Some of Greenland’s ice sheet is thinning inland than previously thought, which is likely to result in more sea-level rise by the end of this century, according to a new study Wednesday.
The results relate to a northeastern section of the giant ice block cover, but the trend is likely taking place elsewhere on Greenland and Earth’s other ice sheet, in Antarctica.
The impact is worrying as sea level rise is already threatening millions of people living on coasts that could become submerged in the decades and centuries to come.
Scientists have previously focused on the edges of the Greenland ice sheet to study active melting as global temperatures rise, mostly 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 of Greenland’s coast stretched back 200 to 300 kilometers (125 to 185 miles).
“What we’re seeing at the front extends far back into the heart of the ice sheet,” lead author Shfaqat Abbas Khan said in a press release about the study, published in Nature.
“The new model really captures what’s going on 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 accurate information, and also used satellite data and numerical models, all of which provided a new dataset likely to alter projections of global sea level rise.
The research was conducted on the Northeast Greenland Ice Stream (NEGIS), which is estimated to cover 12 percent of Greenland, according to co-author Mathieu Morlighem.
It found that thinning could raise sea levels by 13.5 to 15.5 millimeters by the end of this century – equivalent to the contribution of the entire Greenland ice sheet over the past 50 years.
“The NEGIS could lose six times more ice than existing climate models estimate,” the report says.
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One reason for the internal thinning is the intrusion of warm ocean currents that collapsed the floating extension of the NEGIS in 2012.
This event “accelerated ice flow and triggered a wave of rapid ice thinning that spread upstream”.
The Greenland Ice Sheet is currently the main contributor to the swelling of Earth’s oceans, according to NASA, with the Arctic region warming faster than the rest of the planet.
In a landmark report on climate science last year, the Intergovernmental Panel on Climate Change (IPCC) said the Greenland ice sheet would contribute up to 18 centimeters of sea-level rise by 2100 in the highest emissions scenario.
The massive ice sheet, two kilometers thick, contains enough frozen water to raise the global seas by over seven meters (23 feet).
Researchers will now extend their methods to study other glaciers on Greenland and Antarctica, and some new data could be available in about a year.
The Earth’s surface has warmed by an average of nearly 1.2 degrees Celsius since pre-industrial times, triggering a range of impacts from heat waves to more violent storms.
As part of the Paris climate agreement, the countries have agreed to limit warming to well below 2°C.
World leaders are currently meeting in Sharm el-Sheikh, Egypt for UN climate talks aimed at reducing harmful emissions and boosting finance for green developing countries.
Khan said the thinning trend on Greenland’s ice sheet is nearly impossible to reverse, but could at least be slowed with the right policies.
“I really hope they agree on CO2 reduction as soon as possible,” he said in a message to leaders at the COP27 climate talks.
