of marine CDR (http://oceaniron.org). Owing to concerns surrounding the ethics of marine

CDR, ExOIS is organized around a responsible code of conduct that prioritizes activities

for the collective benefit of our planet with an emphasis on open and transparent

studies that include public engagement (2; see inset pg. 3).

Our goal is to establish open-source conventions for implementing OIF for marine

CDR that can be assessed with appropriate monitoring, reporting, and verification

(MRV) protocols, going beyond just carbon accounting, to assess ecological and other

non-carbon environmental effects (eMRV). As urgent as this is, it will still take 5 to 10

years of intensive work and considerable resources to accomplish this goal.

We present here a “Paths Forward’’ report that stems from a week-long workshop held

at the Moss Landing Marine Laboratories in May 2023 that was attended by international

experts spanning atmospheric, oceanographic, and social sciences as well as legal specialists

(see inside back cover). At the workshop, we reviewed prior OIF studies, distilled

the lessons learned, and proposed several paths forward over the next decade to lay the

foundation for evaluating OIF for marine CDR. Our discussion very quickly resulted in

a recommendation for the need to establish multiple “Ocean Iron Observatories’’ where,

through observations and modeling, we would be able to assess with a high degree of

certainty both the durable removal of atmospheric carbon dioxide—which we term the

“centennial tonne”—and the ecological response of the ocean.

3 PATHS FORWARD FOR EXPLORING OCEAN IRON FERTILIZATION

In a five-year phase I period, we prioritize five major research activities:

1. Next generation field studies

Studies of long-term (durable) carbon storage will need to be longer (year or more) and

larger (>10,000 km2) than past experiments, organized around existing tools and models, but

with greater reliance on autonomous platforms. While prior studies suggested that ocean

systems return to ambient conditions once iron infusion is stopped, this needs to be verified.

We suggest that these next field experiments take place in the NE Pacific to assess the

processes controlling carbon removal efficiencies, as well as the intended and unintended

ecological and geochemical consequences.

2. Regional, global and field study modeling

Incorporation of new observations and model intercomparisons are essential to accurately

represent how iron cycling processes regulate OIF effects on marine ecosystems and carbon

sequestration, to support experimental planning for large-scale MRV, and to guide decision

making on marine CDR choices.

3. New forms of iron and delivery mechanisms

Rigorous testing and comparison of new forms of iron and their potential delivery

mechanisms is needed to optimize phytoplankton growth while minimizing the financial

and carbon costs of OIF. Efficiency gains are expected to generate responses closer to those

of natural OIF events.

4. Monitoring, reporting, and verification

Advances in observational technologies and platforms are needed to support the development,

validation, and maintenance of models required for MRV of large-scale OIF deployment. In

addition to tracking carbon storage and efficiency, prioritizing eMRV will be key to developing

regulated carbon markets.

5. Governance and stakeholder engagement

Attention to social dimensions, governance, and stakeholder perceptions will be essential

from the start, with particular emphasis on expanding the diversity of groups engaged in

marine CDR across the globe. This feedback will be a critical component underlying future

decisions about whether to proceed, or not, with OIF for marine CDR.

Paramount in the plan is the need to move carefully. Our goal is to conduct these five activities in parallel

to inform decisions steering the establishment of ocean iron observatories at multiple locations in phase

II. When completed, this decadal plan will provide a rich knowledge base to guide decisions about if,

when, where, and under what conditions OIF might be responsibly implemented for marine CDR.

The consensus of our workshop and this report is that now is the time for actionable studies to begin.

Quite simply, we suggest that some form of marine CDR will be essential to slow down and reverse the

most severe consequences of our disrupted climate. OIF has the potential to be one of these climate

mitigation strategies. We have the opportunity and obligation to invest in the knowledge necessary to

ensure that we can make scientifically and ethically sound decisions for the future of our planet.