Hundreds of iceberg earthquakes have occurred in Antarctica

Glacial earthquakes are a special type of seismic events that occur in the cold polar regions, which occur when a block of ice breaks off from the edge of a glacier and falls into the ocean. Such earthquakes were first detected more than 20 years ago in the Northern Hemisphere, but only isolated cases were recorded in Antarctica until recently. This was reported on December 14 by Science X magazine.

A new study presents data on hundreds of glacial earthquakes recorded in Antarctica between 2010 and 2023. Most of them occurred at the sea edge of the Thwaites Glacier, the so—called "Doomsday glacier", the destruction of which can lead to a sharp rise in sea levels.

A glacial earthquake occurs when a tall and narrow iceberg breaks off from a glacier and, turning over, violently collides with the "mother" ice mass. This impact creates powerful mechanical vibrations of the ground — seismic waves capable of propagating for thousands of kilometers.

The peculiarity of such earthquakes is that they do not generate high-frequency seismic waves, which play an important role in detecting and accurately locating common earthquakes, volcanic activity, or nuclear tests. That is why glacial earthquakes were detected relatively late, despite decades of seismic observations.

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Until now, most of the known glacial earthquakes have been recorded at the ends of Greenland's glaciers. There, these events are characterized by a relatively high magnitude: the most powerful of them are comparable in strength to seismic signals from nuclear tests conducted in recent decades. Due to this, they are easily recorded by a global network of seismic stations.

In Greenland, such earthquakes have a pronounced seasonality and occur more often in late summer. In addition, their frequency has increased in recent decades, which is attributed to accelerating warming in the polar regions.

In Antarctica, direct evidence of glacial earthquakes remained elusive for a long time. Previous detection attempts relied mainly on a global network of seismic sensors, which may not have detected the weaker signals characteristic of Antarctic events.

The new study used data from seismic stations located directly in Antarctica. This made it possible to identify more than 360 glacial seismic events, most of which had not previously been included in any earthquake catalog. The detected signals form two main clusters — in the areas of the Thwaites and Pine Island glaciers. It is these glaciers that have been making the greatest contribution to sea level rise in recent years due to the melting of the Antarctic ice sheet.

On December 1, Science Daily magazine reported on the rapid weakening of the Thwaites Glacier. According to the study, a four-stage sequence of shelf weakening was recorded. According to experts, long cracks appeared first along the direction of movement of the ice, and then short, transverse ones. As specified, this configuration provoked increased destruction due to the acceleration of the flow, and after the destruction, a new acceleration occurred.

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