The platonic ideal of an iceberg is a jagged hunk of ice that looks like a floating mountain crag. But new images from NASA reveal an Antarctic iceberg that is so exquisitely neat in its geometry that it seems as if it was created with a giant rectangular cookie cutter.
Photographed by NASA’s IceBridge polar plane last Tuesday, the oddly satisfying formation belongs to class of floating ice structures called tabular icebergs, named for their tabletop shapes. Estimated to be at least one mile across, the iceberg’s unusually clean shape suggests it recently separated from the Larsen C ice shelf on the eastern shore of the Antarctic Peninsula, and hasn’t been significantly eroded yet.
Tabular icebergs are formed when their weight snaps them free of their host ice shelves, which are large floating sheets of ice connected to landmasses. In contrast, non-tabular icebergs, like the one that sank the Titanic, can form in many different ways, including calving off of ice shelves or glaciers, or from the breakups of larger icebergs.
Most tabular icebergs aren’t as stunningly tidy along the edges as the one imaged by IceBridge, but rectangular “ice islands” are still common off the shore of ice shelves. One of the most famous examples is Pobeda Ice Island, which forms periodically off East Antarctica and can extend for several hundred square miles on its flat top.
While it is natural for icebergs of all shapes and sizes to break off from large ice shelves, climate change may be accelerating the rapid deterioration of ice shelves like Larsen C. The Antarctic Peninsula has warmed by about 0.5°C per decade since the 1940s, but scientists are still uncertain of the degree to which human-driven global warming is responsible for this trend. Regardless of what is causing the collapse of Antarctic ice shelves, the meltwater from these events will contribute to projected rising sea levels in the coming decades.
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