The first summer without an Arctic ice sheet is already on the horizon. The massive chunk of frozen ocean has capped the northern pole of our planet year-round for millennia, but it’s now at risk of receding until it disappears entirely.
Unlike its northern sibling, the kilometers-thick Antarctic ice cap in the south is seated on a buried continent rather than on water. It’s bigger and older than the Arctic ice sheet, and less vulnerable to threats of a warming climate.
Researchers generally agree, however, that the Antarctic will also lose significant amounts of ice mass as the Earth’s temperature rises. The timeline and extent of that loss is just less clear. Unlike the charts of the Arctic’s annual ice, which seem to have taken a plunge toward zero over the last decade, the Antarctic’s process has been more wobbly. As recently as 2014, the southern ice cap reached is largest extent on record.
Here’s what we know about Antarctica’s strange, ancient ice, and what could happen in its future.
The Larson C ice shelf is a colossal block of sea ice off Antarctica's coast. It covers about 2,000 square miles of open ocean, and is 1,100 feet thick at the edge (and thicker toward the middle).
The huge crack isn't new -- it was first spotted in 2010 and has been fairly stable for the last few months.
But a new crack has appeared at its leading edge, forking away from the existing rift. Researchers say this split signals that the iceberg -- nearly the size of Delaware -- is at risk of calving off.
Larsen and other ocean ice shelves like it ring the continent, creating natural barriers that keep massive amounts of ice from sliding off the land into the ocean.
If Larsen C breaks off, some researchers worry it would be like removing a cork from a bottle of champagne. Once it pops off and into the sea, some land-based glaciers could flow out after it.
Melting has been slower in Antarctica, however, and no one can say for certain whether the Larsen C ice shelf will calve, or if other similar ice blocks elsewhere in Antarctica might do the same.
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