UAF Deploys CO2-Sensing Underwater Glider
Scientists and industry partners aboard the research vessel Nanuq recover the carbon dioxide-measuring Seaglider after a test dive in the Gulf of Alaska.
Heather McFarland
UAF researchers and their commercial partners are the first US team to measure carbon dioxide in the ocean using a remotely operated underwater vehicle.
Pink Torpedo
Technological limitations restricted research in the past. Ocean moorings gathered data at a single location year-round, or ships sampled along transects for several weeks from spring to fall. Although these tools still provide critical information, large areas of the ocean are not sampled, especially in winter.
A new tool, the 7-foot-long Seaglider, can fill those data gaps. Claudine Hauri, an oceanographer at the UAF International Arctic Research Center, enlisted international commercial partners to integrate a carbon dioxide sensor with an unoccupied water vehicle that can dive up to 1,000 meters and carry out weeks-long missions to remote parts of the ocean in every season.
“My job is to find the compromise between what the scientists want and what the glider can do,” says Ehsan Abdi, an electronics engineer with Advanced Offshore Operations and Cyprus Subsea. He develops, prepares, and operates underwater gliders for long and deep missions.
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April 2024
The integration was no simple task and required specialized skill in mechanical and electronics engineering as well as in materials science. For example, Abdi had to consider how the heavier sensor changed the buoyancy of the Seaglider while moving through the water. He made adjustments using weights and other parts fabricated on a 3D printer.
Meanwhile, Jöran Kemme and his colleagues at 4H JENA Engineering redesigned one of the market’s most precise carbon dioxide sensors for underwater measurements. The new design, called Contros HydroC CO2, is lighter and more compact, yet its precision still requires a larger size and higher power consumption than the sensors a Seaglider usually carries.
“The most exciting thing is seeing such a big and power-hungry sensor go on such a humble and small glider that was not meant to do stuff like this,” Abdi says. “That’s why it’s challenging, and that’s why we’ve had so many problems. But that’s the fun part of it as well.”
Tracking Ocean Acidification
A sea lion at Alaska Sealife Center in Seward watches UAF oceanographer Claudine Hauri making sure the Seaglider is balanced correctly.
Kaiti Grant
Measuring dissolved carbon dioxide is a way to understand the changing acidity of the ocean. Globally, the pH of the ocean is decreasing as carbon dioxide from burning fossil fuels is absorbed by the ocean. Higher acidity affects the ability of marine organisms to build and maintain their shells and may also change the behavior of some fish.
The Gulf of Alaska’s cold waters naturally hold more carbon dioxide, so it only takes a little added CO2 to reach a threshold that puts marine organisms at risk. Melting glaciers that dump freshwater into the ocean can further reduce the number of building blocks available for shells.
Despite the urgent risk to commercial, subsistence, and sport fishing in Alaska, data are lacking to determine the status of ocean acidification around the state.
“In order to understand how the human-made carbon dioxide in the atmosphere changes the oceans, we also need to know how ocean chemistry varies naturally throughout the year,” Hauri explains.
Glide Path
The Seaglider team went to Seward this spring for operational testing before going to sea. Hauri made sure the glider was balanced correctly while swimming in a tank normally meant for sea lions at the Alaska SeaLife Center. At Alutiiq Pride Marine Institute, the team compared measurements taken by the Seaglider to those from instruments used in labs.
The Seaglider took its first ride into Resurrection Bay via the UAF Seward Marine Center’s research vessel Nanuq. In a series of consecutively deeper dives, the team tested the Seaglider’s maneuverability and response to different temperatures and depths and compared its ability to measure carbon dioxide to ship-based sensors.
Through many hours bobbing in Resurrection Bay adjusting sensors, reprogramming the Seaglider, and examining real-time data, the team was driven by the promise of better carbon dioxide measurements in Alaska’s oceans and globally. They plan to make the details of the sensor integration available to others so teams around the world can study ocean acidification more efficiently and develop more strategic and innovative responses.
“I’m excited by the possibility of having a whole fleet of these seagliders continuously measuring CO2. It’s important to have people from all around the world working on this, especially because it is a worldwide issue,” Kemme says.
Other members of the team include Andrew McDonnell, Dan Hayes, Jack Triest, and Brita Irving. The work was funded by the National Science Foundation and National Oceanographic Partnership Program.
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