Hundreds of Hidden Earthquakes Detected Near Thwaites Glacier

Hundreds of previously undetected seismic events have been identified beneath Antarctica, with 245 occurring near the marine edge of the Thwaites Glacier. Many of these events appear to be glacial earthquakes. These quakes happen when large icebergs break off, capsize, and collide with the glacier.

The surge in seismic activity coincided with a period when the Thwaites Glacier was flowing faster toward the ocean. This suggests that changing ocean conditions may be destabilizing the ice. Glacial earthquakes are a distinct type of seismic event generated in cold, icy regions.

These quakes occur when tall, thin icebergs detach from a glacier and fall into the sea. When these icebergs capsize, they violently clash with the parent glacier. This collision generates strong mechanical ground vibrations, or seismic waves, that travel thousands of kilometers from their origin.

Unlike typical earthquakes, glacial earthquakes do not produce high-frequency seismic waves. These waves are crucial for detecting and locating standard seismic sources like tectonic earthquakes, volcanoes, and nuclear explosions. This difference explains why glacial earthquakes were only recently discovered, despite decades of routine documentation for other seismic sources.

Most previously detected glacial earthquakes have been near the ends of glaciers in Greenland. Greenland's glacial earthquakes are relatively large in magnitude. The largest ones are comparable in size to those caused by nuclear tests. They have been detected by a global network of seismic monitors. These events show seasonal variations, occurring more frequently in late summer. Their increasing frequency in recent decades may be linked to accelerated global warming in polar regions.

Antarctica is the Earth's largest ice sheet, but direct evidence of glacial earthquakes caused by capsizing icebergs has been scarce. Previous attempts to detect Antarctic glacial earthquakes used the worldwide seismic network. However, if Antarctic glacial earthquakes are smaller than those in Greenland, the global network might not detect them. A new study used seismic stations within Antarctica to find over 360 glacier seismic events, most not yet cataloged. Two clusters of events were found near the Thwaites and Pine Island glaciers. These glaciers are the largest contributors to sea-level rise from Antarctica.