SOCONET was originally envisioned as purely reference network, but is currently implemented with broader engagement and aims to serve as a coordinating entity also for operators collecting non-reference surface ocean CO2 measurements . SOCONET supports technical developments and streamlined capacity building which will increase the readiness level in parts of the community not yet capable of making reference-level measurements.
In parallel, the key focus remains on what is referred to as the Tier 1 component, to distinguish it from the larger SOCONET efforts, and describe the best practices required to meet the goals of SOCONET-Tier 1. These best practices should propagate through the relevant oceanographic communities and stakeholders, and elevate the quality and traceability of all surface ocean and marine boundary layer GHG measurements. The development of SOCONET-Tier 1 protocols takes advantage of recommendations regarding instrumental analysis in several established efforts. In particular, procedures described in the SOCAT Quality Control (QC) cookbook and dataset QC flags therein (Gkritzalis et al., 2025).
To this end, a dedicated SOCONET Tier-1 Task Team lead by Rik Wanninkhof, developed a document which describes the first operational steps to implement the reference-quality measurements. The requirements for SOCONET-Tier 1 are to perform high-quality observations with an accuracy of <2 µatm in fCO2w and <0.2 ppm (µmol mol-1) in mole fraction in dry air, xCO2a, and implementation of these measurements in a coordinated framework. This approach and these accuracies are necessary to constrain global annual sea-air CO2 fluxes to 0.2 Pg C (1015 g C) or uncertainties of less than 10% of the current annual global sea-air CO2 flux. The document provides the practical considerations to establish uniform presentation, documentation, and (meta)data delivery. It incorporates ideas and common practices in place by established operators with the goal of providing a unified outward-facing presence of the entities providing high-quality measurements. Therefore, adoption of the steps by established groups is envisioned to be relatively straightforward.
This document is focused on Tier 1 operations, but much of the practices will likely be adapted for non-Tier 1 measurements once experience is gained in incorporating the procedures by the established groups.
Please consult the First steps to implement SOCONET-Tier 1 measurements and data delivery for much more detail.