The Alarming Decline in Ocean CO2 Observations

(Image credit: ChatGPT)

„observations not taken today are lost forever.“ (Wunsch et al., 2013)

The Critical Need for CO₂ Measurements

Imagine the ocean as a giant lung, breathing in carbon dioxide (CO₂) and helping to keep our planet cool. It absorbs about 25% of the CO₂ emissions from human activities, playing a crucial role in mitigating the pace of climate change. But what happens when we lose sight of this process? Because this is precisely the reality we are beginning to face. Our ability to monitor and understand how the ocean absorbs CO₂ is under threat. A troubling decline in CO₂ measurements combined with a critical funding shortfall for the Surface Ocean CO₂ Atlas (SOCAT)—a key resource for tracking the ocean’s CO₂ role—means we are at risk of compromising our understanding of this crucial component of the climate system.

SOCAT: The Ocean’s CO₂ Observation Treasure Chest

Figure 1: The value chain that connects oceanographic CO₂ measurements to climate negotiations. (modified after Guidi et al., 2020)

Think of SOCAT as a treasure trove filled with invaluable data collected from every corner of the globe by ships, buoys, autonomous vehicles, and drifters (see Figure 1). Since 1957, scientists and dedicated volunteers have painstakingly assembled this collection, now boasting 38.6 million precise measurements of surface ocean fCO₂ (fugacity of CO₂). Each measurement, accurate to within 5 µatm, is a piece of a complex puzzle that reveals how our oceans absorb and store CO₂. These observations are not just numbers—they are an important cornerstone to the WMO Global Greenhouse Gas Watch (G3W) initiative, are the lifeblood of the Global Carbon Budget, and play a critical role in shaping climate policies and reports by the Intergovernmental Panel on Climate Change (IPCC) (see Figure 1). SOCAT’s data help us understand the ocean’s role in our climate system and guide global efforts to tackle climate change.

Falling Behind: The Crisis of Declining Data Collection and Coverage

Figure 2: (a) Number of monthly, 1° x 1° grid cells with fCO₂ for each year in SOCAT database version 2022 (v2022) to v2024, a measure for the open ocean CO₂ observing effort. (b) The number of months with 1° x 1° gridded surface ocean fCO₂ in 2022 and 2023 in v2024. (c) The number of individual months with 1° x 1° gridded surface ocean fCO₂ between 1970 and 2023. (from: SOCATv2024 release poster)

The latest update, SOCATv2024, paints a grim picture of the state of our ocean CO₂ monitoring efforts. It reveals a decline in data collection to levels reminiscent of a decade ago (see Figure 2a). Vast regions of the ocean remain under-monitored such as the Southern Ocean (see Figure 2b and 2c), leaving large patches of the ocean in the dark. Since 2017, we have seen this downward trend, compromising the accuracy of SOCAT-based estimates of the ocean CO₂ sink but also significant gaps in data coverage, especially south of 20°N. The research by Dong et al. 2024 shows a 65% increase in the uncertainty of SOCAT-based ocean CO₂ flux estimate attributed to the decline in data availability from 2017-2021, reducing the reliability of ocean CO₂ uptake estimates in years and regions with sparse observations.

Figure 3: The number of monthly, 1° x 1° grid cells with fCO₂ per year in SOCATv2022 and the standard deviation in ocean CO₂ uptake from 7 SOCAT-based data products in the Global Carbon Budget 2022. (Dong et al., 2024; https://creativecommons.org/licenses/by/4.0/)

Addressing Funding Shortfalls

The challenges facing SOCAT extend beyond declining data collection. Persistent funding shortfalls threaten the integration, quality control, and accessibility of its data products. Currently dependent on a single regional hub, the future of the ocean CO₂ observing system is at risk.

Urgent Call to Action: Securing SOCAT’s Future

Recognizing the gravity of the situation, over 100 concerned ocean experts and stakeholders have come together to issue the Ostend Declaration, underscoring the critical need for a robust, resilient, and sustainable surface ocean CO₂ observing system. This declaration calls for concerted international and intergovernmental efforts to ensure the continuity and expansion of ocean carbon data collection, which is vital for informing national and intergovernmental policies on climate change and mitigation efforts (see Figure 1).

In light of this crisis, there is an appeal for emergency support to ensure SOCAT’s continued contribution to the Global Carbon Budgets over the next two years. There is an appeal for a sustainable funding model that can secure SOCAT’s future. Whether through national hubs, a subscription-based model, or a combination of both, the goal is clear: to establish a robust, resilient, and sustainable framework for ocean CO₂ observations. The document titled “Case for SOCAT as an Integral Part of the Value Chain Advising UNFCCC on Ocean CO₂ Uptake” elaborates on SOCAT’s critical role within the value chain of CO₂ measurements, emphasizing its importance in advising the UNFCCC on ocean CO₂ uptake (see Figure 1).

Embracing Innovation: Our Tools for Ocean Monitoring

To keep the ocean CO₂ observational network and its synthesis alive, action is required. Innovative observational platforms such as Saildrones, profiling floats (e.g., the SOCCOM project), and sailing yachts offer unparalleled opportunities to collect data, especially in remote areas like the Southern Ocean. We must also continue our efforts in traditional shipboard observations, where ships-of-opportunity and research ships provide highly accurate data, acting as vital nodes in our global monitoring network.

Our oceans are the pulse of our planet, and CO₂ observations are the heartbeat we must listen to. Don’t underestimate the danger of losing these crucial data points. As Wunsch et al. (2013) aptly cautioned, “observations not taken today are lost forever.”

References:

• SOCATv2024 release poster
• Dong, Y., Bakker, D. C. E., & Landschützer, P. (2024). Accuracy of ocean CO₂ uptake estimates at a risk by a reduction in the data collection. Geophysical Research Letters, 51, e2024GL108502. https://doi.org/10.1029/2024GL108502
• Case for SOCAT as an integral part of the value chain advising UNFCCC on ocean CO₂ uptake
• Declaration on Operationalising the Surface Ocean Carbon Value Chain
• Wunsch, C.; Schmitt, R. W., & Baker, D. J. (2013). Climate change as an intergenerational problem. Proceedings of the National Academy of Sciences, 110(12), 4435-4436. https://doi.org/10.1073/pnas.1302536110
• Guidi, L., Fernandez Guerra, A., Canchaya, C., Curry, E., Foglini, F., Irisson, J. O., Malde, K., Marshall, C. T., Obst, M., Ribeiro, R. P., Tjiputra, J., Heymans, S. JJ. (Ed.), Alexander, B. (Ed.), Muñiz Piniella, Á. (Ed.), Kellett, P. (Ed.), & Coopman, J. (Ed.) (2020). Big Data in Marine Science. (Future Science Brief 6 of the European Marine Board). European Marine Board. https://doi.org/10.5281/zenodo.3755793