VIMS scientist uses underwater gliders to study the Virginia coast

June 2, 2014 - via Virginia Institute of Marine Science

A quarter-century ago, American oceanographer Henry Stommel imagined a world where thousands of autonomous underwater robots roamed the seas, collecting masses of vital raw data for scientists who sat snug on dry land.
Stommel died in 1992, long before he could see his vision realized.

But on Wednesday, physical oceanographer Donglai Gong of the Virginia Institute of Marine Science acknowledged Stommel as he prepared to deploy an autonomous underwater robot in the York River in a public demonstration of this growing technology. "Stommel was and still is a rock star in physical oceanography," Gong says. "This instrument was inspired by science fiction. It's a vehicle that can deploy around the world, in any ocean."

And once deployed, Gong explained, the vehicle — called a Slocum underwater glider after the first man to sail alone around the world "for fun" — will go wherever it's programmed to go. It will collect whatever data it's programmed to collect, from salinity to turbidity, temperature to oxygen levels.

It can gather the information by the second in a virtual live data stream and, once it surfaces, can transmit that data by GPS satellite back to the command computer. From there, Gong said, researchers can analyze oceanographic features, "seeing" them in extremely high resolution.

Such information can help them better conduct a host of research — the effect of water quality or underwater noise on marine mammals, for instance, the impact of warming ocean temperatures, or red tides and dead zones, which can be lethal to marine life.

The Chesapeake Bay has long been plagued by dead zones caused by seasonal algal blooms that suck up dissolved oxygen from the water. Algae growth explodes when nutrients such as nitrogen and phosphorus are dumped into waterways by stormwater runoff.

In action
There are hundreds of underwater gliders around the world now, Gong said, and VIMS owns two of them. Located in Gloucester Point, VIMS is affiliated with the College of William and Mary in Williamsburg. Gong arrived at VIMS in 2012 from the Woods Hole Oceanographic Institution.

On Wednesday, Gong had placed one glider for show on the bottom of the 105-foot Alliance schooner, a commercial vessel operated by Yorktown Sailing Charters, while the other was eased into the river by his assistants aboard the Egret, a powerboat trailing nearby.

The gliders are bright yellow, about 6 feet in length and a foot in diameter, and weigh about 140 pounds. Each costs between $150,000 and $200,000, he said.

They can be outfitted with specialized equipment such as hydrophones to pick up underwater sounds, or wings that make it resemble a torpedo. "But we're in a military area," Gong deadpanned, "and we don't want to raise the security level of the York River."

Once in the water, the glider eased forward at a snail's pace on its programmed path, tugging an orange buoy to mark its route, before diving to its programmed depth of 10 meters.

These gliders can descend hundreds of meters, Gong said, while some can dive to a depth of 1,000 meters. They're battery-powered, and on an alkaline battery pack can travel about 400 miles for up to a month, at a speed of about 1 knot. On a lithium pack, a glider can cross the Atlantic.

Gong has already used gliders in the Arctic as part of a two-year project in the Chukchi Sea off Alaska, according to VIMS.

More recently, he said his studies have focused on the Mid-Atlantic Bight, an offshore coastal region with a complex topography of canyons and circuitous shoreline that affect the area's biology, chemistry, geology and fisheries.

Stars to the sea
Also aboard the Alliance schooner were two dozen paying guests who were curious to witness the deployment and learn about the glider's scientific and environmental potential.

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Author:Tamara Dietrich