'Hottest Arctic ever' triggers massive ice melt

MIAMI - The Arctic shattered heat records in the past year, as unusually warm air triggered massive melting of ice and snow and a late fall freeze, US government scientists said Tuesday.

The Arctic region is continuing to warm up more than twice as fast as the rest of the planet, which is also expected to mark its hottest year in modern times

The grim assessment came in the Arctic Report Card 2016, a peer-reviewed report by 61 scientists around the globe that is issued by the National Oceanic and Atmospheric Administration.

The report spans from October 2015 to September 2016, a period when the Arctic's "average annual air temperature over land areas was the highest in the observational record," it said.

"Rarely have we seen the Arctic show a clearer, stronger or more pronounced signal of persistent warming and its cascading effects on the environment than this year," said Jeremy Mathis, director of NOAA's Arctic Research Program.

The Arctic region is continuing to warm up more than twice as fast as the rest of the planet, which is also expected to mark its hottest year in modern times.

Climate scientists say the reasons for the rising heat include the burning of fossil fuels which emit heat-trapping gases into the atmosphere, as well as the El Nino ocean warming trend, which ended mid-year but exacerbated the warming.

The Arctic's annual air temperature over land was 6.3 degrees Fahrenheit (3.5 degrees Celsius) higher than it was in 1900.

The sea surface temperature in the peak summer month of August 2016 was nine degrees Fahrenheit (five degrees Celsius) above the average for 1982-2010 in the Barents and Chukchi seas and off the east and west coasts of Greenland.

"It is apparent that the record-breaking delay in the freeze up of the sea ice cover in the fall of 2016 is associated with unprecedented warm air and ocean surface temperatures," said the report.

- Record low sea ice -

This warming trend has also led to young, thin ice cover that melts easily.

Scientists added a section to the report on noteworthy records set in October and November 2016, even though that was beyond the report's typical time span. The report said this extra section had not yet been peer-reviewed.

"The Arctic sea ice minimum extent from mid-October 2016 to late November 2016 was the lowest since the satellite record began in 1979," it said.

It was also 28 percent less than the average for 1981-2010 in October.

More of the ice that freezes in the winter is thin, and made up of only a single year's worth of freeze rather than the thicker, more resistant ice built up over multiple years.

In 1985, almost half (45 percent) of the Arctic sea ice was called "multi-year ice."

Now, just 22 percent of the Arctic is covered in multi-year ice. The rest is first-year ice.

In Greenland, the ice sheet continued to shrink and lose mass as it has every year since 2002 when satellite measurements began.

Melting also started early in Greenland last year, the second earliest in the 37-year record of observations, and close to the record set in 2012.

- Record-low snow -

The springtime snow cover in the North American Arctic hit a record low in May, when it fell below 1.5 million square miles (four million square kilometers) for the first time since satellite observations began in 1967.

This melting, combined with retreating sea ice, has allowed more sunlight to penetrate the upper layers of the ocean, stimulating widespread blooms of algae.

The tundra is "now releasing more carbon into the atmosphere than it is taking up," said the report.

If the permafrost all melted, "it could have profound effects on weather and climate in the Arctic and the rest of the Earth," the report warned.

That is because twice as much organic carbon is locked in the northern permafrost as is currently in the Earth's atmosphere.

This carbon could dramatically alter weather patterns even more, and boost sea level rise.

The Arctic's people and animals are also suffering from the changes in climate.

Ocean acidification is adding new stress for ocean creatures that need calcium carbonate to build shells, affecting people in the region who rely on fish for food.

And small mammals known as shrews are increasingly becoming infected with parasites that were once known to infect shorebirds, suggesting a northerly shift of some species.