Glacial seismic events represent a distinct category of tremors originating in frigid, ice-laden environments. Initially identified in the northern hemisphere over two decades ago, these phenomena occur when substantial ice masses detach from glaciers and descend into the ocean.
Until the present juncture, Antarctic occurrences of this nature were exceptionally scarce.
Within a novel investigation slated for publication in Geophysical Research Letters, I am presenting empirical evidence of hundreds of such seismic occurrences in Antarctica between 2010 and 2023. The majority of these were registered at the oceanic terminus of the Thwaites Glacier – colloquially termed the “Doomsday Glacier” due to its potential to precipitate a swift escalation in global sea levels should it undergo catastrophic failure.
The extent of global sea ice cover is more than 3 million square kilometers below the 1981-2010 average. This is the 2nd lowest on record for this date over the satellite-era.
Data from nsidc.org/data/seaice_…
— Zack Labe (@zacklabe.com) Nov 30, 2025 at 1:50 AM
A recent discovery
A glacial earthquake is precipitated by the detachment of towering, attenuated icebergs from the extremity of a glacier into the marine environment.
Upon inversion, these icebergs engage in tumultuous collisions with their parent glacier. This impact engenders potent mechanical ground disturbances, commonly referred to as seismic waves, which propagate over considerable distances from their point of origin.
The distinguishing characteristic of glacial earthquakes is their incapacity to generate seismic waves in the high-frequency spectrum. These particular waves are instrumental in the identification and pinpointing of conventional seismic sources, including terrestrial earthquakes, volcanic eruptions, and nuclear detonations.
Owing to this fundamental divergence, glacial earthquakes were ascertained only in relatively recent times, despite the fact that other seismic phenomena have been systematically cataloged for several decades.
Varying with the seasons
The majority of glacial seismic events recorded to date have been localized in proximity to the termini of glaciers in Greenland, the most extensive ice mass in the northern hemisphere.
These Greenlandic glacial earthquakes are characterized by a significant magnitude. The most substantial among them are comparable in intensity to seismic disturbances caused by nuclear tests conducted by North Korea in recent decades. Consequently, they have been detected by a high-fidelity, perpetually operating global seismic monitoring infrastructure.
The Greenlandic occurrences exhibit seasonal variability, with a higher frequency observed in the latter part of summer. Furthermore, their occurrence has become more prevalent in recent decades, potentially correlated with an accelerated rate of global warming in polar regions.
Average temperature departures by month in the #Antarctic since the year 1940.
Data from @copernicusecmwf.bsky.social ERA5 reanalysis.
— Zack Labe (@zacklabe.com) Nov 12, 2025 at 10:57 AM
Elusive evidence
Despite Antarctica being the largest ice sheet globally, direct corroboration of glacial seismic events attributable to capsizing icebergs in this region has remained elusive. Previous endeavors to detect Antarctic glacial earthquakes predominantly relied on the global seismic detection network.
However, if Antarctic glacial earthquakes are of a significantly lower magnitude compared to their Greenlandic counterparts, the international network might fail to register them.
In my recent research, I employed seismic stations situated within Antarctica itself to scrutinize for indications of these tremors. My investigation yielded the identification of over 360 glacial seismic events, the majority of which are not presently incorporated into any earthquake catalog.
The registered events were concentrated in two distinct clusters, in the vicinity of the Thwaites and Pine Island glaciers. These particular glaciers have been the principal contributors to sea-level rise emanating from the Antarctic continent.
Earthquakes at the Doomsday Glacier
The Thwaites Glacier is occasionally referred to as the Doomsday Glacier. Its complete disintegration could lead to a rise in global sea levels of up to 3 meters, and it possesses the inherent capacity for rapid fragmentation.
Approximately two-thirds of the identified events – specifically, 245 out of 362 – were localized near the marine boundary of the Thwaites Glacier. The prevailing hypothesis is that most of these events are glacial earthquakes resulting from the inversion of icebergs.
The primary impetus for such occurrences does not appear to be the annual fluctuation of warm air temperatures that governs the seasonal behavior of Greenland’s glacial earthquakes.
Conversely, the period exhibiting the highest incidence of glacial earthquakes at Thwaites, spanning from 2018 to 2020, correlates with a phase of accelerated movement of the glacier’s ice tongue towards the sea. This acceleration was independently substantiated through satellite-based observations.
This accelerated flow may have been instigated by oceanic conditions, an effect whose ramifications are not yet fully comprehended.
The research findings indicate a demonstrable short-term influence of oceanic states on the stability of marine-terminating glaciers. This warrants further investigation to ascertain the glacier’s potential contribution to future sea-level elevation.
The secondary cluster of detections was registered in proximity to the Pine Island Glacier. However, these events were consistently situated 60–80 kilometers distant from the ice edge, rendering them unlikely to have been triggered by capsizing icebergs.
These events remain enigmatic and necessitate subsequent research endeavors.
What’s next for Antarctic glacial earthquake research
The identification of glacial seismic events linked to iceberg calving at the Thwaites Glacier could contribute to resolving several critical research inquiries. Among these is a fundamental question regarding the potential instability of the Thwaites Glacier, stemming from the complex interplay between oceanic forces, ice dynamics, and the underlying solid ground at its marine interface.
An enhanced comprehension of these processes may prove pivotal in mitigating the current substantial uncertainties surrounding projected sea-level rise over the ensuing centuries.
