SArOCCO is a multi-institutional ocean carbon – climate science programme in support of effective governance of marine CDR as a public carbon-climate good in South Africa. It aims to minimize the risks and maximize the innovation-led development opportunities for marine CDR in Southern Africa. It is the initial scientific contribution to a potential marine CDR Hub, aiming to coordinate and communicate across the Governance, Finance, Innovation, Science, Education, and Social nexus.
Impact and Outputs
This proposal aims to provide four dimensions of regional and global impacts in both the carbon-climate science and climate mitigation policy development domains for South Africa.
1. It aims to enable South African ocean carbon science and governance policy to strategically assess the feasibility, scalability, and effectiveness of scalable Ocean Alkalinity Enhancement (OAE); Direct CO2 Removal (DOR) and Kelp Afforestation (KA) mCDR interventions in the region
2. It aims to advance the regional ocean carbon–climate science to support this strategic goal. This will be supported by the set-up of a regional high-resolution ocean model verified against high-resolution machine learning reconstruction of coastal CO2 flux variability and trends, as well as a well-resourced mesocosm lab to evaluate the efficiency and risks of interventions..
3. It aims to impact the constraints of the regional carbon sinks, making an order of magnitude reduction on the present uncertainties for the seasonal and mean annual carbon budget for the South African Coastal Ocean System. It aims to integrate with terrestrial constraints to create a regional carbon sink that can enhance the precision of South Africa’s contribution to the Global Coastal Carbon Budget, the Intergovernmental Panel on Climate Change (IPCC), and the National Determined Contributions (NDCs).
4. It aims to impact coastal marine ecosystem management policies by providing a high-confidence multidecadal reconstruction of the variability and trends of ocean acidification, which impacts ecosystem services, biodiversity, and aquaculture in the South African coastal ocean system. These can also be used to develop adaptation policies that minimize the impacts of changing ocean pH on sensitive ecosystems such as corals and non-coral calcifiers as well as industries such as shellfish aquaculture and assess the impacts of scalable mCDR.
Several outputs aim to support these impacts:
1. This project will deliver a high-resolution evaluated model for the South African ocean system that will be a public facility to enable further experiments to be run with confidence. (Key Stakeholder: SU-SCS; SAEON; SOCCO)
2. This project will deliver a model-based strategic assessment of the feasibility and effectiveness of the three most scalable mCDR interventions (OAE, DOR, and Kelp Afforestation). This model will be a public community platform.
3. Quasi-Real Time high resolution coastal ocean carbon products: the multidecadal reconstruction product will be updated continuously from emerging remote sensing observations and annually by the new CO2 observations. Both the science and policy communities can use this product. In the former to assess changes in the trends and variability of the regional carbon cycle and for the latter, to assess the efficacy attribution of mitigation policy interventions at both regional or global scales. (Key Stakeholder: DFFE: Oceans & Coasts)
4. End of Year 3: We will work with the terrestrial carbon community to deliver the first of a five-yearly assessment of the regional land and ocean carbon sinks in support of South Africa’s commitments to the NDCs of the Paris Agreement.
Problem Statement and Science
The confidence and effectiveness of South African and global mitigation measures, such as the NDCs for the Paris Agreement of 2015, depend critically on the degree of uncertainty in the quantified trends and variability of the ocean and land carbon sinks (Canadell et al., 2023; Friedlingstein et al., 2025; Resplandy et al., 2024; Monteiro and Midgley, 2023). These constraints provide quantifiable measures of the state of the carbon cycle and ultimately assess the effectiveness of mitigation from regional and global policy options. These are the most significant carbon-climate global and regional MRV initiatives.
