Greenland’s ice is starting to melt faster than at any time in the past 12,000 years, research has shown, that it will raise sea levels and could have a marked impact on ocean currents.
New measurements show that the melting rate matches any geological record for the Holocene period – defined as the period since the last ice age – and is likely to accelerate, according to an article published in the journal Nature.
According to the study, increased ice loss is likely to lead to a sea level rise of between 2 cm and 1
Jason Briner, professor of geology at the University of Buffalo and lead author of the paper, said, “We have changed our planet so much that the ice sheet melt rates this century are on pace to be greater than anything we have seen under natural variability of the ice sheet over the past 12,000 years. “
These changes, over a relatively short period of less than a century, appear to be unprecedented. The Greenland ice sheet shrank between 10,000 and 7,000 years ago and has slowly accumulated over the past 4,000 years. The current melting will reverse this pattern and within the next 1,000 years, if global warming continues, the vast ice sheet is likely to vanish entirely.
If greenhouse gas emissions continue to rise sharply, the melting rate could accelerate further to four times that seen in the past 12,000 years.
“We are increasingly confident that we are about to experience unprecedented rates of ice loss from Greenland unless greenhouse gas emissions are substantially reduced,” wrote Andy Aschwanden, of the University of Alaska Fairbanks Institute of Geophysics. , in a commentary accompanying the study.
The findings underscore the extent of the changes that human actions are causing on the planet. Last week, a separate team of scientists found that the melting of the Antarctic ice sheet would continue even if the world achieves the Paris Agreement goal of keeping the temperature at no more than 2 ° C, and would eventually raise the level. of the sea of 2.5 meters at that warming level.
Although the Antarctic ice sheet, like the Greenland ice sheet, will take centuries to melt, the study found that the melting trend that had been set in motion by human climate change was likely extremely difficult, if not impossible, to reverse.
Arctic sea ice is also melting rapidly. This year’s summer sea ice minimum was the second lowest in the past 40 years of continuous measurements. Unlike the Greenland ice sheet, which is found on earth, the Arctic ice sheet floats and therefore its melting will not have a major impact on sea level.
However, its melting further accelerates warming by reducing the Earth’s albedo – the reflection of light back into space from the ice – and exposes the darker water below, which absorbs more heat.
The findings also follow a study from last month which found that last year’s melting in Greenland would likely be the worst in centuries.
The team behind the latest Greenland study made their own estimates by producing a computer model of a section of the southwestern region of the ice sheet over the past 12,000 years and then projecting forward to the end of this century.
They compared their findings with what we can say actually happened with the ice, through satellite measurements and other instruments, and also by mapping the position of boulders containing beryllium-10.
These are deposited by glaciers as they move, and beryllium-10 measurements can reveal how long the boulders have been in place, and thus where the edge of the ice sheet was when the boulder was deposited.
“Prior to our study, science didn’t have much control over the long-term trends in the ice loss rate in Greenland,” Briner said.
“There has been a lot of painstaking work done to quantify today’s rates of ice mass loss in Greenland, but we didn’t have a long-term view to put today’s rates into perspective. Our study provides that perspective.”