Antarctica (33 page)

‘How deep was this ice?' I asked. Inger did a quick calculation.

‘About 10,000 feet.'

‘So how old would that be?'

‘About 800,000 years.'

‘You're telling me that this fell as snow 800,000 years ago?'

‘Yes.' Then she added softly: ‘It's a privilege to stand and look at it.'

I caught her mood, or maybe she was catching mine. Because, as I looked at this piece of ice and tried to picture the world of its birth, I felt a shiver. That ancient Earth was utterly alien to me.

The ice was completely clear, with a luminous translucence. There were no signs of melting, which was good, but nor were there any bubbles. At the extreme depth that this ice was pulled from, the pressures were so high that the air dissolved into the ice and formed a kind of ice-air crystal mix called clathrates.

‘The air has dissolved,' I said to Dorthe. ‘Doesn't that affect the gas?'

‘No,' she said. She told me that it wasn't just the depth. Sometimes you got bubbles even at those depths, depending on how much snow was falling. And when you melted the ice and sucked out the air from the same depth, clathrates gave the same value as bubbles. She looked over my shoulder at the ice. ‘It's a miracle that the air stays in there. But it does.'

Dorthe picked up a piece of metal and shaved the top of the remaining ice to clean it. Then she took a two-pronged instrument like a bent tuning fork and scraped it along the ice while Inger watched numbers on a monitor. ‘Normally we'd do this much more carefully, millimetre by millimetre, but this is just to get a rough idea.' They were measuring the electrical resistance of the ice. The more dust there was in the ice, the harder it was for the electricity to flow, and more dust also tends to mean colder, drier conditions. In this case the resistance was quite high. ‘It's fairly dusty, so it was probably an ice age.'

Now Dorthe took a thin slice that she had carved out of the ice and showed me how they put it under polarisers to measure the crystal size. I'd seen this before. Normally, in younger cores, the ice jumped into a psychedelic jigsaw puzzle of colours marking out the different crystals. But here there were just two shades of pink, with a boundary running down the middle.

The crystals here must be enormous. Closer to the surface, they would each be just a few millimetres long or less. But as they descended they embarked on a tug of war for ice, in which the larger winners grew and the smaller losers vanished. After this much time, the winning crystals had grown into great glassy structures several inches long.

That was all the analysis the two scientists would do here. Their main task was to finish off bagging up the cores ready for their journey to Europe. I watched them doing this for a while, but I soon started to get cold. Although it was a few degrees warmer in there than outside, standing still, away from the Sun, brought the chills. ‘Come back any time,' Inger said as I left in search of hot chocolate. ‘We like the company.'

There is always something faintly sad about the end of a long project. This was the end of an era at Dome C. For nearly a decade, the camp had existed mainly to support the drilling of this momentous ice core, the one that would go back farther in time than has ever been done before, and that would surely tell us vital things about the way our planet has changed.

Now it would take on a new identity. The joint Italian-French construction crew had almost finished the new winter station. It stood about half a kilometre away from the summer camp, two elegant circular buildings, attached together by a corridor. Each building stood on six massive steel legs that could be jacked up, so that the station would be able to step gracefully above the accumulated snow. The legs could be lifted individually, and the connecting corridor could slide up and down where it met the two buildings to enable them to be raised one at a time. All the outer panels had now been assembled and the construction crew were busily fitting out the interior. When they had finished, there would be workspaces and leisure rooms, eighteen bedrooms with elegant oak furnishings, bathrooms and a fully fitted surgery. I was especially enchanted by the fire escape from the top floor, which consisted of a gigantic stocking. In case of emergency, the stocking would be unfurled and lowered from the window like Rapunzel's hair, and the occupants would slide down the inside using their elbows as brakes.

The construction crew was racing to be ready; in six weeks all had to be in place for the first ever wintering crew to move in. This was a big deal. There were only two other winter stations on the plateau: the South Pole and Russia's Vostok. Both had been built back in 1957–8, during the International Geophysical Year, which was a massive continent-wide scientific effort that more or less began the age of big science on Antarctica. The new station being built at Dome C would be only the third year-round base in the interior, and the first new one for fifty years.

