| Summary: | Elephant seals have helped scientists unravel a 30-year-old mystery around the sources of the ocean's deepest waters.In a paper published today in Nature Geoscience, scientists from Australia and Japan reveal a fourth source of Antarctic bottom water lying off Cape Darnley.Antarctic bottom water - cold, dense water that sits in the abyssal zone between 4000 metres and 6000 metres below the ocean's surface - plays a plays a key role in global water circulation and the transport of carbon dioxide to the deepest layers of the ocean.The discovery of a fourth source of deep water is critical to our understanding of Antarctica's contribution to global ocean circulation, and will improve modelling of its response to climate change, says study co-author Dr Guy Williams, of the Antarctic Climate and Ecosystem Co-operative Research Centre.Williams says the Cape Darnley deep water contributes about 10 per cent of volume to the Antarctic bottom water.The discovery of a fourth source is like "finding a new component in the engine," he says.Until recently only three sources of the deep waters were known - the Weddell and Ross seas and off the Adelie Coast.But in 1977 a US study uncovered bottom water with high oxygen levels in the Weddell-Enderby Basin off shore of Antarctica's Mac Robertson Land."That was the smoking gun - it was a signal that this water had recently been near the surface [of the ocean] and had somehow been converted into this dense, deep ocean water," says Williams.
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