A new search through Antarctic seismic records found far more activity near Thwaites Glacier than standard earthquake catalogs had shown. Of 362 glacier-related events identified between 2010 and 2023, 245 clustered near the glacier’s ocean-facing end. Their unusual seismic character helps explain why so many passed unnoticed.
Why Glacial Earthquakes Hide in Seismic Records
A conventional earthquake sends out a range of vibrations that includes high-frequency energy used to locate many familiar seismic sources. Glacial earthquakes are different. They can be produced when tall pieces of ice break from a glacier, topple in the water, and strike the ice front, generating strong low-frequency motion without the high-frequency signature detection systems often expect.
The reported analysis used seismic stations in Antarctica rather than relying only on the worldwide monitoring network. That closer view uncovered more than 360 events, most absent from existing earthquake catalogs. The missing catalog entries therefore reflected a detection problem, not proof that the ice had been quiet.
Two Clusters Appeared Around Thwaites and Pine Island
The events were concentrated near two fast-changing West Antarctic glaciers. Thwaites accounted for about two-thirds of the total, with 245 detections near its marine edge. Most of those signals were consistent with the violent motion of capsizing icebergs during calving, placing the seismic sources where floating ice separates from the glacier.
A second cluster appeared near Pine Island Glacier, but its locations were different. Those events sat roughly 60 to 80 kilometers inland from the waterfront, making an iceberg-capsize explanation less convincing. The contrast shows that a similar-looking seismic signal can point to different ice processes depending on where it originates.
The Busy Period Matched Faster Ice-Tongue Flow
Thwaites produced its densest run of glacial earthquakes between 2018 and 2020. Independent satellite observations showed that the glacier’s ice tongue was also moving toward the sea more rapidly during that interval. The timing creates a connection worth investigating, although it does not by itself establish what caused either change.
The pattern also differed from the strong late-summer cycle documented for many Greenland glacial earthquakes. At Thwaites, annual changes in warm air temperature did not appear to be the main driver. Researchers instead pointed to possible ocean influences, a mechanism that remains incompletely understood and requires observations of water, ice, and the bed together.
What Iceberg Impacts Can Reveal About a Glacier
A glacial earthquake records a physical event at the ice front. Counting such events can provide a second view of calving behavior alongside satellite images, especially when clouds, darkness, or the timing between images complicates visual monitoring. Seismic stations can continue listening while the glacier changes in ways that may be brief or hard to see from orbit.
The events are not a direct gauge of future sea-level rise. A count of 245 does not translate into a specific amount of lost ice, and the newly found signals span many years. Their value lies in identifying when and where forceful calving-related motion occurred, then comparing that history with ice speed and ocean conditions.
Thwaites Is a High-Stakes Place to Improve Detection
Thwaites is often called the Doomsday Glacier because a major collapse would have global consequences, but the nickname can obscure the narrower result. The new work does not announce a collapse. It reveals a previously undercounted class of seismic activity near the part of the glacier where ice, ocean, and solid ground interact.
That boundary is difficult to observe and central to understanding stability. The dense cluster near the marine edge suggests that local seismic monitoring can recover information missed by global catalogs. The unexplained inland Pine Island cluster further shows that the method may expose processes that do not fit the first interpretation.
The Next Step Is to Join Seismic and Ocean Records
A stronger explanation would align event times and locations with satellite measurements of flow, records of calving, and observations of nearby ocean conditions. That comparison could test whether bursts of glacial earthquakes consistently accompany faster motion or particular water states. It could also separate capsizing events from other sources of vibration within the ice.
The 245 hidden quakes matter because they convert apparent silence into a measurable history. They do not settle the future of Thwaites, but they expand the evidence available for studying short-term instability at its marine edge. In a remote region where no single instrument provides a complete view, that added record is a substantial gain.
The detection window from 2010 through 2023 also makes the catalog useful for retrospective comparisons. Satellite records can be revisited at the exact times of the seismic events to look for calving, iceberg rotation, or changes in ice-front geometry. That pairing can test the proposed capsizing mechanism event by event rather than relying only on the overall cluster.
Better event locations would sharpen the Pine Island puzzle as well. If the inland signals repeatedly align with a particular fracture zone or moving boundary, the geometry could point toward a different source process. If locations scatter as station coverage changes, part of the mystery may come from uncertainty in the seismic solution itself.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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