Funding for this TPOS-2026 mission is provided by NOAA OMAO UxSOC in support of the project "Uncrewed Surface Vehicles (USV) Integrated within the Tropical Pacific Observing System (TPOS) - TPOS Equatorial Pacific Experiment (TEPEX) Process Studies Embedded Within Backbone Monitoring".

Mission Overview

Mission Dates: Mission Underway

TPOS-2026 (Mission 8)

Mission Blog

Heading to Ground Zero!

August 31, 2026

We now have two pairs of Saildrone, Inc. Uncrewed Surface Vehicles (USV) heading to the Nino 3.4 region of the central equatorial Pacific – Ground Zero of the large El Niño that is in the news. The first pair of USV left Honolulu over a week ago on August 21, 2026, and the second pair is leaving today (August 31, 2026). Each pair of saildrones has an ASVCO₂^® for monitoring air-sea flux of CO₂ and ocean acidification; and all four saildrones have an ADCP to measure upper ocean currents and a full suite of Meteorological and Ocean (METOC) sensors to measure wind stress and air-sea heat flux, and sea surface temperature at multiple depths from the skin of the ocean down to the bottom of the hull at 2 m depth. That 2-meter sensor also measures salinity and dissolved oxygen. In addition, the METOC suite for all but one drone (#1080) has a fluorometer to measure chlorophyll, which is an indicator for phytoplankton in the water.

An El Niño is declared when surface water in the Niño 3.4 box is 0.5°C warmer than the background temperatures for an extended period. These anomalously warm surface waters cause cloud and wind patterns to shift, changing weather around the world. Our 4 drones will head down to the equator to map out exactly where this warm water is located, how sharp the fronts are, how the fronts and warm water affect ocean heating of the atmosphere, how the clouds feedback by affecting how much sunshine enters the ocean, and their impacts on and relation to winds and currents. Our hope is that these measurements will help improve forecasts of this El Niño – by constraining the numerical models with direct measurements, and by cluing us into whether our numerical models are capturing processes that cause the El Niño to grow, evolve, and eventually transition to either a normal or La Niña state. We also will use these observations to help quantify the impact of this El Niño on the ocean’s uptake of carbon dioxide. Normally, the central and eastern equatorial Pacific is a region of carbon dioxide outgassing. But during an El Niño, this is disrupted. By how much? We will see.

Please join us as we journey to the equator for an up close look at this historic El Niño. We are looking forward to observing some really interesting ocean and atmosphere interactions during the next four months. For more information on El Niño and Niño 3.4 see: https://www.noaa.gov/understanding-el-nino and https://www.ncei.noaa.gov/access/monitoring/enso/sst.

TPOS-2026 planned mission route overlaid on satellite image of anomalously warm sea surface temperatures in the Nino 3.4 box. Satellite image from https://www.noaa.gov/understanding-el-nino (Courtesy NOAA).

Blog post by Meghan Cronin