However, the CO2 observations based constraints for marine and ocean systems in the Southern African region are extremely sparse (Monteiro and Midgley, 2023). This sparseness is in sharp contrast to the South African global impact through multidecadal observational-based constraints to the trends and variability of the Southern Ocean (Gregor et al., 2018; Djeutchouang et al., 2022) and global ocean carbon fluxes (Gregor et al.,2019). This is a significant weakness in evaluating the effectiveness of regional carbon sinks and global policy options under increasing and decreasing positive emissions of anthropogenic CO2, as well as in model verification, and particularly in building an effective approach to the rapidly growing need to assess mCDR interventions. In the short to medium term future, this challenge to make mCDR an effective climate mitigation intervention is threefold:
While marine/ocean Carbon Dioxide Removal (mCDR) was initially framed as a part of a set of CDR interventions to address the challenges of hard-to-abate emissions close to net-zero and a predicted small overshoot of 0.1 °C, it is increasingly clear that these assumptions are no longer valid (Canadell et al., 2023; Ramboll et al., 2023; Ampah et al., 2024). Instead, it is increasingly evident that mCDR is now being invoked as necessary to reduce the expected larger CO2 overshoot of the 1.5 °C carbon budget, uncertainties in the non-CO2 contributions to radiative forcing, emerging land and ocean positive feedback, and to support the achievement of net-Zero targets (Lamboll et al., 2022; Schleussner et al., 2024). Notwithstanding the probable excessive optimism about the rapid scalability of mCDR interventions such as OAE and Kelp afforestation, it is doubtful that mCDR could make a significant, sustained contribution (±1 PgCy-1) to support global emissions reductions in a 10-year horizon (Boyd et al., 2022; Ho, 2023; Ampah et al., 2024). Meeting net-Zero by 2050 still relies mainly on the far lower cost emissions reductions (Ho, 2023). However, scalable global mCDR (1 – 3PgC y-1) will still be essential to achieve the net-zero target and subsequently to claw back the overshoot of the 1.5 °C remaining carbon budget beyond net-Zero after 2050. While the scalable OAE and KA mCDR interventions are conceptually simple, their feedback, impacts, and efficiencies at scale are far from well understood (Bach, 2024; Boyd et al., 2024). These are key governance challenges from marine ecosystem management to financial risk associated with the investment required for interventions at scale (Doney et al., 2025 https://oceanpanel.org/publication/marine-carbon-dioxide-removal/).
A potentially significant governance challenge is the short-term acceleration of mCDR deployments for emission offsets that is already happening, driven mainly by the voluntary carbon markets (Nordahl et al., 2024; Oh et al., 2025; https://frontierclimate.com/; https://stripe.com/climate). Although this uses the same atmospheric CO2 removal mechanisms as mCDR, it should be considered with care because, even at scale, it would have a minimal impact on the airborne fraction and radiative forcing, and therefore does not significantly primary climate mitigation objectives (Ho et al., 2023; Canadell et al., 2023). This outcome highlights misconceptions that suggest the apparent feasibility of using mCDR to offset emissions, rather than focusing on its far greater public climate reduction impact and lower cost of emissions reductions to make mCDR effective. Urgency of investment on emissions reductions is increasingly highlighted by growing evidence of weakening of land and oceans sinks – warming is proceeding unabated even though emissions are not increasing at the same rate (Ke et al., 2024; Muller et al, 2025). These are major science and governance policy challenges globally, and not least in South Africa.
SArOCCO takes advantage of this 10-year scaling-up lag to build the necessary skills, capabilities, and science for South Africa to have governance systems that enable it to assess the feasibility and effectiveness of proposed mCDR interventions.
The confidence in model projections that are necessary to evaluate policy options depends critically on low uncertainty levels in ocean observations based reconstructions of pCO2 and CO2 fluxes. All depend on a well-founded, scale-sensitive, and low-uncertainty sustained carbon observing system, along with associated machine learning high-resolution multidecadal reconstructions, which enable the observations to be converted into resources supporting both science and policy (Monteiro and Midgley, 2023). Critically, South Africa does not yet have a sustained coastal carbon observatory, which is essential for models and model projections, as well as for assessing the effectiveness of mCDR policy interventions. South Africa’s sustained coastal carbon – climate observations have long been neglected as part of the long term sustained coastal observations policies with most existing observations unevenly distributed regionally and focused on local marine resource research questions or decadal mean estimates with high degrees of uncertainty (Monteiro and Midgley, 2023).
SArOCCO aims to enable South African science to develop a strategic approach to evaluate the feasibility, efficiency, and effectiveness of scalable mCDR in the South African regional ocean.
We identified the following four priorities.
1. How do the highly energetic dynamics (physics and biogeochemical) of the Southern African coastal ocean (coast to 500km offshore) influence the effectiveness of scalable mCDR interventions?
2. What are the feedback and risks in the South African coastal ecosystems with respect to the possible deployment of two of the most scalable negative emissions interventions: Ocean Alkalinity Enhancement and Kelp Afforestation?
3. What are the critical physical and biogeochemical processes and scales of variability that influence the uncertainties in the multidecadal reconstructed CO2 observations-based products?
4. What is the integrated carbon budget of the South African coupled land – ocean system? Which parts of the integrated South Africa-coupled Land-Ocean system contribute the most to the uncertainty in the mean triennial ocean and land sink budgets?
Work Plan
This proposed research plan will use three inter-connected methodological approaches; in-situ observations (ship, moorings and gliders), machine learning reconstructions (in situ observations and OSSEs) and a high resolution coastal model. The supporting instruments and infrastructure are in place (DFFE – ships and equipment, CSIR – SOCCO – gliders, and SAEON – moorings; High resolution models: SAEON and SOCCO).
