SAN FRANCISCO – After decades of rising temperatures, Arctic conditions have reached new heights again this year, the latest assessments show, signaling dramatic changes for the Arctic and its inhabitants under relentless global warming. Walrus populations in the Pacific Arctic have plunged as dwindling sea ice forces them to haul out onto land in crushing crowds, and the Arctic’s small native fish may stand little chance against large competitors moving northward as polar waters warm up.
These and other threats to Arctic biodiversity and resources were detailed in the 2015 Arctic Report Card, released Tuesday at the American Geophysical Union Fall Meeting in San Francisco. The report is a peer-reviewed, multinational research collaboration involving 72 researchers from 11 countries that has been produced by the U.S. National Oceanic and Atmospheric Administration (NOAA) annually since 2006.
“The impacts of the persistent warming trend over 30 years are clearly evident,” said Kit Kovacs, a biodiversity researcher at the Norwegian Polar Institute.
A number of new climate records were set this year. Winter air temperatures over Arctic lands were the warmest since measurements began in 1900. Between October 2014 and September 2015, temperatures were 1.3C (2.3F) above average, amounting to a 3C (5.4F) gain since the beginning of the 20th century, primarily due to human-driven climate change.
The Arctic Ocean’s sea ice also reached new lows this year. Winter ice began receding more than two weeks earlier than usual, and coverage was the most scant since record keeping began in 1979. The 2015 summer ice shrank to the fourth lowest area on record. These new numbers indicate that summer sea ice is now dwindling at more than 13 percent a decade. Furthermore, 70 percent of the March ice pack contained thin, fragile first-year ice, jeopardizing Arctic mammals that hunt, shelter and bear their young on the frozen seas.
The changing environment has created problems for Pacific walruses. Their population has dropped by more than 50 percent over the past decade. Vanishing ice is at least partly to blame. In recent years, “thousands upon thousands” of these huge animals hauled out onto shore because there was no ice for them to rest on after swimming hundreds of miles to feed, scientists said. The crowded quarters are sparking food shortages and young calves often get crushed in the resulting stampedes.
“The land herds that we’re seeing in the North Pacific have not been seen before in the numbers in which they’re occurring,” said Kovacs, one of the report’s co-authors. “Not in the lifetime of living people have these things happened. And they’re happening now.”
Arctic fish don’t seem to be coping well with warming waters either, the report card finds. Cod and other large fish from the south are migrating into polar waters. In the northern Barents Sea, the cod population is near a record high and haddock are also becoming abundant, while local cold-loving fish have been pushed out of the area.
That may be good news for Arctic fisheries. But these incoming predators pose yet another threat to native fish that are already stressed by warming waters. Local species, such as the gelatinous snailfish and the twohorn sculpin, are small, tend to remain in one area and have specialized diets – all of which limit their ability to adapt to climate change. The snailfish, unable to compete for food and preyed on by their new neighbors, could die out in the northern Barents Sea.
Arctic ecosystems will be further damaged by contaminants, acidifying waters and habitat loss as waning sea ice opens the region to activities such as shipping, mining and oil drilling, the report points out. Invasive species that catch a ride in the ballast water of cargo ships will likely pose another new risk to the Arctic ecosystem.
The report card doesn’t examine the changing climate’s consequences for people in the Arctic. “But as you can imagine there are going to be impacts,” said Martin Jeffries, Arctic science advisor with the U.S. Office of Naval Research, and lead author on this year’s report. “With the retreat of the ice cover, and we’re seeing so much more open water than we used to, there’s talk of transpolar shipping, resource extraction,” he said. “Some people are looking at the changes in the sea ice as an opportunity for economic development.”
Henry Huntington, who leads the scientific work of the Pew Charitable Trusts Arctic projects and is not affiliated with the report card, said the findings tally with his studies that enlist Inuit hunters to provide information on Arctic changes. He said the hunters tell him that if you change the sea ice, the animals will change. “The hunting opportunities for some animals are less because the sea ice isn’t around as long, it breaks up very quickly and recedes very fast. And if you’re trying to hunt on floating pack ice, your window of opportunity is a lot less,” said Huntington.
Overall, the warming amounts to a transition from normal Arctic summers to conditions more closely resembling the subarctic ecosystem, Huntington said. Mean summer sea surface temperatures in the Chukchi, Barents and Kara seas and the waters off the west coast of Greenland registered about 7C–8C (44F–46F) in 2015 – as much as 4C (7.2F) warmer than the 1980–2010 average, the report card showed. Waters northwest of Alaska and off western Greenland are warming fastest – gaining about 0.5C (0.9F) per decade since 1982.
Because the effects of climate change are amplified at the poles, Arctic winter temperatures will rise by at least another 4–5C (7.2F–9F) by mid-century, even if the world sticks to the 2C (3.6F) limit set at the United Nations climate summit in Paris earlier this month. “The Arctic is warming twice as fast as other parts of the planet, which has ramifications for global security, climate, commerce and trade,” said NOAA chief scientist Rick Spinrad.
But this year’s report card still gives room for hope. If greenhouse gases are sufficiently curtailed soon, “that will have a big impact in the second half of the century,” said NOAA Arctic scientist Jim Overland. “The next generation may see an ice-free summer, but hopefully their descendants will see a return of more sea ice.”
Top image: Thousands of walruses hauled out on a barrier island offshore of northern Alaska in September 2014. (NOAA NMFS/Corey Accardo)