Reveal that Antarctica undergoes thousands of small tremors each night – 19/03/2019

Little incessant tremors shake the ice floe of Antarctica every nightwhen the ice regains its shape after melting during the day.

In a recent study, scientists at the University of Chicago placed seismometers on the McMurdo ice sheet and recorded thousands of small "ice tremors" They appear to be caused by puddles of partially melted ice that dilate and freeze at night. The phenomenon can help scientists to trace the melting glaciers and help explain the disintegration of large pack ice.

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"In these areas, we have recorded tens, hundreds, if not thousands of them at night," said co-author Douglas MacAyeal, renowned geophysics professor and glaciologist traveling to Antarctica to study behavior. of the study, in a statement. ice and snow for decades. "Seismometers may be a convenient way for us to remotely monitor the melting of the glacier."

The climate change melts Antarctica, but glaciologists still map how, where and why. We still do not fully understand this process, as evidenced by the mbadive collapse of the Larsen B ice sheet in 2002, which surprised glaciologists, and the understanding of these mechanisms is essential to predict the future of ice .

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MacAyeal and the team were interested in the role of "earthquakes" on floating ice platforms and the role they could play in melting and disintegrating ice.

The team installed seismometers for 60 days during the melt season at two locations near seasonal meltwater lakes on the McMurdo ice floe. One was drier; the other was softer, with puddles of melted water that were again frozen. They found that the wettest area was full of seismic activity during the night.

"In these ponds, there is often a layer of ice above the melted water below, like in a frozen lake at the top," MacAyeal explained. "As the temperature cools at night, the ice on the top decreases and the water below expands when it freezes. until he finally breaks himself with a snap"

The energy vibrates towards the environment, where it is captured by seismometers. Some cracks are closing, others not, said MacAyeal..

This may explain why icebergs break down more often in cold weather. "Maybe it's happening on longer and slower scales," MacAyeal said.

This discovery adds an important element to our understanding of the physics and processes around melting ponds on ice, especially if it can help researchers track remote Antarctic melting. "It can be very useful to add this to our other ways of monitoring the ice," MacAyeal said.

Source: DPA

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