The accelerating pace of climate warming in the earth’s polar regions is spurring a new sense of scientific urgency. This past February 28 a camera onboard the NASA satellite Aqua caught a Manhattan-size floating piece of ice shelf in the act of disintegrating. Slabs continued to calve and break up throughout the next 10 days; by March 8 the Wilkins ice shelf, comprising some 5,000 square miles of floating ice off the coast of the Antarctic Peninsula, had lost 160 square miles of ice to the Pacific Ocean.
\The breakup is the latest of seven major Antarctic ice-shelf collapses in the past 30 years, after some 400 years of relative stability. They include the detachment of a 1,300-square-mile chunk from the Larsen B ice shelf, the disintegration of giant ice shelves in the Prince Gustav Channel and the Larsen Inlet, and the disappearance of ice shelves known as Jones, Larsen A, Muller and Wordie. All of them corroborate temperature measurements showing that the western Antarctic Peninsula—now known to insiders as the Banana Belt—is warming up faster than anyplace else on earth.
The Wilkins event—serendipitously caught on video by a team from the British Antarctic Survey just days after it was discovered—has rallied scientists around the world. “You have closer communication than ever among the global science community now,” says Robin E. Bell, a polar research scientist at the Lamont-Doherty Earth Observatory of Columbia University. “We’re more sensitive that change is really happening quickly.” Relatively warm air seems to be the main culprit. As ice melts in the austral summer, pools of water fill the cracks that inevitably develop in any floating ice shelf as a result of bending and squeezing by the surrounding ocean. In a colder climate those fractures would be nothing more than shallow surface scars. But liquid water in the cracks can drill like a hot knife to the base of an ice shelf, snapping it in two.
The breakup and melting of floating ice has no direct effect on global sea levels. But an ice shelf is thought to act as a “cork in the bottle,” damming the flow of the land-based glacier that slowly feeds the shelf in the sea. When such a “cork” is removed, the glacier lurches forward. “Within a few months” of a breakup, explains glaciologist Ted Scambos of the National Snow and Ice Data Center at the University of Colorado at Boulder, the glacier “accelerates significantly, and within a year or two, it can be moving [toward the ocean] up to four times as fast as it moved when the ice shelf was intact.” As Bell puts it, the result is that “more ice cubes get into the ocean,” which does raise sea level.
In the near term, however, the biggest concerns are the changes in the north: the declines of Arctic sea ice and the Greenland ice sheet. Warm air and surface water are melting the summer polar ice cap. The shrinking sea ice drives a classic positive feedback loop: as more ice melts, fewer patches of white snow reflect solar energy, and larger regions of dark, sunlight-absorbing seawater open up—both causing the ice to melt even faster. That runaway effect, Scambos says, could quickly lead to a warmer climate along the Arctic perimeter and to the loss of Arctic permafrost.
In Greenland the story of not so glacial changes in the outlet glaciers is much the same. Their seaward edges are speeding up, and the ice sheet behind them is thinning. Measurements of local gravitational anomalies by the GRACE satellites show that the Greenland ice sheet, particularly in its southern reaches, is rapidly losing mass. “The ice sheet is on a diet,” Bell says. A lot of Greenland ice is slipping into the Atlantic Ocean.
Do all those effects add up to a tipping point? No one really knows. Investigators are anxiously seeking the answers to two great unknowns about the changes in polar ice. How fast will the ice sheets continue to slide into the sea, and how much more warming will it take to melt the Arctic permafrost? If the permafrost melts, prodigious amounts of trapped methane gas will burp out of the once frozen ground. Twenty years after such a release, methane is 72 times more potent than carbon dioxide (CO2) as a greenhouse gas (after 100 years it remains 25 times more potent than CO2), so if the methane is released, the planet risks a runaway climate catastrophe.
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Add CommentIndeed, there is a new sense of urgency. The NASA satellites watch on polar ice shelf is an unsurpassed evidence of global warming.
