NOAA released the annual Arctic Report Card in December, revealing that the climate was slightly cooler than the previous year—but that long-term climate warming and changes in the environment persist.
The Arctic Report Card aggregates trends in the atmosphere, sea ice and ocean, marine ecosystems, terrestrial ecosystems and the terrestrial cryosphere (i.e., ice on land). Scientists found cooler temperatures in the summer of 2013 across the central Arctic Ocean, Greenland and northern Canada, which moderated the record sea ice loss and extensive melting that the surface of the Greenland ice sheet experienced last year. But regional extremes continued, including record low May snow cover in Eurasia and record high summer temperatures in Alaska.
“The Arctic caught a bit of a break in 2013 from the recent string of record-breaking warmth and ice melt of the last decade,” said David M. Kennedy, NOAA’s deputy under secretary for operations, during a press briefing today at the American Geophysical Union annual meeting in San Francisco. “But the relatively cool year in some parts of the Arctic does little to offset the long-term trend of the last 30 years: the Arctic is warming rapidly, becoming greener and experiencing a variety of changes, affecting people, the physical environment, and marine and land ecosystems.”
A few highlights (or lowlights, so to speak) from the report:
Air temperatures: While Eurasia had spring air temperatures as much as 7°F above normal, central Alaska experienced its coldest April since 1924 with birch and aspen trees budding the latest (May 26) since observations began in 1972. Summer across a broad swath of the Arctic was cooler than the previous six summers, when there had been pronounced retreat of sea ice. But Fairbanks, just below the Arctic Circle in Alaska, experienced a record 36 days with temperatures at or exceeding 80°F.
Snow cover: The snow extent in May and June across the Northern Hemisphere (when snow is mainly located over the Arctic) was below average in 2013. The North American snow cover during this period was the fourth lowest on record. A new record low was reached in May over Eurasia.
Sea ice: Despite a relatively cool summer over the Arctic Ocean, the extent of sea ice in September 2013 was the sixth lowest since observations began in 1979. The seven lowest recorded sea ice extents have occurred in the last seven years.
Ocean temperature and salinity: Sea surface temperatures in August were as much as 7°F higher than the long-term average of 1982-2006 in the Barents and Kara Seas north of Siberia, which can be attributed to an early retreat of sea ice cover and increased solar heating. Twenty-five percent more heat and freshwater is stored in the Beaufort Gyre, a clockwise ocean current circulating north of Alaska and Canada, since the 1970s.
Greenland ice sheet: During a summer when air temperatures were near the long-term average, melting occurred across as much as 44 percent of the surface of the Greenland ice sheet, close to the long-term average but much smaller than the record 97 percent in 2012.
Vegetation: The Arctic is greening as vegetation responds to warmer conditions and a longer growing season. Since observations began in 1982, Arctic-wide tundra vegetation productivity (greenness) has increased, with the growing season length increasing by 9 days each decade.
Wildlife: Large land mammal populations continued trends seen over the last several decades. Musk ox numbers have increased since the 1970s, in part due to conservation and introduction efforts, while caribou and reindeer herds continue to have unusually low numbers.
Marine fishes: The long-term warming trend, including the loss of sea ice and warming of waters, is believed to be contributing to the northward migration into the Arctic of some fish such as Atlantic mackerel, Atlantic cod, capelin, eelpout, sculpin and salmonids.
Black carbon: While black carbon (soot) originating from outside the Arctic has decreased by 55 percent since the early 1990s, primarily due to economic collapse in the former Soviet Union, increasing numbers of wildfires fueled by greater amounts of vegetation in a warmer, drier climate, have the potential to increase atmospheric black carbon in the high latitudes.
Speaking of sea ice cover, “There was more sea ice at the end of summer 2013 than there was at the end of the record-breaking summer of 2012. But, the 2013 minimum ice extent was still 18 percent below the average minimum, and ranked as the 6th smallest ice extent since satellite observations began in 1979,” reported Don Perovich, a research geophysicist at Dartmouth College specializing in Arctic climate changes. “Moreover, the past seven years have had the seven smallest ice extents in the observational record. There is also a continuing shift from older, thicker ice to younger, thinner ice. In March 2013, only 25 percent of the ice cover was more than one year old. The remaining old ice was mainly found in the Western Arctic, adjacent to northernmost Greenland and the Canadian Arctic Archipelago. In summary, I’d say that 2013 was another year in the new normal of reduced Arctic sea ice.”