Sunday , June 13 2021

Melting water causes Antarctic ice to twist: scientists – Xinhua

CHICAGO, Feb. 13 (Xinhua) – A team of scientists from the University of Chicago (UChicago) and the Cooperative Institute for Environmental Sciences Research for the first time directly observed the folding of an Antarctic ice shelf under the weight of the melting water head, a phenomenon that may have led to the historic ice shelf collapse of Larsen B in 2002.

Researchers surveyed the data and noticed that in the months preceding the collapse, the icy shelf was dotted with more than 2,000 melting lakes, according to a message posted on the UChicago website on Wednesday.

During the melting season, lakes can form on the surface of ice shelves, combining the weight of melting snow and ice in many areas of liquid water. These lakes can weigh 50,000 to 2 million tons each, and this pushes down the ice, creating an escape. If the pond is drained, this backfill is reversed. If the resulting stress is high enough, the ice around the lake is weakening and may begin to break, researchers predicted.

To estimate how many lakes have distorted floating Antarctic ice, researchers are exploring for the first time where the lakes will develop. They identified four ponds to provide GPS sensors.

In November 2016, before the start of the melting season, the researchers had access to McMurdo's ice shelf. At each of the four lakes, they installed independent instruments that measured the vertical height and depth of the lake, each of which was fixed to a metal pole drilled more than 6 feet deep into the ice. Three months later they flew back to take out the tools.

The researchers found that in the center of each lake, the ice shelf moved down and then upward by about 3 to 4 feet in response to each filling the pond and then draining.

Climate models predict that over the next few decades there will be more melting of more ice shelves, resulting in an increase in the number of melting lakes.

"These observations are important because they help us better understand the start-up mechanisms for the collapse of the ice shelf, which leads to a rise in sea level," said Alison Banuell, a visiting doctoral student at CIRES and the lead author of the study. "Our results can be used to improve the models to better predict which ice shelves are more vulnerable and are the most susceptible to collapse."

The study was published on Wednesday in Nature Communications.

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