Polar ice is melting at such an alarming rate the rest of the world can't help but feel the heat, reports Marian Wilkinson.
Before the summer heatwave hit Australia in January, climate scientists around the world were already turning their attention in our direction.
The popular belief that Antarctica might be resistant to global warming was punctured with new research based on data from satellites and weather stations, confirming that for the past 50 years, much of the continent has been warming at the same rate as the rest of the planet.
Antarctica is split into two huge ice sheets: east and west, separated by mountains. Because the Eastern Antarctic ice sheet has been extremely cold and stable, many believed it would hold down temperatures across the vast continent. But the new data found West Antarctica has been warming faster than previously believed, "meaning that on average the continent has gotten warmer", says Eric Steig, professor of earth and space sciences at the University of Washington.
Until recently it was mainly the fragile Antarctic Peninsula, jutting up from West Antarctica towards South
America, that was seen as vulnerable to global warming. The peninsula was already warming more rapidly than much of the rest of the world, with temperatures rising 2.5 degrees in the past 50 years and ice loss increasing 140 per cent in a decade. Around the peninsula, ice shelves have broken up or disappeared, exposing the glaciers on the land behind them and speeding up the discharge of ice and fresh water into the ocean. As Dr Ian Allison of the Australian Antarctic Division explains, this activity on the peninsula appears to be linked to air and water temperatures rising.
So far, Australian scientists say, the main Western Antarctic ice sheet, outside the peninsula, is still cold enough to resist the melting of its surface. If this 900,000-square-kilometre ice sheet were to succumb to melting, it holds enough ice to raise global sea levels by five metres, swamping coastal regions from the Indian sub-continent to south Florida.
That is not expected to happen in this century or even the next. But, disturbingly, glaciers on the Western Antarctic ice sheet are also discharging more ice and water into the ocean. Scientists are trying to find why this is happening, whether there is a link to global warming or whether there is a natural glaciological explanation.
The role of global warming in the melting of the Greenland ice sheet is clearer, says Allison, the co-chairman of International Polar Year, a global research effort that focused on the Arctic and the Antarctic during 2007 and 2008.
"Greenland is of major concern," Allison says. "In Greenland, the rate of ice loss is getting greater over the last 10 years and the surface [ice] melt is definitely related to the warming."
The Polar Year leaders concluded: "It now appears certain that both the Greenland and the Antarctic ice sheets are losing mass and thus raising sea level and that the rate of ice loss from Greenland is growing.
"The potential for these ice sheets to undergo further rapid ice discharge remains the largest unknown in projections of the rate of sea level rise by the (UN) Intergovernmental Panel on Climate Change."
Allison and many of the world's top climate scientists met in Copenhagen last week to update the warnings on climate change that the intergovernmental panel delivered in 2007. The findings, including the threat of sea-level rise, will be given to political leaders before they meet to debate the new global climate agreement at the end of the year.
When the UN Environment Program delivered its annual review on the planet last month, it gave a blunt warning on climate change: "The potential for runaway greenhouse warming is real and has never been more clear."
Among the danger signs noted in the report are the shrinking Arctic sea ice and the accelerating melting rates in Greenland and Antarctica. Last year, the Arctic sea ice shrank to its second-lowest extent since satellite monitoring began in 1979. The previous low was the summer of 2007. "Taken together, the two summers have no parallel," the report says.
In 2007 and 2008, an ice-free channel opened in the famous Northwest Passage in Arctic Canada, the passage where many colonial navigators perished when they were trapped by sea ice. But last year also marked the opening of the Northern Sea Route along the Siberian coast in the Arctic. "The two passages have probably not been open simultaneously since before the last ice age, 100,000 years ago," the report finds.
The Arctic is not only warming faster than most of the rest of world, the warming is feeding back on itself. As the reflective snow and ice disappear in the northern summer and are replaced by dark sea, more heat is being drawn into the Arctic. There are now some scientists predicting there will be an ice-free Arctic summer by 2012. More cautious scientists still say we could see this by 2030.
Dr Don Perovich, a research scientist with the US Army Cold Regions Research Laboratories, explained the enormity of this event in simple language: "You might say, 'Well, OK, what if we have an ice-free summer Arctic? Is that a big deal?' As near as we can tell, looking at the historical record, there's been ice in the Arctic in the summer for at least 16 million years, so this would be a big difference."
The ramifications of the warming will not be confined to the poles because weather patterns are likely to change. As scientist Mark Serreze, from the US Snow and Ice Data Centre, explains, the poles are like the Earth's refrigerators. "What we're doing by getting rid of that [Arctic] sea ice is radically changing the nature of that refrigerator," he says.
"We're making it much less efficient. But everything is connected, so what happens up there eventually influences what happens in other parts of the globe."
Since the intergovernmental panel delivered its findings, it had been widely accepted that the planet's warming is almost certainly due to human-induced climate change. The causes are principally the burning of fossil fuels, cement manufacture and land clearing, all of which release greenhouse gas emissions.
Despite the scientific warnings and the promises of politicians, these emissions are still growing at an unprecedented rate. The Arctic contains large amounts of carbon in the form of methane that until now has been locked in permafrost on the land and below the Arctic Ocean bed. Two studies last year found there could be double the amount of carbon in the permafrost as there is in the atmosphere.
Large areas of Alaska's permafrost are within just one or two degrees of thawing. If the Arctic keeps warming, the unfreezing of the permafrost and the release of carbon could rapidly increase the greenhouse gas in the atmosphere and in turn accelerate warming.
Dr Ted Scambos, of the Snow and Ice Data Centre, warns: "What will happen, I think, is that we'll get this whole new source of CO2 [carbon dioxide] and methane from the thawing permafrost that we won't easily be able to shut off, even if we get our act together."
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