Antarctica

by Gabrielle Walker

  And yet, there was no way to know for sure. This whole region of West Antarctica is appallingly hard to study. For one thing, it’s perfectly positioned to evade scientific scrutiny. Although the Amundsen Sea Embayment is not much more than 1,000 km from the main British base on the Peninsula, that puts it just beyond the comfortable range of the British Antarctic Survey’s Twin Otter aircraft. The Americans could reach that far with their ski-equipped Hercules planes, but McMurdo is further away, again just far enough to put it out of reach.

  And even if it were closer to one or other of these major research centres, reaching it would still be challenging. The region’s speeding glaciers—called Thwaites, Pine Island and Smith—fill the bay with icebergs and help choke it up with sea ice for eleven months of the year, deterring all but the bravest of captains from entering by ship. And the heavy snowfall that feeds these glaciers comes from clouds that sock the place in for most of the year, discouraging planes and fogging the vision of satellites that might otherwise have been able to take stock from space.

  This mysterious third of the West Antarctic Ice Sheet couldn’t have done a better job of keeping out of the scientific limelight if it had tried.

  But then, in the 1990s, the European Space Agency launched the European Research Satellites (ERS-1 and -2). Unlike previous satellites, these carried radar instruments capable of firing radio waves through the clouds to reflect off the ice beneath. They also made two passes over the same piece of surface, about a month apart. By comparing the measurements from one pass to the next, researchers could derive a very accurate measurement not just of the height of the ice, but of changes in that height. If the ice were thinning, or if the hinge line were moving, the new satellites should be able to tell.

  And they did. In the late 1990s NASA scientist Eric Rignot from the Jet Propulsion Laboratory in California put together images of the front end of Pine Island Glacier from 1992 to 1996. By looking for the places where the floating ice moved up and down with the tides, he managed to track the hinge line, the place where the glacier started to float. And he discovered that in just four years its hinge line had retreated inwards at more than a half mile per year.9

  His paper, published in July 1998, caused a sensation. Other scientists pored over the satellite results, hastily publishing a blizzard of papers in all the best journals. And they all pointed to massive change in the Amundsen Sea Embayment: Pine Island Glacier’s floating hinge line was indeed moving inland, and the grounded glacier itself was shrinking, losing nearly six feet of height per year. And it was moving faster every year. Thwaites Glacier’s hinge line was also moving inland. And it was thinning, too. In fact, all the glaciers flowing into the Amundsen Sea were thinning. And Thwaites was getting steadily wider. And every year, more and more of the West Antarctic Ice Sheet was rushing out through that unwatched side door and tipping into the Amundsen Sea.10

  If only one of the glaciers had been affected, it could have been something local—a particularly soft bed to slide on, or extra heat coming from below. But this synchronised thinning needed something more general, something from the outside. Eric suspected the oceans. He teamed up with two British scientists, Andy Shepherd and Duncan Wingham, to look at the satellite data from those small floating ice shelves just off shore.11 They found that all three shelves in the bay showed that they had been getting thinner, by an impressive eighteen feet per decade.12

  Marine geologist Stan Jacobs thought he knew why. Most of the seawater around Antarctica is very cold. The freezing air sucks warmth out of the surface waters, taking it close to 28°F, the point at which salty seawater can freeze. But deeper down is a band of warmer water, protected from that cold air, that hovers at a relatively toasty 34°F.

  This warm deep water doesn’t usually get a chance to approach the ice too closely. It is held back by a gigantic underwater shelf that skirts the entire continent. But in the Amundsen Sea there were a few weak points in this natural defence, channels gouged out in the sea floor in the past, when the ice sheet was bigger and the glaciers stretched out much farther than they do today. Back in 1994, Stan had managed to battle his way into Pine Island Bay by ship, and get up to the front of the Pine Island floating shelf. There he found that warm water had crept up through these channels and was lapping right up against the shelf, where it had no right to be.

  Perhaps, then, it was this unusually warm water that was doing the damage. Still, the data from the 1994 cruise gave just one snapshot in time. In January 2009 Stan decided to go back, in the National Science Foundation’s icebreaker, the Nathaniel B. Palmer. This time, he found the water near the shelf was warmer still, and the shelf was melting even more dramatically. Stan calculated that the melting rate had increased by 50 per cent in just fifteen years. But why?

  With him on the ship was Adrian Jenkins from the British Antarctic Survey, who had already tried several times to get into Pine Island Bay. He was desperate to look underneath the ice with a specially designed autonomous submarine, Autosub3. This clever beast is twenty feet long, does not need to be tethered, and can go for more than thirty hours before having to return to the ship. It sends out sound waves to scan the ice above and the sea floor below. It can look into the darkest, murkiest, most inaccessible corners of the ocean beneath the ice, see things that no other instrument can see, and still come back when called. It is the hunting dog of the submarine world. And although nobody actually lives in it, it is also pleasingly yellow.

  Dealing in autonomous subs is risky. They are unattached and beyond a couple of miles you have no way of speaking to them. The Autosub engineers had already lost a previous prototype under a small ice shelf.

