Stephen Baxter - Flood

Lily shut up, as she had developed a habit of doing when people pronounced how they would react in situations they could know nothing of.

Thandie said, “I have to do things. I’m an agent, you know? The frustration would drive me crazy.”

“Everybody feels like that. We all missed our lives, our families, our careers-”

“Yeah, but I got it in spades,” Thandie said ruefully. “Lucky for me I had the smarts to pursue an academic career, where you can be your own boss, though you’re continually fighting for sponsors and contracts and equipment funding. But even so I always seem to spot that limb and head right out on it.”

“Like your theories about the source of the flood water.”

“Yeah.” Thandie grinned, but her eyes were unfocused as she thought about it.

Lily knew that Thandie was getting her share of fame, or notoriety, through her outlandish hypotheses about the true source of the flooding and its likely rise-and everyone knew she hoped to get a book deal out of it. That was her true dream, it seemed, to transcend her profession, even the science, and become famous: to be the Thandie Jones, a media figure, a modern Jacques Cousteau. But to do that, of course, she needed to validate her theories with some hard data. Which was why she was down here now, spending Nathan Lammockson’s money.

However it seemed to Lily that Thandie hadn’t thought it through much further than that. After all, if she was right, if the sea-level rise really was going to become much worse than the consensus of experts was predicting, what would it mean for the world? Thandie was clearly ferociously intelligent. But it was possible she lacked some deeper qualities of imagination. Empathy, perhaps.

Maybe Thandie detected Lily’s reservations about her. They ran out of conversation, and much of the descent passed in silence.

So they dropped into the sea, the dive’s events unfolding relentlessly, the light outside deepening through shades of blue to black. As the air grew steadily colder condensation formed on the walls, making Thandie fret over the effect on her computer screens. It turned out a dehumidifier was faulty. After a time Lily pulled on her Russian fur hat.

At a kilometer down there was an ominous creaking. Lily imagined the small, cramped gondola being crushed like a meringue in a clenched fist. Thandie told her not to worry; it was just the external instrument mounts settling into place as they contracted with the cold.

More than two kilometers down, Thandie’s sonar revealed the shape of the submerged mountains of the Mid-Atlantic Ridge.

She had Lily direct the bathyscaphe toward the mountain slope. Powerful quartz arc-light lamps fixed to the gondola’s exterior picked out the slope, and they studied the TV image and peered through the small, murky Plexiglas window. Lily saw a featureless surface covered in some kind of ooze, a mess of mud, sand and rock. She could see only a few meters in either direction; there was no sense of the scale of the undersea mountain they cautiously skirted. Thandie powered up her radar system, and tested it out on the mountain slope. It returned bright, clear echoes, embedded in which, Lily understood, there was a wealth of data on the deeper structure of the rocks.

When they got close enough a kind of handler arm implanted small charges in the mud. After the Trieste was safely away, these would be detonated to generate seismic signals, another way to probe the rock’s deep interior. Fish and crabs and worms swam by, disturbed by the arm. They were ordinary-looking creatures, but pale, adapted for the dark and the thousand-atmosphere pressures of this deep. Thandie quoted names like echiuroid worm and ethusa and bassogigas. It was an unprepossessing sight, a deep-sea fauna unremarkable to nonspecialist eyes.

Thandie had Lily sail the Trieste away from the slope so she could direct the radar to peer down the mid-Atlantic rise to the deeper floor. As soon as she did so the radar stopped returning clean echoes. The data display was flickering, jumbled.

“Shit.” Thandie ran through a quick diagnostic. “Everything seems OK.” She bounced a quick test pulse off the mountain; the echo came back clean. “But when I send the pulse downwards…” She shook her head. “If I take the results seriously, the sea floor down there is shattered. Broken up. Some kind of subsidence maybe.” The bathyscaphe shuddered. Thandie grabbed the arms of her chair. “Now what?”

Lily hurriedly checked through her own data displays, running through possible scenarios: an implosion of a flotation tank, a propeller failing. All her indicators were fine. “But we’re rising,” she said.

“What?” Thandie leaned over to see. “We’re heavier than the water, we can’t be.”

Lily said nothing; she just pointed to the depth gauge, which had gone into reverse. And she had started to feel queasy. She quickly checked the craft’s stability. Trieste was spinning. “Spinning, and rising,” she said. “It’s like we’re caught in some kind of updraft.” She glanced out of the thick window. By the boat’s lights she saw turbulence, muddy swirls.

“I knew it,” Thandie breathed.

“What?”

“It’s a fountain. Straight from the mantle reservoirs, coming up through some kind of shattered terrain.”

Lily said, “Tell me what we’re seeing.”

“Water, Lily. Water bubbling up from the interior of the Earth. I think this is the source of the flooding, the sea-level rise. My God, Lily. I’ve been down here a dozen times. We’ve found some direct evidence before, seeps, changes in salinity, but nothing as dramatic as this. You found it on your very first dive!”

“But what is it?”

“A subterranean sea…”

Lily sailed them clear of the updraft, into calmer water.

Thandie said she had come up with the idea of deep subsurface oceans through luck. She was in the right place at the right time.

“It started with a study I came across from back in the noughties, where a couple of guys from UC San Diego went through a heap of old seismic signals. You understand that earthquakes generate waves that travel right through the structure of the Earth; you can track them and see how they are diffracted by the different density layers down there, and so on. What they found was a consistent weakening of the waves around a thousand kilometers deep, that’s in the Earth’s mantle, somewhere under Beijing. They showed that the muffling had to be caused by water, immense quantities of it, as much as the Arctic ocean maybe, trapped in porous mantle rock. And there are other theories about how there could be more water down there in other forms, whole oceans trapped a molecule at a time in the structure of certain minerals in the mantle rocks.”

“Subterranean seas.”

“Exactly.”

“So how does the water get there?”

“Well, maybe it’s a relic of Earth’s formation. The planet was born from a cloud of rock and ice, mostly water ice. It’s generally thought that most of the water and other volatiles were boiled off in the heat of formation, and the oceans we ended up with were delivered later by impacting comets. But planetary formation is a complex business. There’s no reason water couldn’t be trapped in the infall, as Earth coalesced.

“Or the water could be transported down there from the surface by tectonic processes. We know that happens in the present day. Here we are at a place where ocean-floor plates are created. There are corresponding places where they are destroyed-subduction zones, where the plates are dragged under one another, back down into the mantle. And when that happens, a lot of water and other material is hauled down with them.”

“So you knew about these deep reservoirs already. And when you needed a theoretical source for a sea-level rise-”