Each Antarctic ice shelf typically sheds a super-size iceberg only once every few decades. Global warming might seem like the most likely explanation, but researchers have been unable to directly link warming to the rapid-fire shedding from the continent's southernmost ice shelves. In fact, scientists argue, the ice shelves were overdue to unload these huge burdens. A breed apart Antarctic icebergs are a breed apart from their Arctic brethren. Most large icebergs in the Northern Hemisphere calve from glaciers that flow into the ocean along the coasts of Alaska and Greenland.
Smaller chunks come from the breakup of ice that forms on the ocean every winter.
In contrast, large southern bergs, which often cover hundreds of square kilometers, periodically split off from ancient ice shelves that float atop the frigid southern seas. Nourished by the languid flow of solid kilometers-thick ice sheets overlying the continent, some of these ice shelves are hundreds of meters thick and cover shallow coastal regions the size of Texas or larger. Although the Arctic Ocean doesn't have such perennial ice shelves these days, there are hints of their earlier presence. North or south, massive changes in the icescape normally happen slowly. There's a reason the word glacial means slow.