Greenland’s Ice Sheet Nearing a Point of No Return

Greenland’s ice sheet, spanning over 1.7 million square kilometers, stands as the largest freshwater reservoir in the Northern Hemisphere. However, this colossal body of ice is undergoing a rapid transformation. Since the 1980s, the ice sheet has already lost more than a trillion tonnes of its total mass, with melting rates accelerating by six times over the past decade. Alarmingly, recent studies reveal that 30 million tonnes of ice are being lost from Greenland’s ice sheet every hour.

This unprecedented rate of melting is directly linked to the warming atmosphere and oceans. The consequences of this loss are twofold: rising sea levels and alterations in ocean salinity. While these changes have immediate effects on the marine ecosystems in Greenland’s vicinity, they also pose global risks, particularly for coastal communities worldwide. Projections indicate that if Greenland’s ice sheet were to completely melt, global sea levels could rise by 7 meters.

The Tipping Point for Irreversible Melting

New research published in The Cryosphere has provided insights into the tipping point—the moment when the loss of ice mass might become irreversible, potentially leading to the complete meltdown of the Greenland ice sheet. Dr. Michele Petrini, from the Bjerknes Centre for Climate Research in Norway, led the study alongside his colleagues. Their goal was to determine the point at which the Greenland ice sheet’s mass loss could spiral out of control.

The team conducted an in-depth analysis of the surface mass balance of the ice sheet, which is the difference between the snow that accumulates on the surface and the ice lost due to melting. To investigate how different climates would affect this balance, they employed climate modeling simulations. Their results revealed that once the Greenland ice sheet loses around 230 gigatons of ice in a single year—a loss amount equivalent to 60% of the surface mass balance when compared to pre-industrial levels—it will reach the tipping point. This tipping point would trigger a rapid and irreversible process of melting, leading to the eventual collapse of the ice sheet over 8,000 to 40,000 years.

This tipping point is closely linked to global warming. According to the model, when the Earth’s global mean temperature rises by about 3.4°C above pre-industrial levels, the ice sheet’s mass balance will tip beyond recovery. As of 2024, the global temperature has already reached 1.5°C above pre-industrial levels, the first time this threshold set by the 2015 Paris Agreement has been exceeded. If this temperature rise continues unchecked, the Greenland ice sheet’s fate could be sealed.

The Role of Topography in Ice Sheet Melting

The research also highlights the importance of topography—the physical features of the land—on the Greenland ice sheet’s ability to retain its mass. Specifically, the study points to the influence of elevation on the ice sheet’s surface mass balance. The ice sheet tends to retreat from lower elevations, eventually leaving behind remnant pockets that form ice caps on higher terrain. In particular, glacial isostatic adjustment plays a significant role in the ice sheet’s retreat. As ice melts, it reduces the weight pressing down on the underlying bedrock, causing the land to slowly rise over time.

However, there is a critical tipping point in this dynamic. If the ice sheet melts at a faster rate than the land can rise, the negative surface mass balance becomes more pronounced. Once the ice mass is reduced by approximately 50%, the melting process becomes self-reinforcing, and the ice sheet could be on a path to near-complete loss. This negative mass balance could continue for thousands of years.

The Role of Feedback Loops in Accelerating Ice Loss

The feedback loops associated with ice-albedo effects also exacerbate the melting process. Albedo refers to the reflectivity of a surface, with ice having a high albedo, meaning it reflects most of the incoming solar radiation. As the ice sheet melts and exposes darker surfaces like land and ocean, these surfaces absorb more heat, further warming the surrounding environment and accelerating the melting of the ice. This creates a positive feedback loop where less ice leads to greater absorption of heat, which in turn causes more melting.

As the century progresses, the loss of ice from surface melting is likely to outpace the loss from the ice sheet’s margins as they retreat inland. The shift from ice sheet margin loss to surface melting will further accelerate the process, especially as feedback loops become more pronounced.

Western Greenland: A Potential Lifeline for the Ice Sheet

The study also explores a particular region of the ice sheet—the western margin of Greenland—which may play a pivotal role in the overall stability of the ice sheet. This area, located along the coastal highlands, has been crucial in preserving the ice sheet’s mass in the past. When the western margin remains connected to the coastline, it helps stabilize the ice sheet by providing high-elevation areas that limit ice loss.

However, if this western margin loses its coastal connection, the ice sheet could retreat inland, triggering a chain reaction of ice loss that might result in the loss of over 80% of its mass. This process could resemble the events of the last interglacial period, roughly 130,000 to 115,000 years ago, when elevated western topography helped prevent the complete loss of the ice sheet. During that period, the Greenland ice sheet likely benefited from the presence of ice caps on high-elevation coastal regions, which kept the ice sheet stable and prevented total collapse.

This discovery suggests that if we can maintain the integrity of Greenland’s western coastal margin, the ice sheet may have a chance of stabilizing and preventing the worst outcomes predicted by current models. This region, along with the continued preservation of high-elevation ice, might serve as a buffer that slows the total collapse of the ice sheet.

Limitations and Future Directions

While the study presents compelling evidence for the tipping point at which the Greenland ice sheet could begin to melt irreversibly, it is important to note some caveats. The modeling in this study does not account for ice-atmosphere feedbacks, which could influence precipitation and cloud cover over the ice sheet. These effects could potentially slow the retreat of the ice sheet by increasing snowfall and thickening the ice. However, the researchers argue that the influence of glacial isostatic rebound—the rise of the land following the melting of ice—will likely play a more significant role in the long-term stability of the ice sheet.

Despite these uncertainties, the researchers’ conclusion is clear: human-driven climate change is pushing us dangerously close to the tipping points that could lead to irreversible loss of the Greenland ice sheet. As a result, they stress the importance of global efforts to combat climate change. By limiting temperature increases and reducing greenhouse gas emissions, we can prevent the Greenland ice sheet from passing its tipping point, thus avoiding devastating consequences for both sea levels and global ecosystems.

Conclusion

The fate of the Greenland ice sheet is intricately tied to the future of our planet’s climate. As the ice sheet continues to lose mass at unprecedented rates, the potential for irreversible melting grows. New research highlights the critical role of topography, feedback loops, and climate models in predicting the ice sheet’s future. The western Greenland region, in particular, may offer a lifeline, but only if we can mitigate the impacts of climate change and prevent the global temperature from rising further.

The clock is ticking, and urgent action is needed to avoid crossing the tipping point that could set in motion the irreversible collapse of Greenland’s ice sheet.

Reference: Michele Petrini et al, A topographically controlled tipping point for complete Greenland ice sheet melt, The Cryosphere (2025). DOI: 10.5194/tc-19-63-2025.