An international team of Earth and environmental scientists has made a significant discovery regarding the Ronne Ice Shelf in West Antarctica, revealing that the shelf did not experience significant melting during the last interglacial period, approximately 120,000 years ago. This finding, which was published in the journal Nature, suggests that the Ronne Ice Shelf could be more resilient to modern climate change than previously thought. The study provides new insights into the behavior of polar ice sheets and their potential response to global warming.
The Importance of the Ronne Ice Shelf
The Ronne Ice Shelf is one of the largest ice shelves in Antarctica, covering an area roughly the size of France. It is a key part of the West Antarctic Ice Sheet, a massive frozen mass that contains vast amounts of the planet’s freshwater. Should the Ronne Ice Shelf melt, it could contribute significantly to global sea level rise—potentially up to 2 meters. Such a rise would have devastating consequences for coastal cities worldwide, flooding metropolitan areas and displacing millions of people.
Because of the potential impact of the Ronne Ice Shelf’s melting on global sea levels, scientists have long been concerned about its stability. Previous research has suggested that the shelf might be vulnerable to changes in climate, particularly because ice shelves are influenced by a combination of air temperature and ocean currents, both of which are affected by climate change. Understanding the history of the Ronne Ice Shelf’s stability during warmer periods in Earth’s past is crucial for predicting how it might behave in response to modern climate changes.
The Study: Core Samples and Ice Analysis
The team’s new study involved drilling ice cores at a site near the edge of the Ronne Ice Shelf, an area known as Skytrain Ice Rise. The researchers selected this location because it is relatively close to the shelf’s edge, where melting and ice loss are more likely to occur. By drilling a hole deep into the ice—down to 651 meters to the underlying bedrock—the researchers aimed to extract a continuous record of climatic conditions over thousands of years.
Ice cores serve as time capsules, preserving environmental conditions at the time the ice was formed. In this case, the scientists hoped to find evidence of past melting events by analyzing sea salt concentrations. Ice shelves, particularly those that extend over water, can trap sea salt particles in the ice as they freeze. If the ice shelf had melted during past warmer periods, the concentration of sea salt near its edges would likely have been significantly higher, since melting ice would release salt from the seawater below.
However, the team found something unexpected. Rather than elevated concentrations of sea salt near the edge of the shelf, the ice core samples showed levels that were consistent with other areas of the shelf—and in some cases, even lower. This suggested that the Ronne Ice Shelf had not undergone significant melting during the last interglacial period. The lack of elevated sea salt concentrations indicated that the ice had remained largely stable during this warmer period, which was characterized by changes in Earth’s orbit and temperatures that were higher than those of today.
In addition to testing for sea salt, the researchers also analyzed isotopes in the ice, which can provide evidence of past weather events and conditions. The results showed no indication of significant melting or changes in the ice structure that would suggest a major retreat or collapse of the shelf during the last interglacial period.
Implications for Modern Climate Change
These findings have significant implications for our understanding of the Ronne Ice Shelf and its potential response to modern climate change. The fact that the shelf did not melt during a period of higher-than-normal temperatures raises the possibility that the Ronne Ice Shelf may be more resilient than previously assumed. It suggests that the shelf could survive modern climate change, even if global temperatures rise, as long as the conditions do not differ significantly from those of the last interglacial period.
However, the researchers also note that there are key differences between the conditions during the last interglacial and those we are experiencing today. One of the most important differences is that ocean temperatures are now significantly higher. As the oceans warm due to climate change, they could contribute to subsurface melting of the ice shelf from below. This process, which occurs when warm ocean water reaches the underside of the ice shelf, could lead to thinning and eventual collapse.
If this subsurface melting is combined with warmer temperatures at the surface, it could create conditions that might cause the Ronne Ice Shelf to destabilize more rapidly than it did during the last interglacial. The researchers caution that while the ice shelf has remained stable in the past, the combination of ocean warming and surface temperature increases could lead to a different outcome in the future.
Conclusion: A Complex Future
The study of the Ronne Ice Shelf provides a valuable perspective on the potential for polar ice sheets to survive modern climate change. The evidence that the shelf did not melt during the last interglacial period suggests that it may have greater stability than previously assumed. However, the researchers also emphasize that modern conditions—particularly warmer ocean temperatures—could lead to different outcomes. The interaction between ocean temperatures, surface warming, and ice shelf dynamics remains complex, and further research is needed to better understand the future of the Ronne Ice Shelf and other ice shelves in Antarctica.
As scientists continue to study the impact of climate change on polar ice, it is clear that the future of the world’s ice sheets will play a critical role in shaping global sea levels. While the Ronne Ice Shelf may be more resilient than we thought, the ongoing rise in global temperatures means that the dynamics of ice shelves will remain an important area of research for the foreseeable future.
References: Eric W. Wolff et al, The Ronne Ice Shelf survived the last interglacial, Nature (2025). DOI: 10.1038/s41586-024-08394-w
Antarctic ice shelf kept its cool during the last interglacial period, Nature (2025). DOI: 10.1038/d41586-025-00190-4