If global warming has paused, someone forgot to tell the Arctic.
Annual average temperatures have continued to rise for the region as a whole throughout the recent slowdown in the pace of warming globally, according to a new analysis of conditions above 60 degrees north latitude.
Over the past five years, temperatures in the autumn and early winter have been warmer all across the Arctic than they were for the same period during the last 20 years of the 20th century, leading an international team of researchers producing the report to conclude that these Arctic-wide conditions "are an indication that the early 21st century temperature increase in the Arctic is due to global warming rather than natural variability."
The report, released Wednesday, is the eighth annual status check on climatic changes at the top of the world and the effects those changes are having on flora and fauna there.
The effort, supported by the National Oceanic and Atmospheric Administration (NOAA) and the Office of Naval Research, is an attempt to provide a year-to-year summary of conditions whose changes are affecting weather patterns at lower latitudes and are opening to commercial development an ocean that long has been isolated year round by a thick sheath of ice.
During the past 30 years, the region has grown warmer and greener. The long-term decline in the extent of summer sea ice is opening the Arctic Ocean to economic activities ranging from shipping and oil exploration to fishing, noted Craig McLean, acting assistant administrator for NOAA's Office of Oceanic and Atmospheric Research, during a briefing on the report conducted during the American Geophysical Union's fall meeting in San Francisco.
The opening of the Arctic Ocean as the climate has warmed also opens a long, remote stretch of US coastline that the Navy must protect and the Coast Guard must patrol as ship traffic across the top of the world increases.
During 2014, "we continue to see the impact of a persistent warming trend in the Arctic that began over 30 years ago," said Jackie Richter-Menge, a researcher at the US Army Corps of Engineers Cold Regions Research and Engineering Laboratory in Hanover, N.H. "We also continue to see the influence of significant year-to-year regional variations."
Overall, the Arctic has been warming twice as fast as the lower latitudes.
One manifestation of those variations: Temperatures for the January-to-March period varied widely by region. Although it was still cold, Svalbard Airport registered 8 degrees C (14 degrees F) above its 1981-to-2010 average for the period. In late January, Alaska posted temperatures as much as 10 degrees Celsius above normal. Meanwhile, eastern North America saw temperatures running some 5 degrees C below normal.
The region's sea ice thickened and became more extensive by winter's end, compared with the end of winter in 2013. But by the end of the melt season three months ago, the ice had retreated to the sixth-lowest extent since 1979, when satellites began to keep track of the ice on a regular basis.
As the ice retreats, it leaves more open water to absorb sunlight that the ocean can return to the atmosphere as heat as autumn and winter arrive. Indeed, sea-surface temperatures across the Arctic have been increasing, with the Chukchi Sea posting gains of nearly 1 degree F per decade. Here, too, regional differences appear. The Laptev Sea and the Bering Sea posted temperatures 7.2 degrees F above the 1981-2010 average, while the Barents Sea above Norway was close to its 1981-to-2010 average.
Researchers with NASA and the Cooperative Institute for Research in Environmental Sciences (CIRES) noted that during the past 15 years, the retreat of summer sea ice has led to a 5 percent increase in the amount of energy the Arctic Ocean has taken up.
Some researchers had suggested that warming over an increasingly exposed Arctic Ocean should have led to an increase in evaporation and hence increased cloudiness in the summer. As that happens, the clouds, instead of sea ice, could act as a break on warming and perhaps on sea-ice loss there by reflecting sunlight back into space
But after analyzing data on clouds, the solar radiation the Arctic Ocean absorbs, and sea ice, the data showed "no long-term trend in clouds during the summer," said Jennifer Kay, a scientist at CIRES who focuses on Arctic climate. This runs counter to conditions over the rest of the world's oceans, which are covered with clouds, she explained.
The amount of cloudiness over the ocean during the summer varies from one year to another as weather patterns vary. But "there is no long-term trend ... that would allow this masking of the surface," she said.
The warming ocean and more sunlight has increased plankton populations in the upper ocean, with blooms more likely to occur twice a year than in the past. Plankton sit at the bottom of the food chain that supports a variety of marine life. The largest increases in plankton this year occurred off the coast of Russia.
And while on land, tundra has been greening in general, given the longer growing season, tundra across Eurasia has been browning – a trend the new Arctic report attributes to generally cooling summertime temperatures there.
The report also includes an update on polar bears – numbers that are incomplete because two broad regions, in the Russian Arctic and along the eastern and northern coasts of Greenland, are hard for scientists to reach, according to Jeff York, senior director of conservation for Polar Bears International, based in Bozeman, Mont.
Reductions in summer sea ice between 1987 and 2011 cut the polar bear population in western Hudson's Bay by a third, from 1,200 animals to 800. Along the norther coast of Alaska and east into Canada, the population centered along the southern Beaufort Sea fell by 40 percent between 2001 and 2010 to around 900 bears. Since then the population appears to have stabilized. Several regions in northern Canada have seen populations that have remained stable, while one region hosts an increasing population of polar bears.
Meanwhile, the Greenland ice sheet has seen little change in mass between 2013 and 2014, said Martin Jeffries, an arctic specialist with the Office of Naval Research in Arlington, Va., even as it saw extensive surface melting.
Given the pace of change and projections that warming will continue, it's vital to maintain and expand the tools in the region needed to monitor the changes, scientists say.
"If we're to understand how this complex environmental system works, if we're going to improve predictions of what's likely to happen ... and identify appropriate responses to the changes, we really need to add to our Arctic observing capabilities," said Dr. Jeffries, the report's principal editor.