Antarctica this week shed an iceberg of mind-boggling size from its Larsen C ice shelf.
The block of ice was unceremoniously given the name of A68 by the US National Ice Center, whose abbreviations denote both an iceberg's location and its order of discovery.
Iceberg A68 now begins a long journey into the Southern Ocean and toward its doom: liquid in Earth's vast and complex system of water.
Here's how scientists discovered the giant iceberg, how it calved, and how it will eventually die — and be reborn.
In 2015, the glaciologist Daniela Jansen discovered a growing crack in Antarctica's Larsen C ice shelf, which was then the fourth-largest ice shelf on the continent. The shelf is hundreds of years old, maybe more.
Ice shelves like Larsen C, and their icebergs, come from snow that has covered Antarctica over thousands of years and compacted into ice. In many places, the ice is a mile thick down to bedrock.
Source: NASA Goddard Space Flight Center
But the ice doesn't sit there. Gravity tirelessly pulls it toward the sea, where it floats on the water to form gigantic ice shelves.
Scientists like Jansen and Adrian Luckman, both glaciologists at Swansea University and the Midas Project, study Antarctica's changing ice shelves and melting surface.
"We spent many weeks camped on the ice investigating melt ponds and their impact — and struggling to avoid sunburn thanks to the thin ozone layer," Luckman said. "Our main approach, however, is to use satellites to keep an eye on things."
In November, NASA flew a survey airplane over Larsen C to get a closer look. Satellite images suggest the crack formed around 2010, but it suddenly and rapidly started growing in 2016.