While us average folks enjoyed the incredible footage captured by a floating drone in the midst of a Category 4 hurricane, scientists were geeking out on the data. And now, they’re ready to share some of the results and insights into how the fiercest storms on Earth can gain strength.
The findings were presented at the American Geophysical Union’s annual meeting as part of a series of talks wrapping up the year in research for Saildrone. The company has worked closely with federal scientists to deploy its fleet of seafaring drones from the tropics to the poles. Among their most daring feats in 2021 was sending one of their autonomous vehicles into the maw of Hurricane Sam.
The powerful storm mercifully stayed far out to sea for most of its life, though its outer edges did glance off Bermuda. But Saildrone 1045 didn’t need to be close to shore to operate; the vehicles can traverse basically any patch of sea. And researchers steered it right into Sam on a late September day, as the storm was undergoing rapid intensification, a meteorological term for when storms see winds increase at least 35 mph (56 kmh) in 24 hours. The trip represented a first for Saildrone vehicles, which have never entered a storm that fierce.
“I told everyone, ‘If this vehicle can survive a hurricane, then this would be a big success story,’” Chidong Zhang, director of the Ocean Climate Research Division of the federal Pacific Marine Environmental Lab, said in a statement. “The whole mission exceeded my expectations.”
The drone sent back unreal images as it was heaved about in towering waves. The research team reported that it flipped over a few times as it slid up and down the face of 50-foot (15-metre) swells. It not only survived. It ✨thrived,✨ transmitting images and data to the team on land.
Some of that data shocked researchers and made them wonder if an instrument had failed. The Saildrone data showed an obstinate pool of warm water clinging to the surface, giving Sam even more fuel to power up. Hurricane winds usually churn up the ocean, drawing cooler water up from below the surface. That mixing can help slow down hurricane intensification.
Not only was the water warm under Sam’s violent thunderstorm, but it was also less salty. Using data from a buoy in the area, researchers were able to confirm the instruments on the drone were working just fine. They also gleaned the likely source: the Amazon River. Ocean currents transported the warm, less salty — and thus, less dense — water into the midst of the Atlantic, where it acted like a lid on the ocean. Researchers also deployed underwater drones known as gliders and Hurricane Hunter aircraft along with the Saildrones, adding to the pile of data.
The scientists will continue to comb over the data in the coming months, but the preliminary findings show how natural processes can influence hurricanes and even build on climate change’s effects. Other research has shown how the ocean is becoming more stratified due to surface heating and generally creating an environment where storms can intensify more rapidly. (It’s also upping the odds of prolific rainmaking hurricanes and tropical storms and raising sea levels, so really there’s no shortage of woes.)
“I like to look at it as [global warming is] increasing the maximum intensity that a hurricane can reach,” Greg Foltz, a physical oceanographer at the federal Atlantic Oceanic and Meteorological Laboratory, said in a statement. “It’s not that every hurricane will increase in intensity, it’s that under the right conditions, a hurricane that would normally reach a wind strength of 241 km/h could reach 257 km/h. It’s creating the potential to have stronger storms.”
Getting a view from inside a hurricane, even one being influenced by a natural heat source, could provide researchers valuable insights for future forecasts. The Saildrone research team also sent their unmanned vehicles into five other tropical cyclones in the Atlantic this year in order to understand rapid intensification. Now, it’s about making the most of that data so we can get ready for whatever the future holds.