Sensor-Laden Super Seals Dive Deep for New Global Warming Data

A behemoth marine mammal whose diving skills would put an Olympic athlete to shame has become a surprise player in climate-change studies, California researchers reported on Monday. Sporting mini hatlike sensors on their heads, elephant seals at the bottom of the world are collecting data at the bottom of the ocean that long has eluded scientists--until now.

Dan Costa, a biologist from the University of California at Santa Cruz, started tagging seals with sensors 25 years ago in an effort to record information about the animal's behavior and ability to adapt to changes in its environment. When it became clear that the seals dove way deeper and more frequently than had been thought, researchers realized that the sensors could collect more than just biological data.

Southern elephant seals dive 400 to 600 meters (about 440 to 650 yards)--and occasionally as deep as 1000 meters--during an average 60 dives per day. In the Southern Ocean around Antarctica, these depths harbor ocean circulation data that are of great interest to scientists who study climate change.

The Southern Ocean, which encircles Antarctica, holds cold, dense water that acts as a driving force in global ocean circulation. "A lot of the planet's weather is driven by what happens in the Southern Ocean," Costa told PM from Australia this weekend. During the winter season, sea-ice formation around Antarctica essentially doubles the continent's size. Because sea-ice extent and thickness has a significant influence on global climate, understanding the rate at which sea ice forms is crucial to understanding the effects of climate change on the polar regions. (Click here for more from an Antarctic drilling rig.)

But one huge scientific hurdle remains: Much of the ocean beneath the Antarctic sea ice lays unobserved--a significant shortcoming given that the Southern Ocean covers about 19 million square kilometers. Although satellites can detect surface characteristics of sea ice, in situ data that reveal temperature and salinity at depth are needed to determine formation rates.

Now over 50 huge sea creatures are bringing back answers.

During the winter of 2004 to 2005, Costa and his colleagues from Australia, France, Germany and the United Kingdom tagged 58 southern elephant seals at four sub-Antarctic islands with oceanographic sensors. The sensor, which houses a pressure transducer, attaches to a section of fur on the seal's head. As the seal surfaces after a dive, the sensor records the dive depth and duration and takes measurements of water temperature and salinity. Each dive is stored in the sensor's memory, and when the seal surfaces the data are transmitted to a satellite that passes over the Antarctic region about every hour. "For every dive, we're getting answers to two questions: What is the animal doing? And what oceanography can we learn?" Costa says.

Data collected by the seals have provided a thirtyfold increase in hydrographic profiles--charts that show ocean temperature and salinity--from the sea-ice zone. "Measurements collected by these predators have allowed the Southern Ocean's high-latitude fronts to be mapped in regions not sampled by other instruments," Costa writes in a paper published this week in the Proceedings of the National Academy of Sciences.

Several studies have been done to ensure that the sensors have no effect on the seals' behavior. "We've seen alpha males go through an entire breeding season with one of these tags on and seen no effects on his ability to mate," Costa says. The sensors fall off when the seals go through their annual molt (shedding their fur), so a seal never wears one for more than a year.

This year, seals tagged with sensors also helped uncover important information about the Wilkins Ice Shelf, a plate of floating ice about the size of the state of Vermont, on the Antarctic Peninsula, which began disintegrating in late February. According to Costa, tagged seals have been visiting the ice shelf since its breakup, bringing back data that show a previously unidentified tongue of warm water that may have contributed to the shelf's disintegration.

From Costa's point of view, the seal-tagging projects have created a unique partnership between biologists and oceanographers. "We're collecting a tremendous amount of information on these animals and their environment, and the added value is that the data are also of great value to oceanographers who study climate change. It's a win-win situation," he says.


* PLUS: 3 Next-Gen Animal Prosthetics Build Perfect Beasts

* TECH WATCH: Scientists Use Balloons to find Space Particles

* EARLIER: Measuring Antarctic Ice from Inside the Earth

* GREEN LIVING: More Environmental Breakthroughs & Analysis!

(Photograph courtesy of Daniel P. Costa, University of California, Santa Cruz)
Advertisement - Continue Reading Below
More From Earth