The heat wave that smashed high temperature records in five European countries a week ago is now over Greenland, accelerating the melting of the island's ice sheet and causing massive ice loss in the Arctic.

Greenland, the world's largest island, is a semi-autonomous Danish territory between the Atlantic and Arctic oceans that has 82 per cent of its surface covered in ice.

The area of the Greenland ice sheet that is showing indications of melt has been growing daily, and hit a record 56.5 per cent for this year on Wednesday, said Ruth Mottram, a climate scientist with the Danish Meteorological Institute. She says that's expected to expand and peak on Thursday before cooler temperatures slow the pace of the melt.

More than 10 billion tonnes of ice was lost to the oceans by surface melt on Wednesday alone, creating a net mass ice loss of some 197 billion tonnes from Greenland in July, she said.

Heat wave in <a href="https://twitter.com/hashtag/Greenland?src=hash&ref_src=twsrc%5Etfw">#Greenland</a> - yesterday, 31 July, had an ice loss of more than 10 gigatonnes (= billion tonnes or km³) just because of surface melt. Melt from the <a href="https://twitter.com/hashtag/icesheet?src=hash&ref_src=twsrc%5Etfw">#icesheet</a> in July, almost equal to the water volume of Lake <a href="https://twitter.com/hashtag/Athabasca?src=hash&ref_src=twsrc%5Etfw">#Athabasca</a>, contributed about half a mm to sea level rise. <a href="https://t.co/QkKUENOizt">pic.twitter.com/QkKUENOizt</a> —@MartinStendel

"It looks like the peak will be today. But the long-term forecast is for continuing warm and sunny weather in Greenland, so that means the amount of the ice loss will continue," she said Thursday in a telephone interview from Copenhagen.

The scope of Wednesday's ice melt is a number difficult to grasp. To understand just how much ice is being lost, a mere one billion tonnes — or one gigatonne — of ice loss is equivalent to about 400,000 Olympic-sized swimming pools, the Danish Meteorological Institute said. And 100 billion tonnes corresponds to a 0.28 mm rise in global sea levels.

Mottram said since June 1 — roughly the start of the ice-loss season — the Greenland ice sheet has lost 240 gigatonnes this year. That compares with 290 gigatonnes lost overall in the 2012 melt season, which usually goes through the end of August.

A June 2019 study by scientists in the U.S. and Denmark said melting ice in Greenland alone will add between five and 33 centimetres to rising global sea levels by the year 2100. If all the ice in Greenland melted — which would take centuries — the world's oceans would rise by 7.2 metres, the study found.

Travelling heat wave

The current melting has been brought on by the arrival of the same warm air from North Africa and Spain that scorched European cities and towns last week, setting national temperature records in Belgium, Germany, Luxembourg, the Netherlands and Britain.

In Russia, meanwhile, forest fires caused by hot, dry weather and spread by high winds are raging over nearly 30,000 square kilometres of territory in Siberia and the Russian Far East, an area the size of Belgium. Smoke from these fires, some of them in Arctic territory, is so heavy it can easily be seen in satellite photos and is causing air quality problems in Russia's third-largest city, Novosibirsk.

Protesters in Moscow on Thursday were demanding that the government do more to fight the blazes. Greenland has also been battling a slew of Arctic wildfires, something that Mottram said was uncommon in the past.

Smoke from wildfires are seen here, centre, drifting across Russia on July 25. (NASA/Terra/Modis/Suomi NPP/VIIRS)

In Greenland, the melt area this year is the second-biggest in terms of ice area affected, behind more than 90 per cent in 2012, said Mark Serreze, director of the National Snow and Ice Data Center in Boulder, Colo., which monitors ice sheets globally. Records go back to 1981.

A lot of what melts can later refreeze onto the ice sheet, but because of the conditions ahead of this summer's heat wave, the amount of ice lost for good this year might be the same as in 2012 or more, according to scientists. They noted a long buildup to this summer's ice melt — including higher overall temperatures for months — and a very dry winter with little snow in many places, which would normally offer some protection to glacier ice.

"This is certainly a weather event superimposed on this overall trend of warmer conditions" that have increasingly melted Greenland ice over the long term, Serreze said.

Compounding the melt, the Greenland ice sheet started out behind this year because of the low ice and snow accumulation, said Snow and Ice Data Center scientist Twila Moon.

Increased frequency

With human-caused climate change, "there's a potential for these kind of rates to become more common 50 years from now," Moon said.

Heat waves have always occurred, but Mike Sparrow, a spokesperson for the UN World Meteorological Organization, noted that as global temperatures have risen, extreme heat waves are now occurring at least 10 times more frequently than a century ago. This year, the world saw its hottest month of June ever.

"These kinds of heat waves are weather events and can occur naturally but studies have shown that both the frequency and intensity of these heat waves have increased due to global warming," Sparrow said in a telephone interview from Geneva.

He noted that sea ice extent in the Arctic and Antarctic are both currently at record lows.

"When people talk about the average global temperature increasing by a little more than one degree (Celsius), that's not a huge amount to notice if you're sitting in Hamburg or London, but that's a global average and it's much greater in the polar regions," he said.

Even though temperatures will be going down in Greenland by the end of this week, the ice melt is not likely to stop any time soon, Mottram said.

"Over the last couple of days, you could see the warm wave passing over Greenland," she said. "That peak of warm air has passed over the summit of the ice sheet, but the clear skies are almost as important, or maybe even more important, for the total melt of the ice sheet."

She added that clear skies are likely to continue in Greenland "so we can still get a lot of ice melt even if the temperature is not spectacularly high."