A couple of hours later, with a new watch strap on my wrist, I was in the Siple Dome comms tent, putting a radio call through to Dave Bresnahan back in Mactown. He couldn’t hear me, so everything had to be relayed through MacOps.
‘I have a ride to Upstream D,’ I said. ‘Henry has offered to take me. Do I have your permission to go?’
I waited for the message to be passed on. The crackly reply came:
‘Will Henry pick you up on the same day or would you have to stay?’
‘I’d like to stay.’
Another pause.
‘He says you could be stuck there. He can’t guarantee to fly you back out for maybe five days or more.’
‘Fine by me.’
This time the pause between messages was longer. I waited anxiously. And then through the static came the voice of MacOps. ‘He says tell her to enjoy her trip.’
The next morning Henry and I took off early. At first the ground was flat, white and featureless. But, suddenly, I saw crevasses on the surface of the ice, like score marks made by gigantic fingernails. Here and there, the snow bridge had broken open, and that familiar vivid blue ice shone through from beneath. Then the crevasses became less regular, criss-crossing, curving, a tangled mess of scattered dips and hollows. ‘We’re right over the margin now,’ Henry said from the cockpit.
That meant we were crossing over into the ice stream. On one side, the ice was moving perhaps several feet per year. On the other, it moved that same distance in a day. On the outside of the margin the ice was resting, on the inside it was racing, and the area between was being ripped apart with the strain, creating such extraordinary patterns of crevasses on the ice that the Twin Otter pilots had given the different margins fanciful sobriquets: ‘The Snake’, ‘The Dragon’, ‘Valhalla’.
Until now the biggest glacier I’d witnessed was the Beardmore, the staircase that Shackleton and later Scott had used to climb up on to the polar plateau. I’d seen it on the flight to the South Pole and it was streaked with flow lines, an impressive frozen river. This one was much, much bigger, too big to take in from the air. It was thirty miles wide, a half mile thick and ran inland for hundreds of miles. The great size and fantastic speed of these ice streams meant they were all colossal superhighways, transporting ice at an extraordinary rate from the interior to the sea. And because of this, many researchers were convinced that they were the key to the stability—or otherwise—of the West Antarctic Ice Sheet.
Moreover, these ice streams weren’t just big and fast; they were also dynamic, stopping and starting, writhing from one place to another on timescales short enough to matter to humans.4 The neighbouring ice stream to this one5 was scarcely moving at all. And yet radar measurements of buried crevasses at its margin showed that it must have been moving as quickly as all the rest, as recently as 130 years ago.
There was something else odd about these ice streams. When we passed the jumbled, chaotic crevasses of the margin, the ice was completely smooth again. It was moving faster than any other glacier I had yet seen. That ought to mean that the ice was jumbled into crevasses as the racing glacier snagged on the ground beneath. But there were no flow lines, no signs of movement, nothing. Researchers had discovered that the ice streams had no flow lines because they slid incredibly smoothly on the base, so that there was nothing to rip, strain or distort the ice.
There were many theories for why the motion should be both so fast and so smooth, but now Barclay Kamb from Caltech was leading the effort to see for himself. One by one he was visiting as many as possible of the Siple Coast’s six ice streams, drilling holes through them to find out what was happening at the business end, the meeting point where the ice slipped over the ground beneath.
Though I hadn’t yet met Barclay, I’d read many of his papers. He habitually described himself as a ‘doubting Thomas’, who needed to see and touch before he could believe. He called it ‘the truth of the drill’. ‘You can have remote-sensing data and interpretations and theories of what is down there, deep below the surface, but until you drill down and get hold of the actual materials, you never really know.’
We landed on a bright blue Antarctic morning. Steve Zebroski, the camp manager, had come to meet the plane and say a hasty hello. He was pale and red-eyed through lack of sleep; the team had been working round the clock to rescue their season. We went together into the galley tent, which held a fully working kitchen filled with the enticing smell of freshly baked bread. Lesley, the camp cook, had just pulled a tray of rolls out of the oven. She offered me one, with a cup of tea, but Steve warned me that the team at the drill site was within about fifteen minutes of breaking through to the base of the ice on its latest hole. I declined the tea, stuffed a roll into my parka pocket and followed him back out.
