The discovery of an underwater mountain ridge could help solve the mystery of why Antarctica鈥檚 Pine Island glacier is vanishing so rapidly.
A robot submarine sent beneath the glacier鈥檚 floating ice sheet has shown that there is a ridge rising 400 metres from the sea floor. Until recently, the glacier would have rested on this ridge, preventing warm seawater from reaching the ice and melting it from underneath. But the submarine has shown that the glacier no longer rests on the ridge 鈥� it has thinned and now floats above it (Nature Geoscience, ).
鈥淥nce you tip the glacier off the ridge, it continues to thin, and this allows even more warm water over the top of the ridge, so it reinforces the whole process,鈥� says of the British Antarctic Survey.
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In January, a modelling study suggested that if such a ridge did exist, then once the glacier retreated behind it, the glacier would not be able to recover.
鈥淭he study confirms our concern that this is a major area of ice mass loss that could be sustained,鈥� says Christian Schoof of the University of British Columbia in Vancouver, Canada. Pine Island glacier is one of a handful in West Antarctica which together are estimated to be responsible for about 10 per cent of global sea-level rise.