The thirteen new winterers, a mix of French and Italians, would experience conditions among the most extreme on Earth. Nobody knew how cold it would get, but it was higher here than the South Pole so temperatures might fall as low as -110°F.
⁴
They would also be the first humans ever to see darkness here, and to witness the night sky.

That was one of the biggest reasons for staying beyond the summer. Though there would be a couple of glaciologists and meteorologists in the winter crew, the highest scientific hopes for Dome C lay in its astronomical promise. The lack of wind meant that the telescopes should be able to see stars more clearly than at the Pole. Already automatic devices were perpetually probing the sky for any disturbances that could cloud a telescope's view. (One particularly annoying device came housed in a bulbous green hut, which everyone called the ‘kiwi fruit' though it looked more like an unripe pumpkin. It spent its entire time sending out sound signals—sodar—to probe the air, in an eternal sequence of chirrups somewhere between a spooky sci-fi theme and an electronic bird. Luckily it was out of direct earshot of both the new station and the summer camp, but every time you passed you found yourself waiting for the change in sequence, then being irritated by it.
⁵
)

The University of Nice had also set up several telescopes, to be manned through the winter by astronomer Karim Agabi. In keeping with the elegant architecture here, the platforms holding the instruments were carefully designed with sweeping curves of wood. Karim told me that the architect had initially planned to create a single arch, like the ones girdling the bottom stage of the Eiffel Tower. However, he persuaded the firms providing materials to hand over two for the price of one, and now two golden arches stand side by side. It was unfortunate that this immediately called to mind the McDonald's logo, but the structure was undeniably beautiful.

Karim and other researchers from the University of Nice had been testing the site for the past five summers using telescopes painted in a colour that the catalogue describes as ‘Antarctic white', and even in daylight the conditions here were fantastic. If the winter results backed up what they had already seen in summertime, astronomy would soon take over from ice coring as Dome C's main raison d'être.
⁶

But in truth this was far from the end for the EPICA cores. Many of them were already being analysed back in Europe, and they were adding to an extraordinary body of knowledge that has come to us from deep in Antarctic ice.

We already know from records written into rocks, mud and trees that temperatures have varied a lot in the past. In fact, the recent relative stability that we've had on Earth over the past 10,000 years (which just happens to be when humans were developing their civilisations) is unusual compared to the lurches in climate that have taken place, perfectly naturally, over most of our world's history. Earth is a restless planet, and change is part of its nature. We humans have been lucky to be spared the effects of that restlessness, so far.

The ice itself also contains a record of past temperature if you know how to read it. Ice comes from snow, which comes in turn from water sucked up from the sea, carried through the air, frozen and then deposited back on the ground. So solid ice is just a rigid network of the molecules that make up water, each containing one oxygen atom and two hydrogen atoms. Researchers can read past temperatures in these molecules because both oxygen and hydrogen come in different flavours, called isotopes, some of which are heavier than others. The heaviest molecules are hardest to lift from the sea up into the sky, and so rarely have the chance to become rain (and then snow) unless temperatures are high and there is enough energy to do the lifting. When it's colder, primarily lighter molecules make it up to the lofty heights that can then freeze and fall again.

So if you measure the ratio of light and heavy molecules in the ice, you get a measure of how warm or cold it was at the time it was sucked out of the sea. Couple this with information about the air trapped inside that same snow and you can draw some important conclusions about why exactly our climate is so highly strung.

Another ice core, already drilled by the Russians just a few hundred kilometres from here at Vostok Station, covers about half the timescale of EPICA.
⁷
Over the 400,000 years that the Vostok core sampled, the temperature rose and fell four times, in great glaciological cycles. Our most recent ice age is the most famous, but in fact the Earth has experienced a whole series of them—perhaps as many as twenty-five—and Vostok captured the four latest times that our planet has frozen, thawed and frozen again.

