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The shift to a not-so-frozen North is “ well underway ”, warn scientists

The Arctic continued its unshakeable transition to a new climate in 2020, as the effects of near-record warming increased across the region, reducing ice and snow cover and fueling extreme forest fires, said Scientists Tuesday.

“The story is clear: the transformation of the Arctic into a warmer, less frozen and biologically altered region is well underway,” the scientists said in an annual assessment of the region published at a conference of the ‘American Geophysical Union.

As the whole planet heats up from emissions gases trapping heat through the combustion of fossil fuels and other human activities, the Arctic is warming more than twice as fast as other regions. This warming has cascading effects further south in more temperate and densely populated regions. regions, sea level rise influencing ocean circulation and, more and more scientists suggest, playing a role in extreme weather conditions.

This year, the minimum extent of sea ice in the Arctic Ocean, reached at the end of the melt season in September, was the second lowest in the satellite record, according to the assessment. On land, Greenland’s immense ice cap and glaciers in Alaska and elsewhere have lost mass at above-average rates, although the rate in Greenland has slowed from last year.

Permafrost, or permanently frozen ground, has continued to thaw and erode along the Arctic coasts, leaving Indigenous communities with damaged infrastructure.

And perhaps most surprisingly, snow cover in the Eurasian Arctic reached an all-time high in June. The drying up of soils and vegetation that followed contributed to the forest fires that burned millions of acres of taiga, or boreal forest, particularly across Siberia. The fires spewed out a third more heat-trapping carbon dioxide into the atmosphere than the previous year, according to European researchers.

The amount of snow that fell in the Eurasian Arctic was actually above normal this year, said Lawrence Mudryk, a researcher at Environment and Climate Change Canada and lead author of the snow cover section of the assessment. “Despite this, it was still hot enough to melt faster and earlier than usual”, he said.

Heat was omnipresent throughout the Arctic. The average land temperature north of 60 degrees latitude, measured from October 2019 to September, was 1.9 degrees Celsius, or 3.4 degrees Fahrenheit, above the baseline average for 1981-2010 and the second highest in more than a century of record. .

The disproportionate influence of the Arctic is why the assessment, called the Arctic Report Card, has been produced annually for the past 15 years by the National Oceanic and Atmospheric Administration. Over 130 experts from 15 countries contributed to this year’s version.

In recent years, Arctic researchers have increasingly recognized that the region is moving from a climate less characterized by ice and snow than by open water and rain.

In a study published in September, two researchers at the National Center for Atmospheric Research in Boulder, Colorado, argued that for sea ice at least, a permanent change had already occurred. The extent of the ice has now shrunk so much, Laura Landrum and Marika M. Holland wrote: that even an extremely cold year would not produce as much ice as it did decades ago.

Donald K. Perovich, professor at Dartmouth College and lead author of the chapter on sea ice in the assessment, said 2007 was a critical year. “We had the biggest drop in ice extent we have ever seen,” he said. “Although there have been these variations since, we never returned to these levels before 2007.”

“It’s like we’re in this new state,” he added.

The age of sea ice is decreasing as the region warms. Three decades ago, ice at least four years old made up about a third of the Arctic Ocean’s pack ice at the end of winter. This year, according to the assessment, old ice represented less than 5% of the pack ice.

The increasing dominance of younger, and therefore generally thinner, ice has helped reduce the extent of sea ice, Dr Perovich said, because thinner ice is less likely to last a single season. .

The change from old to young ice also resulted in a decrease in the overall ice volume. This year’s volume, measured at the end of the melt season in September, was the second lowest in 10 years during which satellites have made reliable measurements.

The assessment noted how conditions in the Arctic affected the Mosaic expedition, during which a German research icebreaker was deliberately cleared to freeze in the Russian pack ice and drift through the center of the ‘Arctic for almost a year. The expedition, Mosaic, ended in October when the ship left the pack ice between Greenland and Norway and returned to Germany.

At the start of the expedition in September 2019, the ship struggled to find pack ice to use as a mooring thick and stable enough to last for months of drift. And as the the voyage continued, the wind regimes that brought such hot temperatures to the arctic also caused the ice and the ship to drift much faster than expected.