‘You can take this skidoo,’ he said, pointing to one that had a name—Clarence—stencilled in duct tape on the side. It turned out that Barclay’s team always chose a theme for naming their skidoos, and this year it was characters in the movie It’s a Wonderful Life. Clarence was the angel who came to show James Stewart’s failing businessman that his life wasn’t so bad. I’d always found the movie too soppy for my taste, but I was still quite pleased to get the angel.
‘How do I find the drill site?’
Steve gave me a dry look. ‘There aren’t many tracks around here,’ he said. ‘Just don’t go near any black flags.’
Ah yes. After the trouble with the Hercules, a team of mountaineers had scoured the area for any further crevasses, and had marked the few danger spots with flags. And in any case Steve was right. There was only one ‘road’, where the snow had been churned up into a visible track. I turned on the engine, pulled down my goggles and headed off.
Barclay came to meet my skidoo. He was tall and clean-shaven—which was rare for men out in the field. I later discovered that among its other amenities this camp even had a shower. True, you had to shovel your own snow to make the water, but the result was as hot and comfortable as any hotel. (As instructed, I shovelled the snow after I’d finished, so the water could be ready melted for the next person to come along. It was hot work, so I didn’t register how cold the air was—until I heard a tinkling sound, which turned out to be strands of my wet hair that had quickly frozen solid.)
The set-up at the drill site involved the same sort of derrick and cable winch that I’d seen for ice coring. But unlike the ice-corers who needed to bring back samples of the stuff they were drilling through, all Barclay wanted to do was get through the ice sheet to what lay beneath. So there was no need for a complicated drill with a rotating metal head and sharp teeth. Instead, the Caltech method was much quicker and cleaner—amounting more or less to a vertically mounted fire hose. The idea was to melt a large amount of snow—which is why there were three people frantically shovelling from a bulldozed snow pile into a large vat—heat the water to about 200°F and pump it under very high pressure through the tip of a jet that looked like the head of a spear. Then you just pointed the jet downwards, pressed the right buttons, and let the combination of hot water and gravity do the rest.
Still, the ice was so thick that it took twenty-four hours to get through it. The team had started this particular hole yesterday and were just about to hit the bottom. Various graduate students and field assistants were kneeling on sheets of plywood around the hole. The derrick was holding the hose in place and one woman was feeding it down through her hands, letting it slide, feeling for the tug it would give when it hit the floor. ‘Come on . . .’ she said. ‘Break through.’
Barclay’s colleague from Caltech, Hermann Engelhardt, emerged suddenly from the Jamesway tent, as short as Barclay was tall, as hirsute as Barclay was clean-shaven. He had been monitoring the instruments and seen the shift in tension on the hose. ‘That’s it!’ he shouted. ‘Pull it out!’ Two people started heaving upwards on the hose, while another dangled his weight from the cable to lend additional pulling power. I ran over and joined in, heaving until someone said: ‘
OK, she’s safe.’ Now, apparently, there was no chance of the drill sticking, though I didn’t know how they knew. We let go and the winch took over, pulling the jet back up to the surface.
Barclay had ducked into the tent again with Hermann and I followed. Both were leaning over a laptop looking at a series of peaks in a graph. ‘That’s beautiful,’ Barclay said. Things were apparently going well.
He told me that this was the fourth hole they had drilled in very rapid succession and all were testing why the ice streams could move so quickly and so smoothly. The answer was a combination of two things that you wouldn’t normally expect to find under a kilometre of ice: water and mud.
Previous holes that they had drilled through other ice streams had shown that these giant carpets of ice seemed to be sliding on their own bed of water. Though this might seem surprising, it’s not that hard to make water at the bottom of the ice sheet. There is always a certain amount of warmth radiating outwards from the planet’s hot interior, and this geothermal heat would certainly help. Then you have the weight of the ice, and the friction caused by its scraping along the bed. Put those together and you have enough energy to melt the ice at the base of the glacier and give it a reason to slip.
