🌏General Circulation Models

Understanding the evolution of intervention impact over time would be critical to assessing the viability of a region for carbon removal at scale, the durability of any mCDR intervention, and the extent to which we could operationalize mCDR before having deleterious impact on the local biological or geochemical systems. To answer these questions, we needed models of a different scale and complexity than our trajectory models - like Regional Ocean Modeling Systems (ROMS) or General Circulation Models (GCMs).

Believing that we would eventually need to be capable of working with a variety of GCMs, we got up and running with ECCO-Darwin to start. A global ocean biogeochemistry model, ECCO-Darwin was developed to accommodate regional cutouts, and was built on the widely-recognized MIT-gcm. We thought these features would be helpful as we expanded our intervention modeling to include interactions with biological systems and open ocean nutrient composition.

Although low-resolution versions of ECCO-Darwin could be run on our desktop computers, we had difficulty accessing supercomputing resources (both expertise and physical hardware), which prevented us from dialing up the resolution on our simulations. We pursued partnerships with leading research institutions to help us with ECCO-Darwin model development and mCDR simulation, which added critical domain knowledge and improved the credibility of the studies by enlisting the help of a disinterested third party.

We ran low resolution ECCO-Darwin simulations internally like the one above of a hypothetical deployment removing 0.1Gt of CO2 from the surface ocean in the North Atlantic near Iceland.

Ultimately, we ran a number of simulations aiming to understand the regional differences in ocean carbon uptake due to mixing and air-sea gas exchange. Answering this question was critical for future OAE and macroalgae interventions. The Running Tide Ocean Modeling team collaborated with a number of authors and collaborators to produce a paper with our results which has been submitted and will be linked here once it is published.

Carbon uptake locations in a preliminary simulation using the ECCO-Darwin model

Preliminary results from one model run demonstrating a high degree of CO2 uptake variability between geographic regions. Consistent with other results published in the scientific literature

Intervention designs are unique due to operational constraints, regional sourcing considerations, financing, etc., and it is useful to be able to run simulations representative of intervention-specific scales and rates. Solutions to quantifying open system interventions which evolve over time due to complicated atmospheric and ocean mixing dynamics such as OAE "efficiency maps" have been proposed. These would be extremely useful tools for guiding mCDR practitioners, although intervention-specific modeled results are likely necessary as well. Thus, increasing the accessibility of ROMS and GCMs will be important for mCDR quantification going forward.