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NASA Satellites Watch Polar Ice Shelf Break into Crushed Ice Ice is melting at the poles much faster than climate models predict

By Peter Brown

The accelerating pace of climate warming in the earth’s polar regions is spurring a new sense of scientific urgency. This past February 28 a camera onboard the NASA satellite Aqua caught a Manhattan-size floating piece of ice shelf in the act of disintegrating. Slabs continued to calve and break up throughout the next 10 days; by March 8 the Wilkins ice shelf, comprising some 5,000 square miles of floating ice off the coast of the Antarctic Peninsula, had lost 160 square miles of ice to the Pacific Ocean.

The breakup is the latest of seven major Antarctic ice-shelf collapses in the past 30 years, after some 400 years of relative stability. They include the detachment of a 1,300-square-mile chunk from the Lars­en B ice shelf, the disintegration of giant ice shelves in the Prince Gustav Channel and the Larsen Inlet, and the disappearance of ice shelves known as Jones, Larsen A, Muller and Wordie. All of them corroborate temperature measurements showing that the western Antarctic Peninsula—now known to insiders as the Banana Belt—is warming up faster than anyplace else on earth.

The Wilkins event—serendipitously caught on video by a team from the British Antarctic Survey just days after it was discovered—has rallied scientists around the world. “You have closer communication than ever among the global science community now,” says Robin E. Bell, a polar research scientist at the Lamont-Doherty Earth Observatory of Columbia Uni­versity. “We’re more sensitive that change is really happening quickly.” Relatively warm air seems to be the main culprit. As ice melts in the austral summer, pools of water fill the cracks that inevitably develop in any floating ice shelf as a result of bending and squeezing by the surrounding ocean. In a colder climate those fractures would be nothing more than shallow surface scars. But liquid water in the cracks can drill like a hot knife to the base of an ice shelf, snapping it in two.

The breakup and melting of floating ice has no direct effect on global sea levels. But an ice shelf is thought to act as a “cork in the bottle,” damming the flow of the land-based glacier that slowly feeds the shelf in the sea. When such a “cork” is removed, the glacier lurches forward. “Within a few months” of a breakup, explains glaciologist Ted Scambos of the National Snow and Ice Data Center at the University of Colorado at Boulder, the glacier “accelerates significantly, and within a year or two, it can be moving [toward the ocean] up to four times as fast as it moved when the ice shelf was intact.” As Bell puts it, the result is that “more ice cubes get into the ocean,” which does raise sea level.