The place that lost 5.8 cubic kilometers of ice per year between 2010 and 2020

One of the largest interconnected glaciers in North America is melting twice as fast as it was before 2010, a team of scientists recently reported.

They described it as an “incredibly worrying” sign that land ice in many places may be disappearing sooner than previously thought.

The researchers estimated that The Juneau Ice Field, which extends along the coastal mountains of Alaska and British Columbia, 5.8 cubic kilometers of ice lost annually between 2010 and 2020. This represents a sharp acceleration compared to previous decades, and even greater than in the mid-twentieth century or earlier.

As societies add more and more carbon dioxide to the atmosphere, glaciers in many regions could cross tipping points beyond which their melting accelerates rapidly, said Bethan Davies, a glaciologist at Newcastle University in England, who led the investigation.

“If we reduce carbon, we have a greater hope of preserving these magnificent ice masses,” Davis said. “The more carbon we put in, the greater the risk that it will be irreversibly and completely wiped out.”

The fate of Alaska’s ice is of great importance to the world. No other region on the planet is expected to contribute more to global sea level rise this century as glacier melt.

The Juneau Icefield covers about 3,900 square kilometers of rugged landscape. The region has become warmer and wetter over the past half century, meaning a longer melt season for glaciers and less snow to replenish them.

The ice field contains 1,050 glaciers. Or at least that’s what it looked like in 2019.

Davies and his colleagues combined decades of glacier measurements with information from satellite images, aerial photos, maps, and surveys.

Scientists found that the rate of ice loss slowed somewhat in the mid-20th century, picked up speed after 1979, and then accelerated further after 2005.

The scientists said the acceleration may have something to do with the way the albedo of the ice affects its melting. As snowfall decreases, more rock is exposed. These darker surfaces absorb more solar radiation, causing the surrounding ice to melt faster. Tourism and forest fires also deposit soot and dust on the surface of glaciers, speeding up their melting.

Another factor is that as the ice sheet thins, more of it is at lower elevations. This exposes more of its flat, broad surface to warm air, causing it to thin faster.

Last year, researchers projected how every glacier on Earth would evolve depending on what we do or don’t do about global warming. The results weren’t encouraging.

Projections suggest that even if countries meet the Paris Agreement’s goal of limiting temperature rise to 1.5 degrees Celsius above pre-industrial conditions, nearly half of the world’s glaciers, about 104,000 in total, could disappear by the end of the year.