Sailboat drones: The ocean drones investigate climate change data

Ocean Data Platform powered by a fleet of unmanned surface vehicles (USVs) called Saildrones. The use of Saildrones will complement and support the limited manned research cruises in the Arctic to greatly increase domain awareness and enhance the collection of critical data in a rapidly changing environment and help scientists measure and understand Arctic warming, sea ice loss and ecosystem change.

These sailboats, outfitted with sensors to probe the ocean, are semiautonomous drones, developed by Saildrone, a marine tech startup based in Alameda, California, in close collaboration with the National Oceanic and Atmospheric Administration (NOAA) in Washington, D.C. The voyage is the longest test for the drones and also the first science test in the Pacific—an important step in showing that they could replace an aging and expensive array of buoys that are the main way scientists sniff out signs of climate-disrupting El Niño events.

After World War II, most sea surface data were collected from ships. Then came buoys and satellites. Now, NOAA scientists want to send in the drones. Within the next decade, hundreds or even thousands of solar- and wind-powered drones could roam the world’s oceans, using satellites to relay information gathered from the sea surface and the air above.

The drones can’t come too soon for scientists who study the El Niño–Southern Oscillation, a set of shifting global temperature and rainfall patterns triggered by warm surface waters that slosh back and forth across the equatorial Pacific every few years. Since the 1980s, NOAA has supported a grid of buoys, moored to the Pacific sea floor, called the Tropical Atmosphere Ocean (TAO) array, to study and forecast these swings. Its success led to similar arrays in the Indian and Atlantic oceans.

But earlier this decade, the TAO array had a near-death experience. The marine growth on buoys and their moorings are fish magnets, which makes them a magnet for fishers as well, causing the distinctive TAO grid to appear on maps of global fish catches. As fishers dragged the buoys aside for easy pickings, they damaged them, and maintenance work began to pile up. Meanwhile, budget cuts and the soaring expense of operating research ships meant few new buoys were deployed.

Ultimately, Congress restored funding for the TAO array, which costs about $10 million a year. But now Japan, which maintains a complementary array in the western Pacific called the Triangle Trans-Ocean Buoy Network, has pulled out almost all of its buoys because of limited funds and a lack of ship time to maintain them, degrading El Niño measurements once again. The crises prompted NOAA and others to look for a more sustainable system to deliver El Niño warnings, which help agencies plan for the heavy rains and droughts that follow in its wake.

Since then, Saildrone has worked with PMEL scientists to rig the boats with sensors and test their limits. In 2015, they survived 40-knot winds during a 3-month foray into the Arctic to assess marine life. That success encouraged scientists to mull whether the drones could help anchor observations in the Pacific. Conceivably, the drones could sail in circles around a virtual mooring point, or run other preplanned patterns, before returning to port every year for cleaning—no ships necessary. The drones could be cheaper, too. Saildrone charges $2500 a day per drone to collect data, whereas ship time can cost $30,000 or more per day.

In addition to temperature, wind, and solar radiation data, the Pacific saildrones are measuring how the ocean and air exchange gases like carbon dioxide and oxygen, and they are using Doppler instruments to gauge currents coursing up to 100 meters below the surface. These sensors could reveal patterns that help explain why the tropical Pacific emits carbon dioxide, rather than absorbing it like most of the rest of ocean. Arrays like the TAO will continue to be important, Cronin says. But she foresees the emergence of a cheaper, more resilient oceanographic backbone.

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