It is twice the size of Manhattan!
It looks like Antarctica is going to be shedding some extra pounds. A floating shelf of ice attached to the coast of Antarctica is about to break off into the Southern Ocean. Over the course of two years, a 50-kilometer (31-mile) crack formed across most of the Nansen Ice Shelf, prompting concerns that it might soon break off, producing an iceberg twice the size of Manhattan!
The Operational Land Imager (OLI) on the Landsat 8 satellite acquired the first image below on December 26, 2013, while the second one was taken on December 16, 2015.
December 26, 2013. Photo credit: NASA Earth Observatory
December 16, 2015. Photo credit: NASA Earth Observatory
At the end of 2015, NASA scientists Christina Dow and Ryan Walker visited the ice shelf to install GPS stations which are used to track how the glacier is affected by ocean tides. However, when they were flying over the area, they noticed that the crack had become substantially bigger.
“There’s a huge crack, miles long and sometimes over a hundred yards wide, which runs more or less parallel to the front of the ice shelf,” Walker wrote in a blog post. “Over the winter, the sea surface freezes and traps small icebergs in the crack, producing a fascinatingly broken icescape.”
At the beginning of March, satellite imagery showed that the ice shelf was still attached to Antarctica, and since the region is now entering it’s winter, the shelf stands a good chance of holding on. However, ice shelves can still break away no matter the weather or temperature.
“Even in winter, strong winds can prevent the water beyond the shelf from freezing, so it is unclear whether the front will separate soon or hang on like a loose tooth,” writes NASA's Earth Observatory in a press release.
So what causes ice shelves to break off? Scientists still have a lot to learn, but it is a natural process and it is not always a result of climate change — ocean currents and tides play a role as well. However, the rate of ice shelf loss has been getting faster. In fact, over the past 20 years, Antarctica’s Larsen Ice Shelves have lost 75 percent of their area.
These giant icebergs not only pose threats to boats, but also marine life — such as the 150,00 penguins that died earlier this year when a giant iceberg blocked their path to sea, cutting off their food supply.
Luckily, these ice shelves do not result in sea level rise just by breaking off since they are already giant floating pieces of ice that just happen to be attached to land. Unfortunately, losing an ice shelf means that the ice loss from the center of the continent is increased, which does contribute to sea level rise.
Researchers will continue to monitor the crack, as well as try to understand how it formed in the first place.
“I’m really interested to see whether this feature is occurring because of the topography around the ice shelf, or whether it was initially created by surface water flowing into a small ice surface crack,” said Dow in the press release. “We’re planning an intensive survey of this feature in the coming years and will hopefully get a handle on the causes.”
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