SAN FRANCISCO, CALIFORNIA—Just last spring, 2012 appeared on track to be a relatively unremarkable year in the Arctic. Throughout the year, in fact, surface air temperatures—which largely drive melting—seemed unexceptional. But, as scientists including National Oceanic and Atmospheric Administration (NOAA) Administrator Jane Lubchenco said today at a press conference at the American Geophysical Union's fall meeting, record-setting melting happened anyway: record snow melt, record sea ice minimum, melting even at the top of the Greenland ice sheet (in what was once called the "dry snow zone"), and widespread warming of permafrost.
The researchers announced the release of the 2012 Arctic Report Card, an annual description of the state of the Arctic that is sponsored by NOAA's Arctic Research Program, part of its Climate Program Office. NOAA published the first Arctic Report Card in 2006. Nearly 150 scientists from 15 countries contributed to this year's report, which looked not only at the melting events, but also examined changes to the growing season, weather events, and ecosystem-wide impacts from phytoplankton blooms to the loss of Arctic megafauna.
The widespread melting across the Greenland ice sheet was one of the most dramatic changes, said Jason Box of the Byrd Polar Research Center at Ohio State University in Columbus. "I've studied Greenland for 20 years—devoted my career to it," he said at the press conference. "And 2012 was an astonishing year." Box pointed to nearly ice-sheet-wide melting on Greenland, with extensive surface melting documented for first time at the highest elevations of ice sheet, and the longest melt season since satellite observations began in 1979.
The changing Arctic, the report notes, is also having wide-ranging impacts on the Arctic ecosystem. For example, the thinning ice is driving melt ponds in the Arctic and promoting phytoplankton blooms under the ice; the warming is also altering population dynamics among lemmings, with, in some locations, dire effects on their predators, such as the Arctic fox.
The combined effect of changes in sea ice, glaciers, and the Greenland ice sheet is also conspiring to reduce the overall reflectivity of the Arctic in the summer, when the sun is ever-present, said Martin Jeffries, NOAA program officer and Arctic science advisor at the Office of Naval Research, and one of the three editors of the report card. Thinner ice means a darker surface, which increases the region's capacity to store heat and thus enables more melting. That, Jeffries said, explains why the Arctic continues to grow warmer twice as fast as the lower latitudes of the planet. This "Arctic amplification" of global warming was predicted 30 years ago, he said, and "we're now seeing [it] happening in a significant way."