Science: Thaw in Greenland passes the point of no return
Climate crisis: images taken by drones reveal the instability of the ice sheet in Greenland
The mass of the Greenland ice sheet will
disappear in the coming decades at a higher rate than at any other time in the past 11,700 years
, although the exact amount will depend on global efforts to reduce greenhouse gas (GHG) emissions. ).
That is the main conclusion of a new study published this Monday in
Nature
, prepared by American, Canadian and German researchers.
Scientists have combined statistical simulations with data obtained from drilling ice blocks on the ground, in addition to studying geological records from the southwest of the island and analyzing available climate models.
On this basis, they estimate that the rates of loss in the first two decades of this century (2000-2018) correspond to a disappearance of 6.1 trillion tons per century.
To find similar rates, they have to go back to those that occurred between 10,000 and 7,000 years ago (when about six billion tons were lost per century).
Even more worrying is that the projections for the future (up to the year 2100) announce
an acceleration in the rates of loss of frozen mass
, which will be between 8.8 billion and 35.9 billion tons per century, depending on which one is. the increase in greenhouse gas emissions (in the lowest and highest GHG scenarios, respectively).
"We have altered our planet so much that
the rate of thaw in this century will be greater than anything seen with the natural variability of the last 12,000 years,
" warns Jason Briner, professor of geology at the University at Buffalo and co-author of the investigation.
As the Arctic warms, the Greenland ice sheet loses mass and contributes to sea level rise, at a rate that has risen exponentially since the 1990s. "
If we don't achieve a severe cut in emissions of GHG, it will be totally disproportionate
. "
For this reason, Briner and his colleagues reiterate the need for countries around the world to take action now to reduce emissions, slow the decline of ice sheets and mitigate sea level rise.
"If the world follows a massive energy diet, in line with the scenario that the Intergovernmental Panel on Climate Change calls RCP2.6, our model predicts that the rate of loss of the Greenland ice sheet this century will be slightly higher. to that experienced in the last 12,000 years, "he explains.
"But
under a scenario of high emissions, like the one Greenland is now following, the rate could be four times higher
than the highest values recorded."
Simulations and field work
To develop an accurate model, the researchers brought together experts from different fields: geologists, remote sensing specialists, and even paleoclimatic researchers at NASA's Jet Propulsion Laboratory (JPL).
This multidisciplinary team applied simulation techniques in the ice sheet to evaluate possible changes that occurred in the southwestern sector of Greenland in a period that begins at the beginning of the Holocene (about 12,000 years ago) and that lasts up to 80 years from now, in the year 2100.
To verify their results, they compared the simulations with available historical records and with actual measurements of the ice sheet made by satellites and aerial surveys over the past decades.
Their model data is also
consistent with fieldwork that was done to identify ancient ice sheet boundaries
, a direct observational method for assessing ice mass loss.
"You can model what you want and your model will always give you an answer, but you also need some way to determine if you are correct," says Nicolás Young, professor of geology at Columbia University.
"The model correctly reproduced the same results from the geological reconstruction, which gave us confidence that it was working well and that you were getting significant results."
The authors reconstructed an "extremely detailed" geologic history of how the margin of the southwestern Greenland ice sheet has moved over time, measuring beryllium-10 in smooth stones that settle in moraines.
"These moraines are large deposits of debris that can be found in the landscape that mark the old edge of an ice sheet or glacier. The beryllium-10 measurement tells you how long that rock and that moraine have been there, and therefore
it tells you when the ice sheet was at that exact point and deposited that rock,
"Young details.
Greenland in extreme situation
Studies follow one another with similar results.
Last month, other work published in
Communications Earth & Environment
by German researchers already suggested that the thaw is accelerating.
Snowfall can no longer compensate for the loss of ice in the Arctic territory.
The authors then pointed out that the Greenland ice sheet
registered a new mass loss record in 2019
: the total loss amounted to 532,000 million tons, up from 464,000 million in 2012 (previous record), which must mean an increase 1.5 mm, on average, at sea level.
But despite these results, one of the fundamental conclusions of the scientists in the paper just published in
Nature
is that climate action is still in a position to make a big difference.
The results of the RCP2.6 and RCP8.5 scenarios are very different, in terms of the disappearance of the ice sheet and, consequently, the rise in sea level.
"Our findings are
another wake-up call, especially for high-emission countries like the United States,
" reflects Briner.
"Especially for Americans with more resources, who have a larger energy footprint and who can afford to make lifestyle changes, such as flying less, installing solar panels and driving a fuel efficient vehicle."
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