Why melting knows no bounds in the far North
"Has anybody in history ever got to 90° north, to be greeted by water and not ice?" That was the question posed by a group of scientists after returning from a cruise to the North Pole in August 2000. Sailing north from Svalbard on one of the world's most powerful icebreakers, the Yamal, the researchers found very little ice to break. And when they got to their polar destination, they were amazed to find not pack ice but a mile-wide expanse of clear blue water.
The story went around the world. For some, it revived the tales of ancient mariners, who said that beyond the Arctic ice there was an open ocean, and beyond that a mystical land, an Atlantis of the North. The proprietors of the Yamal were quick to cash in, offering summer cruises to "the land beyond the pole." But for the less romantically inclined, the story of the ice-free North Pole ignited panic about Arctic melting. By chance, the scientists on board the Yamal had included James McCarthy, a Harvard oceanographer on summer vacation from chairing an IPCC working group on the impacts of climate change. He didn't want to be alarmist, he said on his return. The Arctic ice sheet is made up of shifting plates, so there are bound to be gaps. But there were more and more gaps. So the unexpected discovery was "a dramatic punctuation to a more remarkable journey, in which the ice was everywhere thin and intermittent, with large areas of open water."
The whole Arctic was remarkably ice-free that summer. And that included the Holy Grail of generations of Arctic explorers, the Northwest Passage. The search for a route from the Atlantic to the Pacific and the riches of the Orient excited early explorers almost as much as El Dorado. But it was a deadly pursuit. The ice swallowed up hundreds of them, most notably Sir John Franklin, whose 1845 expedition disappeared with all 128 hands. But in 2000, a Canadian ship made the journey through the Northwest Passage without touching ice. Its skipper, Ken Burton, said: "There were some bergs, but we saw nothing to cause any anxiety."
Inuit whalers the previous June told glaciologists meeting in Alaska that the ice had been disappearing for some years. "Last year it stayed over the horizon the whole summer; we had to go thirty miles just to hunt seals," said Eugene Brower, of the Barrow Whaling Captain's Association. Recently declassified data from U.S. and British military submarines had revealed that the Arctic ice in late summer was on average 40 percent thinner in the 1990s than in the 1950s. And NASA satellites, which had been photographing the ice for a quarter century, offered the most incontrovertible evidence. Their analyst-in-chief is Ted Scambos, of the National Snow and Ice Data Center, in Boulder, Colorado, a wannabe astronaut who turned to exploring the polar regions as a second best. He reports annually on how the retreat of ice is turning into a rout. In 2005, just 2 million square miles of ice were left in mid-September, the usual date of minimum ice cover. That was 20 percent less than in 1978.
The Arctic is a place without half measures. There is no midpoint between water and ice. Melting and freezing are, in the jargon of the systems scientists, threshold processes. Melting takes a lot of solar energy, but once it is complete, the sun is free to warm the water left behind. And, because it is so much darker, that water is also far better at absorbing the solar energy and using it to heat the ambient air. "This makes the whole ice sheet extremely dynamic," says Seymour Laxon, a climate physicist at University College London. "The concept of a slowly dwindling ice pack in response to global warming is just not right. The process is very dynamic, and it depends entirely on temperature each summer."
"Feedbacks in the system are starting to take hold," Scambos says. The winter refreeze is less complete every year; the spring melt is starting ever earlier—seventeen days earlier than usual in 2005. "With all that dark, open water, you start to see an increase in Arctic Ocean heat storage." The Arctic "is becoming a profoundly different place." Most glaciologists agree with Scambos that the root cause of the great melt is Arctic air temperatures that have risen by about 3 to 5°F in the past thirty years—several times the global average. Global warming, it seems, is being amplified here. This is partly because the feedbacks of melting ice create extra local warming. And partly, too, because of a long warm phase in a climatic variable called the Arctic Oscillation, which brings warm winds farther north into the Arctic. The Arctic Oscillation is a natural phenomenon, but there is growing evidence that it is being accentuated by global warming, as we shall see in Chapter 37.
There is another driver for the melting, again probably connected to global warming. Warmer air above the ice is being accompanied by warmer waters beneath. Weeks before Scambos published his 2005 report, Igor Polyakov, of the International Arctic Research Center, in Fairbanks, Alaska, reported on an "immense pulse of warm water" that he had been tracking since it entered the Arctic in 1999. It had burst through the Fram Strait, a narrow "throat" of deep water between Greenland and Svalbard that connects the Greenland Sea and the Atlantic to the Arctic Ocean. And since then, it had been slowly working its way around the shallow continental shelves that encircle the Arctic Ocean. One day in February 2004, the pulse reached a buoy in the Laptev Sea north of Siberia. A thermometer strapped to the buoy recorded a jump in water temperature of half a degree within a few hours. The warm water stayed, the rise proved permanent, and the Laptev Sea rapidly became ice-free. "It was as if the planet became warmer in a single day," Polyakov told one journalist.
Pulses of warm water passing through the Fram Strait may be a regular feature of the Arctic. They were known to the Norwegian explorer and oceanographer Fridtjof Nansen, who a century ago used a specially strengthened ship called the Fram to float with the ice and monitor currents in the Arctic. But as the Atlantic itself becomes warmer, the pulses appear to become bigger, and their impact on the Arctic is growing. One theory is that some of the water that once disappeared down the chimneys in the Greenland Sea now comes farther north into the Arctic.
"The Arctic Ocean is in transition toward a new, warmer state," says Polyakov. And most glaciologists working in the Arctic agree. Writing in the journal of the American Geophysical Union, Eos, in late 2005, a £rouP of twenty-one of them began in almost apocalyptic terms: "The Arctic system is moving to a new state that falls outside the envelope of glacial-interglacial fluctuations that prevailed during recent Earth history." Soon the Arctic would be ice-free in summer, "a state not witnessed for at least a million years," they said. "The change appears to be driven largely by global warming, and there seem to be few, if any, processes within the Arctic system that are capable of altering the trajectory towards this 'super-interglacial' state."
What would the world be like with an ice-free Arctic? Oil and mineral companies and shipping magnates long for the day when they can prospect at will, build new cities, and navigate their vessels in all seasons from Baffin Island to Svalbard and Greenland and Siberia. But it would be a world without polar bears and ice-dwelling seals, a world with no place for the Inuit way of life. And the influence of such a change would spread around the world. Without the reflective shield of ice, the whole world would warm several more degrees; ocean and air currents driven by temperature differences between the poles and the tropics would falter; on land, methane and other gases would break out of the melting permafrost, raising temperatures further; and as the ice caps on land melted, sea levels would rise so high that much of the world's population would have to move or drown. If the Arctic is especially sensitive to climate change, the whole planet is especially sensitive to changes in the Arctic.
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