A mighty predator of the sea, capable of traveling vast distances and diving thousands of feet deep, may become a valuable tool in helping forecast climate change.
In a new study, University of Miami Rosenstiel School researchers found that sensors usually attached to sharks to investigate their behavior can also allow scientists to track temperature changes in parts of the oceans often inaccessible to satellites and drifters pulled by currents. Using mako and blue sharks, among the most nomadic of sharks, scientists were able to fill in data gaps and improve some forecasts by as much as 40%.
”What we ended up seeing is what we're calling model improvements in shallow areas, in the Slope Sea [in the Northwest Atlantic] and along the continental shelf,” said Laura McDonnell, lead author and now a researcher at the Woods Hole Oceanographic Institution.
READ MORE: 'We have a serious problem.' Are mahi fleeing Florida to beat the heat?
Animal oceanographers have been around for decades, collecting data used to look for changes in migration or reproduction in animals as the planet warms. This study marks the first to use that data to model climate as rising temperatures are expected to fuel more disastrous events, from marine heat waves that kill coral to droughts.
”You could imagine we would use a lot of sea critters to have a whole observing network,” said co-author Ben Kirtman, dean of the UM’s Rosensteil School. “You get to double dip. You can augment your system, understand animal behavior and, at the same time, get better understanding of the physical system. So it's kind of a cool idea.”
McDonnell, who focuses on predatory fish and impacts from climate change and fishing, typically tags fish with sensors for studies. But the expense and stress on fish always left her wondering if more could be done with the data she collected.
“It is somewhat of an invasive practice. It's very resource heavy," she said. "You get very cool data that can answer ecological questions, but what else can you use that data for?”
At the time, Kirtman had been chatting with another shark scientist about the potential for mining sensor data for his climate models. Kirtman specializes in more short term climatic changes, which requires even more fine-tuned data.
”The quality of those forecasts are critically dependent on how well we observe the ocean because it's the ocean that has that slow memory that's providing information where you can say something about changes in the statistics of weather, in extreme events,” he said. “Is it going to be a more extreme winter with more snow or something like that? That's really coming from the ocean.”
But there are parts of the ocean that can be hard to measure, he said.
”We have satellite data, which is supposed to give global coverage, but doesn't look into the ocean very well. It just looks at the surface,” he said “We have buoys that sit in a fixed space. We have drifters that are out in the ocean that are going along with currents. But sharks set their own path. They go where the food is, right? So that's another way potentially of observing the state of the ocean.”
To test their theory, Kirtman said they first took existing shark data and combined it with climate data to see if patterns were produced. They wound up discovering that changing migrations for tiger sharks lined up with increases in ocean temperatures.
“Then it just snowballs from there,” he said.
For the study, they needed to first determine where Kirtman’s model lacked data: in the Northwest Atlantic, near New England. Luckily, mako and blue sharks congregate in spring off Cape Cod, making catching and tagging the sharks more doable. Then another colleague hooked McDonnell up with local fishermen to help.
”Local fishermen know these waters like the back of their hands, and they taught us a lot,” she said.
Altogether, they tagged 19 blue sharks and one mako and collected data from 8,200 different points in the ocean when the sharks surfaced and pinged satellites. That trove of information provided a glimpse across thousands of miles between New England and the Caribbean and at depths reaching about 6,500 feet deep.
Kirtman then fed the data into his model and compared forecasts with actual conditions. He found the most improvements in areas of the ocean that are often hard to forecast — near the coasts and ocean shelf. While the study helped prove the validity of the data in the model, he said making it operational and effective will require far more work.
”It was really exciting, but to really rigorously demonstrate that you're significantly improving forecasts, you have to spin that up into a more substantive project,” he said. ”Each time we update the model and update the forecast system, it's two years of work to get it ready.”
For McDonnell, using sharks to improve how fish are managed to keep them healthy as climate change makes their behavior less predictable has a poetic flair.
“Kind of a weird feedback loop of the fish themselves informing the models," she said, "that then help the people who make a living on the water.”
