Deep diving seals yielded critical new knowledge about Antarctica

Deep diving Antarctic seals brought back new knowledge which is critical to predicting global warming,

The tagged seals dived deeper, sometimes by 1 km, than where the sea floor was believed to be. Picture: Clive McMahon / Sydney Institute for Marine Science

With the help of deep diving seals, Australian scientists have filled the gaps in their knowledge of the sea floor around Antarctica and gathered new information about oceanographic processes which drive climate.

Over the past two decades 50 Weddell seals and 215 southern elephant seals have been tagged with devices that recorded over half a million dives on the East Antarctic continental shelf. In about a quarter of cases, the seals went deeper than the sea floor was believed to be at that location.

“The seals were diving hundreds of metres below those depths. In the most extreme case, they were diving 1,000m deeper than what we thought was the ocean floor,” said Mark Hindell, from the University of Tasmania’s Institute for Maritime and Antarctic Studies, who co-authored a paper about the seal’s diving habits in the most recent edition of the journal Nature Communications Earth and Environment.

The seals’ dives revealed previously unknown underwater features including troughs off the Shackleton Ice Shelf and Underwood Glacier, and a deep canyon near the Vanderford Glacier which was recently confirmed by a survey using an echo sounder.

An elephant seal tagged with the tracking device. Picture: Clive McMahon / Sydney Institute for Marine Science

Clive McMahon from the Sydney Institute for Marine Science, said the observations were particularly helpful in identifying channels through which warmer water can enter ice cavities. “This knowledge is essential for scientists trying to measure ice sheet melt rates,” he said.

Dr McMahon is the lead author of the paper, which is titled “Southern Ocean pinnipeds provide bathymetric insights on the East Antarctic continental shelf”.

The melting rate of the East Antarctic ice sheet is particularly important to estimating the rate of sea level rise due to global warming because its volume of ice is equivalent to over 50 metres of sea level rise.

The devices attached to the seals measure temperature, salinity and depth as the seals swim.

Dr McMahon said that knowledge of the shape of the sea floor of the East Antarctic continental shelf had previously been sparse.

“Given the remote and inhospitable nature of Antarctica and the surrounding Southern Ocean, only a small part of the Antarctic continental shelf was surveyed by ships,” he said.