Researchers enlist elephant seals to gather undersea data

How do you study some of the ocean’s most inaccessible regions? Hitch your instruments to elephant seals.

That’s an approach a team of scientists has used to gather basic physical data on the Southern Ocean beneath the ice-clad reaches near Antarctica. Information on how temperature and salinity change with depth is critical to understanding ocean circulation and its effect on the ocean’s carbon cycle.

In the open ocean, such data are typically collected from ships that lower an array of water-sampling bottles to various depths. It can also be done through automated sensor packages known as Argo floats. But the ocean around Antarctica poses special problems. In winter, ice extends far out to sea, preventing ships or Argo-style floats from measuring conditions for some 7 million square miles of ocean.

So a team from the United States, Australia, and Europe came up with their variation of “critter cams.” They “tagged” 58 southern elephant seals with small sensor packages, then turned them loose. The sensors are attached to the seals’ heads with waterproof epoxy glue. The sensors stay on for up to a year, until the seals molt. The collected data are relayed back to the scientists via satellite.

The deep-diving elephant seals, which feed in and around the winter ice pack, provided 30 times the profiles researchers ordinarily see, allowing them to map features and gauge ice-formation rates in ways they couldn’t before.

The group concludes that drafting these and other ocean predators as living remote sensors could provide a cost-effective way of taking targeted measurements in parts of the ocean that might otherwise never be studied.
The results appear in the current edition of the Proceedings of the National Academy of Sciences.