The strange changes that scientists were picking up at Ilulissat were soon seen elsewhere. Back in 2006, a remarkable paper was published in the journal Science analyzing data from a satellite survey of Greenland.9 Its lead author was Eric Rignot, who had started off studying astronomy at the University of Paris but in the 1980s had moved to California to focus on ways to see from space what was happening on Earth. He is now at Caltech and, alarmingly, he found that the glaciers everywhere in the southern part of Greenland were collapsing and that the melt was spreading to the glaciers farther north.
Greenland holds a staggering amount of ice. Up on top of the ice cap, all you can see is an infinite field of white, but under your feet may be as much as two miles of ice, some tens of thousands of years old. You won’t be standing two miles up in the air, though, as the ice is so heavy that it has pushed the earth’s crust down below the level of the surrounding sea. If all 700,000 cubic miles of it were to melt away, the earth’s sea level would rise by around twenty-three feet, causing an unimaginable catastrophe.
A rise of twenty-three feet would engulf large parts of Florida and Bangladesh, drown the Nile Delta, and flood many of the world’s big cities. Still, everyone has always assumed that you couldn’t possibly melt away such a giant volume of ice in less than a millennium, time enough to build new cities and relocate the 15 percent of the world’s population that would find their homes underwater.
That view assumes that the ice just melts slowly away as global temperatures rise, as if it were an ice cube left out to thaw. No allowance was made for “dynamic effects,” that is, the rapid discharge of great chunks of ice straight into the sea. The 2007 IPCC report simply excluded fast-moving glaciers, recording that “models used to date do not include the full effects of changes in ice sheet flow because the basis in the literature is lacking.” Glaciologists love that quote as it shows that their discoveries are really new.
If you take into account the rapid collapse of the glaciers, how much water is Greenland adding to the world’s oceans? In 2008, Rignot teamed up with scientists from around the world and estimated that the ice sheet had been losing 30 gigatons of ice a year from the 1970s through the 1980s, 97 gigatons in 1996, and between 239 and 305 gigatons in 2007. I read their results in the journal Geophysics Research Letters and it left me stunned.10 A gigaton is a billion metric tons, or the weight of a cubic kilometer of water. Add the latest annual figure of 305 gigatons to the oceans and the sea level rises by close to a millimeter. Keep going faster for a century on top of the natural thermal expansion of the oceans as they warm and ice melting elsewhere and that is enough for governments around the world to have to add billions to the cost of coastal defenses. The acceleration is deeply worrying. Its cause appears to be those rapidly moving glaciers: the paper shows that they account for between 40 and 80 percent of the ice loss.
I called up Eric Rignot in his laboratory and asked if he was surprised too. He laughed. “Even just a couple of years ago, to state that the ice sheet was losing as much mass as it is, would make me considered a mad man. I think if you had told people in 1990 that I would make a prediction in 2008 that we are going to lose three hundred gigatons per year of ice in Greenland, everybody would have laughed. He is not serious, they would have said. There is no way you can get anything like that.” So what will happen next? “We see acceleration. It’s not a linear trend; it’s more rapid than that. I don’t know where it’s going to go. Ten years ago we thought we knew everything. Now we know we don’t. Predicting what might happen in the next fifty years with continued warming of the climate is a difficult game. I think the answers might change every year.”
I had already had some experience of rapidly changing answers. Not long before talking to Rignot, I had been up onto the Greenland ice cap to see the explanation for the sudden speed-up in the glaciers—or so I naively thought.
An easy way up is to follow the ten-mile-long route laid out by the French scientist Paul Emile Victor. Soon after the end of the Second World War, Victor realized that there were surplus military tracked vehicles to be bought cheaply. He used them to help build a winding route up through the hills not far from where the Eqi Glacier reaches the sea. Some obstacles were dynamited, and on a really tough stretch across a steep valley he built a half-mile-long cable system to shift heavy equipment. The remains of it are still there, along with abandoned sleds, bits and pieces of equipment, and some sun-bleached wooden crates that look as if they once held champagne. It is still the perfect spot for a picnic.
