Greenland's ice shelves have experienced a significant decline, losing over a third of their volume since 1978, according to researchers. The shrinking ice shelves, caused by warming ocean waters, pose a significant threat to global sea levels. The study warns that if the ice shelves were to collapse entirely, it could result in a sea level rise of approximately 6.8 feet (2.1 meters).

Of the eight ice shelves supporting North Greenland's vast glaciers, three have already collapsed completely, while the remaining five have rapidly retreated. Previously considered stable, the ice shelves were found to be susceptible to disintegration, accelerated by warm ocean temperatures that melt the ice from beneath.

The French National Centre for Scientific Research (CNRS) has estimated that the complete disappearance of Greenland's ice shelves would release enough water to raise global sea levels by 6.8 feet (2.1 meters). The consequences would be severe, with increased rates of ice entering the ocean, thus intensifying the impact on sea levels.

The disintegration of Greenland's ice shelves is further evidenced by the collapse of the Zachariæ Isstrøm, Ostenfeld, and Hagen Brae glaciers since the 2000s. The Ostenfeld ice shelf lost 6.5 cubic miles (27 cubic km) of ice when 80% of it collapsed into the sea in 2003. Similarly, Hagen Bræ saw a collapse between 2001 and 2005, reducing its mass to just over a tenth of its original size.

The remaining ice shelves have also experienced thinning and rapid shrinking, with some retreating up to five miles (8.3 km). These collapses increase the rate of ice entering the ocean, emphasizing the crucial role these ice shelves play as frozen dams, preventing further sea level rise.

Greenland's ice sheet, one of Earth's two continent-scale ice masses, covers almost 80% of Greenland's landmass. If it were to melt entirely, sea levels could rise up to 24 feet (7.3 meters), although experts note that this scenario is highly unlikely. However, the loss of buttressing provided by ice shelves could result in a sea level rise equivalent to 6.6 feet (2.1 meters) from the glaciers located in North Greenland.

Researchers attribute the rapid disintegration of Greenland's ice sheet to increasing ocean temperatures. Between 1965 and 2000, ocean temperatures in Western North Greenland rose modestly from 31.8°F (-0.1°C) to 32°F (0.0°C). However, between 2000 and 2015, temperatures increased faster, reaching 32.45°F (0.35°C). The North East saw an even steeper increase, with temperatures rising from 32.7°F (0.4°C) to 34.2°F (1.2°C) between 1990 and 2020.

Recent studies suggest that if global temperatures continue to rise at the current pace, sea levels could increase by an additional 4.6 feet by 2150. Limiting global warming to 3.6°F (2°C) above pre-industrial levels, a target of the Paris Agreement, would still be insufficient to slow down sea level rise. 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 the acceleration of sea level rise be avoided.

Global sea levels are projected to rise by as much as 1.2 meters (4 feet) by 2300, even if the goals of the 2015 Paris Agreement are achieved. The melting of ice from Greenland to Antarctica is expected to reshape coastlines and pose a threat to low-lying areas and coastal cities.

To mitigate the impending rise, it is essential to reduce emissions promptly. The report emphasizes the urgency of curbing emissions to prevent a more significant increase in sea levels. The current trajectory suggests that none of the nearly 200 nations that signed the Paris Agreement are on track to meet their pledges, making decisive action crucial in combating climate change's effects.