The report, sponsored by the US National Oceanic and Atmospheric Administration (NOAA), shows that in 2017 a warming trend in the Arctic continued, resulting in higher surface and water temperatures and melting sea ice.
Some 85 researchers from a dozen countries contributed to the Arctic Report Card
, now in its 12th year.
"While 2017 saw fewer records shattered than in 2016, the Arctic shows no sign of returning to the reliably frozen region it was decades ago. Arctic temperatures continue to increase at double the rate of the global temperature increase," a NOAA news release on the report said.
The report card indicates that this may be the "new normal" for the region.
Historical data show the current observed rate of sea ice decline and warming temperatures are higher than at any other time in at least the past 1,500 years and likely much longer.
"The rapid and dramatic changes we continue to see in the Arctic present major challenges and opportunities," said retired Navy Rear Adm. Timothy Gallaudet, the acting NOAA administrator.
"This year's Arctic Report Card is a powerful argument for why we need long-term sustained Arctic observations to support the decisions that we will need to make to improve the economic well-being for Arctic communities, national security, environmental health and food security."
Major findings in the report include:
- Warmer air temperature, with the average annual air temperature over land for the year ending September 2017 the second-warmest since 1900. It was 2.9 degrees Fahrenheit (1.6 Celsius) above the average for the period of 1981 to 2010.
- Declining sea ice, with this year's maximum winter sea ice area, measured each March, the lowest ever observed. Sea ice is also getting thinner each year, with young ice covering a wider area.
- Above-average ocean temperature, with sea surface temperatures in August 2017 in the Barents and Chukchi seas up to 4 degrees Celsius warmer than average.
- Increased Arctic ocean plankton blooms, as the retreat of sea ice allows sunlight to reach the ocean and encourages more marine plant growth across the Arctic.
- A greener tundra, as plants get bigger and leafier, with shrubs and trees taking over grassland or tundra, satellite data shows. The biggest increases are occurring on the North Slope of Alaska, Canada's tundra and Siberia's Taimyr Peninsula.
According to the report card, there was greater snow cover in Asia in spring 2017 but less in North America, with the extent of snow cover in the North American Arctic below average for the 11th year of the past 12. It was the first time that the Eurasian part of the Arctic had above-average snow cover since 2005.
Scientists recorded below-average melting on Greenland's ice sheet
in 2017 compared to the previous nine years, after an early melt slowed during a cooler summer.
However, the ice sheet -- a major contributor to a rise in global sea levels -- continued to lose mass in 2017, as it has since measurements began in 2002.
The unprecedented rate of change in the Arctic is disproportionately affecting the people of northern communities, the report said, "further pressing the need to prepare for and adapt to the new Arctic."
'Extraordinary' Arctic changes
Jeremy Mathis, director of the Arctic Research Program for NOAA, told CNN in October that he had witnessed an "extraordinary transition" in the Arctic environment since 2003, during which time he has made 14 trips to the region.
"When I started going to the Arctic in 2003, it was very different environment that it is today," he said. "Back in 2003, we were breaking ice everywhere we went, from pretty much starting in the Bering Strait moving all the way up into the study areas north of Alaska and into the central Arctic basin. There was ice that was very thick and it was very extensive.
"This year in 2017, during a 25-day cruise in the Arctic, we didn't see a single piece of ice. We were sailing around on a coast guard icebreaker in blue water that could have been anywhere in the world. And it certainly didn't look like the Arctic."
The Arctic environment has changed from one that was dominated by sea ice "to one that is now largely ice-free during the summer months," Mathis said. "And that transition in ice cover has had real impact on everything from fishers to polar bears because everything in the ecosystem is really built around that ice coverage."
The fact that the Arctic is warming twice as fast as the rest of the planet is down to a phenomenon known as Arctic amplification, Mathis said.
Put simply, the Arctic is changing from a highly reflective surface to a very dark surface, he said. This means that sunlight entering the atmosphere that would normally be reflected back into space by sea ice or snow and glaciers is instead being absorbed by dark surfaces like the ocean, land and rock.
"The Arctic acts like a refrigerator for the entire Earth," said Mathis. "So, it doesn't matter where you live. You are going to feel the impacts of Arctic change."