Rising ocean temperatures, not atmospheric temperatures, are melting the Antarctic floating ice shelf Pine Island Glacier and possibly other ice shelves, an international team of researchers found.
The scientists examined the remote glacier, which represents a major outlet of the West Antarctic Ice Sheet, in hopes shedding new light behind its rapid thinning in recent years.
By placing a variety of instruments deep below the ice's surface and using radar to map the underside of the ice shelf and the bottom of the ocean, the scientists discovered several factors behind the ice shelf's demise, including warm ocean water.
"We've been dumping heat into the atmosphere for years and the oceans have been doing their job, taking it out of the air and into the ocean," Sridhar Anandakrishnan, a professor of geosciences at Pennsylvania State University, said in a statement. "Eventually, with all that atmospheric heat, the oceans will heat up."
Compounding this are a series of channels located beneath the ice shelf through which the warm ocean water is able to enter.
The result, according to researchers, is a non-uniform melting effect particularly equipped to break the ice shelves apart.
When ice shelves already in the ocean melt, they do not contribute to sea level rise due to the fact that their presence in the water has already been accounted for. However, most of the Antarctic's glaciers are located on land, which means that rapidly adding new ice shelf material to the floating mass will eventually mean more water in the ocean.
"Antarctica is relatively stable, but that won't last forever," Anandakrishnan said. "This is a harbinger of what will happen."
This interaction of the ocean water beneath the ice shelf and the rate at which the ice shelf is melting should be taken into account in models designed to account for sea level rise as a result of global warming, the researchers argue.
"The Antarctic has been relatively quiet as a contributor to sea rise," Anandakrishnan said. "What this work shows is that we have been blind to a huge phenomenon, something that will be as big a player in sea level rise in the next century as any other contributor."
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