warming has had very little effect on all this. It’s raised temperatures and sea levels a little bit, but if that was all that was happening it wouldn’t make much difference here. The problem is we’re still in the interglacial warming that began at the end of the last Ice Age, and that warming sends what we call a thermal pulse down through the polar ice sheets. That pulse has been moving down for eight thousand years. And the grounding line of the west ice sheet has been moving inland for eight thousand years. And now one of the under-ice volcanoes down there is erupting. A major eruption. About three months old now. The grounding line had already started to retreat at an accelerated rate some years ago, and it was very close to the volcano that’s erupted. It looks like the eruption has brought the grounding line right to the volcano, and now ocean water is running between the ice sheet and the bedrock, right into an active eruption. And so the ice sheet is breaking up. Lifting up, sliding out into the Ross Sea, and being carried away by currents.”

His listeners stared at the little inflatable globe. By this time they were over Patagonia. The geologist answered their questions, pointing out features on the globe as he did. This kind of thing had happened before, he told them, and more than once. West Antarctica had been ocean, dry land, or ice sheet, many times in the millions of years since tectonic movement had deposited that continent in that position. And there appeared to be several unstable points in the long-term temperature changes—”instability triggers,” he called them, causing massive changes in a matter of years. “This climatological stuff is practically instantaneous as far as geologists are concerned. Like, there’s good evidence in the Greenland ice sheet that one time we went from glacial to interglacial in three years.” The geologist shook his head.

“And these ice sheet breakups?” Fort asked.

“Well, we think they might go typically in a couple hundred years, which is still very fast, mind you. A trigger event. But this time the volcano eruption makes it much worse. Hey look, there’s the Banana Belt.”

He pointed down, and across Drake Strait they saw a narrow icy mountainous peninsula, pointing in the same direction as the coccyx of Tierra del Fuego.

The pilot banked to the right, then more gently to the left, beginning a wide lazy turn. Below them as they stared down was the familiar image of Antarctica as seen in satellite photos, but everything was now brilliantly colored and articulated: the cobalt blue of the ocean, the daisy chain of cyclonic cloud systems spinning away to the north, the textured sheen of the sun on the water, the great gleaming mass of the ice, and the flotillas of tiny icebergs, so white in the blue.

But the familiar Q shape of the continent was now strangely mottled in the area behind the comma of the Antarctic peninsula, with gaping blue-black cracks in the white. And the Ross Sea was even more fractured, by long ocean-blue fjords, and a radial pattern of turquoise-blue cracks; and offshore from the Ross Sea, floating up toward the South Pacific, were some tabular icebergs that were like pieces of the continent itself, sailing away. The biggest one looked to be about the same size as New Zealand’s South Island, or even bigger.

After they had pointed out the biggest tabular bergs to each other, and the various features of the broken and reduced western ice sheet (the geologist indicated where he thought the volcano under the ice was, but it looked no different from the rest of the sheet), they simply sat in their seats and watched.

“That’s the Ronne ice shelf, there,” the geologist said after a while, “and the Weddell Sea. Yeah, there’s some slippage down into it too. . . . Up there’s where McMurdo used to be, on the far side of the Ross ice shelf. Ice was pushed across the bay and ran up over the settlement.”

The pilot started a second lap around the continent.

Fort said, “Now say again what effect this will have?”

“Well, theoretical models have world sea levels rising about six meters.”

“Six meters!”

“Well, it will take a few years for the full rise, but it’s definitely started. This catastrophic break will raise sea levels about two or three meters, in a matter of weeks. What’s left of the sheet will be afloat in a matter of months, or a few years at most, and that will add another three meters.”

“How could it raise the whole ocean that much?”

“It’s a lot of ice.”

“It can’t be that much ice!”

“Yes it can. That’s most of the fresh water in the world, right down there under us. Just be thankful the East Antarctic ice sheet is nice and stable. If it were to slide off, sea levels would rise sixty meters.”

“Six meters is plenty,” Fort said.

They finished another lap. The pilot said, “We should be getting back.”

“That’s it for every beach in the world,” Fort said, pulling his face back from the window. Then: “I guess we’d better go get our stuff.”