  But if you want a true picture of what’s going on under these ice shelves, you have to take the risk. The technicians from the National Oceanography Centre in Southampton, UK, who had lovingly designed and built this and the previous machines, could only give it instructions, release it from the ship—and hope.

  At first the missions went well. The little yellow submarine sank below the waves, headed off to the Pine Island Ice Shelf, and chose a careful path underneath the ice, mapping the sea floor on the way out and the ice’s underbelly on the way back. Three times it went, each time penetrating twenty miles—which was halfway along the shelf.

  On 24 January came the final mission, the big one. In this, Autosub3 was to go as far as it could get, mapping the shelf all the way to the hinge line where the glacier started to float. This trip would be the most dangerous. The sub would have to decide for itself how far was too far, and turn back before the water was so shallow that it would be trapped. The researchers released it into the water, and for the next thirty-six hours they waited.

  Autosub3 hummed along in the semi-darkness, broadcasting its sound waves, picking up and storing the echoes, making careful adjustments to stay a safe distance from both ice above and sea floor. Now it was beyond twenty miles, in uncharted waters, heading towards that hinge line where ice met water met mud. Closer it drew, broadcasting and receiving all the way, keeping a weather eye on the depth, until its instruments warned it that the water was only 650 feet deep. Time to turn. The sub safely rotated and rose up towards the ice to begin its journey home. Going out it had mapped the sea floor. Now it was supposed to study the underside of the ice shelf. That was OK. It knew how to stay safely 300 feet below the ice, how to keep out of trouble.

  But something was wrong. Its collision avoidance system detected an obstacle ahead. Again, the sub knew what to do: retreat about a kilometre, adjust its direction slightly, and try a different route to avoid the obstacle. Back it motored and BANG! There was something behind. Collision avoidance needed. Move forward. CRASH! Backwards, forwards, the submarine barged helplessly, trapped inside a narrow ice fissure that its sonar hadn’t detected and its brain couldn’t understand. It was getting battered now, its fibreglass casings scratched, its aluminium wings bent and twisted. BANG! CRASH!

  And then, something else kicked in. Luckily the
engineers had programmed one last piece of wise advice into the Autosub’s mental circuitry: ‘If something isn’t working, stop trying.’ The sub finally admitted to itself that the collision avoidance strategy had hopelessly failed. It dropped deeper down into the water, and headed for home.13

  The first the researchers knew of this drama was when they lifted the sub out of the water and saw how battered and bruised it was. But the data it contained was intact. And when put together with the data from the other missions, it showed something fascinating about the Pine Island Glacier Ice Shelf, something that would help explain why it was melting at such an astonishing rate.

  There was a ridge. About halfway into the shelf a mound of sea floor, running parallel to the shelf front, rose up to within a few hundred metres of the overhead ice. When Stan rushed back and looked at satellite pictures from the 1970s of the ice shelf from above, he found a lump on the ice in exactly the same place. But the lump wasn’t there now. The shelf must have been stuck on this ridge, pinned there, until the warm deep waters that had crept into the bay had melted enough of it away that it could float free. Now the warm water was unchecked. It had rushed into the far side of the shelf, right up to the hinge line, and was hollowing out a huge cavity, like a rotten tooth. No wonder the ice was melting and the hinge line receding.14

  This is all very troubling. It’s the first time ever that melting of ice on land has been directly connected to something in the outside world that we know is changing. As the world warms, the deep water around the fringes of Antarctica is already getting noticeably warmer, and models predict this will continue.15 And the warmer the water, the more effectively it can eat away at the hinge lines of the Amundsen Sea glaciers, lowering the resistance of the ice shelves, and allowing the land ice behind them to accelerate into the sea.

  So the seas are eating away at the Amundsen Sea glaciers from the coast. Now we need to know how far this can go. That depends on what’s happening underneath the glaciers themselves. If the land beneath them really does slope downwards all the way to the interior then there would be nothing to stop this process eating all the way into the heart of the West Antarctic Ice Sheet.

  Two research groups—one from the UK and one from the US—have recently shed light on this question, and the news is both good and bad. Veteran Antarctic glaciologists David Vaughan from the British Antarctic Survey and Don Blankenship from the University of Texas at Austin have long been studying their respective sides of the West Antarctic Ice Sheet. David probably knows more than anyone alive about the activities of the ice streams feeding the Ronne Ice Shelf, and Don has been studying the Siple Coast for decades. When they realised the problems with the Amundsen Sea Embayment, the two decided to join forces. Both had survey planes, bristling with instruments, capable of criss-crossing a body of ice and measuring its height, its thickness and what lies beneath. They would take the two planes to the inland part of the Thwaites/Pine Island area. David would study Pine Island Glacier. Don would study Thwaites. And they would put the answers together.

