2021-10-25

Melting of ice mixture: studies say the cold “glue” may control the rate of rupture of the Antarctic ice shelf

By yqqlm yqqlm

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c67fc3dcbdaa9e1 - Melting of ice mixture: studies say the cold "glue" may control the rate of rupture of the Antarctic ice shelf

this finding shows that, The ice mixture – a mixture of iceberg fragments and sea ice in and around ice shelves – is crucial to holding ice shelves together, which means that these ice shelves may rupture faster than scientists expected due to rising temperatures

the ice shelf is the “floating tongue” of glaciers extending to the ocean, which slows down the contribution of glaciers in Antarctica to the rise of global sea level. When the ice shelf of a glacier flows over the Southern Ocean, it will eventually get stuck on an island, submarine ridge or bay wall surrounding the glacier. The ice shelf slowed down the advance of the glacier. But in recent decades, the ice shelf of the Antarctic Peninsula has been moving and disintegrating faster. If this process continues until enough ice shelves break (such as Larsen B in 2002), the glaciers blocked by the ice shelves begin to flow more rapidly from land to sea. This increases the rate of sea level rise

climate warming is the root cause of this change in ice shelf behavior, because it increases the temperature of the air above the glacier and the sea water below the glacier. However, the way ice shelves respond to climate warming is not fully understood. Scientists believe that the freezing and thawing cycle of melting water on ice is expanding the cracks. But if so, how can Larsen c release its huge iceberg in winter

to answer this question, researchers at JPL and the University of California at Irvine focused on the ice mixture. This chaotic, massive mixture has natural properties similar to glue or grout, which can fill cracks or crevices and stick to ice and rock. When it accumulates in the cracks of the ice shelf, it forms a thin layer as hard as the surrounding ice to fix the cracks together. On both sides of the ice shelf, layers of ice mixture bind the ice to the surrounding rock walls. Eric Rignot, a professor at the University of California Irvine and co-author of the study, said: “we have always suspected that this mixture plays a key role, but only recently have we observed its characteristics well.” the study was published in the proceedings of the National Academy of Sciences

researchers modeled the entire Larsen C ice shelf using NASA’s ice and sea level system models, as well as observation data from NASA’s ice bridge operation and European and NASA satellites. They first evaluated which of the hundreds of cracks on the ice shelf were most likely to break, and selected 11 cracks for in-depth analysis. They simulated what would happen if only the ice shelf thinned due to melting, if only the ice mixture thinned, and if both thinned

“many people intuitively think that if you make the ice shelf thinner, you will make it more fragile and it will break,” explained Eric larour, a JPL scientist and lead author of the new study. On the contrary, the model shows that simply thinning the ice shelf without changing the ice mixture actually closes the cracks, and the average widening rate per year decreases from 259 feet to 72 feet (79 meters to 22 meters). At the same time, the thinning ice shelf and cement also closed the cracks. Therefore, the melting of glaciers alone does not explain why ice shelves break faster

however, when researchers only thinned the mixing layer in the model without reducing the thickness of the glacier ice itself, the cracks on the ice shelf expanded faster, accelerating from an average of 249 feet to 367 feet (76 meters to 112 meters) per year. When the narrow mixing layer thins to about 30 to 50 feet (about 10 or 15 meters), they completely lose the ability to fix the cracks together. Cracks can expand rapidly and large icebergs will loosen – as happened on Larsen C

why is this important? “We have pointed out a physical process that can destroy the stability of the ice shelf before the atmosphere warms significantly,” larour said. However, these narrow hybrid layers melt mainly through contact with the seawater below, which continues throughout the year. At any time of the year, they may become too thin to continue to hold the ice shelves together

“we think this process may explain why the ice shelf of the Antarctic Peninsula began to rupture decades before melting water began to accumulate on its surface area,” Rignot said. “This means that the Antarctic ice shelf may be more vulnerable to climate warming – and earlier than previously thought.”