For decades, climatologists have watched the steady shrinking of Arctic sea ice. But what they saw last summer wasn't steady; it was catastrophic.
In July, scientists discovered that all but 3 percent of Greenland's massive ice sheet had thawed at the surface. That was nearly double the usual summer melt, with much of it happening over the space of just four days.
Sea ice followed suit: On September 16, the point of maximum melt, there was more open water in the Arctic than had ever been recorded. The amount surpassed the previous record by 18 percent, or an area the size of Texas.
Every summer for the past ten years has seen far less ice than the 1979-2000 average, leaving the remaining ice thinner and less resilient. But 2012's massive, record-shattering melt is a particularly ominous sign of things to come, says Michael E. Mann, director of the Earth System Science Center at Pennsylvania State. The last record melt, in 2007, Mann says, "was outside the range of what climate models predicted," and some climatologists regarded it as a fluke. "The 2012 melt caused [climate] modelers to step back and say, 'Maybe nature really is proceeding much faster than our models predicted.'"
The pace may get faster yet, given the triggering of "feedback loops." Ice reflects heat, and dark, ice-free water absorbs it. Melting permafrost is emitting the powerful greenhouse gas methane, also at a faster rate than scientists initially predicted. Oil companies are rushing to take advantage of the ice-free waters for new drilling, which will further feed carbon emissions.
Because changes in the Arctic affect the jet stream, they can have major impacts on weather far away: Scientists are drawing connections to the slow-moving, persistent storms of recent winters and to last summer's extreme drought and wildfires. "There's a tendency to overemphasize the melting Arctic environment and polar bears at the expense of talking about impacts that are every bit as real, right where we live," Mann says. "This melting should be seen as something much larger: as truly fundamental change to our planet."
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