159 / 2024-09-10 13:17:04

The effect of model resolution on air-sea CO2 equilibration timescales

Marine Carbon Dioxide Removal,Ocean modelling,air-sea gas exchange,biogeochemical oceanography,physical oceanography

The efficiency of marine Carbon Dioxide Removal (mCDR) deployments is constrained by local air-sea CO₂ exchange rates and deeper water connectivity. Recent studies have highlighted mCDR efficiency in select locations using coarse-resolution models. However, compared with fine-scale resolution models, coarse-resolution models have limitations in eddy resolving and delicate descriptions of jets and downwelling in complex bathymetry regions, which introduces uncertainties in mCDR efficiency predictions.

In this study, we evaluate the impact of model resolution on mCDR efficiency using the ACCESS-OM2-BGC model suite, which employs varying resolutions while maintaining homogeneous code and atmospheric forcing. Specifically, we analyzed the model's response to mCDR deployment by removing identical initial Dissolved Inorganic Carbon (DIC) across 1°, 0.25°, and 0.1° resolutions at various global locations. This approach simulates the variability in surface ocean connectivity and assesses its influence on mCDR efficiency. We also integrated results from previous coarse-resolution studies for cross-comparison.

The findings indicate that global mCDR efficiency is generally higher in tropical regions, relatively lower in mid-latitudes, and very low in polar regions. Differences between resolutions are minor in tropical regions but more pronounced in mid-latitudes. In polar regions, significant differences occur, accompanied by strong deep-water formation processes. Additionally, inter-model variability tends to exceed inter-resolution variability, particularly in the initial years following deployment.

The findings suggest using higher resolution in higher latitudes for more accurate mCDR efficiency evaluation and note that different models and the associated atmospheric forcing can significantly affect the efficiency predictions of mCDR deployments in the initial years.

This research provides valuable insights into the configurational dependencies of modelling for mCDR evaluation, offering guidance for the design and implementation of mCDR strategies in diverse locations and/or current patterns.