Powerful ocean currents beneath West Antarctica's Pine Island Glacier Ice Shelf are eroding the ice from below, speeding the melting of the glacier as a whole, a new study has found.
According to the study, published in the journal Nature Geoscience , a growing cavity beneath the ice shelf has allowed more warm water to melt the ice – a process that feeds back into the ongoing rise in global sea levels.
The glacier is currently sliding into the sea at a clip of 4 km a year, while its ice shelf is melting at about 80 cubic km a year – 50 per cent faster than it was in the early 1990s, the researchers said.
“More warm water from the deep ocean is entering the cavity beneath the ice shelf, and it is warmest where the ice is thickest,” said Stan Jacobs, an oceanographer at Columbia University's Lamont-Doherty Earth Observatory and the lead author of the study.
In 2009, Jacobs and an international team sailed to the Amundsen Sea aboard the icebreaking ship, Nathaniel Palmer, to study the region's thinning ice shelves – floating tongues of ice where land bound glaciers meet the sea.
One goal was to study oceanic changes near the Pine Island Glacier Ice Shelf, which they had visited in an earlier expedition, in 1994.
The researchers found that in that 15 years, melting beneath the ice shelf had risen by about 50 per cent. Although regional ocean temperatures had also warmed slightly, by 0.2 degrees C or so, that was not enough to account for the jump.
The local geology offered one explanation. On the same cruise, a group led by Adrian Jenkins, a researcher at British Antarctic Survey and study co-author, sent a robot submarine beneath the ice shelf, revealing an underwater ridge.