Scientists send glider drone into Gulf of Alaska to learn more about ocean's CO2 levels

Our planet is changing. So is our journalism. This story is part of Our Changing Planet, a CBC News initiative to show and explain the effects of climate change and what is being done about it.

In the cold, choppy waters of Alaska's Resurrection Bay, all eyes were on the grey water, looking for one thing only.

It wasn't a spout from humpback whales that power through this scenic fjord, or a sea otter lazing on its back, munching a king crab.

Instead, everyone aboard the Nanuq, a University of Alaska Fairbanks research vessel, was looking where a 1.5-metre long, bright pink underwater sea glider surfaced.

The glider — believed to be the first configured with a large sensor to measure carbon dioxide levels in the ocean — had just completed its first overnight mission.

Designed to dive 1,000 metres and roam remote parts of the ocean, the autonomous vehicle was deployed in the Gulf of Alaska this spring to provide a deeper understanding of the ocean's chemistry in the era of climate change.

The research could be a major step forward in ocean greenhouse gas monitoring because, until now, measuring CO2 concentrations — a quantifier of ocean acidification — was mostly done from ships, buoys and moorings tethered to the ocean floor.

Oceans have done humans a huge favour by taking in some of the carbon dioxide emitted by the burning of fossil fuels. Otherwise, there would be much more in the atmosphere, trapping the sun's heat and warming the Earth.

"But the problem is now that the ocean is changing its chemistry because of this uptake,'' said Claudine Hauri, an oceanographer with the International Arctic Research Center at the University of Alaska Fairbanks.

The enormous amount of data collected is being used to study ocean acidification that can harm and kill certain marine life.

Rising acidity of the oceans is affecting some marine organisms that build shells. This process could kill or make an organism more susceptible to predators.

Lab in a tube, on a glider, under the sea

Over several weeks this spring, Hauri and her husband Andrew McDonnell, an oceanographer with the College of Fisheries and Ocean Sciences at the university, worked with engineers from Cyprus Subsea Consulting and Services, which provided the underwater glider, and 4H-Jena, a German company that provided the sensor inserted 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 each mission, the crew aboard the Nanuq — the Inupiat word for "polar bear" — pull the 60-kilogram glider back on board. The sensor is then removed from the drone and rushed to the ship's cabin to upload its data.

The sensor, which measures around 30 centimetres by 15 centimetres is a sort of laboratory in a tube, with pumps, valves and membranes moving to separate carbon dixoide from seawater. It analyzes CO2 and logs and stores the data inside a temperature-controlled system. 

"I think [Hauri] is one of the first persons to actually utilize [gliders] to measure CO2 directly, so that's very, very exciting,'' said Richard Feely, the National Oceanic and Atmospheric Administration's senior scientist at the agency's Pacific Marine Environmental Laboratory in Seattle.

The challenge, Feely said, is to make the measurements on a glider with the same degree of accuracy and precision as tests on board ships.

"We need to get confidence in our measurements and confidence in our models if we are going to make important scientific statements about how the oceans are changing over time and how it's going to impact our important economic systems that are dependent on the food from the sea,'' he said, noting that acidification impacts are already seen further down the West Coast 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 but found 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, glider program manager with the Ocean Frontier Institute at Memorial University of Newfoundland, said in an email.

The two teams are "using two different types of sensors to solve the same issue, and it's always good to have two different options," Hauri said.

Wealth of data

There is no GPS unit inside the underwater autonomous drone. Instead, after being programmed, it heads out on its own to cruise the ocean according to the navigation directions — knowing how far to go down in the water column, when to sample, and when to surface and send a locator signal so it can be retrieved.

As the drone tests were underway, the U.S. research vessel Sikuliaq, owned by the National Science Foundation and operated by the University of Alaska Fairbanks, conducted its own two-week mission in the gulf to take carbon and pH samples as part of ongoing work each spring, summer and fall.

Those methods are limited to collecting samples from a fixed point, while the glider will be able to roam all over the ocean and provide 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 across the globe, providing a real-time glimpse of current conditions and a way to better predict the future.