How Uncertain Are Estimates of Marine Carbon Dioxide Removal? Insights from a Simplified Model

[Geoengineering News]

https://www.researchsquare.com/article/rs-10006849/v1

Authors: Ruth Musgrave

https://doi.org/10.21203/rs.3.rs-10006849/v1

24 June 2026

Abstract

Marine carbon dioxide removal (mCDR) approaches such as Ocean Alkalinity Enhancement (OAE) and Direct Ocean Removal (DOR) are necessarily evaluated using ocean models, yet uncertainties in model predictions remain poorly understood. Here, we use a one-dimensional ocean model to investigate the controls on uncertainty in atmospheric CO2 drawdown in an abiotic system. We show that, within the first few years after deployment, estimates of carbon removal are highly sensitive to mixed-layer physical and biogeochemical properties, while longer-term uncertainties are dominated by vertical mixing, air–sea gas exchange and the depth of the initial deployment. Using a Monte Carlo framework, we demonstrate that uncertainty in carbon drawdown can persist for decades when transport into the ocean interior occurs on timescales comparable to or faster than air–sea equilibration. These results identify a fundamental challenge for regional and global mCDR simulations, where the governing physical processes are often poorly constrained and subject to substantial spatial and temporal biases. Critically, uncertainty in the time evolution of carbon removal leads directly to uncertainty in the timing of net neutrality, with important consequences for monitoring, verification, and carbon crediting frameworks.

Source: ResearchSquare