From crumbling permafrost shorelines and dwindling sea ice to unprecedented blooms of ocean plankton, the Arctic region continued its profound transformation to a warmer, less frozen and biologically changed region, a team of international scientists said today, in releasing the 2020 Arctic Report Card.
The annual report, compiled by 133 scientists from 15 countries, found that the average annual Arctic air temperature in 2020 was the second-highest since record-keeping started in 1900. In nine of the last 10 years, the average temperature was at least 2.2 degrees Fahrenheit above the 1981 to 2010 mean, and more than 4 degrees warmer than the 1900 to 2019 mean. Arctic temperatures for the last six years have all exceeded previous records.
For University of Alaska Fairbanks climate scientist Rick Thoman, one of the report’s three lead authors, the prolonged extreme heat over Northern Siberia last spring and summer was one of the standout events in a year of Arctic extremes. The sustained heat triggered a cascade of impacts, with early sea ice loss and early snowmelt, which “set the stage for a big wildfire season,” Thoman said.
The report also highlighted dramatic biological changes in the Arctic, “from increased plankton blooms to fish species moving large distances, to orcas preying on bowhead whales in areas the bowheads were previously safe,” Thoman said. On land, the biggest changes include more plants growing across the tundra and changes in animal distributions, including moose and beaver moving into Alaska’s North Slope, he added.
As to any surprises that might be ahead, he said, “From my expertise, which does not include things like methane ‘explosions’ from the floor of the ocean, the most obvious ‘unexpected’ things to happen would be weather-scale events that produce cascading impacts.”
One example could be a storm that results in large-scale sea ice loss early in the season exposing the ocean to intense sunlight and setting off changes “that could reverberate through the Arctic system through the following autumn and beyond,” Thoman said.
The possibility of catastrophic glacier or ice sheet loss also looms, as does the disruption of freshwater sources for Arctic communities through erosion or storms, he added.
A series of recent studies have also linked the amplified Arctic warming to extreme weather in the mid-latitudes of the Northern Hemisphere, including simultaneous droughts in important agricultural areas, extreme cold outbreaks in the Northeast and flooding rains in the United Kingdom.
The first Arctic Report Card was released in 2006, when scientists started documenting rapid changes to the Greenland ice sheet first evident in the acceleration of glaciers flowing to the sea. Now they know that the ice sheet is melting four times faster than at the turn of the century, raising sea level around the world by nearly 0.3 to 0.6 inches every 10 years, adding up to between 5 and 13 inches by 2100.
“Sadly, even ‘good’ news about Greenland these days is grim,” said Twila Moon, an Arctic researcher with the National Snow and Ice Data Center. “While it might be tempting to take a sigh of relief that it wasn’t another record year, last year’s ice loss is still terrible news,” Moon said.
She added, “The Greenland ice sheet has now lost ice every year since 1998, a devastating pattern that is exacerbating woes on shorelines all around the globe.”
Especially worrisome is that this year’s ice loss happened even though parts of the surface were protected by reflective snow, she said. “Because of the way that Greenland responds to our warming climate, continued ice loss and sea level rise is certain,” she added.
The meltwater that comes from Greenland reaches North American coastlines, said Marco Tedesco, a co-author of the report card and a climate researcher at Columbia University’s Earth Institute and NASA.
“This has huge implications for many aspects of our lives,” Tedesco said. “For example, a change in temperature of the Atlantic water nearby the East Coast of the U.S. could impact lobster behavior, with great implications for fisheries.”
Tedesco said research on Greenland is key to understanding future sea level rise, and if he had to pick the most important factor, he would think about how changes in winds and air currents over the Arctic are hastening its warming.
The researchers also reported that parts of the Arctic Ocean seethed with an unusually high level of biological activity. According to the report, plankton in the Laptev Sea bloomed at twice the average rate in July, and in August, went off the charts, at six times the average rate.
The 2020 plankton boom was part of a long-term sustained increase in the Arctic, said Karen Frey, a geographer at Clark University in Massachusetts who studies the biological and biogeochemical impacts of sea ice decline in polar shelf environments
“Primary productivity in the world’s oceans accounts for about half of all photosynthesis on the planet and is one of the main ways that carbon dioxide is pulled out of the atmosphere and into the oceans,” she said.
Howard Epstein, head of environmental studies at the University of Virginia, tracked changes in Arctic vegetation for the report card, and said that this year’s edition highlights variability, geographically and in time. Greenery has increased in some parts of the Arctic but declined in others.
“From a vegetation perspective, the surprise for me is the changing dynamics,” he said. From about 1990 to 2010, the Arctic greened steadily, but since then, it has “been flat or decreasing,” he added.
The trends are important because increased vegetation would take more carbon out of the air and lock it into soils or woody plant matter. Vegetation changes can also affect how fast permafrost thaws and releases greenhouse gases, and has a direct climate effect because it changes the reflectivity of the surface. An expansion of tundra shrubs warms the climate, he added.
Co-author James Overland, a senior researcher with the National Oceanic and Atmospheric Administration, said the Siberian heat wave was “the big event beyond previous experience for this year.”
The impacts were large, he said, with forest fires, irreversible permafrost melt and delayed regional sea ice growth.
Feedbacks in the climate and ecosystem are accelerating faster than was thought,” Overland said. “Less sea ice traps more heat that allows more ice to melt.”
Tedesco said the report card reinforces concerns about how the Arctic meltdown will affect global sea level.
“I think that the acceleration of the melting and the potential reverberations of the waking up of the Antarctic ice sheet are the two most important scientific facts that have been consolidating within the scientific community,” he said.
“We know the acceleration is occurring,” he said. “We also know that, in the past, when similar conditions were present in terms of CO2 and temperatures, the Greenland ice sheet was contributing to sea level rise more than today.”
Greenland probably “woke up” and started melting after Antarctica, because of changes in global ocean circulation, he said.
“Now, Antarctica is waking up and we are witnessing a one-time experiment that will likely bring an acceleration of sea level rise stronger than anticipated over the past decade or five years.”
An earlier version of this story incorrectly stated the amount that the melting of the Greenland ice sheet is raising sea level around the world. It is raising the level by nearly 0.3 to 0.6 inches every 10 years.