After the Ice

by Alun Anderson

  Ice caught in the Transpolar Drift Stream has a different fate. Like Papanin’s North Pole 1 drift station, it will travel across and out of the Arctic, be devoured by “black snakes” off the coast of Greenland, and melt clean away. The Transpolar Drift Stream destroys ice.

  With that picture in mind, we will leave behind the heroic age of Arctic science and move into the satellite era. Ice drift camps have not entirely disappeared from the modern age. After a long break, Russia is continuing its tradition, although in 2008, drift camp North Pole 35 had great difficulty in finding a suitable chunk of thick ice left anywhere in the Arctic. So did lots of other researchers who wanted to leave instruments on the ice, prompting many tales of scientists from different ships fighting over the best bits of ice left in the Arctic.

  To chart movement of the ice now, buoys can be left out on the ice to be tracked by satellite. The cleverest of these buoys, the “Ice-Tethered Profilers,” don’t just sit on the ice. Beneath them, a wire rope over 2,000 feet long passes through a hole in the ice and down to the depths below. A couple of times a day, a long cylindrical package attached to the wire crawls slowly up and down its length. It is powered by a lithium-battery electric motor, “the same little electric motor that NASA picked to drive a rover around Mars,” says John Toole, the scientist at Woods Hole Oceanographic Institution who designed the machine, and it is so efficient that it can “drive those instruments the distance from Boston to New York and back.” Inside the package are sensors that measure the key parameters of the ocean, the temperature and the salinity at different depths. Up on top, an Iridium phone dials the laboratory at Woods Hole and sends the results to a Web site. You can just click on a map of the Arctic to see where the buoys are going and what they are finding today.

  There are many other buoys out there too; gradually the Arctic is being wired as the age of autonomous exploration machines is arriving. Along with machines on top of the ice, others float freely beneath it, and there are sensors moored to the bottom of the seafloor as well as robot submarines, and underwater gliders that can travel under the ice for months on end, collecting data as they go.10 Many of the new Arctic explorers need scarcely leave the comfort of the cozy labs; Nansen and Papanin would have found such ease hard to imagine.

  Scientists first began to suspect that something was going wrong in the Arctic back in the 1980s. Satellite pictures showed that the area of the Arctic ice at the end of each summer was smaller than it was in the years before, although the area of ice at the end of winter scarcely changed at all. That trend was hidden amid large annual ups and downs. In 1983, the sea ice at the end of the summer covered 2.9 million square miles (7.5 million square kilometers). For comparison, the entire United States has an area of 3.5 million square miles (9.2 million square kilometers). But two years later this ice cover shrank to 2.6 million square miles (6.8 million square kilometers). The following year it rose again to just where it had been in 1983 and stayed there for another two summers. After many wobbles it was at 2.4 million square miles (6.1 million square kilometers) in 1995. Overall though, the trend was downward. The summer ice was losing about 8 percent of its area per decade and scientists needed to find an explanation.

  The earth was beginning to warm and the Arctic more so: the words “greenhouse effect” and “global warming” were just entering the vocabulary. But the slightly higher temperatures that the Arctic was then seeing were not sufficient on their own to explain why the summer ice melt was gradually accelerating. Each winter, the ice returned to close to its usual area. So much ice could not be melting away in summer simply because the air was a little warmer. Something else must be going on and, in the 1990s, scientists turned to an explanation that links straight back to the discoveries made by Nansen, Papanin, and all those explorers who had followed the flow of the Arctic’s ice.

