Scientists have detected hundreds of previously unknown “iceberg earthquakes” near Antarctica’s Thwaites Glacier, raising new concerns about the stability of one of the world’s most vulnerable ice systems. The findings suggest that rapid ice loss and changing ocean conditions are triggering seismic activity at the ocean-facing edge of the glacier, often referred to as the “Doomsday Glacier” because of its potential impact on global sea levels.
The research, soon to be published in Geophysical Research Letters reports that more than 360 glacial earthquakes were recorded in Antarctica between 2010 and 2023, most of them clustered around the Thwaites and Pine Island glaciers in West Antarctica.
What are glacial or iceberg earthquakes?
Glacial earthquakes are a rare type of seismic event that occur when massive icebergs break away from the end of a glacier and topple into the ocean. As these tall, narrow icebergs capsize, they collide violently with the main glacier, generating powerful ground vibrations that can travel thousands of kilometres.
Unlike conventional earthquakes caused by shifting tectonic plates, glacial earthquakes do not produce high-frequency seismic waves. This makes them difficult to detect using traditional global monitoring systems and explains why they were discovered only in the last two decades, despite glaciers calving ice for centuries.
Why Antarctica’s glacial earthquakes went unnoticed for so long
Most known glacial earthquakes have been detected near Greenland, where they tend to be large enough to register on global seismic networks. Some Greenland events have been strong enough to rival seismic signals from underground nuclear tests.
In Antarctica, however, similar events appear to be weaker. Because earlier studies relied mainly on global seismic networks, many Antarctic glacial earthquakes went undetected. The new study instead used seismic stations located on the continent itself, allowing researchers to identify smaller and more localised signals.
This approach revealed clusters of previously undocumented seismic events near Thwaites and Pine Island glaciers, both of which are major contributors to sea-level rise from Antarctica.
Thwaites Glacier emerges as the main hotspot
The majority of detected events occurred near the marine edge of Thwaites Glacier. Out of 362 total seismic detections, 245 were located close to where the glacier meets the ocean, strongly indicating that they were caused by capsizing icebergs.
Thwaites Glacier is considered especially dangerous because a complete collapse could raise global sea levels by around three metres. Scientists also fear that parts of the glacier could destabilise rapidly once critical thresholds are crossed.
Interestingly, unlike Greenland’s glacial earthquakes, which peak during warmer summer months, the seismic activity at Thwaites did not follow a clear seasonal pattern.
Ocean conditions may be driving the seismic activity
The most intense period of glacial earthquakes near Thwaites occurred between 2018 and 2020. This coincided with a phase when the glacier’s floating ice tongue accelerated towards the sea, a change independently confirmed through satellite observations.
Researchers believe ocean conditions may have played a key role in triggering this speed-up, although the exact mechanisms remain unclear. Warmer ocean water can weaken ice shelves from below, making them more prone to cracking, calving and sudden movement.
The findings suggest that short-term changes in ocean state can strongly influence the stability of marine-terminating glaciers, with implications for future sea-level rise.
Puzzling signals near Pine Island Glacier
A second cluster of seismic events was detected near Pine Island Glacier, another rapidly thinning ice system. However, these events occurred 60 to 80 kilometres inland from the glacier’s ocean edge, making iceberg capsizing an unlikely cause.
Scientists say these signals remain unexplained and will require further investigation. They could point to different ice dynamics occurring beneath the surface, possibly involving interactions between ice, bedrock and subglacial water.
Why these discoveries matter for sea-level rise projections
Understanding glacial earthquakes could help scientists better monitor how fast glaciers are changing and how close they may be to instability. Because these seismic signals are linked to iceberg calving and ice flow acceleration, they offer a new tool for tracking glacier health in remote polar regions.
Researchers say improved detection and analysis of Antarctic glacial earthquakes could reduce uncertainty in long-term sea-level rise projections, which currently vary widely for the coming centuries.
As climate change continues to warm both the atmosphere and oceans, scientists warn that glaciers like Thwaites may respond in sudden and unpredictable ways, making close monitoring more urgent than ever.