Scientists use gliders to measure Gulf ‘dead zone’
A team of Texas scientists this week will release four torpedo-like, remotecontrolled gliders into the northern Gulf of Mexico to measure oxygen levels, bringing researchers closer to a long-cherished goal of broadly monitoring the health of the world’s oceans.
“The community of scientists that study oceans have long dreamed of deploying these silent sentinels of the sea,” said Steve DiMarco, an oceano grapher at Texas A&M University.
On Tuesday, DiMarco, aboard the research vessel Manta, departed Pelican Island in Galveston Bay on his annual June cruise to monitor the northern Gulf for hypoxia, or low levels of oxygen in the water that are harmful to marine life.
As part of the cruise, he will deploy four of the gliders, each costing about $200,000, which are autonomous vehicles that measure temperature,
salinity and oxygen levels. Traveling at a speed of about 8 mph, they can go as deep as 1,000 feet.
The gliders, packed with D-cell and lithium batteries, will stream their data back to Texas A&M. Those batteries, which provide all the onboard power, will last about a month before the gliders must surface to replace battery packs.
DiMarco typically cruises the northern Gulf twice a year — for a week in June and August — to measure hypoxia. In deploying the gliders this summer, he hopes to test how accurate their measurements are compared to traditional, shipboard instruments.
“In the last few years, this glider technology has really matured,” he said. “This is their first big test here.”
NOAA funds DiMarco’s cruises, and those of other scientists, to keep track of hypoxia, an environmental problem triggered largely by the widespread use of fertilizers in the Midwest, which drain into the Gulf via the Mississippi River.
But the agency has said it wants scientists to adopt more efficient and less expensive ways to survey the so-called “dead zone,” which has generally increased in size during the last two decades. Last year, it measured nearly 6,000 square miles in extent, or about the size of Connecticut. DiMarco said a typical 1,200-mile cruise, including boat rental and personnel time, costs about $100,000.
Texas A&M believes this technology represents the future of ocean surveillance. The university has created a glider lab where it has experimented with the technology, and from there “full-time glider pilots” will control the four Gulf gliders from desktop computers.
In recent years the gliders, manufactured by Teledyne Webb Research, have been used for a variety of ocean-going tasks. They provided surveillance in the wake of the massive BP oil spill and gathered details about ocean conditions as Hurricane Irene bore down on the East Coast in 2011.
One issue for the Texas researchers is using the gliders along the continental shelf, where hypoxia is often most problematic. Between the 7,000 piers, docks and other structures along the Texas and Louisiana coasts as well as fishing vessels, there are a lot of objects to avoid.
“It’s a fairly big deal for us to fly them on the continental shelf, which is very shallow,” DiMarco said. “We’re really going to be pushing this technology to its limits.”
Oceanographers have been thinking about using technology such as gliders as far back as the 1980s, when it was seen as futuristic and, by some, unrealistic.
In a seminal 1989 essay written in Oceanography, Henry Stommel asserted, “The payoff in increase of knowledge is often greatest the more unconventional the idea, especially when it conflicts with collective wisdom.”
Now there’s the potential to not only measure hypoxia but identify and track other pollutants, measure ocean temperatures and essentially revolutionize our understanding and monitoring of the oceans.
Of course, DiMarco realizes that if he’s successful, one day in the not too distant future, his cruising days may be over. And he’s OK with that.
“This,” he said, “is the future.”