WP1: Sustained Optimized Coastal Observations [Thato Mtshali, Siya Hamnca, Mutshutshu Tsanwani, Sarah Nicholson, Tommy Bornman, Pedro Monteiro]
The purpose of this work package is to obtain the sustained scale sensitive observations (ship and gliders) to enable the high resolution multidecadal machine learning reconstructions of the regional CO2 and CO2 flux constraints to be done in WP2.
WP2: High-resolution modelling of the regional coastal carbon system and its processes and variability [Jennifer Veitch, Christian Ethé; Nicolette Chang; Laique Djeutchouang, Ntsikelelo Yalezo, Pedro Monteiro]
The purpose of this work package is to put in place the high resolution (1 – 10km) reanalysis-forced coastal models that will be used for a) run OSSE experiments to optimize observational scales for the data products and b) to run model based MRV experiments that will enable us to explore the efficiency and effectiveness of OAE and KA deployments at different suitable locations on the South African coastal system in WP3.
WP3: Strategic analysis of the effectiveness and feedbacks from mCDR interventions [Pedro Monteiro, Jennifer Veitch, Sarah Nicholson, Siya Hamnca, Ursula Scharler, David Glassom]
These will be a series of well considered simulation experiments that will examine the physical, biogeochemical and ecological sensitivities and effectiveness of 3 (low, medium, high) deployment of two of the most scalable mCDR interventions (OAE, DOR and KA). The design of these experiments will be carried out by a community panel to ensure that the strategic approach is useful to a wide audience of scientists and policy makers.
Principal Investigators: Prof Pedro Monteiro (SCS, Stellenbosch University) and Dr Thato Mtshali (DFFE: Ocean and Coasts)
Lead Investigators: Dr Sarah Nicholson (SOCCO-CSIR); Dr Laique Djeutchouang (SCS-SU-SOCCO); Dr. Siyabulela Hamnca (SOCCO-CSIR); Dr Jenny Veitch (SAEON-Somisana); Mutshutshu Tsanwani (DFFE: Oceans & Coasts); Prof Ursula Scharler (UKZN); Dr David Glassom (UKZN); Dr Tommy Bornman (SAEON-SMCRI);
HCD: 3 PhD and 3 Post Doc
References
Ampah, J., et al., 2025; Scaling carbon removal without delaying emissions reductions., Nature Reviews clean technology., https://doi.org/10.1038/s44359-025-00081-x
Bach, L. T.: The additionality problem of ocean alkalinity enhancement, Biogeosciences, 21, 261–277, https://doi.org/10.5194/bg-21-261-2024
Boyd, P.W., Bach, L.T., Hurd, C.L. et al. Potential negative effects of ocean afforestation on offshore ecosystems. Nat Ecol Evol 6, 675–683 (2022). https://doi.org/10.1038/s41559-022-01722-1
Boyd, P., et al 2024 Limited understanding of basic ocean processes is hindering. Environ. Res. Lett. 19 061002
Canadell et al., 2023; Intergovernmental Panel on Climate Change (IPCC). Chapter 5: Global Carbon and Other Biogeochemical Cycles and Feedbacks. In: Climate Change 2021 – The Physical Science Basis: Working Group I Contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press; 2023:673-816.
Djeutchouang, L. M.,eet al., (2022): The sensitivity of pCO2 reconstructions to sampling scales across a Southern Ocean sub-domain: a semi-idealized ocean sampling simulation approach, Biogeosciences, 19, 4171–4195, https://doi.org/10.5194/bg-19-4171-2022
Doney, S., et al., 2025. Principles for Responsible and Effective Marine Carbon Dioxide Removal Development and Governance. Washington, DC: World Resources Institute. https://oceanpanel.org/publication/marine-carbon-dioxide-removal/
Friedlingstein et al., 2025; Global Carbon Budget 2024, Earth Syst. Sci. Data, 17, 965–1039, https://doi.org/10.5194/essd-17-965-2025.
Ho, D., 2023 Carbon dioxide removal is not a current climate solution — we need to change the narrative. Nature 616, 9 (2023) doi: https://doi.org/10.1038/d41586-023-00953-x
Ke, et al., 2024, Low latency carbon budget analysis reveals a large decline of the land carbon sink in 2023, National Science Review, https://doi.org/10.1093/nsr/nwae367
Gregor, L., Kok, S., and Monteiro, P. M. S.: (2018) Interannual drivers of the seasonal cycle of CO2 in the Southern Ocean, Biogeosciences, 15, 2361–2378, https://doi.org/10.5194/bg-15-2361-2018