World's Biggest Iceberg Is on the Move

After spending 30 years stuck to the bottom of the Weddell Sea in Antarctica, iceberg A23a is finally floating free.

The iceberg is the largest in the world. Its size puts most cities to shame. A23a's 1,500 square miles of icy surface is about three times the size of New York City. And that only describes what’s visible above the waterline. Like most icebergs, A23a keeps its bulk hidden in the depths. Scientists estimate that A23a is at least 1,312 feet thick. Only about 100-150 feet of the iceberg crests above the ocean’s surface.  

A23a first “calved”, or broke off from, the Filchner-Ronne ice shelf along the coast of Antarctica in 1986. It grounded in the shallow waters of the Weddell almost immediately. The massive, frozen chunk has slowly dwindled in size, becoming detached from the ocean floor. Now it's riding the currents of “iceberg alley.” That's a path into the Southern Ocean that’s taken many floes toward the tip of Argentina.  

Cruising along at about three miles per day, A23a is expected to melt in the open ocean over the course of the next few years. And as for what caused A23a to begin its journey? Experts think it was simply time.

"I asked a couple of colleagues about this, wondering if there was any possible change in shelf water temperatures that might have provoked it, but the consensus is the time had just come," Andrew Fleming told the BBC. He's an expert from the British Antarctic Survey.   

Reflect: How do you think the process of an iceberg breaking free and floating in the ocean might affect the surrounding environment?