“Dead Zones” are growing off the West Coast and elsewhere, affecting fisheries and the ecosystem. Dead zones are areas in the ocean that have become so oxygen-starved that most marine animals flee the area or die (webcast).
To monitor the impact of this phenomena, traditional instruments deployed by ships can cost $20,000 per day to deploy and can only operate for a limited time. Satellites can monitor global ocean phenomena over a longer time, but their resolution is limited and only the ocean surface can be observed.
Since 2006, a research team co-led by Jack Barth and Kipp Shearman of Oregon State University (OSU) has been deploying unmanned robotic gliders throughout Oregon’s coast.
“The technology is pretty incredible,” said Jack Barth, a professor of oceanography at OSU. “We can literally program them to run underwater for three to five weeks, cruising from near-shore to over the continental slope and back while taking all kinds of sophisticated measurements. Each of these gliders can measure the water’s oxygen concentration, temperature, salinity, density, and chlorophyll content.
Each glider may dive down to 200 meters. But “every six hours, each glider must pop back up to the surface and call in to a computer at our lab via Iridium satellite phone and send home the data,” says Barth. They provide around-the-clock, real-time data on subsurface ocean properties that would otherwise be unobtainable.
Their research revealed: 1) Oregon’s coastal dead zones are formed by wind-driven upwellings of low-oxygen waters that naturally occur in deep, offshore waters; and 2) these low-oxygen waters may be expanding towards shore because of changes in wind and oceanic circulation patterns.
But the gliders are not driven by propellers. Rather, they are driven by buoyancy changes that require relatively little battery power. To rise, a glider expels water and thereby increases its buoyancy; to sink, a glider draws in water and decreases its buoyancy. The glider’s vertical motion is translated into forward motion by small wings on its sides. “Each glider operates much like a sailplane in the atmosphere,” explains Barth.
Gliders were first conceived by Douglas Webb, the founder of Webb Research and a former researcher at the Woods Hole Oceanographic Institution (WHOI). Teledyne Webb Research has delivered 124 Slocum gliders to 40 user groups, which have collected data over 120,000 km of the world’s oceans.
So far, OSU’s fleet of gliders has cumulatively travelled more than 25,000 horizontal kilometers, which is equal to travelling about 70 percent of the way around the globe.
“In five weeks you’ve saved $600,000,” Barth said. “And no one gets seasick.”
Rutgers University launched a similar robotic glider off the coast of New Jersey on April 27, 2009, on an eight-month voyage. Rutgers hoped their autonomous underwater vehicle would be the first underwater robot to cross the Atlantic Ocean.
Rutgers has a distributed control room (pdf) that integrates data from instruments received by a 900 MHz FreeWave Radio (with a 60 mile range) and an Iridium data link and puts them onto their web site in real-time.
Eleven NASA and NOAA scientific instruments are integrated into the Global Hawk UAV. Solar-Electric UAVs hold the potential for lingering on-site for months or years. High Altitude, Long Endurance (HALE) UAVs generally fly well above the jet stream.
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