Scientists floored as seals hit new Antarctic depths

Deep-diving seals have shed new light on the depths of Antarctic waters, with some travelling one kilometre below what was previously thought to be the ocean floor.

Data from more than 557,000 dives beneath the East Antarctic Shelf, an area where seals have been fitted with satellite-linked tags since 2004, was analysed in a study.

Co-author Mark Hindell said the information would improve understanding of oceanographic processes impacting Antarctica’s role in the world’s climate.

“We found in some regions that more than 25 per cent of previous estimates of the ocean depths were wrong,” Professor Hindell said.

“We only know this now because the seals were diving hundreds of metres below those depths.

“In the most extreme case, they were diving 1000m deeper than what we thought was the ocean floor.”

The dives revealed new underwater features, including troughs off the Shackleton Ice Shelf and Underwood Glacier, as well as a deep canyon near the Vanderford Glacier.

The canyon was confirmed by a recent multi-beam echo sounder survey from Australia’s icebreaker.

It is estimated only 23 per cent of the earth’s sea floor has been mapped accurately, with Antarctic waters even less well-known.

Lead author Clive McMahon, based at the Sydney Institute of Marine Science, said the seal data was essential for scientists trying to measure ice sheet melt rates.

“The observations we collect from the seals help us better understand the shape of the ocean floor, especially where there are channels for warm water to access ice shelf cavities,” Dr McMahon said.

Prof Hindell said that as the climate changes, greater intrusions of warm water into the shelf cavities are more likely.

Tags, which measure water temperature, salinity and depth, were attached to 50 Weddell seals and 215 southern elephant seals as part of the research.

The study was published in scientific journal Nature Communications Earth and Environment.


Ethan James
(Australian Associated Press)


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