Reply | Report Abuse | Link to thisThis serves as a strong reminder to everyone (be they skeptics) that the climate change is already here and accelerating. Never mind whatever cause one may attribute to, be it the green house effect, the extraordinary sun spots activity or the phenomenal cycle of nature, the earth is obviously getting warmer. For those fence sitters, it is time to be jolted out of unnecessary complacency.
Everyone ought to contribute to the effort (no matter how minute) of decelerating the climate change. Do we really want our childrens children and their children to face the catastrophic consequences?
If this is
Reply | Report Abuse | Link to thisIf this is the "unsurpassed evidence" of global warming the evidence is poor indeed.
Reply | Report Abuse | Link to thisDoomsday speculations are not science. I am waiting for the next Ice Age.
--------------------- Bjorn Palmen is a nuclear engineer in Helsingfors, Finland
In the print edition I find it interesting and amusing that the ad on the facing page is from energytomorrow.org - an organization whose policies are environmentally destructive and accelerate the global warming catastrophe. (As an aside I have to wonder why SciAm accepted ad dollars from such an entity.)
Reply | Report Abuse | Link to thisBjorn, being a nuclear engineer, explains your blindness to global warming. You are, as we say in the US, a major putz.
Reply | Report Abuse | Link to thisActually global warming works FOR more nuclear power, as it will reduce the amount of fossil fuel being burned. Thus it would give me no sneaky advantage as a nuclear engineer to point out that the evidence for global warming is still lacking.
Reply | Report Abuse | Link to thisSo the "ultimatexpert" got it wrong. But he is wrong about the warming too. Some people just cannot think.
While the topic is how scary it is when a crumb of ice breaks off the Wilkens ice shelf, Antarctic ice also set a record (since 1979) for extent of sea ice at the end of last winter. But of course, all climate related phenomena are strong indicators of climate change (formerly known as global warming).
Reply | Report Abuse | Link to thisI recently read the following article in the Washington Post: "The Arctic ocean is warming up, icebergs are growing scarcer and in some places the seals are finding the water too hot, according to a report to the Commerce Department yesterday from Consul Ifft, at Bergen, Norway. Reports from fishermen, seal hunters and explorers, he declared, all point to a radical change in climate conditions and hitherto unheard-of temperatures in the Arctic zone. Exploration expeditions report that scarcely any ice has been met with as far north as 81 degrees 29 minutes. Soundings to a depth of 3,100 meters showed the gulf stream still very warm. Great masses of ice have been replaced by moraines of earth and stones, the report continued, while at many points well known glaciers have entirely disappeared. Very few seals and no white fish are found in the eastern Arctic, while vast shoals of herring and smelts, which have never before ventured so far north, are being encountered in the old seal fishing grounds." Incidentally, the article was published in the November 2, 1922 issue of said newspaper. "Deja vu all over again"?
NASA satellites have only been giving this bird's eye view of the polar regions since 1979, a mere blink of the eye in the time scale required to show unnatural climate change. Sorry believers, you are pathetically unconvincing.
I'm not a scientist, but would the harvesting of energy produced by the ultimate release of methane gas from the burning off of the permafrost be actually beneficial? Allow commerical access to this resource. Maybe they can divert the gas into energy, saving the planet while they convert, store and distribute the energy.
Reply | Report Abuse | Link to thisi'm doing a study for science on the water levels and on how the polar icecaps are changing and melting. some books are saying there not changing the water levels and some are saying they are. one book said it doesn't and had a STUPID idea of a bowl of water and having 10 ice cubes to measure the water put in the ice, let it melt then remeasure it. thats stupid because thinking the worlds water is the bowl theres more then 10 icebergs that are going to melt. so which is it? true or false? do the melting polar icecaps really change the water levels? i think it would have to ecause it could give an imbalence of fresh water and salt. please correct if wrong.
Reply | Report Abuse | Link to thisnever mind i have got it now its not the melting ice its the ice breaking which everytime it does it adds a little but to the levels...
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