Greenland is melting faster than models predicted, and scientists have just discovered why. Deep drilling reveals tiny signals buried under centuries of ice. What researchers have found there is shaking up our understanding of glacier movement.
by Laurie Henry
Cover photo: Science camp set up on the northeast Greenland ice flow (NEGIS), around 400 kilometres from the coast. © Lukasz Larsson Warzecha / LWimages
Greenland’s glaciers are among the main contributors to the rise of the oceans. Their behaviour is crucial to climate forecasting. Until now, glaciological models have been based on the idea that rivers of ice flow slowly and continuously, like a viscous fluid, and that their movements are homogeneous, under the effect of gravity and the internal pressure gradient. Until now, these assumptions have enabled the dynamics of the polar ice caps to be simulated relatively reliably. But this simplified vision is no longer sufficient to explain recent observations. An international team, coordinated by the Swiss Federal Institute of Technology Zurich (ETH Zurich) in collaboration with theAlfred Wegener Institute, the french CNRS and theUniversity of Strasbourg, has just revealed an unexpected mechanism: internal micro-earthquakes that accelerate the melting of glaciers.
The ice river in north-east Greenland (NEGIS), the largest on the island, has therefore proved to be more complex than expected. Its flow speed, measured by satellite, shows irregularities that conventional models were unable to explain. To probe this anomaly, the researchers observed the ice not only at the surface, but also at great depths. To do this, they used an innovative technique.