Breakdown: Saildrones dispatched by NOAA to probe the engine of El Niño in equatorial Pacific

“Remotely piloted, long-range uncrewed surface vehicles open a new era of ocean observation”

Two orange, wind-powered robots sailed out of Honolulu harbor, Hawaii on Aug. 21 bound for a stretch of open ocean 1,500 miles south, according to a report released by NOAA on Sept. 3.

Their mission: Study the beating heart of a building historic El Niño, one NOAA scientists believe has better-than-even odds of becoming the strongest on record since 1950.

The two Saildrone Explorer vehicles that left in late August are the second half of a four-drone fleet NOAA’s Pacific Marine Environmental Laboratory sent out over the past month.

Here’s a breakdown about the saildrones’ mission:

The core news:

• Four Saildrone Explorer uncrewed surface vehicles departed Honolulu in two waves (first group the week of Aug. 14, second pair on Aug. 21), bound for the equatorial Pacific.
• It’s a four-month, roughly 6,000-mile round-trip mission run by NOAA’s Pacific Marine Environmental Laboratory (PMEL).
• They’re headed about 1,500 miles south to the center of the developing El Niño, where heat that had been pooled in the western Pacific has shifted east and is now venting into the atmosphere.

Why now, the framing NOAA itself is using:

• Michael McPhaden,  former PMEL senior scientist, now working with CICOES, said this is “a monumental El Niño is knocking at the door” and this mission exists specifically to document a potentially historic event up close.
• This is explicitly labeled an Eastern Pacific-type El Niño (warming concentrated off South America), the type most associated with major downstream effects like Australian drought and potentially heavy U.S. Southern-tier rainfall and/or flooding.

What the drones actually do:

• Take readings at one-minute intervals, filling in gaps between existing buoys/floats in the Tropical Pacific Observing System (TPOS).
• Map the sharp temperature “fronts” between warm tropical water and cooler water to the east.
• Two of the four carry specialized CO2 sensors, which measures ocean-atmosphere gas exchange. All four vehicles carry current-profiling sonar, which measures water movement in the top 250 feet.
• PMEL Oceanographer Meghan Cronin makes the case for why this beats satellites alone, saying “satellites are great for giving you wide-area coverage, but you still want to put a thermometer in the water to make sure you’re getting an accurate measurement.”

The bigger-picture pitch:

• Historically, getting instruments into the middle of the ocean meant months of planning and an expensive, crewed research vessel. Saildrones (wind and/or solar powered with no crew) cut that cost dramatically and can run for months unattended.
• Part of the data feeds NOAA’s real-time global weather forecast models directly (via the Global Telecommunication System), not just after-the-fact research.

“Remotely piloted, long-range uncrewed surface vehicles open a new era of ocean observation,” Dongxiao Zhang, lead PI of this project at CICOES said. “By targeting areas where data are most needed to improve our understanding and forecasts of high-impact, rapidly developing air-sea processes like this El Niño, that will have profound effects around the world.”

The remote expedition is being funded by NOAA’s Uncrewed Systems Operations Center, with the team composed of researchers from Pacific Marine Environmental Laboratory (PMEL) and its University of Washington cooperative institute, CICOES, as well as scientists with NOAA’s National Marine Fisheries Service and the National Weather Service’s Climate Prediction Center and National Data Buoy Center.