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Oslo: Seals unlock Wilkins Ice Shelf mystery

It’s clear that Antarctica’s Wilkins Ice Shelf has suffered considerable disintegration, breaking up in 1998, 2008 and 2009. What’s been less clear is exactly where all of the heat to cause the collapses came from. Now elephant seals carrying sensors on their heads have helped solve the mystery.

The sensors revealed the seals were diving to greater depths than current bathymetry records acknowledged existed, Daniel Costa of the University of California explained at the International Polar Year Oslo Science Conference. This indicated the presence of troughs in the continental shelf underneath the ice; it seems these troughs enabled warm circumpolar deep water to travel onto the continental shelf and help weaken the ice above. A paper on these results is currently under review at GRL.

Not only have the seals helped oceanographers and glaciologists but the data they have collected could help predict their own future as climate changes in the Antarctic Peninsula. Information gathered during an IPY project shows that elephant seals tend to forage in circumpolar deep water. Crabeater seals, on the other hand, feed in both circumpolar deep water and Antarctic surface water, and stray much less far from the ice shelf around the peninsula.

If winds speed up in the future as climate change predicts they will, this is likely to cause more circumpolar deep water to intrude onto the continental shelf, bringing additional heat to the region. While probably a bonus for the elephant seals that forage for fish and squid in such water, it’s likely to reduce the amount of sea ice off the Antarctic Peninsula. That could be bad news for crabeater seals as they feed on krill, which like to live under pack ice. Crabeater seals also rely on sea ice to breed, unlike land-breeding elephant seals. So it looks like elephant seals could become more abundant in the Antarctic Peninsula and crabeater seals less so.

That said, the past has also seen changes in the distribution of wildlife in the Antarctic region, Costa explained. Analysis of seal fur from old haul-out sites in the Ross Sea region has shown that elephant seals used to visit the region but they no longer do.

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