the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 15 May 2025
Synthesis of data products for ocean carbonate chemistry
Abstract. As the largest active carbon reservoir on Earth, the ocean is a cornerstone of the global carbon cycle, playing a pivotal role in modulating ocean health and regulating climate. Understanding these crucial roles requires access to a broad array of data products documenting the changing chemistry of the global ocean as a vast and interconnected system. This review article provides a comprehensive overview of 60 existing ocean carbonate chemistry data products, encompassing compilations of cruise datasets, derived gap-filled data products, model simulations, and compilations thereof. It is intended to help researchers identify and access data products that best align with their research objectives, thereby advancing our understanding of the ocean's evolving carbonate chemistry.
Competing interests: One of the co-authors, Anton Velo (Instituto de Investigacions Mariñas, IIM – CSIC, Vigo, Spain), is a member of the editorial board of Earth System Science Data.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.- Preprint
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CC1: 'Comment on essd-2025-255', Kunal Chakraborty, 21 May 2025
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The review article ‘Synthesis of Data Products for Ocean Carbonate Chemistry’ offers a thorough and valuable summary of existing ocean carbonate data products, which will greatly benefit the scientific community. However, it overlooks two machine learning-based products that focus on improving surface pCO2 estimates in the Indian Ocean region.
The first is an ML-based climatological pCO2 data product recently developed and published in the journal Scientific Data for the Bay of Bengal region (https://www.nature.com/articles/s41597-024-03236-w) (Joshi et al., 2024). This data product integrates publicly available open-ocean observations with data from the Indian Exclusive Economic Zone. Given that the Bay of Bengal is a unique basin with very limited publicly accessible pCO2 observations, this high-resolution (~0.083°) climatological pCO2 data product represents a significant advancement in our understanding of pCO2 dynamics in the region. Therefore, it may be appropriate to include this product in Section 3.1.3 (i.e., Gridded and derived data products) of the manuscript to enhance its visibility and encourage its use within the scientific community.
The second is a hybrid data product that corrects long-term (1980–2019), high-resolution (~0.083° or 1/12°) modeled surface pCO2 for the Indian Ocean region (as a part of RECCAPv2) using cruise-based observations and an XGB algorithm. This product, available at https://www.nature.com/articles/s41597-025-04914-z (Ghoshal et al., 2025), falls under Section 3.1.6 (i.e., Model-based and hybrid data products and analysis) of this manuscript.
In this study, a machine learning (ML) approach is employed to correct biases in surface pCO2 simulations generated by the INCOIS-BIO-ROMS model (pCO2model) over the period 1980–2019. The ML model is trained using the differences between observed (pCO2obs) and modeled pCO2 to estimate the spatio-temporal deviations (pCO2obs − pCO2model). These interannually and climatologically varying deviations are then added back to the original model output, resulting in two improved data products: pCIBR_Int and pCIBR_Clim.
Evaluation against independent datasets, including moored observations (BOBOA), the gridded SOCAT product, and other ML-based pCO2 products (such as CMEMS-LSCE-FFNN and OceanSODA), demonstrates a significant improvement of approximately 40% ± 3.31% in RMSE compared to the original model. These corrected pCO2 products are expected to improve the accuracy of air–sea CO₂ flux estimates across the Indian Ocean from 1980 to 2019, helping to better identify key source and sink regions and enhancing our understanding of the Indian Ocean’s contribution to the global carbon budget.
Further, in Section 3.1.6 (i.e., Model-based and hybrid data products and analysis), you may also consider including the model-based dataset and analysis of ocean acidification in the Indian Ocean from 1980 to 2019, as presented by Chakraborty et al. (2024). The paper is available at: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2024GB008139. This study provides a comprehensive assessment of ocean acidification trends across the Indian Ocean and its sub-regions, utilizing outputs from a numerical model, an offline biogeochemical (BGC) model, and two machine learning-based products. Overall, the research consolidates the current state of knowledge on Indian Ocean acidification by integrating available field observations, reconstructed datasets, and model simulations.
References:
Joshi, A. P., Ghoshal, P. K., Chakraborty, K., & Sarma, V. V. S. S. (2024). Sea-surface p CO2 maps for the Bay of Bengal based on advanced machine learning algorithms. Scientific Data, 11(1), 384.
Ghoshal, P. K., Joshi, A. P., & Chakraborty, K. (2025). An improved long-term high-resolution surface p CO2 data product for the Indian Ocean using machine learning. Scientific Data, 12(1), 577.
Chakraborty, K., Joshi, A. P., Ghoshal, P. K., Baduru, B., Valsala, V., Sarma, V. V. S. S., Metzl, N., Gehlen, M., Chevallier, F., & Lo Monaco, C. (2024). Indian Ocean acidification and its driving mechanisms over the last four decades (1980–2019). Global Biogeochemical Cycles, 38(9), e2024GB008139. https://doi.org/10.1029/2024GB008139.
