Scientists have long predicted that sea level rise will be one of the most disastrous consequences of global warming -- and now, they're discovering that the northernmost region, the biggest contributor to sea level rise, is warming at unprecedented rates.
Climate change is transforming the Arctic into a "dramatically different state," with the region warming at a rate more than twice as fast as the rest of the world due to the melting of white and sea ice, according to the 2021 Arctic Report Card released by the National Oceanic and Atmospheric Administration Tuesday morning.
The substantial decline in Arctic sea ice extent since 1979 is one of the most iconic indicators of climate change, according to the report. Summer 2021 saw the second-lowest amount of older, multi-year ice since 1985, and the post-winter sea ice volume in April 2021 was the lowest since records began in 2010.
In addition, the period between October and December in 2020 was the warmest Arctic autumn on record, dating back to 1900, according to the report.
The average surface air temperature over the Arctic in the past year, October 2020 through September 2021, was the seventh-warmest on record, and this is the eighth consecutive year since 2014 that air temperatures were at least 1 degree Celsius above the long-term average.
Recent studies on ocean acidification, the process in which the water's pH levels are lowered as a result of carbon dioxide in the atmosphere, show that the Arctic Ocean is acidifying faster than the global ocean, but with high spatial variability, the report states.
Since ocean water is typically neutral, the acidification could have implications on the ecosystem of the Arctic Ocean, including effects on algae, zooplankton and fish, according to the report.
In the Eurasian Arctic, terrestrial snow cover in June 2021 was the third-lowest since records began in 1967, the report states. In the North American Arctic, snow cover has been below average for 15 consecutive years.
Beavers are also colonizing the Arctic tundra of western Alaska, transforming lowland tundra ecosystems and degrading permafrost by increasing the amount of unfrozen water on the landscape during the winter, according to the report.
The number of beaver ponds in Alaska has doubled since 2000, likely due to the warming trend that has resulted in widespread greening in what was previously tundra, scientists and local observers have both noted, the report states.
The Greenland Ice Sheet, the largest contributor to sea level rise in the world, experienced three melt episodes in late July and August, according to the report. Satellite imagery provides "unequivocal evidence" of widespread tundra greening. A melt episode on a glacier can include melting, evaporation, erosion and calving in a short period of time.
Retreating glaciers and thawing permafrost are causing local to regional-scale hazards as well, the scientists wrote.
The Arctic Report Card documents how climate change continues to alter the once "reliably-froze" region as increasing heat and the loss of ice drive its transformation into an uncertain future, according to NOAA.
"This year's Arctic Report Card continues to show how the impacts of human-caused climate change are propelling the Arctic region into a dramatically different state than it was in just a few decades ago," said NOAA Administrator Rick Spinrad, Ph.D. "The trends are alarming and undeniable. We face a decisive moment. We must take action to confront the climate crisis."
ABC News' Dan Manzo contributed to this report.