  Since their camps were fairly far from the coast, the weather wasn’t too bad, but the operation still stretched the resources of both Rothera and McMurdo. But the results justified the effort. The good news came from Pine Island. Though David discovered that the ground beneath this glacier did indeed slope downwards as it went inland, there was a natural limit. At a certain point, the land rose into a ridge. That meant the meltdown of the glacier could only go so far before geography would intervene. He calculated loss of all the ice in the vulnerable basin would lead to a global sea level rise of about eleven inches, which would be serious but not necessarily catastrophic. Moreover, the trunk of the glacier was confined to a trough, stopping it from getting any wider.16

  However, the news from Don’s investigations of the Thwaites Glacier wasn’t quite so good. He found that there was nothing to stop Thwaites going all the way. Moreover, there was no trough beneath Thwaites, which means that it wasn’t nearly as confined. Melting there could spill over, allowing seawater to flood into the apparently safe upper basin of the Pine Island Glacier, and even perhaps over to the ice streams on the Siple Coast.17

  If the whole region collapsed in this way, we’re now talking a sea level rise of about five feet. That’s not as bad as the twelve feet originally feared. But when added to the sea level rise expected from melting ice in Greenland it would still be enough to cause death and destruction, particularly among the many millions living on low-lying deltas in the developing world.18

  All this is very new and fresh and there is a lot left to learn. It matters, of course, how long the melting might take. If the world’s seas rose by five feet within a few decades, that could be devastating. If it took centuries, we might be able to adapt. However, the news from Antarctica’s weak underbelly is that change is definitely happening, and at a rate that otherwise conservative researchers find alarming.

  The fate of the Amundsen Sea glaciers has become the hottest topic in Antarctic research, tied up as it could be with the fate of us all. And as we digest its implications, we could do well to remember the experiences of the man who first flew over and named this empty terrain more than seventy years ago. He had his own way of assessing his adventures. I would summarise them in this way: ‘Learn what you can from Antarctica, but don’t ever underestimate it.’

  Admiral Richard Byrd, soldier, aviator and explorer, was already a hero in America when he arrived in Antarctica on 17 January 1934. He came from a proud Virginian family, and at the age of twelve had travelled alone around the world, stopping to visit family friends in outlandish outposts. As an adult he had fought bravely in the First World War, flown across the Atlantic—just barely scooped by Charles Lindbergh from being the first—and flown to the North Pole.

  Then he had come south where, on his previous expedition, he had flown to the South Pole, and had flown over and mapped much of West Antarctica. (He named the western part of the ice sheet Marie Byrd Land in honour of his wife. It is so remote that in spite of the attempts at land grabs by various nations before the Antarctic Treaty came into force, nobody wanted this part, and it remains the largest unclaimed territory on Earth.)

  Byrd’s plan this time was to spend the winter on the Ross Ice Shelf, where he could sail in with his supplies yet still be within flying distance of West Antarctica; when summer came he would then continue exploring this great empty western ice sheet.

  Most of his men were to pass the winter at a well-established base that he called Little America, close to the coast. But Byrd became consumed by the idea of establishing a small outpost a hundred miles inland, where we now know that the Siple Coast ice streams spill out on to the shelf. Scientifically, he wanted to measure the inland weather through an Antarctic winter, and see if this could help explain the weather patterns at the coast. Personally, he was captivated by the idea of establishing the first inland wintering station on the continent.

  So, he sent a tractor train limping south over the ice from Little America, skirting crevasse fields and feeling its way into the heart of the Barrier. They stopped about 130 miles from Little America, dug a great hole and sunk a prefabricated hut deep into the snow. But when the trip was delayed, making it impossible to do a second supply journey to equip the hut for the three occupants Byrd had originally envisaged, he promptly decided to be dropped off by plane and spend the winter there himself—alone.

  Even today, it is hard to find yourself alone anywhere on the continent. For safety’s sake the stations that I visited refused to let anyone out of sight of the camp without a companion. In Byrd’s time, when there could be no possible hope of rescue if anything went wrong during the long polar night, his decision was extraordinary. Perhaps he was tired of all the effort and the adulation, the necessities of glad-handing and fundraising and being a society darling for rent the moment one expedition finished and he needed to pay off its debts and start planning the next.

  He wrote:

  Out there on
the South Polar barrier, in cold and darkness . . . I should have time to catch up, to study and think and listen to the phonograph; and for maybe seven months . . . I should be able to live exactly as I chose, obedient to no necessities but those imposed by wind and night and cold, and to no man’s laws but my own.19

  In the first few days, his only complaint was that he had forgotten to bring a cookbook. Never having had to cook anything for himself before, he was hamstrung. He wrote in his diary about the ‘Corn Meal Incident’ in which he overdid the amount of corn meal in a pan and induced a volcanic reaction. ‘It oozed over the stove. It spattered the ceiling. It covered me from head to foot. If I hadn’t acted resolutely, I might have been drowned in corn meal.’ He grabbed the pan, rushed it to one of the storage tunnels and slammed it down, where it continued to spew until it froze.

  Byrd recounted these incidents insouciantly to the men back in Little America on his thrice-weekly radio calls. He could hear their actual voices but he had to reply laboriously, spelling out his messages with the dots and dashes of Morse code. His men teased him about his incompetence with the code, especially when he was asked to broadcast a message live to the Chicago World’s Fair, to be relayed via Little America and then somehow translated into a firework display. ‘If the fireworks are supposed to spell out what you send,’ his friend Charlie Murphy told him over the radio, ‘then Chicago is in for the wildest display since the fire.’