But it’s hard to prove, really prove, that there’s water down there if you’re using a hot-water drill. How could you tell if you were just seeing your own water? So for the first hole that Barclay and his team had drilled here, they had deliberately used the lowest water pressure that they could get away with. If it was lifting up the entire weight of the ice sheet to let it slide, the water down below would have to be at a very high pressure. Go in there with a lower pressure, and the water from below should surge up the hole. And that’s exactly what happened. When they broke through on that first hole, they saw a spike in the pressure caused by the ice sheet’s own plumbing system. There was definitely water down there, and it was definitely at a high enough pressure to lift and lubricate the ice.
In subsequent holes they had been experimenting with how interconnected the plumbing was. This time, they had seen oscillations in the pressure as water swilled up and down first one of their boreholes then another, showing that the channels under the ice really were connected. That’s what had caused the peaks in the graph that Barclay was so pleased about.
There was also another factor that affected why the ice streams moved so quickly and so smoothly. Their beds were made not of rock, but of mud. It was the same sort of stuff that you find on the sea floor, and was probably left over from the last time that West Antarctica was an ice-free ocean. On hole number two, the team had managed to drill out a plug of sediment from the bottom of the hole, quickly, before the water inside it froze and the hole closed over. Barclay took a small tub off the shelf and opened it to show me. Inside was dark slate-grey mud, gritty and very sticky, and embedded with small pieces of gravel. He smeared a little on my fingertips and I rubbed them together. Now it was strong, but Barclay assured me that when it was saturated with water—a half mile below our feet—it was soft and fluid. With the help of the water, this mud was strong enough to carry an ice sheet on its back, but weak enough to deform and slip and let the ice slide.
The next day, I took my skidoo off to see the crevasse that had caused all the trouble with the Hercules. The rescuers from Mactown had half filled it with snow to retrieve their plane. You could walk down a snow slope into it, touch the sides and wonder. Inside it was cold, much colder than the surface, and my eyelashes quickly frosted over. Close to the entrance the walls were decorated with frost fronds the size of dinner plates, sticking out from the ice like corals. But as I climbed farther in the sides became sheer, and glowed faintly with a cold, hard blue. They grew closer together until I could barely fit in the gap between. I tried to imagine what it would be like to fall and be wedged in, and shivered. Nobody knew why there was a crevasse here in the inner part of the ice stream, far away from the margins where the ice was supposed to run smooth. But perhaps there was some kind of bobble in the bed beneath, just enough to make the ice rear up a little and split. It wasn’t a trap so much as a reminder that Antarctica was not built with humans in mind. We could occupy it, and study it, but it was still barely tolerating us.
That evening the light was lovely. I borrowed some skis and went out a few kilometres beyond the camp. Apparently there hadn’t been much wind lately; the sastrugi were smooth and low. This was a new variant of the familiar ‘flat white’ of the East Antarctic plateau. Though the air here was 5°F and dry enough to scrape the skin, it was still noticeably damper than the dry desert of the east. There was moisture enough in the air to coat guy ropes with hoar frost. And the crystals on the surface were big and bold and flashy. They glinted in the slanting sunshine, as if someone had scattered handfuls of diamonds over the snow.
There was something liberating about being able to go where I pleased, with no tracks or roads to direct me. Earlier in the day, when one of the team had offered to let me drive one of the snow cats back to the camp, I had asked him nervously ‘what if I crash into something?’ He had turned slowly on his heels in a full circle, peering in exaggerated fashion at the flat white landscape. ‘Into what?’ he had said.
I had been assured that there were no hazards as long as I stayed away from the only crevasse in the neighbourhood, took a radio and kept within sight of the camp. But still I felt oddly nervous. Suddenly I felt myself falling with a mighty ‘whump!’. Almost before I could register the sensation, I hit solid ground again and gasped with relief. It was a ‘firn quake’, in which an area of ice weakened by the attentions of the sun suddenly drops a few centimetres. Steve had warned me about them a few days ago, though I’d forgotten. ‘It’s shocking at first,’ he had said. ‘You fall three inches to your death.’
