The oceans have a huge storage capacity for carbon, containing more than 50 times the carbon found in the atmosphere and 15-20 times more than found in all land plants and soils. The oceans already take up about one-third of the carbon dioxide released by human activities, and if all the fossil fuel CO2 ever released were distributed in the ocean, the C stocks in the ocean would increase by only one percent. Despite this enormous capacity, the ocean is often overlooked when considering carbon dioxide removal (CDR) approaches. This is likely due to hesitancy on the part of the science community and the public to purposefully alter ocean ecosystems and/or geochemistry to enhance the oceans’ solubility and biological carbon pumps.

This presentation will review several approaches being considered for ocean CDR and what we know and still need to learn.  In all cases, the effectiveness to remove atmospheric CO2, the durability of C sequestration, along with the intended and unintended ecological impacts need to be better known.  For all CDR approaches, there will be social considerations and economic costs that need to be weighed against the cost of doing nothing.  Any ocean CDR approach must also meet the challenges for monitoring, reporting and measurement of its effectiveness and durability.

We will focus our attention on ocean iron fertilization (OIF), one of the better studied ocean CDR approaches that has been conducting open ocean field experiments since the 1990’s. These studies were a success at demonstrating the limits of phytoplankton growth and CO2 uptake due to iron, but they were not designed specifically to estimate durable C sequestration. This talk will introduce what the next steps should be in OIF research, including the need for larger-scale, field-based pilot studies that themselves are unlikely to cause harm to the ocean. The recently formed group- ExOIS (Exploring Ocean Iron Solutions)- will be introduced that is trying to build a consensus around the next steps needed for OIF studies and put forward an ethical path and guidelines that protect the ocean commons.  We need to consider all options to remove CO2 from the atmosphere, as we aggressively shift away from our fossil fuel-based economies and attempt to roll back the resulting effects of our ill-conceived an unintended geoengineering of the planet.