by Joe Selmont, UW CICOES

On November 22, 2024, two Saildrones rendezvoused with three Wirewalkers and a Seaglider along the equator in the middle of the Pacific Ocean, about 1,700 miles southeast of Hawai‘i. Their meeting set into motion a carefully planned choreography: six autonomous machines moving in coordination as they rode the waves eastward.

No, this wasn’t a scene from a new Star Wars movie; Saildrones, Wirewalkers, and Seagliders are three different types of scientific research vehicles known as Uncrewed Surface Vehicles, or USVs. Each of these USVs was collecting data essential to understanding the coupled ocean-atmosphere system.

Deployed as part of Mission 7 of the Tropical Pacific Observing System (TPOS), the Saildrones had already traveled nearly 3,000 miles over the previous two months. They sailed along at roughly two nautical miles per hour, adjusting course in response to occasional commands transmitted by human pilots, who were safe and sound back on dry land. By the time they reached the equatorial rendezvous point, the Saildrones had already gathered a rich set of observations.

“These USVs, carrying a whole suite of meteoro-logical, oceanic and biogeochemical sensors, allow us to do adaptive sampling within the TPOS—sometimes surveying shifting frontal regions of a developing system like El Niño, and, sometimes, like here, seren-dipitously leveraging off of intensive process studies taking place in a key region of the climate system,” said Meghan Cronin, an oceanographer with NOAA’s Pacific Marine Environmental Laboratory and an affiliate professor at the University of Washington School of Oceanography.

The meeting of the Saildrones, Wirewalkers, and Seaglider marked a rare moment in which multiple autonomous systems—each operating at different depths, speeds, and scales—converged to observe the same dynamic environment. The Saildrones skimmed across the surface, collecting atmospheric and upper- ocean measurements. The Wirewalkers traced con-tinuous vertical profiles, using the power of passing waves to “walk” profilers up and down 2,500 feet of wire beneath the surface. The Seaglider, diving in long, sweeping arcs that reached depths of 3,000 feet, monitored deeper physical and biogeochemical signals.

This synchronized survey was designed to capture features of the equatorial Pacific that influence weather patterns across the globe, from droughts in Australia to winter storms in North America. Under-standing these processes hinges on both intensive observations and ongoing monitoring. Coordination across three autonomous systems doesn’t just triple the amount of data—it provides unique insights that couldn’t be obtained by any individual platform.

Historically, intensive field campaigns depended on research cruises and moored buoys. Increasingly, fleets of autonomous platforms like Saildrones, Wirewalkers, and Seagliders can roam vast distances with minimal human intervention, transmitting near- real time data back to scientists on shore.

“Uncrewed vehicles are not only being integrated into observing systems in remote areas of the ocean, such as the tropical Pacific. The USVs are also, for the first time, making it possible to directly measure extreme conditions that are too dangerous for crewed research vessels,” said CICOES scientist Dongxiao Zhang. He pointed to a separate effort as an example: the research team is using USVs to observe air-sea interactions inside hurricanes—work that could transform understanding of rapid intensification and ultimately lead to better hurricane forecasts.

The weeklong collaboration with the Wirewalkers and Seaglider represented only one part of the broader TPOS mission. Over their months-long journey, the Saildrones provided both high-resolution measurements and broad spatial coverage of key air–sea interactions in the tropical Pacific. With the hope that missions like this can be conducted fre-quently enough to study patterns and variations in the data, the TPOS research team is building a future in which autonomous observing systems work together in a choreographed scientific ballet, one capable of revealing the processes that shape Earth’s climate.

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The TPOS USV missions started in 2017 and more information can be found here: https://www.pmel.noaa.gov/ocs/tpos-usv.

The Wirewalkers were deployed from the R/V Sikuliaq during the NSF-funded MOTIVE (Mixing belOw Tropical Instability waVEs) cruise, led by Chief Scientist Caitlin Whalen of the University of Washington Applied Physics Laboratory.

The Seaglider was deployed by CICOES and UW School of Oceanography graduate student Katie Kohlman from the same R/V Sikuliaq cruise.

The USV Hurricane Observation missions started in 2021; more information can be found here: https://www.pmel.noaa.gov/usv-hurricane/.