Victor’s route is much overgrown now. In early summer, the tundra is green with moss, lichens, and dwarf willow. Ptarmigan herd their huge families of newborn chicks away from you as you plod up the hill toward them. Sometimes you find one sitting on its nest, utterly still, relying on its dappled feathers to conceal it among the colors of the surrounding tundra. Sometimes it would have been better to flee. Just a few feathers and an abandoned egg lie at another nest. An Arctic fox had visited.
Higher up, the greens and browns give way to the dull, black-and-pewter-colored mounds of the lateral moraine pushed up by the moving ice. Then the ice cap lies in front of you, stretching 600 miles all the way to the east coast of Greenland. At first you can’t take your eyes from the infinite whites and blues of the undulating plain of ice and the streams of crystal meltwater that cross it. But I was up there to look for “moulins,” or rather, to listen for them.
Moulins are the places where melting water, running in rivers across the surface of the ice, suddenly vanishes down a hole, creating a churning waterfall under the ice which sounds like an old-fashioned mill race. You can hear a moulin a long way off and when you eventually come close you put on a climbing rope, attach the other end to a strong person at a good distance, and approach carefully. The rush of foaming water disappearing into a vent amid the brilliant blue of the ice is spectacular. So too is the slipperiness of the water-polished ice; one mistake and you’ll drown in the glacier’s plumbing.
I returned from the moulin hunt believing I had seen the cause of the ice cap’s slide toward the sea. With rising air temperatures, meltwater was draining way under the ice and lubricating the glacier’s slide toward the sea. That new theory had made headlines just a few years earlier.
Tavi Murray set me right. She is a glaciologist from the University of Swansea who I had run into by chance in a little airport in Greenland a year earlier. She was just off to survey thinning glaciers and told me about her plans with great enthusiasm. I called her to say I’d finally been up there myself and seen the moulins. Yes, she said, a few years ago, scientists had discovered that meltwater was getting down to the bedrock at the bottom of the ice and lubricating it, speeding the flow. “That was a big ‘wow,’” she said. This potentially catastrophic effect made its way into Al Gore’s documentary An Inconvenient Truth. Yes, it is still “very interesting,” said Murray, but it has turned out to be not quite the full explanation we need. When scientists were on hand to see a huge lake drain down a moulin in 2008, they found the glacier only managed to lurch forward three feet.11
So what is making the ice speed up? Rignot thinks the fast glaciers have been “ungrounded.” Warm water is getting underneath the ends of glaciers where they stick out into the sea and melting them so they are no longer jammed onto the bottom of the fjord. “It is as if someone was lifting up the part of the glacier which reaches the ocean and so the ice upstream is able to flow faster,” he explains.
For many of Greenland’s glaciers that’s not going to stop for a long time. The Jakobshavn Glacier follows a deep trench below sea level for sixty miles back inland, he says. Once the water starts to lift the glacier, the process just continues.12 “The take-home message is that if a glacier is grounded deep below the sea level, and reaches the ocean and it starts to retreat, there is very little you can do to stop it,” says Rignot.
That was scarcely reassuring, but both Rignot and Andy Shepherd, a glaciologist from the University of Edinbur
gh, assured me that if I wanted to really worry, I was visiting the wrong pole.13 The glaciers of the West Antarctic ice cap have also “unplugged.” We’ve got twenty years of observation in West Antarctica, explained Shepherd. “In the first ten years, we lost one hundred cubic kilometers [one hundred gigatons] of ice per year. In the second ten years, we lost two hundred cubic kilometers of ice per year. Keep doubling that to four hundred, eight hundred, and you get a very, very large sea level rise in a very short time. There is no theory to support that, but there is also no evidence that this is slowing down. We just see it getting bigger and bigger.”
I feel frustrated that I can’t find more certain predictions, but I have to accept that I am at the frontier of knowledge. What we do know is that there is a very large threat (add West Antarctica to Greenland, plus the inevitable expansion of the sea as it warms, and you are looking a rise in global sea levels of sixty feet) which may arrive over thousands of years, but which is showing some signs of arriving sooner rather than later.
