Enlarge / The rift in the Larsen C Ice Shelf, as seen in November 2016. (credit: John Sonntag/NASA)

Concluding a months-long deathwatch, one of the largest icebergs ever seen finally separated from Antarctica’s Larsen C Ice Shelf sometime in the last couple days. The 5,800-square-kilometer iceberg contains over a trillion tons of ice. For years, researchers have been keeping an eye on a growing rift in the floating ice shelf that raced toward completion in recent months.

The Larsen C Ice Shelf is composed of floating ice at the front of glaciers on the narrow Antarctic Peninsula. The breaking off of icebergs from shelves—a process called “calving”—is normal, though icebergs of this size are obviously rare. While warmer water or air temperatures have been an important factor in controlling the size of many Antarctic ice shelves, there’s no indication that climate change has played a significant role in the calving of this specific iceberg.

Because ice shelves are already floating, the melting of icebergs does not appreciably affect sea level (although there is a small contribution because melting icebergs dilute the saltiness of seawater).

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