- Of the eight ice shelves in North Greenland, three have collapsed completely
- Ice shelves hold back glaciers from the sea and prevent sea levels from rising
Greenland’s ice shelves have lost more than a third of their volume since 1978, researchers have warned.
Warm ocean waters have accelerated the disintegration of the vital ice shelves, melting them from beneath and increasing their risk of collapse.
Of the eight ice shelves which support North Greenland’s vast glaciers, three have already collapsed completely, while the remaining five have rapidly retreated.
As the ocean continues to warm, scientists say the ice shelves will continue to retreat – with severe consequences for global sea levels.
If these disappear entirely, these ice shelves could release enough water to raise global sea levels by 6.8ft (2.1m), according to experts from the French National Centre for Scientific Research (CNRS).
Greenland’s ice shelves were previously believed to be stable, unlike the more sensitive regions of the Polar Ice Cap.
However, scientists used field observations, aerial photography, satellite data, and regional climate models to show that the ice shelves have undergone a rapidly accelerating collapse.
Since the 2000s, the floating ice shelves of Zachariæ Isstrøm, Ostenfeld and Hagen Brae glaciers have completely collapsed.
In 2003, 80 per cent of the Ostenfeld ice shelf collapsed into the sea, losing 6.5 cubic miles (27 cubic km) of ice.
Likewise, Hagen Bræ collapsed between 2001 and 2005, leaving a little more than a tenth of its original mass behind.
The other remaining ice shelves have also thinned and shrunk rapidly, with some retreating up to five miles (8.3km).
The danger of these collapses is that they will increase the rate at which ice enters the ocean, which could have an enormous impact on sea levels.
The ice shelves function like giant frozen dams, which hold back the glaciers from entering the sea.
Greenland is already responsible 17.3 per cent of the rise in sea levels between 2006 and 2018.
However, the glaciers of North Greenland are hosting enough ice to raise sea level by 6.6 feet (2.1 meters).
Writing in Nature Communications, the researchers, led by Romain Millan, said: ‘Overall, 25% of the ice sheet area is drained through former or remaining ice shelves, which represents a sea level rise equivalent of 2.1 m.
‘If the glaciers located in North Greenland lose the buttressing provided by ice shelves, the increase in discharge could rival the largest contributors to Greenland ice mass loss.’
Researchers say that the driving factor behind the rapid disintegration of Greenland’s ice sheet is rising ocean temperatures.
Ocean temperatures in Western North Greenland increased modestly between 1965 and 2000, rising from 31.8°F (-0.1°C) to 32°F (0.0°C).
However, between 2000 and 2015 ocean temperatures increased faster as they rose from 32°F (0.0°C) to 32.45°F (0.3°5C).
In the North East, temperatures rose even faster and climbed from 32.7°F (0.4°C) to 34.2°F (1.2°C) between 1990 and 2020.
The authors added: ‘The observed increase in melting coincides with a distinct rise in ocean potential temperature, suggesting a strong oceanic control on ice shelves changes.’
Recent studies suggest that a worst case scenario in which global temperatures continue to rise at the current pace could see the oceans rise by an extra 4.6 feet by 2150.
If global emissions are only weakly cut, temperatures could triple according to scientists from Pusan National University in South Korea and Fabian Schloesser at the University of Hawaii.
Even limiting global warming to 3.6°F (2° C) above pre-industrial levels – a key aim of the Paris Agreement – would be insufficient to slow down the rate at which sea levels are rising.
Only by limiting global temperature increase below 3.2°F (1.8°C) relative to pre-industrial levels by the end of this century can sea level rise acceleration be avoided, the new study warns.
If sea levels continue to rise at current rates then large parts of the United Kingdom could be at risk of flooding.
Dr. Thomas Hughes is a UK-based scientist and science communicator who makes complex topics accessible to readers. His articles explore breakthroughs in various scientific disciplines, from space exploration to cutting-edge research.
