New BG Letter: Composite model-based estimate of the ocean carbon sink from 1959 to 2022

28 March 2025

The ocean is a major natural carbon sink. Despite its importance, estimates of the ocean carbon sink remain uncertain. Here, the author presents a hybrid model estimate of the ocean carbon sink from 1959 to 2022. By combining ocean models in hindcast mode and Earth system models, they keep the strength of each approach and remove the respective weaknesses. This composite model estimate is similar in magnitude to the best estimate of the Global Carbon Budget but 70 % less uncertain.

Co-editor-in-chief's statement: The ocean plays a key role in the global carbon cycle and its carbon sink strength is critical for removing atmospheric carbon dioxide and stabilizing global climate. This oceanic carbon sink strength is difficult to measure and models provide estimates that differ from one another. Terhaar combines multiple modeling approaches using composite model-based averages and fully coupled Earth System Models to take advantages of the benefits of both, and in doing so derives a similar sink strength to existing estimates but with reduced uncertainty.

Contact: Jens Terhaar (jens.terhaar@unibe.ch)