  Satellite maps show that the Transpolar Drift Stream and the Beaufort Gyre are not separate. The outer waters of the gyre connect to the drift stream and other routes out of the Arctic, including the Nares Strait that leads down between Greenland and Canada’s Arctic islands and out through Baffin Bay and the Davis Strait. If the Beaufort Gyre tends to build ice and the Transpolar Drift Stream tends to carry it away, then it is easy to see that the balance between those two processes could be very important in determining how much ice is left in the Arctic. The two streams are driven by the winds, which are related to the pattern of the high- and low-pressure weather systems that surround the Arctic. In 1989 scientists began noticing that a pattern of winds and weather had set in that favored the export of ice out of the Arctic, rather than its retention in the Beaufort Gyre. This is the “positive phase” of the Arctic Oscillation, a pattern of atmospheric pressure differences between the Arctic and the middle latitudes. When the Arctic Oscillation enters its “negative phase,” surface winds within the Arctic blow clockwise and tend to keep ice trapped in the Beaufort Gyre, where ice can grow and strengthen. In the positive phase, the clockwise winds weaken, allowing ice to slip out of the Arctic through the Transpolar Drift Stream and the Fram Strait.

  The positive phase that began in 1989 was much stronger than usual and continued for seven years, right through until 1995. Nothing like it could be seen in the weather records of the previous hundred years. Normally the oscillation behaves as its name suggests and swings back and forth as the years pass. As a consequence, the ice gains in some years and loses in others. Trapped in a long positive phase, wind patterns conspired to steal ice from the Arctic and ship it off to melt in the Atlantic.

  The odd behavior of the Arctic Oscillation seemed to provide an explanation for the loss of ice, but the explanation was soon found to be incomplete. The Arctic Oscillation returned to pretty much its normal behavior, although the oscillation was weaker than before, but the ice did not recover. After an exceptionally cold winter, the summer minimum in 1996 hit 3.1 million square miles (8 million square kilometers), an amount not seen since 1980. Then the downward trend continued and intensified. By 2006, the area was down to 2.2 million square miles (5.7 million square kilometers), lower than it had ever been before.

  There was clearly more to the disappearance of the sea ice then a simple link to the changing wind patterns of the Arctic Oscillation. One view was that the seven long years of the positive phase of the Arctic Oscillation had stripped the Arctic of its older, thicker multiyear ice that would have been built in the Beaufort Gyre. Left with too much thin newer ice that melted more easily, and too little strong ice that could withstand the summer warmth, the Arctic ice simply could not get back on its feet. It had been hit too hard.

  Then the year of the catastrophic crash arrived and shook up the whole science community. In September 2007 the summer ice shrank to just 1.7 million square miles (4.3 million square kilometers), down from 2.3 million square miles (5.9 million square kilometers) the year before and close to half of what it had been in the 1950s and 1960s. Compared to that period, an area of sea ice had been lost that was almost ten times the area of California.

  Even in 2006, scientists at the U.S. National Snow and Ice Data Center had been predicting that the Arctic Ocean would have no ice in September by the year 2060.11 Now they didn’t know where the melt was leading.

  Bigger explanations were needed, and the 2007 crash started a frenzy of analysis. Everyone did know that one essential part of the puzzle was incomplete. Looking down at the area of ice in the Arctic, all you are seeing is a two-dimensional picture. A three-dimensional view that shows the volume of the ice is what is needed. Thin ice will obviously melt away faster than thick ice, so if we don’t know how much ice is hiding beneath the water, the future is going to be very hard to predict.

  Before moving on to see what is known about ice thickness, and why it is so frustratingly difficult to obtain the data that are so important, we should register that we have found a clear suspect in the case of the disappearance of the Arctic ice. A direct link between the Arctic Oscillation and the loss of sea ice may ha
ve gone dead, but it is plain that the pattern of Arctic winds, the pattern of high- and low-pressures around the Arctic, can have a big impact on what happens to the ice and whether it stays in the Arctic or departs. The movement of the ice, its dynamic side, will remain a part of any larger explanation of the disappearance of the ice, and has another consequence which we will explore later.

