Major sea-level rise now 'locked in' due to melting of Greenland Ice Sheet

If the area’s record melt year of 2012 becomes routine, the ice cap could deliver almost a 78cm sea-level rise in the future

Greenland's enormous ice sheet has lost 4.7 trillion tonnes in 20 years. AFP

A major sea-level rise is now locked in as a result of the melting of the Greenland Ice Sheet, even if more is done to halt global warming, a new study suggests.

Scientists say damage done to date will cause a minimum sea-level rise of 27cm, as 110 trillion tonnes of ice thaws.

And if the area’s record melt year of 2012 occurs routinely, the ice cap could deliver almost a 78cm sea-level rise in the future, said the scientists behind the study, which was published in the journal Nature Climate Change.

That would serve as “an ominous prognosis for Greenland’s trajectory through a twenty-first century of warming,” wrote the authors.

Professor Jason Box from the National Geological Survey of Denmark and Greenland (Geus), who led the research, said the 27cm change was “very conservative rock-bottom minimum” and guaranteed, despite all efforts to prevent it.

“Realistically, we will see this figure more than double within this century,” he told The Guardian.

The Greenland Ice Sheet, which is on average 2,600 metres thick, is the world’s second largest after Antarctica.

It contains roughly 8 per cent of the planet’s total supply of fresh water.

Melting of the ice sheet has caused about 25 per cent of global sea level rise over the last few decades, according to estimates.

But if the entire sheet thawed, US space agency Nasa has said the sea level would rise by seven metres, endangering the lives and livelihoods of nearly one-third of the world’s population, who live in or near a coastal zone.

A sea-level rise of only between 60cm and 90cm, which is theoretically possible under one of the study’s scenarios, if record melt years become common, would, according to Nasa, create serious global problems: increased coastal erosion, salt water encroachment, loss of barrier formations like islands, sandbars, and reefs, and increased storm surge damage.

The study used a different methodology compared to previous analyses, which have typically used computer models to predict ice cap behaviour.

For this one, scientists studied satellite measurements of ice loss and the shape of the cap.

That allowed them to calculate how far global heating to date has pushed the sheet from the balance where snowfall matches the amount of ice lost.

Last year, scientists gave warnings that the melting of the Jakobshavn drainage basin in Greenland was nearing the tipping point from where it could not recover.

Data indicated that a critical threshold had been reached after a century of accelerated melting.

And in 2012, the ice sheet in Greenland underwent an unprecedented rate of thawing. For a few days during July, 97 per cent of the entire ice sheet indicated surface melting.

“If [2012] becomes a normal year, then the committed loss grows to 78cm, which is staggering, and the fact that we’re already flickering into that range [of ice loss] is shocking,” Dr William Colgan, who is at Geus, told The Guardian.

“But the difference between 78cm and 27cm highlights the [difference] that can be made through implementing the Paris agreement. There is still a lot of room to minimise the damage.”

However, he said there is growing support about the likelihood of a multi-metre sea level rise in the next 100 to 200 years.

Scientists say there are ominous signs of temperature change in both polar regions.

In February 2020, a research base on the northern tip of the Antarctic Peninsula recorded a record high temperature of 18.3°C, according to Argentina’s national meteorological service. And the mercury hit 38°C in the Russian town of Verkhoyansk, an Arctic record.

And in the following year, rain fell at the highest point on the Greenland ice sheet in the Arctic for the first time on record.

Earlier this year, scientists were stunned when the temperature in the Antarctic plateau rose 40°C higher than normal.

Concordia Station, located high on the Antarctic Plateau, hit a record temperature of -11.8ºC, more than 40ºC above the annual average for three days in March.