To seek a little comfort among all this uncertainty I turned to Tad Pfeffer, professor of engineering at the University of Colorado at Boulder, 14 who has done something very clever. He drew together surveys of the bottom topography of the big glacier outlets around the world and added numbers on how fast the glaciers could go. That provides a good guess of the maximum amount of ice that could come pouring out of them. He told me that the worst case is two and a half feet (and that’s a maximum, not a prediction) this century. His result has been controversial. It suggests that some alarming predictions are unjustified but the limit is much higher than the IPCC’s now rapidly aging view. If we came close to that limit, that would be pretty serious, especially if you are Dutch. You will need to move to another country.
In the changing Arctic we never quite know how many more surprises are waiting for us. We knew nothing of high-speed Arctic glaciers a few years ago. And until just a couple of years ago, we had no real idea that as the Arctic warmed, methane would begin fizzing out of its innards and into the atmosphere. Methane is a powerful greenhouse gas, but unlike carbon dioxide, it does not stay in the atmosphere very long. It packs a very strong but short punch. Now we know that methane is bubbling out of ponds in the tundra and out of the Arctic’s shallow warming seas in places where it had never been seen before.
I had seen gas bubbling out of small lakes on a warm day in Alaska but was not at all sure whether it was methane. Somehow, among the 16,000 scientists who showed up at San Francisco’s Moscone Center for the fall 2008 meeting of the American Geophysical Union (a record for one of the largest science conferences in the world), I managed to find Katey Walter, an expert on bubbling lakes from the University of Alaska. It wasn’t really so hard to find her as I knew what she looked like; although only a few years out of grad school, she’s already published papers in Nature and Science and I’d seen her on television.15
I asked how I would know if I saw methane, expecting a reply along the lines of, “Collect the gas and take it to a laboratory equipped with a mass spectrograph.” Instead, she gave me instructions: “Hold out a lighted match. If it’s 10 percent methane or more it will burn. But be careful. I’ve seen eyebrows go. I’ve seen a big piece of my hair fly off and burn.”
Walter is an unusual person, with a love of the outdoors and Russia. She explained that she went to Russia as a high-school exchange student, learned the language, and became “very passionate” about the nation. When a chance came to go from Alaska to work in Siberia at the Northeast Science Station in Cherskii, she grabbed it. Cherskii is in the furthest reaches of Yakutia and about as remote a spot as you can find on the planet. It is also very cold; mean January temperature is-38°C. Winter walks on frozen Siberian lakes helped Walter to answer that question of how much methane was bubbling from lakes. “The surface cover of ice trapped all the gases,” she explains. “It’s transparent so I could walk across the ice and see all these hot spots of methane bubbling. I knew how many there were and how strong they were.” With the ice to help her find the methane, she could use an umbrella-shaped trap to measure their power. “It was very simple but it worked,” Walter says.
The amount of methane proved far greater than anyone expected—and once again it hadn’t been included in any of the climate models. Plus, the lakes don’t stand still. “The lake just grows,” explains Walter. “The Russian word for it is ‘eats the permafrost.’ And I love it because it’s right. If you look along the edges of these lakes they are not nice and smooth. They are rough, as if someone is taking bites out of a cookie. The lake water is warmer and it migrates across the surface by eating the permafrost, digesting the materials and burping out the methane.”
The methane is created when permafrost—the frozen ground just beneath the surface—melts, allowing microorganisms to break down its rich store of organic material. “More methane increases global atmospheric temperatures and causes more permafrost to thaw,” says Walter.
