The Earth's surface typically creeps at a pace we can barely perceive. Tectonic plates expand at speeds similar to the growth of fingernails; Mountains climb over eons. And glaciers slide rate Even snails will make fun.
Sometimes, nature can surprise us. A new study of Ross Ice Shelf In Antarctica, it revealed elastic waves pushing the entire layer forward once or twice a day.
Considering this is the largest shelf in Antarctica, roughly the size of France, we're talking a lot of movement. Knowing how and why this happens is important in terms of monitoring Antarctica amid ongoing climate change.
The research team behind the discovery, from multiple institutions across the United States, says it was triggered by movement Whillans Glacier Streama belt of fast-flowing ice in the West Antarctic Ice Sheet that moves faster than its surrounding areas.
“We found that the entire shelf suddenly moved by about 6 to 8 centimetres [2.4 to 3.1 inches] Once or twice a day, due to a sliding ice stream that flows onto the ice shelf.” He says Geophysicist Doug Wiens of Washington University in St. Louis.
“These sudden movements likely play a role in triggering icequakes and fractures in the ice shelf.”
Loss of water under a river can make it “more viscous,” causing sudden jumps in movement. Instead of flowing at a reasonably constant speed, much of the Whillans Ice Stream stops, then suddenly accelerates forward.
The study is based on measurements made by Seismographs Which was embedded in ice in 2014.
Movements of up to 40 centimeters can occur in the ice stream in just minutes, with each movement putting pressure on the Ross Ice Shelf. These tremors are known as slip events, and they are not unlike movements along fault lines before earthquakes: stress builds up as the ice moves at different speeds through the stream, and then the stress is released.
“One cannot detect movement simply by feeling it.” He says Wins. “Motion occurs over a period of time of up to several minutes, so it cannot be perceived without the devices.”
“That is why the movement has not been detected yet.”
While researchers do not believe that ice stream sliding events are a direct result of human-induced global warming, they are important in terms of the long-term stability of the Ross Ice Shelf. These shelves extending across the ocean act as natural boundaries for glaciers and streams on land, slowing the rate of melting and increasing ice accumulation.
If the Ross Ice Shelf begins to push faster out to sea and eventually breaks up, that would have consequences for the ice sheet across the region. We know that melting glaciers are already contributing to sea level rise, and the research team will be monitoring the Ross Ice Shelf carefully in the coming years.
“At this point, earthquakes and fractures are just part of the normal life of the ice shelf.” He says Wins.
“There is concern that the Ross Ice Shelf will break up one day, as other smaller, thinner ice shelves have done so.”
The research was published in Geophysical Research Letters.
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