Arctic sea ice is pulling a Benjamin Button. It's been getting younger. But while that's a fate some would relish, it's not necessarily good news for ice, as it's youthful appearance could speed its demise. The National Oceanic and Atmospheric Adminstration has released an animation showing the decline of old sea ice since 1987, the first year forMore
SAN FRANCISCO — The Arctic has just received its yearly checkup from a group of international scientists, and the patient isn’t looking well.
The region continues to be one of the fastest warming on the planet. From October 2014 to September 2015, it had the warmest average temperature on record going back to 1900, as the planet heads toward its warmest year on record. That accelerated warming has repercussions in the form of downward-spiraling sea ice coverage, melting of the massive Greenland Ice Sheet, and reduced summer snow cover.
All that change is having impacts on Arctic ecosystems and key species, and could lead to more shipping traffic and oil exploration in the region, as well as to impacts outside of the Arctic.
“The impacts of the persistent warming trend of over 30 years are clearly evident in land and ocean environments,” Kit Kovacs, a program leader of biodiversity research at the Norwegian Polar Institute and a co-author of the 2015 Arctic Report Card, said. She spoke here Tuesday during a presentation of the major findings of the report at the annual meeting of the American Geophysical Union.
Given the projections of further warming over the rest of the century, the world can expect to see “continued, widespread” change in the Arctic, Kovacs said.
The Arctic has been warming at more than twice the rate of the globe as a whole, with average temperatures today 5.4°F (3°C) above what they were at the beginning of the 20th century, compared to an estimated global average of 1.8°F (1°C) over the same time.
“We know this is due to climate change,” Rick Spinrad, chief scientist for the U.S. National Oceanic and Atmospheric Administration, said. The excess heat trapped in the atmosphere from accumulating greenhouse gases leads to changes in the Arctic that cause still more warming, a process called Arctic amplification.
Temperatures from October 2014 to September 2015 this year were 2.3°F (1.3°C) above average — the highest in an observational record going back to 1900.
That warmth influenced the extent of sea ice across the Arctic over the year: The maximum area that comes at the end of the cold winter months was the lowest on record this year, and it came 15 days earlier than average. At the opposite extreme, the end-of-summer minimum was the fourth lowest on record — the September minimum has declined at a rate of 13.4 percent per decade compared to the 1981-2010 average.
In particular, the older, thicker sea ice that is more resistant to melt in the summer months is making up a dwindling portion of the total. First-year ice, which is much more likely to melt in the summer, now accounts for about 70 percent of all sea ice, compared with about half that amount in the 1980s.
“These observations collectively confirm a trend toward a thinner and more vulnerable sea ice cover,” Jacqueline Richter-Menge with the U.S. Army Corps of Engineers’ Cold Regions Research and Engineering Laboratory and a co-author on the report card, said.
Sea ice isn’t the only thing melting. For the first time since the incredible ice sheet-wide melt event of 2012, the Greenland Ice Sheet saw significant melt across more than 50 percent of its surface. Melting of Greenland’s ice is a major concern because of its potential to substantially raise global sea levels.
The melt season was 30 to 40 days longer than average in the western and northern portions of Greenland, while its southern reaches saw an average to below-average melt season length, in a reversal from recent years. The flip was due to an unusual and persistent jet stream configuration that brought clear skies, and so more melt-fueling sunlight, to the northern parts of the ice sheet, but sent cold, northerly air blowing over its southern half.
While Arctic-wide snow cover was above-average in April, it hit the second lowest area on record for June, pointing to continued early spring snowmelt.
New Surprises & Future Changes
All of these changes can have major impacts on Arctic ecosystems and species. The lack of sea ice has dramatically changed the habitats of walruses, which use sea ice for mating, giving birth, finding food and taking shelter from storms and predators. Large haul outs of walruses onto land have been observed in recent years, and have led to stampedes that have killed calves.
High air temperatures and melting sea ice are also causing the ocean to warm, which is attracting subarctic fish species, displacing Arctic ones, Kovacs said.
One perplexing trend that continued this year was the browning of Arctic tundra that has been occurring over recent years, after several years of greening. Scientists aren’t sure what is causing this switch or exactly what its ramifications might be.
These dramatic changes to the Arctic are expected continue and compound moving forward this century. Even with the recent international agreement to limit warming to a global average of 2°C (3.6°F), Arctic temperatures will warm much more than that. By mid-century, winters in the Arctic could warm by 4° to 5°C, with large sea ice-free areas, report co-author Jim Overland, of NOAA’s Pacific Marine Environmental Laboratory, said.
“We’re already in the adaptation mode,” he said.
But if greenhouse gas emissions are reduced enough, the change in the Arctic “will slow down and have a big effect in the second half of the century,” possibly even heralding the return of more extensive summer sea ice.
While the broad brush strokes of Arctic warming continue to be seen year after year, the report card is important because “almost every year we see new surprises on the rapidity of the types of changes we’re seeing,” Overland said.