Melting Sea Ice

Scientists are watching, but not alarmed by, a growing crack at the edge of a key floating ice shelf in Antarctica. The long-watched rift in the Larsen C ice shelf grew 11 miles in the last few weeks. The crack is now about 60 miles long and about 300 feet wide. If it grows another dozen miles, a Delaware-sized iceberg could break off and float away.

A large section of the mighty West Antarctica ice sheet has begun falling apart and its continued melting now appears to be unstoppable. If the findings hold up, they suggest that the melting could destabilize neighboring parts of the ice sheet and a rise in sea level of 10 feet or more may be unavoidable in coming centuries.

The ice of Greenland and the rest of the Arctic is melting faster than expected and could help raise global sea levels by as much as 5 feet this century, dramatically higher than earlier projections, an authoritative international assessment says.