  We don’t know nearly as much as we would like about changes in the thickness of the ice. Christian Haas at the University of Alberta in Canada has probably spent more time trying to measure the thickness of Arctic ice than anyone else on the planet. “What we are really missing as we try to understand the recent changes and improve our forecasts is ice thickness information and the means to go out there and gain that information,” Haas told me at the end of 2008. The first time I talked to Haas, in late 2007, he had just moved to Canada from his home at the Alfred Wegener Institute in Germany and he had a grand plan to travel across the Arctic in a French airship. The airship would be towing his “electromagnetic [EM] bird” on a long cable so that it flew just above the surface of the ice right across the Arctic. The EM bird looks like a long cylinder with a tubular tail, but inside are electronics to generate an electromagnetic field that can measure the precise distance to the water hidden beneath the ice. A laser beam bounced off the surface of the ice measures the distance to the top of the ice, and combining the two gives a reading of the ice thickness. Haas had already flown numerous helicopter missions, but each was of limited range. The airship trip would have given Haas a thickness map of a big section across the Arctic. Sadly, it never happened. The airship was torn from its moorings in a storm while in France and crashed into a house. No one was hurt, but the project was over before it began. “It was very disappointing,” says Haas.

  Just a couple of years earlier, the European Space Agency launched the Cryosat satellite, equipped with a highly sensitive laser altimeter which would have been capable of measuring the height of the ice above sea level across most of the Arctic, from which the ice depth could be calculated. Seventy-six seconds after liftoff, the Russian rocket carrying Cryosat malfunctioned and the satellite plunged into the sea near the North Pole rather than orbiting above it.

  “After these disasters, I began to wonder if the Arctic has some kind of curse on it—it’s not supposed to be surveyed, and its secrets must never be uncovered,” Haas told me. Despite the setbacks, though, he and his team succeeded in flying 12,000 miles above the ice near the North Pole, towing their EM bird behind a helicopter and later an airplane to measure the thickness of the ice.

  That mission added to other methods for measuring ice thickness, many of them very ingenious and all still very incomplete. To understand them it is best to begin by going under the ice and looking upward, taking a view of the Arctic that for more than fifty years was a secret known only to the nuclear submarine fleets of Cold War navies.

  Chapter Five

  THE VIEW FROM BELOW

  Long before scientists began to worry about what was happening to the ice, the nuclear submarines of the U.S. and Soviet navies already knew the Arctic intimately. Their attack submarines constantly prowled under the ice, testing one another’s defenses, spying on naval bases, maneuvers, and bomb tests, and searching for one another. Tracking an enemy submarine without being detected required consummate skill and a detailed knowledge of the seabed’s ups and downs, its hiding places, and its danger points. As the Cold War progressed, the Soviet Union developed submarines that could launch nuclear-tipped ballistic missiles, making mastery of the world under the ice of the Arctic ever more urgent. Very little that the U.S. Navy learned about the Arctic’s bathymetry and the state of its ice could be passed on to scientists in those days; to reveal anything of what they had seen would be to reveal where they had been. That could only help the enemy track them down.

  Submarines continue to prowl even now that the Soviet Union has become the Russian Federation. Occasionally, they go too far. In 1992, the U.S. nuclear attack submarine USS Baton Rouge collided with a Russian submarine just off the Russian Northern Fleet’s main base at Murmansk. The Russians claimed the collision was inside their waters; the Americans denied it. Both submarines limped back to their bases, and the mission of the USS Baton Rouge was never revealed. A year later the USS Grayling hit a Russian submarine that it was trailing in the Barents Sea. This time the collision could have been more serious as the Russian vessel is believed to have been carrying nuclear-tipped ballistic missiles. Both submarines returned safely.

  Big efforts have been made to create detailed but secret charts of the sea bottom. As early as 1970, a nuclear attack submarine, the USS Queenfish, sailed under the ice along the entire coast of the Soviet Union mapping the contours of the seabed as it went. On its journey through the frozen Laptev, East Siberian, and Chukchi seas, the submarine could rarely surface safely, although it did manage to take pictures of polar bears on the ice through its periscope. Its voyage, now almost forty years old, is one of the very few of which there is a public account.1

  Captain Alfred McLaren records how his submarine crossed the shallow seas, navigating quietly around pingos (small hills pushed up by ice under the sea bottom) while keeping below innumerable deep-draft ice keels protruding like stalactites from the thick ice above. The submarine was almost 300 feet long, with 117 men on board, yet it sneaked under the ice with just 30 feet above its sail and 20 feet below. Among the features they found beneath them were deep ice scours running across the sea bottom, probably caused by giant icebergs. Scientists would have loved to have heard more about them, but they had to wait. McLaren records a more practical interest, noting that they could be used as “pre-launch safe havens for ballistic missile submarines.”

