Read Online With Speed and Violence: Why Scientists Fear Tipping Points in Climate Change by Fred Pearce - Free Book Online
Authors: Fred Pearce
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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 tempera tures 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 group of twenty-one of them began in almost apocalyptic terms: "The Arctic sys tem is moving to a new state that falls outside the envelope of glacialinterglacial 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 'superinterglacial' 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
"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 tempera tures 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 group of twenty-one of them began in almost apocalyptic terms: "The Arctic sys tem is moving to a new state that falls outside the envelope of glacialinterglacial 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 'superinterglacial' 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
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