The floating ice shelves of West Antarctica are fracturing increasingly and losing their grip on the rocky bay walls that slow their flow, threatening to speed up the flow of ice from land to sea, a new study finds.
The study looked at 40 years of satellite images of West Antarctic ice shelves, which have seen rapid ice loss over the past few decades. The region has been steadily warming over the past 30 years; one region in particular, the Antarctic Peninsula, is one of the fastest warming spots on the planet.
The West Antarctic Ice Sheet, which is about the size of Greenland, contains about 10 percent of all the ice in Antarctica. All of this ice makes breakoffs and melting particular concerns in terms of potential sea level rise. Scientists estimate West Antarctica contributes nearly 10 percent of global sea level rise from an acceleration in glacier ice melt.
The glaciers that make up the ice sheet slowly flow toward the sea, and there the ice flows out to sea and floats atop the ocean, forming what is called an ice shelf.
The flow of the glaciers is resisted naturally by the seams where the glaciers merge and by the rocky bay walls that the ice shelves attach to, making the shelves act as a sort of doorstop.
But the satellite record shows that in the eastern Amundsen Sea Embayment, the margins of the ice shelves, where the ice grips onto the rocky walls, are fracturing and retreating inland.
The fracturing increases until the ice shelf calves, or spits off, new icebergs that then drift out to sea. Calving is a normal process, but it is changing with these increasing cracks.
As an ice shelf's grip continues to loosen, these already-thinning masses of ice will be even less able to perform their doorstop function of holding back the grounded ice upstream, leading to potentially even faster flow of these already speedy glaciers.
"An accelerating glacier can tear away from its margins, creating rifts that negate the margins' resistance to ice flow and causing additional acceleration," said study co-author Ginny Catania of the University of Texas at Austin that conducted the research.
The research team found that the largest relative glacier accelerations occurred within and upstream of the increasingly rifted margins.
The study researchers, whose findings are detailed online in the Journal of Glaciology, say the ice shelves are poised to disintegrate further.
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