And as the temperatures rose and fell, so too did the greenhouse gases. Higher temperatures meant higher CO
₂
and methane. Whenever temperatures were lower, CO
₂
and methane were lower.
⁸

In a way this shouldn't be a surprise. Both CO
₂
and methane are chemically built to trap heat. If you put more greenhouse gases like these into the air, basic science says that they will catch more of the warmth radiating out of the Earth and fling it back groundwards like expert fielders in a ballgame. That's how greenhouse gases work.

And, in fact, it's a good thing that they do. Our planet is a little too far from the Sun for us to be truly comfortable. By rights the whole place should be frozen in space, a giant planetary snowball. But the soupçon of greenhouse gases that we have long had in our air is enough to avert this catastrophe. It doesn't take much. CO
₂
is like chilli powder—if you want heat, a pinch is all you need.

Still, the results from the Vostok core were striking enough to cause a stir when they were published back in 1997, because the evidence was so clear and unequivocal. Looking into Antarctica's crystal ball of ice shows the effects of CO
₂
more clearly than any attempt at complex extrapolation.

True, the temperature tended to go first, and the CO
₂
to follow. But that doesn't mean that the CO
₂
was an effect rather than a cause. Scientists have long believed that what first triggers the planet to cycle in and out of ice ages are slight wobbles in the orbit of the Earth around the Sun, which affect how much sunlight arrives in the northern hemisphere in summertime on a timescale of 100,000 years or so.

However, this change in itself isn't large enough to explain the ice age—it's just the trigger. When the world starts cooling a little, other feedbacks quickly kick in. Colder oceans start to soak up more CO
₂
from the atmosphere, and freezing marshes and mires stop putting out so much methane. This cools the planet still more, which means more greenhouse gases disappear from the air, which means yet more cooling. The orbital wobbles start the process, but it's the greenhouse gases that provide the oomph. After that first trigger, the ice core showed how temperature and greenhouse gases marched in exact lockstep.

And there was something else. Though CO
₂
and methane rose and fell perfectly naturally in this way, the Vostok record showed that neither had ever, in 400,000 years, begun to imagine the levels that we have reached today. By pulling coal, oil and gas out of the ground and burning them to make our energy, we have filled our atmosphere with that chilli powder, which is now starting to burn.

If we knew this so clearly, why bother going back further in time with all the EPICA effort? The Vostok record was spectacular but it captured snow falling in only one place. And what if there was something special about those four ice ages that doesn't apply any more? In particular, Vostok stopped tantalisingly short of the ice age that took place between 425,000 and 395,000 years ago. That's important because various intricate wobbles in the Earth's orbit around the Sun have a big effect on our climate, and this was the last time that the orbit was exactly the same as it is today. It's a sort of mirror of today's conditions. Scientists have long worried that the four latest ice ages have all had relatively short warm gaps in between, of six thousand years or less. It's already more than 10,000 years since the last ice age, so does that mean another one is on the way? With EPICA, the scientists wanted not only to test the Vostok results at a different site, but to go farther back, to a time when the whole climate regime might have been more similar to today's.

The EPICA record turned out to hold at least four more ice ages, including that intriguing fifth oldest ice age that was the orbital mirror of the modern world.
⁹
One thing researchers have found is that the warm gap that followed it lasted 28,000 years, so we probably shouldn't be expecting another ice age any time soon—even without considering the extra amounts of CO
₂
chilli powder that we have already put into our air.
¹⁰

Moreover, just before the mirror ice age, something about the climate pattern changed; the temperatures weren't nearly so low during these ice ages, or so high in between. And the EPICA record also reveals something more surprising. Even when our climate was in some other phase, some different way of balancing the many subtle influences that make up the wind and weather and warmth we experience, temperature and greenhouse gases still marched in lockstep. Higher temperature always went with higher CO
₂
. Lower temperature went with lower CO
₂
.