The ocean represents an important component of the carbon cycle and provides a critical service to humanity by absorbing more than a quarter of anthropogenic emissions every year. Our ability to observe the vast and remote Southern Ocean has long been inconsistent with its importance. While Australia has provided global leadership in acquiring ship-board observations, the Southern Ocean remains persistently under-sampled contributing directly to uncertainty in estimates of the ocean carbon sink.

The Constraining Ocean Carbon with Optimized Observing (COCO2) project is focused on acquiring winter season observations of air-sea CO2 flux in the Southern Ocean using Uncrewed Surface Vehicles (USVs). In this presentation, a new international initiative between NOAA PMEL (US), Columbia University (US), CSIR (S. Africa) and CSIRO/AAPP, and in partnership with Saildrone, will be introduced. Beginning in 2026, USVs will be launched from Hobart to circumnavigate the Southern Ocean and acquire the direct measurements required to compute air-sea CO2 fluxes. This novel approach combining state-of-the-art technology and observing system design represents an exciting new direction for Southern Ocean carbon cycle research with potential for expansion beyond the 5-year period initially targeted by the project.