Apart from freezing to death, crevasses are the most prevalent—and romantic—danger in Antarctica. The great Antarctic heroes marched resolutely over the ice, knowing the risks, that at any moment they could plunge through a thin bridge of snow and find themselves dangling helplessly in their harnesses over a gigantic blue crack that descended all the way to oblivion. And yet although my heart was now racing from the firn quake, I still couldn’t understand how it would feel to be faced with an apparently innocent landscape that was riddled with dangers. I still didn’t really know crevasses at all.
Next morning, the team decided to pack up. They had done as much as they could and there was a plane coming soon to take out the first load of equipment. In eight days they had drilled six holes. They were exuberant, deservedly so. Now the people shovelling snow into the melter were preparing a hot tub, while the rest took a banana sledge and tobogganed down the snow pile, which they had unofficially christened ‘The Mountain’. Wheeeee! ‘Look at that,’ Barclay said. ‘It’s the only mountain on the West Antarctic Ice Sheet.’
Barclay’s work at Upstream D confirmed what he had seen before and what he, and others, would see again. Some combination of water and mud lay beneath all of the ice streams, both here on the Siple Coast feeding the Ross Ice Shelf and the ones on the other side of the continent, which were feeding the Ronne Ice Shelf.
Though it makes the ice streams both quick and dynamic, this could still be good news. Some of the mechanisms that researchers have since found to explain the dynamism of the ice streams also suggest that they may be making the ice sheet more stable, not less.6
If they sped up, for instance, the ice would get thinner, which would mean less weight pressing down, which meant less friction, so less water, so they would slow down again. If they ate back into a region where there was no sediment, they would probably stop. And radar evidence from planes crisscrossing the Siple Coast suggests that it is not losing ice; in fact it may be thickening slightly.7 On the other side of the continent, the streams feeding the Ronne Ice Shelf look, if anything, even safer. They are thicker, but they run in grooves, so it is hard for them to widen or writhe, and one of the largest—the Rutford Ice Stream—is pegged on a high ri
se that keeps it in check.8
So several decades of work on the ice streams feeding the Ross Ice Shelf on one side of the continent, and those feeding the Ronne Ice Shelf on the other, have produced this reassuring message: for the foreseeable future, it looks as though these two-thirds of the West Antarctic Ice Sheet are fairly stable. Even as temperatures warm over the next few centuries, the shifting, snaking ice streams are very unlikely to speed up enough to send the ice sheet sliding into the sea.
But, of course, there’s a twist. Because while all these scientists were spending all this time and trouble tramping around the front and back doors of the West Antarctic Ice Sheet, nobody was checking the side door. The Amundsen Sea Embayment is the third section of the West Antarctic Ice Sheet, the one that spills out into the South Pacific, the one that’s hardest to get to, that’s farthest from anyone’s field of operation and has the foulest weather. The one that nobody was watching. And it turns out that this missing piece, this final third of the West Antarctic jigsaw puzzle, is the one where all the action is.
It wasn’t entirely unexpected. Certain glaciologists have been worried about the Amundsen Sea Embayment for decades. First, there was the lack of ice shelves. Unlike the other two exit points for West Antarctic ice, which flow into the Ross and Ronne ice shelves, the glaciers pouring into the Amundsen Sea have no massive shelf of floating ice to buttress them. Instead, each has its own miniature ice shelf that runs for just twenty miles before it hits open water. That puts the glaciers perilously close to the ocean, with very little to hold them back.
On top of that, there were signs from expeditions made back in the 1950s that the ground deep beneath these Amundsen Sea glaciers seemed to have an unusual shape: from the coast going inland, it sloped downwards like the inside of a bowl.
This combination of warm seawater lapping up close to the glacier front, and underlying ground sloping downwards as it went inland, could be devastating. The point where the land ice goes offshore and starts to float acts like a hinge; the floating part moves up and down with the tides (and any other changes in sea level). If this hinge line started to retreat inwards, the seawater would follow it, flowing in and down the sides of the bowl beneath the land ice. This would reduce the resistance for the flowing land ice, so it would slide faster, so the hinge line would retreat further, moving inwards towards that central basin in what could be an unstoppable feedback. Back in the early 1980s, the Amundsen Sea Embayment was already being called the ‘weak underbelly of Antarctica’.
Antarctica Page 32