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White sharks aren’t supposed to be social. Yet researchers have found that the notoriously solitary predators regularly gather together at one particular spot in the Pacific Ocean. There they perform a mysterious ritual: diving down almost 500 yards and then resurfacing, hundreds of times a day. In hopes of gaining some insight into this puzzling behavior, researchers have deployed two autonomous robots called Saildrones to gather crucial data to build a better picture of the region’s ecosystem. Saildrones aren’t the first autonomous devices to be employed in marine science, but since their 2014 release they have been lauded for their utility. These boats are much less expensive to operate than ships, and because they’re wind- and solar-powered they can travel uninterrupted for months. Their 23-foot frames are also small enough to pass through sensitive ecosystems without scaring wildlife. Globally, Saildrones are helping scientists capture a more complete picture of some of the world’s most remote waters, from the Pacific to the Arctic.
The regular patrons of the White Shark Café have had some company lately.
In March, two autonomous robots, called Saildrones, departed from California en route to the “Café,” a mysterious stretch of water in the middle of the Pacific Ocean where the sharks are known to congregate. This week, they were joined by a ship carrying 14 scientists and a vast array of ecological monitoring instruments. Researchers know little about this region – and why it attracts the massive predators – but these reddish-orange sailboats are a crucial step toward learning more.
Their collective journey began with a discovery by Barbara Block, a biologist at the Hopkins Marine Station of Stanford University in Pacific Grove, Calif. Dr. Block’s team had been tagging white sharks for seven years when they noticed something peculiar in 2006. For several months, most of these sharks abandoned the coastline for the open ocean. But they weren’t just dispersing randomly into the Pacific: They were headed somewhere specific, a patch of ocean about halfway between Hawaii and California.
Once there, the sharks behaved in profoundly unusual ways, diving down almost 500 yards and then resurfacing – and doing it hundreds of times a day. Researchers first called the region an “offshore focal area.” Since 2009, Block and her colleagues have simply called it the White Shark Café.
While satellites can record images of the Café – which is thousands of miles away from Block’s office in Monterey, Calif. – from above, their radio waves can’t penetrate below the surface. So what the sharks are doing remains unclear. “It’s as if they’re searching for something, and we’re sitting back here trying to figure out what it is they’re searching for. Is it food? Is it each other?” Block asks.
Those questions may soon have an answer. The two Saildrones are equipped with a number of sensors, including an echosounder, which sends pulses of energy 500 yards into the water column and records every organism in range. Having supplied data for weeks, the drones are now helping identify researchers’ next steps.
“I love the idea of this presence. It’s almost like having your own instruments there,” Block said before departing. “When it’s rough out there, it’s really nice that I’ve got these quiet Saildrones showing me what it used to take a whole ship and weeks of time and effort to do.”
Saildrones aren’t the first autonomous devices employed in marine science, but since their 2014 release they have been lauded for their utility. These boats are much less expensive to operate than ships, and because they’re wind- and solar-powered they can travel uninterrupted for months. Their 23-foot frames are also small enough to pass through sensitive ecosystems without scaring wildlife. Globally, Saildrones are helping scientists capture a more complete picture of some of the world’s most remote waters.
Since 2015, Jessica Cross has been using Saildrones to investigate one particularly inaccessible region: the Arctic. Last year, Dr. Cross, a research oceanographer at the National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory in Seattle, helped deploy three Saildrones in collaboration with NOAA's Alaska Fisheries Science Center. Two drones traversed the Chukchi Sea, northwest of Alaska, to sample water carbon concentrations while another drone monitored pollock and fur seal populations in the Bering Strait. Researching along icy coasts was an ideal spot for the autonomous vessels, says Cross. “Ice is unpredictable, and you need a really heavy ship in order to safely navigate that area. Even though ships are one of the most powerful oceanographic tools that we have, it can be expensive,” she says.
And when surveying easily spooks animals, keeping a low profile can be critical to getting accurate data. “Ships are noisy ... they turn up a lot of water and so what we’re noticing ... is that we scare less fish with the Saildrone. So we get a slightly different count of how many fish are in the water and what level or what depth of the water they’re hanging out at,” she says.
The boats are so discreet that wildlife sometimes feel comfortable approaching them. Last summer, a fur seal hopped aboard one of the Saildrones in the Chukchi Sea and rode it for hours before hopping off into a phytoplankton bloom. “It could have been pure coincidence or it could have been like he was taking a cab, thinking, ‘I can smell that there’s food over there. You look like you’re headed in that direction. I’m going to go with you,’ ” Cross says. “Those are the kinds of things that we’re seeing now that we wouldn’t have had the opportunity to see before.”
Saildrones aren’t just covering new ground; they’re raising new possibilities for oceanographic research. This month, two drones are expected to return from a seven-month excursion into the Pacific Ocean to collect climate data, including wind direction, air pressure, and ocean currents. The boats are being tested to determine their potential in supplementing NOAA’s network of Tropical Atmosphere Ocean buoys and moorings.
“We are integrating all of these different measurements ... to come up with the global maps of the best representation of what is actually out there,” says Meghan Cronin, lead researcher for the Ocean Climate Stations group at PMEL.
If the data the Saildrones bring back matches the buoy measuring system, the drones could help climate scientists better predict and prepare for the extreme weather conditions that El Niño brings.
“The strength of a Saildrone is that it moves and it can do these adaptive surveys, and it can cross fronts and see how abrupt these fronts are,” says Dr. Cronin. When weather in the Pacific changes rapidly, the moorings, stationed nearly 1,000 miles apart, can only roughly render the shape of a moving front.
The drones could enhance future climate modeling, but Cronin doesn’t foresee a future in which they are the only tool oceanographers use.
“Each of these platforms has its own strength but also its weakness, and so you have to fill in some of the weaknesses with strengths of the other platforms,” she says.
That multiplatform experimentation is central to Block’s approach as she and her colleagues maneuver the White Shark Café. The Saildrones are just the first step in the team’s barrage of data-sampling devices. About 30 sharks are also wearing acoustic tags that send locational updates. Another autonomous device, known as a Slocum Glider, will travel up and down the water column and follow the sharks’ rapid diving. And a biochemical instrument called a nanopore processor will scour the water for DNA left behind by fish and other organisms.
Seeing the sharks – many of whom scientists have given names like “Tiny,” “Heffalump,” and “Shawshark Redemption” – so far from where they’re normally spotted is a thrill. But the goal is to build a comprehensive vision of the subaquatic environment. “We’re going to be asking in the simplest form who is in the ecosystem,” she says.
As the technology progresses, the Saildrone will likely continue to adapt and fill scientific niches, says James Bellingham, director of the Center for Marine Robotics at the Woods Hole Oceanographic Institution in Woods Hole, Mass.
“As a technologist I create one of these systems and I’m disappointed if the only thing they’re ever used for is the thing that I thought of when I built the robot,” he says.
But even with the Saildrones’ rapid advances, some design elements seem unlikely to change, at least for now. “It’s kind of interesting because we’ve known about powering things by wind for millennia,” says Dr. Bellingham. “In a way it’s one of these back-to-the-future things.”