Citation: https://doi.org/10.5194/essd-2025-255-CC1 -
AC1: 'Reply on CC1', L.-Q. Jiang, 27 May 2025
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Dear Kunal Chakraborty,
Thank you for your kind words about the article and for highlighting the data products that should be included. We'll be sure to incorporate them in the next version of the paper during the revision process.
Liqing
Citation: https://doi.org/10.5194/essd-2025-255-AC1 -
CC2: 'Reply on AC1', Kunal Chakraborty, 15 Jun 2025
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Dear Dr. Liqing Jiang,
I'm glad to hear that you found the listed data products useful for inclusion in the manuscript. Thank you very much for agreeing to include them during the revision process.
Best regards,
Kunal Chakraborty
Citation: https://doi.org/10.5194/essd-2025-255-CC2
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CC2: 'Reply on AC1', Kunal Chakraborty, 15 Jun 2025
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AC1: 'Reply on CC1', L.-Q. Jiang, 27 May 2025
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RC1: 'Comment on essd-2025-255', Anonymous Referee #1, 21 Jul 2025
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General Comments
The review ‘Synthesis of Data Products for Ocean Carbonate Chemistry’ presents an extensive and thorough summary of multiple oceanic carbonate system data products. This work includes an overview of cruise data compilations, time series data synthesis products, gridded and derived data products, multi-product analyses, and model based data synthesis products for ocean carbonate chemistry. Key information on data availability and access links, with associated references, is reported concisely and clearly. In addition, it is explained that overlaps, such as the use of SOCAT and/or GLODAPv2 in the majority of data products, allows for additional quality control and the test and intercomparison of the different approaches used to generate the respective products. This work is a very useful tool and valuable contribution and will considerably benefit the scientific community in several disciplines. The preprint manuscript is well written with key information regarding each data product reported in a series of tables. I recommend publication following minor revisions, as detailed in the following.Specific Comments
Check for repeat definitions of certain acronyms, e.g. DIC, TA, as the subsequently repeated definitions can be removed to make the text more concise. Make sure to use the acronyms in the remainder of the text, for consistency and instead of writing out in full each time.
Check consistency of certain variables, specifically the saturation states as Ωarg, Ωarag and ΩAr styles are used, for example. Or if the different notations that are used in the manuscript text are due to the specific notation of that variable in the data product, then perhaps retail use of consistent acronyms, if they are the same, e.g. dissolved inorganic carbon (DIC), and re-define variables using a different acronym/notation per dataset, e.g. aragonite saturation state (Ωarag).
Check consistency with defining the pH scale used, e.g. pH on total scale or pH on the total hydrogen ion scale.Technical Corrections
Line 111 is ‘… 1690 to 1730 Gt of Carbon …’ a global average? what is defined as surface ocean (depth)?’
Line 113 regarding ‘…the oceans' buffer capacity…’ add details to further explain this concept on first usage; buffer against?
Line 120 replace ‘… parameters… ‘ with ‘variables’ for correctness and consistency as used on Lines 347, 348, 385 for example; this is the case for the use of this word in other places in the text
Line 129 is there a word missing at the end of the statement ‘… weakened seawater buffer capacity by biologically induced CO2…’?
Line 184 replace ‘… parameters… ‘ with ‘variables’; this is the case for the use of this word in other places in the text
Line 221 acronyms ‘… dissolved inorganic carbon (DIC), total alkalinity (TA)…’ are already defined earlier in the text
Line 243 replace ‘… parameters… ‘ with ‘variables’; this is the case for the use of this word in other places in the text
Line 266 replace ‘… parameters… ‘ with ‘variables’; this is the case for the use of this word in other places in the text
Line 292 replace ‘… parameters… ‘ with ‘variables’; this is the case for the use of this word in other places in the text, which won’t be indicated for each further occurrence beyond page 10 to limit the repetition
Line 349 acronyms ‘… dissolved inorganic carbon (DIC), total alkalinity (TA)…’ are already defined earlier in the text
Line 414 replace ‘…alkalinity…’ with ‘… TA…’, assuming it is total alkalinity or otherwise please specify
Line 488 is the statement ‘… surface-ocean carbonate conditions …’ referring to carbonate ion concentrations or carbonate system variables, please clarify
Line 690-691 check font and type setting
Line 717-718 check all that acronyms previously defined could be used for all variables listen in full
Line 735 has acronym ‘… OA …’ been defined?
Line 841 has ‘ … [H+] …’ been defined/explained in full?Citation: https://doi.org/10.5194/essd-2025-255-RC1
Data sets
Surface Ocean CO2 Atlas Database Version 2024 (SOCATv2024) (NCEI Accession 0293257) Dorothee C. E. Bakker et al. https://doi.org/10.25921/9wpn-th28
Global Ocean Data Analysis Project version 2.2023 (GLODAPv2.2023) (NCEI Accession 0283442) Siv K. Lauvset et al. https://doi.org/10.25921/zyrq-ht66
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