Greenland's melt goes into hyper-drive with unprecedented ice loss in modern times

The Greenland and Antarctic ice sheets are now losing more than three times as much ice a year as they were 30 years ago, according to a new, comprehensive international study.

Key points: From 1992 to 1996, the two ice sheets — which hold 99 per cent the world's freshwater ice — shrank by more than 100 billion tonnes a year, two-thirds of it from Antarctica

From 1992 to 1996, the two ice sheets — which hold 99 per cent the world's freshwater ice — shrank by more than 100 billion tonnes a year, two-thirds of it from Antarctica However, from 2017 to 2020, the newest data available, the combined melt soared to 372 billion tonnes a year, more than two-thirds of it from Greenland

However, from 2017 to 2020, the newest data available, the combined melt soared to 372 billion tonnes a year, more than two-thirds of it from Greenland Since 1992, the Earth has lost 7.5 trillion tonnes of ice from the two ice sheets, an international study found

Using 50 different satellite estimates, researchers found that Greenland's melt has gone into hyper-drive in the past few years.

Greenland's average annual melt from 2017 to 2020 was 20 per cent more a year than at the beginning of the decade and more than seven times higher than its annual shrinkage in the early 1990s.

The new figures "are pretty disastrous, really" said study co-author Ruth Mottram, a climate scientist at the Danish Meteorological Institute.

"We're losing more and more ice from Greenland," Dr Mottram said.

Study lead author Inès Otosaka, a glaciologist at the University of Leeds in the United Kingdom, said that speeded-up ice sheet loss was clearly caused by human-caused climate change.

From 2017 to 2020, Greenland averaged ice loss of about 257 billion tonnes of melting a year, compared to just 213 billion tonnes annually from 2012 to 2016. ( )

From 1992 to 1996, the two ice sheets — which hold 99 per cent of the world's freshwater ice — were shrinking by 116 billion tons (105 billion tonnes) a year, two-thirds of it from Antarctica.

However, from 2017 to 2020, the newest data available, the combined melt soared to 410 billion tons (372 billion tonnes) a year, more than two-thirds of it from Greenland, said the study which was published in Thursday's journal Earth System Science Data.

"This is a devastating trajectory," said US National Snow and Ice Centre's deputy lead scientist, Tilba Moon, who was not part of the study.

"These rates of ice loss are unprecedented during modern civilisation," Dr Moon said.

Since 1992, the Earth has lost 8.3 trillion tons (7.5 trillion tonnes) of ice from the two ice sheets, the study found.

That's enough to flood the entire United States with 0.9 metres of water or submerge France in 15 metres.

However, because the world's oceans are so huge, the melt just from the ice sheets since 1992 still only adds up to a little less than 0.2 metres of sea level rise, on average.

Globally, sea level rise is accelerating and melt from ice sheets has gone from contributing 5 per cent of the sea level rise to now accounting for more than 25 per cent, the study found.

The rest of the sea rise comes from warmer water expanding and from melting glaciers.

A team of more than 65 scientists regularly calculates ice sheet loss in research funded by NASA and the European Space Agency, with Thursday's study adding three more years of data.

They use 17 different satellite missions and examine ice sheet melt in three distinct techniques, Dr Otosaka said, and all the satellites, radar, on-the-ground observations and computer simulations basically say the same thing: Ice sheet melting is accelerating.

Rising sea levels have been blamed for unprecedented and frequent floods in some of the most-vulnerable countries to climate change, such as Bangladesh, Pakistan and Afghanistan. ( )

Ice responds rapidly to climate change

The latest figures also showed what looks like a slowing of melting in parts of Antarctica, which has much more ice than Greenland.

That's mostly due to smaller and fleeting weather changes and the overall longer-term trend still shows an acceleration of melting in Antarctica, Dr Mottram said.

Antarctica from 2017 to 2020 is still losing about 127 billion tons (115 tonnes) of ice a year, down 23 per cent from earlier in the decade but, overall, up 64 per cent from the early 1990s.

"While mass loss from Greenland is outpacing that from Antarctica, there are troublesome wild cards in the south, notably behaviour of the Thwaites glacier," which is nicknamed the Doomsday Glacier, said distinguished geography professor and the director of the US snow and ice centre, Mark Serreze, who was not part of the study.

Study authors used changes in gravity and in ice height and measured how much snow fell, how much snow melted, how much ice was lost in icebergs calving and eaten away from underneath by warmer water etching through the ice.

"This matters, because rising sea levels will displace and/or financially impact hundreds of millions of people, if not billions, and will likely cost trillions of dollars," University of Colorado ice researcher and former NASA chief scientist Waleed Abdalati said.

The study "is not so much surprising as it is disturbing", Professor Abdalati said in an email.

"A few decades ago, it was assumed that these vast reservoirs of ice changed slowly but — through the use of satellite observations, field observations and modelling techniques — we have come to learn that ice responds rapidly to our changing climate."