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Diving Deep with Elephant Seals

Most of us only get to see an Elephant Seal—like this member of the northern species resting on a California beach in the Photo of the Week above—during the relatively short period of time the large marine mammals spend on land molting or mating. But as impressive as they may appear on shore (particularly the bulls), we don’t normally get to see them where they spend almost 80% of their lives. In the ocean. Swimming, for months at a time and for thousands of miles, before returning to land. And hunting for food by repeatedly diving, as deep as a mile, for as long as two hours at a time.

That diving ability caught the attention of oceanic researchers studying ice shelves during the frigid Antarctic winter. No human or human-made vessel could get near enough to the area they sought to study, dive below the sea ice, or stay there long enough to make the observations or collect the data they needed. But the Elephant Seal can. They’ve thrived in these extreme conditions for millennia.

And thanks to technological advances—data collecting satellites and miniaturized sensors and cameras—the scientists could enlist accommodating Elephant Seal to collect data for them. As they dove, hunting for squid and fish, sensors attached to the seals capture and transmit data to waiting satellites above.

The result? “Between 2004 and 2005, the seals swam up to 65 kilometers (40 miles) a day, supplying scientists with 16,500 ice profiles” and providing significant amounts of data “on ice formation, ocean currents and climate change” for the scientists.

In other experiments, the seals have helped scientists discover “a long-elusive source for the deep-ocean streams of cold water that help to regulate the Earth’s climate.” These areas of “Antarctic bottom water” contain “cold, highly saline water that forms near the shores of Antarctica. Being denser than typical seawater, it sinks to the depths and then moves north in sluggish currents that spread across the globe.”

Concerned that rising global temperatures could disrupt these slow-moving currents of cold water, “letting the ocean depths warm and thereby changing the rate of heat exchange between Antarctica and the tropics,” scientists are eager to learn as much about them as possible and include that information into climate-change models.

The seals have also delivered clues about another vexing problem: why Antarctic Sea Ice has been melting at rates faster than in the past. Diving far below the surface, seals have returned with data revealing a submerged layer of water slightly warmer and more saline than the frigid water near the surface. Scientists postulate “that this Circumpolar Deep Water has been sneaking up onto the continental shelves that surround Antarctica and lapping at the bases of marine glaciers, melting them from below.” Could this additional factor cause global sea levels to rise even faster and higher than current climate models predict?

Perhaps the Elephant Seals can help us with that question, as well.

To read more about Elephant Seals and the data they’ve been collecting, see the following articles:

Northern Elephant Seal [The Marine Mammal Center]
Northern Elephant Seal [Monterey Bay Aquarium]
Southern Elephant Seal [Arkive]
Southern Elephant Seal [MarineBio]

Elephant seals join fight against climate change
Elephant Seals Help Find Missing Piece in Global Climate Puzzle
These Elephant Seals Just Taught Scientists Why Antarctica Is Melting So Fast