|The edge of the Ferrigno Ice Stream is seen from a plane. A valley below the stream as well as an offshore channel appear to be allowing relatively warmer sea water to eat away at the ice from below.|
The ancient topography is such that relatively warm sea water could be eating away at the ice edge -- and a question for future research is whether that process is happening elsewhere along Antarctica's coastal rift valleys.
A few other ice-covered valleys have been found but the geology of this one, discoverer Rob Bingham told NBC News, shows that "the areas that are most vulnerable (to ice loss) coincide with areas of ancient rifting."
Reported in the peer-reviewed journal Nature, the find came about when Bingham was part of a British Antarctic Survey team looking at the Ferrigno Ice Stream, an area on the vulnerable West Antarctic Ice Sheet, to see why it was losing ice.
"It was in doing this that we discovered the ice in this region is underlain by a rift" a mile deep in places, Bingham said. Radar showed that "ice losses are concentrated over the rift," he added, allowing researchers to conclude that "the rift topography exacerbates the current ice losses."
Ice from the rift also carved a channel over millions of years that is now covered by coastal seas and appears to be allowing relatively warmer water to "flow back towards the Antarctic ice margin" and then melt it, Bingham said.
The melt causes the ice surface slope to steepen "and this in turn accelerates ice flow such that the ice surface drops over time. The presence of the rift valley facilitates this flow and is thus contributing to gradual depletion of the central ice cover."
Others scientists said the discovery would help better understand the dynamics of Antarctica.
|This illustration shows the Ferrigno Ice Stream, outlined in black and just above a channel, seen in green, that appears to allow relatively warmer water to eat away at the ice margin.|
The British Antarctic Survey agreed on the significance.
"The West Antarctic Ice Sheet is of great scientific interest and societal importance as it is losing ice faster than any other part of Antarctica with some glaciers shrinking by more than one meter (three feet) per year," it said in a statement coinciding with the study.
"Thinning ice in West Antarctica is currently contributing nearly 10 percent of global sea level rise," added BAS scientist David Vaughan. "It's important to understand this hot spot of change so we can make more accurate predictions for future sea level rise."
Study co-author Fausto Ferraccioli, a BAS scientist, told NBC News that satellite and aircraft surveys over the rift would help better explain the dynamics.
"We now need new airborne geophysical surveys both onshore and offshore," he said, in order to understand all facets of "this changing part of the West Antarctic Ice Sheet."
Source: NBC News