Saildrones are studying climate change on the seas
Researchers in the Bering Sea are using autonomous sailing vessels, powered by the sun and wind, to collect data on ocean conditions, fish and marine mammals in a rapidly changing, biologically rich area.
AT THE END of May, two 6m (20ft)-tall orange autonomous sailing vessels, each with a vertical carbon-fiber wing, were set loose in the Bering Sea from a dock in Dutch Harbor, Alaska. Each of the vehicles had been programmed with a single instruction: to sail hundreds of kilometers into the southeastern Bering Sea to a bright yellow, donut-shaped buoy named “Peggy.”
By June 3, 11 days into the trip, the pair of Saildrones, as they’re called, had traveled more than 200 nautical miles through cold and choppy seas. En route, Saildrone 128 snapped pictures, including one of its companion Saildrone 126 floating on the dark blue water, one of a purple sky and one of a crooked sunset. They had also collected hundreds of thousands of data points, sampling the water and the air, and listening for sea life.
The solar- and wind-powered vehicles, built by a California company, are part of an ocean research program that aims to expand researchers’ understanding of the physics, chemistry and biology of the Bering Sea, and how it is changing. “They can provide a new platform that scientists can use to remotely study the oceans in ways that were not possible before,” said Chris Sabine, director of the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Lab (PMEL), at a press conference.
The Bering Sea is a wide wedge of ocean, sandwiched between Alaska and Russia, and bounded to the south by the sweeping arc of the Aleutian Islands. It holds some of the world’s most biologically productive waters, abundant in food for the ribbon seals, gray whales and tufted puffins that feast there in the spring. It also produces almost half of the fish and shellfish caught in the U.S. Salmon, king crab and the biggest catch of all, Alaska pollock, pull in more than $1 billion a year.
But the Bering Sea is showing strong signs of climate change. The sea ice doesn’t reach as far south as it once did and the seasonal melt is starting earlier in the spring. The sea is also becoming more acidic. Cold water is especially good at absorbing carbon dioxide from the atmosphere, nudged along by glacier melt and river runoff.
“The Bering Sea is very sensitive to climate change, and how its ecosystem responds to the reduction of sea ice is an important question that we are investigating,” said Phyllis Stabeno, a physical oceanographer at PMEL in Seattle, Washington.
Each Saildrone carries a payload of sensors that measure wind speed, air temperature and humidity, ocean surface temperature, water temperature, salinity, dissolved oxygen and fluorescence (an estimate of how much phytoplankton is in the water). They also hold acoustic fish finders to look for pollock and passive acoustic monitors that listen for the distinctive shotgun pop and up-call vocalizations of the endangered North Pacific right whale. Each vessel records up to 86,400 measurements a day – almost one every second. Some are transmitted through a satellite link to researchers, others are archived to an onboard hard drive for later retrieval.
The Saildrones appeal to researchers because they can cover large areas and collect near real-time oceanographic data in a more cost-effective way. The alternative – the way most research on the area has been done up until now – is to spend days at a time on a ship, such as the 63m (208ft)-long Oscar Dyson, a research vessel operated by NOAA.
But ship time is costly. Research onboard the Dyson runs at $20,000–25,000 per day, compared to the $1,000–2,000 per day it costs to operate a Saildrone. “These aren’t going to replace ships, but they’re going to supplement and be a strong partner in the program,” said Doug DeMaster, science director of the Alaska Fisheries Science Center.
Studying the North Pacific whale is a good example of how the drones can complement ship-based research, said DeMaster. Although they once numbered in the tens of thousands, the whales were nearly hunted to extinction.
“They were knocked down to less than 100 animals in the eastern North Pacific, and there are probably now fewer than 50,” said DeMaster. Trying to find them in the eastern half of the sea – an area larger than the state of California – from a cruising ship is “very inefficient,” he said. “At this point we don’t even know what neighborhood they’re in.” If a Saildrone hears one, it will give researchers some clues about where these elusive whales might be found on the next research cruise.
The passive acoustic monitors on board the Saildrones will record marine mammal sounds throughout the mission, said Jessica Crance, a marine mammal biologist with the Alaska Fisheries Science Center. “By integrating the Saildrone into our research, we can cover a large area that we have not been able to cover in over a decade,” she said.
As the air and water sensors collect environmental data, the Saildrone will also use an active acoustic pinger – a fish finder – to gather information about pollock. In addition to being important to commercial fishermen, pollock are the primary food for northern fur seals, a species whose 30-year decline is poorly understood.
The Saildrones will steer back to Dutch Harbor and be picked up in September, after logging thousands of kilometers through the Bering Sea. Despite the harsh weather conditions – 80-knot winds, 12m (40ft) seas and near-freezing temperatures – they’re expected to do well. Last year, the same Saildrone pair spent three months touring the Bering Sea. “It’s a pretty brutal environment,” said DeMaster. “But so far, the technology has kept up.”