Arctic temperatures are continuing to rise while sea ice declines, a new report has found, with the region showing no sign of returning to its "reliably frozen" state.
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."