Saturday, May 16, 2015

The ABCs of Antarctic Ice Shelf Melting

One of the sleds that scientists used to drag radar instruments across the Larsen C ice shelf. (Credit: BAS) Click to Enlarge.
January 1995 marked a seminal moment in modern Antarctic history, with the crumbling of the Larsen A ice shelf, a floating plain of ice fed by glaciers on the Antarctic Peninsula.  Less than a decade later, its southern neighbor, the Larsen B ice shelf, disintegrated, stunning polar scientists.

After the spectacular collapses of Larsen A and B, scientists began keeping a close watch on the next ice shelf to the south, the Larsen C, which has shown some worrying signs of thinning.  At about the area of Scotland, it is five times larger than the Larsen B (itself five times as large as the Larsen A), “so when Larsen C goes, it’s going to be a really big event,” Paul Holland, a researcher with the British Antarctic Survey, said.

The failure of the Larsen C would mean that Antarctica’s contribution to sea level rise would increase, further imperiling Earth’s built-up coastlines.

The loss of the Larsen A and B ice shelves caused the glaciers behind them to speed their flow to the sea, contributing to the rise of global sea levels that are already threatening the the more than 1 billion people that live along coastlines.  Since the beginning of the 20th century, global sea levels have risen by 8 inches, making storm surges during events like Hurricane Sandy higher and more destructive than they once were and causing more regular minor floods in coastal areas.

The most recent Intergovernmental Panel on Climate Change report estimates global sea levels could rise by between 10 and 39 inches by 2100.  The IPCC estimates that Antarctica’s current contribution to that rise is about a tenth of an inch a year.

One key question Antarctic scientists have been trying to answer is what exactly is happening to the Larsen C.  Are warm waters melting it from below, or is warming air melting it from above?

A new study from Holland and his colleagues, detailed in the journal The Cryosphere, suggests it could be both.

Read more at The ABCs of Antarctic Ice Shelf Melting

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