Why is the ice melting so fast?

Greenland is a huge region in the Arctic and the world's biggest island. It's usually frozen, but as temperatures in the far north rise faster than most other places on Earth, its massive ice sheets are melting into a warming ocean.

One recent study found that Greenland is the warmest it's been in 1000 years. The resulting Arctic meltdown was responsible for 40% of the world's rising seas in 2019.

Scientists are concerned that Greenland's Petermann glacier is breaking up. Sitting on the edge of the ocean, its retreat will expose the massive ice sheets behind it to warming ocean water. Researchers who have been studying the glacier said projected sea level rise could double as a result. 

Rapid retreat of the planet's largest ice sheet will pose a threat to low-lying islands and coastal areas that are vulnerable to sea level rise. But in Greenland itself, the Indigenous Inuit people are literally living on thin ice, which means a loss of habitat for local wildlife like seals, bears and walruses.

In the southern polar region, Antarctica, sea ice had been increasing in size by about 1% per decade since the 1970s. But last year, it was at its lowest-ever recorded level. 

There are fears that the Thwaites glacier, which is the size of Florida and the biggest chunk of ice on the planet, is starting to crack up due to warming Antarctic waters.

Since the southern polar region is so isolated, scientists are still trying to figure out just how bad things could get there.   

Why is the Arctic melting so fast?

During the forty-odd years between 1979 and 2021, scientists saythe Arctic warmed four times more quickly than the rest of the globe. It's unsurprising, then, that two-thirds of global ice melt is happening in Greenland, researchers have now confirmed. 

Things are so bad that most of the epic Greenland ice sheet is expected to melt if the world heats up by 1.6 degrees Celsius compared with when industrialization began around 250 years ago. (Right now, the world is at around 1.2 degrees Celsius). Once that happens, sea levels could rise by as much as seven meters.

Experts believe the Arctic is warming faster than the Antarctic because there is a lot more surrounding liquid water in the region during summer and autumn, when sea ice declines. This water absorbs sunlight — as opposed to ice, which reflects it — and the ocean warms as a result.

Since the Arctic is an ocean and consists mostly of sea ice, it has also been affected more by rising ocean temperatures than the Antarctic, which consists mostly of ice-covered land.

In addition, the ocean currents in the Southern Ocean tend to bring up deep cold water that keeps the Antarctic region relatively cool. 

Still, ice melt in the Antarctic is increasing: it's up around 65% compared with the 1990s. 

Mountain glaciers are also disappearing

Polar glaciers aren't the only victim of global heating caused largely by burning fossil fuels that emit greenhouse gases.

The world's mountain glaciers, which number roughly 200,000, are melting much faster than they can accumulate these days. This poses a major problem because, although they cover less than 0.5% of the Earth's surface, these "water towers" provide fresh water to about a quarter of the world's population.

Glaciers also feed the rivers that irrigate the crops which hundreds of millions of people across Asia, South America and Europe depend on for their survival. Without them, many people may suffer from both thirst and hunger.

Scientists say this water tower retreat puts almost 2 billion people at risk of water scarcity.

South American cities like Santiago in Chile have had much of their drinking water supply literally dry up as glaciers in the nearby Andes Mountains retreat.

Meanwhile, glaciers in the European Alps, which supply so much fresh water across the region, have shrunk by about half since 1900 and will be almost ice-free by century's end if nothing more is done to curb warming. 

Dark ice melting faster than clean ice

Glaciers covered in rock and dirt tend to melt faster than cleaner ice because the dark matter absorbs more energy from the sun.

These stones and rocks can heat up to temperatures as hot as 40 degrees Celsius in high elevations, researchers say.

When the ice melts as a result, it can lead to broader glacial meltdown.

But an emerging problem in the western Greenland ice sheet is the unexplained arrival of a purple algae that is darkening the ice surface and absorbing more sunlight.  

These algae blooms turn purple to shield themselves from UV radiation but then turn a sooty black, which further intensifies the heating.

Edited by: Sarah Steffen