New research reveals that previously overlooked seasonal melting of the massive East Antarctic ice sheet is happening at a pace that could significantly alter forecasts for global sea level rise. A study focusing on the interactions between the ocean and the ice found that East Antarctica’s floating ice shelves are being rapidly melted from below by warm ocean water during the summer, a dynamic that is largely unaccounted for in current climate models. This finding challenges the long-held view of East Antarctica as a relatively stable region and suggests the continent’s total contribution to rising seas may be seriously underestimated.
The stability of the world’s coastlines is intrinsically linked to the health of Antarctic ice shelves, which act as crucial dams holding back the vast reservoirs of land-based ice. Scientists have discovered that unlike in West Antarctica, where this “basal melting” is a year-round phenomenon, the melting in the east occurs in intense, seasonal spikes. These bursts of melting coincide with the annual retreat of sea ice, which allows warm surface waters to flow into deep cavities beneath the ice shelves. Because this process is not adequately represented in global climate projections, the new findings inject a fresh sense of urgency into understanding the full scope of Antarctica’s vulnerability to climate change.
A Tale of Two Melting Patterns
The research highlights a fundamental difference in the way the ocean is eroding the ice shelves of West and East Antarctica. Using a high-resolution ocean model known as the Whole Antarctic Ocean Model (WAOM), scientists were able to simulate the complex movement of water beneath the ice. The results identified two distinct modes of melting across the continent.
In West Antarctica, the process is more consistent. Warmer, deeper ocean currents continuously flow beneath the ice shelves throughout the year, leading to a steady rate of basal melt. This chronic melting has been the primary focus of scientific concern for decades, as the West Antarctic Ice Sheet is considered less stable due to much of its base resting on bedrock far below sea level.
In contrast, the study revealed that East Antarctica’s ice shelves are subject to a more dramatic, seasonal cycle. During the summer, as sea ice melts and retreats from the coast, sun-warmed surface water gains access to the grounding lines of the ice shelves. This intrusion triggers periods of intense, shallow melting. The process halts and reverses in the winter. As sea ice reforms, areas of open water near the coastline, called polynyas, contribute to a super-cooling of the surface ocean, effectively shutting down the summer melt engine.
The Underestimated Giant
For years, the East Antarctic Ice Sheet was often referred to as a “sleeping giant” by scientists, considered too cold and vast to be a significant near-term contributor to sea level rise. This new understanding of its susceptibility to seasonal ocean warming forces a reevaluation of that stability. The sheer scale of the eastern ice sheet dwarfs its western counterpart; if it were to melt entirely, it holds enough frozen water to raise global sea levels by approximately 52 meters, or over 170 feet. The entire West Antarctic Ice Sheet, in comparison, contains about 5 meters of potential sea level rise.
The new research focused on key ice shelves in East Antarctica, including the Totten Glacier, one of the region’s largest and most rapidly thinning glaciers. The Totten Glacier alone drains a massive area and contains as much ice as the entire West Antarctic Ice Sheet, highlighting how the instability of just a few key eastern glaciers could have global consequences. Evidence of surface meltwater ponding in other areas of East Antarctica further suggests that the giant may be starting to stir from its slumber, making a comprehensive understanding of all melting processes critically important.
Revising Climate Models and Projections
A major implication of the study is the urgent need to improve climate models to better reflect these seasonal dynamics. “Basal melting is a major driver of Antarctic Ice Sheet instability and ice loss,” stated the study’s lead author, Dr. Fabio Boeira Dias of UNSW Sydney. He emphasized that because current models do not fully account for the intricate ways the ocean interacts with the ice shelves, projections of future sea level rise remain uncertain.
Integrating New Data
The failure to incorporate these powerful summer melt pulses could lead to a significant underestimation of ice loss from East Antarctica, particularly as climate change intensifies. Co-author Professor Matthew England noted that the problem is likely to worsen with record-low sea ice levels, more frequent marine heatwaves, and shifting seasons. “If basal melting in East Antarctica is not properly accounted for, future sea level rise may be considerably underestimated,” researchers warned. Improving these models is essential for providing accurate information to policymakers and coastal communities worldwide who must plan for and adapt to rising oceans.
Broader Vulnerabilities Across Antarctica
This discovery of seasonal basal melting adds to a growing body of evidence that all of Antarctica is vulnerable to a warming world. Ice shelves across the continent act as essential barriers, and their weakening or collapse invariably accelerates the flow of land ice into the ocean. Other research has pointed to additional threats, including the 2022 collapse of the Conger ice shelf in East Antarctica, which was triggered by an extreme atmospheric river event. That event demonstrated how a combination of long-term weakening and short-term extreme weather can lead to sudden disintegration.
Looking ahead, the long-term stability of a majority of Antarctica’s ice shelves is in question. One study published in the journal Nature warned that under a high-emission scenario, nearly 60% of the continent’s major ice shelves could become unstable by the year 2300. However, that same study offered a measure of hope, finding that most of these shelves would remain intact if global warming is limited to below 2 degrees Celsius. The findings collectively underscore the sensitivity of the Antarctic ice sheets to both oceanic and atmospheric warming and reinforce the critical need for swift and sustained cuts to greenhouse gas emissions to safeguard the world’s coastlines.