With any discovery like this, two questions immediately leap to mind: has anything similar happened before in Earth’s long history that might give us clues about what will happen next, and how big the impact might be? Walter looked back to the “scars of old lake basins” that cover the Arctic, worked out estimates of when they formed, and found they corresponded with a surge in methane levels at a time when the earth was warming rapidly 14,000 years ago. Arctic lake methane might have been an important trigger in past climate change alongside methane from expanding wetlands.16
She has since expanded her studies of lakes to North America in addition to Siberia. Currently, Walter says, the permafrost lakes add 25 teragrams of methane to the atmosphere. “It isn’t a huge number but it is a large number, given that the total methane entering the atmosphere from everywhere in the world is about 560 teragrams. And it’s a source that hasn’t been accounted for yet. If the future pattern of lake thaw is consistent with what happened in the past, then permafrost thaw lakes could be adding 50 teragrams of methane a year if they thawed over thousands of years, or 500 teragrams a year if they thawed over hundreds of years.” Which will it be? “Our understanding of how these lakes form and grow says it is a centuries timescale,” says Walter. “Although, if you really warm permafrost and start it going, it could go quickly. So I don’t know for certain. Is it one hundred years or one thousand years?” She leaves the question with me.
I quickly find I have a bigger lake to worry about when I meet Igor Semiletov, an oceanographer from the Russian Academy of Sciences. He is also at the giant conference and has recently returned from a series of ocean cruises off the coast of Siberia with a troubling tale. “We found huge bubble clouds of methane in water columns in the Laptev Sea and the East Siberian Sea,” he explains. “Permafrost lies under 80 percent of the entire area; we didn’t know that this huge carbon pool is extremely vulnerable.”
These shallow seas have formed quite recently. Ancient permafrost, once part of the land, is now under the sea and may come into contact with water that can thaw it quickly. With more than 75 percent of the area under less than 130 feet of water, says Semiletov, escaping methane can bubble out into the atmosphere before it has time to dissolve in the water. I ask him, “When did this start?” He didn’t see anything like this on trips in the 1990s, he says, and thinks that “the subsea permafrost is in a transition phase now.” More worryingly, Semiletov adds that the permafrost is “failing to seal ancient carbon, which includes methane hydrates and natural gas.”
A conversation with Semiletov feels a bit like being passed a series of hand grenades. You are just praying that no one has pulled the pin out of any of them. Methane hydrates are Earth’s real climate bomb.17 I have a little indirect experience with them. Up in the Shetland Islands, north of Scotland, there is a quiet little bay I like to walk around. Heading inland a little, you’ll find something very odd. Streams cut though the ancient peat, and, high up in a dark rill, there is a thin layer of what looks like sand sandwiched between layers
of the black peat.
A professor of geography at the University of Oxford called David Smith has looked at this sand very closely. “It was laid down when a tidal wave hit Shetland around eight thousand years ago,” he says. From the gradation of the sand particles he could work out how it settled and how deep the water must have been above it. The answer is that the wave washed up water at least a hundred feet deep. That tsunami was caused by a huge underwater landslide on a steep shelf off the coast of Norway. One candidate for triggering that landslide is the warming of methane hydrates.
The seabed in that region of Norway is rich with hydrates, a frozen form of methane in which the gas is trapped in an icy cage. It will only be released if it is warmed or if the pressure falls. Around the time that the tsunami hit, the sea had warmed. Did it trigger a sudden release of methane which in turn, triggered the slide? The idea is controversial but it does tell you something about the nature of the seabed methane hydrates. Left alone, they are quite safe. But if they are warmed, they may be released in a sudden burst. And there are a lot of them: if just 10 percent of the world’s methane hydrates were released over a few years, it would be the equivalent of increasing atmospheric carbon dioxide concentrations tenfold. The impact would be catastrophic.
I ask Semiletov if there is a real risk of releasing methane hydrates in the area he has visited. “The only thing stopping gas hydrates being disturbed and released to the atmosphere is the existence of subsea permafrost. If the subsea permafrost fails, all this hydrate would be released. If that happens, the world will be changed. There are at least five hundred gigatons of hydrates stored in the Siberian Arctic shelf area. In the atmosphere, we have less than five gigatons of methane.” Is it hundreds or thousands of years away? “I don’t know,” says Semiletov, “we do not have enough data. Too few people have looked under the sea.”
After the Ice Page 26