SEWARD, Alaska — In the cold, choppy waters of Alaska’s Resurrection Bay, all eyes were on the gray waters, looking for just one thing.
It was not the spout of humpback whales drifting through this scenic fjord or a sea otter lounging on its back munching on a king crab.
Instead, everyone watched aboard the Nanuq, a University of Alaska Fairbanks research vessel, where a 5-foot (1.52-meter) long, bright pink underwater sea glider surfaced.
The glider — believed to be the first configured with a large sensor to measure ocean carbon dioxide levels — had just completed its first nighttime mission.
The autonomous vehicle is designed for diving 1,000 meters and roaming remote parts of the ocean. It was deployed in the Gulf of Alaska this spring to help better understand ocean chemistry in the age of climate change. The research could be a major step forward in monitoring ocean greenhouse gases, as the measurement of CO2 concentrations – a quantifier of ocean acidification – has until now been done mainly from ships, buoys, and moorings tethered to the ocean floor.
“Sea acidification is a process by which humans release carbon dioxide into the atmosphere through their activities of burning fossil fuels and changing land use,” said Andrew McDonnell, an oceanographer in the College of Fisheries and Ocean Sciences at the University of Alaska Fairbanks.
Oceans have done humans a great favor by absorbing some of the CO2. Otherwise, there would be much more in the atmosphere, trapping the sun’s heat and warming the Earth.
“But the problem now is that the ocean is changing its chemistry because of this recording,” said Claudine Hauri, an oceanographer at the International Arctic Research Center at the university.
The vast amount of data collected is used to study ocean acidification that can harm and kill certain marine animals.
The rising acidity of the oceans affects some marine organisms that build shells. This process can kill an organism or make it more susceptible to predators.
This spring, Hauri, and McDonnell, who is married, spent several weeks working with engineers from Cyprus Subsea Consulting and Services, which supplied the underwater glider, and 4H-Jena, a German company that provided the sensor to plug into the drone.
Most days, researchers took the glider farther and farther into Resurrection Bay from the coastal community of Seward to conduct tests.
After its first nighttime mission, a crew member spotted it bobbing in the water, and the Nanuq — the Inupiat word for polar bear — backed up to let people pull the 130-pound (59 kilograms) glider onto the ship. After that, the sensor was removed from the drone and rushed into the ship’s cabin to upload the data.
Think of the foot-tall (0.30 meters) sensor with a diameter of 15.24 centimeters like a laboratory in a tube, with pumps, valves, and membranes that move to separate the gas from the seawater. It analyzes CO2 and logs and stores the data in a temperature-controlled system. Many of these sensor components use battery power.
Because it is the industry standard, the sensor is the same as on any ship or laboratory that works with CO2 measurements.
Hauri said using this was “a huge step to accommodate such a large and energy-hungry sensor, so what’s special about this project.”
“I think she’s one of the first to actually use (gliders) to measure CO2 directly, so that’s very, very exciting,” said Richard Feely, senior scientist with the National Oceanic and Atmospheric Administration at the Pacific Marine Environmental Laboratory. from the Seattle agency He said Hauri graduated in 2007 when she accompanied him on the first acidification cruise he ever led.
The challenge, Feely said, is to make the measurements on a glider with the same degree of accuracy and precision as tests aboard ships.
“We need to gain confidence in our measurements and confidence in our models if we are to make important scientific statements about how the oceans are changing over time and how this will affect our important economic systems that depend on the food from the sea”, he said, noting that acidification effects are already being seen in the Pacific Northwest on oysters, Dungeness crabs, and other species.
Researchers in Canada had previously attached a smaller prototype CO2 sensor to an underwater drone in the Labrador Sea. Still, they found that it did not yet meet the targets for ocean acidification observations.
“The tests showed that the glider sensor worked in a remote, harsh environment but needed more development,” Nicolai von Oppeln-Bronikowski, the Glider Program Manager at the Ocean Frontier Institute at the Memorial University of Newfoundland, said in an email.
The two teams “just use two different types of sensors to solve the same problem, and it’s always good to have two different options,” Hauri said.
There is no GPS unit in the autonomous underwater drone. Instead, once programmed, it sets out to navigate the ocean according to its navigational cues – knowing how far to descend in the water column, when to sample, and when to surface and send a positioning signal. Send it for collection.
While drone tests were underway, the US research vessel Sikuliaq, owned by the National Science Foundation and operated by the university, conducted its own two-week mission in the Gulf to take carbon and pH samples as part of ongoing work every spring, summer, and fall.
Those methods are limited to collecting samples from a fi,xed point allowing the glider to roam the entirand e ocean, providing researchers with a wealth of data on the ocean’s chemical makeup.
The vision is to one day have a fleet of robotic gliders operating in oceans around the world, providing a real-time glimpse of current conditions and a way to better predict the future.
“We can … understand much more about what’s going on in the ocean than we’ve been before,” McDonnell said.
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