The recent collapse of a major ice shelf in East Antarctica, a region long considered stable, is forcing scientists to reconsider the mechanisms and timeline of ice loss on the continent. The disintegration of the Conger-Glenzer Ice Shelf in March 2022 was not caused by the surface meltwater that has famously fractured shelves on the Antarctic Peninsula, but rather by a combination of factors that weakened the ice over decades. This unexpected event has highlighted the vulnerability of the entire continent to a warming climate and raises concerns about the future of the much larger ice masses that these floating shelves hold back.

Ice shelves, the floating extensions of land-based glaciers, fringe 75% of Antarctica’s coastline and play a crucial role in regulating the flow of ice into the ocean. Their collapse does not directly raise sea levels, as they are already floating, but their removal allows the glaciers they once buttressed to accelerate, which does contribute to sea-level rise. The surprising failure of the Conger-Glenzer shelf, driven by ocean warming and internal fractures, suggests that existing models may underestimate the continent’s potential contribution to rising seas and that new, more complex processes are at play.

A Collapse Decades in the Making

The final break-up of the Conger-Glenzer Ice Shelf happened over just nine days in March 2022, but the stage for its demise was set over a much longer period. Analysis of 25 years of satellite data reveals a multi-stage process of weakening. Unlike the dramatic collapses on the Antarctic Peninsula, such as the Larsen B event in 2002 which was driven by surface melt ponds deepening crevasses, the East Antarctic event had different origins. Researchers found that the primary culprits were ocean melting from below and the steady calving of icebergs, which gradually thinned and weakened the shelf.

The process was not linear. From 2000 to 2012, the ice shelf experienced significant thinning and a retreat of its grounding line, the point where the glacier loses contact with the seabed and begins to float. This was followed by a period of slower change between 2012 and 2019. However, starting in 2019, the thinning escalated, and larger, more complex fractures began to propagate through the ice, signaling its growing instability. The total length of these fractures grew at a rate of 2 kilometers per year between 2002 and 2017, but that rate jumped to 14 kilometers per year after 2017.

The Final Push

While long-term thinning laid the groundwork, the final, rapid collapse was accelerated by a weather event. In March 2022, an atmospheric river—a concentrated plume of moisture—struck the area, bringing strong winds and ocean swells. This storm did not directly cause the collapse, but it acted as the final push on the already critically weakened ice shelf. The combination of pre-existing fractures and the mechanical stress from the storm led to the shelf’s swift disintegration into a field of icebergs.

Scientists were surprised by the event because the Conger shelf was in a region with generally cold air temperatures, where surface melting is not a primary driver of ice loss. The collapse demonstrated that even in the absence of significant surface melt, the infiltration of warmer ocean water into deep fractures can critically weaken an ice shelf from within, making it susceptible to sudden failure. This mechanism, where salty ocean water seeps into cracks, adds a new and worrying dimension to understanding ice shelf vulnerability.

Contrasting East and West Antarctica

Historically, scientific attention has been focused on the West Antarctic Ice Sheet, which has been losing mass at an alarming rate. Ice shelf collapses, beginning with satellite observations in the 1990s, were previously restricted to the Antarctic Peninsula in the western part of the continent. Events like the shattering of the Larsen A ice shelf in 1995 and the much larger Larsen B in 2002, which lost 3,250 square kilometers of ice in just over a month, were clear signs of instability in a rapidly warming region.

A Different Kind of Threat

The West Antarctic collapses were primarily attributed to hydrofracturing, a process where surface meltwater pools in crevasses, deepens them, and eventually wedges the ice apart. The collapse of the Conger-Glenzer shelf demonstrates that the massive East Antarctic Ice Sheet, previously thought to be largely stable, is not immune to climate change, but is vulnerable to different mechanisms. Ocean-driven melting is emerging as a key threat, thinning the ice from below and making it brittle. This is particularly concerning because the East Antarctic Ice Sheet is the largest single mass of ice on Earth, holding enough water to raise global sea levels by an estimated 52 meters (170 feet).

Implications for Sea-Level Rise

The stability of ice shelves is a critical factor in projecting future sea-level rise. When a shelf is lost, the glaciers behind it can accelerate their flow into the sea. Following the Larsen B collapse, for instance, the glaciers that fed it sped up by about 300%. While the glaciers buttressed by the Conger-Glenzer shelf are smaller, the event serves as a warning. The processes that led to its failure—long-term thinning, fracture growth, and ocean water infiltration—could be affecting other, larger ice shelves in East Antarctica.

Researchers note that the rapid changes observed in East Antarctica have not been fully accounted for in models projecting future sea levels, introducing new uncertainty into these critical forecasts. The discovery that an ice shelf thought to be stable could disappear so quickly underscores the need for closer monitoring of all of Antarctica’s ice shelves. The unexpected collapse is a clear signal that the impacts of a warming climate are reaching even the coldest and most remote parts of the planet, with consequences for coastlines worldwide.