NASA releases stunning images of gigantic iceberg

16 November 2017

US space agency NASA has published a series of stunning images showing an Antarctic iceberg the size of Delaware, giving a close-up glimpse of a vast body of ice previously shown only in satellite images.

Scientists have captured close-up images of the behemoth iceberg that in July detached from one of the largest floating ice shelves in Antarctica (See: Giant Antarctic ice split unveils ecosystem hidden for millennia).

As part of Operation Icebridge, NASA's continuing mission to map polar ice, the agency took sophisticated airborne shots of the Larsen C ice shelf and the enormous iceberg that broke free from it, known as A-68.

''I was aware that I would be seeing an iceberg the size of Delaware, but I wasn't prepared for how that would look from the air,'' wrote NASA Earth Observatory's Kathryn Hansen in a blog about the 12 November mission.

''Most icebergs I have seen appear relatively small and blocky, and the entire part of the berg that rises above the ocean surface is visible at once,'' she said.

''Not this berg. A-68 is so expansive it appears [as] if it were still part of the ice shelf. But if you look far into the distance you can see a thin line of water between the iceberg and where the new front of the shelf begins.

''A small part of the flight today took us down the front of iceberg A-68, its towering edge reflecting in the dark Weddell Sea.''

The images, posted on NASA's website and on social media, show the vast expanse of ice making up A-68, as well as the gap separating it from the ice shelf.

The iceberg is one of the largest in recorded history to split off from Antarctica, consisting of almost four times as much ice as the melting ice sheet of Greenland loses in a year.

''I was shocked, because we flew over the iceberg itself and it looks like it's still part of the ice shelf, in terms of how large it is and the surface texture,'' said Nathan Kurtz, a scientist with Operation Icebridge, which travelled to Antarctica near the end of October to get a closer look at the iceberg.

''To see it fully detached, to see this massive block of ice floating out there, was pretty shocking,'' he said.

Satellite images in July first showed the 2,200-square-mile iceberg calving and floating away from the Larsen C ice shelf. Scientists had been anticipating that the iceberg, known as A-68, would break from the larger ice shelf, and in recent months watched the progress of a crack extending more than 100 miles long.

Ice shelves are large, thick floating extensions of glaciers that have extended from the land. They have long encircled the Antarctic continent, but are now vulnerable because of warming air temperatures and ocean waters, which can cause them to thin or collapse. When they do, the ice behind them is freed to flow more quickly into the ocean, raising sea levels.

The separation of iceberg from shelf was a long time in the making. A crack in the shelf was rapidly expanding from 2011 before it finally broke in 2017. It followed the breakaway of another iceberg from Larsen B, to the North of Larsen C, in 2002.

Operation Icebridge scientists will collect data through the end of the month to track changes in Antarctica's ice coverage, so that they can better understand how the ice shelves and the ocean interact and what effect those interactions may have on climate change. For example, Kurtz said scientists are measuring how much ice is melting from the Larsen C ice shelf both above and below the water to try to predict how the ice shelf might behave in the future.

The instruments scientists are using include radar sounders that measure the thickness and layering of snow and ice and an infrared camera that measures surface temperature.

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