Nearly 20 years ago, the Ross Ice Shelf, the largest ice shelf in Antarctica at several hundred meters thick, saw a huge chunk break off, float out to sea and break up again into several large pieces. Now, one of these pieces has started to float out to warmer waters where it is expected to die, NASA says.

Known as B-15T, this "coffin-shaped" iceberg is now floating around the South Atlantic, between South Georgia and the South Sandwich Islands, NASA said.

"B-15T’s journey to this iceberg graveyard has been a long one. Its parent berg (B-15) first broke away from the Ross Ice Shelf in March 2000," the government agency explained on its website. "It fractured over time into smaller bergs, many of which continued riding the Antarctic Coastal Current (counter-clockwise) around Antarctica."

For its entire lifespan, this iceberg went around Antarctica in the Antarctic Coastal Current, going counter-clockwise around Antarctica, NASA explained. But by the latter part of 2017, the Weddell Sea gyre had "redirected B-15T from its near circumnavigation and sent the berg drifting north."

From there, it entered the Antarctic Circumpolar Current, which "funnels through the Drake Passage, then steered the iceberg toward the east and its current location." At this spot on the Earth, water is significantly warmer than the Southern Ocean and is considered "deadly" for icebergs.

NASA/UMBC glaciologist Chris Shuman said that the odd shape was acquired long ago and is the byproduct of a number of collisions, including hitting the Ross Ice Shelf itself, bedrock along the coast and other tabular icebergs.

“The coffin shape is an accident of time and space, given the approximately 18.5-year voyage of B-15T,” Shuman said. “We can only guess at the forces that have acted on this remnant of B-15 along the long way around Antarctica.”

Last month, NASA released images of a huge, flat iceberg with perfect, right angles, floating among sea ice just off the Larsen C ice shelf.

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