One of the sleds that scientists used to drag radar instruments across the Larsen C ice shelf.

One of the largest icebergs ever recorded broke off Antarctica’s Larsen C ice shelf earlier this week, according to satellite pictures and scientists who monitor such things, permanently altering the coastline of our planet’s frozen continent.

Twice the size of Long Island and packing a trillion tons of ice — fully melted, that’s enough water to fill Lake Michigan — the newly birthed iceberg seems like a perfect symbol for our overheating world. But there’s a more complex story at play.

You might be thinking: Should I have moved to the mountains of Colorado yesterday? Well, this one iceberg itself (likely to be named A68) doesn’t mean much on its own. Its “calving” (as scientists call it) was likely mostly natural, and it was already floating, so it won’t contribute significantly to sea-level rise. And there are other regions of Antarctica that contain vastly more ice.

But now the clock could be ticking on the collapse of Larsen C itself, kicking off one of the most potentially important natural science experiments in human history. By closely watching what happens at Larsen C, we’ll be able to learn more about what might happen to the rest of Antarctica in our lifetimes, and refine sea-level rise projections for the coming decades.

“This puts the ice shelf in a very vulnerable position,” said Martin O’Leary, a member of the Swansea University monitoring team that first announced the iceberg’s formation on Wednesday. “This is the furthest back that the ice front has been in recorded history. We’re going to be watching very carefully for signs that the rest of the shelf is becoming unstable.”

The Larsen C shelf is a floating mass of ice located about midway down the Antarctic Peninsula, and the fourth-largest on our southernmost continent. The peninsula itself is a frozen finger of land that extends northward toward the southern tip of Chile; it’s a hotspot of climate change.

Scientists have been monitoring this area for years, watching a crack in the ice shelf slowly progress toward the sea. In the past few months, the rift dramatically accelerated — leading to close scrutiny of every satellite image taken of the area in recent days.

Larsen C animation
University of Edinburgh–N. Gourmelen

Larsen C’s newborn offspring carries enough ice to coat the entire United States in a 4.6-inch thick skating rink, but its impact on sea levels will be negligible; ice shelves are already-floating extensions of inland glaciers that have moved out over the ocean. Calving (yes, just like momma cow giving birth to a calf) is a natural event that happens regularly on ice shelves, and it’s necessary to balance out the snowfall that the parent glaciers receive.

As long as the parent ice shelf remains stable, A68 should have no measurable impact on the rest of the planet, other than posing a hazard to ships in the South Atlantic, potentially for years to come.

Just for fun calc:…