Crack in Antarctica’s Larsen C ice shelf forks

The 180-kilometer-long crack threatening one of Antarctica’s largest ice shelves has branched out, new satellite observations reveal. The main rift in the Larsen C ice shelf hasn’t grown longer since February. But radar mapping shows that a second crack has split off from the main rupture like a snake’s forked tongue, members of the Antarctic research group Project MIDAS reported May 1. That second branch, which stretches around 15 kilometers, didn’t exist on radar maps taken six days earlier, the scientists say.

If either branch makes it to Larsen C’s edge, the shelf could calve off a 5,000-square-kilometer hunk of ice, creating one of the largest icebergs ever recorded, says glaciologist Adrian Luckman of Swansea University in Wales. “The new branch is heading off more toward the ice front, so it’s more dangerous and more likely to cause this calving event to occur” than the existing branch, he says.

Snapping off such a large ice chunk could destabilize the entire ice shelf, Luckman warns. A similar event led to the collapse of Larsen B in 2002. Because Larsen C’s ice floats on the ocean, the loss wouldn’t directly raise sea levels. But its demise could serve as a case study of how other shelves may break apart as rising temperatures melt and weaken Antarctic ice, Luckman says.

Divergence

Recent radar mapping of Antarctica’s Larsen C ice shelf (top left) reveal that a new crack (right in both inset and white section of diagram) has forked from a long fissure that cuts across the ice shelf. If either branch of the fissure, which has grown considerably over the last few years (dates mark recorded changes in the crack’s length), reaches the shelf’s edge, it could snap off a massive iceberg.