Paris (AFP) – Some of the Greenland ice sheet is thinning further inland than previously thought, likely leading to more sea level rise by the end of this century, a new study said Wednesday.
The findings concern a northeastern section of the giant ice sheet, but the trend is likely to be occurring elsewhere in Greenland and on Earth’s other ice sheet, Antarctica.
The consequences are alarming, as rising sea levels already threaten millions of people living along coastlines who could be underwater in the coming decades and centuries.
Scientists have previously focused on the edges of the Greenland ice sheet to examine active melting as global temperatures rise, largely using satellite data.
But the authors of Wednesday’s study looked further inland, more than 100 kilometers from the coast.
What they found was alarming: the thinning off the coast of Greenland extended from 200 to 300 kilometers (125 to 185 miles).
“What we see happening at the front extends far back into the heart of the ice sheet,” first author Shfaqat Abbas Khan said in a press release about the study, published in Nature.
“The new model really captures what’s happening inland, the old ones don’t… you end up with a completely different mass change or sea level projection,” he told AFP in an interview.
The researchers installed GPS stations on the ice sheet to gather more precise information, and also used satellite data and numerical modeling, which provided a new set of data that could potentially change sea-level rise predictions.
The research was conducted in the Northeast Greenland Ice Stream (NEGIS), which covers about 12 percent of Greenland, according to co-author Mathieu Morlighem.
It found that thinning could add between 13.5 and 15.5 millimeters to sea levels by the end of this century — equivalent to the contribution of the entire Greenland ice sheet over the past 50 years.
“NEGIS could lose six times more ice than existing climate models estimate,” the report says.
One reason for the inland thinning is the intrusion of warm ocean currents, which in 2012 caused the NEGIS floating extension to collapse.
This event “accelerated the ice flow and triggered a wave of rapid ice thinning that spread upstream.”
The Greenland ice sheet is currently the main factor in swelling Earth’s oceans, according to NASA, with the Arctic region warming at a faster rate than the rest of the planet.
In a landmark climate science report last year, the Intergovernmental Panel on Climate Change (IPCC) said the Greenland ice sheet would contribute up to 18cm to sea level rise by 2100 under the highest emissions scenario.
The massive ice sheet, two kilometers thick, contains enough frozen water to raise the world’s seas by more than seven meters (23 feet) in total.
The researchers will now expand their methods to look at other glaciers in Greenland and Antarctica, and some new data could be available in a year or so.
The earth’s surface has warmed, on average, nearly 1.2 degrees Celsius since the pre-industrial era, unleashing a catalog of effects from heat waves to more intense storms.
Under the Paris climate agreement, countries agreed to limit temperature rise to below 2 degrees Celsius.
World leaders are currently meeting in Sharm el-Sheikh, Egypt for UN climate talks aimed at curbing harmful emissions and boosting financing for green developing countries.
Khan said the thinning trend in the Greenland ice sheet will be nearly impossible to reverse, but can at least be slowed with the right policies.
“I really hope they will agree on CO2 reduction and as soon as possible,” he said in a message to leaders at the COP27 climate talks.
© 2022 AFP
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