Greenland's largest ice stream flows under the effect of small earthquakes ❄️

An international team, involving scientists from CNRS Earth & Universe, has uncovered a previously unknown phenomenon in the dynamics of ice streams.

Contrary to the hypothesis that these gigantic rivers of ice flow slowly and continuously, scientists have discovered that they also advance in jerks due to micro-earthquakes. This discovery, made possible by a fiber-optic cable inserted into a 8,743-foot-deep (2,665 meters) borehole located on the Northeast Greenland Ice Stream, could revolutionize sea-level rise prediction models.


Greenland and Antarctica's ice streams play a key role in transporting ice from polar ice sheets to the ocean. Their flow speed directly influences sea-level rise, making their understanding essential for anticipating the effects of global warming. Until now, numerical models assuming slow and continuous flow failed to explain certain satellite observations. The study reveals that ice streams do not flow solely like a viscous fluid but also deform through a jerky process, akin to crackling.

Using an innovative distributed acoustic sensing technology, scientists detected micro-earthquakes triggering one another and propagating several hundred meters deep. These mini ice quakes could explain the discrepancies observed between theoretical models and reality. The idea that these streams flow only like viscous honey is outdated. These new findings will refine sea-level predictions by incorporating this seismic dynamic.

For several decades, fractures between ice crystals have been observed in deep ice cores without precise explanation. These micro-earthquakes finally shed light on their origin: they fracture the ice and influence its flow. Scientists also identified a surprising factor: micro-earthquakes originate from volcanic impurities present in the ice. These impurities, carried by winds to Greenland and deposited as snow, appear to play a role in micro-earthquake formation by weakening the ice structure.

Cutting-edge technology: a 8,743-foot (2,665 meters) ice borehole

This discovery was made possible by installing a fiber-optic cable in a borehole located on the Northeast Greenland Ice Stream, which drains 12% of the ice sheet. Using ultra-sensitive seismic sensors, researchers recorded these signals up to 4,921 feet (1,500 meters) deep for 14 hours, paving the way for a new era in glacier studies.

Scientists' observations suggest these micro-earthquakes may occur continuously in all ice streams, playing a significant role in their flow dynamics. However, verifying this will require similar seismic measurements in other boreholes.