If you want to witness climate change, just head north and keep going until you run out of globe. Of course, that's easier said than done; the Arctic is a forbidding, isolated area, short of people and encased in ice much of the year. But those who make their way to places like Barrow, Ala. the northernmost point of the U.S. or the icy seas of the Arctic Ocean will witness a part of the planet that is warming and changing faster than anywhere else. While the world as a whole warmed by about 1°F (.55°C) over the entire 20th century, parts of the Arctic have warmed by 4° to 5°F (2.2° to 2.7°C) just since 1950. The physical changes from global warming are visible in the Arctic almost in real time and they are a warning for those of us who live in more comfortable latitudes. As the polar expert Walt Meier of the National Snow and Ice Data Center (NSIDC) has put it: "What happens in the Arctic doesn't stay in the Arctic."
That's bad news, since not only is the warming threat in the Arctic bad, it's almost certainly intensifying. Earlier this month scientists at the NSIDC announced that Arctic summer sea-ice extent had fallen to its second lowest level since at least 1979, and likely long before that. Just 1.67 million sq. mi. (4.32 million sq km) of the Arctic sea was covered by ice as of mid-September a little larger than the all-time record low of 1.608 million sq. mi. (4.16 million sq km) set in September 2007. And that may be a lowball figure: a separate group of researchers at the University of Bremen in Germany did their own estimate earlier this month and reported that there was even more melt in 2011 than in 2007.
The differences between the two estimates are academic; the larger point is that the current sea-ice extent is more than 1 million sq. mi. (2.5 million sq km) below the 19792000 average. That means the Arctic has lost an area greater than all the U.S. states east of the Mississippi. And what ice remains appears to be getting thinner and weaker as well. "There is plentiful data to suggest that the ice is thinning as well as shrinking in area," Nick Toberg and Till Wagner, polar-ocean physicists from Cambridge University, wrote to me recently in an e-mail from the Greenpeace ship Arctic Sunrise, where they were doing sea-ice fieldwork north of Norway. "It's a downward spiral because after successive seasons of thinner ice, each [year] gets worse than the one before it."
The question now is what's going to happen to the Arctic as we keep adding carbon emissions to the atmosphere and the climate keeps warming. Some scientists worry that Arctic sea ice may be going from a downward spiral to a "death spiral," one from which there is no escape even if we can manage to reduce carbon emissions. As more ice melts, more dark open water is exposed, which absorbs more heat, accelerating the melting. (White sea ice, by contrast, reflects sunlight, slowing warming.) Until recently, many scientists thought it might take until the end of the century for the North Pole to become completely ice-free during the summer. Now there are estimates that we could see a naked North Pole by 2030 or even earlier. "The melting is happening faster in the real world than it has in the models," says James Overland, an oceanographer for the National Oceanic and Atmospheric Administration.
That's why doing fieldwork on Arctic sea ice is so important. Models and satellite data can only take you so far. For full accuracy, someone actually has to go to the far north and measure. On their research trip, Toberg and Wagner went to the north Greenland Sea and measured sea-ice thickness at multiple sites using power drills, snow-depth measurements and GPS readings. "Drilling is still the most accurate, and only direct way, of measuring thickness of the ice," they wrote. "This involves simply poking a tape measure down a hole drilling in the ice to note both the total depth of the ice and the thickness of the freeboard [the ice above the water line]." The work is basic science at its best.
But it's not all that simple. Toberg and Wagner are also working with laser 3-D scanners that enable them to capture a high-resolution replica of an ice floe essentially allowing them to take the ice back to the lab, something that would otherwise be impossible without the help of a very large refrigerator. That data gives them a much deeper understanding of what's happening to Arctic ice, a big improvement over what you can get from satellites, which struggle to measure ice below the water level. (And as anyone who watched Titanic knows, that's where most of the ice hides.) "Snow cover, surface meltwater and the high variability in ice properties hide the full picture of what is happening with the ice under the sea," write Toberg and Wagner. "The information we gather can help verify satellite data and ultimately improve the accuracy of complex computer models."
The more on-the-ground information scientists can gather the better because ice, despite its seeming simplicity, is extremely complex. The rate of melting in the Arctic isn't just a function of temperature change; local weather conditions, snow cover and ocean currents can also influence ice loss. That's what makes it so difficult to predict exactly how rapidly we might see the Arctic go ice-free. Scientists at the National Center for Atmospheric Research even predicted in a recent study that Arctic sea-ice melt might pause or reverse over the next decade, depending on northern-wind patterns. But that would simply be a pause in the inexorable decline inexorable, that is, if we don't curb carbon emissions soon. At that point, Arctic ice becomes a memory, and we will find ourselves on a very different planet.