|
Report: More Arctic warming, ice melting as temperatures rise
In many ways the canaries in the mine when it comes to global warming, features such as the sea ice extent in the Arctic region provide dramatic evidence of rising temperatures, according to the Arctic Report Card 2015, published by the National Oceanic and Atmospheric Administration.
“Now in its 10th year, the Arctic Report Card is a key tool to understanding changes in the Arctic and how those changes may affect communities, businesses and people around the world,” said NOAA Chief Scientist Dr. Rick Spinrad, when announcing publication of the report during a Dec. 15 press conference. “The Arctic is warming twice as fast as other parts of the planet, which has ramifications for global security, climate, commerce and trade.”
Production of the peer-reviewed report involved about 70 authors from 11 countries, including contributors from U.S. federal agencies and academics, with guidance from the U.S. Army Corps of Engineers Cold Regions Research and Engineering Laboratory and from NOAA, NOAA says.
Rising air temperatures Particularly notable were findings for Arctic air temperatures. The average annual temperature over land between October 2014 and September 2015 turned out to be 1.3 C above the long-term average, the highest level since observations began in 1900 and a 3 C increase since the beginning of the 20th century, the report card says.
Surface sea temperatures, measured in August during the Arctic open water season, show some variability, with three regions demonstrating temperature increases. The East Baffin Bay region, between northern Canada and Greenland, showed an average temperature rise of 0.5 C per decade since 1982, with an acceleration to 1 C per decade in the past two decades. Surface temperatures in the Chukchi Sea region have also shown an average rise of 0.5 C per decade. The average per decade temperature rise in the Kara Sea has been 0.3 C, with the August 2015 sea surface temperature in this region being 4 C higher than the 1982 to 2010 average, the report card says.
Shrinking ice As temperatures have risen, the Arctic sea ice cover has shrunk. The maximum sea ice extent for 2015, recorded on Feb. 25, proved to be the lowest since records began in 1979. The minimum sea ice extent, recorded at the end of the summer melt season, has been declining at an average rate of 13.4 percent per decade, with the Sept. 15, 2015, minimum extent being the fourth lowest since records began. Moreover, 70 percent of the March 2015 sea-ice cover consisted of relatively thin first-year ice, rather than thicker and more durable multi-year ice, the report card says.
On-land ice in the Greenland ice sheet is showing significant evidence of surface melting over more than 50 percent of its area. Although in 2015 the summer melt season lasted 30 to 40 days longer than on average in western, northwestern and northeastern Greenland, the season length was at or below average elsewhere. And, with 22 of 45 of the largest ocean-terminated glaciers retreating while nine relatively wide glaciers advanced, the annual ice loss was a relatively low 6.4 square miles, the report card says.
While the Arctic-wide terrestrial snow cover in April turned out to be above average, by June the snow cover had shrunk to the lowest level since records began in 1967 in both the North American and Eurasian sectors of the Arctic. The Arctic-wide snow extent has declined by 18 percent per decade since 1979, the report card says.
And, probably as a consequence of rising precipitation, the measured rate of discharge of freshwater into the Arctic Ocean from eight Eurasian and North American rivers was 10 percent greater in 2014 and the first seven months of 2015 than in the decade 1980 to 1989.
Ecosystem impacts Rising temperatures coupled with shrinking ice and snow are having a noticeable impact on Arctic ecosystems. Increasing levels of sunlight in the upper layers of the ocean are promoting photosynthesis and hence led in 2015 to widespread and exceptional phytoplankton blooms at various locations along the edge of the continental shelf. And the greenness of Arctic vegetation has been increasing over the past two to three decades, although with some decline in greenness in the past two to three years. Greenness provides a measure of the density of live vegetation.
There have also been some well publicized impacts on Arctic wildlife. Walrus, traditional users of sea ice as a platform for mating, giving birth, finding food, sheltering from storms and evading predators, have been observed congregating in large numbers on the seashore in northwest Alaska in recent years. Overcrowding in coastal haul-outs has led to stampedes, and walrus must now travel longer distances to the ice edge to forage for food, the report card says.
And scientists from Norway and Russia have detected the northward movement of subarctic fish species such as cod and long rough dap into the Arctic waters of the Barents Sea. These predator fish may pose a threat to smaller Arctic fish species, the report card says.
- ALAN BAILEY
|