  With the minds of U.S. submariners on the serious issue of winning the Cold War, scientists who wanted to obtain submarine data from them would have to wait—more than forty years from the first submarine cruise under the ice, as it turned out. In the meantime, they turned instead to Britain’s Royal Navy submarines, which made their first underice cruises in 1971. Peter Wadhams of the Scott Polar Research Institute in Cambridge, England, was on that first trip thanks to the good connections of his laboratory chief, who had been a submariner in World War II. An odd twist, though, was the source of his funding.

  “My own work on board British submarines was funded largely by the U.S. Office of Naval Research,” Wadhams told me. “They wanted to see submarine data, and they couldn’t get hold of the classified U.S. Navy data either.” Wadhams has continued to make submarine voyages to look at the ice, right up to his most recent trip across the Arctic in 2007.

  Flying above the ice, says Wadhams, you’ll see smooth, frozen seas surrounded by pressure ridges where colliding ice floes have pushed up walls of ice. Overall their pattern recalls an aerial view of the old English countryside with “ancient fields surrounded by tumbledown walls.” From below, the view is different. Beneath the pressure ridges are enormous ice keels, many between 30 and 60 feet deep and some even reaching 150 feet. Their size, Wadhams explains, means that they make up about half of the volume of the ice in the Arctic even though they are totally invisible from above. The keels begin as little more than underwater rubble broken from the floes, but as time passes, currents polish, smooth, and harden them. As Captain McLaren recorded, navigating among them in shallow water is one of the toughest tasks for a submarine commander.

  Submarines use sonar to “see” the ice, and multibeam sonar is now the underwater eye of choice. Many narrow beams of sound are sent out in a fan shape around the submarine, and their echoes are recorded. As the millions of sonar pings return, they are converted into a three-dimensional map of the undersurface of the ice. “This is how you get the thickness, shape, and size of all the features,” explains Wadhams. A navy submarine cruising beneath the ice can map a 300-foot-wide swath of the ice above, and multiple overlapping tracks can quickly build three-dimensional maps of large regions of ice.

 
In the late 1980s, with several submarine cruises under his belt, Wadhams noticed a worrying trend in the data he was collecting. “I started to realize that when you went over the same ground again, the ice was thinner than it was before,” he says. Before then, no one had worried about the ice in the Arctic or thought that it could be at risk. But his submarine cruises along a line between the Fram Strait and the North Pole were showing him that the ice had lost an average of a little over two and a half feet of its thickness between 1976 and 1987. An area around Greenland had lost seven feet.2 Even though the area of the ice was yet to change dramatically when seen from above, Wadhams’ early work warned that the ice was already being eaten away in that hidden third dimension.

  Wadhams’ most recent trip was a 1,600-mile, 11-day cruise under the ice from Spitsbergen to Alaska on board the nuclear-powered HMS Tireless in the summer of 2007. Sadly, that cruise ended in tragedy when an explosion in the submerged submarine killed two sailors. “It was very frightening, for the crew as well, as nothing like this had ever happened before. For the first half hour nobody knew what had happened, but they did all the right things and followed their training,” Wadhams says. The accident happened near journey’s end, and most of the data had already been gathered. It confirmed what he had been saying for more than twenty years: the ice is growing thinner and thinner. Although it is the shrinking area of the ice that has grabbed all the attention, the volume of ice in the Arctic is disappearing even faster. “The cruise by HMS Tireless shows the average thickness of the sea ice has fallen by 40 percent since the 1970s,” Wadhams says.