Towards a global assessment of coastal dissolved organic carbon

Toming, K, Kulk, G, Quast, R, Shevchuk, R and Kutser, T 2026 Towards a global assessment of coastal dissolved organic carbon. Remote Sensing of Environment, 339. 115388. 10.1016/j.rse.2026.115388

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Abstract/Summary

Dissolved organic carbon (DOC) plays a crucial role in ecological and biogeochemical processes. Many regional satellite algorithms for DOC in coastal waters have been developed. However, there is currently no global algorithm capable of addressing the variability and complexity of DOC dynamics in coastal waters. We address this gap by developing a global DOC satellite retrieval algorithm for coastal waters by using daily, 4-km resolution data from the European Space Agency (ESA) Ocean Colour Climate Change Initiative (OC-CCI) from 1997 to 2023, combined with sea surface salinity (GLORYS12v1 database) and temperature (ESA SST-CCI, version 3.0 database). For model development, we matched these satellite datasets with in situ DOC concentration data from the CoastDOM v1 database. A pairwise correlation between different variables was used to identify the most relevant predictor variables of coastal DOC concentrations. Several statistical methods, including multiple linear regression (MLR), random forest regression (RF), and extreme gradient boosting (XGBoost), were tested. The best performance was achieved by a RF model using sea surface salinity and temperature, the remote sensing reflectance at 560 nm and total absorption at 412 nm, with cross-validation metrics of R2 = 0.91, RMSE = 0.52 mg C L− 1 , and MAPE = 13.01%, and independent validation on unseen data giving R2 = 0.83, RMSE = 0.64 mg C L− 1 , and MAPE = 23.15%. Although the developed algorithm showed high performance, the relatively coarse resolution of OC-CCI poses challenges, as it may fail to resolve sharp DOC gradients in dynamic coastal waters such as river plumes and estuaries, potentially reducing accuracy in those areas. Still, OC-CCI offers climatequality data for a longer period of time compared to individual ocean-colour sensors. Expanding in situ observations, especially in underrepresented areas, will further enhance model accuracy and applicability. The results help to understand carbon dynamics in coastal ecosystems and offer a robust tool for satellite-based assessments of DOC in coastal waters globally

Item Type:	Publication - Article
Additional Keywords:	Dissolved organic carbon Coastal waters Remote sensing Ocean colour Global carbon cycle Ocean colour climate change initiative European space agency
Divisions:	Plymouth Marine Laboratory > Science Areas > Marine Processes and Observations
Depositing User:	S Hawkins
Date made live:	03 Jul 2026 09:20
Last Modified:	03 Jul 2026 09:20
URI:	https://plymsea.ac.uk/id/eprint/10637

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