Huge icebergs are about to leave the Song Dao Glacier in Antarctica.

Satellite images show the Song Dao Glacier on September 17, 2065438 and October 1 2065438. The OLI images of Landsat processed by Steflhermette/Delft University of Technology show that a newly discovered long and rugged rift is cracking on the Song Dao Glacier in western Antarctica.

Steffler Mitte, an assistant professor in the Department of Earth Science and Remote Sensing at Delft University of Technology in the Netherlands, said that the rift nearly 19 miles (30 kilometers) long began in the middle of the ice shelf, when the ice shelf was in contact with warm seawater melting from below.

Lemit said that before one or more icebergs broke, the rift valley was only 6 miles (65,438+00 kilometers) away from the glacier. Another similar event occurred a year ago in 20 17, when an iceberg 4.5 times the size of Manhattan broke away from the Song Dao Glacier. [Photo Gallery. Glacier cracks in Song Dao, Antarctica]

The coming Song Dao glacier covers an area of about 1 15 square miles (300 square kilometers). (Landsat OLI images are processed by Stef Lhermitte/ Delft University of Technology) Lhermitte discovered new cracks by analyzing satellite images of glaciers, and he received these images in his email inbox every day. "It was Wednesday night (65438+10.3), and I suddenly saw something I didn't see the day before. He told Life Science,

If the iceberg is connected and disconnected, its area will be as high as 1 15 square miles (300 square kilometers), even larger than the iceberg that was disconnected last year. (The iceberg area of 20 17 is 103 square miles, which is 267 square kilometers. )

Lhermite pointed out that if the final iceberg is big enough, it will get a name. However, regardless of whether the crack leads to one or more icebergs, it will be the sixth major disintegration event of Song Dao glacier since 200 1, he said.

Of course, it is natural for glaciers to break up icebergs. However, the problem with Song Dao Glacier is that it breaks down icebergs more frequently than before. Flamel said that Song Dao Glacier gave birth to icebergs in 200 1 1, 2007 1 1, 20 1 65438+2, and in 2066.

The red line shows the location of iceberg fracture of Song Dao Glacier in 20 17. The blue line shows the newly discovered rift valley. (Landsat OLI image processed by Stefflemette/Delft University of Technology) The coming iceberg is not loose. "But in fact, the rift valley spans almost the whole glacier, and it may happen faster," said Lhermitte.

However, it is challenging to say the meaning of "soon". According to Lhermitte, calving may happen within weeks or months, "but it may not take years," he said. I expect this will happen sometime between now and this year's Antarctic summer.

Once a fracture occurs, if the iceberg floats with Antarctic sea ice, it is likely to remain frozen. However, if the ocean current carries it farther north, the iceberg will melt in warm sea water, Lemit said.

Song Dao Glacier is one of the fastest glaciers in Antarctica. According to a report last year, it will lose 45 billion tons (40.8 billion tons) of ice every year, which will cause the sea level to rise by 0.03 inch (1 mm) every eight years. If the whole glacier melts, the sea level will rise by 1.7 feet (0.5 meters).

This video, which lasted from 2002 to 20 16, describes how much ice the glaciers in Song Dao are losing. (In the video, yellow, orange, red and black represent the loss of ice, and blue represents the increase of ice. )

Lhermite said that ice shelves are important because they prevent glaciers from all flowing into the sea, just like dirt blocking the sink and slowing down water loss. Lhermitte wrote on Twitter that once the upcoming disintegration event occurs, Songdo Glacier will retreat by nearly 4 miles (6 kilometers). As for the reason of Songdao glacier,

It's hard to say that ier is losing more ice shelves (not touching bedrock, but extending to the frozen part of the ocean). Lhermitte said that the warm water that melted the ice shelf from below was pushed up from the deep sea.

"The reason why we get this rising warm water is of course related to the climate, but it is hard to say whether it is related to climate change," he said. Antarctica is a continent that is very sensitive to climate change. But for this iceberg, it is impossible to infer.

Originally published in the journal Life Science.